Galactic Rotation Parameters Research Articles

Galactic disk kinematics traced by low-altitude stars of 55 km/s mean transverse velocity within 500 PC from the sun

The Galactic disk velocity field in a 500 pc radius solar neighborhood is mapped on the basis of a set of 75,000 stars at an altitude lower than 300 pc above the Galactic plane and with a 55 km/s mean transverse velocity. An age range of 5 Gyr is inferred from the ellipsoidal distribution of the velocities in the Galactic plane. A circular motion with an expansion of 21 +/-12 km/s kpc was observed, suggesting a nonflat rotation cure, even when the young Gould's Belt stars are removed. A velocity gradient of 0.3 km/s pc delineates the shock front of large known clouds in the Pleiades, the Hyades, the Perseus, and the Scorpio-Ophiucus regions, suggesting that the Galactic differential rotation parameters describing stellar streaming cannot be segregated from the interstellar medium velocity. A transverse velocity dispersion increase of 3 km/s over a 50-pc cell size is noticeable in the Pleiades only. An 8 +/-4 km/s heating process of the local stellar disk during an encounter with dust clouds near an 18 +/-4 km/s transverse velocity is suggested.

Variation of galactic rotation parameters with distance scale

view Abstract Citations (3) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Variation of galactic rotation parameters with distance scale Howard, William E., III ; Kirk, John G. Abstract The radial velocities of 144 Cepheids and 39 galactic clusters are analyzed by means of a higher-order expansion of the galactic rotation equation, assuming pure circular rotation. Provision is made to determine the galactic rotation parameters simultaneously and to investigate the effects on these parameters of varying the distance scale. The Cepheid and cluster distance scales are found to agree to within 3.5%. Various other galactic models are compared with a final composite model derived here which has the following parameters: R5= 11.4 kpc; '= -2.29 km/sec-kpc2 ws" $0.35 km/sec-kpc2 W = -0.1 km/sec-kpc4 A = 13.1 km/sec-kpc; K= -3.3 km/sec; LO, BO, VO (adopted) =58 4, $21 5,16.4 km/sec, respectively. Publication: The Astronomical Journal Pub Date: August 1965 DOI: 10.1086/109758 Bibcode: 1965AJ.....70..434H full text sources ADS |

Determination of the Galactic Rotation Parameters from Cepheid Radial Velocities and their Variation with the Distance Scale.

Determination of the Galactic Rotation Parameters from Cepheid Radial Velocities and their Variation with the Distance Scale.