J/A+A/635/A150 CasA, CygA, TauA, VirA 30MHz & 77MHz models (de Gasperin+, 2020)
Cassiopeia A, Cygnus A, Taurus A, and Virgo A at ultra-low radio frequencies.
de Gasperin F., Vink J., McKean J.P., Asgekar A., Bentum M.J., Blaauw R.,
Bonafede A., Bruggen M., Breitling F., Brouw W.N., Butcher H.R., Ciardi B.,
Cuciti V., de Vos M., Duscha S., Eisloel J., Engels D., Fallows R.A.,
Franzen T.M.O., Garrett M.A., Gunst A.W., Horandel J., Heald G.,
Koopmans L.V.E., Krankowski A., Maat P., Mann G., Mevius M., Miley G.,
Nelles A., Norden M.J., Oringa A.R., Orru E., Paas H., Pandey-Pommier M.,
Pizzo R., Reich W., Rowlinson A., Schwarz D.J., Shulevski A., Smirnov O.,
Soida M., Tagger M., Toribio M.C., van Ardenne A., van der Horst A.J.,
van Haarlem M.P., van Weeren R.J., Vocks C., Wucknitz O., Zarka P., Zucca P.
<Astron. Astrophys. 635, A150 (2020)>
=2020A&A...635A.150D 2020A&A...635A.150D (SIMBAD/NED BibCode)
ADC_Keywords: Supernovae ; Interferometry ; Models
Keywords: radio continuum: general - techniques: interferometric
Abstract:
The four persistent radio sources in the northern sky with the highest
flux density at metre wavelengths are Cassiopeia A, Cygnus A, Taurus
A, and Virgo A; collectively they are called the A-team. Their flux
densities at ultra-low frequencies (<100MHz) can reach several
thousands of janskys, and they often contaminate observations of the
low-frequency sky by interfering with image processing. Furthermore,
these sources are foreground objects for all-sky observations
hampering the study of faint signals, such as the cosmological 21cm
line from the epoch of reionisation.
We aim to produce robust models for the surface brightness emission as
a function of frequency for the A-team sources at ultra-low
frequencies. These models are needed for the calibration and imaging
of wide-area surveys of the sky with low-frequency interferometers.
This requires obtaining images at an angular resolution better than
1500 with a high dynamic range and good image fidelity.
We observed the A-team with the Low Frequency Array (LOFAR) at
frequencies between 30MHz and 77MHz using the Low Band Antenna (LBA)
system. We reduced the datasets and obtained an image for each A-team
source.
The paper presents the best models to date for the sources Cassiopeia
A, Cygnus A, Taurus A, and Virgo A between 30MHz and 77MHz. We were
able to obtain the aimed resolution and dynamic range in all cases.
Owing to its compactness and complexity, observations with the long
baselines of the International LOFAR Telescope will be required to
improve the source model for Cygnus A further.
Description:
For each of the 4 sources discussed in the paper we provide:
1. xxx-model.tgs: a series of fits files in wsclean format containing
the clean components at different frequencies (see fits header for the
frequency). The file named xxx-MFS-model.fits contains all the
components at a mean frequency.
2. xxx-sources.txt: a list of clean components in wsclean format
3. xxxLow-sources.txt: a list of clean components in wsclean format
(low resolution: 45")
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table.dat 128 12 List of files
Cas-sources.txt 201 9571 Cassiopeia A list of clean components in
wsclean format
CasA-model.tgz 512 763674 Cassiopeia A series of fits files in
wsclean format containing the clean
components at different frequencies
CasLow-sources.txt 196 1660 Cassiopeia A list of clean components in
wsclean format (low resolution: 45")
Cyg-sources.txt 199 2462 Cygnus A list of clean components in
wsclean format
CygA-model.tgz 512 450367 Cygnus A series of fits files in wsclean
format containing the clean components at
different frequencies
CygLow-sources.txt 191 335 Cygnus A list of clean components in
wsclean format (low resolution: 45")
Tau-sources.txt 200 2325 Taurus A list of clean components in
wsclean format
TauA-model.tgz 512 1014949 Taurus A series of fits files in wsclean
format containing the clean components at
different frequencies
TauLow-sources.txt 190 52 Taurus A list of clean components in
wsclean format (low resolution: 45")
Vir-sources.txt 208 9054 Virgo A list of clean components in
wsclean format
VirA-model.tgz 512 1027357 Virgo A series of fits files in
wsclean format containing the clean
components at different frequencies
VirLow-sources.txt 203 3159 Virgo A list of clean components in
wsclean format (low resolution: 45")
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- FileName Name of the file
20-128 A109 --- Title Title of the file
--------------------------------------------------------------------------------
Acknowledgements:
Francesco de Gasperin, fdg(at)hs.uni-hamburg.de
(End) Patricia Vannier [CDS] 26-Feb-2020