Densification of the VLBA Calibrator Survey (VCS9)

Goals

Goals of the project:

1. To improve astrometric accuracy of Pan-STARRS and future LSST catalogs by extending the spacial coverage of VLBI astrometric catalogue to that level that any field of view of PanSTARRS (disk of 1.5° radius) and/or LSST (disk of 1.75° radius) will be guaranteed to have at least one VLBI calibrator.

   At the moment the probability to find a VLBI detected source with position accuracy 5 mas or better at any Pan-STARRS field is 77%. The goal of our project is to find a calibrator in remaining 22.2% of the sky.

2. To study of the population of steep spectrum sources.. Due to a heavy selection bias, the population of steep spectrum sources is poorly studied.
   We are going to observe all remaining sources from GB6 and PMN at $\delta > -30^\circ$ brighter 200~mJy at 4.85~GHz that were not previously observed with VLBI. This is approximately 1/3 of this flux-limited sample (remaining 2/3 have already been observed). Proposed observations will generate a flux-limited unbiased sample of 7177 objects. We will perform a population analysis with the goal to understand the difference in physics of of parsec-scale emission of flat-spectrum and steep-spectrum sub-samples.
3. To study of a sample of 200 sources with large radio-optical offsets (250—800 mas) that we found by analyzing differences between the RFC and positions from the preliminary PanSTARRS catalogue. At the moment, we do not know whether these displacements are due to errors in VLBI positions, or in optical positions, or as \citet{r:zah,r:fre} claim they may be real displacements. The latter claim seems highly controversial from a radio astronomer point of view, but nevertheless, a definite proof is required to solve this mystery. We would like first to get reliable positions and images of these sources and then follow-up a clean sample with large optical telescopes.
4. Community service, is to improve the list of calibrators for phase referencing. These observations will allow us to produce the accumulative list of calibrators that are strong enough at longest baselines for being detected for less than one minute at 2048 Mbps. The list will be dense enough to guarantee finding a calibrator in a circle of a radius of 2° at any target. Proposed organization of observations will also allow a user to order a candidate for a calibrator for his or her proposal.

The list of observed sources.

Status on 2017.08.02

The number of target sources observed:	10766
The number of calibrator sources observed:	244
The number of segments observed:	99
The number of segments correlated:	99
The number of segments fringe fit in fine mode:	99
The number of segments with preliminary solution:	99
The number of segments fully processed:	99
The number of target sources detected at any band:	5447
The number of target sources detected at C-band:	5436
The number of target sources detected at X-band:	4839
The number of new sources detected any band:	4855
Detection rate:	51%
Number of processed visibilites:	482,352,263
Nominal campaign duration:	530 hours
On source time:	342 hours
Dataset size	52.7 Tb
Amount of raw data:	3 Pb Tb

The catalogue of positions of 5436 target sources from C-band observations: vcs9_c.sou
The catalogue of positions of 4842 target sources from X-band observations: vcs9_x.sou

The list of source that were observed, but not detected at C-band
The list of source that were observed, but not detected at X-band

Change Log

Back to astronomy projects.

This web page was prepared by Leonid Petrov ()
Last update: 2018.06.03_21:14:35