Shaken Snow Globes: Kinematic Tracers of the Multiphase Condensation Cascade in Massive Galaxies, Groups, and Clusters

Abstract

We propose a novel method to constrain turbulence and bulk motions in massive galaxies, galaxy groups and clusters, exploring both simulations and observations. As emerged in the recent picture of the top-down multiphase condensation, the hot gaseous halos are tightly linked to all other phases in terms of cospatiality and thermodynamics. While hot halos (∼ 10 7 K) are perturbed by subsonic turbulence, warm (∼ 10 4 K) ionized and neutral filaments condense out of the turbulent eddies. The peaks condense into cold molecular clouds (< 100 K) raining in the core via chaotic cold accretion (CCA). We show all phases are tightly linked in terms of the ensemble (wide-aperture) velocity dispersion along the line of sight. The correlation arises in complementary long-term AGN feedback simulations and high-resolution CCA runs, and is corroborated by the combined Hitomi and new Integral Field Unit measurements in Perseus cluster. The ensemble multiphase gas distributions (from UV to radio band) are characterized by substantial spectral line broadening (σ v,los ≈ 100 -200 km s −1 ) with mild line shift. On the other hand, pencil-beam detections (as HI absorption against the AGN backlight) sample the small-scale clouds displaying smaller broadening and significant line shift up to several 100 km s −1 (for those falling toward the AGN), with increased scatter due to the turbulence intermittency. We present new ensemble σ v,los of the warm Hα+[NII] gas in 72 observed cluster/group cores: the constraints are consistent with the simulations and can be used as robust proxies for the turbulent velocities, in particular for the challenging hot plasma (otherwise requiring extremely long X-ray exposures). Finally, we show the physically motivated criterion C ≡ t cool /t eddy ≈ 1 best traces the condensation extent region and presence of multiphase gas in observed clusters and groups. The ensemble method can be applied to many available spectroscopic datasets and can substantially advance our understanding of multiphase halos in light of the next-generation multiwavelength missions.

Constraining cold accretion on to supermassive black holes: molecular gas in the cores of eight brightest cluster galaxies revealed by joint CO and CN absorption

“…8. In the chaotic cold accretion scenario, most clouds are expected to drift in the large-scale turbulent field (with low v cen ), while only a few outliers are found to reach velocities of several 100 km s −1 (see Gaspari et al 2018), which is consistent with our findings here. Nevertheless, the number of detections these conclusions are based upon remains small.…”

“…Therefore, the lack of absorption lines in the systems listed above does not necessarily mean that significant masses of cold molecular gas are absent. Overall, the eight absorbing systems we find from the sample of 18 observed implies a line of sight covering fraction in line with expectations and is similar to that predicted by accretion simulations, such as those by Gaspari et al (2018).…”

“…9, the distribution of blue points (our ALMA detections in Table 5) is consistent with that of CO and HI clouds in other galaxies (red and yellow; see Gaspari et al 2018), as well as with the simulated 1-3σ contours predicted by chaotic cold accretion simulations. Regarding bulk motions, the log mean and dispersion for our points is log v shift 1.9 ± 0.5, which is comparable to that of the points observed in Gaspari et al (2018) simulations with log v shift 2.0 ± 0.5. In terms of the turbulence, the log mean and dispersion for our points is log σ v 1.6 ± 0.5, which is analogous to that of the points observed in Gaspari et al (2018) simulations.…”

“…Although many theoretical works hypothesise about at least in part, as a population of relatively small clouds in the few hundred parsecs around the cores of massive brightest cluster galaxies (e.g. Pizzolato & Soker 2005;Gaspari et al 2015;Gaspari et al 2018). The ensemble of molecular gas clouds which make up this reservoir are expected to undergo inelastic collisions, causing them to lose angular momentum and be funneled into the few hundred parsecs surrounding the supermassive black hole, eventually providing it with fuel.…”

Linking macro-, meso- and microscales in multiphase AGN feeding and feedback

“…While X-ray telescopes detect ubiquitous AGN feedback imprints in the gas-rich ICM/IGrM of massive/central galaxies, evidences in spiral/isolated galaxies and dwarfs are still difficult to acquire (due to the low photon count). Does the CCA-driven self-regulation scale down to the poor systems 16,17 , given that the related fundamental physics is expected to operate in all environments?…”