VLBA21B-033

Unveiling the nature of a fueling flow in CygnusA

Abstract

Molecular gas is a direct probe that can trace fueling and feedback processes in the central (pc/sub-pc) regions of AGN. However, the physical and geometric properties of the gas are poorly understood, mainly due to the lack of spatial resolution. For radio AGN, the circum-nuclear gas can be studied through molecular absorption line VLBI, with the central bright continuum source used as the background source. Recently, we detected excited 13 GHz OH absorption in the core region of Cygnus A using high sensitivity VLBI observations (HSA). This detection of redshifted OH absorption on sub-pc scales and the velocity pattern suggest a fueling flow from a Torus. However, the high observing frequency (13 GHz) and small beam size limit absorption detection to small radii around the radio core. At lower frequencies, the jet is brighter so that an extended fueling flow can be unveiled. This proposal aims at imaging two additional OH absorptions lines at 6 cm and at larger radii along the jet. The study of multiple OH transitions will help to discriminate between accretion flow and torus models and unveil the circum-nuclear gas properties around the SMBH in the center of the archetypal radio-galaxy Cygnus A.

Investigators

Name	Institution
GBT Operator	Green Bank Observatory
Chris Henkel	Max-Planck-Institut für Radioastronomie
Tony Zensus	National Radio Astronomy Observatory; Max-Planck-Institut für Radioastronomie
Uwe Bach	Max-Planck-Institut für Radioastronomie
Violette Impellizzeri	National Radio Astronomy Observatory; Leiden, University of; Joint ALMA Observatory
Biagina Boccardi	Max-Planck-Institut für Radioastronomie
Thomas Krichbaum	Max-Planck-Institut für Radioastronomie
Dongjin Kim *	Massachusetts Institute of Technology

* indicates the PI