Description:

Large near-infrared spectroscopic surveys have confirmed that star-forming galaxies at cosmic noon (z~2-3) exhibit emission line spectra that are distinct from their local counterparts. These differences reflect important changes in the physical conditions and chemical enrichment patterns of galaxies at early times, correlated with differences in their star formation histories relative to most present-day galaxies. At z~2, almost all galaxies have nearly constant or rising star formation histories, but by z~0, galaxies overall have more modest star formation rates and many have largely finished forming stars. Using spectra from the Keck Baryonic Structure Survey (KBSS) and photoionization models designed to reconcile the joint rest-UV-optical spectra of high-z star-forming galaxies, I have demonstrated that the majority of z~2-3 galaxies have moderate oxygen enrichment but sub-solar iron enrichment as a result of their rapid assembly histories. I will show that this marked alpha-enhancement means that it is imperative to consider abundance patterns rather than a single "metallicity" when describing galaxies' chemical enrichment. I will also report new measurements of the correlation between galaxy stellar mass and multiple chemical tracers (inluding O, N, and Fe) at z~2-3 using my model method and discuss extant challenges to comparing metallicity scaling relations with predictions from cosmological simulations. These comparisons are critical for understanding the way in which energetic feedback acts to regulate star formation in galaxies throughout cosmic time, which remains an open question in modern astrophysics and will be one of the key science drivers of upcoming facilities such as the James Webb Space Telescope and the ELTs.

Speaker: Allison Strom, Carnegie Science

Host: Sarah Wellons

Keywords: Physics, Astronomy, Astrophysics