Gas Condensation in Brightest Group Galaxies Unveiled with MUSE

While a consensus has emerged that cold gas in central cluster galaxies forms through the cooling of the hot atmosphere, less attention has been paid to the central group galaxies. This talk will present new Multi-Unit Spectroscopic Explorer (MUSE) comments that trace the warm ionized gas for a sample of 18 nearby Brightest Group Galaxies (BGGs) optically selected. Our MUSE observations reveal a distribution of morphologies from complex networks of filaments to extended (>10 kpcs) and compact (<3 kpc) disk-dominated structures. Some rotating disks show rings and elongated structures arising from the central disk. The kinematics of the stellar component is mainly rotation-dominated, which is very different from the disturbed kinematics and distribution found in the filamentary sources. The ionized gas is kinematically decoupled from the stellar component for most systems, suggesting an external origin for the gas. By exploring the thermodynamical properties of the X-ray atmospheres, we find that the filamentary structures and compact disks are found in systems with small central entropy values and tcool/teddy ratios. This suggests that, like for Brightest Cluster Galaxies (BCGs) in cool core clusters, the ionized filaments and the cold gas associated are likely formed from hot halo gas condensations, consistently with the Chaotic Cold Accretion simulations. We note that gaseous rotating disks are more frequent than in BCGs. As suggested by some sources of the present sample, an explanation for the origin of the gas in those objects is a contribution to gas fueling by wet-mergers or group satellites, as qualitatively hinted by some sources of the present sample.