Affiliation: Harvard University

Contribution: Oral

Title: A census of 5 < z < 8 emission-line-free smouldering galaxies: Constraints on the primordial star formation cycle

Abstract: The number abundance of faint dwarf galaxies at high-redshift yields valuable insights on the primordial star formation cycle as the galaxy counts predicted by theoretical models is strongly sensitive to the feedback implementation. Inspired by the serendipitous spectroscopic discovery of an emission-line-free, seemingly quiescent galaxy at z=7.3, we undertake a photometric search for additional low-mass (log M*/M⊙ < 9) quiescent galaxies at 5 < z < 8. These smouldering galaxies (also referred to as mini-quenched) exhibit very low levels of ongoing star formation activity, thus providing novel constraints on the balance (or lack thereof) between gas accretion, star formation and feedback-driven outflows in the early Universe. In this talk, I will begin by discussing the basis for finding smouldering galaxies, outlining how deep NIRCam imaging with medium-band photometry (such as JADES) is essential. This is because i) low-mass quiescent galaxies are faint, with ii) the lack of emission lines identified in medium-band photometry betraying their dormant flame. I will further discuss the physical properties of these smouldering galaxies and number abundances. Indeed, current theoretical models of galaxy formation predict drastically different number counts for high-redshift smouldering galaxies, ranging from these systems being incredibly rare (~1%) to being common (~50%). Thus I will close by highlighting how observational studies of the smouldering galaxy population will greatly advance our understanding of primordial star formation.

This contribution can be found here (pdf).