A Uniformly Selected Sample of Low-mass Black Holes in Seyfert 1 Galaxies. III. Radio sources from the SKA pathfinders and beyond. (arXiv:2401.15895v1 [astro-ph.GA])

A Uniformly Selected Sample of Low-mass Black Holes in Seyfert 1 Galaxies. III. Radio sources from the SKA pathfinders and beyond. (arXiv:2401.15895v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Wu_J/0/1/0/all/0/1">Jin-Zhi Wu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dong_X/0/1/0/all/0/1">Xiao-Bo Dong</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Qian_L/0/1/0/all/0/1">Lei Qian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_W/0/1/0/all/0/1">Wen-Juan Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xie_F/0/1/0/all/0/1">Fu-Guo Xie</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Peng_B/0/1/0/all/0/1">Bo Peng</a>

Occupying the intermediate-mass regime of the accretion–jet parameter space,
radio continuum emission from active galactic nuclei with black hole mass M_BH
<~ 10^6 Msun (low-mass AGNs) is a valuable probe to the physics of relativistic
jets. Yet the number of low-mass AGNs with radio detection is rather limited so
far (~ 40 in total). In this work we make two efforts to search for radio
counterparts for the largest sample of optically selected low-mass AGNs. First,
we collect counterparts from the recent data releases of SKA pathfinders such
as LOFAR Two-metre Sky Survey (LoTSS). Additionally, we deeply mine in Faint
Images of the Radio Sky at Twenty-Centimeters (FIRST), fitting the FIRST images
of the optical AGNs with an elaborate procedure optimized to detect faint radio
sources. We have obtained 151 radio sources (mainly from the SKA pathfinders),
including 102 new reliable sources (S/N >= 5) and 23 new candidates (3.5 <= S/N
< 5). The majority of these new sources (119 of 125) have flux densities lower
than the threshold of the official FIRST catalog. The new sources have
rest-frame 20 cm power (P_20cm) from 1.98 x 10^20 to 1.29 x 10^23 W/Hz. For
low-z Seyfert galaxies P_20cm correlates with M_BH intrinsically and
positively, yet only marginally with Eddington ratio L/L_EDD. In terms of the
logN–logS relation for the expanding Universe, the limiting flux density for
the completeness of our LoTSS sources turns out to be 0.45 mJy at 1.4 GHz;
i.e., complete to such a flux-density level that is four times deeper than the
official FIRST catalog.

Occupying the intermediate-mass regime of the accretion–jet parameter space,
radio continuum emission from active galactic nuclei with black hole mass M_BH
<~ 10^6 Msun (low-mass AGNs) is a valuable probe to the physics of relativistic
jets. Yet the number of low-mass AGNs with radio detection is rather limited so
far (~ 40 in total). In this work we make two efforts to search for radio
counterparts for the largest sample of optically selected low-mass AGNs. First,
we collect counterparts from the recent data releases of SKA pathfinders such
as LOFAR Two-metre Sky Survey (LoTSS). Additionally, we deeply mine in Faint
Images of the Radio Sky at Twenty-Centimeters (FIRST), fitting the FIRST images
of the optical AGNs with an elaborate procedure optimized to detect faint radio
sources. We have obtained 151 radio sources (mainly from the SKA pathfinders),
including 102 new reliable sources (S/N >= 5) and 23 new candidates (3.5 <= S/N
< 5). The majority of these new sources (119 of 125) have flux densities lower
than the threshold of the official FIRST catalog. The new sources have
rest-frame 20 cm power (P_20cm) from 1.98 x 10^20 to 1.29 x 10^23 W/Hz. For
low-z Seyfert galaxies P_20cm correlates with M_BH intrinsically and
positively, yet only marginally with Eddington ratio L/L_EDD. In terms of the
logN–logS relation for the expanding Universe, the limiting flux density for
the completeness of our LoTSS sources turns out to be 0.45 mJy at 1.4 GHz;
i.e., complete to such a flux-density level that is four times deeper than the
official FIRST catalog.

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