* Coloquio especial
2023/02/09 | Rosa Amelia González López-Lira, IRyA
Anfitrión: Jesús Toalá La relación entre los cúmulos globulares y los agujeros centrales supermasivos (SMBH) en galaxias espirales: el eslabón con la correlación SMBH - masa estelar totalExploramos la relación entre el número total de cúmulos globulares, $N_{\rm GC}$, y la masa del agujero negro central, $M_\bullet$, en galaxias espirales. Incluyendo dispersión cósmica, log $M_\bullet$ \propto (1.64 +- 0.24) log $N_{\rm GC}$. En galaxias elípticas la correlación es lineal [log $M_\bullet$ \propto (1.02 +- 0.10) log $N_{\rm GC}$] y, por lo tanto, podría deberse a la convergencia estadística a través de fusiones. Por el contrario, este mecanismo no puede explicar la correlación mucho más empinada en espirales. Además, derivamos la masa estelar total, $M_\ast$, a partir de su correlación con $N_{\rm GC}$, y ajustamos la correlación entre $M_\bullet$ y $M_\ast$, tanto para espirales como para elípticas. En el espacio de parámetros $M_\bullet$ versus $M_\ast$, con $M_\ast$ derivado de $N_{\rm GC}$}, $M_\bullet$ \propto (1.48 +- 0.18) log $M_\ast$ para elípticas, y $M_\bullet$ \propto (1.21 +- 0.16) log $M_\ast$ para espirales. La concordancia observada entre elípticas y espirales podría implicar que los agujeros negros y las galaxias coevolucionan a través de la acreción "calmada", la retroalimentación por AGNs y otros procesos seculares. |
2023/02/16 | Benne Holwerda, University of Louisville
Anfitrión: Sundar Srinivasan What can the Occult Do for You? Using overlapping galaxies to probe dust properties in galaxiesInterstellar dust is still a dominant uncertainty in Astronomy, limiting precision in e.g., cosmological distance estimates and models of how light is re-processed within a galaxy. When a foreground galaxy serendipitously overlaps a more distant one, the latter backlights the dusty structures in the nearer foreground galaxy. Such an overlapping or occulting galaxy pair can be used to measure the distribution of dust in the closest galaxy with great accuracy. The STARSMOG program uses Hubble to map the distribution of dust in foreground galaxies in fine (<100 pc) detail. Integral Field Unit (IFU) observations will map the effective extinction curve, disentangling the role of fine-scale geometry and grain composition on the path of light through a galaxy. The overlapping galaxy technique promises to deliver a clear understanding of the dust in galaxies: geometry, a probability function of dimming as a function of galaxy mass and radius, and its dependence on wavelength. |
*2023/02/17 | Edgar Santamaría, UdG
Anfitrión: Jesús Toalá Expansion de novas y su difusión en el MIELas observaciones espectroscópicas de remanentes de nova tienen el potencial de determinar sus propiedades básicas y revelar detalles de su estructura, pero hasta ahora se han realizado muy pocos estudios de este tipo. En este trabajo presentamos un análisis sobre la dinámica del material eyectado de novas clásicas y su difusión en el medio interestelar, así como modelos espacio-cinemáticos derivados de una serie de imágenes ópticas y observaciones espectroscópicas de rendija larga y de campo integral de alta dispersión, los cuales permiten revelar por primera vez una visión más real y completa de la morfología de los remanentes nebulares de un evento de nova. |
2023/02/23 | Vianey Camacho, IRyA
Anfitrión: Enrique Vázquez Energía cinética y gravitacional de sistemas hub-filamento durante la fragmentación gravitacional de nubes molecularesRealizamos un estudio del balance de energías gravitacional (Eg), cinética (Ek) y magnética (Em) de grumos y núcleos densos en un sistema hub-filamento en una simulación numérica de la formación y evolución de nubes en colapso gravitacional jerárquico (GHC) y comparamos con una muestra observacional de núcleos densos. Investigamos el escalamiento de Ek y Em con |Eg|, y estudiamos el parámetro virial $\alpha$ y el cociente de Larson $L=v/R^0.5$ correspondientes. Nuestros resultados muestran que los parámetros $\alpha$ y $L$ magnéticos exhiben relaciones similares a su contraparte cinética, aunque el cociente Em/Ek disminuye a medida que |Eg| aumenta. Los objetos más grandes tienden a estar ligados gravitacionalmente, mientras que sus subestructuras internas tienden a parecer desligadas. El parámetro virial, tanto cinético como magnético, exhibe una gran dispersión a bajas masas $M$, al igual que $L$ a bajas densidades columnares $\Simga$. Esta dispersión se reduce fuertemente en las gráficas de Ek y Em contra |Eg|, lo que sugiere que el balance energético en las estructuras es principalmente controlado por Eg de la cual derivan sus energías cinética y magnética. A grandes masas/densidades columnares, las estructuras tienden a ser moderadamente subviriales de acuerdo con las observaciones. En las gráficas de $\alpha-M$ y $L-\Sigma$, los datos observacionales se superponen o continuan la tendencia de los datos numericos, lo que sugiere que el escenario GHC es consistente con las observaciones. |
*2023/03/01 | Shmuel Bialy, Center for Astrophysics
Anfitrión: Enrique Vázquez How do stars shape interstellar gas? UV radiation -supernova -cosmic raysStars form in interstellar clouds through gravitational collapse. Once the stars form, they begin injecting energy back into the interstellar medium, which regulates the next-generation star-formation process. In this talk, I will review key aspects of this feedback process, focusing on the interaction of FUV radiation supernovae, and cosmic rays, with interstellar clouds. The FUV radiation emitted by massive O/B stars is responsible for gas heating and dissociation of molecules in the global ISM (e.g., H2, CO), and may provide a self-regulation mechanism for star-formation. I will present a new analytic model that predicts the FUV radiation field intensity in different galaxies and interstellar environments with varying metallicity, gas density, star formation rate, and galactic disk size. Once these massive stars finish exhausting their fuel, they "go supernova". The supernovae are also a form of feedback, that can both destroy molecular clouds, but also facilitate gas condensation and cloud formation. I will discuss our recent discovery of the "Per-Tau Shell", a gigantic 3D shell of gas and dust in the solar vicinity, that is actively forming new stars. Per-Tau is the first 3D observational evidence for the constructive aspect of supernovae feedback, where supernovae promote cloud condensation and trigger the formation of a new generation of stars. |
2023/03/02 | Bolivia Cuevas Otahola, IRyA
Anfitrión: Jesús Toalá ¿Qué nos dicen los super cúmulos estelares?Además de los cúmulos globulares y los cúmulos abiertos, existe una clasificación de cúmulos con características similares a las de los cúmulos globulares, los llamados super cúmulos estelares (SSCs). En esta charla, resumimos tres resultados principales respecto a las SSCs: (i) En primer lugar, presentamos la herramienta de ajuste nProFit, enfocada en ajustar modelos dinámicos a cúmulos estelares para obtener parámetros dinámicamente relevantes, como masas, densidades, radio del core, radio a media luz y dispersión de velocidades. Para llevar a cabo un estudio robusto de los SSCs, usamos nProfit para ajustar los perfiles de brillo superficial de la población de cúmulos en el disco de M82, la cual es una galaxia tipo starburst con una población aproximadamente coetánea, que alberga alrededor de 400 SSCs. (ii) A la luz de las masas y los radios obtenidos, abordamos la Función Inicial de Masas de los cúmulos (CIMF) del disco de M82, utilizando el código de evolución dinámica Evolve Me a Cluster of Stars (EMACSS), para reproducir la Función de Masa de los cúmulos observada y sus implicaciones.(iii) Como resultado final, y considerando evidencia indirecta de la existencia de estrellas RR Lyrae (RRLs) de edad intermedia, usamos una muestra de SSCs y cúmulos viejos en las Nubes de Magallanes, y la correlacionamos con Gaia DR3 y datos de OGLE, con el fin de encontrar evidencia directa de la existencia de RRLs de edad intermedia. Presentamos una inferencia bayesiana para calcular las probabilidades de pertenencia de las estrellas obtenidas a partir de la correlación cruzada y mostramos las frecuencias por masa solar inferidas de las RRLs. |
2023/03/09 | Roberto Galván Madrid, IRyA
Anfitrión: Jesús Toalá Resolved Observations and Modelling of the Formation of Massive Stars in ClustersDuring the last decade, radio interferometric observations have reshaped our view of the formation of massive stars in clusters. However, very often the interpretation is limited by the complexity of observations. First, I will present recent projects to quantify the population of star-forming cores and young massive stars in cluster forming clouds, mainly the ALMA-IMF Large Program and complementary projects in the W49 cloud. I will highlight some of the first scientific results of these programs, and describe the first continuum (published) and line (submitted) data releases of ALMA-IMF. For the interpretation of the continuum images, the separation of dust and free-free emission is very important, and I will discuss a few methods to achieve this. Then I will switch to another, yet related project, that consists in modelling the kinematics of the ionized gas in the ultra-compact HII region produced by a system of massive stars with a total mass of up to 200 solar masses. Our best-fit synthetic observations confirm that the ionized gas in the inner r~1500 au is gravitationally bound, and that their motions are a combination of rotation and external radial motions. Finally, I will outline our initial efforts to use these tools to contribute to the science case of the Next Generation Very Large Array in the topic of massive star formation. |
2023/03/16 | Eric Jiménez, IRyA
Anfitrión: Sundar Srinivasan Evolución de estructura de galaxias con formación estelar a 0.5 |
2023/03/23 | Josep Miquel Girart, Instituto de Ciencias del Espacio (España)
Anfitrión: Aina Palau Campos magnéticos permeando núcleos de formación estelar: la visión de ALMALos campos magnéticos permean el material de formación estelar en cada escala espacial, desde escalas de galaxias completas, hasta las escalas de ~100 pc de las nubes moleculares, escalas de ~0.1 pc de los núcleos protoestelares, e incluso las regiones más internas de las envolturas protoestelares (escalas de ~100 au) donde los planetas se forman en discos soportados rotacionalmente alrededor de estrellas jóvenes. En el régimen (sub)milimétrico, estos campos magnéticos se infieren principalmente observando la polarización proveniente de granos de polvo alineados magnéticamente. En esta charla, resumiré los resultados principales obtenidos de observaciones de polarización del polvo en regiones de formación estelar, desde escalas de varios miles de au a varias decenas de au. Primero, describiré las propiedades generales derivadas a partir de la polarización observada con ALMA a estas escalas y discutiré el origen de la señal polarizada en diferentes ambientes. Luego, para los casos en que la polarización del polvo parece trazar el campo magnético, mostraré algunas tendencias generales y propiedades de los campos magnéticos, y su relevancia en el proceso de formación estelar. Finalmente, mostraré algunos ejemplos de regiones seleccionadas observadas con ALMA, que son de interés especial. |
2023/03/30 | Alice Pasetto, IRyA
Anfitrión: Jesús Toalá Mapping the 3D magnetic field configuration of M87The magnetic field configuration of AGN jets, how far from the central engine it maintains its configuration and how it evolves during its journey along the jet, are still a matters of debate. In the talk I will present unprecedented high fidelity radio images of the M87 jet. Jansky Very Large Array (VLA) broadband, full polarization, radio data from 4 to 18 GHz, taken at A configuration, allow the study of the emission of the jet up to kpc scales. The high sensitivity and resolution of our data allow to resolve the jet width. The double-helix morphology of the jet material between $\sim$300 pc and $\sim$1 kpc has been confirmed. A gradient of the polarization degree with a minimum at the projected axis and maxima at the jet edges, and a gradient in the Faraday depth with opposite signs at the jet edges have been detected. The 3D configuration of the magnetic field of the jet M87 is finally mapped. The behavior of the polarization properties along the wide range of frequencies is consistent with internal Faraday depolarization. All these characteristics strongly support the presence of a helical magnetic field in the M87 jet up to 1 kpc from the central black hole although the jet is most likely particle dominated at these large scales. A plausible scenario I will show is that the helical configuration of the magnetic field is maintained to large scales thanks to the presence of Kelvin-Helmholtz instabilities. This work is paving the way for future investigations on this matter which will be easily addressed with the upcoming ngVLA. |
2023/04/13 | Carlos Román, IA-Ensenada
Anfitrión: Jesús Toalá Estudiando Estrellas Jóvenes con SDSS APOGEEEl programa de espectroscopía multiobjeto de alta resolución en el cercano infrarrojo, SDSS APOGEE-2, se diseñó originalmente para estudiar estrellas gigantes rojas en las distintas componentes galácticas. Sin embargo, a modo de ciencia de prueba se otorgaron algunas pocas visitas para estudiar estrellas jóvenes en un par de regiones de formación estelar de la galaxia. Hacia el final de la fase IV del SDSS; se habían observado casi 20 regiones de formación estelar, y se decidió que la población de estrellas recién formadas en la galaxia, fuera uno de los programas núcleo del sondeo Milky Way Mapper en la fase V del SDSS. Hablaremos de cómo se logró compilar un catálogo con parámetros estelares para más de 3600 fuentes en 16 regiones de formación estelar, y del desarrollo de dos metodologías de clasificación espectral: por un lado la red neuronal APOGEE Net 2, y por otro el código TONALLI, desarrollado en el IAUNAM. Hablaremos de porqué no es trivial clasificar fuentes en la etapa de pre-secuencia principal, de porqué Milky Way Mapper puede representar un parteaguas en esta área de estudio, y de cómo el grupo de formación estelar del IA UNAM Ensenada está participando de manera importante en este problema. |
2023/04/20 | Alice Pasetto, IRyA
Anfitrión: Jesús Toalá Mapping the 3D magnetic field configuration of M87The magnetic field configuration of AGN jets, how far from the central engine it maintains its configuration and how it evolves during its journey along the jet, are still a matters of debate. In the talk I will present unprecedented high fidelity radio images of the M87 jet. Jansky Very Large Array (VLA) broadband, full polarization, radio data from 4 to 18 GHz, taken at A configuration, allow the study of the emission of the jet up to kpc scales. The high sensitivity and resolution of our data allow to resolve the jet width. The double-helix morphology of the jet material between $\sim$300 pc and $\sim$1 kpc has been confirmed. A gradient of the polarization degree with a minimum at the projected axis and maxima at the jet edges, and a gradient in the Faraday depth with opposite signs at the jet edges have been detected. The 3D configuration of the magnetic field of the jet M87 is finally mapped. The behavior of the polarization properties along the wide range of frequencies is consistent with internal Faraday depolarization. All these characteristics strongly support the presence of a helical magnetic field in the M87 jet up to 1 kpc from the central black hole although the jet is most likely particle dominated at these large scales. A plausible scenario I will show is that the helical configuration of the magnetic field is maintained to large scales thanks to the presence of Kelvin-Helmholtz instabilities. This work is paving the way for future investigations on this matter which will be easily addressed with the upcoming ngVLA. |
