Probing multiphase gas in local massive elliptical galaxies via multiwavelength observations

Abstract

We investigate the cold and warm gas content, kinematics, and spatial distribution of six local massive elliptical galaxies to probe the origin of the multiphase gas in their atmospheres. We report new observations, including SOFIA [CII], ALMA CO, MUSE H$\alpha$+[NII] and VLA radio observations. These are complemented by a large suite of multiwavelength archival datasets, including thermodynamical properties of the hot gas and radio jets, which are leveraged to investigate the role of AGN feeding/feedback in regulating the multiphase gas content. Our galaxy sample shows a significant diversity in cool gas content, spanning filamentary and rotating structures. In our non-central galaxies, the distribution of such gas is often concentrated, at variance with the more extended features observed in central galaxies. Misalignment between the multiphase gas and stars suggest that stellar mass loss is not the primary driver. A fraction of the cool gas might be acquired via galaxy interactions, but we do not find quantitative evidence of mergers in most of our systems. Instead, key evidence supports the origin via condensation out of the diffuse halo. Comparing with Chaotic Cold Accretion (CCA) simulations, we find that our cool gas-free galaxies are likely in the overheated phase of the self-regulated AGN cycle, while for our galaxies with cool gas the k-plot and AGN power correlation corroborate the phase of CCA feeding in which the condensation rain is triggering more vigorous AGN heating. The related C-ratio further shows that central/non-central galaxies are expected to generate an extended/inner rain, consistent with our sample.