J/A+A/690/A160 MRC 2011-298 radio images (Bruno+, 2024)
From 100 MHz to 10 GHz: Unveiling the spectral evolution of the X-shaped radio
galaxy in Abell 3670.
Bruno L., Brienza M., Zanichelli A., Gitti M., Ubertosi F., Rajpurohit K.,
Venturi T., Dallacasa D.
<Astron. Astrophys. 690, A160 (2024)>
=2024A&A...690A.160B 2024A&A...690A.160B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio
Keywords: radiation mechanisms: non-thermal -
galaxies: clusters: individual: Abell 3670 -
galaxies: individual: MRC 2011-298 - radio continuum: galaxies
Abstract:
X-shaped radio galaxies (XRGs) are characterised by two pairs of
misaligned lobes: active lobes hosting radio jets and the wings. None
of the formation mechanisms proposed thus far are able to exhaustively
reproduce the diverse features observed among XRGs. Emerging evidence
has proposed the existence of sub-populations of XRGs forming via
different processes.
The brightest cluster galaxy (BCG) in Abell 3670 (A3670) is a dumbbell
system hosting the XRG MRC 2011-298. The morphological and spectral
properties of this interesting XRG were first characterised based on
Karl G. Jansky Very Large Array (JVLA) data at 1-10GHz. In the present
work, we follow up on MRC 2011-298 with the upgraded Giant Metrewave
Radio Telescope (uGMRT) at 120-800MHz to further constrain its
properties and origin.
We carried out a detailed spectral analysis sampling different
spatial scales. Integrated radio spectra, spectral index maps, radio
colour-colour diagrams, and radiative age maps of both the active
lobes and prominent wings were employed to test the origin of the
source.
We confirm a progressive spectral steepening from the lobes to the
wings. The maximum radiative age of the source is ∼80Myr, with the
wings being older than the lobes by ≥30Myr in their outermost
regions.
The observed properties are in line with an abrupt reorientation of
the jets by ∼90deg from the direction of the wings to their present
position. This formation mechanism is further supported by the
comparison with numerical simulations in the literature, which
additionally highlight the role of hydrodynamic processes in the
evolution of large wings such as those of MRC 2011-298. It is
plausible that the coalescence of supermassive black holes could have
triggered the spin-flip of the jets. Moreover, we show that the
S-shape of the radio jets is likely driven by precession with a period
of P∼10Myr.
Description:
Images of MRC 2011-298 (Fig. 2 in the paper).
A3670 was observed with the uGMRT wide-band receiver (GMRT Wideband
Backend, GWB) in band 2 (120-220MHz), band 3 (250-450MHz), and band 4
(550-850MHz) for 8, 8, and 9 hours, respectively. Data were recorded
in channels of width 0.34, 1.1, and 1.6MHz each for band 2, band 3,
and band 4, respectively. Furthermore, the outdated narrow-band
receiver (GMRT Software Backend, GSB) was active during the
observations. Each observation includes pointings (∼10min) on 3C380
and 3C48, which were used as flux density scale calibrators.
Bruno et al. (2019A&A...631A.173B 2019A&A...631A.173B) first presented JVLA observations
of MRC 2011-298. We reprocessed these data with more sophisticated
calibration and imaging strategies to obtain higher quality im ages.
MRC 2011-298 was observed at 1-2GHz (L-band, CnB array configuration),
4-8GHz (C-band, both CnB and DnC array configurations), and 8-10GHz
(X-band, CnB array configuration) for ∼30min on-source each. In all
the observations, 3C48 and J2003-3251 were used as flux density scale
and phase calibrators, respectively. The data in CnB and DnC
configuration were recorded in 16 and 34 spectral windows,
respectively, each split into 64 channels.
The VLA Sky Survey (VLASS; Lacy et al., 2020PASP..132c5001L 2020PASP..132c5001L) is
observing the sky above a declination of -40° at 2-4GHz (S-band)
in B configuration. A number of snapshots of ∼10s have been mosaicked
to reach a typical noise level of 120uJy/beam at the nominal
resolution of 2.5".
Objects:
------------------------------------------------------------
RA (2000) DE Designation(s)
------------------------------------------------------------
20 14 17.00 -29 44 54.0 A3670 = ACO 3670
20 14 18.69 -29 42 36.4 MRC 2011-298 = [CAC2009] A3670
------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 170 7 List of fits images
fits/* . 7 Individual fits images
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 48 A21 "datime" Obs.date Observation date
50- 57 F8.3 MHz Freq Observed frequency
59- 62 I4 Kibyte size Size of FITS file
64- 95 A32 --- FileName Name of FITS file, in subdirectory fits
97-170 A74 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Luca Bruno, luca.bruno4(at)unibo.it
(End) Patricia Vannier [CDS] 26-Aug-2024