Implications of a Temperature Dependent IMF II: An Updated View of the Star-Forming Main Sequence

TL;DR

This study explores how the temperature-dependent initial mass function (IMF) influences galaxy properties, revealing that most star-forming galaxies have a bottom-lighter IMF than the Milky Way, with variations based on galaxy mass and redshift.

Contribution

Introduces a temperature-dependent IMF parameter into galaxy modeling, uncovering new patterns in galaxy IMF characteristics across different masses and redshifts.

Findings

Most star-forming galaxies have a bottom-lighter IMF than the Milky Way.

Galaxies at fixed redshift share similar IMFs.

More massive star-forming galaxies exhibit less bottom-light IMFs.

Abstract

The stellar initial mass function (IMF) is predicted to depend upon the temperature of gas in star-forming molecular clouds. The introduction of an additional parameter, $T_{IMF}$ , into photometric template fitting, allows galaxies to be fit with a range of IMFs. Three surprising new features appear: (1) most star-forming galaxies are best fit with a bottom-lighter IMF than the Milky Way; (2) most star-forming galaxies at fixed redshift are fit with a very similar IMF; and (3) the most massive star-forming galaxies at fixed redshift instead exhibit a less bottom-light IMF, similar to that measured in quiescent galaxies. Additionally, since stellar masses and star formation rates both depend on the IMF, these results slightly modify the resulting relationship, while yielding similar qualitative characteristics to previous studies.