FLASH Talks: Zhiyuan Ji (Steward Observatory) & Rieko Momose (Carnegie Observatories)

Friday, 02 December 2022 1 p.m. — 2 p.m. MST

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

Zhiyuan Ji (Steward Observatory) & Rieko Momose (Carnegie Observatories)
Zhiyuan Ji, Steward Observatory
Reconstructing the Assembly of Massive Galaxies at Cosmic Noon
Understanding the transition from star-forming galaxies to quiescent galaxies, a process referred to as galaxy quenching, remains a key missing piece toward a complete picture of galaxy evolution. Strong correlations between the star-formation activity and the structural properties of galaxies are observed at least out to redshift z ~ 3. The physics behind these well-established correlations, however, still eludes us. Critical, but yet open questions are whether a causal link exists between structural transformations and quenching, and what the relative timing of the two phenomena is. I will present a series of our recent, empirical studies on the joint evolution of star-formation activity and structural properties of massive galaxies at Cosmic Noon. We use the SED-fitting code Prospector to reconstruct the nonparametric star formation history (SFH) of the massive galaxies at z~2. We find a clear dependence of the morphology of galaxies on their stellar-mass assembly history. Knowledge of the SFH also enables us to empirically reconstruct the structural evolution of individual galaxies, hence allow us to empirically estimate contributions from different physical mechanisms to the apparent structural evolution. While the progenitor effect is clearly observed and accounted for in our analysis, it alone is insufficient to explain the observed structural evolution. We show that, as they evolve from star-forming phase to quiescence, galaxies grow massive dense stellar cores. Quenching begins at the center and then propagates outward to the rest of the structure. Our empirical constraints are in good quantitative agreement with the model predictions from dissipative accretion of gas to the center followed by massive starbursts before final quiescence.
Rieko Momose, Carnegie Observatories
The relationship between IGM and galaxy as probes of the cosmic web
The matter in the Universe is distributed like a network called the large-scale structure or cosmic web. The observational probe of the cosmic web is the large-scale distribution of galaxies and the intergalactic medium (IGM). Because they trace the same underlying dark matter, one can expect their spatial correlation. Nonetheless, we cannot currently make their direct comparison due to the lack of either galaxy catalogs or IGM data, or both. Instead, we conducted the cross-correlation analysis and investigated the spatial connection between galaxies and the IGM. In this talk, I will present our latest results about the IGM-galaxy connection and its variety obtained from the Lyα forest tomography data, CLAMATO, and several galaxy catalogs at z = 2 in the archive. I will show similarities and differences in the cross-correlation function among galaxy properties and discuss the large-scale IGM neutral hydrogen environments around galaxies depending on galactic populations.