Efficient early stellar feedback can suppress galactic outflows by reducing supernova clustering

Abstract

We present a novel set of stellar feedback models, implemented in the moving-mesh code Arepo, designed for galaxy formation simulations with near-parsec (or better) resolution. These include explicit sampling of stars from the IMF, allowing feedback to be linked to individual massive stars, an improved method for the modelling of H ii regions, photoelectric heating from a spatially varying FUV field and supernova feedback. We perform a suite of 32 simulations of isolated Mvir = 1010 M⊙ galaxies with a baryonic mass resolution of 20 M⊙ in order to study the non-linear coupling of the different feedback channels. We find that photoionization and supernova feedback are both independently capable of regulating star formation to the same level, while photoelectric heating is inefficient. Photoionization produces a considerably smoother star formation history than supernovae. When all feedback channels are combined, the additional suppression of star formation rates is minor. However, outflow rates are substantially reduced relative to the supernova only simulations. We show that this is directly caused by a suppression of supernova clustering by the photoionization feedback, disrupting star forming clouds prior to the first supernovae. We demonstrate that our results are robust to variations of our star formation prescription, feedback models and the baryon fraction of the galaxy. Our results also imply that the burstiness of star formation and the mass loading of outflows may be overestimated if the adopted star particle mass is considerably larger than the mass of individual stars because this imposes a minimum cluster size.

The impact of pre-supernova feedback and its dependence on environment

“…Deharveng et al 1988;Bresolin et al 2009;Faesi et al 2014), planetary nebulae (PNe; e.g. Soffner et al 1996;Peña et al 2012;Stasińska et al 2013), and supernova remnants (SNRs; e.g. Blair & Long 1997;Millar et al 2012;Vučetić et al 2015).…”

Stellar winds and photoionization in a spiral arm

“…Simulations by Lucas et al (2020) show that the energy from SNe is able to escape clouds through low-density channels created by pre-SN feedback; this energy may have an impact on larger scales beyond an individual cloud. This is supported by some simulations of dwarf galaxies, in which early radiative feedback can aid SNe in driving stronger galactic outflows (Hu et al 2017;Emerick et al 2018Emerick et al , 2019, while others find weaker outflows due to photoionization producing fewer clusters of SNe (Smith et al 2021).…”

Bursty star formation during the Cosmic Dawn driven by delayed stellar feedback

“…We have focused on supernovae to provide the delay, but stellar feedback also includes radiative processes, which begins much sooner after star formation. We saw that allowing feedback to begin earlier damps out the burstiness, so this will help to moderate its effects (as seen in simulations by, e.g., Smith et al 2021). Moreover, if factors other than feedback control the star formation rate (by generating turbulence through radial transport, for example; Forbes et al 2014;Krumholz et al 2018), the star formation rate may be smoother.…”

“…Intuitively, one then expects that star formation will occur through repeated bursts, with episodes running away until feedback kicks in and temporarily shuts off star formation (or at least decreases its rate). Detailed numerical simulations, which typically incorporate stellar feedback in this manner, show strong bursts in both early galaxies (e.g., Kimm et al 2015) and dwarfs (e.g., Weisz et al 2012;Broussard et al 2019;Wheeler et al 2019;Emami et al 2019;Chaves-Montero & Hearin 2021;Iyer et al 2020;Kravtsov & Manwadkar 2021), though other forms of feedback can moderate these effects (e.g., Smith et al 2021).…”