BEGIN:VCALENDAR VERSION:2.0 PRODID:-//jEvents 2.0 for Joomla//EN CALSCALE:GREGORIAN METHOD:PUBLISH BEGIN:VTIMEZONE TZID:America/Chicago BEGIN:STANDARD DTSTART:20201101T010000 RDATE:20210314T030000 TZOFFSETFROM:-0500 TZOFFSETTO:-0600 TZNAME:America/Chicago CST END:STANDARD BEGIN:STANDARD DTSTART:20211107T010000 RDATE:20220313T030000 TZOFFSETFROM:-0500 TZOFFSETTO:-0600 TZNAME:America/Chicago CST END:STANDARD BEGIN:STANDARD DTSTART:20221106T010000 RDATE:20230312T030000 TZOFFSETFROM:-0500 TZOFFSETTO:-0600 TZNAME:America/Chicago CST END:STANDARD BEGIN:STANDARD DTSTART:20231105T010000 RDATE:20240310T030000 TZOFFSETFROM:-0500 TZOFFSETTO:-0600 TZNAME:America/Chicago CST END:STANDARD BEGIN:STANDARD DTSTART:20241103T010000 RDATE:20250309T030000 TZOFFSETFROM:-0500 TZOFFSETTO:-0600 TZNAME:America/Chicago CST END:STANDARD BEGIN:STANDARD DTSTART:20251102T010000 RDATE:20260308T030000 TZOFFSETFROM:-0500 TZOFFSETTO:-0600 TZNAME:America/Chicago CST END:STANDARD BEGIN:DAYLIGHT DTSTART:20200829T120000 RDATE:20201101T010000 TZOFFSETFROM:-0600 TZOFFSETTO:-0500 TZNAME:America/Chicago CDT END:DAYLIGHT BEGIN:DAYLIGHT DTSTART:20210314T030000 RDATE:20211107T010000 TZOFFSETFROM:-0600 TZOFFSETTO:-0500 TZNAME:America/Chicago CDT END:DAYLIGHT BEGIN:DAYLIGHT DTSTART:20220313T030000 RDATE:20221106T010000 TZOFFSETFROM:-0600 TZOFFSETTO:-0500 TZNAME:America/Chicago CDT END:DAYLIGHT BEGIN:DAYLIGHT DTSTART:20230312T030000 RDATE:20231105T010000 TZOFFSETFROM:-0600 TZOFFSETTO:-0500 TZNAME:America/Chicago CDT END:DAYLIGHT BEGIN:DAYLIGHT DTSTART:20240310T030000 RDATE:20241103T010000 TZOFFSETFROM:-0600 TZOFFSETTO:-0500 TZNAME:America/Chicago CDT END:DAYLIGHT BEGIN:DAYLIGHT DTSTART:20250309T030000 RDATE:20251102T010000 TZOFFSETFROM:-0600 TZOFFSETTO:-0500 TZNAME:America/Chicago CDT END:DAYLIGHT END:VTIMEZONE BEGIN:VEVENT UID:72c6c718e87fa84d879b81bf51f87b14 CATEGORIES:Galaxies and Cosmology Seminar SUMMARY:Galaxies and Cosmology Seminar LOCATION:PMA 15.216B DESCRIPTION;ENCODING=QUOTED-PRINTABLE:
Title: TBA
DTSTAMP:20240328T120449Z DTSTART;TZID=America/Chicago:20210830T120000 DTEND;TZID=America/Chicago:20210830T130000 SEQUENCE:0 RRULE:FREQ=WEEKLY;UNTIL=20211214T000000Z;INTERVAL=1;BYDAY=MO TRANSP:OPAQUE END:VEVENT BEGIN:VEVENT UID:72c6c718e87fa84d879b81bf51f87b14 CATEGORIES:Galaxies and Cosmology Seminar SUMMARY:Alex Riley, Texas A&M University LOCATION:Online DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Dynamics of Milky Way Satellites in the Gaia Era
The release of high-precision astrometric d ata from the Gaia space mission has revolutionized studies of the Milky Way ’s halo substructures over the past few years. I have used this data to mod el the dynamics of Milky Way satellite galaxies, globular clusters, stellar streams, and the stellar halo, often by incorporating comparisons to cosmo logical simulations that include galaxy formation. The Milky Way satellite galaxies have tangentially dominated motions, a kinematic signature consist ent with the central galaxy disrupting radial orbits that pass nearby. Usin g updated catalogs of globular cluster phase-space measurements and new ste llar stream discoveries, I will show that these substructures are not align ed with the Milky Way’s plane of satellite galaxies, suggesting this unusua l orbital configuration in LCDM is not a long-lived structure or the result of a recent accretion event. Additionally, I will show that substructures in simulated stellar halos can produce velocity dipoles along the sky, comp licating recent findings that attribute a similar signal in the Milky Way h alo to the LMC. Finally, I will describe how we can develop simulation and modeling infrastructure to properly leverage observations from upcoming fac ilities in the next generation of Local Group dynamical studies.