2023/04/27 | Jesús Toalá, IRyA
Anfitrión: Sundar Srinivasan Este no es un AGN: La historia del sistema simbiótico CH CygSymbiotic stars (SySts) are binary systems in which a white dwarf (WD) accretes material from a red giant star. X-ray studies of SySts reveal an apparent variety of processes which would suggest different origins. In this talk I will briefly review our current knowledge of the X-ray properties of SySts (their classification and physical parameters), in particular I will describe the iconic systems R Aqr and CH Cyg. Finally I will present our analysis of SySts using the same tools as those currently used for the X-ray-emitting AGNs. |
2023/05/04 | Pedro Rivera, IRyA
Anfitrión: Ramandeep Gill Modeling the early mass ejection in jet-driven outflowsProtostellar jets are an important agent of star formation feedback, tightly connected with the mass-accretion process. The history of jet formation and mass-ejection provides constraints on the mass accretion history and the nature of the driving source. We aim to characterize the time-variability of the mass-ejection phenomena at work in the Class 0 protostellar phase, in order to better understand the dynamics of the outflowing gas and bring more constraints on the origin of the jet chemical composition and the mass-accretion history towards the intermediate-mass Class 0 protostellar system Cep E. We have used the axisymmetric chemo-hydrodynamical code WALKIMYA-2D to numerically model and reproduce the physical and CO emission properties of the jet-driven outflow from Cep E, which was observed at ∼800 au resolution in the CO J=2→1 line with the IRAM interferometer. Our simulations take into account the observational constraints available on the physical structure of the protostellar envelope to provide constraints on the dynamics of the inner protostellar environment from the study of the outflow/jet propagation away from the launch region. WALKIMYA-2D successfully reproduces the main qualitative and quantitative features of the Cep E outflow and the jet kinematics, naturally accounting for their time variability. Signatures of internal shocks are detected as knots along the jet. In the early times of the ejection process, the young emitted knots interact with the dense circumstellar envelope through high-velocity, dissociative shocks, which strongly decrease the CO gas abundance in the jet. As time proceeds, the knots propagate more smoothly through the envelope and dissociative shocks disappear after ∼1000 yr. The distribution of CO abundance along the jet shows that the latter bears memory of the early dissociative phase in the course of its propagation. Numerical modeling of the Cep E jet-driven outflow and comparison with the CO observations have allowed us to peer into the outflow formation mechanism with unprecedented detail and to retrieve the history of the mass-loss events that have shaped the outflow. |
2023/05/11 | Peter Scicluna, ESO
Anfitrión: Sundar Srinivasan
Accelerating our knowledge of interstellar and circumstellar dust with machine learning using Ampere
Accelerating our knowledge of interstellar and circumstellar dust with machine learning using AmpereThe ubiquity of astrophysical dust makes understanding its physics and chemistry essential, even if only so its effects can be removed from observations to study other physics. Dust is in almost every observation, scattering and absorbing light from stars and galaxies at short wavelengths, and emitting at long wavelengths such that roughly half of all photons have been processed by dust at some point. The optical properties of dust are influenced by the size, shape and mineralogy of the grains, which all impact the shape and strength of the absorption and scattering in both the continuum and in features. The impacts of these different physical parameters are often overlapping, such that there are strong degeneracies between different models - for example, changing the size, shape and composition of grains all alter the shape of the 10 micron silicate feature, and similarly can alter the long-wavelength slope of the dust emissivity. To probe the underlying physics, therefore we must both quantify these degeneracies by understanding the parameter distributions, and include prior knowledge in our inference. Therefore it behoves us to adopt Bayesian approaches. However, the physical models required to interpret observations of dust (e.g. Mie theory, the discrete-dipole approximation or radiative transfer) are notoriously expensive in terms of computation time and may not even have a well-defined likelihood function, making many traditional approaches to Bayesian computation infeasible; for example, to interpret extinction we have to model both the dust (Mie theory) and the star’s emission simultaneously. On the other hand, approximate Bayesian approaches tend to produce poor estimates of parameter distributions. Recent advances combining simulation-based inference (SBI) with machine-learning tools such as Normalising Flows have produced a family of asymptotically-exact approaches with the speed of approximate Bayesian computing, known as Neural Inference, which can be many orders of magnitude faster than MCMC. I will give a brief overview of these approaches, before demonstrating how they can be applied to improve our understanding of dust, using the python package Ampere. They are particularly well-suited to problems involving complex, high-dimensional datasets (such as mid-infrared spectra and images) and models with long computing times. I will present the results of applying neural inference to understand the composition of dust produced by evolved stars and dust in the ISM, before finally discussing how it can be applied to a wider range of observables and environments. |
2023/05/18 | Raúl Maldonado, IRyA
Anfitrión: Sundar Srinivasan Evolución dinámica de sistemas planetarios y su conexión con la contaminación metálica en atmósferas de enanas blancasSe conoce que entre el 25-50% de enanas blancas (EBs) tienen elementos metálicos en sus atmósferas, lo cual es evidencia observacional de sus sistemas planetarios remanentes. El paradigma para explicar la presencia de material localizado a pocos radios solares de la EB involucra a los planetas que han sobrevivido la evolución de su estrella central y han desestabilizado de alguna forma asteroides y planetas, los cuales han sido enviados a órbitas muy cercanas de la EB en donde las fuerzas de marea de la EB pueden destrozarlos y así producir la fenomenología observada. Diversos estudios teóricos han analizado la estabilidad dinámica de sistemas planetarios por medio de simulaciones de N-cuerpos a través de la evolución estelar con el objetivo de entender el origen de la llamada contaminación metálica de EBs. Siguiendo esta misma línea de investigación y persiguiendo el mismo objetivo, en este trabajo he realizado miles de simulaciones de N-cuerpos de sistemas planetarios con más de dos planetas, evolucionando la estrella central desde secuencia principal hasta la fase de EB y construyendo los modelos de los sistemas planetarios tomando como base las arquitecturas de los cientos de sistemas exo-planetarios observados con múltiples planetas. Esta elección de parámetros permite constreñir y al mismo tiempo expandir el espacio de parámetros físico y orbital explorado previamente en otros estudios. Además, para entender el papel que juega la multiplicidad planetaria en la contaminación metálica de EBs, he evolucionado un nuevo conjunto de simulaciones usando un espacio de parámetros controlado de tal forma que la única variable es el número de planetas en el sistema. El resultado principal de este trabajo muestra que mientras más planetas tenga el sistema, mayor es la probabilidad de tener una inestabilidad dinámica (pérdida de planetas, cruce de órbitas o dispersión orbital) en la fase de EB, resaltando que la multiplicidad planetaria juega un papel muy importante en activar inestabilidades dinámicas que pueden contribuir a la contaminación metálica de EBs. Incluso, la fracción de simulaciones dinámicamente inestables con 4, 5 y 6 planetas con arquitecturas basadas en los sistemas exo-planetarios es comparable con la prevalencia observada de EBs contaminadas con metales. Además, las simulaciones con alta multiplicidad planetaria resultaron en un número no despreciable de sistemas inestables en la fase de EB con planetas que son lanzados a órbitas muy cercanas de la EB (algunos cruzando el radio de Roche de la EB). Esto último sugiere un mecanismo natural para originar planetas que orbitan cercanamente a EBs como el planeta joviano WD1856b recientemente descubierto con un periodo orbital de 1.4 días. Adicionalmente, el mayor número de eventos dinámicamente inestables se obtiene durante en el primer Gyr de la fase de enfriamiento de la EB y este número decrece a medida que la EB envejece, donde los sistemas que involucran planetas de baja masa (Mp < 100 Mtierra) son dinámicamente activos en escalas de tiempo de Gyr, mientras que los sistemas con planetas de alta masa (Mp ≥ 100 Mtierra) tienden a ser inestables en escalas de tiempo de Myr. |
2023/05/25 | Jacopo Fritz, IRyA
Anfitrión: Ramandeep Gill Under pressure: galaxies’ lives in clustersLas características físicas de las galaxias, como las propiedades de sus poblaciones estelares, el contenido del medio interestelar y su morfología, evolucionan a lo largo de sus vidas. En estructuras masivas como son los cúmulos de galaxias, estos cambios pasan de forma acelerada, tanto que la población galáctica en los cúmulos es muy diferente a distintas épocas cósmicas. En general, las galaxias que se encuentran en cúmulos en el universo local, tienen morfologías de tipo temprano y la mayoría de las de tipo tardío son rojas y se encuentran sin formación estelar. Hay varios mecanismos que se han propuesto para explicar estas diferencias con respecto a la población de galaxias “aisladas”, tanto en la morfología como en las poblaciones estelares, y la mayoría de ellos involucran la capacidad de los cúmulos de remover el medio interestelar de las galaxias que caen hacia ellos. En esta plática voy a examinar los efectos de la presión hidrodinámica, uno de los mecanismos mas efectivos responsable por estos cambios, evidenciando efectos positivos con respecto a la formación estelar y un posible papel con respecto a las transformaciones morfológicas. |
*2023/05/30 | Donaji Esparza, IAC/La Laguna
Anfitrión: Omaira González New spectral decomposition method for QSOs using IFU data.Quasi-stellar objects (QSO) are very luminous active galactic nuclei (AGN), which have been explored broadly to understand the connection between AGN and the host galaxy. However, despite the last decade's efforts, several questions regarding this connection remain unanswered. This is mainly because their study requires a robust deblending of the AGN and host galaxy light.Integral Field Spectroscopic (IFS) can resolve both the integrated and spatially resolved spectroscopic properties of galaxies. Several techniques have been developed for this purpose; however, their algorithms are complex and require several steps. In this talk, I will present a novel, straightforward technique for removing the AGN and revealing the host galaxy's 3D information. This technique will be used for the scientific preparation of the exploitation of the High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (HARMONI), which is the first light instrument of the Extremely Large Telescope (ELT). Consequentially, I will also introduce the main features of this instrument. |
2023/06/01 | Yilen Gómez Maqueo Chew, IA-UNAM
Anfitrión: Carlos Carrasco Propiedades fundamentales de las estrellas y sus sistemas planetarios extrasolares desde el IA-UNAMPresentaré el trabajo de investigación que he realizado en los últimos años en el Instituto de Astronomía que tiene como fin el entender la formación y evolución de las estrellas y sus sistemas planetarios. Parte de este trabajo lo realizo con el telescopio SAINT-EX, un telescopio de 1m de diámetro que se encuentra en el Observatorio Astronómico Nacional de San Pedro Mártir en Baja California. También llevo a cabo la caracterización de las propiedades fundamentales de las estrellas en sistemas binarios eclipsantes, y las de los exoplanetas en sistemas transitantes, como aquellos confirmados con datos de SAINT-EX. |
2023/06/08 | Ph.D. seminars, IRyA
Anfitrión: Gilberto Gómez |
*2023/06/12 | Ue Li, ASIAA
Anfitrión: Susana Lizano Holographic pulsar maps of the ISM: evidence for magnetic domains boundaries?Plasma structures as mapped through plasma lensing have posed an enigmatic challenge since the extreme scattering events in the 80’s. Here we present new insights into the ISM structure through new developments in pulsar scintillation VLBI, pointing to aligned magnetic domain boundaries as a natural mechanism. I will discuss implications and applications. |
*2023/06/13 | Thavisha Dharmawardena, Flatiron Institute
Anfitrión: Sundar Srinivasan A multi-scale multi-resolution view of the 3D structure of the Milky Way and its molecular cloudsThe detailed 3D distributions of dust density and extinction in the Milky Way have long been sought after. However, such 3D reconstruction from sparse data is non-trivial, but is essential to understanding the properties of star-formation, large-scale dynamics and structure of our Galaxy. In this work I will introduce our new fast and scalable algorithm for 3D dust modeling. Using advanced ML methods such as sparse Gaussian Processes and Variational Inference, our algorithm maps Star Formation Regions (SFRs) with millions of input sources in parsec scales within an hour on a single GPU. Our approach allows us to identify large-scale structures in the Milky Way while simultaneously peering into individual molecular clouds, providing insights into multi-scale processes such as fragmentation in molecular clouds. In Dharmawardena et al., (2022 a, b), we model the 3D dust density distribution of 15 SFRs, exploiting distances and extinctions derived from Gaia DR2 and IR data (from Fouesneau et al., 2022). From these maps, we extract 3D boundaries, volumes, precise dust masses (12% statistical uncertainty) and filling factors to study fragmentation within our regions. We recover a wider range of substructures such as new interconnecting and free standing filaments and star-formation feedback and supernovae cavities. In Dharmawardena et al., subm., we present a first look at our new 3D dust density maps of the Milky Way out to 2 kpc from the sun simultaneously showing both large scale structure at 100s of pc scale and smaller scale structure at 10s of pc. The maps’ comparison to the YSO and evolved star samples will shed light on stellar processes taking place in the Milky Way in 3D. |
2023/06/15 | Eric Jiménez y Diana García, IRyA
Anfitrión: Eric Jiménez y Diana García |
2023/06/22 | Auditorium unavailable,
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2023/06/29 | Auditorium unavailable,
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2023/07/27 | Auditorium unavailable,
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2023/08/03 | Auditorium unavailable,
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2023/08/10 | Auditorium unavailable, T.B.D.
