J/A+A/658/A10 3C295 LOFAR, MERLIN and VLA images (Bonnassieux+, 2022)
Spectral analysis of spatially-resolved 3C295 (sub-arc second resolution) with
the International LOFAR Telescope.
Bonnassieux E.H.J., Sweijen F., Brienza M., Rajpurohit K., Riseley C.J.,
Bonafede A., Jackson N., Morabito L.K., Brunetti G., Harwood J., Kappes A.,
Rottgering H.J., Tasse C., van Weeren R.
<Astron. Astrophys. 658, A10 (2022)>
=2022A&A...658A..10B 2022A&A...658A..10B (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Radio sources
Keywords: instrumentation: high angular resolution - methods: observational -
instrumentation: interferometers - radio continuum: galaxies -
galaxies: individual: 3C295
Abstract:
3C295 is a bright, compact steep spectrum source with a well-studied
integrated radio spectral energy distribution (SED) from 132MHz to
15GHz. However, spatially resolved spectral studies have been limited
due to a lack of high resolution images at low radio frequencies. These
frequencies are crucial for measuring absorption processes,
and anchoring the overall spectral modelling of the radio SED. In this
paper, we use International LOw-Frequency ARray (LOFAR) Telescope
(ILT) observations of 3C295 to study its spatially resolved spectral
properties with sub-arcsecond resolution at 132MHz. Combining our new
132MHz observation with archival data at 1.6GHz, 4.8GHz, and 15GHz, we
are able to carryout a resolved radio spectral analysis. The spectral
properties of the hotspots provides evidence for low
frequency flattening. In contrast, the spectral shape across the lobes
is consistent with a Jaffe-Perola spectral ageing model. Usingthe
integrated spectral information for each component, we then fitted
low-frequency absorption models to the hotspots,finding that both
free-free absorption and synchrotron self-absorption models provide a
better fit to the data than a standard power law. Although we can say
there is low-frequency absorption present in the hot spots of 3C295,
future observations with the Low Band Antenna of the ILT at 55MHz may
allow us to distinguish the type of absorption.
Description:
Reduced data cubes containing the flux density maps for this paper.
The LOFAR HBA data were taken during a targeted observation of 3C 295
(PI: Sweijen; project code COM_010, L693723) on January 25, 2019. It
was observed from 01:41:00 to 09:40:59 UT, for a total of 8h on
source and was book-ended by two 15 min calibrator observations.
The archival MERLIN observation was taken on 26 May 1998, with a
central observing frequency of 1.658 GHz and a total bandwidth of
26MHz. The observation included 6 antennas. The data were extracted
from the MERLIN archive, and flux-calibrated with 3C286.
Our VLA data were acquired from the NRAO Science Data Archive. We
restricted our search to observations from A-configuration and longer
than two hours in duration to maximise our uv-coverage. We used two
observations from the NRAO Science Data Archive, each in
A-configuration and longer than two hours in duration to maximise our
uv-coverage and each comprising two frequency bands, taken as part of
project AP135 (PI: R. Perley) on 12 September 1987. The central
frequencies of each observation were 4.76 and 14.975GHz, with
bandwidths of 50MHz.
Objects:
-------------------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------------------
14 11 20.47 +52 12 09.5 3C 295 = QSO J1411+522
-------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 126 4 List of fits files
fits/* . 4 Individual fits files
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See also:
J/A+A/285/785 : 3C 295 BRri photometry (Thimm+, 1994)
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/A6 : 3C293 high and low resolution maps (Kukreti+, 2022)
J/A+A/658/A8 : Resolved jet of 3C 273 at 150 MHz (Harwood+, 2022)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 50 A21 "datime" Obs.date Observation date
52- 56 I5 Kibyte size Size of FITS file
58- 70 A13 --- FileName Name of FITS file, in subdirectory fits
72-126 A55 --- Title Title of the FITS file
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Acknowledgements:
Etienne Bonnassieux, etienne.bonnassieux(at)unibo.it
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
Kukreti et al., Paper VI 2022A&A...658A...6K 2022A&A...658A...6K, Cat, J/A+A/658/A6
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
(End) Patricia Vannier [CDS] 14-Sep-2021