Constraining Dark Matter through Gravitational Heating and Cooling P rocesses
Fuzzy Dark Matt er (FDM), consisting of ultralight bosons, is an intriguing alternative to Cold Dark Matter (CDM). Unlike in CDM, FDM halos consist of a central solit onic core, surrounded by an envelope of order unity density fluctuations. T he envelope density fluctuations also interact with the soliton causing it to wobble and oscillate. Using novel, high-resolution numerical simulations of an FDM halo, corresponding to a particular boson mass, I will demonstra te that the gravitational potential fluctuations associated with the solito n's wobble, its oscillations, and the envelope density fluctuations dynamic ally heat nuclear objects (e.g., central star clusters and supermassive bla ck holes) and galaxies. As a result, nuclear objects, initially located at rest at the soliton center, migrate outwards over time until the outward mo tion is counteracted by dynamical friction and an equilibrium is reached. S imilarly, a galaxy undergoes significant size expansion and central density reduction over a Hubble time. Generalizing these results for other halo an d boson masses and comparing them with observations (such as galaxy size-ag e relation, measured offsets of supermassive black holes and nuclear star c lusters from the centers of their host galaxies) will be able to constrain the boson mass. After discussing FDM, I will also briefly present my work o n the peculiar galaxy NGC 1052-DF2 and show what we can learn about its mas s distribution from the dynamical friction-induced orbital decay of its glo bular clusters.
Jackie Champagne, The University of Texas at Austin
Evaluating the Stages of Protocluster Evolution at 2<z<6
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I'll start the talk with a conclusion of my Islands of Reionization project where I used deep Keck/MOSFIRE spectroscopy, alongsid e a rigorous data reduction process to detect Lyα at z=8.661 in the EGS fie ld (Larson et al. 2021 submitted). This new galaxy lies physically close (3 .5 pMpc) to another galaxy with Lyα detected at z=8.684 (Zitrin et al. 2015 ). These two spectroscopic sources and 3 nearby photometric sources might s uggest the presence of the highest-redshift overdensity in the reionization era -- indicating the existence of ≥1Mpc ionized bubbles as early as 500My r after the Big Bang and shedding light on galaxy growth in the early unive rse. Planned follow-up photometric and spectroscopic observations with JWST will further expand upon our ability to quantify the impact these galaxies had on the reionization of the IGM around them.
Forthcoming JWST dat a will be taken over a variety of fields, to different depths and across va rious areas, building up a new era of deep fields. These will be ideal for the discovery and classification of galaxies out to distances previously un charted, potentially as far as z ~ 15. As spectroscopic redshift measuremen ts for sources in this epoch will not be readily available to compare with our first photometric measurements of z > 8 galaxies, we need to establi sh optimal processes now to maximize completeness and minimize contaminatio n rates in our survey data. In preparation for the first wave of observatio ns with JWST, we have produced mock catalogs of photometry based upon the s emi-analytic models from Yung et al. (2019), which mimic expected field dep ths and areas of 4 upcoming JWST deep surveys: NGDEEP (m~30.6, 6 arcmin2), PRIMER DEEP (m~29.5, 33 arcmin2), CEERS (m~28.6, 100 arcmin2), and COSMOS-W eb (m~27.7, 0.6deg2). Typically the selection of high redshift galaxies inv olves spectral energy distribution (SED) fitting to photometric data, an ex pectation for contamination levels, and measurement on sample completeness - all vetted through comparison to spectroscopic redshift measurements of a sub-sample. We have tested a variety of galaxy SED templates and found an appropriate set that matches the colors (β-slope) of our simulated galaxies and performed SED fitting of our simulated sources using the EAZY code (Br ammer et al., 2006). I will show preliminary results highlighting the best practices for selecting galaxies at 6 < z < 15 with JWST, providing a n important road map for observers venturing into this new era of astronomy .
