Galaxy And Mass Assembly (GAMA): Properties and evolution of red spiral galaxies

TL;DR

This study uses multi-wavelength data from the GAMA survey to investigate why some nearby spiral galaxies appear red, finding that environment-driven gas and dust removal leads to reduced star formation and red colors without significant morphological change.

Contribution

It demonstrates that environmental mechanisms cause red spiral galaxies to have lower star formation and dust content, with no evidence of nuclear activity or inclination effects as primary causes.

Findings

Red spirals have lower sSFR and dust-to-stellar mass ratios.

Red spirals are more massive and in denser environments.

Gas-rich red spirals show lower SFR compared to blue spirals.

Abstract

We use multi-wavelength data from the Galaxy and Mass Assembly (GAMA) survey to explore the cause of red optical colours in nearby (0.002<z<0.06) spiral galaxies. We show that the colours of red spiral galaxies are a direct consequence of some environment-related mechanism(s) which has removed dust and gas, leading to a lower star formation rate. We conclude that this process acts on long timescales (several Gyr) due to a lack of morphological transformation associated with the transition in optical colour. The sSFR and dust-to-stellar mass ratio of red spiral galaxies is found to be statistically lower than blue spiral galaxies. On the other hand, red spirals are on average $0.9$ dex more massive, and reside in environments 2.6 times denser than their blue counterparts. We find no evidence of excessive nuclear activity, or higher inclination angles to support these as the major causes for the red optical colours seen in >= 47% of all spirals in our sample. Furthermore, for a small subsample of our spiral galaxies which are detected in HI, we find that the SFR of gas-rich red spiral galaxies is lower by ~1 dex than their blue counterparts.