Measuring the galaxy-mass and galaxy-dust correlations through magnification and reddening

TL;DR

This study detects and characterizes galaxy-mass and galaxy-dust correlations using magnification and reddening effects, revealing dust distribution and mass profiles around galaxies on large scales.

Contribution

It provides the first simultaneous measurement of gravitational magnification and dust reddening effects, constraining galaxy-mass and galaxy-dust correlation functions across cosmological distances.

Findings

Dust detected from 20 kpc to several Mpc, following a theta^-0.8 distribution.

Dust in halos is comparable to that in disks, with wavelength dependence consistent with interstellar dust.

Estimated cosmic dust density Omega_dust ~ 5x10^-6, half in halos of L* galaxies.

Abstract

We present a simultaneous detection of gravitational magnification and dust reddening effects due to galactic halos and large-scale structure. The measurement is based on correlating the brightness of ~85,000 quasars at z>1 with the position of 20 million galaxies at z~0.3 derived from the Sloan Digital Sky Survey and is used to constrain the galaxy-mass and galaxy-dust correlation functions up to cosmological scales. The presence of dust is detected from 20 kpc to several Mpc, and we find its projected density to follow: Sigma_dust ~ theta^-0.8, a distribution similar to mass. The amount of dust in galactic halos is found to be comparable to that in disks. On large scales its wavelength dependence is described by R_V=3.9+/-2.6, consistent with interstellar dust. We estimate the resulting opacity of the Universe as a function of redshift and find A_V~0.03 mag up to z=0.5. This, in turn, implies a cosmic dust density of Omega_dust ~ 5x10^-6, roughly half of which comes from dust in halos of ~L* galaxies. We present magnification measurements, corrected for dust extinction, from which the galaxy-mass correlation function is inferred. The mean mass profile around galaxies is found to be Sigma ~ 30 (theta/arcmin)^-0.8 h M_sun/pc^2 up to a radius of 10 Mpc, in agreement with gravitational shear estimates.