Local stellar kinematics from Hipparcos data

Abstract

(shortened) From a kinematically unbiased subsample of the Hipparcos catalogue we have redetermined as a function of colour the kinematics of main-sequence stars. The stars' mean heliocentric velocity nicely follows the asymmetric drift relation, except for stars blueward of B-V=0.1. Extrapolating to zero dispersion yields for the velocity of the Sun w.r.t. the LSR in km/s: U_0=10.00+/-0.36 (radially inwards), V_0=5.23+/-0.62 (in direction of galactic rotation), and W_0=7.17+/-0.38 (vertically upwards). A plot of velocity dispersion vs. colour beautifully shows Parenago's discontinuity: the dispersion is constant for B-V>0.62 and decreases towards bluer colour. We determine the velocity-dispersion tensor sigma^2_ij as function of B-V. The mixed moments involving vertical motion are zero within the errors, while sigma^2_xy is non-zero at about (10km/s)^2 independent of colour. The resulting vertex deviations are about 20 deg for early-type stars and 10+/-4 deg for old-disc stars. The persistence of the vertex deviation to late-type stars implies that the Galactic potential is significantly non-axisymmetric at the solar radius. If spiral arms are responsible for this, they cannot be tightly wound. Except for stars bluer than B-V=0.1 the ratios of the principal velocity dispersions are 2.2 : 1.4 :1, while the absolute values increase with colour from sigma_1=20km/s at B-V=0.2 to sigma_1=38km/s at Parenago's discontinuity and beyond. These ratios imply significant heating of the disc by spiral structure and that R_0/R_d=3 to 3.5, where R_d is the scale length of the disc.Comment: 7 pages, LaTeX, mn.sty, 6 postscript figures, submitted to MNRA

Chemical abundances of 451 stars from the HARPS GTO planet search program

“…6, were computed with the trigonometric parallaxes and proper motions from the Hipparcos catalogue (ESA 1997), and by adopting the mean radial velocities obtained from the HARPS spectra (courtesy of the HARPS GTO team). The Galactic spacevelocity components were calculated using the procedure from Johnson & Soderblom (1987) and corrected for the solar motion relative to the local standard of rest (LSR) using (U , V , W ) = (+10.00, +5.25, +7.17) km s −1 from Dehnen & Binney (1998). This LSR correction was also used by Bensby et al (2003Bensby et al ( , 2005.…”

Accurate and homogeneous abundance patterns in solar-type stars of the solar neighbourhood: a chemo-chronological analysis

“…We developed a code that uses equations of Johnson & Soderblom (1987), parallaxes and proper motions both from the new reduction of the Hipparcos data, and radial velocities from Holmberg et al (2007), Torres et al (2006) for HD 114613, and Santos et al (2004) for HD 160691. For the Sun, the adopted values of U LSR , V LSR , and W LSR are 10.0, 5.3, and 7.2 km s −1 , respectively (Dehnen & Binney 1998). The mean orbital distance from the Galactic centre (R m ) and the orbital eccentricity (e) were also considered in our analysis (see Fig.…”

Asymmetric inelastic inert doublet dark matter from triplet scalar leptogenesis

“…The gaussian priors and the astrophysical likelihood are given in details in [87]. Only in the case of Maxwellian velocity distribution we do not vary the astrophysical observable in their allowed range but keep them fixed at their mean values, which arev 0 = 230 kms −1 [97,98], v esc = 544 kms −1 [99,100] andρ = 0.4 GeVcm −3 [101,102].…”