Galaxies and Cosmology Seminar

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Galaxies and Cosmology Seminar

Date	Time	Speaker	Title
Monday, March 18, 2024	12:00pm	Ana Matkovic, Penn State University	Fostering Active Learning, Science Identity, and Sense of Belonging: Evidence Based Teaching Strategies for You Abstract Abstract The recent study spanning two decades of students in STEM (Seymour and Hunter, 2019) identified that the most important factors of why students leave STEM majors relate to course structure and poor teaching, and lack of a sense of belonging in the field. Building upon my experience in teaching astronomy to both STEM and non-STEM undergraduates for over a decade, my involvement in Center for Excellence in Science Education at Penn State, and as a instructor and facilitator at the yearly Evidence Based Teaching Academy at Penn State, and the scholar at Penn State’s Equity Pedagogy Network, I will discuss teaching strategies that we can use to affect positive change in these numbers. After briefly reviewing teaching strategies based on meta analysis of 80 Million students (Hattie 2009) I will give examples on using backward design and active learning in Astronomy courses, and how to avoid the ‘coverage trap’ that most STEM instructors fall into. I will also include the more modern approach to student motivation which is tied to the sense of belonging in science and to student Astronomy or Physics identity and how to achieve increased student astronomy identity and a sense of belonging in the major. Finally, I will discuss how sustainability, and projects driven by such goals that connect and address socio-scientific issues (e.g. understanding light pollution and dark skies) can provide meaningful engagement and deepen both conceptual understanding and the sense of belonging for all students.
Monday, March 25, 2024	12:00pm	Graduate Student Recruiting	No talk scheduled
Monday, April 01, 2024	12:00pm	Two Talks	Oscar A. Chavez Ortiz, The University of Texas at Austin The Lyman-Alpha Dependence on Nebular Properties from the HETDEX and MOSDEF Surveys Abstract Abstract Investigating the impact of galaxy properties on emergent Lyman-alpha emission is a crucial aspect of reionization studies, given the sensitivity of Lyman-alpha to neutral hydrogen. This study presents an analysis of the physical characteristics of 155 star-forming galaxies, 29 w/ Lyman-alpha detected, and 126 w/ Lyman-alpha not detected w/ EW < 20 Angstroms, at z = 1.9 -- 3.5, drawn from the MOSFIRE Deep Evolution Field (MOSDEF) survey that have overlapping observations from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) survey. To unravel the interstellar medium (ISM) conditions in our sample, we developed a custom nebular line diagnostic algorithm based on the MAPPINGS V photoionization model grid and the emcee framework. Combining nebular-based ISM properties with photometry-based global properties, constrained via Bagpipes, we explore distinctions in the stellar and gas properties between Lyman-alpha detected and Lyman-alpha non-detected galaxies. Our analysis reveals statistically significant differences between the two samples in terms of stellar mass and dust attenuation at > 2 sigma significance, as determined via a Kolmogorov-Smirnov (KS) test. Moreover, there are weaker (< 1 sigma significance) indications that the ionization parameter and metallicity exhibit differences between the two samples. Our results also demonstrate that the escape fraction of Lyman-alpha is inversely correlated with stellar mass, SFR, and dust attenuation, while positively correlated with the ionization parameter, with significance levels exceeding 2 sigma. Our findings suggest that the interstellar environment of the Lyman-alpha detected galaxies, characterized by low mass, low dust, low gas-phase metallicity, and high ionization parameters, play a pivotal role in promoting the escape of Lyman-alpha radiation. Hyunsu Kong, The University of Texas at Austin Testing Lambda-CDM with Dark Matter Subhalos Abstract Abstract The number of dark matter subhalos, as a function of mass and their distance from their host, can be crucial discriminators among dark matter models. The Milky Way exhibits a significantly uncertain distribution of satellite galaxies concerning both mass and radial distance, underscoring the importance of understanding dark matter substructures. While numerical simulations are key for quantifying these subhalos, there is a growing concern regarding the suitability of standard tools, namely halo finders and merger trees, used to identify and track subhalos in simulations, particularly for low-mass subhalos orbiting deep within the potential of the host halo. To address this challenge, I have developed and rigorously tested a subhalo tracking package named Bloodhound, optimized for accurately tracking subhalos even in the densest regions of the host halo. In this talk, I will present Bloodhound's contributions to refining statistical properties of dark matter subhalos in Phat ELVIS cosmological simulations. These new predictions will be directly compared with observations of the Milky Way’s dwarf satellite galaxies from the JWST and the forthcoming Vera Rubin Observatory, potentially offering the most rigorous test of the Lambda-CDM cosmological paradigm to date. Alignment between predicted subhalo counts and observed satellite galaxies would provide a powerful confirmation for Lambda-CDM. Conversely, any discrepancies may prompt a reassessment and exploration of alternative models, such as self-interacting dark matter.
Monday, April 08, 2024	12:00pm	Total Solar Eclipse	No talk scheduled
Monday, April 15, 2024	12:00pm	Om Gupta, The University of Texas at Austin	Second Year Research Talk Constraining the Cosmic Evolution of Fast Radio Bursts Abstract Abstract Fast Radio Bursts (FRBs) are a unique high-energy astrophysical phenomenon that are produced in extreme environments. Since their discovery in 2007, thousands have been detected, with most of them being extragalactic, while one repeating source resides in the Milky Way. Recent and proposed work establishes them as useful probes of cosmology and galaxy evolution processes at high redshift, but these often require large number statistics. I will discuss that this necessitates the assessment of how many FRBs are actually observable over the full sky, as well as how they evolve with redshift. Their evolution with redshift is also determined by their progenitor formation channels, which can either track star formation rate, or the stellar mass density. I will first discuss how we constrain the cosmic evolution of the star formation rate density, especially at high redshifts with published JWST results. Then I will talk about constraining the FRB luminosity (energy) function as well their tentative spectrum, which is somewhat analogous to how redshift evolution of galaxies is determined. All of these components give us a theoretical model of FRB source count evolution with redshift, which needs to be converted to a quantity called the Dispersion Measure (DM), which gives the column density of free electrons, and is also an FRB observable. I will talk about this conversion using Monte Carlo sampling of estimated DMs contributed by the IGM and FRB host galaxies, to build a theoretical FRB DM distribution which is matched with the observed DM distribution from the CHIME radio telescope’s FRB catalog. Finally, I will discuss some correlations in the model parameters that leave them unconstrained, and the possibility of resolving them with fluence data from the new CHIME baseband catalog. Once resolved, the luminosity function can inform FRB physics providing constraints to the energy emission limits, and the redshift evolution can maybe resolve the progenitor formation channel debate.
Monday, April 22, 2024	12:00pm	Two talks	Katherine Chworowsky, The University of Texas at Austin Title: TBA Alexa Morales, The University of Texas at Austin Title: TBA
Monday, April 29, 2024	12:00pm	Two Talks	Maria Straight, The University of Texas at Austin Title: TBA Kay Guo, The University of Texas at Austin Title: TBA