Analysis of peculiarities of the stellar velocity field in the solar neighborhood

Abstract

Based on a new version of the Hipparcos catalogue and an updated Geneva-Copenhagen survey of F and G dwarfs, we analyze the space velocity field of ≈17000 single stars in the solar neighborhood. The main known clumps, streams, and branches (Pleiades, Hyades, Sirius, Coma Berenices, Hercules, Wolf 630-αCeti, and Arcturus) have been identified using various approaches. The evolution of the space velocity field for F and G dwarfs has been traced as a function of the stellar age. We have managed to confirm the existence of the recently discovered KFR08 stream. We have found 19 Hipparcos stars, candidates for membership in the KFR08 stream, and obtained an isochrone age estimate for the stream, 13 Gyr. The mean stellar ages of the Wolf 630-αCeti and Hercules streams are shown to be comparable, 4-6 Gyr. No significant differences in the metallicities of stars belonging to these streams have been found. This is an argument for the hypothesis that these streams owe their origin to a common mechanism.

The nature of the KFR08 stellar stream

“…The probability that the star HIP 74033 belongs to the KFR08 stream is 0.65 according to Bobylev et al (2010). Since the location of this star in velocity space is also close to the Arcturus stream, we are not surprised that it was selected as a potential member of the Arcturus stream in Arifyanto & Fuchs (2006).…”

“…Stellar sample Bobylev et al (2010) found nineteen stars that probably are members of the KFR08 stream. Seventeen of those are high-probability members.…”

“…This spectrum has a wide wavelength range (350-920 nm), high resolution (R ∼ 48 000), and good S/N (∼75 per rebined pixel). The exoplanet survey carried out with HARPS on nearby stars with high-resolution spectroscopy (R ∼ 120 000, Mayor et al 2003) includes spectra for two of the stars identified as possible stream members by Bobylev et al (2010). Both spectra have a mean S/N higher than 50 per rebinned pixel.…”

“…"-" indicates the 1σ lower (or upper) age could not be determined because a very young (or old) star is outside of the isochrones limitations. (a) Means that the space velocities of the stars are taken from Bobylev et al (2010).…”

“…An over-density region that corresponds to the location of the KFR08 stream within parameter distributions was found. Based on a new version of the Hipparcos catalogue (van Leeuwen 2007) and updated Geneva-Copenhagen Survey (Holmberg et al 2007) of F and G dwarfs, Bobylev et al (2010) identified statistically significant signals of the main inhomogeneities in the velocity distribution using the wavelet transform technique. They found 19 possible stream members around (-160, 225) km s −1 in the V and (U 2 + 2V 2 ) 1/2 plane.…”