A Rediscussion of Determinations of Precession and Galactic Rotation from Lick Proper Motions Referred to Galaxies
Abstract
Summary. A determination of precessional corrections from differences between the published AGK3 proper motions and the Lick proper motions measured with reference to galaxies has been made. The "systematic trend" in right ascension detected by Vasilevskis and KIemola (1971) was confirmed. There are, however, strong indications that the effect is a consequence of the use of different photographic systems of measurement and not a consequence of star streaming. With the application of corrections due to this effect the proper motion differences AGK3-Lickcorr have yielded the centennial values of the precessional corrections Api = +0':95 + 0' l5 (m.e.) and AA + Ae = +l':2l + 0'.'l6 (m.e.) per century following from the directly determined values An = +0':38 + 0' 06 (m.e.) and Ak = -0:34 + 0:11 (m.e.) per century. An analysis of the proper motions of the faintest Lick stars which, according to their authors, appear to be well measured, yielded Oort's constants A = +8.5 i 2.4 (m.e.)kms-1kpc-1 and B = -15.2 + 1.9 (me.) km i kpc -1 on the basis of the Oort-Lindblad model of galactic rotation. The it6-soluflon yielded A = +13.7 + 3.3 (m.e.) km - 1 kpc- . The application of the threedimensional model proposed by Ogorodnikov (1932) and Milne (1935) has not yielded significant results for the parameters of the streaming field. Key words: galactic rotation - precessional corrections - proper motions
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 1978
- Bibcode:
- 1978A&A....66..441D
- Keywords:
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- Galactic Rotation;
- Precession;
- Astronomical Models;
- Error Analysis;
- Stellar Motions;
- Astronomy