Lensing and the Warm Hot Intergalactic Medium

TL;DR

This paper models the correlation between weak lensing and CMB data to understand the distribution and temperature of unbound intergalactic gas, providing constraints and methods to distinguish it from halo gas.

Contribution

It introduces a model for the gas in filaments using a log-normal distribution and analyzes its impact on lensing-CMB correlations, aiding in detecting unbound intergalactic gas.

Findings

Most correlation is from gas with overdensities 3-33

Upper limit of ~10^6 K on intergalactic medium temperature

Lensing-comptonization spectrum peaks at different scales than halo gas

Abstract

The correlation of weak lensing and Cosmic Microwave Anisotropy (CMB) data traces the pressure distribution of the hot, ionized gas and the underlying matter density field. The measured correlation is dominated by baryons residing in halos. Detecting the contribution from unbound gas by measuring the residual cross-correlation after masking all known halos requires a theoretical understanding of this correlation and its dependence with model parameters. Our model assumes that the gas in filaments is well described by a log-normal probability distribution function, with temperatures $10^{5-7}$K and overdensities $\xi\le 100$. The lensing-comptonization cross-correlation is dominated by gas with overdensities in the range $\xi\approx[3-33]$; the signal is generated at redshifts $z\le 1$. If only 10\% of the measured cross-correlation is due to unbound gas, then the most recent measurements set an upper limit of $\bar{T}_e\lesssim 10^6$K on the mean temperature of Inter Galactic Medium. The amplitude is proportional to the baryon fraction stored in filaments. The lensing-comptonization power spectrum peaks at a different scale than the gas in halos making it possible to distinguish both contributions. To trace the distribution of the low density and low temperature plasma on cosmological scales, the effect of halos will have to be subtracted from the data, requiring observations with larger signal-to-noise ratio than currently available.