Thermal Regulation and the Star-Forming Main Sequence

TL;DR

This paper presents a toy model linking cosmic rays, initial mass function, and heating processes to regulate star formation, successfully reproducing the observed main sequence and making testable predictions about galaxy evolution.

Contribution

It introduces a new galaxy evolution model incorporating temperature-dependent IMF and heating effects, explaining the star-forming main sequence across redshifts.

Findings

Model reproduces the star-forming main sequence over broad redshift range

Predicts higher metallicities and dust masses at high redshift

Suggests lower stellar mass-to-light ratios, affecting mass and dark matter inferences

Abstract

We argue that the interplay between cosmic rays, the initial mass function, and star formation plays a crucial role in regulating the star-forming "main sequence". To explore these phenomena we develop a toy model for galaxy evolution in which star formation is regulated by a combination of a temperature-dependent initial mass function and heating due to starlight, cosmic rays and, at very high redshift, the cosmic microwave background. This produces an attractor, near-equilibrium solution which is consistent with observations of the star-forming main sequence over a broad redshift range. Additional solutions to the same equations may correspond to other observed phases of galaxy evolution including quiescent galaxies. This model makes several falsifiable predictions, including higher metallicities and dust masses than anticipated at high redshift and isotopic abundances in the Milky Way. It also predicts that stellar mass-to-light ratios are lower than produced using a Milky Way-derived IMF, so that inferences of stellar masses and star formation rates for high redshift galaxies are overestimated. In some cases, this may also transform inferred dark matter profiles from core-like to cusp-like.