xGASS：全球HI光谱中不对称性及其与环境过程关系的稳健量化
xGASS: Robust quantification of asymmetries in global HI spectra and their relationship to environmental processes
摘要：
我们提出了一个分析的全球HI光谱的不对称性，从扩展GALEX阿雷西博SDSS调查（xGASS），恒星质量选择和气体分数有限的调查，这是代表本地宇宙中的星系HI属性。我们证明了HI谱中的不对称性与其信噪比密切相关，这意味着与以前的工作相反，不同样品的不对称分布不能在面值上进行比较。我们开发了一种方法来解释噪声引起的不对称性，并发现xGASS检测到的典型星系表现出比仅归因于噪声的不对称性更高的不对称性，在80%的置信水平下，37%的样本显示不对称性大于10%。我们发现，非对称星系包含，平均而言，29%的HI质量相比，他们的对称同行匹配的恒星质量和信噪比。我们还提出了明确的证据表明，卫星星系，作为一个人口，表现出更多的不对称HI光谱比中心和组中央星系显示出略高的HI不对称率相比，孤立的中心。所有这些结果都支持这样一种情况，即环境过程，特别是那些负责气体去除的过程，是xGASS中不对称性的主要驱动因素。
英文摘要：
We present an analysis of asymmetries in global HI spectra from the extended GALEX Arecibo SDSS Survey (xGASS), a stellar mass-selected and gas fraction-limited survey which is representative of the HI properties of galaxies in the local Universe. We demonstrate that the asymmetry in a HI spectrum is strongly linked to its signal-to-noise meaning that, contrary to what was done in previous works, asymmetry distributions for different samples cannot be compared at face value. We develop a method to account for noise-induced asymmetry and find that the typical galaxy detected by xGASS exhibits higher asymmetry than what can be attributed to noise alone, with 37% of the sample showing asymmetry greater than 10% at an 80% confidence level. We find that asymmetric galaxies contain, on average, 29% less HI mass compared to their symmetric counterparts matched in both stellar mass and signal-to-noise. We also present clear evidence that satellite galaxies, as a population, exhibit more asymmetric HI spectra than centrals and that group central galaxies show a slightly higher rate of HI asymmetries compared to isolated centrals. All these results support a scenario in which environmental processes, in particular those responsible for gas removal, are the dominant driver of asymmetry in xGASS.
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