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arXiv 1809.01037astro-ph.GA
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星系切变和恒星反馈对恒星形成的影响

Impact of galactic shear and stellar feedback on star formation

Cédric Colling, Patrick Hennebelle, Sam Geen, Olivier Iffrig, Frédéric Bournaud

摘要:

数值剪切盒是用来进行三维模拟的1千秒差距分层立方盒湍流和自引力星际介质(在旋转框架)与超新星和HII反馈。我们改变由剪切引起的速度梯度的值和银河系磁场的初始值。最后计算了不同的恒星形成率和与这组模拟相关的结构的性质。我们首先确认,反馈有很强的限制作用,恒星的形成。银河系切变也有很大的影响:切变越大,SFR越低。以太阳附近的速度梯度值为例,SFR与观测到的肯尼柯特定律相比太高了,大约是3到6倍。这种差异可以通过以下论点来解决:相关的剪切值不是太阳附近的剪切值,而且实际上星团内的恒星形成效率不是100%。考虑到恒星形成云通常位于螺旋臂中的事实,那里的剪切力可以大大提高(正如星系尺度模拟所探测的那样),SFR现在接近观测值。不同的数值配方已经过测试的下沉颗粒,给出了一个数值的不确定性的一个因素,约为2的SFR。最后,我们还估计了稠密云中的速度弥散,发现它们比观测到的拉森定律低约2倍。结论.在我们的模拟中,磁场,剪切,HII区,和超新星都有助于显着降低SFR。在这个数值设置与反馈从超新星和HII区域和银河系剪切的相关值,SFR是兼容的观察到的,与数值不确定因子约为2。

英文摘要:

A numerical shearing box is used to perform three-dimensional simulations of a 1 kpc stratified cubic box of turbulent and self-gravitating interstellar medium (in a rotating frame) with supernovae and HII feedback. We vary the value of the velocity gradient induced by the shear and the initial value of the galactic magnetic field. Finally the different star formation rates and the properties of the structures associated with this set of simulations are computed. We first confirm that the feedback has a strong limiting effect on star formation. The galactic shear has also a great influence: the higher the shear, the lower the SFR. Taking the value of the velocity gradient in the solar neighbourhood, the SFR is too high compared to the observed Kennicutt law, by a factor approximately three to six. This discrepancy can be solved by arguing that the relevant value of the shear is not the one in the solar neighbourhood, and that in reality the star formation efficiency within clusters is not 100%. Taking into account the fact that star-forming clouds generally lie in spiral arms where the shear can be substantially higher (as probed by galaxy-scale simulations), the SFR is now close to the observed one. Different numerical recipes have been tested for the sink particles, giving a numerical incertitude of a factor of about two on the SFR. Finally we have also estimated the velocity dispersions in our dense clouds and found that they lie below the observed Larson law by a factor of about two. Conclusions. In our simulations, magnetic field, shear, HII regions, and supernovae all contribute significantly to reduce the SFR. In this numerical setup with feedback from supernovae and HII regions and a relevant value of galactic shear, the SFRs are compatible with those observed, with a numerical incertitude factor of about two.

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