Title: THE ROLE OF SHOCKS IN THE EMISSION OF THE SINGLY IONIZED CARBON  IN GALAXIES

SUMMARY:

The fine structure [CII] line at 157.7um is considered a good tracer of star formation because it is unaffected by dust attenuation and it is bright enough to be detected in high-z galaxies. This happens because the singly ionized carbon C+ collisionally excited by the surrounding neutral atomic and molecular hydrogen acts as the main coolant for the molecular clouds heated by young bright stars in galaxies. In this talk I will present a few cases of nearby galaxies where shocks are instead the reason for the [CII] emission. In particular I will talk about galaxies where jets from the central AGN affect the interstellar medium at great distance from the nucleus and about a few other cases where shocks from galaxy interactions are at the origin of a [CII] emission excess.

Cometary emission processes: fingerprints of their physical and chemical behavior

I will discuss key atomic and molecular processes in cometary atmospheres.  Like comets in our solar system, it will be difficult if not impossible to directly study the physical and chemical properties of comets around other stars. Instead, we have to infer these properties from the gas and dust surrounding them. Atomic and molecular reaction such as dissociation, ionization, and charge exchange both alter gases surrounding comets. Because many reactions result in the emission of light, they also offer insight into the composition and radiation environment exocomets are exposed to. In this presentation I will provide a broad review of radiative processes in cometary atmospheres, with a particular focus on spectral modeling, observational opportunities, and anticipated challenges in the interpretation of new observations, based on our current understanding of the atomic and molecular processes occurring in the atmospheres of small, icy bodies. Close to the surface, comet atmospheres form a thermalized atmosphere tracing the irregular shape of the nucleus. Gravity is too low to retain the gas, which flows out to form a large collisionless exosphere. As such, cometary comae represent conditions that are both familiar, as well as unattainable in laboratories on Earth, necessitating state-of-the-art theoretical treatments of the relevant microphysical processes. Radiative processes offer direct diagnostics of the local conditions, as well as the macroscopic coma properties. Finally, measurements of cometary compositions are uniquely valuable because they provide information on the formation and evolution of our solar system, but extracting chemical abundances from spectroscopic measurements of the coma requires detailed models that span a broad range of physical regimes (both macroscopic and microscopic).

Cometary emission processes: fingerprints of their physical and chemical behavior

I will discuss key atomic and molecular processes in cometary atmospheres.  Like comets in our solar system, it will be difficult if not impossible to directly study the physical and chemical properties of comets around other stars. Instead, we have to infer these properties from the gas and dust surrounding them. Atomic and molecular reaction such as dissociation, ionization, and charge exchange both alter gases surrounding comets. Because many reactions result in the emission of light, they also offer insight into the composition and radiation environment exocomets are exposed to. In this presentation I will provide a broad review of radiative processes in cometary atmospheres, with a particular focus on spectral modeling, observational opportunities, and anticipated challenges in the interpretation of new observations, based on our current understanding of the atomic and molecular processes occurring in the atmospheres of small, icy bodies. Close to the surface, comet atmospheres form a thermalized atmosphere tracing the irregular shape of the nucleus. Gravity is too low to retain the gas, which flows out to form a large collisionless exosphere. As such, cometary comae represent conditions that are both familiar, as well as unattainable in laboratories on Earth, necessitating state-of-the-art theoretical treatments of the relevant microphysical processes. Radiative processes offer direct diagnostics of the local conditions, as well as the macroscopic coma properties. Finally, measurements of cometary compositions are uniquely valuable because they provide information on the formation and evolution of our solar system, but extracting chemical abundances from spectroscopic measurements of the coma requires detailed models that span a broad range of physical regimes (both macroscopic and microscopic).

Black hole accretion flows: from nearby stellar binaries to quasars at cosmic dawn

Accretion onto black holes transforms the darkest objects in the universe into the brightest. I will review what we know about the emission from the accretion flow, starting with the stellar mass black holes in binary systems in our own galaxy. Scaling up to the supermassive black holes in active galaxies and quasars reveals both similarities and differences. One of the key similarities is the 'changing look' phenomena in active galaxies, where the UV continuum associated with an optically thick accretion flow drops over a few months/years, triggering the disappearance of the characteristic broad emission lines, analogous to the state transition in binaries. One of the key differences is the nature of the accretion flow above the transition luminosity, where the stellar mass black holes look like standard discs and have variability timescales like standard discs while the supermassive ones do not. Only at the highest luminosities (extreme narrow line Seyfert 1 galaxies and the weak line quasars) does the accretion flow match to the disc models. I will speculate on the physics underlying all the behavior, and give a united picture of the accretion flow.

