Extension of the ICRF for selected areas down to the 15th magnitude

In this paper, we present our results towards the extension of the ICRF to the optical domain down to the 15(th) V magnitude, for some regions of spec ial astronomical interest. This extension is given by accurate positions an d proper motions in the ICRS. Present epoch positions were obtained with th e CCD transit circle of the Abrahao de Moraes Observatory, in the city of V alinhos - Sao Paulo. Proper motion derivation is achieved by combining our meridian circle positions with those from available astrometric catalogues and SERC-J plate measurements performed with the MAMA measuring machine ( P aris). The final result is presented as a catalogue containing positions, p roper motions, magnitudes and cross-identifications with major catalogues f or 41 721 objects. A full description of the employed data is given along w ith an analysis of the uncertainties on positions and proper motions in our final catalogue. On average, stars with V less than or equal to 14.0 have positional precisions better than 50 mas in both coordinates, and 100 mas a t the detection limit of our instrument ( V similar to 16.0). For proper mo tions, average precisions are better than 4 mas/year, whatever the magnitud e, when delta less than or equal to -17 degrees. To the south of this decli nation, precisions become magnitude-dependent, providing figures of 3 mas/y ear when V less than or equal to 12.0 and reaching 17 mas/year at the detec tion limit. The declination dependence affects the fainter stars and reflec ts a feature of our main first epoch material for this magnitude range, the USNO-A2.0 catalogue. The Valinhos CCD transit circle observations cover a variety of regions of great interest. Here, we consider those containing ex tragalactic radio sources, mostly from ICRF, and pre-main sequence stars in southern star-forming regions (Chamaeleon, Lupus and Upper Scorpius - Ophi uchus), where positions from the SERC-J plates were employed.