J/MNRAS/509/2150 MIGHTEE catalogues of COSMOS/XMM-LSS fields (Heywood+, 2022)
MIGHTEE: total intensity radio continuum imaging and the COSMOS/XMM-LSS
Early Science fields.
Heywood I., Jarvis M.J., Hale C.L., Whittam I.H., Bester H.L., Hugo B.,
Kenyon J.S., Prescott M., Smirnov O.M., Tasse C., Afonso J.M., Best P.N.,
Collier J.D., Deane R.P., Frank B.S., Hardcastle M.J., Knowles K.,
Maddox N., Murphy E.J., Prandoni I., Randriamampandry S.M., Santos M.G.,
Sekhar S., Tabatabaei F., Taylor A.R., Thorat K.
<Mon. Not. R. Astron. Soc. 509, 2150-2168>
=2022MNRAS.509.2150H 2022MNRAS.509.2150H (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galaxies ; Radio continuum ; Radio sources ;
Positional data ; Photometry ; Spectroscopy
Keywords: techniques: interferometric - surveys - radio continuum: galaxies
Abstract:
MIGHTEE is a galaxy evolution survey using simultaneous radio
continuum, spectropolarimetry, and spectral line observations from the
South African MeerKAT telescope. When complete, the survey will image
∼20 deg2 over the COSMOS, E-CDFS, ELAIS-S1, and XMM-Newton Large Scale
Structure field (XMM-LSS) extragalactic deep fields with a central
frequency of 1284 MHz. These were selected based on the extensive
multiwavelength data sets from numerous existing and forthcoming
observational campaigns. Here, we describe and validate the data
processing strategy for the total intensity continuum aspect of
MIGHTEE, using a single deep pointing in COSMOS (1.6 deg2) and a
three-pointing mosaic in XMM-LSS (3.5 deg2). The processing includes
the correction of direction-dependent effects, and results in thermal
noise levels below 2 µJy.beam-1 in both fields, limited in the
central regions by classical confusion at ∼8 arcsec angular
resolution, and meeting the survey specifications. We also produce
images at ∼5 arcsec resolution that are ∼3 times shallower. The
resulting image products form the basis of the Early Science continuum
data release for MIGHTEE. From these images we extract catalogues
containing 9896 and 20274 radio components in COSMOS and XMM-LSS,
respectively. We also process a close-packed mosaic of 14 additional
pointings in COSMOS and use these in conjunction with the Early
Science pointing to investigate methods for primary beam correction of
broad-band radio images, an analysis that is of relevance to all
full-band MeerKAT continuum observations, and wide-field
interferometric imaging in general. A public release of the MIGHTEE
Early Science continuum data products accompanies this article.
Description:
Radio continuum observations are a uniquely powerful tool in the
pursuit of understanding how galaxies form and evolve over cosmic
time, one of the key goals of modern astrophysics. Concernong our
study, MeerKAT consists of 64 * 13.5 m dishes with offset Gregorian
optics, providing an unblocked aperture. It is equipped with three
receiver bands: UHF (544-1088 MHz), L band (856-1712 MHz), and S
band (1750-3500 MHz). Three-quarters of the collecting area is
within a dense, 1 km diameter core region, and the remaining dishes
are situated around the core, providing a maximum baseline of 8 km.
The large number of baselines, wide field of view (1 deg at L band),
and low (∼20 K) system temperature all conspire to make MeerKAT an
exceptionally fast and capable synthesis imaging telescope.
Also coming in at the deep end is MIGHTEE (MeerKAT International
Gigahertz Tiered Extragalactic Explorations).
