Symmetry in Fundamental Parameters of Galaxies on the Star-forming Main Sequence

TL;DR

This study uncovers a symmetry in galaxy structural properties on the star-forming main sequence, linking SFR dispersion to fluctuations in cosmic accretion flows and stellar surface density, advancing understanding of galaxy evolution.

Contribution

It reveals a fundamental symmetry in galaxy properties on the SFMS and connects SFR dispersion to accretion flow oscillations regulated by stellar surface density.

Findings

Galaxies above and below the SFMS share similar structural parameters.

SFR dispersion correlates with galaxy size and stellar surface density.

SFR variation is driven by oscillations in cosmic accretion flows.

Abstract

The Star-Forming Main Sequence (SFMS) serves as a critical framework for understanding galaxy evolution, highlighting the relationship between star formation rates (SFR) and stellar masses M_* across cosmic time. Despite its significance, the origin of the 0.3-0.4 dex dispersion in the SFMS remains a key unresolved question. Uncovering the origin of dispersion is crucial for understanding the evolution of galaxies. Using a large sample of approximately 500,000 galaxies, we reveal an unprecedented symmetry in the distribution of key structural properties-effective radius (R_{\rm e}), stellar surface density (M_*/R_{\rm e}^2), and morphology on the SFMS. This symmetry implies that galaxies with high (above SFMS) and low (below SFMS) SFRs share similar fundamental parameters. Moreover, galaxies with smaller R_{\rm e} or higher M_*/R_{\rm e}^2 exhibit greater dispersion in SFR. This dispersion reflects the response to fluctuations in cosmic accretion flows, while the SFR itself represents the time-averaged effect over the gas consumption timescale. Shorter gas consumption timescales, associated with higher M_*/R_{\rm e}^2, lead to greater SFR dispersion. Our results reveal that the variation of SFR originates from the oscillation of accretion flow and is regulated by the stellar surface density.