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2023/08/17 | Alessia Moretti, INAF/Padova
Anfitrión: Jacopo Fritz Ram pressure stripping at work in intermediate redshift clusters: the case of A2744 and A370Ram pressure stripping has been proven to be effective in shaping galaxy properties in dense environments at low redshift. MUSE IFU data are available for a sample of more distant (z∼0.3-0.5) clusters, with mosaics covering the inner cluster regions. I will present the results of our search of ram-pressure stripped galaxies in this sample. In particular I will describe how we discovered and characterised 13 ram-pressure-stripped galaxies in the central regions of A2744 and A370 (z∼0.3-0.4), using the MUSE spectrograph. As in their low-redshift counterpart, emission-line properties as well as stellar features have been analyzed to infer the presence of this gas-only stripping mechanism, that produces spectacular ionized gas tails departing from the main galaxy body. Our analysis has revealed that in the inner regions of these two clusters the vast majority of blue star-forming cluster members are predominantly ram-pressure stripped, suggesting that this mechanism was even more effective at intermediate redshift than in today’s universe. |
2023/08/24 | Bert Vander Meulen, Ghent University
Anfitrión: Omaira González X-ray radiative transfer in complex AGN media with SKIRTModels of active galactic nuclei (AGN) suggest that their circumnuclear media are complex with clumps and filaments, while recent observations hint towards polar extended structures of gas and dust, as opposed to the classical torus paradigm. The X-ray band could form an interesting observational window to study these circumnuclear media in great detail. To this goal, we have extended the 3D radiative transfer code SKIRT with the X-ray processes that govern the X-ray spectra of obscured AGN, to study the structure of AGN circumnuclear media based on their reflected X-ray emission. This includes Compton scattering on free electrons, photo-absorption and fluorescence by cold atomic gas, scattering on bound electrons, and extinction by dust. To verify our X-ray implementation, we performed the first dedicated benchmark of X-ray torus models, comparing five X-ray radiative transfer codes. The most recent version of SKIRT covers the X-ray to millimetre wavelength range self-consistently, has all features of the established SKIRT framework, is publicly available, and is fully optimised to operate in arbitrary 3D geometries. We illustrate the 3D nature of the SKIRT code by producing synthetic X-ray images and spectra of clumpy torus models, and demonstrate how SKIRT could be used to make predictions for microcalorimeter observations with XRISM. |
*2023/08/29 | Alejandro Lopez Vazquez, ASIAA
Anfitrión: Susana Lizano Star formation processes: accretion streamers and episodic molecular outflowsThe ALMA observations reveal in detail the different structures associated with the star formation processes. In this talk, I will show the formaldehyde emission of the high-star forming region GGD27. I will focus on the emission and modeling of the accretion streamers associated with the disk of the GGD27-MM1. Also, I will present the ALMA Band 7 observations of the CO molecular line emission of the class 0 protostellar system HH 212. The molecular outflow has a complex structure where we find episodic knots launching from the inner part of the accretion disk, as well as, we observe different CO bow shocks entrained by the SiO jet, and we detect the rotating molecular outflow. Finally, I will present ALMA Band 6 observations of the CO molecular line emission of the class II protostellar system HH 30. The molecular outflow presents an internal cavity, as well as multiple outflowing shell structures. We distinguish three different shells with constant expansion and possible rotation signatures. We find that the shells can be explained by magnetocentrifugal disk winds. The multiple shell structure may be the result of episodic ejections of the material from the accretion disk associated with three different epochs. |
2023/08/31 | Mordecai-Mark Mac Low, AMNH
Anfitrión: Enrique Vasquez Dynamical Collapse of Molecular CloudsThe association of molecular emission with dark clouds and star formation now dates back over fifty years. For nearly that long it has been debated whether these clouds are long-lived, quasi-static objects, or short-lived, rapidly evolving ones. Recently, it has become clear that, though they are rapidly evolving, with dynamics controlled by internal gravitational collapse, they are not as short-lived as one might expect because they are continually accreting new mass from their environment. I present evidence for their rapid evolution drawn from clouds self-consistently formed within kiloparsec scale numerical models of magnetized turbulence in a stratified medium driven by supernovae, as well as from full galaxy models using gas dynamics. The evidence includes comparisons to observations of the angle between field direction and density gradients. I support the argument with an analytic calculation showing that clouds likely accumulate due to gravitational instability rather than shock wave sweeping. Finally, I show preliminary results from models of cloud destruction by feedback from newly forming star clusters, emphasizing the difficulty of disrupting the most massive clouds. |
2023/09/07 | Enrique Vasquez, IRyA
Anfitrión: Ramandeep Gill The roles of cooling, the magnetic field, turbulence and gravity in atomic and molecular cloud formationI will discuss the interplay between the various physical processes intervening in numerical simulations of the formation of cold atomic and molecular clouds. Clouds form by external compressions, that may be of (non-self) gravitational or inertial origin. As clouds accumulate mass and increase their column density, three important transitions occur at N ~ 10^21 cm^-2: 1) The clouds begin to become molecular. 2) The clouds become magnetically supercritical. 3) The clouds become gravitationally bound. Thus, compressions naturally explain the observed B-n correlation, and, at typical WNM velocities and field strengths, imply that the flow is moderately supersonic and super-Alfvenic. This produces shocks followed by a thermal condensation front. The flow becomes trans-Alfvenic behind the shock, and sub-Alfvenic in the condensed layer. The magnetic field is bent by the shock and the bending is amplified in the post-shock gas, rendering the field nearly parallel to the dense layer. Induced shear forms filaments, nearly parallel to the field. Gravitational instability in the dense layer then drags the field and forms filaments, causing the field to be perpendicular to molecular filaments. |
2023/09/14 | René Ortega, IRyA
Anfitrión: Ramandeep Gill 3-in-1: on an outreach model, experiences on the social construction of ignorance, and tips to give more effective outreach talks.In this three-part talk, I'll present the outreach model we've been following at IRyA when dealing with hands-on activities directed to school groups, and then I'll comment on experiences when media has altered our intented message, resulting in the social construction, either unintentional or deliberate, of ignorance. In the third part, I'll give a series of suggestions to give more effective outreach talks, considering is the most common outreach action performed by IRyA's academic and student communities. As an epilogue, I'll make a brief summary of the outreach and SciComm actions taken by our team at IRyA. |
2023/09/21 | Anibal Sierra, Universidad de Chile
Anfitrión: Susana Lizano Revealing dust and gas structures in protoplanetary disksSolids and gas are the main components of protoplanetary disks. The dust and gas spatial distribution give us valuable information about the different physical properties taking place in disks, where planet formation is expected. In this talk, I will present results from two projects where dust and gas ALMA observations were used to study physical properties such as dust traps or gas kinematics, and where we found dust/gas observation signatures from forming planets candidates.The first project studies the distribution of solids around six transitional disks (CQTau, DMTau, LkCa15, RXJ1615, SR24S, and UXTau), where ALMA and VLA continuum emission visibilities were analyzed, and where we look for observational signatures that can help us to explain the origin of the large cavities observed in these disks. The second project reveals the distribution of solids and gas around a peculiar disk, which is part of the ALMA Large Program AGE PRO: “ALMA survey of Gas Evolution in PROtoplanetary disks”, and where we found observational gas and dust signatures of two planet candidates. |
2023/09/28 | Auditorium unavailable,
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2023/10/05 | Nadia Murillo, IA-UNAM
Anfitrión: Alice Pasetto The factors that influence protostellar multiplicity in PerseusStellar multiplicity is common at all evolutionary stages and mass ranges. Multiple stellar systems produce a myriad of phenomena, such as complex planetary nebulae, cataclysmic variables, type Ia supernovae, and inspirialing binary systems that generate gravitational waves. Observations of star forming regions reveal that a significant fraction of stars form in multiple protostellar systems. Fragmentation of the natal cloud core or protostellar disk are generally agreed to be the main formation mechanisms of these systems. However, the factors that determine the degree of multiplicity and system structure have not been observationally constrained. To do so, physical conditions (e.g., temperature, density, mass, and kinematics) around protostellar sources need to be measured and compared with system properties (location in the star forming region, multiplicity, luminosity, outflows, and chemical inventory). In order to gain observational insight into the molecular gas environment around protostellar systems, a survey of the Perseus Molecular cloud is carried out. An observing campaign with the Nobeyama 45m Radio Observatory (>5000 AU scales), APEX (5000 to 8000 AU), and ALMA/ACA (> 3000 AU) targetted molecular species that trace cold and warm gas from molecular cloud scales down to inner envelope scales. The range of molecular species covered provide several independent measurements of temperature, molecular hydrogen density, column densities, gas masses, and kinematics at different scales. Dust continuum, polarization data and chemical inventories at scales of a few 100 AU from previous surveys compliment the Perseus molecular gas survey, providing an almost complete view of star formation in the region, and allowing the factors that influence multiple star formation to be identified. In this presentation I will provide an overview of the available data, current results, and future projects. |
2023/10/12 | Auditorium unavailable,
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*2023/10/17 | Javier Ballesteros, IRyA
Anfitrión: Enrique Vázquez ¿Gravedad o turbulencia? La relación Kennicutt-SchmidtEn esta charla daré una visión general de la gran variedad de relaciones Kennicutt-Schmidt reportadas en la literatura, tanto galácticas como extragalácticas, y luego, a partir de la definición pura de la tasa de formación estelar y del álgebra simple, derivaré lo que llamamos "ecuación fundamental de la formación estelar", SFR = \eff Mgas/\tau_ff (donde SFR es la tasa de formación de estrellas, \eff la eficiencia por tiempo de caída libre, Mgas la masa en gas y tau_ff el tiempo de caída libre). Mostraré que si \eff es constante, la masa M_gas debe estar colapsando, y luego, con estas ecuaciones básicas, mostraré que la amplia variedad de correlaciones reportadas en la literatura para nubes moleculares en la Vecindad Solar y para galaxias externas se pueden explicar de una manera autoconsistente, siempre que exista una comprensión de la estructura real de los objetos (galácticos o extragalácticos) bajo estudio. Estos resultados implicarían que la turbulencia poco o nada tiene que ver con la ley de Kennicut-Schmidt. |
2023/10/19 | Sundar Srinivasan, IRyA
Anfitrión: Jesús Toalá SN 2023ixf, or how I learned to stop carboning and love the MCMCThe radiative transfer modeling of circumstellar dust is a many-parameter problem; one must into account various stellar (effective temperature, luminosity, metallicity) and circumstellar (chemistry, geometry) properties, not to mention the properties of the dust itself (size and shape distribution, mineralogy, choice of optical constants). Simplifying assumptions often have to be made for the sake of computational convenience — parameters are kept fixed at “canonical values” based on results from either small or biased samples, or the parameter space is not sufficiently explored to account for the degeneracy in the resulting model spectrum. Both of the above may result in systematic biases in the results. Visual inspection is often used to determine the best fit to the observed spectral energy distribution (SED); worse, no attempt is made to consider models that may be within some tolerance of the supposed best-fit model. As a result, many misconceptions have existed in the literature about inferring the properties of the central star as well as the circumstellar dust content. In this talk, I will focus on SN2023ixf, the brightest SN explosion detected this year so far. A Type II-L supernova that exploded in M101, the Pinwheel Galaxy, the progenitor of this source was identified from archival optical and infrared data and analysed by many authors. I will discuss two papers in which I and my collaborators were involved, focusing on the differences in modeling compared to other works, and will explain how Markov Chain Monte Carlo helped us address the parameter degeneracy, and how this technique might also be easily adaptable to such modeling efforts at the institute. I will end with a rant about the choice of carbon dust for modeling SEDs when there is little evidence or justification for it. I will attempt to provide enough introduction to the basis, so that this talk will be accessible to students as well. |
2023/10/26 | Gibrán Morales, IRyA
Anfitrión: Ramandeep Gill Explorando los destellos de rayos gamma (GRBs) desde una perspectiva de neutrinosCon la temprana detección de neutrinos provenientes de la SN1987A más la reciente detección de ondas gravitacionales, una nueva rama de observación multi-mensajero en la Astronomía ha surgido. Dentro de este contexto, los neutrinos representan un canal de detección valioso para caracterizar múltiples fuentes astrofísicas. Como ejemplo, en este trabajo nos enfocamos en los eventos electromagnéticos mas energéticos que existen en el Universo, los llamados gamma-ray bursts (GRBs), en donde una gran cantidad de neutrinos son creados a través de procesos térmicos. Estos neutrinos obedecen las características del medio cuando se propagan. A lo largo de esta charla mostraremos como se ven modificadas estas propiedades inherentes a los neutrinos dentro de diferentes medios materiales y que información se puede extraer de este tipo de fuentes, ya que muchas veces son opacas inicialmente a los fotones. Adicionalmente presentaré un cálculo estimado del número de neutrinos esperados en detectores actuales y próximos a construir. |
2023/11/09 | Ariel Werle, INAF Padova
