LOFAR discovery and wide-band characterisation of an ultra-steep spectrum AGN radio remnant associated with Abell 1318
Journal article, 2024
We present the discovery of a very extended (550 kpc) and low-surface-brightness (3.3 µJy arcsec−2 at 144 MHz) radio emission region in Abell 1318. These properties are consistent with its characterisation as an active galactic nucleus (AGN) remnant radio plasma, based on its morphology and radio spectral properties. We performed a broad-band (54–1400 MHz) radio spectral index and curvature analysis using LOFAR, uGMRT, and WSRT-APERTIF data. We also derived the radiative age of the detected emission, estimating a maximum age of 250 Myr. The morphology of the source is remarkably intriguing, with two larger, oval-shaped components and a thinner, elongated, and filamentary structure in between, plausibly reminiscent of two aged lobes and a jet. Based on archival Swift as well as SDSS data we performed an X-ray and optical characterisation of the system, whose virial mass was estimated to be ∼7.4 × 1013 M. This places A1318 in the galaxy group regime. Interestingly, the radio source does not have a clear optical counterpart embedded in it, thus, we propose that it is most likely an unusual AGN remnant of previous episode(s) of activity of the AGN hosted by the brightest group galaxy (∼2.6 × 1012 M), which is located at a projected distance of ∼170 kpc in the current epoch. This relatively high offset may be a result of IGrM sloshing sourced by a minor merger. The filamentary morphology of the source may suggest that the remnant plasma has been perturbed by the system dynamics, however, only future deeper X-ray observations will be able to address this question.
galaxies: active
radio continuum: galaxies
Author
A. Shulevski
Leiden University
Anton Pannekoek Institute for Astronomy
University of Groningen
Netherlands Institute for Radio Astronomy (ASTRON)
M. Brienza
University of Bologna
Istituto nazionale di astrofisica (INAF)
F. Massaro
University of Turin
R. Morganti
Netherlands Institute for Radio Astronomy (ASTRON)
University of Groningen
H. T. Intema
Leiden University
T. Oosterloo
Netherlands Institute for Radio Astronomy (ASTRON)
University of Groningen
F. De Gasperin
Istituto di Radioastronomia
University of Hamburg
K. Rajpurohit
Istituto di Radioastronomia
Harvard-Smithsonian Center for Astrophysics
University of Bologna
T. Pasini
University of Hamburg
A. M. Kutkin
Netherlands Institute for Radio Astronomy (ASTRON)
D. Vohl
Anton Pannekoek Institute for Astronomy
Netherlands Institute for Radio Astronomy (ASTRON)
Elizabeth A.K. Adams
University of Groningen
Netherlands Institute for Radio Astronomy (ASTRON)
B. Adebahr
Ruhr-Universität Bochum
M. Brueggen
University of Hamburg
Kelley Michelle Hess
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Netherlands Institute for Radio Astronomy (ASTRON)
Spanish National Research Council (CSIC)
M. Loose
Netherlands Institute for Radio Astronomy (ASTRON)
L. C. Oostrum
Netherlands eScience Center
Anton Pannekoek Institute for Astronomy
Netherlands Institute for Radio Astronomy (ASTRON)
J. Ziemke
University of Oslo
Netherlands Institute for Radio Astronomy (ASTRON)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 682 A171Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/202346824