arXiv 2008.102072020-08astro-ph.GA

金属和在遥远宇宙中寻找分子：麦哲伦MIKE在2

Metals and a Search for Molecules in the Distant Universe: Magellan MIKE Observations of sub-DLAs at 2<z<3

Suraj Poudel, Varsha P. Kulkarni, Debopam Som, Celine Peroux

备注：: 14 pages, 20 figures, accepted for publication in MNRAS
DOI：: 10.1093/mnras/stab926

摘要：

我们提出了丰富的测量元素Zn，S，O，C，Si和Fe的四个子DLAs的红移范围从z=2.173到z=2.635使用观测从麦哲伦望远镜的MIKE摄谱仪约束的化学富集和富气星系的恒星形成。对于z=2.173、2.236、2.539和2.635的吸收体，使用弱耗尽元素O、S和/或Zn，我们发现光电离校正后的金属丰度为[S/H]=-0.50 \pm 0.11，[O/H]>-0.84，[O/H]=-1.27 \pm 0.12，和[Zn/H]=+0.40 \pm 0.12，分别此外，我们能够把约束的电子密度使用的精细结构线的C II* 和Si II* 的两个子DLA。我们发现，这些值远高于文献中发现的DLAs的中值。此外，我们估计的冷却速率lc=1.20 \times 10-26 erg s-1每个H原子的吸收体在z=2.173，这表明更高的恒星形成率密度在此子DLA比典型的恒星形成率密度在类似的红移DLA。我们还研究了我们的吸收剂的金属丰度与速度色散关系。大多数吸收体遵循人们可以从文献中的子DLAs的质量与金属丰度关系中预期的趋势。最后，我们能够把限制从CO分子的各种强线的非检测的分子柱密度。我们估计的3σ上限log N（CO，J=0）<13.87，log N（CO，J=0）<13.17，和log N（CO，J=0）<13.08，分别从在1544，1510和1478 nm附近的CO AX 0-0，1-0和2-0带的J=0水平的吸收的未检测。

英文摘要：

We present abundance measurements of the elements Zn, S, O, C, Si and Fe for four sub-DLAs at redshifts ranging from z=2.173 to z=2.635 using observations from the MIKE spectrograph on the Magellan telescope to constrain the chemical enrichment and star formation of gas-rich galaxies. Using weakly depleted elements O, S, and or Zn, we find the metallicities after the photoionization corrections to be [S/H]=-0.50\pm0.11, [O/H]>-0.84, [O/H]=-1.27\pm0.12, and [Zn/H]=+0.40\pm0.12 for the absorbers at z=2.173, 2.236, 2.539, and 2.635, respectively. Moreover, we are able to put constraints on the electron densities using the fine structure lines of C II* and Si II* for two of the sub-DLAs. We find that these values are much higher than the median values found in DLAs in the literature. Furthermore, we estimate the cooling rate lc=1.20\times10-26 erg s-1 per H atom for an absorber at z=2.173, suggesting higher star formation rate density in this sub-DLA than the typical star formation rate density for DLAs at similar redshifts. We also study the metallicity versus velocity dispersion relation for our absorbers. Most of the absorbers follow the trend one can expect from the mass versus metallicity relation for sub-DLAs in the literature. Finally, we are able to put limits on the molecular column density from the non detections of various strong lines of CO molecules. We estimate 3σupper limits of log N(CO,J=0)<13.87, log N(CO,J=0)<13.17, and log N(CO,J=0)<13.08, respectively, from the non-detections of absorption from the J=0 level in the CO AX 0-0, 1-0, and 2-0 bands near 1544, 1510, and 1478Å.

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