GALEX Arecibo SDSS巡天VII：大质量星系的二元中性氢-恒星质量函数
The GALEX Arecibo SDSS Survey VII: The Bivariate Neutral Hydrogen-Stellar Mass Function for Massive Galaxies
摘要：
本文给出了作为GALEX Arecibo SDSS巡天（GASS）的一部分，在Arecibo的中性氢（HI）观测的480个本星系（0.025 < z < 0.050）的样本中得到的大质量（log M_*/M_sun > 10）星系的二元中性氢-恒星质量函数（HISMF）（phi（M_HI，M_*））。我们适合六种不同的模型的HISMF，并发现，Schechter函数，向下延伸到1% HI气体馏分，与一个额外的分数低于该限制的贡献，是最好的参数化的HISMF。我们计算了Omega_{HI, M_* >10^10}，发现大质量星系贡献了本宇宙HI密度的41%。除了合并的HISMF，我们还得到了一个连续的双变量拟合，这表明Schechter参数仅随恒星质量变化很弱：M_HI^* 是HI的特征质量，标度为M_*^0.39; α是中等HI质量时HISMF的斜率，标度为M_*^0.07; f是HI气体含量大于1%的星系比例。标度为M_*^-0.24。f随恒星质量的变化应是数值模拟的一个强约束。为了理解产生HISMF形状的物理机制，我们重新定义了Schechter函数的参数，作为恒星质量和恒星形成速率的显式函数，以产生三变量拟合。这一分析揭示了SFR的强烈趋势。虽然M_HI^* 随恒星质量和SFR的变化很弱，但α是恒星质量和特别是恒星形成速率的更强函数。HISMF是一个重要的工具，可用于约束宇宙学星系模拟，测试星系人口的HI含量的观测预测，并确定其属性偏离平均趋势的星系。
英文摘要：
We present the bivariate neutral atomic hydrogen (HI)---stellar mass function (HISMF) (phi(M_HI, M_*)) for massive (log M_*/M_sun > 10) galaxies derived from a sample of 480 local (0.025 < z < 0.050) galaxies observed in HI at Arecibo as part of the GALEX Arecibo SDSS Survey (GASS). We fit six different models to the HISMF and find that a Schechter function that extends down to a 1% HI gas fraction, with an additional fractional contribution below that limit, is the best parametrization of the HISMF. We calculate Omega_{HI, M_* >10^10} and find that massive galaxies contribute 41% of the HI density in the local universe. In addition to the binned HISMF we derive a continuous bivariate fit, which reveals that the Schechter parameters only vary weakly with stellar mass: M_HI^*, the characteristic HI mass, scales as M_*^0.39, alpha, the slope of the HISMF at moderate HI masses, scales as M_*^0.07, and f, the fraction of galaxies with HI gas fraction greater than 1%, scales as M_*^-0.24. The variation of f with stellar mass should be a strong constraint for numerical simulations. To understand the physical mechanisms that produce the shape of the HISMF we redefine the parameters of the Schechter function as explicit functions of stellar mass and star formation rate to produce a trivariate fit. This analysis reveals strong trends with SFR. While M_HI^* varies weakly with stellar mass and SFR, alpha is a stronger function of both stellar mass and especially star formation rate. The HISMF is a crucial tool that can be used to constrain cosmological galaxy simulations, test observational predictions of the HI content of populations of galaxies, and identify galaxies whose properties deviate from average trends.
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