The second goal, is to improve the position accuracy of the Pan-STARRS catalog, which is currently under construction. The PanSTARRS survey covers the δ > -31° portion of the sky, with field of view (FoV) of approximately 7 square degrees. The current astrometric accuracy of PanSTARRS catalog has been achieved using a general purpose pipeline and referencing to the 2MASS catalog. However, this methodology significantly underperforms compared to the expected photon noise error floor. We propose a new method to do the PanSTARRS astrometry, a so-called "global astrometry" method, which was originally developed for the (now defunct) SIM project. In the past, the grid of extragalactic sources with high position accuracies has been too sparse to implement this global astrometry technique. However, using numerical simulations, we find that when at least 1 source with milliarcsecond VLBI position accuracy is present in a field, then a robust, one-step astrometric adjustment of source positions over the entire 3π sky can be successfully performed. An accurate PanSTARRS astrometric catalog is important for various applications, such as correct identification of transient X-ray and gamma-ray sources, a proper astrometric calibration of the Kepler telescope field, detection of nearby faint stars and high-proper motion halo population, Galactic dynamics studies, characterization of tidal streams of stars on the outskirts of the Galaxy, as well as other specific US DoD applications. We propose to observe candidate sources in the areas that have less than 1 source per PanSTARRS FoV, especially at higher Galactic latitudes to avoid crowding and extinction issues.
The third goal, 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 fourth goal is to extend the legacy source list. The calibrator list with positions known at a milli-arcsecond level of accuracy accompanied with brightness distributions in fits format at several frequencies is used for many studies beyond phase-calibration and population analysis. This includes identification of AGNs, generation of parent lists for high frequency surveys, lists of targets for space navigation, etc. For 18 years, VLBA spent ~1000 hours for intensive surveys, or about 1%. But this 1% observing time yielded 2/3 of the total number of objects ever detected with VLBA. In a long term, the list of detected sources, their positions and images will be treated as a legacy of the array.
| The number of segments observed: | 10 | |
| The number of sources observed: | 1218 | |
| The number of segments correlated: | 10 | |
| The number of target sources correlated: | 1208 | |
| The number of target sources detected at any band: | 753 | |
| The number of target sources detected at C-band: | 750 | |
| The number of target sources detected at X-band: | 714 | |
| Detection rate: | 62% |
The catalogue of source positions from C-band observations:
vcs8_c.sou
The catalogue of source positions from X-band observations:
vcs8_x.sou
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