Dust in the Circumgalactic Medium of Low-Redshift Galaxies

TL;DR

This study detects and characterizes dust-induced reddening in the circumgalactic medium of low-redshift galaxies using SDSS data, revealing a large-scale dust distribution with weak dependence on galaxy mass.

Contribution

It presents the first measurement of circumgalactic dust reddening at low redshift using a novel standard crayons method with minimized systematic errors.

Findings

Reddening levels range from 0.5 to 10 millimagnitudes.

Reddening is weakly dependent on galaxy stellar mass.

Dust extends out to scales of 1 Mpc around galaxies.

Abstract

Using spectroscopically selected galaxies from the Sloan Digital Sky Survey we present a detection of reddening due to dust in the circumgalactic medium of galaxies. We detect the mean change in the colors of "standard crayons" correlated with the presence of foreground galaxies at z ~0.05 as a function of angular separation. Following Peek & Graves (2010), we create standard crayons using passively evolving galaxies corrected for Milky Way reddening and color-redshift trends, leading to a sample with as little as 2% scatter in color. We devise methods to ameliorate possible systematic effects related to the estimation of colors, and we find an excess reddening induced by foreground galaxies at a level ranging from 10 to 0.5 millimagnitudes on scales ranging from 30 kpc to 1 Mpc. We attribute this effect to a large-scale distribution of dust around galaxies similar to the findings of Menard et al. 2010. We find that circumgalactic reddening is a weak function of stellar mass over the range $6 \times 10^9 M_\odot$ -- $6 \times 10^{10} M_\odot$ and note that this behavior appears to be consistent with recent results on the distribution of metals in the gas phase.