Probing AGN Feedback in Dwarf Galaxies
There is a consensus that feedback processes likely p lay a vital role in the evolution of dwarf galaxies, given their shallow po tential well. While stellar processes have long been considered the primary source of feedback, it is still debated whether such stellar feedback is e ffective enough to reproduce the properties of dwarf galaxies we see today. Given the increasing number of AGN detected in dwarf galaxies, and the ten tative evidence of AGN feedback in them as reported by recent literature, i t is crucial to evaluate the impact of AGN feedback in dwarf galaxies. In t his talk, I will present our studies of the AGN feedback in dwarf galaxies by observing the fast outflows in a sample of nearby dwarf galaxies with AG N through optical integral field spectroscopy and far-ultraviolet spectrosc opy. These outflows are faster than those observed in star-forming galaxies with similar stellar mass and star formation rates. They are mainly photoi onized by the AGN, and a small but non-negligible portion of them may escap e the galaxies. They are primarily AGN-driven and may have an impact on the ir host galaxies similar to those taking place in the more luminous AGN.
Synthesizing Stellar Populations in Massive Galaxy Clusters and High -Redshift Lensed Galaxies
On the other ‘ end’ of the redshift scale, I will share the characterization of COOL J1241 +2219, a lensed galaxy at z = 5.04 that is the brightest galaxy known at z > 5 (zAB ~ 20.5). This galaxy was discovered by COOL-LAMPS — ChicagO Opt ically-selected strong Lenses - Located At the Margins of Public Surveys — initiated to find strongly lensed systems, consisting primarily of a team o f undergraduate students. We characterize the lensed galaxy using ground-ba sed spectrophotometric data to find an intrinsically luminous and massive s tar-forming galaxy. We aim to compare CJ1241 and other COOL-LAMPS discovere d lensed massive galaxies at z>3 with their potential descendents — quie scent massive galaxies at lower redshifts. With anticipated multi-wavelengt h spectroscopic data, including from an approved JWST Cycle 1 Program (GO 2 566, PI: Khullar), we will uncover mass assembly pathways in CJ1241 well in to the epoch of reionization.
Exploring the Properties of the Reionization Sources With Low-Redshi
ft Lyman Continuum
Emitters and High-redshift 21-cm Tomogra
phic Observations
The Ep och of Reionization is a major phase transition in the universe's history, but the nature of the ionizing sources and the physical processes involved are still largely unconstrained. This talk will present the results of rece nt works trying to shed light on these questions. During the first part, I will present the results of recent studies focusing on HI absorption lines and Lyman profiles observed in low-redshift Lyman continuum emitters. These works highlighted that the ISM porosity and dust attenuation are crucial i ngredients regulating the escape of Lyman-alpha and ionizing photons in the se galaxies.
