近盘星系中分子气体的一个常数耗尽时间
A Constant Molecular Gas Depletion Time in Nearby Disk Galaxies
摘要：
我们结合新的敏感，宽场CO数据从HERACLES调查的紫外和红外数据从GALEX和斯皮策比较表面密度的H2，Sigma_H2，和最近的恒星形成率，Sigma_SFR，在成千上万的位置在30个附近的盘星系。与以前的工作相比，我们将星系样本的大小增加了四倍多，并包括具有广泛星系属性的目标。即使在这项研究中的盘星系跨越广泛的属性，我们发现一个强大的和近似线性的相关性之间的Sigma_SFR和Sigma_H2在我们共同的分辨率为1 kpc。这意味着我们的样本中H2消耗时间中位数大致恒定，tau_H2 = Sigma_H2 / Sigma_SFR，约为2.35Gyr（包括重元素）。在1 kpc分辨率下，在Sigma_H2~5-100M_sun/pc^2的范围内，Sigma_H2和tau_H2之间只有很弱的相关，这一点被我们的数据所探测到。我们汇编了一系列广泛的文献测量，这些测量是使用各种恒星形成示踪剂，采样方案和物理尺度获得的，并表明总体而言，这些数据产生几乎完全相同的结果，尽管有更多的分散。我们将这些结果解释为强有力的，尽管是间接的证据，表明在螺旋星系盘中的巨大分子云中，恒星形成以统一的方式进行。
英文摘要：
We combine new sensitive, wide-field CO data from the HERACLES survey with ultraviolet and infrared data from GALEX and Spitzer to compare the surface densities of H2, Sigma_H2, and recent star formation rate, Sigma_SFR, over many thousands of positions in 30 nearby disk galaxies. We more than quadruple the size of the galaxy sample compared to previous work and include targets with a wide range of galaxy properties. Even though the disk galaxies in this study span a wide range of properties, we find a strong and approximately linear correlation between Sigma_SFR and Sigma_H2 at our common resolution of 1kpc. This implies a roughly constant median H2 consumption time, tau_H2 = Sigma_H2 / Sigma_SFR, of ~2.35Gyr (including heavy elements) across our sample. At 1kpc resolution, there is only a weak correlation between Sigma_H2 and tau_H2 over the range Sigma_H2~5-100M_sun/pc^2, which is probed by our data. We compile a broad set of literature measurements that have been obtained using a variety of star formation tracers, sampling schemes and physical scales and show that overall, these data yield almost exactly the same results, although with more scatter. We interpret these results as strong, albeit indirect evidence that star formation proceeds in a uniform way in giant molecular clouds in the disks of spiral galaxies.
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