MIGHTEE is one of MeerKAT's flagship Large Survey Projects, a galaxy
evolution survey that is using simultaneous continuum, polarimetry
and spectral line (Maddox et al. 2021A&A...646A..35M 2021A&A...646A..35M)
measurements to investigate the formation and evolution of galaxies
over cosmic time. It will use ∼1000 h of observations with
MeerKAT's L-band receivers, with the goal of imaging 20 deg2 over
four extragalactic deep fields, namely COSMOS, the Extended Chandra
Deep Field South (E-CDFS), the southermost field of the European Large
Area ISO Survey (ELAIS-S1), and the XMM-Newton Large Scale Structure
field (XMM-LSS).
After data processing and data productions (partly made with the PYBDSF
algorithm, see respectively section 2 Observations and data processing
and 3 Early science continuum data products) we product two level-1
catalogue cosmosl1.dat and xmmlssl1.dat which synthetized and compiled
all the radio components retreived from these two interesting fields.
Further, (i.e see the section 4 Discussion) we discuss succesively on
Astrometry verification (section 4.1), Photometry verification
(section 4.2) and Reliability of resolved sources (section 4.3) in
order to check data quality of our samples.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cosmosl1.dat 251 9896 *COSMOS Level-1 Early Science radio component
catalogue
xmmlssl1.dat 250 20274 *XMM-LSS Level-1 Early Science radio component
catalogue
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Note on cosmosl1.dat and xmmlssl1.dat: The image and catalogue products
presented in this article can be freely accessed from
https://doi.org/10.48479/emmd-kf31 . The data processing scripts used can be
downloaded from https://github.com/IanHeywood/oxkat (v0.1), and the underlying
software packages from the links therein.
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See also:
J/A+A/602/A1 : VLA-COSMOS 3 GHz Large Project (Smolcic+, 2017)
J/MNRAS/429/1652 : XMM-LSS catalogue. Version II. (Chiappetti+, 2013)
J/ApJ/910/105 : VLA Frontier Fields survey for 3 MACS clusters
(Heywood+, 2021)
J/MNRAS/481/4548 : New constraints on the 1.4GHz source counts (Prandoni+,2018)
VIII/100 : GaLactic and Extragalactic All-sky MWA survey
(Hurley-Walker+, 2016)
J/A+A/598/A104 : LOFAR Two-metre Sky Survey (Shimwell+, 2017)
https://doi.org/10.48479/emmd-kf31 : The image and catalogue products
https://github.com/IanHeywood/oxkat : The data processing scripts
Byte-by-byte Description of file: cosmosl1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- ID Radio component identifier name in form
JHHMMSS.SS±DDMMSS.S (NAME)
21- 29 F9.5 deg RAdeg Right Ascension (RA) (J2000) (G1)
31- 37 F7.5 deg e_RAdeg Mean 1σ positional uncertainty of
right ascension (E_RA) (G1)
39- 45 F7.5 deg DEdeg Declination (DEC) (J2000) (G1)
47- 53 F7.5 deg e_DEdeg Mean 1σ positional uncertainty of
declination (E_DEC) (G1)
55- 63 F9.7 Jy Snu Integrated flux density at an given
effective frequency νeff (S_INT) (G2)
65- 73 F9.7 Jy e_Snu Mean 1σ uncertainty of Sν
(ESINT)
75- 83 F9.7 Jy/beam Speak The peak brightness at νeff (S_PEAK)
85- 93 F9.7 Jy/beam e_Speak Mean 1σ uncertainty of Speak
(ESPEAK)
95-104 I10 Hz nueff Observational effective frequency
(NU_EFF) (G3)
106-114 F9.7 Jy S1.4 Integrated flux density corrected
to 1.4 GHz assuming νeff values
(S_INT14) (G4)
