Stellar winds and photoionization in a spiral arm

Abstract

The role of different stellar feedback mechanisms in giant molecular clouds is not well understood. This is especially true for regions with many interacting clouds as would be found in a galactic spiral arm. In this paper, building on previous work by Bending et al., we extract a 500 × 500 × 100 pc section of a spiral arm from a galaxy simulation. We use smoothed particle hydrodynamics (SPH) to re-simulate the region at higher resolution (1 M⊙ per particle). We present a method for momentum-driven stellar winds from main sequence massive stars, and include this with photoionization, self-gravity, a galactic potential, and ISM heating/cooling. We also include cluster-sink particles with accretion radii of 0.78 pc to track star/cluster formation. The feedback methods are as robust as previous models on individual cloud scales (e.g. Dale et al.). We find that photoionization dominates the disruption of the spiral arm section, with stellar winds only producing small cavities (at most ∼ 30 pc). Stellar winds do not affect the resulting cloud statistics or the integrated star formation rate/efficiency, unlike ionization, which produces more stars, and more clouds of higher density and higher velocity dispersion compared to the control run without feedback. Winds do affect the sink properties, distributing star formation over more low-mass sinks (∼102 M⊙) and producing fewer high-mass sinks (∼103 M⊙). Overall, stellar winds play at best a secondary role compared to photoionization, and on many measures, they have a negligible impact.

Supernovae and photoionizing feedback in spiral arm molecular clouds

“…We have not considered either radiation pressure or winds. We leave the first to future work, however in Ali et al (2022) we found that the impact of winds is less than photoionization and winds act primarily to excavate small 10 pc cavities around feedback emitting sinks. Likewise the winds contribute to velocity dispersions, but the results from Ali et al (2022) suggest this occurs on fairly small scales.…”

“…We leave the first to future work, however in Ali et al (2022) we found that the impact of winds is less than photoionization and winds act primarily to excavate small 10 pc cavities around feedback emitting sinks. Likewise the winds contribute to velocity dispersions, but the results from Ali et al (2022) suggest this occurs on fairly small scales. A second caveat is that we assume some efficiency for the feedback, here our fiducial choice of 50% was too high and probably 10-20% is more realistic.…”

The SOFIA FEEDBACK Legacy Survey Dynamics and Mass Ejection in the Bipolar H ii Region RCW 36

“…The physical processes that drive expanding motion of H II regions are still a matter of debate. Simulations generally predict that ionizing radiation is the main driver of expansion compared to stellar winds (e.g., Haid et al 2018;Geen et al 2021;Ali et al 2022). Yet simulating the high dynamic range of temperatures and densities associated with the presence of stellar winds in the ISM is challenging (e.g., Dale 2015).…”

The formation of clusters and OB associations in different density spiral arm environments

“…The time of the first supernova, and the total evolution time for the simulations are shown in Table 1. Winds are not included, however we found in Ali et al (2022) that winds have little effect in our simulations.…”