Jamie Lin (Tufts University) - High Redshift Quiescent Galaxies in Overdensities at z~4-5 Observed by JWST

The advent of JWST has revolutionized our understanding of the early Universe, most notably through the discovery of massive quiescent galaxies (QGs) at z>4. These systems challenge standard galaxy formation models, as they require both an extremely rapid assembly of stellar mass and an abrupt cessation of star formation within the first few billion years of cosmic time. To understand the mechanisms driving this early quenching, we must investigate the role of the environment.

In this talk, I present a search for rare, high-redshift QGs within four proto-clusters in GOODS-S and GOODS-N fields at z~4-6 using JWST Cycle 1 data from the FRESCO program. Leveraging a comprehensive dataset—including up to 17 NIRCam filters, MIRI imaging, and ancillary HST data—we identify 13 QG candidates with stellar masses ranging from log(M_*/M_odot)~9-11.

Our analysis reveals a clear positive correlation between stellar mass and the quiescent fraction. Notably, we observe significant variation across proto-clusters: proto-clusters in GOODS-N exhibit a 100% quiescent fraction in the highest mass bin log(M_*/M_odot)> 10.5), while analogous structures in GOODS-S appear devoid of massive QGs. Furthermore, these galaxies reside primarily on the outskirts of overdensity peaks—contrary to z~0 expectations—and we observe a sharp decline in QG prevalence at z > 5. These findings suggest that efficient quenching mechanisms were not yet fully mature at the highest redshifts and highlight the nuanced, diverse role of environment in early galaxy evolution.

The FCAD Astronomy Seminars cover a wide range of topics with speakers of all career levels, from graduate students and postdocs to faculty. The seminars take place on Wednesdays from 12-1 PM in LGRT 533. All members of the FCAD community are welcome to attend.