Dependence of kinematics on the age of stars in the solar neighborhood

Abstract

lar neighborhood. The variations of kinematic parameters with age are considered for a sample of 15 402 thin-disk O-F stars with accurate α, δ, µ, and π > 3 mas from the Hipparcos catalogue and radial velocities from the PCRV catalogue. The ages have been calculated from the positions of the stars on the Hertzsprung-Russell diagram relative to the isochrones from the Padova database by taking into account the extinction from the previously constructed 3D analytical model and extinction coefficient R V from the 3D map of its variations. Smooth, mutually reconciled variations of the velocity dispersions σ(U), σ(V ), σ(W ), solar motion components U ⊙ , V ⊙ , W ⊙ , Ogorodnikov-Milne model parameters, Oort constants, and vertex deviation l xy consistent with all of the extraneous results for which the stellar ages were determined have been found. The velocity dispersion variations are well fitted by power laws the deviations from which are explained by the influence of predominantly radial stellar streams: Sirius, Hyades, α Cet/Wolf 630, and Hercules. The accuracy of determining the solar motion relative to the local standard of rest is shown to be fundamentally limited due to these variations of stellar kinematics. The deviations of our results from those of Dehnen and Binney (1998), the Geneva-Copenhagen survey of dwarfs, and the Besancon model of the Galaxy are explained by the use of PCRV radial velocities with corrected systematic errors. *

The Surface Brightness-color Relations Based on Eclipsing Binary Stars: Toward Precision Better than 1% in Angular Diameter Predictions

“…R V can vary significantly, but mostly lies between 2.7 and 3.7 (e.g. Gontcharov 2012). When this is not accounted for, it shows as an additional intrinsic scatter in the SBC relation that amounts to about 0.02 mag in some individual cases.…”

The local standard of rest and the well in the velocity distribution

“…The kinematical LSR refers to the mean motion of a specified stellar population. As described in a number of recent papers (e.g., Gontcharov, 2012aGontcharov, & 2012bFrancis & Anderson, 2009a "FA09a"; Dehnen, 1998), kinematics is heavily dependent on stellar age, which in turn leads to dependency on stellar temperature (or colour).…”

Interstellar Extinction

“…Here iterations can be performed: reddening is calculated from a "dirty" sample and they are used to calculate de-reddened colors, contaminated stars are rejected, and the reddening is calculated using the "clear" sample. This approach has been used by Gontcharov (2012a). The characteristics of a large number of stars in each cell of space should be averaged.…”

“…In the Besançon model of the galaxy (Robin 2003), which was once popular but is now obsolete (Gontcharov 2012d), 28% of the mass was assigned to the interstellar medium in the galactic neighborhood of the Sun, 59%, to residual baryonic matter (stars, brown dwarfs, white dwarfs, neutron stars, and planets), and 13% to dark matter. In the new version of this model by Czekaj, et al (2014), right after Binney and Tremain (2008), the spatial mass density for the interstellar medium in the Suns vicinity is taken to be 0.05 (47%), for residual baryonic matter 0.043 − 0.049 (about 44%), and for dark matter, 0.01M ⊙ /pc 3 (9%).…”

“…This can be seen in 2015), have found the same behavior in the galaxy M82 (R V initially decreases with distance from the galactic center and then increases for many kpc). Gontcharov (2012aGontcharov ( , 2013bGontcharov ( , 2016 has analyzed the extinction law in spatial cones of height 25 kpc extending from the Sun to the galactic poles. This made use of photometric data on 9769 clump giants (in a radius of 8 • around the poles) and 1221 branch giants (in a radius of 20 • around the poles) from the Tycho-2, 2MASS, and WISE catalogs.…”