Star formation is boosted (and quenched) from the inside out: radial star formation profiles from MaNGA

TL;DR

This study uses MaNGA survey data to analyze how star formation varies within galaxies, revealing that starbursts and quenching occur from the inside out, supporting the 'compaction' scenario of galaxy evolution.

Contribution

It introduces a new metric, Delta Sigma_SFR, to quantify local star formation enhancements and deficits relative to the resolved main sequence across galaxy radii.

Findings

Starbursts are most intense within 3 kpc of galaxy centers.

Galaxies above the main sequence show metal-poor gas inflows.

Passive galaxies exhibit central star formation deficits.

Abstract

The tight correlation between total galaxy stellar mass and star formation rate (SFR) has become known as the star forming main sequence. Using ~487,000 spaxels from galaxies observed as part of the Sloan Digital Sky Survey Mapping Galaxies at Apache Point Observatory (MaNGA) survey, we confirm previous results that a correlation also exists between the surface densities of star formation (Sigma_SFR) and stellar mass (Sigma_mass) on kpc scales, representing a `resolved' main sequence. Using a new metric (Delta Sigma_SFR), which measures the relative enhancement or deficit of star formation on a spaxel-by-spaxel basis relative to the resolved main sequence, we investigate the SFR profiles of 864 galaxies as a function of their position relative to the global star forming main sequence (Delta SFR). For galaxies above the global main sequence (positive Delta SFR) Delta Sigma_SFR is elevated throughout the galaxy, but the greatest enhancement in star formation occurs at small radii (< 3 kpc, or 0.5 R_e). Moreover, galaxies that are at least a factor of three above the main sequence show diluted gas phase metallicities out to 2 R_e, indicative of metal-poor gas inflows accompanying the starbursts. For quiescent/passive galaxies that lie at least a factor of 10 below the star forming main sequence there is an analogous deficit of star formation throughout the galaxy with the lowest values of Delta Sigma_SFR in the central 3 kpc. Our results are in qualitative agreement with the `compaction' scenario in which a central starburst leads to mass growth in the bulge and may ultimately precede galactic quenching from the inside-out.