J/A+A/658/A6 3C293 high and low resolution maps (Kukreti+, 2022)
Unmasking the history of 3C 293 with LOFAR sub-arcsecond imaging.
Kukreti P., Morganti R., Shimwell T.W., Morabito L.K., Beswick R.J.,
Brienza M., Hardcastle M.J., Sweijen F., Jackson N., Miley G.K., Moldon J.,
Oosterloo T., de Gasperin F.
<Astron. Astrophys. 658, A6 (2022)>
=2022A&A...658A...6K 2022A&A...658A...6K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; Radio continuum
Keywords: galaxies: active - radio continuum: galaxies -
galaxies: individual: 3C 293 - techniques: high angular resolution
Abstract:
Active galactic nuclei (AGNs) show episodic activity, which can be
evident in galaxies that exhibit restarted radio jets. These restarted
jets can interact with their environment, leaving signatures on the
radio spectral energy distribution. Tracing these signatures is a
powerful way to explore the life of radio galaxies. This requires
resolved spectral index measurements over a broad frequency range
including low frequencies. We present such a study for the radio
galaxy 3C293, which has long been thought to be a restarted galaxy on
the basis of its radio morphology. Using the International LOFAR
telescope (ILT) we probed spatial scales as fine as ∼0.2-arcsec at
144MHz, and to constrain the spectrum we combined these data with
Multi-Element Radio Linked Interferometer Network (MERLIN) and Very
Large Array (VLA) archival data at frequencies up to 8.4GHz that have
a comparable resolution. In the inner lobes (∼2kpc), we detect the
presence of a spectral turnover that peaks at ∼225MHz and is most
likely caused by free-free absorption from the rich surrounding
medium. We confirm that these inner lobes are part of a jet-dominated
young radio source (spectral age ∼0.17Myr), which is strongly
interacting with the rich int <0.27Myr. The outer lobes (extending up
to ∼100kpc) have a spectral index of ∼0.6-0.8 from 144-4850MHz with a
remarkably uniform spatial distribution and only mild spectral
curvature. We propose that intermittent fuelling and jet flow
disruptions are powering the mechanisms that keep the spectral index
in the outer lobes from steepening and maintain the spatial uniformity
of the spectral index. Overall, it appears that 3C293 has gone through
multiple (two to three) epochs of activity. This study adds 3C293 to
the new sub-group of restarted galaxies with short interruption time
periods. This is the first time a spatially resolved study has been
performed that simultaneously studies a young source as well as the
older outer lobes at such low frequencies. This illustrates the
potential of the International LOFAR telescope to expand such studies
to a larger sample of radio galaxies.
Description:
We performed targeted observations of 3C 293 with the ILT HBA for a
total of 8h split into two 4h observing runs, on 30 July 2020 and 02
August 2020 (Project code - LC14_015).
We reprocessed archival VLA 1.36 and 4.85GHz data for the target.
1.36GHz observations were carried out with the VLA in B configuration
in November 1999 (Project code - GP022). The target was observed for
∼11h with a 25MHz bandwidth. 3C 48 and OQ 208 were the flux and
phase calibrators respectively. 4.85GHz observations of 3C 293 were
carried out on November 1986 (Project code AB412) and October 1984
(AR115) in C and D configuration respectively. 3C 286 was used as the
flux and phase calibrator for the AB412 data set. 3C 286 and OQ 208
were used as the flux and phase calibrator respectively for the AR0115
data sets.
We have reprocessed VLA 4.85GHz archival data to make a high
resolution image of the central region at 4.8GHz. 3C 293 was observed
with the VLA in December 2000 (AT0249) and August 2002 (AH0766) in A
and B configuration respectively. 3C 286 and OQ 208 were used as flux
and phase calibrators respectively for both data sets.
Objects:
-------------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------------
13 52 17.88 +31 26 46.5 3C 293 = LEDA 49258
-------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 149 7 List of fits images
fits/* . 7 Individual fits images
--------------------------------------------------------------------------------
See also:
J/MNRAS/414/1397 : Double-double radio galaxy 3C293 radio study (Joshi+, 2011)
J/A+A/564/A128 : Continuum and CO maps of 3C 293 (Labiano+, 2014)
J/A+A/658/A2 : LOFAR Long-Baseline Calibrator Survey. II. (Jackson+, 2022)
J/A+A/658/A4 : LOFAR imaging of Arp299 at 150MHz (Ramirez-Olivencia, 2022)
J/A+A/658/A5 : Hercules A LOFAR and JVLA images (Timmerman+, 2022)
J/A+A/658/A8 : Resolved jet of 3C 273 at 150 MHz (Harwood+, 2022)
J/A+A/658/A10 : 3C295 LOFAR, MERLIN and VLA images (Bonnassieux+, 2022)
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- 53 A26 "datime" Obs.date Observation date
55- 62 F8.3 MHz Freq Observed frequency
64- 67 I4 Kibyte size Size of FITS file
69-106 A38 --- FileName Name of FITS file, in subdirectory fits
108-149 A42 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Pranav Kukreti, kukreti(at)astro.rug.nl
References:
Morabito et al., Paper I 2022A&A...658A...1M 2022A&A...658A...1M
Jackson et al., Paper II 2022A&A...658A...2J 2022A&A...658A...2J, Cat. J/A+A/658/A2
Sweijen et al., Paper III 2022A&A...658A...3S 2022A&A...658A...3S
Ramirez-Olivencia et al., Paper IV 2022A&A...658A...4R 2022A&A...658A...4R, Cat, J/A+A/658/A4
Timmerman et al., Paper V 2022A&A...658A...5T 2022A&A...658A...5T, Cat, J/A+A/658/A5
Badole et al., Paper VII 2022A&A...658A...7B 2022A&A...658A...7B
Harwood et al., Paper VIII 2022A&A...658A...8H 2022A&A...658A...8H, Cat, J/A+A/658/A8
Groeneveld et al., Paper IX 2022A&A...658A...9G 2022A&A...658A...9G
Bonnassieux et al., Paper X 2022A&A...658A..10B 2022A&A...658A..10B, Cat. J/A+A/658/A10
(End) Patricia Vannier [CDS] 08-Nov-2021