AGN radio-mode feedback onto giant-molecular cloud associations in Fornax A

ABSTRACT :
AGN feedback onto the interstellar medium (ISM) has been considered as a key physical process that regulates star formation in galaxies. Nevertheless, the immediate roles of radio-mode feedback on molecular gas, the material for star formation, remain unclear. We explore the physical properties of giant-molecular-cloud associations (GMAs) in NGC1316, a.k.a. Fornax A, one of the nearby radio galaxies with prominent radio lobes and a nuclear jet. In previous studies, abundant molecular gas (~5x10^8 Msun) was found at the vicinity of the nuclear jet based on the ALMA ACA observation (Morokuma-Matsui+2019, PASJ, 71, 85). The kpc-scale data shows a complex molecular-gas distribution including a shell, a blob and multiple clump structures. With our new ALMA CO(J=1-0) data with a beam size of ~100 pc, we identify 52 GMAs using a cloud-finding tool, PYCPROPS. A typical radius and velocity dispersion of the NGC1316 GMAs are R~200 pc and σ~30 km/s, respectively. These values are higher than those of normal star-forming galaxies in the PHANGS project (~70 pc and ~7 km/s, Rosolowsky+2021). Most NGC1316 GMAs has a virial parameter, α_vir of >2, suggesting they are not gravitationally bound, while the PHANGS galaxies have α_vir of ~1.0. This result suggests that star formation in NGC1316 is suppressed due to the turbulence injection by the jet-ISM interaction.