J/A+A/690/A163 MeerKAT Absorption Line Survey Data Release 2 (Wagenveld+ 2024)
The MeerKAT Absorption Line Survey Data Release 2.
Wideband continuum catalogues and a measurement of the cosmic radio dipole.
Wagenveld J.D., Kloeckner H.-R., Gupta N., Sekhar S., Jagannathan P.,
Deka P.P., Balashev S.A., Borgaonkar D., Chatterjee A., Combes F.,
Emig K.L., Gaunekar A.N., Hilton M., Jozsa G.I.G., Klutse D.Y., Knowles K.,
Krogager J.-K., Momjian E., Muller S., Sikhosana S.P.
<Astron. Astrophys. 690, A163 (2024)>
=2024A&A...690A.163W 2024A&A...690A.163W (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Active gal. nuclei ; Radio continuum ; Redshifts
Keywords: surveys - galaxies: statistics -
large scale structure of the Universe - radio continuum: galaxies
Abstract:
We present the second data release of the MeerKAT Absorption Line
Survey (MALS), consisting of wideband continuum catalogues of 391
pointings observed at L band. The full wideband catalogue covers
4344deg2 of sky, reaches a depth of 10µJy/beam, and contains
971980 sources. With its balance between survey depth and sky
coverage, MALS DR2 covers five orders of magnitude of flux density,
presenting a robust view of the extragalactic radio source population
down to 200µJy. Using this catalogue, we perform a measurement of
the cosmic radio dipole, an anisotropy in the number counts of radio
sources with respect to the cosmic background, analogous to the dipole
found in the cosmic microwave background (CMB). For this measurement,
we present the characterisation of completeness and noise properties
of the catalogue, and show that a declination-dependent systematic
affects the number density of faint sources. In the dipole measurement
on the MALS catalogue, we recover reasonable dipole measurements once
we model the declination systematic with a linear fit between the size
of the major axis of the restoring beam and the amount of sources of
each pointing. The final results are consistent with the CMB dipole in
terms of direction and amplitude, unlike many recent measurements of
the cosmic radio dipole made with other centimetre wavelength
catalogues, which generally show a significantly larger amplitude.
This result demonstrates the value of dipole measurements with deeper
and more sparse radio surveys, as the population of faint sources
probed may have had a significant impact on the measured dipole.
Description:
The second data release of the MeerKAT Absorption Line Survey (MALS)
consists of wideband continuum catalogues of 391 pointings observed at
L band. The full wideband catalogue covers 4344deg2 of sky and
contains 971980 sources. For each source, the observational details
and image characteristics of the pointing it is found in are given.
Source characteristics like shape and flux density are based on PyBDSF
output, with additional characteristics such as spectral index added.
An additional catalogue contains the characteristics of the individual
Gaussian components of the sources, as determined by PyBDSF.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
all.dat 1230 971980 Source catalogue
gauss.dat 437 1142084 Gaussian component catalogue
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See also:
J/A+A/673/A113 : MALS ten pointings continuum catalogue (Wagenveld+ 2023)
J/ApJS/270/33 : MeerKAT Absorption Line Survey (MALS). I. DR1 (Deka+, 2024)