Anfitrión: Jacopo Fritz Star-forming regions in the tails of jellyfish galaxiesWe use HST photometry to model the stellar populations of star-forming clumps in the tails of 6 galaxies undergoing extreme ram-pressure. Clumps detected in narrow-band Hα and in the F275W filter of the WFC3 camera are embedded in larger regions (star-forming complexes) detected in the optical (F606W filter). The median mass-weighted ages are ~25 Myrs for Hα clumps and ~35 Myrs for F275W clumps and star-forming complexes. Stellar masses vary from 103.5 to 107 solar masses, with star-forming complexes being the most massive. Hα clumps form a well defined sequence in the stellar mass - SFR plane, with a similar slope to (but systematically above) the main sequence of star-forming galaxies; some F275W clumps and star-forming complexes follow the same relation while others stray away from it as they passively age. As we move further away from the galactic disks, we find clumps to be younger, less massive and less obscured by dust. The difference in the mean age of the stellar populations between the complex and its youngest embedded clump scales with the distance between the clump and the center of the optical emission of the complex, with the most displaced clumps being hosted by the most elongated complexes. This is consistent with a fireball-like morphology, where star-formation proceeds in a small portion of the complex while older stars are left behind producing a linear stellar population gradient. Although the stellar masses of star-forming complexes are consistent with the ones of globular clusters, their stellar mass surface densities are lower by 2 dex, and consistent with the population of low surface brightness dwarf galaxies in clusters. |
2023/11/16 | Violeta Gamez Rosas, Leiden Observatory
Anfitrión: Omaira González The Dust and Molecular Gas in the Torus of NGC 1068"In the context of the AGN unification paradigm, the concept of the “torus” plays a crucial role to discern between Type-1 and Type-2 AGNs. NGC 1068, a well-studied AGN across the electromagnetic spectrum, is a nearby barred galaxy (d=14.4 Mpc) considered the prototypical Seyfert 2. Using MATISSE at the VLTI, we have obtained direct evidence of the dusty torus enshrouding the AGN in NGC 1068. The multi-band capabilities of the instrument and the high spatial resolution that the interferometric technique can achieve have enable us to study in detail the characteristics of the obscuring dust and its spatial distribution. My presentation will delve into these findings and discuss our latest research on the molecular counterpart of the dusty torus. Using ALMA we are able to resolve structures with a comparable angular resolution. The revealed kinematics from the ALMA data suggest an ongoing merger event, potentially contributing to the observed asymmetries in the torus and the water maser disk." |
*2023/11/22 | Omaira González, IRyA
Anfitrión: Jacopo Fritz Las etapas de la evolución del AGN y sus implicaciones para el gas y polvo próximo al núcleoLa evolución de los AGNs está conectada con la evolución de las galaxias a través de la retroalimentación. En las etapas más activas, potentes vientos son lanzados al medio barriendo el material con el que se podrían crear nuevas generaciones de estrellas. Las etapas menos activas del AGN también regulan la evolución de las galaxias a través de potentes chorros relativistas. Es por ello que es importante entender como ocurre la evolución de los AGNs. Nuestro grupo se dedica a encontrar pistas de como ocurre la evolución del gas y polvo en escalas de decenas de parsec entorno al disco de acrecimiento de AGNs a través de la técnica de ajuste espectral. En este platica les contaré nuestros avances en los últimos años y cuales son los pasos que pretendemos dar en el futuro más cercano, utilizando nuevas observaciones del satélite JWST. |
2023/11/23 | María del Pilar González Barreda, Facultad de derecho de la UNAM
La atención del aborto como un asunto de derechos humanosDesde representaciones histórico-jurídicas el aborto ha sido asociado a la realización de un delito. A pesar de que este paradigma estuvo vigente en nuestro país por mucho tiempo, en los últimos años, y debido a los estudios críticos del derecho, particularmente desde perspectivas feministas, así como el avance argumentativo en materia de derechos humanos, la criminalización de esta intervención terapéutica, ha sido considerada como una afectación directa de los derechos sexuales y reproductivos de mujeres, niñas y adolescentes. Desde esta nueva visión, el aborto es considerado como un servicio esencial de salud, que tiene como objetivo procurar el bienestar integral de las personas. Es a partir de este paradigma, que el aborto es defendido como un asunto de derechos humanos, en donde la negativa a la atención, puede tener impacto en la vida y salud de las mujeres, sobre todo para aquellas que viven en contextos de desigualdad complejos. |
2023/12/07 | Ph.D. seminars,
Anfitrión: Gilberto Gómez y Karin Hollenberg |
* Coloquio especial
* Coloquio especial
2021/02/18 | Camilla Pacifici, STScI
Anfitrión: Sundar Srinivasan The ups and downs of galaxiesIn the past years, ground-based and space telescopes have given us inestimable information about the Universe we leave in. We can now study the physical properties of galaxies from the present day, up to 13 billion years ago. Such quantity and quality of data require more and more advanced tools to make the most of the observations. We have thus built a physically motivated library of galaxy spectral energy distributions by combining predictions from cosmological simulation with state-of-the-art models of the stellar and nebular emission and the effect of dust. Our approach allows us to constrain the star formation histories of galaxies and assess how galaxies form, evolve and, after some ups and downs, eventually quench their star formation and evolve passively. I will present the constraints we derive from observations of local and high-redshift galaxies on their evolutionary timescales as a function of stellar mass, and I will also present some work on dust laws in galaxies at redshift one. |
2021/02/25 | Lidia Oskinova, University of Potsdam
Anfitrión: Jesús Toalá Opening new windows for messages from cosmic influencers: massive stars in the era of gravitational wave astronomyStars with masses much higher than our Sun end their short lives in a gravitational collapse, leaving behind neutron stars and black holes. The detections of gravitational waves (GW) brought massive star astrophysics into the new multi-messenger era. A comprehensive understanding of massive star lives and deaths is urgently required to fully unleash the power of multi-messenger astronomy. In this talk I will briefly review our empiric knowledge about massive stars, and highlight the key problems in our current understanding of neutron star and black hole progenitors. I will further discuss the potential of high-mass X-ray binaries to constrain the evolutionary channels leading to GW events. Finally, I will discuss what we are learning about massive star and X-ray binary feedback in different cosmic environments and times. |
2021/03/04 | Bianca Poggianti, INAF
Anfitrión: Jacopo Fritz Multiphase gas, star formation and AGN activity in jellyfish galaxiesI will present results from the GASP (GAs Stripping Phenomena in galaxies) survey whose aim is to study the physical processes that remove gas from galaxies in different environments. I will focus on galaxies in clusters and, in particular, on the ongoing star formation activity and its relation with gas in different phases (ionized, neutral, molecular), both in the galaxy disks and in the tails of stripped gas that are observed at different wavelengths. The most spectacular such cases are known as "jellyfish galaxies". I will show the latest results regarding the star-forming clumps in these tails and I will discuss the star formation history and the quenching induced by ram pressure stripping. Finally, I will show the existing evidence for a possible causal relation between the stripping and the AGN activity. |
2021/03/11 | Annel Tagle, Oficina de la Abogacía General de la UNAM
Anfitrión: Comisión Interna para la Igualdad de Género La política institucional de la UNAM para atender la violencia de géneroLa plática tiene como objetivo dar a conocer el proceso que vivió la Universidad en la adopción y fortalecimiento de su política de género durante los últimos cuatro años. Especialmente se abordarán los principales retos, avances y nuevos desafíos de la política en materia de atención y prevención de la violencia de género dentro de la UNAM. |
2021/03/18 | Daniela Calzetti, UMass Amherst
Anfitrión: Javier Ballesteros Revisiting Attenuation Curves - Then and NowOver the next decade, several facilities will come on-line which will observe the restframe UV/optical emission of galaxies across the entire span of cosmic time, yielding samples of millions of spectral energy distributions (SEDs). Measurements of star formation rates (SFRs), masses, and other physical parameters from those SEDs will enable comparisons with models of galaxy evolution with unprecedented accuracy. However, the derivation of physical parameters from observed SEDs requires removing the effects of dust attenuation. (Sub)mm facilities will not be able to provide sufficient areal coverage and sensitivity to observe those millions of galaxies. This implies that IR-based dust corrections will be difficult to extend to large galaxy samples. For most galaxies, dust attenuation removal from their UV-optical SEDs will require the use of attenuation curves. I will review the current state of our understanding of attenuation curves at low and high redshift, highlight both their strengths and weaknesses, and discuss what steps may be able to move the field forward. |
2021/03/25 | Rene Alberto Ortega Minakata, IRyA-UNAM
One year of outreach during the pandemic: the good, the bad and the uglyA year after the first "work from home" order, I will talk about some of the advantages and difficulties of doing viritual-only outreach and science communication at IRyA during the Covid-19 pandemic. I will comment on outreach projects for the rest of 2021 and I will make a case for the continued use of mixed and virtual-only formats along traditional in-situ events for outreach and science communication once in-person activities resume. |
2021/04/08 | Luis Felipe Rodríguez, IRyA-UNAM
Un rehilete de radio asociado con WR147Las estrellas Wolf-Rayet (WR) son estrellas masivas evolucionadas, caracterizadas por altas luminosidades y vientos estelares rápidos y densos. Hemos detectado un rehilete de radiocontinuo asociado con WR 147, una estrella WR rica en nitrógeno. Estas estructuras se han detectado en el infrarrojo alrededor de un puñado de estrellas WR ricas en carbono de tipo tardío con compañeras masivas, donde se ha formado polvo en la zona donde chocan los dos vientos y producido una columna de gas denso y polvo que es acarreada por el viento WR. A medida que gira el sistema binario, se produce una espiral de Arquímedes. El rehilete resultante contiene información sobre la velocidad del viento, la relación viento-momento y los parámetros orbitales de la binaria. Sin embargo, WR 147 es una estrella WN y la formación de polvo es poco probable, por lo que debe estar funcionando un mecanismo de emisión diferente. Nuestro análisis de los datos sugiere que en este caso la emisión es predominantemente de naturaleza no-térmica (sincrotrón). Es posible que los rehiletes asociados con las estrellas WN sean detectables solo como emisores no-térmicos en longitudes de onda de radio. A partir de las características del rehilete, estimamos un período de 1.7 años para el sistema binario (la estrella WN y una compañera que aún no se ha detectado directamente) que es responsable del rehilete. |
2021/04/15 | Luis Felipe Rodríguez, IRyA-UNAM
Observaciones de hidrógeno atómico en el Amanecer CósmicoDespués de la época de la recombinación a z = 1100, el Universo entró en la llamada Edad Oscura, cuando el hidrógeno era neutro y las observaciones no habían sido posibles hasta hace poco. Se han detectado explosiones de rayos gamma a valores tan altos como z = 11. Pero entre estos dos valores de z no ha habido detecciones. En 2018, la colaboración EDGES reportó la detección de la transición hiperfina del hidrógeno atómico en absorción muy desplazada al rojo, entre z = 15 y 20. La profundidad de la absorción no se puede explicar en términos de cosmología estándar y se han propuesto tres posibles explicaciones: 1) las observaciones son incorrectas, 2) hay un proceso exótico de física y 3) hay un fondo de radio adicional al fondo cósmico conocido. Discutiré posibles fuentes de radio que podrían dar cuenta de la última posibilidad. |
2021/04/22 | Américo González Esparza, Instituto de Geofísica, UNAM
Anfitrión: Vicente Rodríguez Primeras observaciones del nuevo sistema digital de MEXARTEl Radiotelescopio de Centelleo Interplanetario (MEXican Array Radio Telescope MEXART) es un instrumento de tránsito dedicado principalmente a realizar observaciones de centelleo interplanetario (IPS) de fuentes extragalácticas con una frecuencia de operación central de 139.6 MHz. El principal objetivo científico es realizar estudios de propiedades del viento solar y perturbaciones de clima espacial. El sitio está ubicado en Coeneo, Michoacán (19.810 N, -101.690 W) a unos 80 km de Morelia. La antena es un arreglo plano de 4096 dipolos de longitud de onda completa ordenados en una matriz de 64x64. En 2016, el observatorio se convirtió en el sitio principal del Laboratorio Nacional de Clima Espacial (LANCE). El MEXART operaba originalmente con una Matriz de Butler de 16x16, que producía 16 haces latitudinales fijos en diferentes declinaciones. Usando 1/4 de la antena (16 líneas E-W), el MEXART inició operaciones y reportó las primeras mediciones de fuentes IPS, la detección de eventos transitorios de viento solar y observaciones sistemáticas de algunas fuentes IPS para inferir la variación anual de sus índices de centelleo. Sin embargo, el sistema de back-end analógico de MEXART tenía varios problemas. Los 16 haces producidos por la matriz Butler tenían mala directividad (con haces secundarios muy grandes), lo que provocaba pérdidas de ganancia importantes y esto impidió que el instrumento alcanzara la respuesta esperada. Los problemas con las señales de la antena que llegaban al backend, en amplitud y fase, impidieron que el radiotelescopio pudiera detectar la cantidad de fuentes de radio necesarias para monitorear adecuadamente el viento solar entre el Sol y la Tierra. Para resolver este problema, encargamos el diseño y la construcción de un nuevo sistema digital de backend. El nuevo sistema digital resolvió los problemas con el sistema de formación de haces, aumentó el ancho de banda y mejoró la sensibilidad del instrumento. Presentamos en este seminario la primera luz del sistema digital MEXART. Describimos las nuevas capacidades técnicas del instrumento y mostramos algunos resultados preliminares: una estimación de la sensibilidad del instrumento, la observación del tránsito de la Galaxia a 140 MHz y algunas observaciones IPS. |
2021/04/29 | Henrik Beuther, MPIA
Anfitrión: Enrique Vázquez Dynamical star formation from Milky Way cloud scales to hundreds of AUStar formation processes are important over a huge range of physical scales, from large atomic and molecular clouds down to the scales of individual protostellar cores disks around stars. Linking these scales is crucial for a general understanding of star formation and the interstellar medium. I will set into context results from Milky Way cloud scales to individual star-forming regions and dense cores with an emphasis on the dynamical properties of the star formation processes. |
2021/05/06 | Arjun Dey, NOAO
