Implications of a Temperature Dependent IMF I: Photometric Template Fitting

TL;DR

This study introduces a temperature-dependent IMF parameterization into photometric template fitting, revealing systematic variations in galaxy stellar populations and suggesting a top-heavier IMF at higher redshifts.

Contribution

It presents a novel IMF parameterization integrated into photometric fitting, uncovering evidence for a variable, temperature-dependent IMF across different galaxy populations.

Findings

Most galaxies have top-heavier IMFs than the Milky Way.

IMF becomes more top-heavy with increasing redshift.

Subpopulations show evolution consistent with dust temperature changes.

Abstract

A universal stellar initial mass function (IMF) should not be expected from theoretical models of star formation, but little conclusive observational evidence for a variable IMF has been uncovered. In this paper, a parameterization of the IMF is introduced into photometric template fitting of the COSMOS2015 catalog. The resulting best-fit templates suggest systematic variations in the IMF, with most galaxies exhibiting top-heavier stellar populations than in the Milky Way. At fixed redshift, only a small range of IMFs are found, with the typical IMF becoming progressively top-heavier with increasing redshift. Additionally, subpopulations of ULIRGs, quiescent- and star-forming galaxies are compared with predictions of stellar population feedback and show clear qualitative similarities to the evolution of dust temperatures.