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arXiv 1709.03992astro-ph.GA
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引力透镜红移10星系的HST棱镜观测

HST Grism Observations of a Gravitationally Lensed Redshift 10 Galaxy

Austin Hoag, Maruša Bradač, Gabriel B. Brammer, Kuang-Han Huang, Tommaso Treu, Charlotte A. Mason, Marco Castellano, Marcella Di Criscienzo, Tucker Jones, Patri… 展开作者

Austin Hoag, Maruša Bradač, Gabriel B. Brammer, Kuang-Han Huang, Tommaso Treu, Charlotte A. Mason, Marco Castellano, Marcella Di Criscienzo, Tucker Jones, Patrick Kelly, Laura Pentericci, Russell Ryan, Kasper B. Schmidt, Michele Trenti

摘要:

利用$\textit{Hubble}$空间望远镜($\textit{HST}$)WFC 3/IR光栅对一个莱曼破裂候选星系(MACS 1149-JD)进行了深光谱观测。在4个不同的位置角上进行了棱镜观测,G141棱镜总共有34个轨道,尽管沿着MACS 1149-JD的轨迹只有19个轨道相对未受污染。我们适合一个3参数($z$,F160 W MAG,和Ly $α$等效宽度)莱曼break星系模板的三个污染最少的棱镜位置角,使用MCMC方法。单独的棱镜数据与红移为$z_{\mathrm{grism}}=9.53^{+0.39}_{-0.60}$($68\%$置信度)的最佳拟合,与我们对$z_{\mathrm{phot}}=9.51^{+0.06}_{-0.12}$($68\%$置信度)的光度估计非常一致。我们的分析排除了MACS 1149-JD在$3σ$等效宽度为21 μ m以上的莱曼α发射,这与高度中性的IGM一致。我们探讨的情况下,红色的$\textit{Spitzer}$ /IRAC $[3.6] - [4.5]$颜色的星系以前指出的文献中是由于强大的休息帧光发射线从一个非常年轻的恒星人口,而不是4000个?休息。我们发现,虽然这可以提供一个解释所观察到的IRAC颜色,它需要一个较低的红移($z\lesssim9.1$),这是不太喜欢的$\textit{HST}$成像数据。棱镜的数据与这两种情况一致,表明红色的IRAC颜色仍然可以用4000光年的突破来解释,这是相对进化的恒星群体的特征。在这种解释中,测光表明$340^{+29}_{-35}$ Myr恒星群在大爆炸后已经存在于这个星系中,只有$\sim500~\mathrm{Myr}$。

英文摘要:

We present deep spectroscopic observations of a Lyman-break galaxy candidate (hereafter MACS1149-JD) at $z\sim9.5$ with the $\textit{Hubble}$ Space Telescope ($\textit{HST}$) WFC3/IR grisms. The grism observations were taken at 4 distinct position angles, totaling 34 orbits with the G141 grism, although only 19 of the orbits are relatively uncontaminated along the trace of MACS1149-JD. We fit a 3-parameter ($z$, F160W mag, and Ly$α$ equivalent width) Lyman-break galaxy template to the three least contaminated grism position angles using an MCMC approach. The grism data alone are best fit with a redshift of $z_{\mathrm{grism}}=9.53^{+0.39}_{-0.60}$ ($68\%$ confidence), in good agreement with our photometric estimate of $z_{\mathrm{phot}}=9.51^{+0.06}_{-0.12}$ ($68\%$ confidence). Our analysis rules out Lyman-alpha emission from MACS1149-JD above a $3σ$ equivalent width of 21 Å, consistent with a highly neutral IGM. We explore a scenario where the red $\textit{Spitzer}$/IRAC $[3.6] - [4.5]$ color of the galaxy previously pointed out in the literature is due to strong rest-frame optical emission lines from a very young stellar population rather than a 4000 Å break. We find that while this can provide an explanation for the observed IRAC color, it requires a lower redshift ($z\lesssim9.1$), which is less preferred by the $\textit{HST}$ imaging data. The grism data are consistent with both scenarios, indicating that the red IRAC color can still be explained by a 4000 Å break, characteristic of a relatively evolved stellar population. In this interpretation, the photometry indicate that a $340^{+29}_{-35}$ Myr stellar population is already present in this galaxy only $\sim500~\mathrm{Myr}$ after the Big Bang.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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