Byte-by-byte Description of file: all.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Pointing Pointing where the source is found
(Pointing_id)
24- 56 A33 --- DateL Observation date(s) and time(s) of
pointing at L band (ObsdateL)
60 A1 --- Obsband [L] Observing band:
L = L band (Obs_band)
62- 73 A12 --- PBeamV Software and version of primary beam
model used for primary beam
correction (PBeamVersion)
75- 103 A29 --- Fluxcal Calibrators used for flux and
bandpass calibration (Fluxcal)
105- 153 A49 --- Fluxscale Reference flux scale used for flux
calibration (Fluxscale)
155- 162 A8 --- SPW Portion of the band used for
creating the image (SPW_id)
164- 177 F14.9 MHz RefFreq Reference frequency of the image
(Ref_freq)
179- 194 F16.13 arcsec Majaxis Major axis of restoring beam
(Majrestoringbeam)
196- 210 F15.13 arcsec Minaxis Minor axis of restoring beam
(Minrestoringbeam)
212- 228 F17.13 deg PA [] Position angle of restoring beam
(PArestoringbeam)
230- 232 F3.1 --- sigma1 [0] RMS noise measured in an annular
ring at FWHM of the primary beam
(DR1 only) (sigma_1)
234- 236 F3.1 --- sigma2 [0] RMS noise measured in an annular
ring at twice the FWHM of the
primary beam (DR1 only) (sigma_2)
238- 254 F17.13 --- sigma20 RMS noise value at a cumulative
fraction of 0.2 of the rms noise
distribution of the image
(sigma_20)
256- 274 A19 --- Name Source name following IAU convention
JHHMMSS.ss+DDMMSS.s (Source_name)
276- 296 E21.19 arcmin DistPtg Distance of source from pointing
centre (Distance_pointing)
298- 318 F21.18 arcmin SepNN Distance of source to nearest
neighbour (Distance_NN)
320 A1 --- SCode [SMC] PyBDSF source flag
(S_Code) (1)
322- 323 I2 --- NGaus [1/94] Number of Gaussian components
fit to source (N_Gaus)
325- 349 F25.17 --- MGaussMax ?=-1 Maximum separation between
Gaussian components in source
(Maxsep_Gauss)
351- 370 F20.16 arcsec MajFWHM FWHM of major axis (Maj)
372- 394 F23.19 arcsec e_MajFWHM Error on major axis (Maj_E)
396- 416 F21.17 arcsec MinFWHM FWHM of minor axis (Min)
418- 438 E21.19 arcsec e_MinFWHM Error on minor axis (Min_E)
440- 460 E21.19 deg PAMaj [0/180] Position angle of major axis
(PA)
462- 482 E21.19 deg e_PAMaj Error on position angle (PA_E)
484- 502 E19.17 arcsec DCMaj FWHM of deconvolved major axis
(DC_Maj)
504- 526 F23.19 arcsec e_DCMaj Error on deconvolved major axis
(DCMajE)
528- 549 F22.18 arcsec DCMin FWHM of deconvolved minor axis
(DC_Min)
551- 571 E21.19 arcsec e_DCMin Error on deconvolved minor axis
(DCMinE)
573- 593 E21.19 deg DCPA [0/180] Position angle of
deconvolved major axis (DC_PA)
595- 615 E21.19 deg e_DCPA Error on deconvolved position angle
(DCPAE)
617- 637 E21.19 deg RAdeg Right Ascension (J2000) (RA_mean)
639- 659 E21.19 deg e_RAdeg Error in Right Ascension (RAmeanE)
661- 682 E22.19 deg DEdeg Declination (J2000) (DEC_mean)
684- 704 E21.19 deg e_DEdeg Error in Declination (DECmeanE)
706- 726 E21.19 deg RAMdeg Right Ascension of maximum (J2000)
(RA_max)
728- 748 E21.19 deg e_RAMdeg Error on right ascension of maximum
(RAmaxE)
750- 771 E22.19 deg DEMdeg Declination of maximum (J2000)
(DEC_max)
773- 793 E21.19 deg e_DEMdeg Error on declination of maximum
(DECmaxE)
795- 815 E21.19 mJy FluxTot Total flux density of Gaussian
components (Total_flux)
817- 837 E21.19 mJy e_FluxTot Error on total flux density
(TotalfluxE)
839- 859 E21.19 mJy eFluxFit Fitting error on total flux density
(TotalfluxE_fit)
861- 881 E21.19 mJy eFluxSys Systematic error on total flux
density (TotalfluxE_sys)
