The kinematics of late type stars in the solar cylinder studied with SDSS data

التفاصيل البيبلوغرافية
العنوان:	The kinematics of late type stars in the solar cylinder studied with SDSS data
المؤلفون:	Fuchs, B., Dettbarn, C., Rix, H. -W., Beers, T. C., Bizyaev, D., Brewington, H., Jahreiss, H., Klement, R., Malanushenko, E., Malanushenko, V., Oravetz, D., Pan, K., Simmons, A., Snedden, S.
سنة النشر:	2009
المجموعة:	Astrophysics
مصطلحات موضوعية:	Astrophysics - Galaxy Astrophysics
الوصف:	We study the velocity distribution of Milky Way disk stars in a kiloparsec-sized region around the Sun, based on ~ 2 million M-type stars from DR7 of SDSS, which have newly re-calibrated absolute proper motions from combining SDSS positions with the USNO-B catalogue. We estimate photometric distances to all stars, accurate to ~ 20 %, and combine them with the proper motions to derive tangential velocities for this kinematically unbiased sample of stars. Based on a statistical de-projection method we then derive the vertical profiles (to heights of Z = 800 pc above the disk plane) for the first and second moments of the three dimensional stellar velocity distribution. We find that = -7 +/- 1 km/s and = -9 +/- 1 km/s, independent of height above the mid-plane, reflecting the Sun's motion with respect to the local standard of rest. In contrast, changes distinctly from -20 +/- 2 km/s in the mid-plane to = -32 km/s at Z = 800 pc, reflecting an asymmetric drift of the stellar mean velocity that increases with height. All three components of the M-star velocity dispersion show a strong linear rise away from the mid-plane, most notably \sigma_{ZZ}, which grows from 18 km/s (Z = 0) to 40 km/s (at Z = 800 pc). We determine the orientation of the velocity ellipsoid, and find a significant vertex deviation of 20 to 25 degrees, which decreases only slightly to heights of Z = 800 pc. Away from the mid-plane, our sample exhibits a remarkably large tilt of the velocity ellipsoid towards the Galactic plane, which reaches 20 deg. at Z = 800 pc and which is not easily explained. Finally, we determine the ratio \sigma^2_{\phi\phi}/\sigma^2_{RR} near the mid-plane, which in the epicyclic approximation implies an almost perfectly flat rotation curve at the Solar radius. Comment: 18 pages, 9 figures, accepted to Astron. J
نوع الوثيقة:	Working Paper
DOI:	10.1088/0004-6256/137/5/4149
URL الوصول:	http://arxiv.org/abs/0902.2324
رقم الأكسشن:	edsarx.0902.2324
قاعدة البيانات:	arXiv

الوصف
DOI:	10.1088/0004-6256/137/5/4149