J/AJ/142/89 Precise astrometry with VLBA (VIPS) (Petrov+, 2011)
Precise absolute astrometry from the VLBA imaging and polarimetry survey
at 5 GHz.
Petrov L., Taylor G.B.
<Astron. J., 142, 89 (2011)>
=2011AJ....142...89P 2011AJ....142...89P
ADC_Keywords: Positional data ; VLBI ; Fundamental catalog ; Radio sources
Keywords: astrometry - catalogs - surveys
Abstract:
We present accurate positions for 857 sources derived from the
astrometric analysis of 16 eleven-hour experiments from the Very Long
Baseline Array imaging and polarimetry survey at 5GHz (VIPS). Among
the observed sources, positions of 430 objects were not previously
determined at milliarcsecond-level accuracy. For 95% of the sources
the uncertainty of their positions ranges from 0.3 to 0.9mas, with a
median value of 0.5mas. This estimate of accuracy is substantiated by
the comparison of positions of 386 sources that were previously
observed in astrometric programs simultaneously at 2.3/8.6GHz.
Surprisingly, the ionosphere contribution to group delay was
adequately modeled with the use of the total electron content maps
derived from GPS observations and only marginally affected estimates
of source coordinates.
Description:
The VIPS position catalog presents coordinates of 857 target sources
observed with the Very Long Baseline Array at 5GHz.
The catalogue contains the following information: source positions,
their inflated uncertainties and correlation coefficients between
right ascension and declination; the number of observations used; the
total correlated flux density computed as a sum of all CLEAN
components and its uncertainty; and the correlated flux density of the
unresolved component computed as the median of correlated flux density
values measured different projected spacings at 5, 8.4, 15, and 22GHz.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 122 857 VIPS (Very Long Baseline Array imaging and
Polarimetry Survey) catalog of 857 sources
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See also:
J/ApJ/658/203 : VLBA imaging and polarimetry survey at 5GHz (Helmboldt+, 2007)
J/ApJ/671/1355 : EGRET blazars in VIPS (Taylor+, 2007)
J/AJ/143/35 : KCAL VERA 22 GHz calibrator survey (Petrov+, 2012)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 A1 --- n_IVS [XC] Source flag (1)
3- 10 A8 --- IVS The IVS (International VLBI Service) name (B1950)
12- 21 A10 --- IAU The IAU name (J2000)
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- 59 F5.2 mas e_RAs Inflated error in RAs
61- 65 F5.2 mas e_DEs Inflated error in DEs (without cosDE factor)
67- 72 F6.3 --- Corr [-1/1] Correlation between RA and DE
74- 77 I4 --- Nobs Number of observations used
79- 84 F6.3 Jy Stot ?=-1 Total S band (2.3GHz) flux density (3)
86- 91 F6.3 Jy Sunr ?=-1 Unresolved S band (2.3GHz) flux density (4)
93 A1 --- l_Ctot Limit flag on CTot (2)
94- 99 F6.3 Jy Ctot ?=-1 Total C band (5GHz) flux density (3)
101 A1 --- l_Cunr Limit flag on CUnr (2)
102-107 F6.3 Jy Cunr ?=-1 Unresolved C band (5GHz) flux density (4)
109 A1 --- l_Xtot Limit flag on XTot (2)
110-115 F6.3 Jy Xtot ?=-1 Total X band (8.6GHz) flux density (3)
117-122 F6.3 Jy Xunr ?=-1 Unresolved X band (8.6GHz) flux density (4)
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Note (1): "X" if the sources was previously detected at X (8.6GHz) and S
(2.3GHz) bands under absolute astrometry programs, "C" otherwise.
Note (2): A "<" indicates the upper limit of the flux density is present in
the following column.
Note (3): Integrated over entire map.
Note (4): At long VLBA baselines.
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Acknowledgements:
Leonid Petrov, Leonid.Petrov(at)lpetrov.net
(End) Patricia Vannier [CDS] 01-Mar-2012