星系的成团作为它们光度学估算的原子气体含量的函数
The clustering of galaxies as a function of their photometrically-estimated atomic gas content
摘要：
本文介绍了一种新的光度估算方法，它是恒星质量、恒星表面质量密度、NUV-r色和g-i色梯度四个参数的线性组合。利用GASS和ALOFA巡天的HI谱线探测结果，对邻近星系（0.025<z<0.05）的M_HI/M_* 进行了标定，结果表明，即使对于HI丰富的星系，该方法也能提供无偏的M_HI/M_* 估计。我们将此估计应用于SDSS/DR 7中相同红移范围内的~ 24，000个星系的样本。然后，我们将这些星系的恒星质量和HI质量分数和计算投影两点交叉关联函数相对于参考星系样本。结果进行了比较，从目前的半解析模型的星系形成的预测。对于恒星质量大于10^10 M_sun的星系，这种一致性是好的，但对于较低质量的系统则不然。然后，我们通过研究HI-穷人或HI-丰富的星系相对于正常HI含量的星系在100千秒差距和~5百万秒差距之间的尺度上的集群的偏见扩展分析。对于HI-缺乏人口，最强的偏差效应出现时，HI-缺乏的定义相比，相同的恒星质量和大小的星系。半解析模型无法重现这一现象，因为在半解析模型中，卫星中恒星形成的猝灭是通过“饥饿”发生的，而不依赖于它们的内部结构。发现质量大于10^10太阳质量的富HI星系与“正常”HI含量的星系相比是反偏置的。有趣的是，在低质量星系中没有发现这种效应。
英文摘要：
We introduce a new photometric estimator of the HI mass fraction (M_HI/M_*) in local galaxies, which is a linear combination of four parameters: stellar mass, stellar surface mass density, NUV-r colour, and g-i colour gradient. It is calibrated using samples of nearby galaxies (0.025<z<0.05) with HI line detections from the GASS and ALFALFA surveys, and it is demonstrated to provide unbiased M_HI/M_* estimates even for HI-rich galaxies. We apply this estimator to a sample of ~24,000 galaxies from the SDSS/DR7 in the same redshift range. We then bin these galaxies by stellar mass and HI mass fraction and compute projected two point cross-correlation functions with respect to a reference galaxy sample. Results are compared with predictions from current semi-analytic models of galaxy formation. The agreement is good for galaxies with stellar masses larger than 10^10 M_sun, but not for lower mass systems. We then extend the analysis by studying the bias in the clustering of HI-poor or HI-rich galaxies with respect to galaxies with normal HI content on scales between 100 kpc and ~5 Mpc. For the HI-deficient population, the strongest bias effects arise when the HI-deficiency is defined in comparison to galaxies of the same stellar mass and size. This is not reproduced by the semi-analytic models, where the quenching of star formation in satellites occurs by "starvation" and does not depend on their internal structure. HI-rich galaxies with masses greater than 10^10 M_sun are found to be anti-biased compared to galaxies with "normal" HI content. Interestingly, no such effect is found for lower mass galaxies.
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