The Scaling Relation between Galaxy Luminosity and WHIM Density from EAGLE Simulations with application to SDSS data

TL;DR

This study establishes a robust scaling relation between galaxy luminosity density and WHIM density from EAGLE simulations, and applies it to SDSS data to estimate the cosmic baryon content, aiding the search for missing baryons.

Contribution

It introduces a new calibration method linking galaxy luminosity to WHIM density, validated with simulations and applied to observational data to estimate baryon fractions.

Findings

The scaling relation predicts WHIM density with less than 0.5 dex scatter.

Application to SDSS data estimates WHIM contains about 31% of cosmic baryons.

Results are consistent with current missing baryon estimates within uncertainties.

Abstract

This paper presents an updated scaling relation between the optical luminosity density (LD) of galaxies in the $r$ band and the density of the warm-hot intergalactic medium (WHIM) in cosmic filaments, using the high-resolution EAGLE simulations. We find a strong degree of correlation between the WHIM density and the galaxy luminosity density, resulting in a scaling relation between the two quantities that permits to predict the WHIM density of filaments with a scatter of less than $\frac{1}{2}$ dex in a broad range of smoothed filament luminosity densities. In order to estimate the performance of the simulation-based calibration of the LD-WHIM density relation, we applied it to a sample of low-redshift filaments detected with the \emph{Bisous} method in the Legacy Survey SDSS~DR12 data. In the volume covered by the SDSS data, our relation predicts a WHIM density amounting to $31\pm7\pm12$ % (statistical errors followed by systematic) of cosmic baryon density. This agrees, albeit within the large uncertainties, with the current estimates of the cosmological missing baryon fraction, implying that our LD-WHIM density relation may be a useful tool in the search for the missing baryons. This method of analysis provides a new promising avenue to study the physical properties of the missing baryons, using an observable that is available for large volumes of the sky, complementary and independent from WHIM searches with absorption-line systems in the FUV or X-rays.