Kavli Affiliate: Luis C. Ho
| First 5 Authors: Sanna Gulati, Sanna Gulati, , ,
| Summary:
We present results from uGMRT 685 MHz observations of 87 QSOs belonging to
the Palomar Green (PG) quasar sample with $z<0.5$. Radio emission is detected
in all sources except for 3 radio-quiet (RQ) sources, viz., PG 0043+039, PG
1121+422, and PG 1552+085. The radio-loud (RL) $-$ RQ dichotomy persists at 685
MHz with only 1 source, PG 1216+069, changing its classification from RQ to RL.
Approximately 1/3 of the detected RQ quasars display AGN-dominated radio
emission while the rest may show additional contributions from stellar-related
processes. Consistent with this, the RL and RQ quasars occupy distinct tracks
on the `fundamental plane’ of black hole activity. We find that RL quasars have
$log_10(L_685,mathrmMHz/mathrmW,Hz^-1) > 25.5$, while RQ quasars
have $log_10(L_685,mathrmMHz/mathrmW,Hz^-1) <23.5$.
Furthermore, the radio sizes display the RQ$-$RL divide as well with RQ sources
typically having sizes $lesssim30$ kpc, with only 16 ($sim22$%) RQ sources
having sizes between 30 and 100 kpc where there is an overlap with RL quasar
sizes. A strong correlation exists between 685 MHz radio luminosity and black
hole mass which is tightened when accretion rate is considered, highlighting
the important role played by the accretion rate and accretion disk structure in
jet production. We found no difference in the minimum-energy magnetic field
strengths of the radio cores of RL and RQ quasars; however, different
assumptions of source volume and volume filling factors may apply.
High-resolution X-ray observations and radio-X-ray flux comparisons are needed
to independently test the `magnetic flux paradigm’.
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