EDP Sciences
Free Access
Volume 372, Number 3, June IV 2001
Page(s) 833 - 850
Section Extragalactic astronomy
DOI https://doi.org/10.1051/0004-6361:20010366
Published online 15 June 2001

A&A 372, 833-850 (2001)
DOI: 10.1051/0004-6361:20010366

Kinematics of young stars

II. Galactic spiral structure
D. Fernández1, F. Figueras1, 2 and J. Torra1, 2

1  Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain
2  IEEC (Institut d'Estudis Espacials de Catalunya), Edif. Nexus-104, Gran Capità 2-4, 08034 Barcelona, Spain

(Received 9 February 2001 / Accepted 8 March 2001)

The young star velocity field is analysed by means of a galactic model which takes into account solar motion, differential galactic rotation and spiral arm kinematics. We use two samples of Hipparcos data, one containing O- and B-type stars and another one composed of Cepheid variable stars. The robustness of our method is tested through careful kinematic simulations. Our results show a galactic rotation curve with a classical value of A Oort constant for the O and B star sample ( AOB = 13.7-13.8 km s-1 kpc-1) and a higher value for Cepheids ( ACep = 14.9-16.9 km s-1 kpc-1, depending on the cosmic distance scale chosen). The second-order term is found to be small, compatible with a zero value. The study of the residuals shows the need for a K-term up to a heliocentric distance of 4 kpc, obtaining a value K = -(1-3) km s-1 kpc-1. The results obtained for the spiral structure from O and B stars and Cepheids show good agreement. The Sun is located relatively near the minimum of the spiral perturbation potential ( $\psi_\odot = 284$-20$\degr$) and very near the corotation circle. The angular rotation velocity of the spiral pattern was found to be $\Omega_{\mathrm{p}} \approx 30$ km s-1 kpc-1.

Key words: Galaxy: kinematics and dynamics -- Galaxy: solar neighbourhood -- Galaxy: structure -- stars: early-type -- stars: kinematics -- stars: variables: Cepheids

Offprint request: D. Fernández, dfernand@am.ub.es

SIMBAD Objects

© ESO 2001

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.