In the second part of this talk, I will talk about how f uture 21-cm tomographic observations obtained with the Square Kilometer Arr ay will be crucial to constrain the properties of the ionizing sources. In particular, I will show how the morphological properties of the ionized reg ions trace the astrophysics of reionization and can be incorporated in a Ba yesian inference framework to disentangle multiple reionization scenarios.< /p>
Internal structures of HII regions: Photoionized Herbig-Haro objects
Based on high-resolutio n UVES @ VLT spectroscopy and 20 years of HST imaging, we study the interna l interactions of Orion Nebula gas with photoionized Herbig-Haro (HH) objec ts. Our works reveal that the multiple internal gas interactions that take place within the Orion Nebula have an important role in the density structu re of the nebula, changing dramatically the local ionization state of the g as. These interactions must be present in an unknown proportion in more dis tant Galactic and extragalactic star forming regions, where the existence o f young stellar objects ensures the presence of protostellar jets such as t he HHs. The consideration of this more realistic image of the star forming regions, different from assuming that they are homogeneous environments, ca n change the assumptions we make on their physical conditions to derive the ir chemical composition. We will focus on HH529II, HH529III, HH204 and HH51 4. These objects are located at different distances from the main ionizatio n source of the Orion Nebula, with different ionization / physical conditio ns and flow velocities. In all HH objects, we find direct evidence of dust destruction, that increases the gaseous abundances of Fe, Ni and Cr, which magnitude seems to be correlated with the flow velocity. By combining the e mission of the HH objects and the Orion Nebula we simulate low-resolution s pectra with high-density inclusions, finding that some of the classical dia gnostics --such as [SII] I(6716)/I(6731)-- underestimate the true density, overestimating the temperature, which can result in erroneous chemical abun dance determinations.
Reionizing the Clumpy Intergalactic Medium
Reionization is an epic event when lumi nous sources ionized the neutral universe. The upcoming observations will r eveal reionization in unprecedented detail, including its sources and geome try. However, the progress of reionization depended also on the sinks of io nizing photons: dense gas in the intergalactic medium (IGM) absorbs more ph otons due to fast recombination. Recent observations and simulations show t he rapid evolution of the clumpy IGM during reionization. I will present my new, adaptive, and efficient radiative transfer method, SPH-M1RT. With thi s method, we simulate the complex interplay between the clumpy IGM and reio nization. Finally, I will discuss the applications of SPH-M1RT in galaxy si mulations, especially reionization of the local universe.
Emission Line Galaxies and Star Formation in FIGS and HALO7D
Studying the processe s that influence and regulate star formation is critical to understanding t he growth and development of galaxies. Low-mass galaxies may be sensitive p robes of these processes, but their faintness makes studying them difficult at higher redshift. Deep grism spectroscopy offers a way to do this throug h accurate redshift measurement and estimates of galaxy star formation thro ugh the detection of emission lines. In the Faint Infrared Grism Survey (FI GS), we identify 24 candidate galaxy overdensities and 208 Emission Line Ga laxies (ELGs) with 0 < z < 2.0 in low-resolution 1D spectra obtained using Hubble’s WFC3/G102 grism. The ELGs have measured line fluxes down to 10^-17 ergs/cm2/s and continuum magnitudes down to AB(F105W) < 28. We id entify Hα6563, [OIII]5007, and [OII]3727 Å strong line emitters, from which we estimate star formation rates and gas-phase metallicities. We observe a correlation between specific star formation rate and low gas-phase metalli city, and find little evidence that a galaxy’s line emission relates closel y to overdensity. In the HALO7D survey, we describe ongoing work using Keck /DEIMOS spectroscopy of low-mass galaxies to characterize their metallicity , star formation burstiness, and other properties.
Exploring the Cold Universe: From Obscured Active Galactic Nuclei, I nterstellar to Circumgalactic Media at z~5-7
The cosmic infrared background light is know n to have energy comparable to the optical one, suggesting the importance o f infrared observations to understand the other aspect of the universe obsc ured by cold materials. In this seminar, I will present our latest research on the formation and evolution of galaxies at z~5-7 in a wide range of sca les, including active galactic nuclei (<100 pc), interstellar (ISM; ~100 pc to 5 kpc), and circumgalactic media (CGM; ~5-20 kpc), based on the late st (sub)millimeter observations with ALMA and NOEMA. I will discuss what is taking place in the cold side of the early universe, highlighting three re cent discoveries: i) the CGM-scale [CII]158um gas halo, ii) the difference between the 3D structure of neutral and ionized gases in the ISM, and iii) the young quasar forming in a dust-enshrouded starburst.
