J/AJ/142/35 The VLBA Galactic Plane Survey (VGaPS) (Petrov+, 2011)
The VLBA Galactic Plane Survey. VGaPS.
Petrov L., Kovalev Y.Y., Fomalont E.B., Gordon D.
<Astron. J. 142, 35 (2011)>
=2011AJ....142...35P 2011AJ....142...35P
ADC_Keywords: Positional data ; VLBI ; Fundamental catalog ; Radio sources
Keywords: astrometry - catalogs - surveys
Abstract:
We presents accurate absolute positions from a 24 GHz Very Long
Baseline Array (VLBA) search for compact extragalactic sources in an
area where the density of known calibrators with precise coordinates
is low. The goals were to identify additional sources suitable for use
as phase calibrators for galactic sources, determine their precise
positions, and produce radio images. In order to achieve these goals,
we developed a new software package, PIMA, for determining group
delays from wide-band data with much lower detection limit. With the
use of PIMA we have detected 327 sources out of 487 targets observed
in three 24 hour VLBA experiments. Among the 327 detected objects, 176
are within 10 degrees of the Galactic plane. This VGaPS catalogue of
source positions, plots of correlated flux density versus projected
baseline length, contour plots, as well as weighted CLEAN images and
calibrated visibility data in FITS format, are available on the Web at
http://astrogeo.org/vgaps. Approximately one half of objects from the
24GHz catalogue were observed at dual band 8.6GHz and 2.3GHz
experiments. Position differences at 24GHz versus 8.6/2.3GHz for all
but two objects on average are strictly within reported uncertainties.
We found that for two objects with complex structure positions at
different frequencies correspond to different components of a source.
Description:
The VGaPS catalogue of positions and correlated flux densities of 327
target sources observed with the Australian Long Baseline Array in the
absolute astrometry mode.
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 at projected spacings greater than 400Mλ.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table9.dat 90 327 VGaPS catalogue
table10.dat 65 160 The list of 160 sources that have not been
detected in VGaPS observations
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See also:
J/MNRAS/414/2528 : LBA Calibrator Survey. LCS1. (Petrov+, 2011)
Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1 A1 --- Cat [CNU] Category: Calibrator, Non-calibrator,
or Unreliable coordinates
3- 10 A8 --- Bname IVS B1950 source name
12- 21 A10 --- Jname IAU J2000 source name
23- 24 I2 h RAh Right ascension (J2000.0)
26- 27 I2 min RAm Right ascension (J2000.0)
29- 37 F9.6 s RAs Right ascension (J2000.0)
39 A1 --- DE- Declination sign (J2000.0)
40- 41 I2 deg DEd Declination (J2000.0)
43- 44 I2 arcmin DEm Declination (J2000.0)
46- 53 F8.5 arcsec DEs Declination (J2000.0)
55- 60 F6.2 mas e_RAs Inflated right ascension position uncertainty
(without cos(δ) factor)
62- 67 F6.2 mas e_DEs Inflated declination position uncertainty
69- 74 F6.3 --- Corr [-1/1] Correlation between estimates of right
ascension and declination
76- 79 I4 --- Nobs Number of used observations
81- 84 F4.2 Jy Ftot K-band (22GHz) total correlated flux density
integrated over entire map
86 A1 --- l_Func Limit flag on Func
87- 90 F4.2 Jy Func K-band (22GHz) unresolved correlated flux
density at long VLBA baselines
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Byte-by-byte Description of file: table10.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Bname The IVS source name; B1950.0
10- 19 A10 --- Jname The IAU source name; J2000.0
21- 22 I2 h RAh Hour of Right Ascension (J2000)
24- 25 I2 min RAm Minute of Right Ascension (J2000)
27- 32 F6.3 s RAs Second of Right Ascension (J2000)
34 A1 --- DE- Sign of the Declination (J2000)
35- 36 I2 deg DEd Degree of Declination (J2000)
38- 39 I2 arcmin DEm Arcminute of Declination (J2000)
41- 45 F5.2 arcsec DEs Arcsecond of Declination (J2000)
47- 51 F5.1 deg GLAT Galactic latitude
53- 56 I4 mJy Flux ? Flux density extrapolated at 22GHz
58- 62 F5.2 --- alpha ? Spectral index α
(in sense F∝να)
64- 65 I2 --- o_alpha Number of points for α computation
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Acknowledgements:
Leonid Petrov, Leonid.Petrov(at)lpetrov.net
(End) Patricia Vannier [CDS] 28-Jun-2011