A Detection of Circumgalactic Dust at Megaparsec Scales with Maximum Likelihood Estimation

Abstract

One of the more surprising astrophysical discoveries of the last decade has been the presence of enormous quantities of dust at megaparsec distances from galaxies, which has important implications for galaxy evolution, the circumgalactic and intergalactic medium, and observational cosmology. In this work, we present a novel method for studying these vast halos of circumgalactic dust: a maximum-likelihood estimator for dust-induced extinction of background galaxies. This estimator can accommodate a broad range of archival photometric data and can incorporate different dust reddening prescriptions, making it applicable to diverse galaxy types and redshifts. We apply the estimator to the redMaGiC catalog of luminous red galaxies, selected for their tight dispersion in color and well-constrained photometric redshifts, and measure the resulting extinction as a function of projected distance from WISExSuperCOSMOS and redMaGiC foreground galaxies. We detect significant dust-induced extinction profiles extending to at least 1 megaparsec from galactic disks, with noticeable differences between star-forming and quiescent galaxies: star-forming galaxies exhibit a pronounced rise in extinction within the inner 50 kiloparsecs and a steep decline beyond 1 megaparsec, while the quiescent galaxies host little dust in the inner halo but have detectable extinction out to 30 megaparsecs. We test the robustness of our results using star catalogs and inverted foreground and background samples and find no evidence for significant systematic error. Our approach provides a powerful tool for studying the interplay between circumgalactic dust, galaxy evolution, and large-scale structure, with potential applications in a number of astrophysical subfields.

Figures (6)

• Figure 1: Sky coverage of catalogs used in this analysis. Top row: foreground WISExSCOS (grey points) and the background high-luminosity high-redshift redMaGiC galaxy catalog (fuchsia points) before (left panel) and after (right panel) masking. Bottom row: WISExSCOS random galaxy catalog after application of the WISExSCOS survey mask alone (left panel) and after application of both WISExSCOS and DES survey masks (right panel).
• Figure 2: Color versus redshift for the two redMaGiC galaxy catalogs (small, dark red points) and their respective random galaxy catalogs (large, bright red points connected by a solid line). Top row: high density galaxy sample. Bottom row: high-luminosity high-redshift sample.
• Figure 3: Extinction vs impact parameter for WISExSuperCOSMOS (blue points) and redMaGiC LRGs (maroon points). Power-law fits are shown for the redMaGiC LRG profile (maroon dashed line) and the combined WISExSuperCOSMOS x redMaGiC profiles (blue dashed line). For comparison, the M10 result is shown in red. Results are based on the CSFD Milky Way extinction correction.
• Figure 4: Extinction profiles produced for systematics testing with best-fit power laws overplotted. Left panels show the full impact parameter range; right panels are cropped to high impact parameters. Top row: Gaia foreground cross-correlated with redMaGiC high-$z$ (maroon) and high-density (red) background catalogs. Middle row: WISExSuperCOSMOS galaxy foreground cross-correlated with DES Y3 stars. Bottom row: cross-correlation of redMaGiC high-$z$ foreground with $z<0.45$ high-density background.
• Figure 5: Comparison of extinction profiles obtained with the SFD (light blue) and CSFD (medium blue) Galactic extinction corrections. From left to right, profiles are shown for WISExSuperCOSMOS galaxies cross-correlated with high-density redMaGiC background galaxies, for WISExSuperCOSMOS galaxies cross-correlated with high-luminosity high-redshift redMaGiC background galaxies, and for high-density redMaGiC galaxies cross-correlated with high-luminosity high-redshift redMaGiC background galaxies. The M10 profile is plotted in red.