Different influence of gas accretion on the evolution of star-forming and non-star-forming galaxies

TL;DR

This study uses integral field spectroscopy to compare how gas accretion affects the evolution of star-forming and non-star-forming galaxies with counter-rotating stellar disks, revealing different mechanisms and impacts.

Contribution

It provides the first detailed spatially resolved analysis of gas accretion effects on both star-forming and non-star-forming galaxies with counter-rotating disks.

Findings

Gas accretion fuels star formation in the inner regions of star-forming galaxies.

External gas preserves angular momentum and fuels star formation in the outer regions of non-star-forming galaxies.

Different gas accretion processes lead to distinct evolutionary pathways for the two galaxy types.

Abstract

Using integral field spectroscopic data from the Mapping Nearby Galaxies at Apache Point Observatory survey, we investigate the spatially resolved properties and empirical relations of a star-forming galaxy and a non-star-forming galaxy hosting counter-rotating stellar disks (CRDs). The DESI $g, r, z$ color images reveal no evidence of merger remnants in either galaxy, suggesting that gas accretion fuels the formation of CRDs. Based on the visible counter-rotation in the stellar velocity field, we can fit a spatial boundary to distinguish the inner and outer regions dominated by two stellar disks in each galaxy. In the inner region of the star-forming CRDs, stars are co-rotating with ionized gas, and the stellar population is younger. Comparison of the star-forming main sequence relations between the inner and outer regions reveals enhanced star formation in the inner region. Given the abundant pre-existing gas in the star-forming galaxy, collisions between pre-existing and external gas efficiently consume angular momentum, triggering star formation in the inner region. Conversely, in the outer region of the non-star-forming CRDs, stars are co-rotating with ionized gas, and the stellar population is younger. Comparison of the stellar mass-metallicity relations between the inner and outer regions indicates enriched gas-phase metallicity in the outer region. Considering the less abundant pre-existing gas in the non-star-forming galaxy, external gas could preserve angular momentum, fueling star formation in the outer region. Overall, gas accretion exhibits different influence on the evolution of star-forming and non-star-forming galaxies.