Detection of intercluster gas in superclusters using the thermal Sunyaev-Zel'dovich effect

TL;DR

This study detects hot intercluster gas in superclusters using the thermal Sunyaev-Zel'dovich effect, suggesting it may account for a significant portion of the universe's missing baryons.

Contribution

First detection of intercluster gas in superclusters via tSZ effect after removing intracluster gas, providing insights into baryon distribution.

Findings

Detected supercluster tSZ signal at 6.4 sigma significance.

First evidence of intercluster gas in superclusters at 2.5 sigma.

Intercluster gas could explain 17-52% of missing baryons.

Abstract

Using a thermal Sunyaev-Zel'dovich (tSZ) signal, we search for hot gas in superclusters identified using the Sloan Digital Sky Survey Data Release 7 (SDSS/DR7) galaxies. We stack a Comptonization y map produced by the Planck Collaboration around the superclusters and detect the tSZ signal at a significance of 6.4 sigma. We further search for an intercluster component of gas in the superclusters. For this, we remove the intracluster gas in the superclusters by masking all galaxy groups/clusters detected by the Planck tSZ, ROSAT X-ray, and SDSS optical surveys down to a total mass of 10^13 Msun. We report the first detection of intercluster gas in superclusters with y = (3.5 +- 1.4) * 10^(-8) at a significance of 2.5 sigma. Assuming a simple isothermal and flat density distribution of intercluster gas over superclusters, the estimated baryon density is (Omega_gas / Omega_b) * (T_e/(8*10^6 K)) = 0.067 +- 0.006 +- 0.025. This quantity is inversely proportional to the temperature, therefore taking values from simulations and observations, we find that the gas density in superclusters may account for 17 - 52 % of missing baryons at low redshifts. A better understanding of the physical state of gas in the superclusters is required to accurately estimate the contribution of our measurements to missing baryons.