We present constraints on the massive star and ionized gas properties for a sample of 62 star-forming galaxies at $z\sim2.3$. Using BPASS stellar population models, we fit the rest-UV spectra of galaxies in our sample to estimate age and stellar metallicity which, in turn, determine the ionizing spectrum. In addition to the median properties of well-defined subsets of our sample, we derive the ages and stellar metallicities for 30 high-SNR individual galaxies -- the largest sample of individual galaxies at high redshift with such measurements. Most galaxies in this high-SNR subsample have stellar metallicities of $0.001<Z_*<0.004$. We then use Cloudy+BPASS photoionization models to match observed rest-optical line ratios and infer nebular properties. Our high-SNR subsample is characterized by a median ionization parameter and oxygen abundance, respectively, of $\log(U)_{\textrm{med}}=-2.98\pm0.25$ and $12+\log(\textrm{O/H})_{\textrm{med}}=8.48\pm0.11$. Accordingly, we find that all galaxies in our sample show evidence for $α$-enhancement. In addition, based on inferred $\log(U)$ and $12+\log(\textrm{O/H})$ values, we find that the local relationship between ionization parameter and metallicity applies at $z\sim2$. Finally, we find that the high-redshift galaxies most offset from the local excitation sequence in the BPT diagram are the most $α$-enhanced. This trend suggests that $α$-enhancement resulting in a harder ionizing spectrum at fixed oxygen abundance is a significant driver of the high-redshift galaxy offset on the BPT diagram relative to local systems. The ubiquity of $α$-enhancement among $z\sim2.3$ star-forming galaxies indicates important differences between high-redshift and local galaxies that must be accounted for in order to derive physical properties at high redshift.
MOSDEF-3D: Keck/OSIRIS Maps of the Ionized ISM in $z \sim 2$ Galaxies
Department of Physics & Astronomy, University of California, Los Angeles（加州大学洛杉矶分校物理与天文学系）；Department of Physics and Astronomy, University of Kentucky（肯塔基大学物理与天文学系）；Department of Physics and Astronomy, University of California Davis（加州大学戴维斯分校物理与天文学系）；Department of Astronomy & Astrophysics, University of California, San Diego（加州大学圣地亚哥分校天文与天体物理学系）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；Department of Physics & Astronomy, University of California, Riverside（加州大学河滨分校物理与天文学系）
Galaxy Protoclusters as Drivers of Cosmic Reionization: I. Bubble Overlap at Redshift z ~ 7 in LAGER-z7OD1
University of California Santa Barbara（加州大学圣塔芭芭拉分校）；Goddard Space Flight Center（戈达德太空飞行中心）；The University of Tokyo（东京大学）；Space Telescope Science Institute（太空望远镜科学研究所）；MIT Kavli Institute for Astrophysics and Space Research（麻省理工学院卡弗里天体物理学与空间研究研究所）；CNRS, Institut d'Astrophysique de Paris（法国国家科学研究中心，巴黎天体物理研究所）；Chinese Academy of Sciences（中国科学院）；University of Science and Technology of China（中国科学技术大学）
