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arXiv 1109.4150astro-ph.COastro-ph.GA
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银河系云、邻近星系、高红移星系和星暴中的一个普遍的局部恒星形成定律

A Universal, Local Star Formation Law in Galactic Clouds, Nearby Galaxies, High-Redshift Disks, and Starbursts

Mark R. Krumholz, Avishai Dekel, Christopher F. McKee

备注：
20 pages, 4, figures, 4 tables, emulateapj format, accepted to ApJ. This version fixes a minor error in equation 18; no other changes
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摘要：

虽然对本星系群星系的观测显示了一个非常简单的局部恒星形成规律，即星系中每个斑块的单位面积恒星形成率与分子气体表面密度呈线性关系，但最近对银河系分子云和高红移星系的观测显然显示了一种更复杂的关系，其中相同表面密度的区域可以以完全不同的速率形成恒星。这些数据被解释为意味着不同的恒星形成定律适用于不同的情况，恒星形成定律对大尺度星系特性而不是局部特性敏感，或者恒星形成有高密度阈值。在这里，我们整理了银河系分子云的解析观测、本星系群星系的kpc尺度观测以及本地宇宙和高红移中盘状星系和星暴星系的未解析观测。我们表明，所有这些数据实际上是符合一个简单的，本地的，体积恒星形成的法律。这种明显的变化源于这样一个事实，即观察到的物体具有各种各样的3D尺寸尺度和内部聚集程度，因此即使在固定的气柱密度下，观察到的区域也可以具有广泛变化的体积密度。我们提供了一个简单的理论框架来消除这种投影效应，并且我们表明，从质量约为10^3 Msun的小型太阳邻域云到质量约为10^11 Msun的亚毫米星系，所有的数据都落在一个单一的恒星形成定律上，其中SFR只是每个局部自由落体时间分子气体质量的约1%。相比之下，建议恒星形成的法律，其中恒星形成的时间尺度是由银河系的旋转周期或SFR是线性成比例的气体质量以上的一些密度阈值不匹配至少有一些数据。

英文摘要：

[abridged] While observations of Local Group galaxies show a very simple, local star formation law in which the star formation rate per unit area in each patch of a galaxy scales linearly with the molecular gas surface density, recent observations of both Milky Way molecular clouds and high redshift galaxies apparently show a more complicated relationship, in which regions of equal surface density can form stars at quite different rates. These data have been interpreted as implying either that different star formation laws apply in different circumstances, that the star formation law is sensitive to large-scale galaxy properties rather than local properties, or that there are high density thresholds for star formation. Here we collate resolved observations of Milky Way molecular clouds, kpc-scale observations of Local Group galaxies, and unresolved observations of both disk and starburst galaxies in the local universe and at high redshift. We show that all of these data are in fact consistent with a simple, local, volumetric star formation law. The apparent variations stem from the fact that the observed objects have a wide variety of 3D size scales and degrees of internal clumping, so even at fixed gas column density the regions being observed can have wildly varying volume densities. We provide a simple theoretical framework to remove this projection effect, and we show that all the data, from small Solar neighborhood clouds with masses ~10^3 Msun to sub-mm galaxies with masses ~10^11 Msun, fall on a single star formation law in which the SFR is simply ~1% of the molecular gas mass per local free-fall time. In contrast, proposed star formation laws in which the star formation timescale is set by the galactic rotation period or the SFR is linearly proportional to the gas mass above some density threshold fail to match at least some of the data.

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