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
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) and between one and three sources from the ICRF28 catalog (Fey et al. 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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 65 199 Detected sources table3.dat 63 1330 *Undetected sources
Note on table3.dat: The coordinates, coordinate uncertainties, and the fluxes are extracted from the CORNISH (Purcell et al. 2008ASPC..387..389P) and NVSS (Cat. VIII/65) point source catalogs.
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
Bytes Format Units Label Explanations
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 ? 1sigma uncertainty in RA (2) 50- 55 F6.1 mas e_DEs ? 1sigma 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
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).
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
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 1sigma positional error (1) 59- 63 F5.3 Jy Flux Flux density (1)
Note (1): values extracted from the NVSS (Cat. VIII/65) or CORNISH catalog (Purcell et al. 2008ASPC..387..389P), at 1.4GHz or 5GHz.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 19-Sep-2011
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