The Geneva-Copenhagen survey of the solar neighbourhood

Abstract

Context. Ages, chemical compositions, velocity vectors, and Galactic orbits for stars in the solar neighbourhood are fundamental test data for models of Galactic evolution. The Geneva-Copenhagen Survey of the Solar Neighbourhood (Nordström et al. 2004; GCS), a magnitude-complete, kinematically unbiased sample of 16 682 nearby F and G dwarfs, is the largest available sample with complete data for stars with ages spanning that of the disk. Aims. We aim to improve the accuracy of the GCS data by implementing the recent revision of the Hipparcos parallaxes. Methods. The new parallaxes yield improved astrometric distances for 12 506 stars in the GCS. We also use the parallaxes to verify the distance calibration for uvbyβ photometry by Holmberg et al. (2007, A&A, 475, 519; GCS II). We add new selection criteria to exclude evolved cool stars giving unreliable results and derive distances for 3580 stars with large parallax errors or not observed by Hipparcos. We also check the GCS II scales of T eff and [Fe/H] and find no need for change. Results. Introducing the new distances, we recompute M V for 16 086 stars, and U, V, W, and Galactic orbital parameters for the 13 520 stars that also have radial-velocity measurements. We also recompute stellar ages from the Padova stellar evolution models used in GCS I-II, using the new values of M V , and compare them with ages from the Yale-Yonsei and Victoria-Regina models. Finally, we compare the observed age-velocity relation in W with three simulated disk heating scenarios to show the potential of the data. Conclusions. With these revisions, the basic data for the GCS stars should now be as reliable as is possible with existing techniques. Further improvement must await consolidation of the T eff scale from angular diameters and fluxes, and the Gaia trigonometric parallaxes. We discuss the conditions for improving computed stellar ages from new input data, and for distinguishing different disk heating scenarios from data sets of the size and precision of the GCS.

Radial migration of the Sun in the Milky Way: a statistical study

“…Past studies of the age-metallicity relation in the solar neighbourhood suggested that the Sun is more metal rich by typically 0.2 dex than most stars at its age and Galactocentric orbit (Edvardsson et al 1993;Holmberg et al 2009). Hence, from the relationship between metallicity and Galactocentric radius, it is natural to deduce that the Sun might have migrated from the inner regions of the disk to its current position in the Galaxy (Wielen 1996;Minchev et al 2013).…”

“…Wielen (1996) argued that the Sun was born at a Galactocentric distance of 6.6±0.9 kpc; roughly 2 kpc nearer to the Galactic centre. He based his conclusions on the observation that the Sun is more metal rich by 0.2 dex with respect to most stars of the same age and Galactocentric position (Holmberg et al 2009) and the presence of a radial metallicity gradient in the Milky Way. Other studies also support the idea that the Sun has migrated from its birth place.…”

Separation of stellar populations by an evolving bar: implications for the bulge of the Milky Way

“…In reality, discs are composed of multiple populations of different ages with different dispersions; even in the Solar neighbourhood, the radial, tangential and vertical velocity dispersions are all a function of age (e.g. Wielen 1977;Nordström et al 2004;Holmberg et al 2009;Aumer & Binney 2009;Casagrande et al 2011). …”

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

“…The mean orbital distance from the Galactic centre (R m ) and the orbital eccentricity (e) were also considered in our analysis (see Fig. 5), where e = (R a − R p )/(R a + R p ) and R m = (R a + R p )/2 were computed using the perigalactic (R p ) and the apogalactic (R a ) orbital distances from the Geneva-Copenhagen survey (Holmberg et al 2009). For the Sun, the adopted values are e = 0.06 and R m = 8 kpc.…”