Observing Correlations Between Dark Matter Accretion and Galaxy Growth: I. Recent Star Formation Activity in Isolated Milky Way-Mass Galaxies

TL;DR

This study introduces an observational method to measure the correlation between dark matter accretion and star formation in isolated Milky Way-mass galaxies, finding no significant positive correlation at present epoch.

Contribution

The paper presents a novel technique to observationally assess the correlation between dark matter accretion and star formation, tested on SDSS data and simulations.

Findings

Positive correlation between dark matter accretion and star formation is ruled out with >85% confidence.

Star formation activity may be driven more by gas recycling than by fresh accretion.

Dark matter accretion does not strongly influence recent star formation in isolated Milky Way-mass galaxies.

Abstract

The correlation between fresh gas accretion onto haloes and galaxy star formation is critical to understanding galaxy formation. Different theoretical models have predicted different correlation strengths between halo accretion rates and galaxy star formation rates, ranging from strong positive correlations to little or no correlation. Here, we present a technique to observationally measure this correlation strength for isolated Milky Way-mass galaxies with $z < 0.123$. This technique is based on correlations between dark matter accretion rates and the projected density profile of neighbouring galaxies; these correlations also underlie past work with splashback radii. We apply our technique to both observed galaxies in the Sloan Digital Sky Survey as well as simulated galaxies in the UniverseMachine where we can test any desired correlation strength. We find that positive correlations between dark matter accretion and recent star formation activity are ruled out with $\gtrsim 85\%$ confidence. Our results suggest that star formation activity may not be correlated with fresh accretion for isolated Milky Way-mass galaxies at $z=0$ and that other processes, such as gas recycling, dominate further galaxy growth.