Black hole accretion flows: from nearby stellar binaries to quasars at cosmic dawn

Accretion onto black holes transforms the darkest objects in the universe into the brightest. I will review what we know about the emission from the accretion flow, starting with the stellar mass black holes in binary systems in our own galaxy. Scaling up to the supermassive black holes in active galaxies and quasars reveals both similarities and differences. One of the key similarities is the 'changing look' phenomena in active galaxies, where the UV continuum associated with an optically thick accretion flow drops over a few months/years, triggering the disappearance of the characteristic broad emission lines, analogous to the state transition in binaries. One of the key differences is the nature of the accretion flow above the transition luminosity, where the stellar mass black holes look like standard discs and have variability timescales like standard discs while the supermassive ones do not. Only at the highest luminosities (extreme narrow line Seyfert 1 galaxies and the weak line quasars) does the accretion flow match to the disc models. I will speculate on the physics underlying all the behavior, and give a united picture of the accretion flow.

The fifth incarnation of the Sloan Digital Sky Survey (SDSS-V) began taking data last year and is in the process of transitioning to the use of a robotic positioning system. I will described the SDSS-V Milky Way Mapper program and its goals. The first of its major goals is to understand the history and structure of the Milky Way. Following upon work done with the APOGEE-1 and 2 surveys the Milky Way Mapper will use approximately 6 million stars to trace out the detailed structure of the Galaxy. The second major goal is to understand stellar astrophysics. The Milky Way Mapper contains several smaller programs called cartons, whose goals cover a wide variety of stellar candidates including white dwarfs, binary stars, young stellar objects, planet hosts, asteroseismology targets and x-ray binaries. These cartons will allow us to explore all sorts of interesting topics that can only be done with a large-scale spectroscopic survey. I will give updates on the current progress of the survey, and lay out our plans for the future.

The deaths of massive stars seed our universe with black holes and neutron stars - the most exotic objects of the stellar graveyard. The births of these stellar remnants, as well as their mergers when paired in binaries, power explosions that can launch the most relativistic jets we know of in the universe (gamma-ray bursts) and shake the very fabric of space-time via ripples called gravitational waves. GW170817, the merger of two neutron stars witnessed through both its gravitational wave siren and its glow at all wavelengths of light, represents the first multi-messenger detection of one such extreme cosmic bang. Starting from the example of GW170817, in this talk I will discuss how radio light in particular, and gravitational waves, can be used in tandem to unveil the physics of relativistic transients. I will also highlight opportunities and challenges that lie in front of us, as improvements in detectors’ sensitivities will transform a trickle of multi-messenger discoveries into a flood.

Modelling the molecular gas that is detected through CO observations of high-z galaxies constitutes a major challenge for ab initio simulations of galaxy formation. I will present recent numerical work aimed at studying the formation and evolution of the simplest and most abundant molecule, H2. Our model fully solves the out-of-equilibrium rate equations and accounts for the unresolved structure of molecular clouds. We apply our model to two types of cosmological simulations: a) the formation of a Milky Way-sized galaxy at z=2 and b) a small cosmological box in order to obtain some statistical results. The results are compared to those obtained from two different approximations commonly used in the literature and for numerical convergence. Our results indicate that independently of the model, robust results (H2 masses) can only be obtained for galaxies that are suffiiciently metal enriched in which H2 formation is fast. However, their morphology differ from model to model. Furthermore, the cosmological H2 mass function derived from the non-equilibrium model agrees well with recents observations that only sample the high-mass end. Extensions of our model towards including other molecules, such as CO, and species, in particular C and its derivatives, will also be discussed.

Abstract: I will review recent observations and theoretical estimates of the spatial extent of galaxies, defined as systems of stars and gas embedded in extended halos of dark matter and hot gas. Formed by the infall of smaller systems, their sizes are determined by gravitational assembly, gas dynamics, and chemical enrichment in heavy elements blown into extragalactic space by galactic winds. But the full extent of galaxies remains poorly determined. The “virial radius” and “splash-back radius” approximate the separation between collapsed structures and infalling matter. Other measurements include X-ray emission and ultraviolet absorption lines from metal-enriched gas in galactic halos. Astronomers have identified large reservoirs of baryonic matter in the circumgalactic medium (CGM) and intergalactic medium (IGM) that contain 50-70% of the cosmological baryons formed in the Big Bang. Investigations of physical processes at the “edge of galaxies” help define the importance of this gas in sustaining the star formation in galaxies.

The HI-MaNGA survey is an HI (21cm line) follow-up program for the SDSS-IV MaNGA survey.  I will describe the HI-MaNGA survey, its progress to date, and future plans.  I will then present new results where we combine HI-MaNGA and MaNGA data to investigate how the global HI content of star-forming galaxies relates to the mean properties of their ISM derived from optical emission lines, including integrated equivalent width, metallicity, ionization parameter, and the relative strength of low-ionization lines such as [SII] and [OI]. This analysis allows us to understand if and how the properties of the ISM vary between the most gas-rich galaxies to the most gas-poor, and how such variations may affect their evolution.  I will also discuss how gas content relates to the nuclear ionizing source (e.g., Seyfert, LINER, HII regions) and whether we find any evidence that AGN contribute to gas deficiency in the galaxy population.

Zoom Recording: https://uky.zoom.us/rec/share/xGrDewYs7rui5ao4A-_hr_N5r8_c6mkGkiksm--I61WP-hQ8VhJn9HM8fTadgDUG.M9oUhbMc-oa1r2Nr