A Value-added COSMOS2020 Catalog of Physical Properties: Constraining Temperature-dependent Initial Mass Function

TL;DR

This paper introduces a new catalog of galaxy properties derived using a temperature-dependent initial mass function (IMF), revealing a continuum of IMFs and lower stellar masses and star formation rates compared to traditional methods.

Contribution

It presents a novel modeling technique for galaxy properties assuming a temperature-dependent IMF applied to the COSMOS2020 catalog, providing new insights into galaxy evolution.

Findings

Galaxies show a continuum of IMFs and gas temperatures.

Most galaxies have bottom-lighter IMFs than the Milky Way.

Stellar masses and star formation rates are lower than previous estimates.

Abstract

This work presents and releases a catalog of new photometrically-derived physical properties for the $\sim 10^5$ most well-measured galaxies in the COSMOS field on the sky. Using a recently developed technique, spectral energy distributions are modeled assuming a stellar initial mass function (IMF) that depends on the temperature of gas in star-forming regions. The method is applied to the largest current sample of high-quality panchromatic photometry, the COSMOS2020 catalog, that allows for testing this assumption. It is found that the galaxies exhibit a continuum of IMF, and gas temperatures, most of which are bottom-lighter than measured in the Milky Way. As a consequence, the stellar masses and star formation rates of most galaxies here are found to be lower than those measured by traditional techniques in the COSMOS2020 catalog by factors of $\sim 1.6-3.5$ and $2.5-70.0$, respectively, with the change being the strongest for the most active galaxies. The resulting physical properties provide new insights into variation of the IMF-derived gas temperature along the star-forming main sequence and at quiescence, produce a sharp and coherent picture of downsizing, as seen from the stellar mass functions, and hint at a possible high-temperature and high-density stage of early galactic evolution.