Anfitrión: Rosa Amelia González-Lópezlira Mapping the Universe with 4m TelescopesThe availability of wide-field telescopes equipped with CCD imaging cameras and, more recently, very wide field spectroscopic capabilities, is revolutionizing discovery in astronomy. I will describe the Legacy Surveys project which has created one of the largest, public, deep optical catalogs of the sky. The Legacy Surveys is being used for selecting targets for a cosmology survey with the Dark Energy Spectrospic Instrument (DESI). I will present an overview of the goals, construction, and current status of the DESI project, which aims to create the largest cosmographic map of the universe and investigate its expansion history with unprecedented precision, as well as map the kinematics of many millions of stars in our Galaxy. |
2021/05/13 | Mikako Matsuura, Cardiff University
Anfitrión: Sundar Srinivasan Can supernovae be important source of dust in the interstellar medium of galaxies?In the last decade, Spitzer, Herschel and ALMA have opened up a new era of supernova studies. New findings include detections of dust and molecules from supernovae and supernova remnants. These findings are paving the ways to understand if supernovae can be the major source of dust in galaxies, and to constrain explosive nucleo-synthesis, that is considered to be the main source of elements in galaxies, and explosion mechanisms, which would provide kinetic energy into the interstellar medium of galaxies. I am going to present our latest observations from Herschel, ALMA and SOFIA of supernova 1987A and Galactic supernova remnants. |
2021/05/20 | Luis A. Aguilar, IA/Ensenada
Anfitrión: Susana Lizano GravotermodinámicaLa gravedad es la fuerza que moldea el Universo y las galaxias, cúmulos estelares, estrellas y planetas que contiene. De las fuerzas conocidas, es la única que afecta toda la materia y energía. A pesar de lo sencillo de su forma funcional, su efecto puede ser muy complejo ycontra-intuitivo, pues es de largo alcance y no lineal.Al estudiar sistemas dominados por la gravedad, resulta a veces útil el estudiarlos como sistemas termodinámicos y aplicar conceptos y técnicas de esta disciplina que revelanalgunos de sus comportamientos sorprendentes.Esta no será una charla regular de presentación de resultados originales. Mi objetivo es dar una visión amplia de un área de investigación interesante, que espero Uds. encuentren interesante también. Hablaremos únicamente de gravedad en un regimen no-relativista. |
2021/05/27 | Joel Sanchez-Bermudez, IA-UNAM
Anfitrión: Luis Felipe Rodríguez Interferometric imaging of Young Stellar ObjectsCurrently, it is well-known that low-mass stars are formed via accreting disks. During the last decade an impressive plethora of morphologies have been observed with interferometric observations at radio wavelengths (e.g., ALMA) and, more recently, with infrared coronagraphs (e.g., SPHERE/VLT or GPI). Infrared interferometers have also observed these objects, allowing us to observe the inner rims of the accreting disks and, even, to trace the emitting region of lines like BrG or CO. In this talk, we will review some examples of these discoveries made with the interferometer GRAVITY. |
2021/06/03 | Víctor Mauricio A. Gómez-González, IRyA-UNAM
Anfitrión: Jesús Toalá In search of extragalactic Wolf-Rayet stars: the case of the AntennaeWolf-Rayet (WR) stars are considered descendants of O-type stars. They can be used as indicators of young stellar populations and to study the chemical enrichment of their environments due to their characteristic strong stellar winds enhanced with processed elements. They are also considered as the most suitable candidates for core collapse supernovae (SN) and long-duration soft-gamma ray burst. In this talk I will present the analysis of archival Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) observations of the interacting galaxies NGC 4038/39 (a.k.a. the Antennae) at a distance of 18.1 Mpc, the nearest and youngest pair of colliding galaxies at an early stage of a merger. We report the number, classification and distribution of the WR population in star-forming complexes of the Antennae. We compare our results with stellar population synthesis models. With this work we are increasing the sample of extragalactic WR stars, SNIbc candidates and other interesting post-SN by-products. |
2021/06/17 | José Eduardo Méndez Delgado, IAC Tenerife
Anfitrión: Will Henney Photoionized Herbig-Haro objects in the Orion Nebula. Laboratories to better understand ionized nebulae.We present some results on a project based on high-resolution UVES@VLT spectroscopy and HST imaging of photoionized Herbig-Haro (HH) objects in the Orion Nebula. We study physical conditions, chemical abundances and other properties such as proper motions and the origin of the driving jets. Our study will include at least 9 HH objets, of which we will focus on HH529II, HH529III and HH204 in this talk. Our data allow us to separate the spectrum of the outflows from the main nebular emission, studying each object with an unprecedented detail. The HHs are located at different distances from the main ionization source of the Orion Nebula, with different ionization/physical conditions and flow velocities. In all objects, the electronic density (ne) is substantially higher than in the surrounding Orion Nebula, while the electronic temperature (Te) is maintained under photoionization equilibrium for the most abundant ion stages. In HH204 we observe a Te([OIII]) gradient due to the contribution of [OIII] emission from the cooling layer behind the bow shock, which is also detected in the HST imaging. The ionization degree of the gas in the different HH objects is very different, allowing us to determine the chemical composition of the Orion Nebula under both ionization conditions, avoiding the use of ionization correction factors (ICFs) for many elements. HH204 shows an abundance discrepancy -the difference between abundances derived from recombination and collisionally excited lines- that is actually zero. We find direct evidence of dust destruction in the bow shock in all objects. This increases the gaseous abundances of Fe, Ni and Cr with respect to the Orion Nebula ones. We show that a failure to resolve the different kinematic components -as in a low spectral resolution spectrum- can lead to significant error in the determination of chemical abundances -40% underestimate of O in the case of HH204-, mainly due to incorrect estimation of the electron density. |
2021/06/24 | Varios, IRyA-UNAM
Anfitrión: Omaira & Karin |
2021/08/19 | Enrique Vázquez, IRyA-UNAM
Anfitrión: Sundar Srinivasan The crucial role of accretion in Global Hierarchical Collapse FlowRecent observational and numerical evidence suggests that accretionin the process of star formation occurs not only in the final step, from core to star, but rather at all scales involved. Furthermore, the accretion at each level has a number of unexpected and crucial consequences, which I will discuss in this talk. At the scale of the parent cloud, accretion from its surrounding (possibly atomic) medium counteracts the mass consumption by star formation, maintaining the instantaneously-meauserd star formation efficiency low. Moreover, it causes an increase in the cloud's mass, density, and radius, causing an evolution from a low- to a high-mass star-forming stage. At the filament level, it allows the establishment of a possibly near-stationary regime in which the filaments act as "rivers", funneling material from the cloud to the core scale. At the core scale, the accretion compresses the innermost regions, driving them to collapse even if they are not Jeans unstable. Finally, the gravity-driven mass transfer rate across the core depends on the core's radial density profile. If the density profile is shallower than r^-2, the cores are capable of accumulating mass without transferring it entirely to their central parts, and thus grow in mass and density. Therefore, accretion is one of the main drivers of evolution in star-forming structures. |
2021/08/26 | Tonatiuh Matos, CINVESTAV
Anfitrión: Enrique Vázquez ¿Puede la Mecánica Cuántica explicar el Universo Oscuro?La mecánica cuántica fue desarrollada para explicar el micromundo físico, átomos, moléculas etc. En esta charla mostramos como la ecuación de Schrödinger y los conceptos más simples de la mecánica cuántica han podido explicar los fenómenos más controversiales observados en los halos oscuros, como son la densidad de materia oscura en el centro de las galaxias, el número de galaxias satélite alrededor de galaxias grandes, el comportamiento anómalo de las trayectorias de galaxias satélite, etc. y como conceptos elementales de la mecánica cuántica nos dan una explicación a la expansión acelerada del universo, sin necesidad de energía oscura. |
2021/09/02 | Alberto Carramiñana, INAOE
Anfitrión: Luis Felipe Rodríguez Un poderoso acelerador cósmico en la región de CygnusEn resonancia con las ideas planteadas por Enrico Fermi hace más de sesenta años, predomina la noción de que los rayos cósmicos Galácticos se originan en remanentes de supernova, donde rápidos frentes de choque lograrían acelerar partículas hasta energías en el rango de PeV. El desarrollo de observatorios de partículas de altas energías capaces de muestrear el Plano Galáctico ha permitido poner el paradigma de Fermi a prueba. Y mientras que algunos remanentes de supernova se distinguen entre las fuentes de rayos gamma de TeV, sus espectros no parecen extenderse más allá de algunas pocas decenas de TeV. Por otro lado las observaciones recientes de la región de Cygnus con el observatorio de rayos gamma HAWC de fotones con energías alrededor de 100 TeV muestran que las regiones de formación estelar son capaces de producir rayos cósmicos, pudiendo ser fuentes más relevantes en las energías más altas. |
2021/09/09 | Thomas Nony, IRyA-UNAM
Anfitrión: Roberto Galván
How do stars get their mass? Understanding the origin of the IMF from the mass distribution of cores
How do stars get their mass? Understanding the origin of the IMF from the mass distribution of coresThe origin of stellar masses is one of the most central open issues in astrophysics. In a pilot survey toward W43-MM1, we showed that in the extreme environments of our Galaxy the mass distribution of cores (CMFs) present an excess of high-mass objects compared to the canonical IMF. In this talk, I will introduce the ALMA-IMF Large Program, whose goal is to determine if and how the origin of the Initial Mass Function (IMF) depends on the cloud characteristics. Its first results, obtained from a large sample of cores without significant bias, suggest that CMFs of high-mass proto-clusters generally do not follow the canonical IMF. I will also present our recent detailed studies of the W43-MM2&MM3 region. We propose that top-heavy CMFs are associated with spatially and temporally limited bursts of star formation. In addition, the identification of outflows in CO(2-1) enables us to assess that a very large fraction of the excess high-mass cores are protostellar. This confirms that the high-mass prestellar core phase, if it exists, is evanescent. |
2021/09/23 | Alejandro Raga, ICN-UNAM
Anfitrión: Luis Zapata Los 'dedos de Orion' como objetos autogravitantes de baja masa eyectados en una explosion de supernovaEl sistema de los "dedos de Orion" (eyectados por la fuente infrarroja BN/KL) tiene una elongacion NO-SE, y una asimetria red/blueshift respecto de un eje alineado con la direccion de maxima elongacion del sistema. Esto desafia una interpretacion en terminos de un "flujo bipolar" parcialmmente colimado. Proponemos que este sistema proviene de un disco de objetos de baja masa orbitando en torno de una estrella masiva. Al tener esta estrella una explosion de supernova, los objetos del disco pasan de tener orbitas ligadas a basicamente seguir trayectorias rectas, todas sober el plano del disco. Esta configuracion reproduce en forma llamativa la elongacion y separacion rojo/azul "lado a lado" del sistema de los dedos de Orion. |
2021/09/30 | ,
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2021/10/07 | Karín Menéndez-Delmestre, UFRJ, Brazil
Anfitrión: René Ortega Stellar Structures in Galaxies: Insights from the Local UniverseGalaxies in the local universe are a fossil record of events in the distant universe and present critical constraints for examining models of formation and evolution of galaxies. Based on the Spitzer Survey of Stellar Structure in Galaxies (S4G) database, we study the stellar light that is typically associated with different stellar structures (such as bulge, disk, bar, spiral arms) in an effort to construct a local reference for stellar structure studies. S4G is one of the major legacy surveys of the post-cryogenic campaign of Spitzer and is the largest, deepest and most homogenous mid-IR survey of the nearby Universe to date. Combined with deep optical follow-up, an unprecedented opportunity opens up to complement a stellar mass census with a detailed analysis of the stellar populations in stellar structures. With this in mind we have initiated an observational campaign using the Goodman imager on SOAR to go after S4G galaxies in the southern sky: the Census of Austral Nearby GAlaxies (CANGA). The CANGA survey, covering all griz bands, complements the exquisite work that has been performed by the Sloan Digital Sky Server in the northern hemisphere, but largely surpasses its sensitivity. I will show a number of discoveries we have made within the S4G data set, with a particular focus on the characterization of stellar bars, and give you a preview of the exciting work we are doing with CANGA. |
2021/10/14 | Jesús Toalá, IRyA
Anfitrión: Sundar Srinivasan Shaping born-again planetary nebulaeBorn-again planetary nebulae (PNe) represent very special cases of the evolution of low-mass stars. It is believed that they experienced a very late thermal pulse ejecting highly processed material that is H-deficient but C-rich, rendering their central stars a [Wolf-Rayet]-type. Abundance analysis of the optically-emitting nebulae seem to suggest that these objects were produced by a binary system in a nova-like evolutionary channel. In this talk I will present the analysis of dust emission from the born-again PNe A30 and A78 to demonstrate that once we take into account the C trapped into grains the abundances are consistent with the single stellar evolution scenario. In contrast, I will also present recent ALMA data on one of the youngest objects of this class, A58, which suggest that the shaping mechanisms of the H-deficient nebula is due to the presence of a binary companion. |
2021/10/21 | ,
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*2021/10/26 | Marcelo Barrera, MPIA, Heidelberg
Anfitrión: Carlos Carrasco Observational signatures of the vertical shear instability in planet-forming disk CO kinematicsThe turbulent gas motions in planet-forming disks are crucial for their evolution and are thought to affect the planet formation process significantly. Recent (sub-)millimeter observations show evidence of weak turbulence in the disk’s outer regions. However, the detailed physical mechanism of turbulence in these outer regions remains uncertain. The vertical shear instability (VSI) is a promising candidate mechanism to produce turbulence in the outer parts of the disk. By performing global 3D hydrodynamical simulations of a VSI-unstable disk, and post-processing them producing synthetic ALMA observations, we studied the non-Keplerian kinematic signatures of the VSI that could be observable with the ALMA interferometer. Characterizing these signatures in high-resolution observations can confirm that the VSI operates in the outer regions of protoplanetary disks. During my talk, I will summarize the efforts studying the kinematic signatures of protoplanetary disks produced by the vertical shear instability, and present our predictions for upcoming ALMA observations of CO isotopologues. |
