J/AJ/131/1872 Fourth VLBA calibrator survey: VCS4 (Petrov+, 2006)
The fourth VLBA calibrator survey: VCS4.
Petrov L., Kovalev Y.Y., Fomalont E.B., Gordon D.
<Astron. J., 131, 1872-1879 (2006)>
=2006AJ....131.1872P 2006AJ....131.1872P
ADC_Keywords: Surveys ; Radio sources ; Positional data
Keywords: astrometry - catalogs - surveys
Abstract:
This paper presents the fourth extension to the VLBA Calibrator
Survey, containing 258 new sources not previously observed with very
long baseline interferometry (VLBI). This survey, based on three 24hr
Very Long Baseline Array observing sessions, fills remaining areas on
the sky above declination -40° where the calibrator density is
less than one source within a 4° radius disk in any given
direction. The share of these areas was reduced from 4.6% to 1.9%.
Source positions were derived from astrometric analysis of group
delays determined at 2.3 and 8.6GHz frequency bands using the
Calc/Solve software package. The VCS4 catalog of source positions,
plots of correlated flux density versus projected baseline length,
contour plots, and fits files of naturally weighted CLEAN images, as
well as calibrated visibility function files, are available online at
http://vlbi.gsfc.nasa.gov/vcs4 .
Description:
The VCS4 observations were carried out in three 24hr observing
sessions with the VLBA on 2005 May 12, June 12, and June 30. Each
target source was observed in two scans. The scan duration was 120s
for sources from the list of 107 bright objects and 235s for other
target sources. The target sources were observed in a sequence
designed to minimize loss of time from antenna slewing. In addition to
these objects, 93 strong sources were taken from the Goddard Space
Flight Center astrometric and geodetic catalog 2004f_astro (See
http://vlbi.gsfc.nasa.gov/solutions/astro). Observations of three to
four strong sources from this list were made every 11.5hr during
observing sessions.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 111 292 The VCS4 catalog
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See also:
J/ApJS/141/13 : VLBA calibrator Survey - VCS1 catalog (Beasley+, 2002)
J/AJ/126/2562 : Second VLBA calibrator survey: VCS2 (Fomalont+, 2003)
J/AJ/129/1163 : Third VLBA calibrator survey: VCS3 (Petrov+, 2005)
http://vlbi.gsfc.nasa.gov/vcs4 : VCS4 Home Page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 A1 --- Cat [-C] Category (where C = calibrator)
3- 10 A8 --- IVS The IVS name (B1950), BHHMM-DDd
12- 21 A10 --- VCS4 The IAU name (J2000), JHHMM-DDMM
23- 24 I2 h RAh Hour of Right ascension (J2000)
26- 27 I2 min RAm Minute of Right ascension (J2000)
29- 37 F9.6 s RAs Second of Right ascension (J2000)
39 A1 --- DE- Sign of the Declination (J2000)
40- 41 I2 deg DEd Degree of Declination (J2000)
43- 44 I2 arcmin DEm Arcminute of Declination (J2000)
46- 53 F8.5 arcsec DEs Arcsecond of Declination (J2000)
55- 60 F6.2 mas e_RAs Inflated error in Right Ascension
62- 67 F6.2 mas e_DEs Inflated error in Declination
69- 74 F6.3 --- Corr Correlation between Right Ascension
and Declination errors
76- 78 I3 --- Nobs Number of group delays used for
position determination
80 A1 --- l_T8.6GHz Upper limit flag on T8.6GHz
81- 84 F4.2 Jy T8.6GHz ? X-band (8.6GHz) total flux density
integrated over entire map (1)
86 A1 --- l_U8.6GHz Upper limit flag on U8.6GHz
87- 90 F4.2 Jy U8.6GHz ? X-band (8.6GHz) unresolved flux density at
longest VLBA baselines (1)
92 A1 --- l_T2.3GHz Upper limit flag on T2.3GHz
93- 96 F4.2 Jy T2.3GHz ? S-band (2.3GHz) total flux density
integrated over entire map (1)
98 A1 --- l_U2.3GHz Upper limit flag on U2.3GHz
99-102 F4.2 Jy U2.3GHz ? S-band (2.3GHz) unresolved flux density at
longest VLBA baselines (1)
104-106 A3 --- Band Used band for position estimation (2)
108-111 A4 --- --- [VCS4] Catalog name
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Note (1): NULL = no data are available. All bytes of the columns are blank.
Note (2): Band as follows:
X = central frequency 8.6GHz
S = central frequency 2.3GHz
X/S = Both bands with central frequency 8.6 and 2.3GHz
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 21-Sep-2007