J/MNRAS/439/1212 Deep 20GHz survey of CDFS and SDSS Stripe 82 (Franzen+, 2014)
Deep 20-GHz survey of the Chandra Deep Field-South and SDSS Stripe 82:
source catalogue and spectral properties.
Franzen T.M.O., Sadler E.M., Chhetri R., Ekers R.D., Mahony E.K.,
Murphy T., Norris R.P., Waldram E.M., Whittam I.H.
<Mon. Not. R. Astron. Soc., 439, 1212-1230 (2014)>
=2014MNRAS.439.1212F 2014MNRAS.439.1212F
ADC_Keywords: Surveys ; Radio sources
Keywords: methods: data analysis - catalogues - surveys - galaxies: active -
galaxies: evolution - radio continuum: galaxies
Abstract:
We present a source catalogue and first results from a deep, blind
radio survey carried out at 20GHz with the Australia Telescope Compact
Array, with follow-up observations at 5.5, 9 and 18GHz. The Australia
Telescope 20GHz (AT20G) deep pilot survey covers a total area of
5deg2 in the Chandra Deep Field South and in Stripe 82 of the Sloan
Digital Sky Survey. We estimate the survey to be 90% complete above
2.5mJy. Of the 85 sources detected, 55percent have steep spectra
(α1.420←0.5) and 45% have flat or inverted spectra
(α1.420≥-0.5). The steep-spectrum sources tend to have
single power-law spectra between 1.4 and 18GHz, while the spectral
indices of the flat- or inverted-spectrum sources tend to steepen with
frequency. Among the 18 inverted-spectrum (α1.420≥0.0)
sources, 10 have clearly defined peaks in their spectra with
α1.45.5>0.15 and α918←0.15. On a 3-yr time-scale,
at least 10 sources varied by more than 15percent at 20GHz, showing
that variability is still common at the low flux densities probed by
the AT20G-deep pilot survey.
Description:
The AT20G-deep pilot survey was carried out with ATCA in 2009 July,
shortly after the telescope was provided with a new wide-bandwidth
correlator, the CABB. As a result of this upgrade to the telescope,
the observing bandwidth was increased by a factor of 16, from 2x128
to 2x2048MHz, in all bands (ranging from 1.1 to 105GHz),
greatly increasing the sensitivity of continuum observations. Our
observations were made in continuum mode using two 2048-MHz CABB bands
centred at 19 and 21GHz, with each 2048-MHz band divided into 2048
1-MHz channels. All four Stokes parameters were measured.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 98 50 The 20-GHz source catalogue for the 03hr field
table3.dat 98 35 The 20-GHz source catalogue for the 21hr field
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See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VIII/90 : The FIRST Survey Catalog, Version 12Feb16 (Becker+ 2012)
J/AJ/132/2409 : Deep ATLAS radio observations of CDFS (Norris+, 2006)
Byte-by-byte Description of file: table2.dat table3.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Seq Source number (SNN)
5- 11 A7 --- --- [AT20GDP]
13- 26 A14 --- AT20GDP Source name (JHHMMS+DDMMSS)
28- 29 I2 h RAh Right ascension (J2000) (1)
31- 32 I2 min RAm Right ascension (J2000) (1)
34- 37 F4.1 s RAs Right ascension (J2000) (1)
39 A1 --- DE- Declination sign (J2000) (1)
40- 41 I2 deg DEd Declination (J2000) (1)
43- 44 I2 arcmin DEm Declination (J2000) (1)
46- 47 I2 arcsec DEs Declination (J2000) (1)
49- 54 F6.2 mJy S20 Total flux density at 20GHz (2)
56- 59 F4.2 mJy e_S20 rms uncertainty on S20 (3)
61 A1 --- l_S1.4N Limit flag on S1.4N
62- 68 F7.2 mJy S1.4N ?=- Total flux density at 1.4GHz taken from
the NVSS catalogue (Cat. VIII/65) or
estimated from the NVSS image (4)
69 A1 --- n_S1.4N [*] * indicates flux densities derived from
the NVSS image
71 A1 --- l_S1.4A Limit flag on S1.4A
72- 78 F7.2 mJy S1.4A Total flux density at 1.4GHz taken from the
ATLAS/FIRST (J/AJ/132/2409 or VIII/90)
catalogues or estimated from the ATLAS/FIRST
image in the case of the 03hr/21hr field (5)
79 A1 --- n_S1.4A [*] * indicates flux densities derived from
the ATLAS/FIRST image
81 A1 --- l_S1.4 Limit flag on S1.4
82- 88 F7.2 mJy S1.4 'best' 1.4-GHz flux density, S1.4 (6)
89 A1 --- n_S1.4 [*] * indicates flux densities derived from
NVSS or ATLAS/FIRST image
91 A1 --- l_alpha Limit flag on alpha
92- 96 F5.2 --- alpha Spectral index α1.420 between 1.4
and 20GHz obtained using S1.4 and S20
98 A1 --- Cl Spectral class: S=steep, F=flat, I=inverted
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Note (1): This is the centroid position of all components included in the
source. The peak position, interpolated between pixels, is taken to best
represent the position of a component classified as point-like; the peak
position from the Gaussing fitting is taken to best represent the position
of a component classified as extended.
Note (2): This is the total flux density of all components included in the
source. The peak flux density is taken to best represent the flux density of
a component classified as point-like; the integrated flux density from the
Gaussian fitting is taken to best represent the flux density of a component
classified as extended.
Note (3): This is the sum of the uncertainties on the flux densities of all
components included in the source. For a component classified as point-like,
the uncertainty is 5% of the peak flux density added in quadrature with the
local noise. For a component classified as extended, the uncertainty is 5% of
the integrated flux density added in quadrature with the error on the
integrated flux density reported by the Gaussian-fitting task (which accounts
for the local noise). The 5% calibration error is based on findings shown in
Murphy et al. (2010MNRAS.402.2403M 2010MNRAS.402.2403M, Cat. J/MNRAS/402/2403). To provide errors
on the 20-GHz flux density measurements in the AT20G catalogue, Murphy et al.
(2010MNRAS.402.2403M 2010MNRAS.402.2403M, Cat. J/MNRAS/402/2403) estimated the calibration error
for each observational epoch from the scatter in the visibility amplitudes of
the calibrators in each observing run. The calibration error was found to be
typically 4-5% of the total flux density.
Note (4): Flux densities were derived from the NVSS image only for sources that
did not appear in the NVSS catalogue (see Section 4 for details).
Note (5): Flux densities were derived from the ATLAS/FIRST image only for
sources that did not appear in the ATLAS/FIRST catalogue (see Section 4 for
details).
Note (6): This is the NVSS flux density if the source is present in the NVSS
catalogue, otherwise it is the ATLAS/FIRST flux density in the 03hr/21hr field.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 16-Dec-2014