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Scientific paper
Sep 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002ycat.1283....0h&link_type=abstract
VizieR On-line Data Catalog: I/283. Originally published in: Lick Observatory (September 2002)
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Positional Data, Proper Motions, Magnitudes: Photographic, Colors, Cross Identifications
Scientific paper
The NPM2 Catalog is the second part of the Lick Northern Proper Motion (NPM) program to measure absolute proper motions, on an inertial system defined by some 50,000 faint galaxies, for nearly 400,000 stars over a blue apparent magnitude range from 8 to 18. There are 1246 6x6degree fields in the NPM survey (to declination -23°). The NPM2 Catalog covers the 28% of the northern sky lying near the plane of the the Milky Way and contains some 230,000 stars in the 347 NPM fields remaining after the 1993 NPM1 Catalog (149,000 stars in 899 fields away from the Milky Way).
Each NPM field was photographed with the 51 cm Carnegie Double Astrograph at two epochs between 1947 and 1988. The mean first and second epochs are 1950 and 1977; the average epoch difference is 27 years. The first-epoch plates were taken in the blue only; both blue and yellow plates were taken at the second epoch. For NPM2, the plates were scanned by the Precision Measuring Machine (PMM) at the US Naval Observatory, Flagstaff. From the PMM scans, some 120,000 faint (B>14) stars were chosen anonymously for the NPM astrometric reductions and for statistical studies of stellar motions. In addition, the NPM2 catalog contains some 80,000 bright (B<14) positional reference stars, mostly from the Tycho-2 Catalogue, and some 35,000 stars chosen for astronomical interest from Klemola's "Lick Input Catalog of Special Stars" (ICSS). Details of the NPM2 star selection, data reductions, and catalog compilation will be presented in a paper being prepared for the Astronomical Journal.
The present version (September 2002) of the NPM2 Catalog contains 196,639 stars from 295 of the 347 NPM2 fields (85%). The remaining 52 fields, in the Summer Milky Way from -02 to -23°, are now being processed, and will be added to the catalog in 2003. Together with the NPM1 Catalog (J2000 version at http://www.ucolick.org/~npm/NPM1/) the NPM2 Catalog completes the Lick Northern Proper Motion program after more than a half-century of work by three generations of Lick Observatory astronomers.
The NPM2 catalog gives J2000 positions computed for the catalog epoch 2000, and is in the form of 108 one-degree declination zone files (e.g. z+83n) from +83 to -23°. Following the convention of the NPM1 catalog, each NPM2 star has an NPM2 "name" (e.g. +83.0001) reflecting the declination zone and a running number in right ascension order within the zone.
Each star's entry includes the absolute proper motion and blue (B) magnitude. For 98.5% of the stars the B-V color is also given. Other data given for each star are: the original mean epoch, a stellar class code, the number of NPM fields on which the star was measured, and discrepancy flags for proper motion, and photometry. Tycho-2 numbers are given for the primary positional reference stars (40% of NPM2); for these stars the Tycho B,V photometry, transformed to Johnson B and B-V, is listed in preference to the NPM2 photographic photometry. ACRS and Hipparcos numbers are also given for NPM2 stars selected from those catalogs.
The RMS errors of the NPM2 absolute proper motions are about 0.6"/centy (6mas/yr) in each coordinate, comparable to the NPM1 errors. The RMS position errors at the NPM2 catalog epoch 2000 average about 0.2" (200mas) in each coordinate, due mostly to the accumulated proper motion error from original plate epochs (average 1968) to 2000. The pure positional errors at the original epochs average 0.08" (80mas) in each coordinate. The RMS errors for the NPM photographic photometry average about 0.18mag in B, and 0.20mag in B-V.
We thank the National Science Foundation for its long-term support of the NPM program. The NPM2 phase was supported by NSF grants AST-9530632 and AST-9988105. We thank the Yale Southern Proper Motion group (W. van Altena, I. Platais, and T. Girard) for their help in developing software to process the PMM plate scans.
(1 data file).
Hanson Robert B.
Jones Burton F.
Klemola Arnold R.
Monet David G.
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