Pre-supernova feedback mechanisms drive the destruction of molecular clouds in nearby star-forming disc galaxies

Abstract

It is a major open question which physical processes stop gas accretion on to giant molecular clouds (GMCs) and limit the efficiency at which gas is converted into stars. While feedback from supernova explosions has been the popular feedback mechanism included in simulations of galaxy formation and evolution, ‘early’ feedback mechanisms such as stellar winds, photoionisation and radiation pressure are expected to play an important role in dispersing the gas after the onset of star formation. These feedback processes typically take place on small scales (∼10 − 100 pc) and their effects have therefore been difficult to constrain in environments other than the Milky Way. We apply a novel statistical method to ∼1″ resolution maps of CO and Hα across a sample of nine nearby galaxies, to measure the time over which GMCs are dispersed by feedback from young, high-mass stars, as a function of the galactic environment. We find that GMCs are typically dispersed within ∼3 Myr on average after the emergence of unembedded high-mass stars, with variations within galaxies associated with morphological features rather than radial trends. Comparison with analytical predictions demonstrates that, independently of the environment, early feedback mechanisms (particularly photoionisation and stellar winds) play a crucial role in dispersing GMCs and limiting their star formation efficiency in nearby galaxies. Finally, we show that the efficiency at which the energy injected by these early feedback mechanisms couples with the parent GMC is relatively low (a few tens of per cent), such that the vast majority of momentum and energy emitted by the young stellar populations escapes the parent GMC.

From dawn till disk: Milky Way's turbulent youth revealed by the APOGEE+Gaia data

“…Although the physics of the self-enrichment during cluster formation is not understood (see, e.g., Section 4 of Bastian & Lardo 2018, for a review of models), we note that there is now a substantial observational evidence that molecular gas in the natal regions of star clusters is cleared by photoionization and stellar feedback within 3 − 5 Myr before the first core-collapse supernovae explode (e.g., Reggiani et al 2011;Kos et al 2019;Kruijssen et al 2019b;Chevance et al 2020Chevance et al , 2022Kim et al 2021). Such short time frame for star formation in clusters is also strongly indicated by theoretical models (e.g., Semenov et al 2021) and implies that models of cluster enrichment that achieve enrichment of the second generation stars with ≈ 3 − 5 Myr (e.g., Prantzos & Charbonnel 2006, see Section 4.6 in Bastian & Lardo 2018 for a review) are preferred.…”

The Gas-Star Formation Cycle in Nearby Star-forming Galaxies II. Resolved Distributions of CO and H$α$ Emission for 49 PHANGS Galaxies

“…This breakdown of the scaling relation has been attributed to the evolution of GMCs (Schruba et al 2010;Feldmann et al 2011;Kruijssen & Longmore 2014). The separation between GMCs and star formation tracers is now regularly used as an empirical probe of the cycle between gas and star formation (Kawamura et al 2009;Schruba et al 2010;Kruijssen & Longmore 2014;Kruijssen et al 2018), including the timescale of evolutionary cycling between GMCs and star formation (Kruijssen et al 2019;Chevance et al 2020;Kim et al 2021) and the impact of destructive stellar feedback (e.g., photoionization, stellar winds, and supernova explosions) on the structure of interstellar medium (ISM) and future star formation (Barnes et al 2020(Barnes et al , 2021Chevance et al 2022).…”

Mechanical feedback from stellar winds with an application to galaxy formation at high redshift

“…Agertz et al 2013;Stinson et al 2013;Geen et al 2015;Hopkins et al 2018) by removing gas from the birth giant molecular cloud (GMC). This scenario is supported by observations showing that gas is cleared out of the star-formation site before the first SN explosion (Barnes et al 2020) and that GMCs are dispersed within 3 Myr after the emergence of unembedded high-mass stars (Chevance et al 2022).…”