* 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
* Special colloquium