paper

An Elusive Population of Massive Disk Galaxies Hosting Double-lobed Radio-loud AGNs

arXiv:2210.11724 · doi:10.3847/1538-4357/ac9cd5

Abstract

It is commonly accepted that radio-loud active galactic nuclei are hosted exclusively by giant elliptical galaxies. We analyze high-resolution optical Hubble Space Telescope images of a sample of radio galaxies with extended double-lobed structures associated with disk-like optical counterparts. After systematically evaluating the probability of chance alignment between the radio lobes and the optical counterparts, we obtain a sample of 18 objects likely to have genuine associations. The host galaxies have unambiguous late-type morphologies, including spiral arms, large-scale dust lanes among the edge-on systems, and exceptionally weak bulges, as judged by the low global concentrations, small global Sérsic indices, and low bulge-to-total light ratios (median ). With a median Sérsic index of 1.4 and low effective surface brightnesses, the bulges are consistent with being pseudo bulges. The majority of the hosts have unusually large stellar masses (median ) and red optical colors (median mag), consistent with massive, quiescent galaxies on the red sequence. We suggest that black hole mass (stellar mass) plays a fundamental role in launching large-scale radio jets, and that the rarity of extended radio lobes in late-type galaxies is the consequence of the steep stellar mass function at the high-mass end. The disk radio galaxies have mostly Fanaroff-Riley type II morphologies yet lower radio power than sources of a similar type traditionally hosted by ellipticals. The radio jets show no preferential alignment with the minor axis of the galactic bulge or disk, apart from a possible mild tendency for alignment among the most disk-dominated systems.

33 pages, 12 figures, 5 tables; accepted for publication in ApJ

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