UV-IR color profiles of the outer regions of 2K nearby S$^{4}$G galaxies

TL;DR

This study uses UV and IR imaging to analyze the color profiles of nearby galaxies, revealing different radial color trends among galaxy types and suggesting outside-in quenching mechanisms.

Contribution

It provides the first detailed spatially-resolved UV-IR color profiles of S$^{4}$G galaxies, identifying distinct color evolution patterns and proposing environmental quenching processes.

Findings

Most GBS galaxy disks become bluer outward.

Most GRS galaxy disks remain color-stable radially.

Over 50% of GGV galaxies' outer disks redden, indicating outside-in quenching.

Abstract

We present our new, spatially-resolved, photometry in FUV and NUV from images obtained by GALEX, and IRAC1 (3.6 $\mu$m) photometry obtained by the Spitzer Space Telescope. We analyzed the surface brightness profiles $\mu_{\rm{FUV}}$, $\mu_{\rm{NUV}}$, $\mu_{[3.6]}$, as well as the radial evolution of the (FUV-NUV), (FUV - [3.6]), and (NUV - [3.6]) colors in the Spitzer Survey of Stellar Structures in Galaxies (S$^{4}$G) galaxies (d$<$40 Mpc) sample. We defined the GALEX Blue Sequence (GBS) and GALEX Red Sequence (GBR) from the (FUV - NUV) versus (NUV - [3.6]) color-color diagram, populated by late-type star forming galaxies and quiescent early-type galaxies respectively. While most disk becomes radially bluer for GBS galaxies, and stay constant for GRS galaxies, a large fraction ($>$50%) of intermediary GALEX Green Valley (GGV) galaxies' outer disks are becoming redder. An outside-in quenching mechanism such as environmentally-related mechanisms such as starvation or ram-pressure-stripping could explain our results.