The MOSDEF Survey: [SIII] as a New Probe of Evolving ISM Conditions
The MOSDEF Survey: [SIII] as a New Probe of Evolving ISM Conditions
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MOSDEF 调查：[SIII] 作为不断变化的 ISM 状况的新探索
DOI：
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发表时间：
2019
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影响因子：
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通讯作者：
F. Fornasini
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作者：
R. Sanders;T. Jones;A. Shapley;N. Reddy;M. Kriek;A. Coil;B. Siana;B. Mobasher;I. Shivaei;S. Price;W. Freeman;Mojegan Azadi;G. Leung;T. Fetherolf;T. Zick;L. D. Groot;G. Barro;F. Fornasini
作者：瑞安·桑德斯 (Sanders)琼斯，塔克；沙普利，爱丽丝E；雷迪，纳文 A；克里克，玛莉丝卡；线圈，艾莉森·L；西安娜，布莱恩；莫巴舍尔、巴赫拉姆；希瓦伊，艾琳；价格，塞多纳 H；弗里曼，威廉·R；阿扎迪，莫杰甘；梁吉恩 CK；费瑟罗夫，塔拉；齐克，汤姆·奥；格鲁特，劳拉·德；巴罗，吉列尔莫；弗朗西斯卡·M·福纳西尼 |摘要：我们提出了 $zsim1.5$ 恒星形成星系样本的 [SIII]$lambdalambda$9069,9531 测量值，这是第一个在 zg0.1 处测量这些线的样本。我们采用线路比率 S$_{32}$$equiv$[SIII]$lambdalambda$9069,9531/[SII]$lambdalambda$6716,6731 作为不断变化的 ISM 条件的新颖探针。由于该比率包括低电离线 [SII]，因此至关重要的是，在 $zsim0$ 积分星系光谱中考虑扩散电离气体 (DIG) 对发射线比率的影响，或者与不存在 DIG 发射的局部 HII 区域的样本进行比较。我们发现，在 $zsim1.5$ 和 $zsim0$ 处，S$_{32}$ 随着恒星质量的增加而减小，但依赖性很弱，表明 S$_{32}$ 与金属丰度具有非常浅的反相关性，而 O$_{32}$ 则表现出很强的金属丰度依赖性。因此，S$_{32}$ 在固定恒星质量下仅轻微演化红移。 $zsim1.5$ 样本相对于 $z=0$ HII 区域在固定的 [OIII]/H$ eta$ 处系统性地向较低的 S$_{32}$ 和较高的 [SII]/H$alpha$ 偏移。通过与光电离模型网格进行比较，我们发现这种趋势可以用这样一种情况来解释：固定 O/H 下电离谱随着红移的增加而变得更困难，但与固定 O/H 下电离参数的增加不一致。该分析证明了在演化研究中扩展到最强的静止光学谱线之外的优势，以及 [SIII] 在表征演化的 ISM 条件和恒星组成方面的特殊用途。这些测量结果为估计高红移星系的 [SIII] 线强度提供了基础，詹姆斯·韦伯太空望远镜将测量这条线的 z~5.5。
Author(s): Sanders, Ryan L; Jones, Tucker; Shapley, Alice E; Reddy, Naveen A; Kriek, Mariska; Coil, Alison L; Siana, Brian; Mobasher, Bahram; Shivaei, Irene; Price, Sedona H; Freeman, William R; Azadi, Mojegan; Leung, Gene CK; Fetherolf, Tara; Zick, Tom O; Groot, Laura de; Barro, Guillermo; Fornasini, Francesca M | Abstract: We present measurements of [SIII]$lambdalambda$9069,9531 for a sample of $zsim1.5$ star-forming galaxies, the first sample with measurements of these lines at zg0.1. We employ the line ratio S$_{32}$$equiv$[SIII]$lambdalambda$9069,9531/[SII]$lambdalambda$6716,6731 as a novel probe of evolving ISM conditions. Since this ratio includes the low-ionization line [SII], it is crucial that the effects of diffuse ionized gas (DIG) on emission-line ratios be accounted for in $zsim0$ integrated galaxy spectra, or else that comparisons be made to samples of local HII regions in which DIG emission is not present. We find that S$_{32}$ decreases with increasing stellar mass at both $zsim1.5$ and $zsim0$, but that the dependence is weak suggesting S$_{32}$ has a very shallow anticorrelation with metallicity, in contrast with O$_{32}$ that displays a strong metallicity dependence. As a result, S$_{32}$ only mildly evolves with redshift at fixed stellar mass. The $zsim1.5$ sample is systematicallty offset towards lower S$_{32}$ and higher [SII]/H$alpha$ at fixed [OIII]/H$eta$ relative to $z=0$ HII regions. By comparing to photoionization model grids, we find that such trends can be explained by a scenario in which the ionizing spectrum is harder at fixed O/H with increasing redshift, but are inconsistent with an increase in ionization parameter at fixed O/H. This analysis demonstrates the advantages of expanding beyond the strongest rest-optical lines for evolutionary studies, and the particular utility of [SIII] for characterizing evolving ISM conditions and stellar compositions. These measurements provide a basis for estimating [SIII] line strengths for high-redshift galaxies, a line that the James Webb Space Telescope will measure out to z~5.5.