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A new UBV and proper motion survey in the anticentre direction at intermediate galactic latitude: Kinematics of the Galaxy's stellar populations
We present the results from a new complete absolute proper motion surveyin the direction of intermediate galactic latitude (L = 167.5 deg, b =47.4 deg) with respect to background galaxies and quasars, using a setof Tautenburg and OCA (Observatoire de la Cote d'Azur) Schmidt plates,obtained at different epochs separated by approximately 25 years.Photometric U, B and V survey has been done for 4167 objects covering18.8 square degree field and proper motions have been calculated for1888 objects for a 8.6 deg2 area. The resulting catalogs arecomplete down to V = 17, B = 19 and U = 16.5. An average proper motionaccuracy of 0.25 sec per century was achieved for stars brighter than V= 16, with the uncertainties increasing to approximately 0.4 sec percentury at V greater than 16. The photometric accuracy ranges between0.07 to 0.10 in the three bands. We utilize our photometric and absoluteproper motions data to investigate the structure and kinematics of theGalaxy. We have determined ultraviolet excesses and distances for asub-sample of 2685 stars in the color range 0.3 less than or equal to(B-V) less than or equal to 0.9 and with V less than or equal to 17.Thus we have been able to probe the kinematical distribution of F andG-type stars to distances up to 3.5 kpc from the plane. We obtain avalue -0.21 +/- 0.1/kpc for the galactic radial gradient of velocitydispersion. By comparing the ratio of stars in this direction to thenumber of stars towards galactic center at intermediate latitude (l =3deg, b = 47 deg), give a strong evidence that the scale length of olddisk is rather short (2-2.5 kpc). Because of the kinematical biasesinherent in our data sample, we can not present definite kinematicalparameters for the intermediate population, but reasonable estimateswould be an asymmetric drift of 57 +/- 4 km/s and velocity dispersion of60 +/- 3 km/s at a mean distance (above the plane) of z = 2 kpc.
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Osservazione e dati astrometrici
| Costellazione: | Orsa Maggiore |
| Ascensione retta: | 09h41m26.79s |
| Declinazione: | +49°21'40.1" |
| Magnitudine apparente: | 8.986 |
| Moto proprio RA: | -5.4 |
| Moto proprio Dec: | -2.9 |
| B-T magnitude: | 10.233 |
| V-T magnitude: | 9.089 |
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