The growth of H ii regions around massive stars: the role of metallicity and dust
The growth of H ii regions around massive stars: the role of metallicity and dust
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DOI：
10.1093/mnras/staa3992
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发表时间：
2021-01
影响因子：
4.8
通讯作者：
A. Ali
中科院分区：
文献类型：
--
作者：
A. Ali
气体金属度Z和相关的粉尘-气体比fd可以通过金属线冷却和UV吸收来影响H ii区域的生长。我们在包含大质量恒星的恒星形成区域中模拟这些效应。本文采用MonteCarlo辐射传输与流体力学耦合的方法，计算了恒星光电离和辐射压反馈，包括恒星辐射场和漫射辐射场，并采用团簇-汇粒子方法跟踪了105 M湍流云（Z/Z = 2，1，0.5，0.1和fd = 0.01Z/Z）的星星形成过程。这些模型在反馈下至少进化了150万年。较低的Z导致较高的温度和因此较大的H ii区域。当Z > Z时，辐射压Prad可以局部地超过汇粒子周围内半秒差距内的气压Pgas。在全球范围内，Prad/Pgas的比值约为1（2 Z）、0.3（Z）、0.1（0.5 Z）和0.03（0.1 Z）。在太阳模型中，排除RP导致电离体积比具有两种机制的基准模型小几倍。排除RP和紫外线衰减的灰尘的结果在一个更大的电离体积比基准的情况下。电离气体向外的径向膨胀速度达到+15 km s−1，而中性气体在大部分运行时间内都是向内的，除了0.1 Z超过+4 km s−1。Z和fd不会显著改变星星的形成效率，速率，或集群半质量半径，除了0.1 Z由于早期的中性气体驱逐。
Gas metallicity Z and the related dust-to-gas ratio fd can influence the growth of H ii regions via metal line cooling and UV absorption. We model these effects in star-forming regions containing massive stars. We compute stellar feedback from photoionization and radiation pressure (RP) using Monte Carlo radiative transfer coupled with hydrodynamics, including stellar and diffuse radiation fields.We follow a 105M turbulent cloud with Z/Z = 2, 1, 0.5, 0.1 and fd = 0.01Z/Z with a cluster-sink particle method for star formation. The models evolve for at least 1.5Myr under feedback. Lower Z results in higher temperatures and therefore larger H ii regions. For Z > Z , radiation pressure Prad can dominate locally over the gas pressure Pgas in the inner half-parsec around sink particles. Globally, the ratio of Prad/Pgas is around 1 (2 Z ), 0.3 (Z ), 0.1 (0.5 Z ), and 0.03 (0.1 Z ). In the solar model, excluding RP results in an ionized volume several times smaller than the fiducial model with both mechanisms. Excluding RP and UV attenuation by dust results in a larger ionized volume than the fiducial case. That is, UV absorption hinders growth more than RP helps it. The radial expansion velocity of ionized gas reaches +15 km s−1 outwards, while neutral gas has inward velocities for most of the runtime, except for 0.1 Z which exceeds +4 km s−1. Z and fd do not significantly alter the star formation efficiency, rate, or cluster half-mass radius, with the exception of 0.1 Z due to the earlier expulsion of neutral gas.