TY - JOUR

T1 - Evolution of Stellar Feedback in H ii Regions

AU - Olivier, Grace M.

AU - Lopez, Laura A.

AU - Rosen, Anna L.

AU - Nayak, Omnarayani

AU - Reiter, Megan

AU - Krumholz, Mark R.

AU - Bolatto, Alberto D.

PY - 2021/2/15

Y1 - 2021/2/15

N2 - Stellar feedback is needed to produce realistic giant molecular clouds and galaxies in simulations, but due to limited numerical resolution, feedback must be implemented using sub-grid models. Observational work is an important means to test and anchor these models, but limited studies have assessed the relative dynamical role of multiple feedback modes, particularly at the earliest stages of expansion when H ii regions are still deeply embedded. In this paper, we use multiwavelength (radio, infrared, and X-ray) data to measure the pressures associated with direct radiation (P-dir), dust-processed radiation (P-IR), photoionization heating (P-H II), and shock-heating from stellar winds (P-X) in a sample of 106 young, resolved H ii regions with radii less than or similar to 0.5 pc to determine how stellar feedback drives their expansion. We find that the P-IR dominates in 84% of the regions and that the median P-dir and P-H II are smaller than the median P-IR by factors of 6 and 9, respectively. Based on the radial dependences of the pressure terms, we show that H ii regions transition from P-IR-dominated to P-H II-dominated at radii of similar to 3 pc. We find a median trapping factor of f(trap) similar to 8 without any radial dependence for the sample, suggesting this value can be adopted in sub-grid feedback models. Moreover, we show that the total pressure is greater than the gravitational pressure in the majority of our sample, indicating that the feedback is sufficient to expel gas from the regions.

AB - Stellar feedback is needed to produce realistic giant molecular clouds and galaxies in simulations, but due to limited numerical resolution, feedback must be implemented using sub-grid models. Observational work is an important means to test and anchor these models, but limited studies have assessed the relative dynamical role of multiple feedback modes, particularly at the earliest stages of expansion when H ii regions are still deeply embedded. In this paper, we use multiwavelength (radio, infrared, and X-ray) data to measure the pressures associated with direct radiation (P-dir), dust-processed radiation (P-IR), photoionization heating (P-H II), and shock-heating from stellar winds (P-X) in a sample of 106 young, resolved H ii regions with radii less than or similar to 0.5 pc to determine how stellar feedback drives their expansion. We find that the P-IR dominates in 84% of the regions and that the median P-dir and P-H II are smaller than the median P-IR by factors of 6 and 9, respectively. Based on the radial dependences of the pressure terms, we show that H ii regions transition from P-IR-dominated to P-H II-dominated at radii of similar to 3 pc. We find a median trapping factor of f(trap) similar to 8 without any radial dependence for the sample, suggesting this value can be adopted in sub-grid feedback models. Moreover, we show that the total pressure is greater than the gravitational pressure in the majority of our sample, indicating that the feedback is sufficient to expel gas from the regions.

KW - Galaxy formation

KW - Stellar feedback

KW - Star formation

KW - Star-forming regions

KW - H II regions

KW - Compact H II region

U2 - 10.3847/1538-4357/abd24a

DO - 10.3847/1538-4357/abd24a

M3 - Journal article

VL - 908

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

M1 - 68

ER -