Talks

I will present an overview of the work of the "GM Galaxies" project, which explores the relationship between history of a galaxy and its observable traits. I will give three examples of our work, looking at how dwarf galaxies change their properties based on their mass assembly, the Milky Way stellar halo responds to variations in its merging history, and the circumgalactic medium of massive galaxies mediates the transition from star-forming to quiescent.

Line Intensity Mapping (LIM) experiments are innovative techniques for studying structures at high redshift. They allow us to uncover previously inaccessible astrophysical data by making 3D tomographic maps with 2D spatial line intensity fluctuations. As efforts like COMAP progress in detecting carbon monoxide (CO) and other spectral lines, generating precise mock maps becomes crucial for data analysis, prediction of future observations, and development of new statistical methods for LIM analysis. These mock maps are generated by interpolating line luminosities across the specified dark matter halo distribution, using response functions that are defined by the relationship between the line luminosities and both observable and derived properties of simulated galaxies. In my presentation, I will elucidate the statistical relationship between the calculated line luminosity and inherent/derived observables for simulated FIRE (Feedback In Realistic Environment) galaxies, focusing on CO(1-0) to CO(8-7) lines at four different redshift regimes: z=0, 1, 2, and 3. I will examine the correlations between CO emission and galactic properties at different redshifts and explore the potential causal relationships they may suggest as well as how they can define essential response functions for creating mock maps.

The CGM is sensitive to various baryonic flows (e.g. stellar winds, supernovae, etc.) occurring on different timescales. Chemical abundance patterns in circumgalactic clouds provide a unique timing clock for constraining the dominant source of feedback regulating galaxy growth. In this talk, I will discuss how we leverage multiwavelength quasar spectra from surveys like the Cosmic Ultraviolet Baryon Survey (CUBS) to constrain the gas ionization state and elemental abundances of cool/warm-hot CGM absorbers. We find relatively cool (~1-5e4 K), diffuse (~0.001-0.01 cm^-3) photoionized gas clumps exhibiting a variety of chemical enrichment patterns. Several absorbers show an enhancement in non-alpha elements (e.g. carbon, nitrogen) reflecting metal production by secondary nucleosynthetic pathways. We also find chemically mature, metal-poor absorbers, showing evidence of mixing between pre-enriched gas and pristine inflows. These results demonstrate the value of using elemental abundances to understand which feedback processes are most critical in shaping the cosmic baryon cycle.

Using zoom-in cosmological simulations, I will discuss some of the physical and observable properties of the circumgalactic medium (CGM). I will focus on non-thermal physical processes and how they impact the galactic ecosystem. The presence of magnetic fields and feedback from relativistic cosmic rays changes the flow of gas in the CGM, affecting the efficiency of outflows driven by stars or supermassive black holes as well as the turbulence-driven mixing in the CGM. This also affects our simulations’ predictions for neutral hydrogen and metal ions, observable through 21 cm emission and quasar absorption lines. I will show how these effects of magnetic fields and cosmic rays vary across a wide range in halo mass, from dwarf galaxies to galaxy groups.

Project AMIGA (Absorption Maps In the Gas of Andromeda) provides an unprecedented view of the circumgalactic medium (CGM) of our nearest large galaxy neighbor. Using 55 sightlines obtained largely from two large HST COS programs, we map Andromeda's CGM across distances spanning from 10 to 570 kpc, nearly reaching twice its virial radius (Rvir=300 kpc). Using extensive diagnostics of different gas phases (OI/VI, SiII/III/IV, CII/CIV, FeII, AlII), this study uniquely bridges the smaller scales of the CGM with its largest scales extending into the intergalactic medium (IGM). In this talk, I will demonstrate how gas complexity and gas-phase structures significantly change with impact parameters but show little variation with azimuth relative to major/minor projected axes. Our program can differentiate components associated with the thick disk from those in the CGM, providing crucial insights for characterizing gas phases and accurately determining the total mass of Andromeda's CGM. I will place these findings in the broader context of other CGM observations, recent cosmological zoom simulations of Milky Way-mass galaxies at z~0, and how this pathfinder study may inform next-generation observations of the CGM/IGM with HWO.

We report results from observations of the CGM ionized, atomic, molecular, and condensed phases using a combination of integral field spectroscopy (MaNGA, VLT MUSE, JWST MRS), and imaging and spectroscopy from HST, VLT, Magellan. In a study of the warm and cool CGM of galaxies mapped with IFS, and a comparison of the kinematics, ionization, and metallicity of this gas with the ionized gas in star-forming regions in the galaxies, we find consistency with a co-rotation of the cool CGM with galaxy disks and hints of changes in gas ionization, potentially due to the stronger intergalactic radiation field at larger galactocentric distance. Our spatially resolved maps of gas metallicity and ionization around galaxies provide constraints on models of the metal distribution around galaxies. Our results are also consistent with higher metallicity and higher ionization parameter for gas at higher elevation angles, as expected for outflows. Our JWST studies of the composition, structure, and extinction properties of the dust grains in both the diffuse and dense ISM/CGM of galaxies at 0

Simulations with fixed spatial resolution are an excellent tool to investigate the interplay between different phases of gas in and around galaxies because they mitigate the disparity in cell sizes due to density variations in traditional mass-based refinement schemes. Additionally, the moving-mesh technique implemented in Arepo has been shown to minimize numerical mixing and instability suppression. In this talk, I will introduce a new suite of cosmological zoom simulations with 200 pc resolution covering the inner CGM of a Milky Way-mass galaxy, utilizing the full IllustrisTNG galaxy formation model. At this high resolution, we find increased turbulent velocities, many small, cool cloudlets, and a smooth and homogeneous hot phase. I will outline these results and discuss the implications for high- and intermediate-velocity cloud studies and gas mixing in the CGM.

Despite its vast extent—spanning hundreds of kiloparsecs beyond the galactic disk—the circumgalactic medium (CGM) is shaped by microphysical processes operating on much smaller scales. One key example is the coupling between cosmic rays and gas. Under the right conditions, cosmic rays can dominate the pressure support in the CGM of low-redshift L* galaxies. However, this coupling depends sensitively on AU-scale magnetic field fluctuations—well below the resolution limit of modern galaxy-scale simulations. In this talk, I will highlight recent theoretical developments in cosmic-ray transport and their implications for CGM pressure profiles. I’ll also introduce CGSM, a new subgrid model designed to represent unresolved cold gas structures in hydrodynamic simulations, and discuss its potential to bridge the gap between microphysics and galaxy evolution.

The circumgalactic/intergalactic medium (CGM/IGM) represents a significant baryon reservoir for sustaining star formation and provides insights into the inflows, outflows, and feedback history of galaxies.  Star-forming dwarf galaxies, with their shallow potential wells, are predicted to drive metal-enriched gas into the CGM/IGM. Therefore, a census of the CGM around dwarf galaxies can provide insights into the stellar feedback. We present highly sensitive absorption-line measurements in quasar sightlines adjacent to 91 isolated dwarf galaxies with a median stellar mass of M_star/M_sun≈8.4 from the Cosmic Ultraviolet Baryon Survey (CUBS). This survey uses HST absorption spectroscopy to access a range of ion transitions from 0.077