2024MNRAS.535.2173F

Cooling flows are common in galaxy clusters which have cool cores. The soft X-ray emission below 1 keV from the flows is mostly absorbed by cold dusty gas within the central cooling sites. Further evidence for this process is presented here through a more detailed analysis of the nearby Centaurus cluster and some additional clusters. Predictions of JWST near and mid-infrared spectra from cooling gas are presented. [Ne VI] emission at $7.65\,\mu$m should be an important diagnostic of gas cooling between 6 and $1.5\times 10^5{\rm \, K}$. The emerging overall picture of hidden cooling flows is explored. The efficiency of active galactic nucleus feedback in reducing the total cooling rate in cool cores is shown to be above 50 per cent for many clusters but is rarely above 90 per cent. The reduction is mostly in outer gas. Cooling dominates in elliptical galaxies and galaxy groups that have mass flow rates below about $15{{\rm \, {\rm M}_{\odot }}{\rm \, yr}^{-1}\, }$ and in some massive clusters where rates can exceed $1000{{\rm \, {\rm M}_{\odot }}{\rm \, yr}^{-1}\, }.$