2021/10/28 | Rowan Smith, University of Manchester
Anfitrión: Javier Ballesteros The Cloud Factory: resolving star formation in its galactic contextI present suites of simulations that resolve individual molecular clouds down to ~0.1 pc scales while they are embedded within a larger galaxy simulation. This enables us to study fragmentation and star formation within the resolved clouds in their true galactic context and is a perfect point of comparison to ISM observations in the ALMA era. Our Arepo simulations include a time-dependent chemical model, gas self-gravity, the ISRF and gas self-shielding, magnetic fields, sink particles, and supernova feedback. Using a Milky Way analogue and dwarf galaxy simulations of various metallicities as our base, we turn on these effects step-by-step in a series of simulations to create a laboratory for testing the physics of the ISM and star formation from kpc scales to cold cores. |
2021/11/04 | Neal Evans, UT Austin
Anfitrión: Enrique Vázquez The Central Problem of Star Formation: Why So Slow?The Central Problem of star formation has been clear for over 40 years: simple estimations predict star formation rates more than 100 times what is observed in the Milky Way and other galaxies. Much ingenious theoretical work has been expended to solve this problem, enhancing our understanding of turbulence and feedback in molecular clouds, but the fundamental problem remains. This situation suggests a reconsideration of the basic assumption that underlies the problem: that molecular clouds are bound entities. In the most complete catalog of structures from CO emission maps, most molecular clouds are unbound, ameliorating the problem. Preliminary work combining this information with theoretical models of how the star formation rate depends on the initial virial parameter, along with considerations of how metallicity affects the conversion of CO luminosity into mass, suggests that a solution to the Central Problem may be at hand for the Milky Way. The situation for other galaxies is less clear. |
2021/11/11 | Leonardo Chaves, IRyA
Anfitrión: Gilberto Gomez Stellar orbital dynamics in steady galactic potentialsWe investigate the role of 2D and 3D sticky-chaotic orbits in building boxy bar structures. The models studied originate from snapshots of N-Body simulations. We quantify the degree of chaoticity of the orbits by using the GALI2 index. The candidate orbits that construct these morphologies are located in the outer parts of stability islands. In the case of spiral arms, we use the PERLAS potential that considers massive structures. The spirals are imposed from the ILR to 1.2 times the corotation radius and the parameters of the model emulate Sc galaxies. We compute the 3D periodic orbits of the models in cases when the amplitude of the perturbation varies. These orbits are considered as the skeleton of the spiral arms. The periodic and quasi-periodic orbits support the spirals from the ILR up to the 4:1 resonance. Finally, I present some results of my last work with the GravPot16 model. In this case, we carry out spectral analysis to a set of test particles in this Galactic model. This analysis allows catching the orbits that build the galactic bar. The computed orbits generate a "peanut" structure on the edge-on view. We present the contribution of each orbital family to "peanut" morphology. |
2021/11/18 | ,
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2021/11/25 | Patricia Piñones Vázquez, Centro de Investigación y Estudios de Género
Anfitrión: Comisión Interna para la Igualdad de Género El papel de la academia ante la violencia de género. Estrategias de atención y prevenciónLa conferencia abordará el papel de la comunidad universitaria en lo general, y de la academia en lo particular en el cuestionamiento, modificación y desmontaje de la ceguera de género y la violencia en la universidad. Se desarrollarán elementos que permitan visibilizar la realidad de la UNAM en materia de violencia de género y de violencia contra las mujeres, para que, desde ese lugar se sostenga la necesidad de establecer y consolidar alianzas que construyan una ética comunitaria universitaria que trascienda la confrontación entre sexos, y que deconstruya y redefina normas de género basadas en la dominación. Finalmente se presentarán algunas de las bases para elaborar un plan universitario de acción que promueva la igualdad de género y prevenga la violencia. |
2021/12/02 | Alessia Moretti, INAF
Anfitrión: Jacopo Fritz The molecular gas content of jellyfish galaxiesJellyfish galaxies represent on one side a key tool to understand the galaxy evolution in galaxy clusters, but also they can lead to the understanding of the star formation process in peculiar environments (disturbed disks and stripped gas tails). I will discuss both aspects, focusing in particular on the molecular gas content of GASP jellyfish galaxies, as derived using single dish and interferometric observations at different scales. |
2021/12/09 | Thiago Gonçalves, UFRJ, Brazil
Anfitrión: René Ortega How fast do galaxies die? Probing quenching timescales in the green valleyGalaxies show a clear dichotomy in their properties, with blue spirals being markedly different from red ellipticals. This means galaxies must undergo some physical transformation that prevent them from further forming new stars. In this talk I will discuss a series of results from our group that aim to measure and understand star formation quenching, in particular measuring how fast this must occur. More recently, we have investigated the possible correlation between quenching timescales and other processes, in an attempt to further understand the main drivers of galaxy evolution and transformation between the two populations. |
* Coloquio especial
* Coloquio especial
*2019/01/22 | Rodolfo Montez, Smithsonian Astrophysical Observatory
Anfitrión: Jesus Toalá Out on a Limb: UV Emission from the Asymptotic BranchMass loss dominates stars on the asymptotic giant branch (AGB). Circumstellar shells of enriched material, fed by the mass loss, reprocess stellar light resulting in cool and luminous stars with ample emission longward of optical. As a result, ultraviolet and X-ray emission are not expected from AGB stars, but can originate from binary companions. Taking advantage of the nearly all-sky UV surveying capabilities of the Galaxy Evolution Explorer (GALEX), we have now established that most, if not all, AGB stars do emit in the UV. The origin of the UV emission is unclear; evidence exists for binary origins in some stars and intrinsic origins (photospheric, chromospheric and/or wind shocks) in others. I will review the UV properties of AGB stars and consider the evidence for binary and intrinsic origins. |
*2019/01/23 | Xavier Hernández, IA-UNAM
Anfitrión: Bernardo Cervantes Approaching the dark sector through a bounding curvature criterion.Understanding the observations of dynamical tracers and the trajectories of lensed photons at galactic scales within the context of General Relativity (GR) requires the introduction of a hypothetical dark matter dominant component. The onset of these gravitational anomalies, where the Schwarzschild solution no longer describes observations, closely corresponds to regions where accelerations drop below the characteristic a0 acceleration of MOND, which occur at a well-established mass-dependent radial distance, Rc ∝ (GM/a0)1/2. At cosmological scales, inferred dynamics are also inconsistent with GR and the observed distribution of mass. The current accelerated expansion rate requires the introduction of a hypothetical dark energy dominant component. We here show that for a Schwarzschild metric at galactic scales, the scalar curvature, K, multiplied by (r4/M) at the critical MOND transition radius, r = Rc, has an invariant value of κB = K(r4/M) = 28Ga0/c4. Further, assuming this condition holds for r > Rc, is consistent with the full space-time which under GR corresponds to a dominant isothermal dark matter halo, to within observational precision at galactic level. For an FLRW metric, this same constant bounding curvature condition yields for a spatially flat space-time a cosmic expansion history which agrees with the ΛCDM empirical fit for recent epochs, and which similarly tends asymptotically to a de Sitter solution. Thus, a simple covariant purely geometric condition identifies the low-acceleration regime of observed gravitational anomalies, and can be used to guide the development of extended gravity theories at both galactic and cosmological scales |
*2019/02/06 | Akimasa Kataoka, National Astronomical Observatory of Japan
Investigating the grain growth in a protoplanetary disk by millimeter-wave polarizationThe interpretation of polarization of protoplanetary disks at millimeter wavelengths has been dramatically changing. As a direct extension of polarization in star-forming regions, it has been thought that non-spherical dust grains aligned with magnetic fields would produce the intrinsic polarization in protoplanetary disks as well. However, it is pointed out that dust scattering can also produce polarization. Furthermore, even the direction of the alignment might not be determined by magnetic fields but by radiation fields. Recent ALMA observations have shown that both of the theories are at work in protoplanetary disks. Furthermore, the scattering-induced polarization suggests that grain size is not as large as millimeter but 100 micron, which is a crucial constraint on planet formation. I will review these recent theoretical and observational developments of millimeter-wave polarization in protoplanetary disks and discuss what we can learn from the polarization observations. |
2019/02/07 | Simon Casassus, Universidad de Chile
Warps in transition disksWarps or inclination changes as a function of radius have often been invoked to explain protoplanetary disk observations. Well characterised examples can inform on the origin of such warps, on their role in disk evolution, and may allow for new probes of physical conditions. In transition disks, the separation of the inner and outer disks by a radial gap allows firm constraints on warp geometry. There are now 4 examples of sharply warped transition disks, in which the outer disk is directly exposed to stellar light. In a couple of examples the temperature drop of the gas under the shadowed regions has been detected. Along with a description of the known warped systems, I will present a diagnostic of the outer disk mass based on the cooling timescale of the shadowed gas. |
2019/02/14 | Emilio Tejeda, UMSNH
Tidal breakup of binary stars by supermassive black holesWhen a binary stellar system ventures too close to the supermassive black hole that resides at the center of every galaxy, the intense tidal field due to the latter can split up the binary. In a typical encounter, one of the stars becomes bound to the central black hole while the other is ejected out of the system with a kick velocity of the order of ~ 1000 km/s. In this talk, I will review a proposed model in which this mechanism can naturally account for two peculiar stellar populations in our galaxy: the S-stars at the galactic center and the hypervelocity starts in the galactic halo. Finally, I will present the outcome of recent general relativistic, numerical simulations of binary tidal breakups that systematically explore the vast parameter space that characterizes these encounters. |
2019/02/28 | IRyA AGN group,
AGN torus detectability at submm wavelengthsIn this talk we will show you a study on the detectability of the emission associated with the Active Galactic Nuclei (AGN) dusty structure at sub-mm wavelengths in the era of ALMA. We hack this issue with a theoretical and observational approach considering three typical ALMA frequencies/wavelenghts (100GHz/3000μm, 353GHz/850μm, 666 GHz/450 μm). Theoretically, we use the Clumpy models from Nenkova et al. together with the mid-infrared to X-ray and the radio fundamental plane scaling relations. The latter scaling relation was included since a no negligible contribution at sub-mm wavelength may come from synchrotron emission of the AGN radio jets. The theoretical approach results in the more likely detection of big and dense dusty tori at the highest ALMA frequency (666 GHz/450 μm). Observationally, we use four prototypical AGN: NGC 1052, NGC 1068, NGC 3516, and IZw1, with radio, sub-millimeter, and mid-IR available data. After performing the mid-IR and radio spectrum fitting alone, we combined and extrapolated both fits in order to compare the extrapolation of both torus and jet contributors at sub-mm wavelengths. Our observational results are consistent with our theoretical results. The most promising candidate to detect the torus is the QSO IZw1, although it cannot be resolved due to its large distance. In order to explore the detection of a torus at sub-mm wavelengths, we suggest to perform a multifrequency SED analysis including also radio data. |
*2019/03/05 | Karina Maucó, Universidad de Valparaíso
Anfitrión: Javier Ballesteros Searching for, and analyzing low-mass stars and BD.I will show the on-going analysis of NaCo/VLT data (Ks band polarimetry) of Sz91, a young (~2 Myr), transitional disk around an M1 star located in the Lupus III star-forming region. This object has one of the largest inner cavity observed in a disk around a T Tauri star (~100 au; Canovas, Schreiber et al. 2015) estimated from ALMA. The mm-size grains are concentrated in a narrow (~44 au width), ring-like structure. The micron-sized dust grains probed by our near-IR observations with NaCo lie inwards of the mm ring: a clear example of dust filtering. Our preliminary results suggest that the dust grains responsible for the polarized emission are porous (>60%), small (< 3 microns), silicate grains. With our new L-band observations (also acquired by our group), we are able to rule out the presence of very massive giant planets inside the cavity. I will also present the work in progress in the search for sub-mm cold cores that can harbor pre- and proto-BDs candidates in LDN1589, one of the most active star-forming clouds in the Lambda Ori Star-forming region. For this, we carried out 870-micron continuum observations of the dark cloud using APEX/LABOCA bolometer array. We have detected a few potential candidates (with S/N >= 4) of cold cores in the data. I’m currently doing the crossmatch of the detections with catalogs at different wavelengths in order to characterize the spectral energy distribution of the detected sources and to estimate their properties (e.g. bolometric luminosity) to discriminate if these are indeed pre- and proto-BDs. With this result at hand, we plan to propose sensitive ALMA observations to study dynamic signatures of the cores to confirm their sub-stellar origin. |
2019/03/07 | Víctor Mauricio Alfonso Gómez González, IRyA-UNAM
Anfitrión: Jesús Toalá Search for Massive stars in M81 using GTC: 7 new Wolf--Rayets, analysis and classification of the total sampleWolf-Rayet (WR) stars are related to some of the most exotic and interesting astronomical objects in the Universe, e.g. the most massive stars, binaries, supernova explosions, compact objects, Gamma Ray Bursts and gravitational waves. We here report the detection of seven new WR star locations in M81 using the Multi-Object Spectrograph of the OSIRIS instrument at the 10.4-m Gran Telescopio Canarias. In this work, we analyse the entire sample of 21 spectra to specifically identify spectra that correspond to individual WR stars of one of the known sub-types. For this purpose, we explore a variety of independent methods of classification and analysis. We find 18 of our 21 detections are associated to individual stars of sub-types WNL, WNE, WCE and transitional WN/C. Our study makes M81 the farthest galaxy with individual WRs reported, thus providing a new environment for testing the massive star evolutionary models. |
