论文标题
宇宙高点的典型矮星系的直接使用方法丰度
The Direct-Method Oxygen Abundance of Typical Dwarf Galaxies at Cosmic High-Noon
论文作者
论文摘要
我们提出了16个典型，重力镜，星形成，矮星系的凯克/MOSFIRE，静息，复合频谱，售价为$ 1.7 \ sillesim Z \ Lessim Z \ Lessim 2.6 $ 2.6 $（$ z_ {\ z {\ rm {mean}}} = 2.30 = 2.30 = 2.30 $），所有选择独立于发射线。这些星系的中间恒星质量为$ \ log（m_ \ ast/\ rm {m_ \ odot}）_ {\ rm {med {med}} = 8.29^{+0.51} _ { - 0.43} $和中间星星的中间星星形成率$ \ rm \ rm \ rm {sfr} 2.25^{+2.15} _ { - 1.26} \ m_ \ odot \ yr^{ - 1}} $。我们在考虑一个自举（仅统计）不确定性频谱时，我们测量了微弱的，电子温度敏感的发射线[O III] $ 4363排放线的意义为$2.5σ$（$4.1σ$）。这产生了$ 12+\ log（\ rm {o/h}）_ {\ rm {direct}} = 7.88^{+0.25} _ { - 0.22} $（$ 0.22} $（$ 0.15^{+0.12} _ {+0.12} _ { - 0.06} $ { - 0.06} $ { - 我们调查了本地校准的，基于氧气的，强的金属关系的高$ z $的适用性，发现ARXIV的本地参考校准：1805.08224最佳再生产（$ \ lyssim 0.12 $ dex）我们的复合金属性以固定的强线比。在固定的$ m_ \ ast $上，我们的复合材料由$ z \ sim 2.3 $ direct-method恒星质量$ \， - \，$ a arxiv：1907.00013的$气相金属关系（MZR）。与Illustristng和Fire模拟的预测MZR相比，我们发现与Fire MZR有着极好的一致性。我们的复合材料与本地定义的基本金属关系的固定$ m_ \ ast $和sfr保持一致。我们测量双重比率[O II] $λ$ 3729/[O ii] $ \ lambda3726 = 1.56 \ pm 0.32 $（$ 1.51 \ pm 0.12 $）和相应的电子密度为$ n_e = 1^{+215} 1^{+74} _ { - 0} \ \ rm {cm^{ - 3}} $）在考虑引导（仅统计）错误频谱时。该结果表明，低质量星系的密度低于$ z \ sim 2 $的高质量星系。
We present a Keck/MOSFIRE, rest-optical, composite spectrum of 16 typical, gravitationally-lensed, star-forming, dwarf galaxies at $1.7 \lesssim z \lesssim 2.6$ ($z_{\rm{mean}}=2.30$), all chosen independent of emission-line strength. These galaxies have a median stellar mass of $\log(M_\ast/\rm{M_\odot})_{\rm{med}} = 8.29^{+0.51}_{-0.43}$ and a median star formation rate of $\rm{SFR_{Hα}^{med} = 2.25^{+2.15}_{-1.26}\ M_\odot\ yr^{-1}}$. We measure the faint, electron-temperature-sensitive, [O III] $λ$4363 emission line at $2.5σ$ ($4.1σ$) significance when considering a bootstrapped (statistical-only) uncertainty spectrum. This yields a direct-method oxygen abundance of $12+\log(\rm{O/H})_{\rm{direct}}=7.88^{+0.25}_{-0.22}$ ($0.15^{+0.12}_{-0.06}\ \rm{Z_\odot}$). We investigate the applicability at high-$z$ of locally-calibrated, oxygen-based, strong-line metallicity relations, finding that the local reference calibrations of arXiv:1805.08224 best reproduce ($\lesssim 0.12$ dex) our composite metallicity at fixed strong-line ratio. At fixed $M_\ast$, our composite is well-represented by the $z \sim 2.3$ direct-method stellar mass$\,-\,$gas-phase metallicity relation (MZR) of arXiv:1907.00013. When comparing to predicted MZRs from the IllustrisTNG and FIRE simulations, we find excellent agreement with the FIRE MZR. Our composite is consistent with no metallicity evolution, at fixed $M_\ast$ and SFR, of the locally-defined fundamental metallicity relation. We measure the doublet ratio [O II] $λ$3729/[O II] $\lambda3726 = 1.56 \pm 0.32$ ($1.51 \pm 0.12$) and a corresponding electron density of $n_e = 1^{+215}_{-0}\ \rm{cm^{-3}}$ ($n_e = 1^{+74}_{-0}\ \rm{cm^{-3}}$) when considering the bootstrapped (statistical-only) error spectrum. This result suggests that lower-mass galaxies have lower densities than higher-mass galaxies at $z \sim 2$.
