WHIM-hunting through cross-correlation of optical and SZ effect data in the Virgo cluster filaments (2210.02831v2)

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.