116-124 F9.7 Jy e_S1.4 Mean 1σ uncertainty of S1.4
(ESINT14)
126-134 F9.7 Jy/beam Speak1.4 The peak brightness corrected to 1.4 GHz
assuming νeff values (S_PEAK14) (G4)
136-144 F9.7 Jy/beam e_Speak1.4 Mean 1σ uncertainty of Speak1.4
(ESPEAK14)
146-152 F7.5 deg MajAxis The major axis of the 2D Gaussian fitted
to the source by PYBDSF (IM_MAJ) (G5)
154-160 F7.5 deg e_MajAxis Mean 1σ uncertainty of MajAxis
(EIMMAJ)
162-168 F7.5 deg MinAxis The minor axis of the 2D Gaussian fitted
to the source by PYBDSF (IM_MIN) (G5)
170-176 F7.5 deg e_MinAxis Mean 1σ uncertainty of MinAxis
(EIMMIN)
178-182 F5.1 deg PA The position angle measured east of north
(IM_PA)
184-188 F5.1 deg e_PA Mean 1σ uncertainty of PA (EIMPA)
190-196 F7.5 deg ThetaM The major axis of the deconvolved source
size (THETA_MAJ) (G6)
198-206 F9.5 deg e_ThetaM Mean 1σ uncertainty of ΘM
(ETHETAMAJ)
208-214 F7.5 deg Thetam The minor axis of the deconvolved source
size (THETA_MIN) (G6)
216-224 F9.5 deg e_Thetam Mean 1σ uncertainty of Θm
(ETHETAMIN)
226 I1 --- Res Resolved flag (equal to 1) if it satisfies
our criterion (RESOLVED) (G7)
228-236 F9.7 Jy/beam RMSnoise Average background rms noise around the
component estimated by PYBDSF (ISL_RMS)
238-241 I4 --- IDgauss A unique identifier for the Gaussian
component from the raw PYBDSF output
(GAUS_ID)
243-246 I4 --- IDsrc A unique identifier for the source from
the raw PYBDSF output (SRC_ID)
248-251 I4 --- IDisl A unique identifier for the island from
the raw PYBDSF output (ISL_ID)
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Byte-by-byte Description of file: xmmlssl1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- ID Radio component identifier name in form
JHHMMSS.SS±DDMMSS.S (NAME)
21- 28 F8.5 deg RAdeg Right Ascension (RA) (J2000) (G1)
30- 36 F7.5 deg e_RAdeg Mean 1σ positional uncertainty of
right ascension (E_RA) (G1)
38- 45 F8.5 deg DEdeg Declination (DEC) (J2000) (G1)
47- 53 F7.5 deg e_DEdeg Mean 1σ positional uncertainty of
declination (E_DEC) (G1)
55- 63 F9.7 Jy Snu Integrated flux density at an given
effective frequency νeff (S_INT) (G2)
65- 73 F9.7 Jy e_Snu Mean 1σ uncertainty of Sν
(ESINT)
75- 83 F9.7 Jy/beam Speak The peak brightness at νeff (S_PEAK)
85- 93 F9.7 Jy/beam e_Speak Mean 1σ uncertainty of Speak
(ESPEAK)
95-104 I10 Hz nueff Observational effective frequency
(NU_EFF) (G3)
106-114 F9.7 Jy S1.4 Integrated flux density corrected
to 1.4 GHz assuming νeff values
(S_INT14) (G4)
116-124 F9.7 Jy e_S1.4 Mean 1σ uncertainty of S1.4
(ESINT14)
126-134 F9.7 Jy/beam Speak1.4 The peak brightness corrected to 1.4 GHz
assuming νeff values (S_PEAK14) (G4)
136-144 F9.7 Jy/beam e_Speak1.4 Mean 1σ uncertainty of Speak1.4
(ESPEAK14)
146-152 F7.5 deg MajAxis The major axis of the 2D Gaussian fitted
to the source by PYBDSF (IM_MAJ) (G5)
154-160 F7.5 deg e_MajAxis Mean 1σ uncertainty of MajAxis
(EIMMAJ)
162-168 F7.5 deg MinAxis The minor axis of the 2D Gaussian fitted
to the source by PYBDSF (IM_MIN) (G5)
170-176 F7.5 deg e_MinAxis Mean 1σ uncertainty of MinAxis
(EIMMIN)
178-182 F5.1 deg PA The position angle measured east of north
(IM_PA)
184-188 F5.1 deg e_PA Mean 1σ uncertainty of PA (EIMPA)
190-196 F7.5 deg ThetaM The major axis of the deconvolved source
size (THETA_MAJ) (G6)
198-204 F7.5 deg e_ThetaM Mean 1σ uncertainty of ΘM
(ETHETAMAJ)
206-212 F7.5 deg Thetam The minor axis of the deconvolved source
