The TELPERION Survey for Distant [O III] Clouds around Luminous and Hibernating AGN

• Main Authors: Keel, William C, Moiseev, Alexei, Kozlova, D. V, Ikhsanova, A. I, Oparin, D. V, Uklein, R. I, Smirnova, A. A, Eselevich, M. V
• Format: Journal Article
• Language: English
• Published: 14-12-2021
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.2112.07084

We present a narrowband [O III] imaging survey of 111 AGN hosts and 17
merging-galaxy systems, in search of distant extended emission-line regions
(EELRs) around AGN (either extant or faded). Our data reach deeper than
detection from the broadband SDSS data, and cover a wider field than some early
emission-line surveys used to study extended structure around AGN.
Spectroscopic followup confirms two new distant AGN-ionized clouds, in the
merging systems NGC 235 and NGC 5514, projected at 26 and 75 kpc from the
nuclei (respectively). We also recover the previously-known region in NGC 7252.
These results strengthen the connection between EELRs and tidal features;
kinematically quiescent distant EELRs are virtually always photoionized tidal
debris. We see them in ~10% of the galaxies in our sample with tidal tails.
Energy budgets suggest that the AGN in NGC 5514 has faded by >3 times during
the extra light-travel time ~250,000 years from the nucleus to the cloud and
then to the observer; strong shock emission in outflows masks the optical
signature of the AGN. For NGC 235 our data are consistent with but do not
unequivocally require variation over ~85,000 years. In addition to these very
distant ionized clouds, luminous and extensive line emission within four
galaxies - IC 1481, ESO 362-G08, NGC 5514, and NGC 7679. IC 1481 shows apparent
ionization cones, a rare combination with its LINER AGN spectrum. In NGC 5514,
we measure a 7-kpc shell expanding at ~370 km/s west of the nucleus.