What controls star formation in the central 500 pc of the Galaxy
What controls star formation in the central 500 pc of the Galaxy
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DOI：
10.1093/mnras/stu494
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发表时间：
2013-03
影响因子：
4.8
通讯作者：
J. Kruijssen;S. Longmore;B. Elmegreen;N. Murray;J. Bally;L. Testi;R. C. K. J. E. Garching;E. Garchi
中科院分区：
文献类型：
--
作者：
J. Kruijssen;S. Longmore;B. Elmegreen;N. Murray;J. Bally;L. Testi;R. C. K. J. E. Garching;E. Garchi
银河系中央分子带（CMZ，即中央500 pc）中的星星形成率（SFR）比它所包含的大量致密气体所预期的低10倍以上，这挑战了当前的星星形成理论。在本文中，我们量化了哪些物理机制可能是负责任的。在大于盘尺度高度的尺度上，低SFR被认为是一致的，由于长期的不稳定性或可能的变化，气体流入沿着银河系酒吧的情节星星的形成。当包含气体和恒星时，CMZ是轻微的托姆勒稳定，但当只考虑气体时，CMZ是高度的托姆勒稳定，这表明自引力云的凝结率很低。在小尺度上，我们发现CMZ中的SFR可能是由于高湍流压力导致星星形成的临界密度升高而引起的。排除了星星形成的普遍密度阈值的存在。氢的HI-H2相变、潮汐场、由于底部重的初始质量函数而可能产生的大质量恒星、磁场和宇宙射线或辐射压力反馈也不能单独解释低SFR。我们提出了一个自洽的周期星星形成的CMZ，在几个不同的过程联合收割机抑制星星形成的影响。速率限制因素是气体向坍缩的缓慢演化-一旦星星形成开始，它就以正常速率进行。星星形成抑制物的普遍存在表明，在其他星系中，中心SFR降低应该是一种普遍现象。我们讨论了银河系尺度星星形成和超大质量黑洞生长的影响，并将我们的结果与其他极端环境中的星星形成条件联系起来。
The star formation rate (SFR) in the Central Molecular Zone (CMZ, i.e. the central 500 pc) of the Milky Way is lower by a factor of > 10 than expected for the substantial amount of dense gas it contains, which challenges current star formation th eories. In this paper, we quantify which physical mechanisms could be responsible. On scales larger than the disc scale height, the low SFR is found to be consistent with episodic star formation due to secular instabilities or possibly variations of the gas inflow along the Galact ic bar. The CMZ is marginally Toomre-stable when including gas and stars, but highly Toomre-stable when only accounting for the gas, indicating a low condensation rate of self-grav itating clouds. On small scales, we find that the SFR in the CMZ may be caused by an elevated critica l density for star formation due to the high turbulent pressure. The existence of a universal density threshold for star formation is ruled out. The HI‐H2 phase transition of hydrogen, the tidal field, a possible underproduction of massive stars due to a bottom-heavy initial mass function, magnetic fields, and cosmic ray or radiation pressure feedback also cannot individually explain the low SFR. We propose a self-consistent cycle of star formation in the CMZ, in which the effects of several different processes combine to inhibit star formation . The rate-limiting factor is the slow evolution of the gas towards collapse ‐ once star formation is initiated it proceeds at a normal rate. The ubiquity of star formation inhibitors suggests th at a lowered central SFR should be a common phenomenon in other galaxies. We discuss the implications for galactic-scale star formation and supermassive black hole growth, and relate our results to the star formation conditions in other extreme environments.