论文标题
SMC状星系UGC 5282中的吸收线丰度：ISM稀释的证据
Absorption line abundances in the SMC-like galaxy UGC 5282: evidence for ISM dilution from inflows on kiloparsec scales
论文作者
论文摘要
We present an HST Cosmic Origins Spectrograph (COS) spectrum of the QSO SDSS J095109.12+330745.8 ($z_{em} = 0.645$) whose sightline passes through the SMC-like dwarf galaxy UGC 5282 ($M_B = -16.0$, $cz = 1577$ km s$^{-1}$ ), 1.2来自银河系中央HII地区投影的KPC。 $ \ log $ [$ n $（hi）cm $^{ - 2} \：$] = 20.89 $^{+0.12} _ { - 0.21}} \：\：$：$ \ n $（hi）cm $^{ - 2} \：{ - 0.21}} \：\：$。对随附的SII，PII和OI金属线的分析产生了中性气体金属性，$ z_ {hi} $，of [s/h] $ \ simeq $ [p/h] $ = -0.80 \ pm0.24 $。从中央HII区域的电离气体的金属度，$ z_ {hii} \：$，从其发射线中测量的是[o/h] $ = -0.37 \ pm0.10 $，$+0.43 \ pm 0.26 $的差额为$ z__ {hi} \：$。这种差异$δ$与其他恒星星系中对HII区域的发现是一致的，并支持这样的观念：在星系中，恒星形成区域附近的电离气体在系统的中性星际介质（ISM）中显示出比在其余的中性星际介质中存在的金属金属性更高（ISM）。 UGC 5282中发现的$δ$的正值（以及另一个恒星形成的星系）可能是由于在gpc尺度上与银河系间介质中的低金属气体与星系的ISM混合。该模型也与DLA吸收底部检测到的广泛的$α$排放一致，从吸收速度中抵消了$ \ sim 125 $ km s $^{ - 1} $。试图复制人口特征（例如质量金属关系）的星系进化模型可能需要从以$ z_ {hi} $表示的星系金属性开始，而不是传统上从$ z_ {hii} \：$中衡量的金属性。
We present an HST Cosmic Origins Spectrograph (COS) spectrum of the QSO SDSS J095109.12+330745.8 ($z_{em} = 0.645$) whose sightline passes through the SMC-like dwarf galaxy UGC 5282 ($M_B = -16.0$, $cz = 1577$ km s$^{-1}$ ), 1.2 kpc in projection from the central HII region of the galaxy. Damped Ly$α$ (DLA) absorption is detected at the redshift of UGC 5282 with $\log$[$N$(HI) cm$^{-2}\:$] = 20.89$^{+0.12}_{-0.21}\:\:$. Analysis of the accompanying SII, PII and OI metal lines yields a neutral gas metallicity, $Z_{HI}$, of [S/H] $\simeq$ [P/H] $= -0.80\pm0.24$. The metallicity of ionized gas from the central HII region, $Z_{HII}\:$, measured from its emission lines is [O/H]$= -0.37\pm0.10$, a difference of $+0.43\pm 0.26$ from $Z_{HI}\:$. This difference $δ$ is consistent with that seen towards HII regions in other star-forming galaxies and supports the idea that ionized gas near star forming regions shows systematically higher metallicities than exist in the rest of a galaxy's neutral interstellar medium (ISM). The positive values of $δ$ found in UGC 5282 (and the other star forming galaxies) is likely due to infalling low metallicity gas from the intergalactic medium that mixes with the galaxy's ISM on kpc scales. This model is also consistent with broad Ly$α$ emission detected at the bottom of the DLA absorption, offset by $\sim 125$ km s$^{-1}$ from the absorption velocity. Models of galaxy evolution that attempt to replicate population characteristics, such as the mass-metallicity relation, may need to start with a galaxy metallicity represented by $Z_{HI}$ rather than that measured traditionally from $Z_{HII}\:$.
