VLBA Calibrator Survey 4 (VCS4)

Summary

Here the fourth extension to the Very Long Baseline Array (VLBA) Calibrator Survey, containing 262 new sources not previously observed with very long baseline interferometry (VLBI) is presented. The survey, based on three 24 hour VLBA observing sessions, fills the areas on the sky above declination -40o where the calibrator density is less than one source within a 4o radius disk at any given direction. The positions were derived from astrometric analysis of the group delays determined at 2.3 and 8.6 GHz frequency bands using the Calc/Solve software package. The VCS4 catalogue of source positions, plots of correlated flux density versus the length of projected baseline, contour plots and fits files of naturally weighted CLEAN images as well as calibrated visibility function files are available at this page.

Publication:
L. Petrov, Y.Y. Kovalev, E. Fomalont, D. Gordon "The Fourth VLBA Calibrator Survey - VCS4", Astronomical Journal, vol. 131, pp. 1872-1879, 2006.    Preprint: astro-ph/0508506    Full text   (PS + gzip, 307Kb )    PDF-file.

Observations

There were three observing sessions, each 24 hour long: VCS4a, VCS4b and VCS4c:
VCS4a was observed from 2005.05.12_16:50 till 2005.05.13_16:51
VCS4b was observed from 2005.06.01_22:01 till 2005.06.02_22:02
VCS4c was observed from 2005.06.30_18:51 till 2005.07.01_18:52

Date Experiment Session URL for downloading Size (bytes)
2005.05.12 vcs4a $05MAY12XV ftp://cddis1.gsfc.nasa.gov/vlbi/raw/fits/2005_05_12_vcs4a_fits.tar.bz2 11,107,097,761
2005.06.01 vcs4b $05JUN01XV ftp://cddis1.gsfc.nasa.gov/vlbi/raw/fits/2005_06_01_vcs4b_fits.tar.bz2 11,301,138,116
2005.06.30 vcs4c $05JUN30XV ftp://cddis1.gsfc.nasa.gov/vlbi/raw/fits/2005_06_30_vcs4c_fits.tar.bz2 11,298,227,225

Results

  1. VCS4 catalogue in HTML form. The catalogue contains positions os 289 targeted sources, their uncertainties, estimates of the total VLBA flux density, the VLBA flux density of unresolved components, naturally weighted CLEAN images in postscript and in fits format at X and S-band; plots of the correlated flux density as a function of the length of the baseline projection to the source plane; fits files with calibrated uv data.
  2. VCS4 catalogue in ASCII format. The catalogue contains source positions, their uncertainties, total VLBA flux density, the VLBA flux density of unresolved components.
  3. Catalogue in HTML form of 96 sources used as tropospheric calibrators. The catalogue contains source positions, their uncertainties, estimates of the total VLBA flux density, the VLBA flux density of unresolved components, naturally weighted CLEAN images in postscript and in fits format at X and S-band; plots of the correlated flux density as a function of the length of the baseline projection to the source plane; fits files with calibrated uv data.
  4. Catalogue in ASCII format of 96 sources used as tropospheric calibrators.
  5. All images and uv data in one tar.bz2 file (309Mb). Refer to the readme file for the file name convention in this archive.

262 new sources and 27 previusly observed sources were detected. 196 of them are suitable as calibrators (more than 8 X/S good observations, semi-major error ellipse is less than 25 nrad (5 mas)). The area of the sky above declination -40o with sky source density less than one calibrator in the disk of radius 4o was reduced from 4.6% to 1.9%.

These two plots showed by green color the regions with sky density less than one source in a radius of 4o at a given direction at declination -45o degrees and greater.

Before VCS4

 

 

 

After VCS4


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Last update: 16-MAR-2006 10:21:55
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