Oxygen Abundance Gradients and Kinematics in z~2-2.5 Galaxies
Abstract
Studying galaxies that were forming early in the universe's history can help shed light on the formation of the Milky Way and galaxies in the local universe. Specifically, understanding the spatial distribution of metals in galaxies can provide constraints on theories of galaxy formation and evolution. To address this issue, we have measured metallicity gradients and kinematics in four z~2-2.5 galaxies from the Keck Baryonic Structure Survey (KBSS) using near-infrared spectroscopy from Keck/MOSFIRE to analyze the HII regions in these galaxies. Our sample has galactic-radii of ~ 6.15-7.65 physical kpc, and we use the strong line ratio method, specifically the indicators [NII]λ 6585/Hα and [OIII]λ5007/Hβ, to determine the oxygen abundance. The metallicity measurements in one galaxy exhibit a negative gradient, consistent with inside out-growth models of galaxy formation, which predict that the formation of galaxies begins at the central regions, followed later by the formation of the outer edges. If this is the case, galaxies should present more metal enriched gas closer to the center than the edges. In contrast, one galaxy exhibits an inverted gradient with higher oxygen abundance at larger galactic radii, which could be attributed to gas inflow from filaments in the cosmic web. The remaining two galaxies in our sample do not show a distinct chemical gradient. The kinematics in our sample were measured, and the indicators in the spectra of three galaxies show ordered rotation, with rotational velocities consistent with similar z~2 galaxies in other spectroscopic samples.
- Publication:
-
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23314411A