Finding the Missing Baryons Using CMB as a Backlight

TL;DR

This paper introduces a novel method to detect missing baryons by cross-correlating galaxy momentum templates with CMB data, enabling direct detection of ionized gas in the intergalactic medium with significant signal-to-noise ratios.

Contribution

The paper presents a new technique for detecting the kinematic Sunyaev-Zel'dovich effect using galaxy momentum templates derived from surveys and CMB data, improving detection prospects.

Findings

Signal-to-noise ratios of 4, 9, and 12 for ACT with different galaxy surveys.

Signal-to-noise ratios of 11, 23, and 32 for PLANCK with different galaxy surveys.

Availability of galaxy momentum templates for direct cross-correlation with CMB maps.

Abstract

We present a new method for detecting the missing baryons by generating a template for the kinematic Sunyaev-Zel'dovich effect. The template is computed from the product of a reconstructed velocity field with a galaxy field; we find that the combination of a galaxy redshift survey such as SDSS and a CMB survey such as ACT and PLANCK can detect the kSZ, and thus the ionized gas, at significant signal-to-noise. Unlike other techniques that look for hot gas or metals, this approach directly detects the electrons in the IGM through their signature on the CMB. The estimated signal-to-noise for detecting the galaxy-momentum kSZ cross-correlation is 4, 9, and 12 for ACT (with survey area of 2000 $\mathrm{deg}^2$) with SDSS-DR4, SDSS3 and ADEPT respectively. The estimated signal-to-noise for PLANCK with SDSS-DR4, SDSS3 and ADEPT is 11, 23, and 32. Our method provides a new mean for determining properties of the ionized gas in the Universe. We provide galaxy momentum templates constructed from Sloan Digital Sky Survey online at our website at http://www.astro.princeton.edu/~shirley/SZ/SZ.html. The predicted correlation coefficients are provided along with the momentum maps. One can download the momentum templates and cross-correlate directly with CMB maps from ACT and PLANCK to detect the missing baryons.