Misc,
A Multi-wavelength Study of the Turbulent Central Engine of the Low-mass AGN hosted by NGC404
(Jul 7, 2017)
Abstract
The nearby dwarf galaxy NGC404 harbors a low-luminosity active galactic
nucleus (AGN) powered by the lowest-mass (< 150,000 solar-masses) central
massive black hole (MBH) with a dynamical mass constraint currently known, thus
providing a rare low-redshift analog to the MBH "seeds" that formed in the
early Universe. Here, we present new imaging of the nucleus of NGC404 at 12-18
GHz with the Karl G. Jansky Very Large Array (VLA) and observations of the
CO(2-1) line with the Atacama Large Millimeter/Submillimeter Array (ALMA). For
the first time, we have successfully resolved the nuclear radio emission,
revealing a centrally peaked, extended source spanning 17 pc. Combined with
previous VLA observations, our new data place a tight constraint on the radio
spectral index and indicate an optically-thin synchrotron origin for the
emission. The peak of the resolved radio source coincides with the dynamical
center of NGC404, the center of a rotating disk of molecular gas, and the
position of a compact, hard X-ray source. We also present evidence for shocks
in the NGC404 nucleus from archival narrowband HST imaging, Chandra X-ray data,
and Spitzer mid-infrared spectroscopy, and discuss possible origins for the
shock excitation. Given the morphology, location, and steep spectral index of
the resolved radio source, as well as constraints on nuclear star formation
from the ALMA CO(2-1) data, we find the most likely scenario for the origin of
the radio source in the center of NGC404 to be a radio outflow associated with
a confined jet driven by the active nucleus.
