J/MNRAS/435/650 325MHz GMRT survey of Herschel-ATLAS/GAMA fields (Mauch+, 2013)
A 325-MHz GMRT survey of the Herschel-ATLAS/GAMA fields.
Mauch T., Klockner H.-R., Rawlings S., Jarvis M., Hardcastle M.J.,
Obreschkow D., Saikia D.J., Thompson M.A.
<Mon. Not. R. Astron. Soc., 435, 650-662 (2013)>
=2013MNRAS.435..650M 2013MNRAS.435..650M
ADC_Keywords: Surveys ; Galaxies, radio ; Morphology
Keywords: catalogues - surveys - radio continuum: galaxies
Abstract:
We describe a 325MHz survey, undertaken with the Giant Metrewave
Radio Telescope (GMRT), which covers a large part of the three
equatorial fields at 9, 12 and 14.5h of right ascension from the
Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) in the
area also covered by the Galaxy And Mass Assembly (GAMA) survey. The
full data set, after some observed pointings were removed during the
data reduction process, comprises 212 GMRT pointings covering
∼90deg2 of sky. We have imaged and catalogued the data using a
pipeline that automates the process of flagging, calibration,
self-calibration and source detection for each of the survey
pointings. The resulting images have resolutions of between 14 and
24-arcsec and minimum rms noise (away from bright sources) of
∼1mJy/beam, and the catalogue contains 5263 sources brighter than
5σ. We investigate the spectral indices of GMRT sources which
are also detected at 1.4GHz and find them to agree broadly with
previously published results; there is no evidence for any flattening
of the radio spectral index below S1.4=10mJy. This work adds to the
large amount of available optical and infrared data in the H-ATLAS
equatorial fields and will facilitate further study of the
low-frequency radio properties of star formation and AGN activity in
galaxies out to z∼1.
Description:
The H-ATLAS/GAMA regions that have been observed by the Herschel Space
Observatory and are followed up in our GMRT survey are made up of
three separate fields on the celestial equator. The three fields are
centred at 9, 12 and 14.5h of right ascension (RA), and each spans
approximately 12° in RA and 3° in declination to cover a total
of 108deg2 (36deg2 per field). The full width at half-maximum
(FWHM) of the primary beam of the GMRT at 325MHz is 84-arcmin. In
order to cover each H-ATLAS/GAMA field as uniformly and efficiently as
possible, we spaced the pointings in a hexagonal grid separated by
42-arcmin.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
9hcat.dat 133 2628 9h field catalog
12hcat.dat 133 1620 12h field catalog
14_5hcat.dat 133 1015 14.5h field catalog
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See also:
J/MNRAS/415/2336 : Herschel-ATLAS Science Demonstration Catalog (Rigby+, 2011)
J/MNRAS/413/971 : Galaxy And Mass Assembly (GAMA) DR1 (Driver+, 2011)
Byte-by-byte Description of file: 9hcat.dat 12hcat.dat 14_5hcat.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right ascension (J2000)
11- 19 F9.5 deg DEdeg Declination (J2000)
22- 23 I2 h RAh Right ascension (J2000)
25- 26 I2 min RAm Right ascension (J2000)
28- 32 F5.2 s RAs Right ascension (J2000)
34 A1 --- DE- Declination sign (J2000)
35- 36 I2 deg DEd Declination (J2000)
38- 39 I2 arcmin DEm Declination (J2000)
41- 44 F4.1 arcsec DEs [0/60] Declination (J2000)
48- 50 F3.1 arcsec e_RAs rms uncertainty on RA (1)
53- 55 F3.1 arcsec e_DEs rms uncertainty on DE (1)
58- 63 F6.1 mJy A 325MHz fitted peak brightness (mJy/beam) (2)
65- 69 F5.1 mJy e_A rms uncertainty on A (mJy/beam) (2)
71- 76 F6.1 mJy S 325MHz total flux density (3)
78- 82 F5.1 mJy e_S rms uncertainty on S (3)
85- 88 F4.1 arcsec Maj ?=- Major axis FWHM of the fitted
elliptical Gaussian
90- 93 F4.1 arcsec Min ?=- Minor axis FWHM of the fitted
elliptical Gaussian
95- 99 F5.1 deg PA [0/180]?=- Position angle (east of north)
of the fitted elliptical Gaussian (4)
101-104 F4.1 arcsec e_Maj ?=- rms uncertainty on Maj (5)
106-109 F4.1 arcsec e_Min ?=- rms uncertainty on Min (5)
111-112 I2 deg e_PA ?=- rms uncertainty on PA (5)
115-118 F4.1 mJy rms Local rms noise (mJy/beam) (6)
120-133 A14 --- Pointing Name of the GMRT mosaicked image
containing the source (7)
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Note (1): This is calculated from the quadratic sum of the calibration
uncertainty, described in Section 5.3, and the fitting uncertainty, calculated
using the equations given by Condon (1997PASP..109..166C 1997PASP..109..166C).
Note (2): The fitted peak brightness and its associated uncertainty, calculated
from the quadratic sum of the fitting uncertainty from the equations given by
Condon (1997PASP..109..166C 1997PASP..109..166C) and the estimated 5% flux calibration
uncertainty of the GMRT. The raw brightness measured from the image has
been increased by 0.9mJy/beam to account for the effects of clean bias
(see Section 5.2).
Note (3): The total flux density of the source and its uncertainty calculated
from equations given by Condon (1997PASP..109..166C 1997PASP..109..166C). This equals the fitted
peak brightness if the source is unresolved.
Note (4): The PA is only meaningful for sources that are resolved (i.e. when
the fitted Gaussian is larger than the restoring beam for the relevant field).
As discussed in Section 5.4, fitted sizes are only quoted for sources that are
moderately resolved in their minor axis.
Note (5): The fitting uncertainties in the size parameters of the fitted
elliptical Gaussian calculated using equations from Condon
(1997PASP..109..166C 1997PASP..109..166C).
Note (6): Local rms noise σ(local) at the source position calculated as
described in Section 3.3. The local rms is used to determine the source
signal-to-noise ratio, which is used to determine fitting uncertainties.
Note (7): These names consist of the letters PN, a letter A, B or C indicating
the 9-, 12- or 14.5-h fields, respectively, and a number between 01 and 96
which gives the pointing number within that field (see Fig. 1).
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 19-Sep-2014