J/AJ/126/2562 Second VLBA calibrator survey: VCS2 (Fomalont+, 2003)
The second VLBA calibrator survey: VCS2.
Fomalont E.B., Petrov L., Macmillan D.S., Gordon D., Ma C.
<Astron. J., 126, 2562-2566 (2003)>
=2003AJ....126.2562F 2003AJ....126.2562F
ADC_Keywords: Radio sources ; Surveys ; Positional data
Keywords: astrometry - catalogs - quasars: general - radio continuum -
reference systems - techniques: interferometric
Abstract:
This paper presents an extension of the Very Long Baseline Array
Calibrator Survey, called VCS2, containing 276 sources. This survey
fills in regions of the sky that were not completely covered by the
previous VCS1 calibrator survey. The VCS2 survey includes calibrator
sources near the Galactic plane, -30°<DE←45°, and VLA
calibrators. The positions have been derived from astrometric analysis
of the group delays measured at 2.3 and 8.4 GHz using the Goddard
Space Flight Center CALC/SOLVE package. From the VLBA snapshot
observations, images of the calibrators are available, and each source
is given a quality code for anticipated use. The VCS2 catalog is
available from the NRAO Web site.
Description:
The VCS2 observations were carried out in two 24hr sessions:
2002 January 31 and 2002 May 14. The observations used the VLBA
dual-frequency geodetic mode, observing simultaneously at 2.3GHz
(S band) and 8.4GHz (X band). The data for each of these two
frequencies were separated into four 8MHz channels, which spanned
140MHz at 2.3GHz and 490MHz at 8.4GHz, in order to provide precise
measurements of the group delays for astrometric processing.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 100 276 The VCS2 Source List
--------------------------------------------------------------------------------
See also:
VIII/60 : Interferometer phase calibration sources (Patnaik+ 1998)
J/ApJS/141/13 : VLBA calibrator Survey - VCS1 catalog (Beasley+, 2002)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- VCS2 Second VLBA Calibrator Survey J2000 source name
12- 19 A8 --- IVS The B1950 source name (1)
21- 22 I2 h RAh Hour of right ascension (J2000)
24- 25 I2 min RAm Minute of right ascension (J2000)
27- 34 F8.5 s RAs Second of right ascension (J2000)
36- 42 F7.5 s e_RAs The 1 σ error in RAs
44 A1 --- DE- Sign of the declination (J2000)
45- 46 I2 deg DEd Degree of declination (J2000)
48- 49 I2 arcmin DEm Arcminute of declination (J2000)
51- 57 F7.4 arcsec DEs Arcsecond of declination (J2000)
59- 64 F6.4 arcsec e_DEs The 1 σ error in DEs
66- 71 F6.3 --- Cor Correlation between RA and DE error estimate
73- 75 I3 --- Num Number of observations used from survey sessions
77- 80 A4 --- BCode Band code (2)
81- 85 F5.2 Jy SFlux S-band (2.3GHz) correlated flux density
at 500km baseline
87 A1 --- q_SFlux Quality factor on SFlux (3)
89- 93 F5.2 --- XFlux X-band (8.4GHz) correlated flux density
at 500km baseline
95 A1 --- q_XFlux Quality factor on XFlux (3)
97-100 A4 --- --- [vcs2] Catalog name
--------------------------------------------------------------------------------
Note (1): In JHHMM+DD.d format.
Note (2): Band code:
X/S = An ionosphere-free linear combination of the X-band and S-band
data used for the position determination;
X+ = Only X-band group delays were used, because of the poor quality
of the S-band data;
X-o = Only X-band group delays were used, because no fringes at S
band were detected.
Note (3): Quality factor:
1 = Excellent quality. Little change of signal over all baselines and
stronger than 0.4Jy.
2 = Good quality. Some decrease of signal at shorter baselines, but
stronger than 0.2Jy at all baselines.
3 = Average quality. Decrease of signal at the shorter baselines, but
stronger than 0.10Jy everywhere.
4 = Fair quality. Less than 0.10Jy on the longer baselines, but more
signal on the shorter baselines. These calibrators should be
checked before using.
5 = Poor quality. Less than 0.10Jy on most baselines. These
calibrators should not be used. The positions could be even more
in error than indicated. Most sources within about 10 degrees of
the Galactic plane are significantly broadened by interstellar
scattering at 2.3GHz.
? = Unknown quality.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 12-Jan-2004