arXiv 2009.123722020-09astro-ph.GA

红移z<~ 0.5的环银河系MgII的全面普查

A Complete Census of Circumgalactic MgII at Redshift z<~ 0.5

Yun-Hsin Huang, Hsiao-Wen Chen, Stephen A. Shectman, Sean D. Johnson, Fakhri S. Zahedy, Jennifer E. Helsby, Jean-René Gauthier, Ian B. Thompson

备注：: 20 pages, 11 figures, accepted for publication in the MNRAS
DOI：: 10.1093/mnras/stab360

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摘要：

我们提出了一个调查镁吸收气体附近的380个随机星系，使用156个背景类星体（QSO）的吸收线探针。该样本包括211个孤立的（73个静止和138个恒星形成星系）和43个非孤立的星系与敏感的限制MgII吸收和Ha发射。投影距离的范围从d=9到497 kpc，星系的红移范围从z=0.10到0.48，静止坐标系绝对B带星等范围从$M_{\rm B}=-16.7$到$-22.8$。我们的分析表明，Mg Ⅱ的静止坐标系等效宽度$W_r$（2796）依赖于主星系的晕半径（$R_h$）、$B$ -带光度（$L_{\rm B}$）和恒星质量（$M_{\rm star}$），对于孤立的恒星形成星系，随着$d$的增加，其宽度急剧下降。$W_r$（2796）没有显示出孤立的、静止的星系或非孤立星系的明显趋势。Mg Ⅱ吸收气体$\langle κ\rangle$的覆盖率在$<40$ kpc时很高，达到$\langle κ\rangle\gtrsim 60$ %，在$d\gtrsim100$ kpc时迅速下降到$\langle κ\rangle\approx 0$.在气体半径内，$\langle κ\rangle$敏感地依赖于$M_{\rm star}$和由Ha推断的特定恒星形成率。与大质量静止晕不同，在恒星形成星系周围观测到的Mg II气体速度弥散与维里运动的预期一致，这将单个团簇质量限制为$m_{\rm cl} \gtrsim 10^5 \,\rm M_\odot$，冷气体吸积速率限制为$\sim 0.7-2 \,M_\odot\,\rm yr^{-1}$ .我们发现没有强烈的方位角的MgII吸收的恒星形成或静止星系的依赖。我们的研究结果强调需要一个均匀的，吸收盲样品建立一个整体的描述化学富集气体在环星系空间。

英文摘要：

We present a survey of MgII absorbing gas in the vicinity of 380 random galaxies, using 156 background quasi-stellar objects(QSOs) as absorption-line probes. The sample comprises 211 isolated (73 quiescent and 138 star-forming galaxies) and 43 non-isolated galaxies with sensitive constraints for both MgII absorption and Ha emission. The projected distances span a range from d=9 to 497 kpc, redshifts of the galaxies range from z=0.10 to 0.48, and rest-frame absolute B-band magnitudes range from $M_{\rm B}=-16.7$ to $-22.8$. Our analysis shows that the rest-frame equivalent width of MgII, $W_r$(2796), depends on halo radius($R_h$), $B$-band luminosity($L_{\rm B}$) and stellar mass ($M_{\rm star}$) of the host galaxies, and declines steeply with increasing $d$ for isolated, star-forming galaxies. $W_r$(2796) exhibits no clear trend for either isolated, quiescent galaxies or non-isolated galaxies. The covering fraction of MgII absorbing gas $\langle κ\rangle$ is high with $\langle κ\rangle\gtrsim 60$% at $<40$ kpc for isolated galaxies and declines rapidly to $\langle κ\rangle\approx 0$ at $d\gtrsim100$ kpc. Within the gaseous radius, $\langle κ\rangle$ depends sensitively on both $M_{\rm star}$ and the specific star formation rate inferred from Ha. Different from massive quiescent halos, the observed velocity dispersion of MgII gas around star-forming galaxies is consistent with expectations from virial motion, which constrains individual clump mass to $m_{\rm cl} \gtrsim 10^5 \,\rm M_\odot$ and cool gas accretion rate of $\sim 0.7-2 \,M_\odot\,\rm yr^{-1}$. We find no strong azimuthal dependence of MgII absorption for either star-forming or quiescent galaxies. Our results highlight the need of a homogeneous, absorption-blind sample for establishing a holistic description of chemically-enriched gas in the circumgalactic space.

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