Is feedback-free star formation possible?
Year: 2025
Type: article
Abstract: It has been suggested that, if the free-fall time of star-forming clouds is shorter than the lifetime ( ∼ 3 Myr) of massive stars exploding as supernovae (SN), a large fraction of the cloud gas can be converted into stars during an allegedly `feedback-free’ phase. Here, we show that radiation pressure from Ly α photons produced in the pre-SN phase can instead erase feedback-free conditions, and severely limit the star formation efficiency (SFE). We find that, for a constant star formation rate, all clouds with gas surface density have ϵ * < 0.08 . Higher SFE values can only be reached if Ly α -driven shells fragment and form stars. While advanced RHD simulations are required to establish the importance of this effect, adopting an optimistic guess, we find that the SFE increases with cloud surface density, rising from ϵ * = 0.023 at Σ g = 37 M ⊙ p c − 2 to ϵ * = 0.27 at Σ g = 1.7 × 10 5 M ⊙ p c − 2 . Given the optimistic assumptions adopted, these numbers should be regarded as upper limits. We conclude that Ly α radiation pressure strongly limits the SFE, even at solar metallicities, erasing the possibility that a feedback-free star formation mode with ϵ * ≳ 0.4 exists in the pre-SN phase. This conclusion remains valid even when other effects such as dust destruction of Ly α photons, presence of HII regions, velocity gradients, atomic recoil, and turbulence are considered.
Source: The Open Journal of Astrophysics
DOI: 10.33232/001c.144792
Institution: Scuola Normale Superiore
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W4414451494