2019/03/14 | Genaro Suárez, IA-UNAM Campus Ensenada
Anfitrión: Javier Ballesteros Initial Mass Function and Kinematics of 25 OrionisStar formation is a complex process that can occur over a wide range of scales. To better understand this process it is important to study the stellar initial mass function (IMF) and the kinematics of stellar groups. An excellent laboratory to carry out this kind of studies is 25 Orionis (25 Ori). Combining new deep optical photometry from DECam with optical and NIR data from the literature, we selected 1687 member candidates of 25 Ori. With this sample we derived the system IMF of 25 Ori from 12 Mjup to 13.1 Msun, which is one of the few IMFs across the whole mass range of a stellar group. The resultant system IMF is well-described by a two-part power-law function and by a tapered power-law form. We also report its best lognormal parameterization. This system IMF do not present significant variations within a radius of about 7 pc, which indicates that the substellar and stellar objects in 25 Ori do not have any preferential spatial distribution. We compared the reported system IMF as well as the substellar/stellar ratio with those of a large diversity of stellar populations and did not find significant discrepancies, which strongly supports the hypothesis that the star formation mechanism is largely insensitive to environmental conditions. Also, I present the current status of a spectroscopic survey to confirm the membership of each candidate using several world-wide facilities (GTC/OSIRIS, SDSS-III/BOSS, MMT/Hectospec, SDSS-IV/APOGEE-2 and OAN-SPM/MES). So far the survey is 75% complete and we have confirmed 530 members. With this sample of members we estimated the parameters of 25 Ori (mean values of distance, visual extinction, age, radial velocity and proper motion as well as the velocity dispersion, total mass and stellar density). Using these parameters we found that 25 Ori is a dynamically young group that is gravitationally unbound. (These are the main results of my PhD thesis project) |
2019/03/21 | Manuel Zamora-Aviles, INAOE
Dynamical dispersion of a young cluster via gravitational feedbackPhotodissociation bubbles are common features in the interstellar medium. They can be easily detected as ring-like structures in line emission maps tracing either neutral atomic or molecular hydrogen. One particularly clear case is in the $\lambda$-Ori region, which exhibits a quite symmetric, 20 pc radius ring that has been previously interpreted as to be the result of the expansion of a supernova explosion between ~1-2 Myr ago. Recently, high precision proper motions of stars in this region became available through the second data release of Gaia, which showed that the projected velocity vectors of $\lambda$-Ori stars tend clearly to point away from the center of the ring/bubble, as could be expected for an open cluster that it is breaking apart. Moreover, the data suggest that stars located farther from the center of the ring/bubble have faster (or larger) proper motions.This lead us to propose a different scenario for the formation of the $\lambda$-Ori bubble and its proper motions: In the present contribution we used numerical simulations to show that, while at the beginning, stellar clusters are formed in a collapsing environment and the stars are drawn to each other due to the gravity of the cloud, later the feedback from the newborn massive stars in these clusters expels the gas from the center, creating a cavity and moving the potential well away from the center of collapse. Since neither the formed shells nor the parental clouds are symmetric, a net force pulling out the stars is present, accelerating the stars towards the edges of the cavity. In this way, we propose that gravity from the expelled gas appears to be the crucial mechanism producing unbound clusters that expand away from their formation center. This mechanism has not been considered before, mainly because in previous simplified models the gravitational potential was usually one of an empty, homogeneous sphere, which is constant, and thus no net force is expected to act over the clusters embedded in a shell structure. |
2019/03/28 | Adam Ginsburg, NRAO
Anfitrión: Roberto Galván Star Formation in Crowds - Star formation changes with environment, and high mass stars define the neighborhoodStar formation is the defining process in the evolution of galaxies. Our present understanding of star formation has primarily been informed by low-mass stars in nearby clouds, but these nearby regions do not reflect typical conditions over the history of the universe. The denser and more crowded regions that represent our own origins exist within our Galaxy, and ALMA allows us to explore these regions in ways previously impossible. I will show that high-density regions preferentially form clusters over isolated stars. In these dense, clustered regions, the stellar initial mass function (IMF) is governed by feedback from high-mass stars, which we demonstrate using ALMA to measure gas properties and identify individual protostars. Protostar-counting measurements provide tests of star formation theories, and they show evidence that star formation density thresholds vary with environment. These measurements can be repeated throughout the Galaxy to provide strong constraints on the formation of the IMF, which will be achieved by the recently-begun ALMA-IMF large program. |
2019/04/04 | Lorena Hernández García, Universidad de Valparaíso - Chile
Anfitrión: Omaira González Restarting activity in the nucleus of Giant Radio GalaxiesGiant radio galaxies (GRG) are defined as those active galactic nuclei (AGN) whose radio morphology show linear extended emission above 0.7 Mpc. The lobes in these galaxies can be as old as 10^8 years, whereas the AGN activity can be reactivated within 10^4-8 yrs, thus GRG are perfect laboratories to study AGN evolution and restarted activity. The usual way to find restarting activity is through the radio morphology, where different phases of nuclear activity can be observed in the same dataset. However, we might be missing a fraction of restarting activity in galaxies because we are not able to detect the earliest phase where the new jets have recently formed and are not visible in the radio band. In this seminar I will focus on two cases of restarted activity on early phases, namely PBC J2333.9-2343 and Mark 1498. These sources were selected on a hard X-ray basis and we performed multiwavelength analyses in order to gain information of different emitting regions and to have the most comprehensive view of their nuclei. |
2019/04/11 | Cómputo IRyA, IRyA
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2019/04/25 | Javier Sánchez Salcedo, IA-UNAM
The gravitational disk-satellite interaction: Migration and circularization of orbitsIn many astrophysical systems, perturbers embedded in gaseous disk migrate due to the angular momentum transfer with the disk (e.g., protoplanets, black holes, globular clusters). I will discuss the different regimes that arise in the problem of the interaction between a gravitational body and a gaseous disk, for both prograde and retrograde orbits. Then, we will focus on the linear case, and compare the migration and circularization rates derived in the local approximation with those found in numerical simulations. We will discuss under what conditions the local approximation provides accurate estimates. |
2019/05/02 | Rosa Amelia González López Lira, IRyA-UNAM
The globular cluster system of NGC 4258: a relic of cosmic high noon?We present multi-object spectroscopic observations of 23 globular cluster candidates (GCCs) in the prototypical megamaser galaxy NGC 4258, carried out with the OSIRIS instrument at the 10.4 m Gran Telescopio Canarias. The candidates have been selected based on the (u* - i') versus (i' - Ks) diagram, in the first application of the \uiks\ method to a spiral galaxy. In the spectroscopy presented here, 70% of the candidates are confirmed as globular clusters. Our results validate the efficiency of the \uiks\ method in the sparser GC systems of spirals, and given the downward correction to the total number of GCs, the agreement of the galaxy with the correlations between black hole mass, and total number and mass of GCs is actually improved. We find that the metal-poor GCs co-rotate with the HI disk, even at large galactocentric distances. The ratio of rotation to velocity dispersion V/sigma of the system is ~ 1, consistent with the highly turbulent, rotating disks at z>=2 that constitute nowadays the favored environment for the formation of globular clusters. This system could be a z = 0 relic of this process. |
2019/05/16 | Laurence Sabin, IA-UNAM, Ensenada
Polarimetric studies and magnetic fields in intermediate mass evolved stars.Magnectic fields are known to be extremely relevant at various stages of stellar evolution. Indeed, several investigations have focused on the role of those fields during stellar formation (e.g. molecular clouds) and in evolved massive stars ( e.g. SN). The detection and analysis of magnetism in the short period (~10,000 yrs) corresponding to the advanced evolutive phase of intermediate mass stars, namely post-AGB and Planetary Nebulae, is less known. I will present a review of the investigations realised so far, with a focus on the most recent observational and theoretical results. In order to better tackle this issue, we also formed a group dedicated to polarization studies and composed of several researchers from various national institutions. I will then present the different activities ( i.e. instrumentations and observations) of the group. |
2019/05/23 | Laurent Loinard, IRyA-UNAM
First results of the Event Horizon Telescope: image of the supermassive blackhole at the center of M87El Telescopio de horizonte de eventos (EHT, por sus siglas en ingles) es un instrumento que combina una decena de telescopios repartidos en toda la Tierra y permite reconstruir imágenes en la banda milimétrica del espectro electromagnético con una resolución angular (del orden de 25 micro-segundos de arco) muy superior a la de cualquier otro instrumento astronómico. El 10 de abril de este año, se anunciaron los primeros resultados de este instrumento: una imagen del entorno del agujero negro supermasivo en el centro de la galaxia Messier 87 que muestra una depresión central interpretada como la sombra producida por al agujero negro mismo. En esta charla, describiremos el instrumento EHT, la técnica que utiliza, y el tratamiento de datos que permite reconstruir imágenes con este instrumento. Después, describiré la imagen de M87 obtenida, así como su interpretación en términos de modelos de magneto-hidrodinámica en el contexto de la relatividad general (GR-MHD). Terminare con unas perspectivas a futuro. |
2019/05/30 | David Alvarez Castillo, Joint Institute for Nuclear Research, Dubna Russia
Neutron Star Equation of State after the GW170817 eventIn this talk I will review the method of estimation of tidal deformabilities of compact stars and present results for pure hadronic as well as hybrid stars that include the mass twins case. Then I will discuss the impact of the nuclear symmetry energy in the determination of the compact star radius. In particular, the recent detection of gravitational radiation from the GW170817 event shed light on the properties of the neutron star equation of state (EoS), thus comprising both the study of the symmetry energy and stellar radius. Furthermore, I shall address the question of the possibility of a universal symmetry energy contribution to the neutron star equation of state under restricted Direct Urca cooling. When these two aspects are combined, powerful predictions for thestiffness of the neutron star EoS are obtained. Furthermore, I will focus on the case of mass twin compact stars, hybrid compact stars with approximately the same masses but different radii.To qualify the above, I will show a recent developed EoS that features of a color superconducting chiral quark model with nonlocal, covariantinteractions bearing density dependent vector meson coupling and a density-dependent bag pressure. This model allows for a scenario where thecompact stars of the GW170817 event are either both hadronic, both hybrid, or simultaneously hadronic and hybrid configurations. |
2019/06/06 | Jesús Toalá, IRyA-UNAM
Hot and cool gas around Wolf-Rayet starsLas estrellas Wolf-Rayet (WR) son descendientes de las estrellas masivas que se encuentranen etapas finales de su evolución, justo antes de explotar como supernovas. Debido a susfuertes vientos, éstas estrellas chocan, comprimen y calientan el material circunestelar creandolas llamadas nebulosas WR. En combinación con sus potentes flujos de fotones ionizantes, las estrellas WR son capaces de crear un medio multi-fase que puede ser estudiado a travésde observaciones multi-frecuencia. En esta charla presentamos nuestros resultados del estudiodel material caliente emisor de rayos X y del polvo detectado con observaciones IR. |
2019/06/13 | Enrique Vázquez Semadeni, IRyA-UNAM
Hierarchical gravitational collapse: the mechanism and implications for collapse timescales, cloud ages, the SFR, and cluster structure.Diverse numerical and observational evidence suggests that star-forming molecular clouds (MCs) may be in a process of global hierarchical contraction (GHC). As originally proposed by Hoyle (1953), in such a regime, a sequential destabilization of successively smaller masses should occur, leading to fragmentation of the cloud and ultimately to the formation of stellar-mass objects, when the equation of state diverts from isothermal. Early objections to the global gravitational contraction of MCs do not necessarily hold in the light of our modern understanding of turbulence and the structure of MCs. In this context, I discuss how the HGC mechanism implies a nearly pressureless collapse of mMCs and an initial acceleration of the star formation activity. These features naturally explain the ubiquitous formation of filamentary structures that funnel material to so-called "hubs", the observed morphology of the magnetic field around the filaments, the scattered nature of low-mass star-forming regions, the observed SFR-mass relations at both the local (cloud) level and the global (galactic) level, and the structure of the embedded stellar associations, such as their fractal structure and the observed radial mass and age gradients, as well as their stellar-age histograms. |
2019/08/01 | Carlos Gershenson, C3 e IIMAS - UNAM
Enfrentando la Complejidad de la Movilidad UrbanaLos problemas de movilidad urbana nos afectan a todos. Si no hacemos nada, seguirán empeorando. Tiempos de traslado, contaminación, pérdidas económicas, impacto a la salud: todos reducen nuestra calidad de vida. ¿Cómo es que no hemos podido mejorar la movilidad más rápido de lo que empeora? Mi respuesta es: porque no hemos comprendido la complejidad de la movilidad. Usamos técnicas tradicionales, las cuales son adecuadas sólo para problemas "estacionarios". Pero las interacciones inherentes a la complejidad de la movilidad urbana generan cambio impredecible, que llevan a problemas "no estacionarios". ¿Cómo enfrentar esta complejidad? Con adaptación. Esta puede lograrse por medio de la auto-organización. Presentaré dos ejemplos: en la coordinación de semáforos y en regulación de transporte público. |