Solving Reionization with Resolved Lyman-alpha
The most pressing questions around Reionization -- e.g., whether its protagonists were a handful of bright gal axies (``the oligarchs") or numerous ultra-faint sources (``democratic reio nization") -- hinge on the unknown ionizing photon escape fractions (LyC fe sc) of star-forming galaxies. Efforts to understand the physics and statist ics of LyC fesc have been stymied by our inability to construct pure sample s of LyC leakers vs. non-leakers with generalizable selection functions. I will argue high-resolution Lyman-alpha (LyA) spectroscopy is the panacea to these issues. Using the X-SHOOTER LyA survey at z~2 (XLSz2) I will present clean stacks of leakers vs. non-leakers that show dramatic differences acr oss ~1000-8000A -- these differences clarify how/why ionizing photons escap e and identify the features that can be studied at z>6 to constrain fesc (e.g., MgII, O32, HeII). The leakers constitute half our survey, and have escape fractions ~50%. Building on these results, I will present a LyA-base d framework for the ionizing emissivity from z~2-8 that both explains the p uzzling flatness of the emissivity at z~2-6 as well as rapid reionization b etween z~6-8. I will end by previewing two Cycle 1 JWST programs I am leadi ng -- these programs examine ionized bubbles towards the beginning and end of reionization, and will produce some of the deepest grism pointings in Cy cle 1 to enable a variety of z~1-9 science.
The Role of Dense Circumgalactic Gas in Shaping Galaxies
< !-- START: Sliders -->The circumgalactic medium (CGM) houses large-scale gaseous flows as well as a reservoir of material that can be used for future star formation. For galaxies to continue formin g stars, they must accrete material that passes through the CGM in the form of inflows (recycling material or gas from the intergalactic medium, IGM) while also contending with outflows (winds escaping the galaxy disk). Here I present two projects that study the CGM of galaxies at z < 1, investig ating whether the CGM properties correlate with the galaxy properties using absorbers known as partial Lyman limit systems (pLLSs) and Lyman limit sys tems (LLSs) with 16.0 ”Ü logNHI < 19.0 [cm-2]. Using a sample of blindly -selected pLLSs that span a broad range (0.1ØC54% solar) in metallicity, I utilize IFU observations to identify and characterize the host galaxies of these absorbers to determine the types of environments that house absorbers of different metallicities. In my second project, I observationally test m odel predictions for cold-mode and hot-mode accretion into galaxy halos by determining the cool HI gas content in the halos of luminous red galaxies ( LRGs, logM”ļ > 11 M”Ń) at z ~ 0.5 and the metallicity of the absorbers w e detect. My findings show the CGM metallicity does not correlate with most of the host galaxy properties, with the exception of stellar mass. There i s no mass where we do not find cool gas in the inner CGM of galaxy halos, a nd low-metallicity absorbers are found in halos of all masses. However, the majority of these low-metallicity absorbers are most likely associated wit h filaments instead of galaxy halos at z < 1. With these two surveys, we see that to understand the interplay between the CGM and the galaxy, obser vations of both are necessary.
Joohyun Lee, The University of Texas at Austin
Dark Matter Deficient Galaxies and Their Member Star Clusters Form Simulta
neously during High-velocity Galaxy Collisions in 1.25 pc Resolution Simula
tions
How diffuse dwarf galaxies that are deficie nt in dark matter—such as NGC1052-DF2 and NGC1052-DF4—formed remains a myst ery. Along with their luminous member globular clusters (GCs), the so-calle d dark matter deficient galaxies (DMDGs) have challenged observers and theo rists alike. Here we report a suite of galaxy collision simulations using t he adaptive mesh refinement code ENZO with 1.25 pc resolution, which demons trates that high-velocity galaxy collisions induce the formation of DMDGs a nd their star clusters (SCs) simultaneously. With a numerical resolution th at is significantly better than our previous study, we resolve the dynamica l structure of the produced DMDGs and the detailed formation history of the ir SCs, which are possible progenitors of the DMDG’s member GCs. In particu lar, we show that a galaxy collision with a high relative velocity of ∼300 km/s, invoking severe shock compression, spawns multiple massive SCs (Mstar < 10^6 Msun) in < 150 Myr after the collision. At the end of the ∼80 0 Myr evolution in our fiducial run, the resulting DMDG of Mstar ~ 3.5×10^8 Msun hosts 10 luminous Mv < −8.5 mag, gravitationally bound SCs with a line-of-sight velocity dispersion 11.2 km/s. Our study suggests that DMDGs and their luminous member SCs could form simultaneously in high-velocity ga laxy collisions while being in line with the key observed properties of NGC 1052-DF2 and NGC1052-DF4.
