Discovery of large-scale diffuse radio emission in low-mass galaxy cluster Abell 1931
Date Issued
2018
Author(s)
Brüggen, M.
•
Rafferty, D.
•
•
van Weeren, R. J.
•
Shimwell, T.
•
Intema, H.
•
Röttgering, H.
•
•
Di Gennaro, G.
•
Savini, F.
•
Wilber, A.
•
O'Sullivan, S.
•
Ensslin, T. A.
•
•
Hoeft, M.
Abstract
Extended, steep-spectrum radio synchrotron sources are pre-dominantly found
in massive galaxy clusters as opposed to groups. LOFAR Two-Metre Sky Survey
images have revealed a diffuse, ultra-steep spectrum radio source in the
low-mass cluster Abell 1931. The source has a fairly irregular morphology with
a largest linear size of about 550 kpc. The source is only seen in LOFAR
observations at 143 MHz and GMRT observations at 325 MHz. The spectral index of
the total source between 143 MHz and 325 MHz is $\alpha_{143}^{325} = -2.86 \pm
0.36$. The source remains invisible in Very Large Array (1-2 GHz) observations
as expected given the spectral index. Chandra X-ray observations of the cluster
revealed a bolometric luminosity of $L_X = (1.65 \pm 0.39) \times 10^{43}$ erg
s$^{-1}$ and a temperature of $2.92_{-0.87}^{+1.89}$ keV which implies a mass
of around $\sim 10^{14} M_{\odot}$. We conclude that the source is a remnant
radio galaxy that has shut off around 200 Myr ago. The brightest cluster
galaxy, a radio-loud elliptical galaxy, could be the source for this extinct
source. Unlike remnant sources studied in the literature, our source has a
steep spectrum at low radio frequencies. Studying such remnant radio galaxies
at low radio frequencies is important for understanding the scarcity of such
sources and their role in feedback processes.
Volume
477
Issue
3
Start page
3461
Issn Identifier
0035-8711
Ads BibCode
2018MNRAS.477.3461B
Rights
open.access
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