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J/AJ/146/5     Optically Bright extragalactic Radio Sources II    (Petrov, 2013)

The catalog of positions of optically bright extragalactic radio sources OBRS-2. Petrov L. <Astron. J., 146, 5 (2013)> =2013AJ....146....5P
ADC_Keywords: VLBI ; Radio sources ; Surveys Keywords: astrometry - catalogs - surveys Abstract: Future space-borne astrometry missions, such as Gaia, will be able to determine the optical positions of hundreds of quasars with submilliarcsecond accuracies comparable to those achieved in radio by very long baseline interferometry (VLBI). Comparisons of coordinate systems from space-borne missions and VLBI will be very important, first for investigations of possible systematic errors and second for investigations of possible shifts between centroids of radio and optical emissions in active galactic nuclei. In order to make such a comparison more robust, a program for densification of the grid of radio sources detectable with both VLBI and Gaia was launched in 2006. Program sources are 398 quasars with declinations >-10° that are brighter than 18mag at the V band. The first two observing campaigns were run in 2007-2008. In the third campaign, a set of 291 objects from that list was observed with the VLBA+EVN in 2010-2011 with the primary goal of producing their images with milliarcsecond resolution. In this paper, following the method of absolute astrometry, coordinates of observed sources have been derived with milliarcsecond accuracies from analysis of these observations. The catalog of positions of 295 target sources, estimates of their correlated flux densities at 2.2 and 8.4GHz, and their images are presented. The accuracies of source coordinates are in a range of 2-200mas, with a median of 3.2mas. Description: The first VLBI (Very Long Baseline Interferometry) observing campaign in 2007 resulted in the detection of 398 targets with the European VLBI Network (EVN; Bourda et al., 2010, cat. J/A+A/520/A113). During the second observing campaign, a subset of 105 sources detected in the previous campaign was observed (Bourda et al., 2011, cat. J/A+A/526/A102). Their positions were derived by Petrov (2011, cat. J/AJ/142/105) and formed the OBRS-1 (Optically Bright extragalactic Radio Sources) catalog. The remaining sources were observed in the third campaign, called OBRS-2. During the OBRS-2 campaign, there were three observing sessions with 10 VLBA (Very Long Baseline Array) stations and 5-6 EVN stations from this list: EFLSBERG, MEDICINA, ONSALA60, YEBES40M, DSS63, HARTRAO, and NOTO. Observations were made on 2010 Mar 23 (session ID gc034a), on 2011 Nov 8 (gc034bcd), and on 2011 Mar 15 (gc034ef). The OBRS-2 catalog presents precise positions of the 295 extragalactic radio sources as well as median correlated flux densities at 8.4 and 2.2GHz at baseline lengths shorter than 900km and at baseline lengths longer than 5000km. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 120 295 The OBRS-2 source VLBI position catalog
See also: VII/258 : Quasars and Active Galactic Nuclei (13th Ed.) (Veron+ 2010) I/323 : International Celestial Reference Frame 2, ICRF2 (Ma+, 2009) I/251 : VLBI International Celestial Reference Frame ICRF (Ma+ 1997) J/A+A/544/A34 : Bright AGN VLBI imaging study at 2 and 8GHz (Pushkarev+, 2012) J/MNRAS/416/1097 : The EVN Galactic Plane Survey - EGaPS (Petrov, 2012) J/MNRAS/414/2528 : LBA Calibrator Survey (LCS1) (Petrov+, 2011) J/AJ/142/105 : Optically Bright Extragalactic Radio Sources (Petrov+, 2011) J/AJ/142/35 : The VLBA Galactic Plane Survey (VGaPS) (Petrov+, 2011) J/A+A/526/A102 : VLBI imaging of 105 extragalactic radio sources (Bourda+, 2011) J/A+A/520/A113 : VLBI detection of 398 extragalactic radio sources (Bourda+, 2010) J/AJ/136/580 : Sixth VLBA calibrator survey: VCS6 (Petrov+, 2008) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 10 A10 --- JName IAU source name (JHHMM+DDMM) 12- 19 A8 --- BName IVS source name (HHMM+DDd; B1950) (1) 22- 23 I2 h RAh Hour of Right Ascension (J2000) 25- 26 I2 min RAm Minute of Right Ascension (J2000) 28- 36 F9.6 s RAs Second of Right Ascension (J2000) 38 A1 --- DE- Sign of the Declination (J2000) 39- 40 I2 deg DEd Degree of Declination (J2000) 42- 43 I2 arcmin DEm Arcminute of Declination (J2000) 45- 52 F8.5 arcsec DEs Arcsecond of Declination (J2000) 55- 60 F6.2 mas e_RAs Uncertainty in RAs (without cosδ factor) 62- 67 F6.2 mas e_DEs Uncertainty in DEs 70- 75 F6.3 --- Corr [-1/1] Correlation coefficient between the uncertainties in RAs and DEs 78 A1 --- B [SX] Band used for deriving positions: S (2.2GHz) or X (8.4GHz) 80- 82 I3 ---- NS [0/385] Number of used observations at S-band 84- 86 I3 ---- NX [0/381] Number of used observations at X-band 88- 93 F6.3 Jy F(S)s ?=-1.000 Median value of the correlated "short" flux density at the S-band (2.2GHz) (2) 95 A1 --- l_F(S)l [<] Upper limit flag on FlS (detection limit) 96-101 F6.3 Jy F(S)l ?=-1.000 Median value of the correlated "long" flux density at the S-band (2.2GHz) (2) 103-108 F6.3 Jy F(X)s ?=-1.000 Median value of the correlated "short" flux density at the X-band (8.4GHz) (2) 110 A1 --- l_F(X)l [<] Upper limit flag on FlX (detection limit) 111-116 F6.3 Jy F(X)l ?=-1.000 Median value of the correlated "long" flux density at the X-band (8.4GHz) (2) 118 A1 --- S [m] A map at S-band is available 120 A1 --- X [m] A map at X-band is available
Note (1): International VLBI Service for geodesy and astrometr; <IVS BHHMM+DDd> in Simbad. Note (2): "short" and "long" mean: short = at baseline projection lengths shorter than 900km. long = at baseline projection lengths longer than 5000km. This estimate serves as a measure of the correlated flux density of an unresolved component.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 04-Jun-2014
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