New empirical constraints on the cosmological evolution of gas and stars in galaxies

Abstract

We combine the latest observationally motivated constraints on stellar properties in dark matter haloes, along with data-driven predictions for the atomic (HI) and molecular (H${}_2$) gas evolution in galaxies, to derive empirical relationships between the build-up of galactic components and their evolution over cosmic time. At high redshift ($z\gtrsim 4$), the frameworks imply that galaxies acquire their cold gas (both atomic and molecular) mostly by accretion, with the fraction of cold gas reaching about 20% of the cosmic baryon fraction. We infer a strong dependence of the star formation rate on the H${}_2$ mass, suggesting a near-universal depletion timescale of 0.1-1 Gyr in Milky Way sized haloes (of masses $10^{12}{M}_{\odot }$ at $z=0$). There is also evidence for a near-universality of the Kennicutt-Schmidt relation across redshifts, with very little dependence on stellar mass, if a constant conversion factor (${\alpha }_{\mathrm{CO}}$) of CO luminosity to molecular gas mass is assumed. Combining the atomic and molecular gas observations with the stellar build-up illustrates that galactic mass assembly in Milky-Way sized haloes proceeds from smooth accretion at high redshifts, towards becoming merger-dominated at late times ($z\lesssim 0.6$). Our results can be used to constrain numerical simulations of the dominant growth and accretion processes of galaxies over cosmic history.

8 pages, 6 figures, accepted for publication in MNRAS

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• The Cosmic Baryon and Metal Cycles
• The role of mergers and interactions in driving the evolution of dwarf galaxies over cosmic time
• A direct measurement of galaxy major and minor merger rates and stellar mass accretion histories at $z<3$ using galaxy pairs in the REFINE survey
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• Effect of low-mass galaxy interactions on their star formation
• New constraints on the evolution of the MHI-M* scaling relation combining CHILES and MIGHTEE-HI data
• Survey2Survey: A deep learning generative model approach for cross-survey image mapping
• EDEN: Exploring Disks Embedded in N-body simulations of Milky-Way-mass halos from Symphony
• A Multi-messenger view of Cosmic Dawn: Conquering the Final Frontier
• Recent star formation in 0.5<z<1.5 quiescent galaxies
• Gamma Analytical Modeling Evolution (GAME) I: The physical implications of deriving the stellar mass functions from z=0 to z=8