| 2023/02/09 | Rosa Amelia González López-Lira, IRyA
Host: Jesús Toalá The relation between GC systems and SMBH in spiral galaxies: The link to the M_\bullet - M_\ast$ correlationWe explore the relationship between globular cluster total number, $N_{\rm GC}$, and central black hole mass, $M_\bullet$, in spiral galaxies. Including cosmic scatter, log $M_\bullet \propto$ (1.64 $\pm$ 0.24) log $N_{\rm GC}$. Whereas in ellipticals the correlation is linear [log $M_\bullet \propto$ (1.02 $\pm$ 0.10) log $N_{\rm GC}$], and hence could be due to statistical convergence through mergers, this mechanism cannot explain the much steeper correlation in spirals. Additionally, we derive total stellar galaxy mass, $M_\ast$, from its two-slope correlation with $N_{\rm GC}$ (Hudson et al.\ 2014) for both spirals and ellipticals. In the $M_\bullet$ versus $M_\ast$ parameter space, with $M_\ast$ derived from $N_{\rm GC}$, $M_\bullet \propto$ (1.48 $\pm$ 0.18) log $M_\ast$ for ellipticals, and $M_\bullet \propto$ (1.21 $\pm$ 0.16) log $M_\ast$ for spirals. The observed agreement between ellipticals and spirals may imply that black holes and galaxies co-evolve through ``calm” accretion, AGN feedback and other secular processes. |
| 2023/02/16 | Benne Holwerda, University of Louisville
Host: 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
Host: Jesús Toalá Nova expansion and their difussion into the ISMSpectroscopic observations of nova remnants can be used to determine their basic properties and reveal details in their structures. However, until now ver few studies have been presented in the literature. In this talk I will present results of the analysis on the dynamics of the ejecta of classical novae and their diffusion into the ISM. In addition, I will present morpho-kinematic results obtained from multi-epoch images and spectroscopic data, including integral fiel spectroscopic from the GTC MEGARA. These allowed us for the first time a more realistic view of nova remnants. |
| 2023/02/23 | Vianey Camacho, IRyA
Host: Enrique Vázquez The kinetic and magnetic energy budget of hub-filament systems during the gravitational fragmentation of molecular cloudsWe present a numerical study of the balance between the gravitational (Eg), kinetic (Ek), and magnetic (Em) energies of the clumps and cores within a hub-filament system in a numerical simulation of cloud formation and evolution undergoing global hierarchical collapse (GHC), and compare our results with an observational sample of dense cores. We investigate the scaling of Ek and Em with |Eg| and their corresponding virial parameter $\alpha$ and Larson ratio $L= v/R^0.5$, where $v$ is the velocity and R is the size. Our results show that the magnetic $\alpha$ and $L$ parameters follow similar scalings as their kinetic counterparts, although the ratio Em/Ek decreases as |Eg| increases. The largest objects tend to be gravitationally bound, while their internal substructures tend to appear unbound. The magnetic and kinetic virial parameters exhibit a large scatter at low masses $M$, as do the corresponding Larson ratios at low column density ($\Sigma$). This scatter is strongly reduced when Ek and Em are plotted directly against |Eg|, suggesting that the main controlling parameter of the energy budget in the structures is Eg and that they derive their kinetic and magnetic energies from it. At large masses/column densities, the structures tend to be moderately subvirial, in agreement with observations. The observational data points in the $\alpha$-$M$ and $L$-$\Sigma$ diagrams overlap or continue the trends followed by the numerical data, suggesting that the GHC scenario is consistent with observations. |
| *2023/03/01 | Shmuel Bialy, Center for Astrophysics
Host: 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
Host: Jesús Toalá What do super star clusters tell us?In addition to globular clusters and open clusters, there is a classification of clusters with features resembling those of globular clusters, the so-called super star clusters (SSCs). In this talk, we summarize three main results regarding SSCs: (i) In the first place, we present the fitting tool nProFit, focused on fitting dynamical models to star clusters to obtain dynamically-relevant parameters, such as masses, densities, core and half-light radius, and velocity dispersions. In order to have a robust study of SSCs, we use nProfit to fit the surface brightness profiles of the disk population of clusters in the M82, which is a starburst galaxy with a nearly coeval population, harboring around 400 SSCs. (ii) in the light of the obtained masses and radii, we address the Cluster Initial Mass Function of M82 disk SSCs, using the dynamical evolution code Evolve Me a Cluster of Stars (EMACSS), to reproduce the current observed Cluster Mass Function and its implications. (iii), As a final result, and considering striking indirect evidence of the existence of intermediate-age RR Lyrae stars (RRLs), we use a sample of SSCs and old clusters in the Magellanic Clouds, and cross-matched it with Gaia DR3 and OGLE data, in order to find direct evidence of the existence of intermediate-age RRLs. We present a bayesian inference to compute membership probabilities of the matched stars and show the inferred RRLs frequencies per solar mass. |