2019/08/08 | Roberto Galván Madrid, IRyA-UNAM
The radio/submm view of massive, deeply embedded clusters in our GalaxyI will present recent observational and modelling results that tackle the following important issues on star-cluster formation: i) The diversity of massive, cluster forming clouds, and a possible origin for it. ii) Evidence for gas accretion from GMC ($\sim 50$ pc) to disk ($< 1000$ au) scales. iii) The first censuses of the stellar populations in formation, i.e., YSO counting in massive protocluster clouds. iv) The effects of feedback from massive YSOs on their natal cores and clumps. |
2019/08/15 | Gloria Koenigsberger, Instituto de Ciencias Físicas-UNAM
La evolución de estrellas masivas y el curioso caso de HD 5980.HD5980 es un sistema múltiple ubicado en la Nube Menor de Magallanes. Su componente principal es un sistema binario eclipsante, excéntrico, con un período orbital de 19.3d, y masa total de aproximadamente 120 M_sun. Ambas parecen ser estrellas Wolf-Rayet, y sus propiedades sugieren que son el producto de evolución con mezclado muy eficiente. Es decir, las trazas evolutivas que mejor las describen corresponden a los modelos de Quasi-chemically homogeneous evolution, QCHE calculados por el grupo de Bonn. Las trazas de QCHE resultan de un mezclado casi completo del material nuclear con el de las capas externas de la estrella. En los modelos estandard, este mezclado se logra únicamente si la estrella rota muy rápidamente durante gran parte de su vida. En esta charla hablaré sobre un posible mecanismo alternativo en sistems binarios como HD5980, basado en el tipo de rotación diferencial inducida por las fuerzas de marea. |
2019/08/29 | Peter Otto Hess, ICN-UNAM
Anfitrión: Laurent Loinard Comparing the pseudo-complex General Relativity with the EHT observationThe motivation for a pseudo-complex General Relativity will be given and the main structure will be resumed. Simulations of a thin accretion disk are presented and compared to the observation of the black hole in M87 by the EHT collaboration. Some problems are discussed. |
2019/09/05 | Anibal Sierra, IRyA-UNAM
Effects of scattering on the emergent intensity of protoplanetary disks and their apparent 7 mm excessDust scattering can be a very important opacity source in protoplanetary disks observed at radio wavelengths with ALMA and VLA. However, scattering is usually neglected in analysis of multi-wavelength observations because it increases the complexity of Monte Carlo simulations and is time consuming. In this talk, I present an analytical solution of the emergent intensity of a vertically isothermal face-on disk, taking into account the scattering in the radiative transfer equation. The emergent intensity with scattering modifies the spectral indices compared with that of the non-scattering emission. The shape of the spectral energy distribution is also modified, depending on the disk inclination in the plane of the sky which increases with the optical depth. Finally, we used the scattering effects to give an alternative explanation to the observed excess emission reported at a wavelength of 7 mm in several disks. These results were recently implemented to explain the radial dust distribution in the HL Tau disk. |
2019/09/19 | Luis Felipe Rodriguez, IRyA-UNAM
Regreso a OriónOrion is the region of massive star formation closest to the Sun and in consequence it has been studied in detail. I will present three recent results from the IRyA group on this region. The first one is the ultraprecise determination of the distance to Orion using VLBI observations of stars with non-thermal emission. The second result is a study of the kinematics of the stars with either termal or non-thermal emission. Finally, we will focus on the extraordinary “explosion” that seems to have taken place in the Orion BN/KL region. Not only the molecular gas but also several stars are receding from a point in common with velocities of hundreds of km/s for the gas and of tens of km/s for the stars. We will present the most recent data on the proper motion of the stars and discuss the models that have been proposed to explain this phenomenon. |
2019/09/26 | Ricardo Chavez, IRyA-UNAM
HII Galaxies as Cosmic LaboratoriesWe present new high spectral resolution observations of 15 high-z (1.3 ≤ z ≤ 2.5) HIIG obtained with MOSFIRE at the Keck Observatory. These data, combined with already published data for another 31 high-z and 107 z ≤ 0.15 HIIG, are used to obtain new independent cosmological results using the distance estimator based on the established correlation between the Balmer emission line velocity dispersion and luminosity for HIIG. Our results are in excellent agreement with the latest cosmological con- cordance model (ΛCDM) published results. From our analysis, we find a value for the mass density parameter of Ω_m = 0.290 + 0.056 - 0.069 (stat). For a flat Universe we constrain the plane {Ω ; w } = {0.280 + 0.130 - 0.100; −1.12 + 0.58 - 0.32} (stat). The joint likelihood analysis of HIIG with other complementary cosmic probes (Cosmic Microwave Background and Baryon Acoustic Oscillations) provides tighter constraints for the parameter space of the Equation of State of Dark Energy that are also in excellent agreement with those of similar analyses using Type Ia Supernovae instead as the geometrical probe. |
2019/10/03 | Eric Martínez García, INAOE
Comparing SPS models in resolved nearby disk galaxiesThe dust component affects the measurements of galaxy properties since dust absorbs and re-emits the starlight from the UV and the optical radiation. The latter process enables the prediction of the emission of radiation at infrared-submillimeter-radio wavelengths, by fitting evolutionary stellar population synthesis (SPS) models to observed UV-optical-NIR observations and assuming a dust emission model. Nevertheless, the predictions depend on the choice of the SPS model, e.g., Bruzual and Charlot (2003), or the Maraston (2005) models. This is mainly due to the different treatments of the thermally pulsing asymptotic giant branch (TP-AGB) phase of stellar evolution. Comparisons of the SPS models with resolved (e.g., pixel-by-pixel) observations (at optical and NIR wavelengths) can be used to discriminate between models. We will show the results of these comparisons to a sample of nearby disk galaxies. |
2019/10/10 | Omar López-Cruz, INAOE
A 40 Billion Solar Masses Black Hole in Holm 15A: The End of the Bonfini vs. López-Cruz Controversy?
A 40 Billion Solar Masses Black Hole in Holm 15A: The End of the Bonfini vs. López-Cruz Controversy?We have embarked on the search for ultramassive black holes (UMBH), those whose mass is larger than 10 billion solar masses. I discuss the reliability of different BH mass indicators, followed by discussion of Holm 15A and IC 1101 a plausible candidates to hosting UMBH, I will spice the talk with my own take on the recent controversies that have arisen regarding the core size (inner flattening of the surface brightness distribution) of those galaxies. I, then discuss the feasibility of IFU observations, which can help us to uncover dynamical constraints on the fusion of supermassive black hole binaries (SBHB) as a stage of UMBH formation. In 2014 I led an international team who suggested that the galaxy Holm 15A might host the most massive black hole in the nearby universe. Four months ago, a German team led by K. Merhgan, a graduate student, reported a BH mass of 40 billion solar masses for Holm 15A. This is the largest BH mass ever measured in the nearby universe. |
*2019/10/15 | Javier Mejuto, Departamento de Arqueoastronomía y Astronomía Cultural UNAH, Honduras
Anfitrión: Jacopo Fritz Otros cielos, otros universosDesde los albores de la humanidad podemos apreciar el interés del ser humano por observar y conocer el espacio celeste que siempre le ha rodeado. Al hacerlo el universo ha dado forma a su cultura y las diferentes culturas, incluida la nuestra, han visto el universo a través del filtro propio de su cultura. En este caso nos centraremos en la tradición astronómica meso y centroamericana que sigue vigente, a través de los pueblos originarios, por más de 15.000 años. A través de este viaje veremos cómo para cada pueblo el cielo es un espacio vivo donde se aúnan anhelos, historias y conocimiento, un lugar de encuentro que todos los seres humanos compartimos, el lugar que nos hace humanos |
2019/10/24 | Victor Berrueta, GIRA
Anfitrión: Jane Arthur |
2019/10/31 | Amira Tawfeek, IRyA-UNAM
Anfitrión: Bernardo Cervantes Are Galaxy Triplets Physically Bounded Systems?Galaxy triplets represent one of the most interesting laboratory in identifying the formation and the evolution of galaxies. Understanding such systems will give us clues about the construction of larger groups and clusters of galaxies. Towards that, we conduct a statistical study on 315 isolated triplet systems taken from the ¨SDSS-based catalog of Isolated Triplets¨ (SIT) to obtain their physical and dynamical parameters. Meanwhile, the correlation between the dynamical parameters of these systems and the Large-Scale Structure (LSS) have been presented. For further details about triplet systems and signs of interactions between their members, we applied surface photometry analysis and decomposition on nine galaxy triplets to declare their radial profiles and identify their fine structures. We found that triplet systems follow hierarchical structure in their formation and evolution. In addition, we found that signs of interactions are pronounced in systems with small projected separations between their members (rp < 0.3 Mpc). |
2019/11/07 | Martín Guerrero, Instituto de Astrofísica de Andalucía
Anfitrión: Jesús Toalá Variable hard X-ray emission fromwhite dwarfs and central stars of PNeSingle central stars of planetary nebulae (PNe) and isolated white dwarfs (WDs) can produce stable photospheric soft X-ray emission. Moreover shocks in the stellar winds of the central stars of PNe can produce stochastic harder X-ray emission. Therefore, the detection of modulated hard X-ray emission necessarily implies accretion or chromospheric emission from a companion. We will present in this talk two of the most notorious cases of hard X-ray emission from the central star of a PN and a WD. Since the presence of a chromospherically active dwarf companion can be unambiguously rejected, accretion processes need to be invoked. The implications for the nature of the unseen companions are surprising, ranging from a WD companion up to … a substellar companion. |
2019/11/14 | Nuria Huélamo, Centro de Astrobiología (CSIC-NASA) España
Anfitrión: Aina Palau A search of protoplanets through Halpha observationsDuring their formation, young planets are surrounded by disks of gas and dust, the so-called circumplanetary disks. Several works have predicted that, as observed in young stars, protoplanets can accrete material from their disks and emit in accretion tracers like e.g. the Halpha emission line. This scenario has been recently confirmed with the detection of two young planets through Halpha imaging (PDS70bc). In this talk I will show preliminary results from a project to detect accreting protoplanets around young stars using SPHERE/ZIMPOL at the Very Large Telescope (VLT). I will discuss the sample, the observational strategy, and our main findings. |
*2019/11/15 | Sebastián Sanchez Sanchez, IA-UNAM
Anfitrión: Omaira González Spatially Resolved Spectroscopic Properties of Low-Redshift Star-Forming GalaxiesI review here the spatial resolved spectroscopic properties of low-redshift star- forming galaxies (and their retired counter-parts), using results from the most re- cent Integral Field Spectroscopy galaxy surveys. First, I present the global spec- troscopic properties of these galaxies, including their main ionization process, their star-formation rate, oxygen abundance, and average stellar ages and metal- licities. I show how they depend on galaxy morphologies and stellar masses. Second, I present the local distribution of the ionising processes, to the kilopar- sec scales, and the radial distributions of the surface densities of the properties explored globally, and how they depend on the integrated galaxy properties. Third, I show how the global evolutionary relations found between integrated parameters (like the SFMS, MZR and SK-law) present local counter-parts, be- ing the global ones just integrated/average versions of them. Finally, I sum- marise all these result under the scenario of inside-out growth and quenching of galaxies, and how this latter process is related to the dynamical state of the galaxies. |
2019/11/21 | Ana Torres Campos, INAOE-GTM
Anfitrión: Ricardo Chávez Estudio fotométrico espacialmente resuelto en galaxias HII con diferente morfologíaThe main goal of this study is to characterise the stellar populations in very low metallicity galaxies. We have obtained broad U, B, R, I, J, H, intermediate Strömgren y and narrow Hα and [OIII] deep images of three H II galaxies with different morphology. The stellar populations dominating the stellar cluster complexes (SCC) in the galaxies have been characterised by comparing the observed broad band colours with those of single stellar population models. The main results of this work are consistent with the galaxies containing an old extended component on top of which the young stellar populations are distributed, enclosed inside a luminous diffuse Ha emission. The spatial distribution of the SCCs and H II regions indicates that star formation in the three galaxies is more likely stochastic and simultaneous within short time scales. In the three galaxies the dominating stellar populations in the SCCs were characterized with a variety of ages ranging form 1 Myr to 10 Gyr. Some of them are candidates to contain Wolf-Rayet clusters and 11 of them were identified as being dominated by Super Stellar Clusters (Age >= 10 Myr and Mass >= 10^5 Msun).The NIR colours of four SCCs in one of the galaxies suggest that these contain a larger amount of RSG stars than what the SSP models predict. The mismatch between observations and models however cannot be attributed alone to a mistreat of the RSG phase and needs to be further investigated. |
*2019/11/27 | Denija Crnojevic, The University of Tampa
Anfitrión: Verónica Lora Resolving the extended stellar halos of nearby galaxies: the future of Near-Field CosmologyThe widely accepted Lambda Cold Dark Matter paradigm faces important challenges at the scales of individual galaxies, primarily linked to the implementation of baryonic physics in cosmological simulations. The study of resolved stellar populations in the nearest galaxies, or "near-field cosmology", provides key constraints on the physics underlying galaxy formation and evolution. In this talk, I will present the ongoing Panoramic Imaging Survey of Centaurus and Sculptor and the Magellanic Analog Dwarf Companions And Stellar Halos survey, targeting galaxies in the Local Volume within a range of masses and environments. The unique strength of such surveys is the exquisite synergy between wide-field, ground-based imaging and their extensive follow-up campaigns (HST, Keck, VLT, Magellan, AAT). Such surveys constitute the first accurate characterization of the past and ongoing accretion processes shaping the halos of these nearby galaxies and their satellite populations: they do not only quantitatively inform theoretical models of galaxy formation and evolution, but also represent a necessary testbed in preparation for the next generation of ground-based (LSST, GMT, TMT) and space-borne telescopes (JWST, WFIRST). |
2019/11/28 | Karin Hollenberg, IRyA-UNAM
Anfitrión: Karin, Omaira, Charly |
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