Taking snapshots of the jet-ISM interplay: The case of PKS0023-26

TL;DR

This study uses high-resolution ALMA observations to investigate how a young radio source interacts with the molecular gas in its host galaxy, revealing different coupling modes that influence galaxy evolution.

Contribution

It provides detailed observational evidence of the changing interaction modes between radio jets and the interstellar medium in PKS0023-26.

Findings

Inner regions show jet-cloud interactions with broad emission profiles.

Outer regions exhibit gas avoiding radio lobes with lower velocity dispersion.

The AGN impacts star formation indirectly through jet-ISM coupling.

Abstract

We present high angular resolution ALMA CO(2-1) and 1.7 mm continuum observations of the far-infrared-bright galaxy PKS0023-26, which hosts a young radio source and a luminous optical AGN. Although young, the powerful radio source has grown to a size of a few kpc, making it capable of affecting the ISM of the host galaxy. We detect an extended distribution of molecular gas with a mass between 0.3 and 3x10^10 Msun, depending on the CO conversion factor. The gas has a maximum extent of ~24 kpc and is distributed asymmetrically wrt the radio galaxy. Overall, the observed properties are reminiscent of molecular structures observed in some galaxy clusters. However, in the inner few kpc, the kinematics of the gas appears to be affected by the radio source. In the central regions we observe the brightest emission and the broadest profiles (FWZI ~ 500 km/s), which indicate a direct interaction of the jet with dense clouds. On larger scales, the molecular gas appears to avoid the radio lobes and gas with smaller velocity dispersion (FWZI ~350 km/s) is observed around the them. There, the gas appears to be affected by the expanding cocoon surrounding the radio source, dispersing and heating preexisting molecular clouds. The data suggest that the mode of coupling between radio jets and ISM changes from an outflowing phase in the inner regions to a maintenance phase at larger radii. This reveals that on galaxy scales the impact of the AGN is not limited to outflows. With a star-formation rate of 25 Msun/yr, PKS0023-26 is located on the SFR-M* relation for star forming galaxies. The AGN does not appear to have, at present, a major impact on the overall level of star formation of the host galaxy. However, as the jet and lobes expand throughout the galaxy, they will carry enough energy to prevent further gas cooling and/or to inject turbulence and affect future star formation.