| 2023/03/09 | Roberto Galván Madrid, IRyA
Host: 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
Host: Sundar Srinivasan Structural evolution of star-forming galaxies at 0.5 |
| 2023/03/23 | Josep Miquel Girart, Instituto de Ciencias del Espacio (España)
Host: Aina Palau Magnetic fields threading star forming cores: The ALMA viewMagnetic fields permeate star-forming material on every spatial scale, from the scales of entire galaxies, to the ∼100 pc scale of molecular clouds, to the ∼0.1 pc scale of protostellar cores, and all the way down to innermost regions of protostellar envelopes (∼100 au scales) where planets form within rotationally supported disks around young stars. In the (sub)millimeter regime, these magnetic fields are mainly inferred by observing polarization from magnetically aligned dust grains. In this talk, I will summarize the main results obtained from dust polarization ALMA observations toward star forming regions from scales of few thousand to few tens of au. First, I will also describe the general properties derived of the polarization observed with ALMA at these scales, discuss the origin of the polarized signal in different environments. Then, for the cases where the dust polarization appears to trace the magnetic fields, I will show some general trends and properties of the magnetic fields, and their relevance to the star formation process. Finally, I will show some examples of selected regions observed with ALMA, which are of special interest. |
| 2023/03/30 | Alice Pasetto, IRyA
Host: 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
Host: 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
Host: 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
Host: Sundar Srinivasan This is not an AGN: the story of the symbiotic star 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
Host: 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
Host: 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
Host: Sundar Srinivasan Dynamical evolution of planetary systems and its connection to metal pollution in white dwarf atmospheresIt is well stablished that between 25-50% of white dwarfs (WDs) have metallic elements in their atmospheres, which is observational evidence of their remaining planetary systems. The paradigm to explain the presence of material located at a few solar radii from the WD involves planets that have survived the stellar evolution of their host star and somehow have destabilized asteroids and other planets and have sent them to star-grazing orbits, where the WD’s tidal forces can disrupt them, hence, producing the observed phenomenology. Different theoretical studies have analyzed the dynamical stability of planetary systems by N-body simulations through stellar evolution with the objective to understand the origin of the so called WD’s metal pollution. Following this line of research and pursing the same goal, in this work, I performed thousands of N-body simulations of planetary systems with more than two planets, evolving the host star from the main sequence to the WD phase and building the planetary templates by taking as basis the architectures of the hundreds of observed exo-planet systems with multiple planets. This parameter set up allows to constrain and at the same time to expand the physical and orbital parameter space explored previously by other studies. Besides, in order to understand the role of planet multiplicity in WD metal pollution, I evolved a new set of simulations with a controlled parameter space in such a way that the only variable is the number of planets. The main result of this work shows that the more planets the system has, the more likely is to have a dynamical instability (planet loss, orbit crossing and/or orbital scattering) on the WD phase, highlighting that the planet multiplicity plays an import role in triggering dynamical instabilities that may contribute to WD metal pollution. Even the fraction of unstable simulations with 4, 5 and 6 planets with architectures based on the observed exo-planet systems is comparable to the observed prevalence of metal polluted WDs. Furthermore, simulations with a high planet multiplicity resulted in a non-negligible number of unstable systems on the WD phase with planets reaching star-grazing orbits (some of them crossing the WD’s Roche radius). This latter result suggests a natural mechanism to originate close-in planets to WDs as the Jovian planet WD1856b recently discovered with an orbital period of 1.4 days. Additional results evince that the number of dynamically unstable events peaks in the first Gyr of the WD’s cooling time and it decreases as the WD ages, where systems involving low-mass planets ( Mp < 100 Mearth) are dynamically active for Gyr time-scales while systems with high-mass planets (Mp ≥ 100 Mearth) tend to be unstable in Myr time-scales. |
