WHIM-hunting through cross-correlation of optical and SZ effect data in the Virgo cluster filaments

TL;DR

This study searches for the warm-hot intergalactic medium (WHIM) in Virgo cluster filaments by cross-correlating optical galaxy data with SZ effect maps, setting upper limits on WHIM density consistent with simulations.

Contribution

It introduces a novel cross-correlation method combining optical and SZ data to constrain the WHIM in Virgo filaments, providing the first such upper limit analysis.

Findings

No significant cross-correlation detected.

Upper limit on WHIM density is < 4×10⁻⁴ cm⁻³.

Results align with theoretical WHIM predictions.

Abstract

Context. The physical state of most of the baryonic matter in the local universe is unknown, which is commonly referred to as the ``missing baryon problem". It is theorized that at least half of these missing baryons are in a warm-hot, low-density phase outside of the virialized dark-matter halos. Aims. We make an attempt to find the signature of this warm-hot intergalactic medium (WHIM) phase in the filaments of the nearby Virgo cluster by using optical and Sunyaev-Zeldovich effect data. Methods. Specifically, we use a filament-galaxy catalog created from the HyperLeda database and an all-sky Compton-y map extracted from the Planck satellite data for 2-dimensional cross-correlation analysis by applying spherical harmonics transform. Significance test is based on the null-test simulations which exploits advanced cut-sky analysis tools for a proper map reconstruction. To place upper limits on the WHIM density in the Virgo filaments, realistic baryonic density modelling within the cosmic filaments is done based on state-of-the-art hydro-simulations, and it's done within the signal-boosting routine. Results. The cross-correlation signal is found to be too dim compared to the noise level in the Planck y-map. At 3$\sigma$ confidence level, the upper limit on volume-average WHIM density turns out to be $\left\langle n_e \right\rangle \lt 4\times10^{-4} cm^{-3}$, which is indeed consistent with the WHIM parameter space as predicted from simulations.