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.

Analogy between the Coulomb law of interaction between charges and the Newton law of gravitational attraction between masses is familiar to every physics student.  In this talk I demonstrate that this analogy implies that a system of identical charges can evolve with time in a manner that parallels cosmological evolution of the physical Universe with hallmarks such as Hubble's law and Friedmann-type dynamics present.  The Coulomb and Newton laws are also dissimilar because the electrostatic force is many orders of magnitude larger than the gravitational force whose manifestations are only noticeable on astronomical scale.  On the other hand, analog cosmological evolutions driven by Coulomb interactions are predicted to be observable in laboratory experiments involving Coulomb explosions and electron density oscillations in conductors.

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.

Elements condensing into dust grains is an important physical process that occurs in the ISM. Through studies on extinction, scattering, heating and depletion of elements out of gas-phase, it has long been known that grains have a major effect on observed spectra of galaxies. Despite the large amount of observations available on extinction, scatter and heating, details of depletions onto grains and their effect on observed emission-line spectra are rarely studied. We explore the effects of grain depletions on strong spectral lines, and find non-trivial results. Our results suggest that the level of depletion, not only affects the emission line strength of corresponding ions, but also changes the abundance of coolants in the ISM gas, hence affecting its temperature. In addition, we include new code into Cloudy, allowing a user to alter the degree of grain depletions in a given model.

Elements condensing into dust grains is an important physical process that occurs in the ISM. Through studies on extinction, scattering, heating and depletion of elements out of gas-phase, it has long been known that grains have a major effect on observed spectra of galaxies. Despite the large amount of observations available on extinction, scatter and heating, details of depletions onto grains and their effect on observed emission-line spectra are rarely studied. We explore the effects of grain depletions on strong spectral lines, and find non-trivial results. Our results suggest that the level of depletion, not only affects the emission line strength of corresponding ions, but also changes the abundance of coolants in the ISM gas, hence affecting its temperature. In addition, we include new code into Cloudy, allowing a user to alter the degree of grain depletions in a given model.

The environment in which a galaxy lives plays a key role in driving its evolution.  As the most tenuously bound component of galaxies, neutral atomic hydrogen (HI) is a valuable tracer of both the interaction history of a galaxy with its environment and a measure of its future star formation potential.  As galaxies move from the low-density field to high-density clusters, they lose their gas and star formation is quenched, but how exactly this happens is still poorly understood.  In fact, perhaps most galaxies spend a large fraction of their life in the intermediate-density group environment where the signatures of galaxy evolution are more subtle and widely varied.  In this talk I will present what my work on both wide-area HI surveys and individual observations have revealed about galaxy evolution, from the low mass group environment to the outskirts of massive galaxy clusters.  Statistical studies of the HI provide insight on not only the gas processing and ongoing evolution within galaxy groups, but also the growth of large-scale structure.  In addition, I'll present the first of the next generation of HI surveys, Apertif, which is observing 3500 square degrees at 14 times the spatial resolution of previous HI surveys and better HI mass sensitivity. Apertif will allows us to resolve and take the inventory, for the first time, of the physical mechanisms that remove gas from galaxies, across the full range of galaxy environments from poor groups to galaxy clusters.

Zoom Recording: https://uky.zoom.us/rec/share/HyMikMEOik6ZtjHliTbYeOx5-W5k-lH5hemITZcVBqec-w1Tu3rQOD6biC3qSb38.sPUbAc39PoZWKBwu

The environment in which a galaxy lives plays a key role in driving its evolution.  As the most tenuously bound component of galaxies, neutral atomic hydrogen (HI) is a valuable tracer of both the interaction history of a galaxy with its environment and a measure of its future star formation potential.  As galaxies move from the low-density field to high-density clusters, they lose their gas and star formation is quenched, but how exactly this happens is still poorly understood.  In fact, perhaps most galaxies spend a large fraction of their life in the intermediate-density group environment where the signatures of galaxy evolution are more subtle and widely varied.  In this talk I will present what my work on both wide-area HI surveys and individual observations have revealed about galaxy evolution, from the low mass group environment to the outskirts of massive galaxy clusters.  Statistical studies of the HI provide insight on not only the gas processing and ongoing evolution within galaxy groups, but also the growth of large-scale structure.  In addition, I'll present the first of the next generation of HI surveys, Apertif, which is observing 3500 square degrees at 14 times the spatial resolution of previous HI surveys and better HI mass sensitivity. Apertif will allows us to resolve and take the inventory, for the first time, of the physical mechanisms that remove gas from galaxies, across the full range of galaxy environments from poor groups to galaxy clusters.

Zoom Recording: https://uky.zoom.us/rec/share/HyMikMEOik6ZtjHliTbYeOx5-W5k-lH5hemITZcVBqec-w1Tu3rQOD6biC3qSb38.sPUbAc39PoZWKBwu