FLASH Talks: Jed McKinney (UT Austin) & Kaixiang Wang (KIAA - PKU)

Friday, 03 March 2023 noon — 1 p.m. MST

NOIRLab Headquarters | 950 North Cherry Ave., Tucson, AZ 85719

Jed McKinney (UT Austin) & Kaixiang Wang (KIAA - PKU)

Jed McKinney, UT Austin
Into the Dusty Universe: massive dust-obscured galaxies in the COSMOS-Web survey
Most of star-formation over cosmic time is obscured by dust. However, orders-of-magnitude uncertainty on the prevalence of dusty star-forming galaxies at z>4 make it difficult to quantify the role played by dust during cosmic dawn. In this talk I will present early results (some never-before-seen) on the optical/near-IR counterparts found for high-redshift and far-infrared bright galaxies within the COSMOS-Web survey. COSMOS-Web is the largest Cycle 1 JWST GO program, and its wide field coverage makes it ideal for constraining the number densities of rare galaxy populations. Amidst the hunt for dusty galaxies beyond z>5 we run into degeneracies with ultra-high-redshift (z>10) galaxies as well as low mass but unusually dusty objects at 2<z<4. I will highlight what we are learning about dusty galaxies from Cycle 1 JWST programs, and conclude my talk with a brief discussion about mission design requirements a future space-based far-infrared telescope must satisfy to fully unveil the dust-obscured Universe.

Kaixiang Wang, KIAA - Peking University
Revealing the Origins of Ultra-Compact Dwarf Galaxies with Panoramic Deep Imaging
Ultra-compact dwarf galaxies (UCDs) appear to be an intermediate population of stellar systems that bridge the gap between globular clusters (GCs) and classical dwarf elliptical galaxies (dEs) in the size-luminosity plane. The association of some UCDs with supermassive black holes, complex star formation histories, or diffuse stellar envelopes suggest that these UCDs could be the remnant nuclear star clusters of tidally-stripped nucleated dwarf galaxies. Their resemblance, however, to massive star clusters and the possibility that they might also have formed as ancient compact galaxies, have obscured their origins. If UCDs are remnant stellar nuclei, where are those dwarf galaxies that are undergoing tidal disruption? Based on deep CFHT imaging from the Next Generation Virgo Cluster Survey, as well as archival HST data, our detailed structural analysis reveal the existence of faint stellar envelopes surrounding roughly 70 UCDs in the Virgo Cluster, resulting in the largest and most complete sample of UCDs with envelopes (UCD,Es) to date. We also identified a sub-population of dwarf galaxies (dE,Ns) with prominent nuclear star clusters that resemble UCD,Es. In particular, we find significant tidal features around a few dE,Ns that suggest the same origin of these dE,Ns and UCD,Es. They are caught at different stages of the tidal stripping process. In this talk, I will also discuss the implication of our work to the UDG formation, and using UCDs as probes for studying the accretion and mass assembly history in galaxy clusters.