VIII/97 74MHz VLA Low-frequency Sky Survey Redux (VLSSr) (Lane+, 2014)
The Very Large Array Low-frequency Sky Survey Redux (VLSSr).
Lane W.M., Cotton W.D., van Velzen S., Clarke T.E., Kassim N.E.,
Helmboldt J.F., Lazio T.J.W., Cohen A.S.
<Mon. Not. R. Astron. Soc., 440, 327-338 (2014)>
=2014MNRAS.440..327L 2014MNRAS.440..327L
ADC_Keywords: Radio continuum ; Radio sources ; Surveys
Keywords: techniques: image processing; catalogues; surveys;
radio continuum: general
Abstract:
We present the results of a recent re-reduction of the data from the
Very Large Array (VLA) Low-frequency Sky Survey (VLSS). We used the
VLSS catalogue as a sky model to correct the ionospheric distortions
in the data and create a new set of sky maps and corresponding
catalogue at 73.8MHz. The VLSS Redux (VLSSr) has a resolution of 75",
and an average map rms noise level of σ∼0.1Jy/beam. The clean
bias is 0.66xσ and the theoretical largest angular size is 36'.
Six previously unimaged fields are included in the VLSSr, which has an
unbroken sky coverage over 9.3sr above an irregular southern boundary.
The final catalogue includes 92964 sources. The VLSSr improves upon
the original VLSS in a number of areas including imaging of large
sources, image sensitivity, and clean bias; however the most critical
improvement is the replacement of an inaccurate primary beam
correction which caused source flux errors which vary as a function of
radius to nearest pointing centre in the VLSS.
Description:
The VLSSr reprocessed all of the data from the original VLSS project.
The observations were made between 2001 and 2007, under VLA observing
programs AP397, AP441, AP452, and AP509. The sky was divided into a
roughly hexagonal grid of 523 pointing centres, at a spacing of
8.6°. The bandwidth used was 1.56MHz centred at 73.8MHz. Fields in
the range -10<DEC<80° were observed in the VLA B configuration,
while those at DEC←10° and DEC>80° were observed in the BnA
configuration to compensate for beam elongation at low elevations.
Further details of the observational setup are given in Cohen et al.
(VLSS; 2007, Cat. VIII/79).
The final catalogue contains 92964 entries. Of these, roughly 3 per
cent have no match in the NVSS within 60 arcsec of the fitted
position. However many unmatched sources are actually components of
larger sources which may be fit differently in the two catalogues.
The global rms position error is 3.3 arcsec in RA and 3.5 arcsec in
declination.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 81 523 List of each pointing
catalog.dat 105 92965 VLSSr catalog
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See also:
VIII/81 : Sydney University Molonglo Sky Survey (SUMSS V2.1) (Mauch+ 2008)
VIII/79 : The VLA Low-frequency Sky Survey at 74MHz (VLSS) (Cohen+ 2007)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VIII/62 : The Westerbork Northern Sky Survey (Leiden, 1998)
VIII/31 : Revised source list for the Rees 38-MHz survey (Hales+ 1995)
VIII/23 : 6C Survey of radio sources - IV. (Hales+ 1991)
VIII/5 : Bright Extragalactic Radio Sources (1Jy) (Kuehr+, 1981)
J/ApJS/200/8 : AGES: the AGN and Galaxy Evolution Survey (Kochanek+, 2012)
J/MNRAS/402/2403 : Australia Telescope 20GHz Survey Catalog (Murphy+, 2010)
J/A+A/456/791 : XMM-LSS field at 74 and 325MHz (Tasse+, 2006)
J/MNRAS/352/131 : 13+38 XMM-Newton/ROSAT 1.4GHz radio catalog (Seymour+, 2004)
http://www.cv.nrao.edu/vlss/VLSSpostage.shtml : VLSSr Postage Stamp server
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Field Field designation (HHMM+DDd; J2000)
10- 15 F6.4 Jy rms [0.04/1.5] rms noise over the inner half of
the image; in Jy/beam
17- 21 I5 --- Range [8/16679] Final dynamic range (peak to rms)
23- 32 A10 --- Meth Reduction method used on the final map (1)
34- 81 A48 --- Note Notes
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Note (1): Method as follows:
2 = second order Zernike fits
3 = third order Zernike fits
nvss = NVSS was used as a calibrator catalogue
brt = bright source subtracted, with the source indicated in the notes column
peel = sources with peaks greater than 10Jy/beam were peeled
RFI = more stringent RFI (Obit tasks: RFIFilt, AutoFlag;
Lane et al. 2012RaSc...47.0K04L; Cotton W.D. 2009, Obit Development
Memo Series. Vol. 16.) removal criteria were used.
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Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right ascension (J2000) (RA2000)
12- 21 F10.6 deg DEdeg Declination (J2000) (DEC2000)
23- 29 F7.2 Jy Sp [0.2/8498] Peak intensity at 74MHz;
in Jy/beam (PEAK_INT)
31- 34 F4.2 deg MajAx [0.02/0.03] Major axis of deconvolved
component size (MAJOR_AX)
36- 39 F4.2 deg MinAx [0.02/0.03] Minor axis of deconvolved
component size (MINOR_AX)
41- 46 F6.2 deg PA [-90/90] Position angle of Major Ax (POSANGLE)
48- 51 F4.2 Jy e_Sp [0.05/7.1] Intensity RMS in Jy/beam (I_RMS)
53- 58 F6.2 Jy Rrms [0.02/353] Residual RMS, in Jy/beam (RES_RMS)
60- 66 F7.2 Jy Rpk [0.05/3824] Residual peak intensity, in Jy/beam
(RES_PEAK)
68- 74 F7.2 Jy RFlx [-102/105] Residual integrated flux (RES_FLUX)
76- 81 F6.1 pix Xpos [332/3745] X position of source on map (CENTER_X)
83- 88 F6.1 pix Ypos [332/3745] Y position of source on map (CENTER_Y)
90- 97 A8 --- Field Field designation (HHMM+DDd; J2000) (FIELD)
99-105 I7 d JD [2456435] Julian Date field processed (2456435)
(JD_PROCESSED)
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History:
* 29-Oct-2014: from electronic version of the journal for table 1.
Copied at http://www.cv.nrao.edu/vlss/CATALOG/ for VLSSR.CATALOG.FIT
(26-Aug-2013 version)
(End) Emmanuelle Perret [CDS] 29-Oct-2014