883- 903 E21.19 mJy FluxTotmeas Measured total flux density
(differs from Total_flux in DR1)
(Totalfluxmeasured)
905- 925 E21.19 mJy e_FluxTotmeas Error on measured total flux density
(Totalfluxmeasured_E)
927- 950 F24.18 mJy/beam FluxP Peak flux density (Peak_flux)
952- 972 E21.19 mJy/beam e_FluxP Error on peak flux density
(PeakfluxE)
974- 995 E22.19 mJy FluxIsl Total flux of associated island of
emission (IslTotalflux)
997-1018 F22.18 mJy e_FluxIsl Error on total flux of island
(IslTotalflux_E)
1020-1042 F23.19 mJy/beam Islrms Average background RMS noise of
island (Isl_rms)
1044-1065 E22.19 mJy/beam Islmean Average background mean of island
(Isl_mean)
1067-1087 E21.19 mJy/beam ResidIslrms Average residual background RMS
noise of island (ResidIslrms)
1089-1110 E22.19 mJy/beam ResidIslmean Average residual background mean of
island (ResidIslmean)
1112-1114 F3.1 mJy/beam FluxCorr [1/1] Correction factor applied to
flux density (Flux_correction)
1116-1120 A5 --- Real [false true] False detection flag
(False: artifact, True: ok)
(Real_source)
1122-1126 A5 --- Res [false true] Resolved flag
(False: unresolved, True: resolved)
(Resolved)
1131-1153 E23.20 --- SpIndex ? Spectral index determined from MFS
image (Spectral_index)
1155-1176 F22.20 --- e_SpIndex ? Error on spectral index from MFS
image (SpectralindexE)
1178-1182 A5 --- SpIndexspw ? Spectral windows used for spectral
index measurement
(Spectralindexspwused)
1184-1206 E23.20 --- SpIndexfit ? Spectral index from spectral
window fit (Spectralindexspwfit)
1208-1230 F23.18 --- e_SpIndexfit [-999/999]? Error on spectral index
from spectral window fit
(Spectralindexspwfit_E)
-------------------------------------------------------------------------------
Note (1): S code as follows:
S = fit with a single Gaussian
M = fit with multiple Gaussians
C = one of multiple sources on the same island)
-------------------------------------------------------------------------------
Byte-by-byte Description of file: gauss.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- Source Source name following IAU convention,
MALS JHHMMSS.ss+DDMMSS.s (Source_name)
26- 32 I7 --- GID ID of Gaussian component (G_id)
34- 54 E21.19 deg RAdeg Right Ascension (J2000) (G_RA)
56- 77 E22.19 deg e_RAdeg Error in Right Ascension (GRAE)
79-100 E22.19 deg DEdeg Declination (J2000) (G_DEC)
102-123 E22.19 deg e_DEdeg Error in Declination (GDECE)
125-148 F24.18 mJy/beam Fpeak Peak flux density (GPeakflux)
150-170 E21.19 mJy/beam e_Fpeak Error on peak flux density (GPeakflux_E)
172-193 F22.18 arcsec Maj Major axis (G_Maj)
195-215 E21.19 arcsec e_Maj Error on major axis (GMajE)
217-237 E21.19 arcsec Min Minor axis (G_Min)
239-260 E22.19 arcsec e_Min Error on minor axis (GMinE)
262-282 E21.19 deg PA Position angle (G_PA)
284-304 E21.19 deg e_PA Error on position angle (GPAE)
306-326 E21.17 arcsec DCMaj Deconvolved major axis (GDCMaj)
328-348 E21.19 arcsec e_DCMaj Error on deconvolved major axis
(GDCMaj_E)
350-370 E21.18 arcsec DCMin Deconvolved minor axis (GDCMin)
372-393 E22.19 arcsec e_DCMin Error on deconvolved minor axis
(GDCMin_E)
395-415 E21.19 deg DCPA Deconvolved position angle (GDCPA)
417-437 E21.19 deg e_DCPA Error on deconvolved position angle
(GDCPA_E)
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Acknowledgements:
Jonah Wagenveld, wagenveld(at)mpifr-bonn.mpg.de
(End) J. Wagenveld [MPI for Radio Astron.], P. Vannier [CDS] 30-Aug-2024