Events Daily

Tuesday, November 14, 2023

Global Categorical Symmetries Workshop
, Simons Collaboration
Event Type: Other
Time: 8:00 AM - 6:00 PM
Location: 726 Broadway, 940, CCPP Seminar

Challenges and first results on modeling halos and galaxies in the ultra-high-redshift universe
Aaron Yung, Space Telescope Science Institute
Event Type: Astro Seminar
Time: 2:00 PM - 3:15 PM
Location: 726 Broadway, Room #802
Abstract: The superb capabilities of JWST have extended our vision to the ultra-high-redshift universe  (z > 12) and many early JWST surveys have surprisingly revealed an abundance of massive galaxies that challenges conventional galaxy formation models.  In our quest to decipher this cosmic conundrum, we employ the well-established Santa Cruz semi-analytic model (SAM) in tandem with merger trees extracted from the suite of Gadget at Ultrahigh Redshift with Extra-Fine Timesteps (GUREFT) simulations, which consists of 170 snapshots spanning 40 > z > 6 and resolving halos down to progenitor halo masses of log(Mvir/Msun)~5. With these merger trees serving as the robust backbone, we explore and quantify the impact from various sources of uncertainties, including a potentially evolving mass-to-light ratio driven by changes in the IMF, under-reported uncertainties from field-to-field variance, high uncertainties in photometric redshift, etc. In our study, we have also investigated the number density of halo populations in this cosmic epoch, as well as the gas cooling rate and star formation efficient of galaxies, and come to the conclusion that the stellar feedback models currently in place in our model, which is also adopted by many hydrodynamic simulations, is ejecting gas as quickly as halo accrete mass, which deprive our galaxies from forming stars. We will also present timely, new simulated results for various alternative star formation and stellar feedback models and discuss the implied necessary conditions to reproduce the observed ultra-z galaxies.