Does environment affect the star formation histories of early-type galaxies?

TL;DR

This study investigates how environment influences the star formation histories of early-type galaxies by analyzing spectral data from SDSS, revealing that environment has a secondary effect compared to internal galaxy properties.

Contribution

The paper introduces a novel spectral analysis method using principal component analysis to quantify environmental effects on galaxy star formation histories.

Findings

Environment has a secondary impact on galaxy spectra compared to internal properties.

Spectral parameters correlate with stellar age and recent star formation.

Local properties like velocity dispersion show stronger correlations with stellar age.

Abstract

Differences in the stellar populations of galaxies can be used to quantify the effect of environment on the star formation history. We target a sample of early-type galaxies from the Sloan Digital Sky Survey in two different environmental regimes: close pairs and a general sample where environment is measured by the mass of their host dark matter halo. We apply a blind source separation technique based on principal component analysis, from which we define two parameters that correlate, respectively, with the average stellar age (eta) and with the presence of recent star formation (zeta) from the spectral energy distribution of the galaxy. We find that environment leaves a second order imprint on the spectra, whereas local properties - such as internal velocity dispersion - obey a much stronger correlation with the stellar age distribution.