Abstract

Understanding the quiescent galaxy population is incredibly important in the context of galaxy evolution. These galaxies are defined as having a low star formation rate, and their evolved stellar populations makes them identifiable by their redder colors in both the observed and rest-frame. Since their rest-frame optical emission lies in the infrared (IR) regime, observations of these galaxies at high redshifts were quite difficult prior to the launch of the James Webb Space Telescope (JWST). Recent observations of this high redshift population conflict with galaxy formation and evolution models that existed prior, with quiescent galaxies being detected more frequently than expected. This means that these models are poorly constrained, under predicting either the formation of massive galaxies at this early epoch or the onset of quenching in these galaxies. These observations also depict a diverse quiescent population, suggestive of an evolutionary picture that mixes numerous quenching mechanisms. In this work, I present a measurement of the photometric number density of quiescent galaxies utilizing the COSMOS-Web dataset. These galaxies are selected via their rest-frame (NUV-r-J) or Near Infrared Camera (NIRCam) colors, or by their measured specific star formation rates from this work's spectral energy distribution (SED) fits. After vetting, the final measured number densities show good agreement with previous observational results, leveraging the large area of COSMOS-Web to mitigate the uncertainty in these calculations, and extend these measurements out to higher redshifts. While only photometrically observed and still to be confirmed, the highest redshift objects in this sample contend with the redshift record for a quiescent galaxy.

Publication Date

8-2025

Document Type

Thesis

Student Type

Graduate

Degree Name

Astrophysical Sciences and Technology (MS)

Department, Program, or Center

Physics and Astronomy, School of

College

College of Science

Advisor

Jeyhan Kartaltepe

Advisor/Committee Member

Andrew Robinson

Advisor/Committee Member

Joshua Faber

Campus

RIT – Main Campus

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