The Contribution of Stars, Dust, Neutral Gas and SMBHs in Galaxies to the Cosmic Baryon Inventory

TL;DR

This study estimates the cosmic mass history of stars, dust, neutral gas, and SMBHs in galaxies from redshift 0 to 3, revealing that only about 5% of baryons are within galaxies, with the rest dispersed in the intergalactic medium.

Contribution

It provides a self-consistent census of baryons in galaxies using spectral energy distribution modeling of extensive galaxy surveys, including dust, gas, stars, and SMBHs.

Findings

Dust mass history follows the star formation history but declines more slowly.

Neutral gas mass density is about 0.7 dex lower than 21cm measurements.

Galactic baryons (stars, gas, SMBHs, dust) account for approximately 5% of total baryons.

Abstract

We compute the cosmic stellar, dust and neutral gas mass history at $0<z\lesssim3$ using ProSpect spectral energy distribution modelling of $\approx 800 \, 000$ galaxies in the Galaxy and Mass Assembly (GAMA) survey and the Deep Extragalactic VIsible Legacy Survey (DEVILS). The cosmic dust mass history broadly follows the shape of the cosmic star formation history; though, the decline is slower, suggestive of a slowing rate of dust growth and destruction as the star formation declines past its peak at $z\approx 2$. Neutral gas masses were estimated by scaling the dust masses by the metallicity-dependent dust-to-gas ratio. The neutral gas mass density as traced by the dust is an average of $\approx 0.7$ dex lower than that measured from $21$cm experiments, most likely due to differences in the spatial scales inhabited by dust and HI. Folding in measurements of the supermassive black hole mass density obtained previously with similar data and methods, we present a self-consistent census of the baryons confined to galaxies. Stars, neutral gas, SMBHs and dust contained within the optical radii of galaxies account for $\approx 5$ per cent of the baryons. Most of the remaining $\approx 95$ per cent of baryons must be ionised and dispersed throughout the interstellar, circumgalactic and intergalactic media within, around and between galaxies.