Kavli Affiliate: Claudio Ricci
| First 5 Authors: Arghajit Jana, Claudio Ricci, Sophie M. Venselaar, Chin-Shin Chang, Mai Liao
| Summary:
The origin of compact millimeter (mm) continuum emission from radio-quiet
AGNs (RQAGNs) is still not fully understood. Changing-state AGNs (CSAGNs)
display rapid and strong variability, which can allow us to investigate the
origin of the mm emission. We present here the results of the first study of
the mm continuum variability of a CSAGN using archival ALMA band 6 ($sim 230$
GHz) observations of NGC 1566 obtained in 2014-2023. We find a positive
correlation between the mm and X-ray flux with an intrinsic scatter of 0.05 dex
($1sigma$), suggesting a common origin. The mm spectral index ($alpha_{rm
mm}$) is found in the range of $0.13pm0.38$ to $-0.26pm0.53$, consistent with
a compact optically thick synchrotron source. No significant correlation was
found between the $alpha_{rm mm}$ and the mm flux. The mm/X-ray ratio also
shows no clear link to the Eddington ratio but is higher in the low-accretion
state. We discuss several scenarios about the origin of the mm emission in NGC
1566. We find that synchrotron emission in the magnetized X-ray corona appears
to be the most probable origin of mm emission, confirming that mm emission can
be used as a tracer of AGN activity in RQAGNs.
| Search Query: ArXiv Query: search_query=au:”Claudio Ricci”&id_list=&start=0&max_results=3