Grace Olivier, The Ohio State University
Evolution of Stellar Feedback from Reionization to The Milky Way: A Divers
e Toolset of Imaging, Spectroscopy, and Modelling for Understanding the Imp
act of Massive Stars
Massive stars contribute incredible amounts of energy to their surro undings across a variety of environments in the universe. Before their exci ting deaths, massive stars produce feedback through a number of mechanisms that are frequently used in subgrid physics models in galaxy simulations to create realistic galaxies. Observations are a key to anchoring these simul ations in reality, but there has been limited work on this front, especiall y for the youngest, embedded HII regions. I explore the effects of direct r adiation pressure, dust-processed radiation pressure, photoionization heati ng and shock-heating from stellar winds in a sample of young HII regions (s ources with radii < 0.5 pc) and determine which is the most important fo r very young stars. This analysis suggests radiative feedback on dust drive s the earliest stages of HII region expansion. Additionally, I study the ef fects of radiative feedback in an exciting population of extremely low-meta llicity star-forming galaxies that have been discovered in the local univer se which are analogues to Reionization Era galaxies. During the Epoch of Re ionization radiative feedback played a significant role in shaping the univ erse, and such analogues give us a detailed laboratory to explore the effec ts from feedback. I present deep FUV and optical spectra of two of these ex treme emission line galaxies that have strong very-high-ionization optical and FUV emission lines (e.g., CIV, HeII, [FeV], [ArIV]). I demonstrate that canonical photoionization models, using typical stellar population models, catastrophically fail to reproduce the high-ionization emission lines. I c onstrain the stellar population properties using the FUV spectral features and explore the deficiencies of current stellar models. By simultaneously f itting the stellar and nebular emission within these extremely high-ionizat ion emission line galaxies, I provide new observational benchmarks of radia tive feedback for the next generation of stellar models at very low metalli city. By studying the effects of stellar feedback from single stars in the Milky Way to entire stellar populations in analogues to the first galaxies we can begin to build a coherent picture of stellar feedback as it impacts the vast scales of the universe.
Labor Day - no talk scheduled
DTSTAMP:20240328T120449Z DTSTART;TZID=America/Chicago:20210906T120000 DTEND;TZID=America/Chicago:20210906T130000 RECURRENCE-ID;TZID=America/Chicago:20210906T120000 SEQUENCE:0 TRANSP:OPAQUE END:VEVENT BEGIN:VEVENT UID:72c6c718e87fa84d879b81bf51f87b14 CATEGORIES:Galaxies and Cosmology Seminar SUMMARY:Galaxies and Cosmology Seminar LOCATION:Online DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Organizational meeting
DTSTAMP:20240328T120449Z DTSTART;TZID=America/Chicago:20210830T120000 DTEND;TZID=America/Chicago:20210830T130000 RECURRENCE-ID;TZID=America/Chicago:20210830T120000 SEQUENCE:0 TRANSP:OPAQUE END:VEVENT BEGIN:VEVENT UID:72c6c718e87fa84d879b81bf51f87b14 CATEGORIES:Galaxies and Cosmology Seminar SUMMARY:Galaxies and Cosmology Seminar LOCATION:Online DESCRIPTION;ENCODING=QUOTED-PRINTABLE:Galaxies and Cosmology Seminar
DTSTAMP:20240328T120449Z DTSTART;TZID=America/Chicago:20211213T120000 DTEND;TZID=America/Chicago:20211213T130000 RECURRENCE-ID;TZID=America/Chicago:20211213T120000 SEQUENCE:0 TRANSP:OPAQUE END:VEVENT END:VCALENDAR