Characterizing uniform star formation efficiencies with marginally stable galactic discs
Characterizing uniform star formation efficiencies with marginally stable galactic discs
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DOI：
10.1093/mnras/stw993
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发表时间：
2016-04
影响因子：
4.8
通讯作者：
O. I. Wong;G. Meurer;Z. Zheng;T. Heckman;D. Thilker;M. Zwaan
中科院分区：
文献类型：
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作者：
O. I. Wong;G. Meurer;Z. Zheng;T. Heckman;D. Thilker;M. Zwaan
我们研究了基于HI的星星形成效率（SFE_HI），星星形成速率与原子氢（HI）质量的比值，在一个恒定稳定的恒星形成盘模型的背景下。我们对HI选定星系的观测表明，在恒星质量的5个数量级范围内，SFE相当恒定（log SFE_HI = -9.65 yr-1，色散为0.3 dex）。我们提出了一个模型来解释这一结果，其主要原理是星系内的气体形成一个均匀的稳定盘，恒星形成在这个盘的分子气体。我们测试两个版本的模型不同的处方，确定的分子气体分数，根据流体静压，或恒星表面密度的磁盘。对于像银河系这样的大质量星系，我们发现这两种方法预测的SFE_HI与观测结果相似。然而，对于低质量星系，流体静压力处方是一个更准确的SFE_HI预测器。我们的模型是第一个将低红移星系中观测到的均匀SFE_HI与具有恒定边缘稳定性的恒星形成盘联系起来的模型。虽然在我们的模型中旋转振幅Vmax是盘结构的主要驱动因素，我们发现星系的特定角动量可能在解释SFE_HI和盘的有效表面亮度之间的弱相关性方面发挥作用。
We examine the HI-based star formation efficiency (SFE_HI), the ratio of star formation rate to the atomic Hydrogen (HI) mass, in the context of a constant stability star-forming disk model. Our observations of HI-selected galaxies show SFE to be fairly constant (log SFE_HI = -9.65 yr-1 with a dispersion of 0.3 dex) across ~5 orders of magnitude in stellar masses. We present a model to account for this result, whose main principle is that the gas within galaxies forms a uniform stability disk and that stars form within the molecular gas in this disk. We test two versions of the model differing in the prescription that determines the molecular gas fraction, based on either the hydrostatic pressure, or the stellar surface density of the disk. For high-mass galaxies such as the Milky Way, we find that either prescription predicts SFE_HI similar to the observations. However, the hydrostatic pressure prescription is a more accurate SFE_HI predictor for low-mass galaxies. Our model is the first model that links the uniform SFE_HI observed in galaxies at low redshifts to star-forming disks with constant marginal stability. While the rotational amplitude Vmax is the primary driver of disk structure in our model, we find the specific angular momentum of the galaxy may play a role in explaining a weak correlation between SFE_HI and effective surface brightness of the disk.