| 2023/05/25 | Jacopo Fritz, IRyA
Host: Ramandeep Gill Under pressure: galaxies’ lives in clustersThe physical characteristics of galaxies, such as the properties of their stellar populations, their interstellar medium content, and their morphologies, are subject to evolution across a galaxy life. In massive structures such as galaxy clusters, these changes can happen very efficiently in such a way that the cluster galaxy population is dramatically different at different cosmic epochs. Generally speaking, galaxies found in local clusters, are predominantly early types, while the vast majority of late tape ones are red and basically quenched. Various physical mechanisms have been proposed to explain these differences with respect to “isolated” galaxies, both with respect to their morphology and their stellar populations, and most of them involve the ability of the cluster environment to efficiently remove the ISM of infalling galaxies. In this talk, I will review the effects of ram pressure, one of the most efficient mechanisms responsible for these changes, highlighting positive effects on star formation and a possible role on morphological changes as well. |
| *2023/05/30 | Donaji Esparza, IAC/La Laguna
Host: 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
Host: 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
Host: Gilberto Gómez |
| *2023/06/12 | Ue Li, ASIAA
Host: 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
Host: 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
Host: Eric Jiménez y Diana García |
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| 2023/08/10 | Auditorium unavailable, T.B.D.
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| 2023/08/17 | Alessia Moretti, INAF/Padova
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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, T.B.D.
Host: Alice Pasetto |
| 2023/10/12 | Auditorium unavailable,
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| *2023/10/17 | Javier Ballesteros, IRyA
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| 2023/10/19 | Sundar Srinivasan, IRyA
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| 2023/10/26 | Omaira González, IRyA
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| 2023/11/09 | Ariel Werle, T.B.D.
Host: Jacopo Fritz |
| 2023/11/16 | Violeta Gamez Rosas, Leiden Observatory
Host: Omaira González |
| 2023/11/23 | T.B.D., T.B.D.
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| 2023/11/23 | Auditorium unavailable,
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* Special colloquium
* Special colloquium
| 2021/02/18 | Camilla Pacifici, STScI
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
A Radio Pinwheel Associated with WR147Wolf-Rayet (WR) stars are evolved massive stars, characterized by high luminosities and fast and dense stellar winds. We have detected a radio continuum pinwheel associated with WR 147, a nitrogen-rich WR star. These structures have been detected in the infrared around a handful of late-type carbon-rich WR stars with massive companions, where dust has formed in the zone where the two winds collide and produced a plume of dense gas and dust that is carried out with the WR wind. As the binary system rotates, an Archimedean spiral is produced. The resulting pinwheel contains information on wind speeds, wind-momentum ratio, and orbital parameters. However, WR 147 is a WN star and the formation of dust is unlikely, so a different emission mechanism must be at work. Our analysis of the data suggests that in this case the emission is dominantly of a nonthermal nature (synchrotron). It is possible that the pinwheels associated with WN stars will be detectable only as nonthermal emitters at radio wavelengths. From the characteristics of the pinwheel we estimate a period of 1.7 yr for the binary system (the WN star and a companion yet undetected directly) that is responsible for the pinwheel. |
| 2021/04/15 | Luis Felipe Rodríguez, IRyA-UNAM
Observations of Atomic Hydrogen at Cosmic DawnAfter the epoch of recombination at z = 1100 the Universe entered into the so-called Dark Ages, when hydrogen was neutral and observations have not been possible until recently. Gamma-ray bursts have been detected at values as high as z = 11. But between these two values of z there were no detections. In 2018 the EDGES collaboration reported the detection of highly redshifted HI in absorption between z = 15 and 20. The depth of the absorption cannot be explained in terms of standard cosmology and three possible explanations have been proposed: 1) the observations are wrong, 2) there is an exotic physics process and 3) there is an additional radio background to the known cosmic background. I will discuss possible radio sources that could account for the last possibility. |
