The radio emission from Active Galactic Nuclei. (arXiv:2104.04519v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Radcliffe_J/0/1/0/all/0/1">J. F. Radcliffe</a> (1,2,3), <a href="http://arxiv.org/find/astro-ph/1/au:+Barthel_P/0/1/0/all/0/1">P. D. Barthel</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Garrett_M/0/1/0/all/0/1">M. A. Garrett</a> (3,4), <a href="http://arxiv.org/find/astro-ph/1/au:+Beswick_R/0/1/0/all/0/1">R. J. Beswick</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Thomson_A/0/1/0/all/0/1">A. P. Thomson</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Muxlow_T/0/1/0/all/0/1">T. W. B. Muxlow</a> (3) ((1) University of Groningen, NL, (2) University of Pretoria, SA, (3) University of Manchester, UK, (4) Leiden Observatory, NL)
For nearly seven decades astronomers have been studying active galaxies, that
is to say galaxies with actively accreting central supermassive black holes,
AGN. A small fraction of these are characterized by luminous, powerful radio
emission: this class is known as radio-loud. A substantial fraction, the
so-called radio-quiet AGN population, displays intermediate or weak radio
emission. However, an appreciable fraction of strong X-rays emitting AGN are
characterized by the absence of radio emission, down to an upper limit of about
$10^{-7}$ times the luminosity of the most powerful radio-loud AGN.
We wish to address the nature of these – seemingly radio-silent –
X-ray-luminous AGN and their host galaxies: is there any radio emission, and if
so, where does it originate? Focusing on the GOODS-N field, we examine the
nature of these objects employing stacking techniques on ultra-deep radio data
obtained with the JVLA. We combine these radio data with Spitzer far-infrared
data. We establish the absence, or totally insignificant contribution of
jet-driven radio-emission in roughly half of the otherwise normal population of
X-ray luminous AGN, which appear to reside in normal star-forming galaxies. We
conclude that AGN- or jet-driven radio emission is simply a mechanism that may
be at work or may be dormant in galaxies with actively accreting black holes.
The latter can be classified as radio-silent AGN.
For nearly seven decades astronomers have been studying active galaxies, that
is to say galaxies with actively accreting central supermassive black holes,
AGN. A small fraction of these are characterized by luminous, powerful radio
emission: this class is known as radio-loud. A substantial fraction, the
so-called radio-quiet AGN population, displays intermediate or weak radio
emission. However, an appreciable fraction of strong X-rays emitting AGN are
characterized by the absence of radio emission, down to an upper limit of about
$10^{-7}$ times the luminosity of the most powerful radio-loud AGN.
We wish to address the nature of these – seemingly radio-silent –
X-ray-luminous AGN and their host galaxies: is there any radio emission, and if
so, where does it originate? Focusing on the GOODS-N field, we examine the
nature of these objects employing stacking techniques on ultra-deep radio data
obtained with the JVLA. We combine these radio data with Spitzer far-infrared
data. We establish the absence, or totally insignificant contribution of
jet-driven radio-emission in roughly half of the otherwise normal population of
X-ray luminous AGN, which appear to reside in normal star-forming galaxies. We
conclude that AGN- or jet-driven radio emission is simply a mechanism that may
be at work or may be dormant in galaxies with actively accreting black holes.
The latter can be classified as radio-silent AGN.
http://arxiv.org/icons/sfx.gif
