2017MNRAS.469.2423M

We present a Chandra study of the hot intragroup medium of the galaxy group NCG 2563. The Chandra mosaic observations, with a total exposure time of ∼430 ks, allow the gas density to be detected beyond R₂₀₀ and the gas temperature out to 0.75 R₂₀₀. This represents the first observational measurement of the physical properties of a poor groups beyond R₅₀₀. By capitalizing on the exquisite spatial resolution of Chandra that is capable to remove unrelated emission from point sources and substructures, we are able to radially constrain the inhomogeneities of gas ('clumpiness'), gas fraction, temperature and entropy distribution. Although there is some uncertainty in the measurements, we find evidences of gas clumping in the virialization region, with clumping factor of about 2-3 at R₂₀₀. The gas clumping-corrected gas fraction is significantly lower than the cosmological baryon budget. These results may indicate a larger impact of the gas inhomogeneities with respect to the prediction from hydrodynamic numerical simulations, and we discuss possible explanations for our findings.