Thursday, June 13, 2024, 4:00pm
Speaker: Emma Kleiner (NASA GSFC)
Abstract: With the exciting launch of JWST, COSMOS-Web (Cycle 1, PIs: Casey and Kartelpe) allows for a first glance into the detailed morphologies of galaxies at Cosmic Noon and beyond. The ability to look further back into our Universe’s evolution with unprecedented sensitivity not only offers new discoveries but an opportunity to re-contextualize existing results. Galaxies that are undergoing a rapid burst of star-formation, or starbursts (SBs), have been the subject of numerous morphological studies aimed at explaining their nature. Studies of these galaxies in the more nearby Universe have provided mixed results in terms of significant mergers being the triggering event for the rapid onset of extreme star-formation. Furthermore, SBs are rarer in the local Universe, but with JWST we can now probe in detail the morphologies of SBs at the peak of their existence — Cosmic Noon. In this talk, I will present our latest results from COSMOS-Web where we assess the merger fraction of SBs galaxies at Cosmic Noon. Using the rich ancillary dataset afforded by the COSMOS field, we select a sample of SBs using both the rest-frame UV-NIR SED and FIR/sub-mm data. We then use a host of morphological measures to determine the merger fraction and interloper fraction of these sources using the 4 NIRCam Imaging mosaics of the April 2023 COSMOS-Web dataset. With the increased resolution of the NIRcam imaging we also identified multiple examples of sources being identified as “SBs” that were simply chance on-sky pairs and are spatially blended main-sequence galaxies in the lower-resolution ground-based and FIR imaging data. These sources represent important contaminants in ground-based SB samples, and we contextualize the effect of sample purity on conclusions drawn from ground-based studies. Finally, we report the merger fraction of SBs at Cosmic Noon as a function of stellar mass, star-formation, and compactness of the starburst.