| 2021/04/22 | Américo González Esparza, Instituto de Geofísica, UNAM
Host: Vicente Rodríguez First Observations of the New MEXART's Digital SystemThe Mexican Array Radio Telescope (MEXART) is a transit instrument mainly dedicated to perform Interplanetary Scintillation (IPS) observations of extragalactic sources with a central operation frequency of 139.6 MHz. The main scientific objective is to perform studies of solar wind properties and space weather perturbations. The site is located in Coeneo, Michoacan (19.810 N, -101.690 W) at about 80 km from Morelia. The antenna contains 4096 fullwavelength dipoles ordered in a 64x64 array. In 2016, the observatory became the main site of the National Space Weather Laboratory (LANCE). The MEXART was originally operating with a 16x16 Butler Matrix, which produced 16 fixed latitudinal beams at different declinations. Using 1/4 of the antenna (16 E-W lines), the MEXART began operations and reported the first measurements of IPS sources, the detection of solar wind transient events, and the systematic observations of a few IPS sources to infer the yearly variation of their scintillation index. However, the MEXART’s analogue back-end system had several problems. The 16 beams produced by the Butler matrix had poor directivity (with very large secondary beams), which caused significant gain losses and that the instrument did not reach the expected performance. Problems with the antenna signals arriving at the backend, in power and phase, did prevent that the radio-telescope could detect the number of radio sources required to monitor the solar wind between the Sun and the Earth. In order to solve this problem, we commissioned the design and construction of a new backend’s digital system. The new digital system solved the problems with the beam forming system, increased the bandwidth and improved the instrument’s sensitivity. We present the first light of the MEXART’s digital system. We describe the new technical capabilities of the instrument, and we show some preliminary results: an estimation of the instrument’s sensibility, the observation of the transit of the Galaxy at 140 MHz, and some IPS observations. |
| 2021/04/29 | Henrik Beuther, MPIA
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: Omaira & Karin |
| 2021/08/19 | Enrique Vázquez, IRyA-UNAM
Host: 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
Host: Enrique Vázquez Could quantum mechanics explain the dark universe?We know that Quantum Mechanics was developed to explain the micro-world: atoms, molecules, etc. In this talk we show how the Schrödinger equation and the simplest concepts of quantum mechanics can explain the most controversial phenomena of dark halos, such as the core-cusp problem, the number of galaxies satellites around the big ones, the anomalous behavior of the trajectories of the galaxies satellites, etc. and how elementary concepts of quantum mechanics give us an explanation for the accelerated expansion of the universe, without dark energy. |
| 2021/09/02 | Alberto Carramiñana, INAOE
Host: Luis Felipe Rodríguez The Cygnus Cocoon: a powerful star forming particle acceleratorIn resonance to ideas put forward by Enrico Fermi more than sixty years ago, Galactic cosmic rays are generally believed to originate in supernova remnants, where rapidly moving shocks should allow for particle acceleration up to the PeV range. The development of high-energy observatories capable of scanning the Galactic Plane has enabled to test the Fermi paradigm. While supernova remnants have been found among the sources of TeV gamma rays, tracers of very high energy cosmic rays, their gamma-ray spectra do not appear to extend beyond some tens of TeV. Recent observations of the Cygnus region with the HAWC gamma-ray observatory of photons with energies in the 100 TeV range show that star forming regions are able to provide very high energy cosmic rays and may be more suitable sources at the higher energies. |
| 2021/09/09 | Thomas Nony, IRyA-UNAM
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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. |
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| 2021/11/25 | Patricia Piñones Vázquez, Centro de Investigación y Estudios de Género
Host: 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
Host: 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
Host: 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. |
* Special colloquium
* Special colloquium
| *2019/01/22 | Rodolfo Montez, Smithsonian Astrophysical Observatory
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: Jane Arthur |
| 2019/10/31 | Amira Tawfeek, IRyA-UNAM
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: 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
Host: Karin, Omaira, Charly |
* Special colloquium
* Special colloquium
* Special colloquium
* Special colloquium
* Special colloquium