Astrometric Representation of the Gaia Extragalactic Reference Frame from Ground Observations

Details Astrometric Representation of the Gaia Extragalactic Reference Frame from Ground Observations Astrometric Representation of the Gaia Extragalactic Reference Frame from Ground Observations

Jan 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005esasp.576..275a&link_type=abstract

"Proceedings of the Gaia Symposium "The Three-Dimensional Universe with Gaia" (ESA SP-576). Held at the Observatoire de Paris-Me

Astronomy and Astrophysics

Astronomy

1

Gaia, Reference Frame, Quasar

Scientific paper

The Gaia Extragalactic Celestial Reference Frame (GCRF) will be formed by about 500 000 quasars, up to magnitude G = 20, defined to typical precision of 50 µas. The GCRF is pivotal for many of the mission objectives, starting with the astrometry catalogue. Yet the pre-mission representation of the GCRF is complicated because of the comparatively small number of observed quasars. Here, we present a restricted representation of the GCRF, based on the V´eron-Cetty & V´eron list of 48 921 quasars. This representation brings the original list to a fully coherent placement on the ICRS. The source positions have been collected from the USNO B1.0 catalogue, which is complete to V = 20. Around each of them, fields of size as small as 6 were detailed, in which were picked up B1.0 stars and their corresponding positions from catalogs extending the HCRS to dimmer magnitudes. The UCAC2 (48 million stars, to RV = 16, precise to 30 mas) and the 2MASS (470 million objects, complete to J = 16, precise to 100 mas) acted as the astrometric reference catalogs. Taking as paradigm the B1.0 positions corrected by the UCAC2, a reference frame is obtained containing 37 513 quasars, globally aligned to 1mas with the ICRF. The optical minus radio standard deviation is at 150 mas, much smaller therefore than the nominal 200 mas B1.0 accuracy (the o-r standard deviation is above 300 mas for the original V&V entries). The extragalactic reference frame obtained in this manner enables us to gather insights on the distribution and luminosity of the GCRF. At the same time it provides a useful frame for all-purpose observations.

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