J/ApJS/194/25 The VLBA calibrator search for the BeSSeL survey (Immer+, 2011)
The VLBA calibrator search for the BeSSeL survey.
Immer K., Brunthaler A., Reid M.J., Bartkiewicz A., Choi Y.K., Menten K.M.,
Moscadelli L., Sanna A., Wu Y.W., Xu Y., Zhang B., Zheng X.W.
<Astrophys. J. Suppl. Ser., 194, 25 (2011)>
=2011ApJS..194...25I 2011ApJS..194...25I
ADC_Keywords: Positional data ; Galaxies, radio ; Surveys
Keywords: astrometry - Galaxy: general - H II regions -
radio continuum: general - surveys
Abstract:
We present the results of a survey of radio continuum sources near the
Galactic plane using the Very Long Baseline Array (VLBA). Our
observations are designed to identify compact extragalactic sources of
milliarcsecond size that can be used for parallax measurements in the
Bar and Spiral Structure Legacy Survey. We selected point sources from
the NVSS and CORNISH catalogs with flux densities above 30mJy and
within 1.5° of known maser targets. Of the 1529 sources observed,
199 were detected. For sources detected on three or more baselines, we
determined accurate positions and evaluated their quality as potential
calibrators. Most of the 1330 sources that were not detected with the
VLBA are probably of extragalactic origin.
Description:
The survey list are point-like sources from the NVSS (sizes <20") and
CORNISH catalogs (provided by Condon et al. 1998, Cat. VIII/65 and
Purcell et al. 2008ASPC..387..389P 2008ASPC..387..389P) and between one and three sources
from the ICRF28 catalog (Fey et al. 2009ITN....35....1M 2009ITN....35....1M). In total,
1529 sources were selected for observations with the VLBA. We used
eight 16MHz bands, with band center frequencies spanning the range
from 8109.49 to 8583.49MHz.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 65 199 Detected sources
table3.dat 63 1330 *Undetected sources
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Note on table3.dat: The coordinates, coordinate uncertainties, and the fluxes
are extracted from the CORNISH (Purcell et al. 2008ASPC..387..389P 2008ASPC..387..389P) and
NVSS (Cat. VIII/65) point source catalogs.
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See also:
VIII/85 : SPECFIND V2.0 Catalog of radio continuum spectra (Vollmer+ 2009)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
J/MNRAS/390/819 : Combined NVSS-FIRST Galaxies (CoNFIG) sample (Gendre+, 2008)
J/MNRAS/357/1231 : Texas-Oxford NVSS (TONS) radio galaxies (Brand+, 2005)
http://www.mpifr-bonn.mpg.de/staff/abrunthaler/BeSSeL : BeSSeL (Bar and
Spiral Structure Legacy Survey) home page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- [IBR2011] The J2000 source name; JHHMM+DDMM
11 A1 --- f_[IBR2011] [*] Averaged source position (1)
13- 14 I2 h RAh Hour of Right Ascension (J2000)
16- 17 I2 min RAm Minute of Right Ascension (J2000)
19- 26 F8.5 s RAs Second of Right Ascension (J2000)
28 A1 --- DE- Sign of the Declination (J2000)
29- 30 I2 deg DEd Degree of Declination (J2000)
32- 33 I2 arcmin DEm Arcminute of Declination (J2000)
35- 41 F7.4 arcsec DEs Arcsecond of Declination (J2000)
43- 48 F6.1 mas e_RAs ? 1σ uncertainty in RA (2)
50- 55 F6.1 mas e_DEs ? 1σ uncertainty in DE (2)
57 A1 --- Grade [A-F] Compactness grade (3)
59- 62 F4.2 Jy Flux ? Flux density
65 I1 --- Nobs Number of observations
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Note (1): The asterisks mark sources for which the ICRF2 source position
was averaged in with the source position. Weighted means are given
for those calibrators that were observed more than once.
Note (2): The coordinate uncertainties, determined from the quadrature sum
of the formal fitting errors and the error floors for the appropriate
compactness grade. For the grade F sources, the coordinates from the
NVSS catalog were used.
Note (3): Depending on a source's compactness, a grade from A to D was
assigned, representing their quality as a potential calibrator.
Compactness was determined by examining the visibility plots by eye
and estimating the maximum baseline length (in wavelength units) for
which the normalized fringe visibility was greater than 0.2. For
grade A sources, which are the most compact, the normalized fringe
visibility falls below this threshold at >200Mλ. Grade B and C
sources are defined to have normalized visibilities greater than 0.2
for baselines longer than 100 and 50Mλ, respectively. Grade D
sources were more resolved than grade C sources, but still detected on
three or more baselines. Finally, grade F sources were detected on
only one or two baselines. The two shortest VLBA baselines have
lengths of 236km (PT-LA) and 417km (KP-PT).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- [IBR2011] The J2000 source name; JHHMM+DDMM
13- 14 I2 h RAh Hour of Right Ascension (J2000) (1)
16- 17 I2 min RAm Minute of Right Ascension (J2000) (1)
19- 23 F5.2 s RAs Second of Right Ascension (J2000) (1)
28 A1 --- DE- Sign of the Declination (J2000) (1)
29- 30 I2 deg DEd Degree of Declination (J2000) (1)
32- 33 I2 arcmin DEm Arcminute of Declination (J2000) (1)
35- 38 F4.1 arcsec DEs Arcsecond of Declination (J2000) (1)
45- 48 F4.1 arcsec ePos 1σ positional error (1)
59- 63 F5.3 Jy Flux Flux density (1)
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Note (1): values extracted from the NVSS (Cat. VIII/65) or CORNISH catalog
(Purcell et al. 2008ASPC..387..389P 2008ASPC..387..389P), at 1.4GHz or 5GHz.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 19-Sep-2011