size (THETA_MIN) (G6)
214-220 F7.5 deg e_Thetam Mean 1σ uncertainty of Θm
(ETHETAMIN)
222 I1 --- Res Resolved flag (equal to 1) if it satisfies
our criterion (RESOLVED) (G7)
224-232 F9.7 Jy/beam RMSnoise Average background rms noise around the
component estimated by PYBDSF (ISL_RMS)
234-238 I5 --- IDgauss A unique identifier for the Gaussian
component from the raw PYBDSF output
(GAUS_ID)
240-244 I5 --- IDsrc A unique identifier for the source from
the raw PYBDSF output (SRC_ID)
246-250 I5 --- IDisl A unique identifier for the island from
the raw PYBDSF output (ISL_ID)
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Global notes:
Note (G1): These uncertainties are the statistical uncertainties derived from
the component fitting by pybdsf and thus do not include astrometric
errors. RAdeg and DEdeg have not been corrected for any systematic
offsets, (i.e please refer to section 4.1 Astrometry verification).
Note (G2): The integrated flux density Sν is acquired in the spectral Lband
(856-1712 MHz) around 1300 MHz, (i.e refer to sections 3.3 Radio
component catalogues and 4.2 Photometry verification).
Note (G3): As explained in the section 3.2 Effective frequency images, we define
νeff for each individual pointing at each pixel (x,y) positions
in the full-band image using the weighted mean νeff(x,y), (i.e
the equation 3 of this section). More, for the COSMOS field, we
denote a frequency range [1.304-1.375] GHz with 1.348 GHz mean value,
while for the XMMLSS field, we denote a frequency range [1.248-1.348]
GHz with 1.318 GHz mean value.
Note (G4): For each component in the catalogue, we extracted the effective
frequency νeff at its position from the maps described in
Section 3.2, assuming a spectral index of -0.7, in order to correct
the flux density and peak brightness measurements to a common
frequency of 1.4 GHz. This frequency is selected as it is the
commonly used reference frequency for previous L-band continuum
studies, (i.e refer to section 3.3.4 Effective frequencies).
Note (G5): As explicited in the section 3.3.3 Resolved sources, major and minor
axis (φM * φm) define fitted image component correspond
to the source area determined with PYBDSF source finder
(Mohan & Rafferty 2015ascl.soft02007M, i.e refer to the section
3.3.1 Source finding).
Note (G6): As explained in the section 3.3.3 Resolved sources, following
Murphy et al. (2017ApJ...839...35M 2017ApJ...839...35M), the deconvolved size
(ΘM * Θm) of a Gaussian component is given by the
equation 4 of this section. The uncertainty in the deconvolved source
size is calculated according to the equation 5 of this section.
Similarly, we compute Θm based on equation 4 and 5, see also
Wild (1970AuJPh..23..113W 1970AuJPh..23..113W) for the equations of the generalized case
involving an elliptical restoring beam. More, a zero in these columns
means that the source was fitted with an unphysical size by PYBDSF
and is assumed to be unresolved along the major and minor axis.
Note (G7): Evaluate the relationship given in equation 6 of the section 3.3.3
Resolved sources, to flag sources that are deemed to be reliably
resolved. Thus, the number of components that are flagged as resolved
are 898 (10 per cent) and 1376 (7 per cent) in COSMOS and XMM-LSS,
respectively.
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 18-Sep-2024