H-ATLAS/GAMA and HeViCS - Dusty Early-Type Galaxies in Different Environments

TL;DR

This study compares dust properties and star formation in early-type galaxies from two Herschel surveys, revealing environment-driven differences in dust content and star formation activity.

Contribution

It provides a direct comparison of dust and star formation properties of early-type galaxies in different environments using consistent methods.

Findings

H-ATLAS ETG have higher dust masses and dust-to-stellar mass ratios.

H-ATLAS ETG are found in sparser environments than HeViCS ETG.

H-ATLAS ETG show higher specific star formation rates and younger stellar populations.

Abstract

The Herschel Space Observatory has had a tremendous impact on the study of extragalactic dust. Specifically, early-type galaxies (ETG) have been the focus of several studies. In this paper we combine results from two Herschel studies - a Virgo cluster study HeViCS and a broader, low-redshift H-ATLAS/GAMA study - and contrast the dust and associated properties for similar mass galaxies. This comparison is motivated by differences in results exhibited between multiple Herschel studies of early-type galaxies. A comparison between consistent modified blackbody derived dust mass is carried out, revealing strong differences between the two samples in both dust mass and dust-to-stellar mass ratio. In particular, the HeViCS sample lacks massive ETG with as high a specific dust content as found in H-ATLAS. This is most likely connected with the difference in environment for the two samples. We calculate nearest neighbour environment densities in a consistent way, showing that H-ATLAS ETG occupy sparser regions of the local Universe, whereas HeViCS ETG occupy dense regions. This is also true for ETG that are not Herschel-detected but are in the Virgo and GAMA parent samples. Spectral energy distributions are fit to the panchromatic data. From these we find that in H-ATLAS the specific star formation rate anticorrelates with stellar mass and reaches values as high as in our Galaxy. On the other hand HeViCS ETG appear to have little star formation. Based on the trends found here, H-ATLAS ETG are thought to have more extended star formation histories and a younger stellar population than HeViCS ETG.