Galaxies and Cosmology Seminar

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Galaxies and Cosmology Seminar

Date	Time	Speaker	Title
Monday, August 28, 2023	12:00pm	Annalisa Citro, University of Minnesota	Investigating the Baryon Cycle Using Galaxy Gas-Phase Properties Abstract Abstract Galaxies are “ecosystems” where energy flows and material cycles are self-regulated in a pattern referred to as “baryon cycle”. When inflows of gas trigger star formation, ionizing radiation is emitted into the interstellar medium (ISM) and Supernovae II feedback also releases chemical elements into the ISM. These processes modify the composition and structure of the ISM and can lead to the escape of ionizing radiation and Lyman alpha photons. In this talk, I will investigate two specific aspects of the baryon cycle. I will show the value of chemical abundances and in particular of the carbon/oxygen abundance to trace the early stages of the galaxy star formation histories.I will also discuss the connection between the structure of the ISM, LyC escape fraction and the Lya emission. I will present new analytical models that describe how the Lyman alpha equivalent width varies as a function of the ISM structure and content.
Monday, September 04, 2023	12:00pm	Labor Day - UT Closed	No talk scheduled
Monday, September 11, 2023	12:00pm	Jordan Flitter, Ben Gurion University	Searching for Dark Matter Signatures in the 21cm Signal Abstract Abstract The 21cm signal is a promising observable that has the potential to probe uncharted regions of our Universe, thereby presenting an opportunity to challenge the standard model and perhaps discover new physics. In this talk I will discuss how we can exploit the spatial fluctuations in the signal to study exotic models of dark matter. I will focus on two popular dark matter candidates, fuzzy dark matter (FDM) and scattering dark matter (SDM). Despite the high uncertainty in the astrophysics that control the signal, our analysis shows that 21cm interferometers, such as HERA, will be sensitive enough to probe FDM and SDM in regions in the parameter space that haven’t been ruled out by other observations. With the new cosmological tool we have developed, 21cmFirstCLASS, a merger of the well known codes 21cmFAST and CLASS, I will demonstrate how a joint analysis of 21cm and CMB can relax degeneracies between the cosmological parameters and improve their constraints considerably.
Monday, September 18, 2023	12:00pm	Yechi Zhang, The University of Tokyo	Understanding galaxy outflows at z~6-9 through JWST NIRCam and NIRSpec Abstract Abstract In this talk I will present the statistics of z~6-9 galaxy outflows indicated by spatially-extended gas emission and broad lines in the JWST NIRCam imaging and NIRSpec spectroscopy respectively. With a total of 61 spectroscopically confirmed galaxies at z~6-9 in the JWST CEERS, GLASS, and ERO data, we find five galaxies with [Oiii]+Hb ionized gas emission significantly extended beyond the kpc-scale stellar components based on the emission line images constructed by the subtraction of NIRCam broadband (line on/off-band) images. The number fraction of galaxies with the spatially extended gas, 5/32, at z~6-9 is an order of magnitude higher than those at z~0-1, which can be explained by events triggered by frequent major mergers at high redshift. We also investigate medium- and high-resolution NIRSpec spectra of 30 galaxies at z~6-9, and identify five galaxies with broad (140-800 km/s) lines in the [Oiii] forbidden line emission, suggestive of ongoing galaxy outflows. All of the galaxies with broad lines have outflow velocities smaller than the escape velocities of their dark matter halos, indicating that outflows in these galaxies cannot eject hot ionized gas into IGM. The existence of galaxies with/without spatially-extended gas emission or broad lines may suggest that these are galaxies in the early, late, post phases of galaxy outflows at high redshift, where the relatively large fractions of such galaxies indicate the longer-duration and/or more-frequent outflows at the early cosmic epoch.
Monday, September 25, 2023	12:00pm	Two Talks	Peter Senchyna, Carnegie Observatories TItle: TBA Mahdi Qezlou, University of Califormia Riverside Cosmology and Galaxy Evolution with Ly-alpha Tomography Abstract Abstract Ly-alpha tomography surveys have produced 3D maps of the Lya opacity of the intergalactic medium (IGM) at z ~ 2.5 with Mpc resolution, offering a new window to discover high-redshift large-scale structures like the progenitors of present-day massive galaxy groups and clusters. This presentation explores the complementarity of Ly-alpha tomography with conventional galaxy surveys. In the largest IGM map to date, the Lyman-α Tomographic IMACS Survey (LATIS), we detect both previously known galaxy protoclusters and a novel population that was missed by galaxy spectroscopic surveys. I also present our independent constraints on the stellar vs. halo mass relation from LATIS tomography. Additionally, I'll discuss our recent work demonstrating synergies between these tomographic maps and the upcoming line intensity map (LIM) experiments at cosmic noon. This cross-correlation allows one to detect emission from the faintest galaxies, enabling unbiased cosmological and galaxy evolution studies. Throughout the presentation, I will share our progress to date and the promising prospects for the future, covering both the modeling of these new mapping techniques using the largest cosmological hydrodynamic simulations, which is required to fully realize the potential of these techniques, alongside the latest observations in this emerging field.
Monday, October 02, 2023	12:00pm	Two Talks	Owen Chase, The University of Texas at Austin Title: TBA Macarena G. del Valle-Espinosa, University of Edinburgh Title: TBA
Monday, October 09, 2023	12:00pm	Indigenous Peoples Day	No talk scheduled
Monday, October 16, 2023	12:00pm	Two Talks	Kim Boddy, The University of Texas at Austin Title: TBA Maya Debski, The University of Texas at Austin Title: TBA
Monday, October 23, 2023	12:00pm	Changhoon Hahn, Princeton University	Title TBA
Monday, October 30, 2023	12:00pm	BashFest Symposium	No talk scheduled

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