Stochastic star formation in early galaxies: JWST implications

A. Pallottini; A. Ferrara

doi:10.1051/0004-6361/202347384

paper

Stochastic star formation in early galaxies: JWST implications

arXiv:2307.03219 · doi:10.1051/0004-6361/202347384

Abstract

The star formation rate (SFR) in high redshift galaxies is expected to be time-variable due to competing physical processes. Such stochastic variability might boost the luminosity of galaxies, possibly explaining the over-abundance seen at $z ≳ 10$ by JWST. We aim at quantifying the amplitude and timescales of such variability, and identifying the key driving physical processes. We select 245 $z = 7.7$ galaxies with stellar mass $5 \times 1 0^{6} ≲ M_{⋆} / M_{⊙} ≲ 5 \times 1 0^{10}$ from SERRA, a suite of high-resolution, radiation-hydrodynamic cosmological simulations. After fitting the average SFR trend, $⟨ SFR ⟩$ , we quantify the time-dependent variation, $δ (t) \equiv lo g [SFR/ ⟨ SFR ⟩]$ for each system, and perform a periodogram analysis to search for periodicity modulations. We find that $δ (t)$ is distributed as a zero-mean Gaussian, with standard deviation $σ_{δ} ≃ 0.24$ (corresponding to a UV magnitude s.d. $σ_{UV} ≃ 0.61$ ) that is independent of $M_{⋆}$ . However, the modulation timescale increases with stellar mass: $t_{δ} \sim (9, 50, 100) Myr$ for $M_{⋆} \sim (0.1, 1, 5) \times 1 0^{9} M_{⊙}$ , respectively. These timescales are imprinted on the SFR by different processes: (i) photoevaporation, (ii) supernova explosions, and (iii) cosmological accretion/merging dominating in low, intermediate, and high mass systems, respectively. The predicted SFR variations cannot account for the required $z ≳ 10$ UV luminosity function boost. Other processes, such as radiation-driven outflows clearing the dust, must then be invoked to explain the enhanced luminosity of super-early systems.

arXiv comment5 pages, 4 figures, accepted by A&A

Stochastic star formation in early galaxies: JWST implications

Abstract

References in corpus (65)

Cited by in corpus (64)