AGN Feedback and the Development of Dusty Multiphase Gas in X-ray Emitting Elliptical Galaxies

TL;DR

This study explores how AGN feedback influences the formation and properties of dusty, multiphase gas in elliptical galaxies, revealing the spatial and kinematic relationships among hot X-ray gas, dust, and molecular clouds.

Contribution

It provides new insights into the connection between AGN-driven X-ray cavities and cold dusty gas formation, highlighting the role of feedback in shaping dust grain properties in galaxy environments.

Findings

Dust clouds are located at X-ray cavity rims.

Molecular and ionized gases are dynamically linked.

Regions with mixed-phase gas have smaller Rv values.

Abstract

This paper investigates the physical and kinematic properties of dust-rich regions in a small sample of group-centered elliptical galaxies, emphasizing their connection with the hot X-ray emitting gas and detailed dust grain characteristics. Comprehensive multi-wavelength data, including H-alpha and CO emission detected by MUSE and ALMA, demonstrate the presence of dust clouds embedded within complex, hot X-ray atmospheres shaped by AGN feedback. X-ray images show bubbles and cavities surrounded by bright rims. We find that dust regions containing molecular gas traced by CO are preferentially located at the rims of these X-ray cavities, suggesting that AGN-driven outflows enhance the condensation of cold, dusty gas at these compressive interfaces. Kinematic measurements indicate that molecular and ionized gas phases are dynamically and spatially linked, supporting the framework of a multiphase medium arising from the top-down condensation rain in the hot plasma and related chaotic cold accretion. Crucially, spatial variations in the total-to-selective extinction ratio Rv show that regions where dust, CO, and H-alpha emission coincide exhibit notably smaller Rv values, implying steeper extinction curves and the predominance of smaller or less evolved dust grains within these mixed-phase environments. This contrasts with larger Rv values found elsewhere in the dust clouds, suggesting grain growth or survival mechanisms within shielded cold gas.