The Geneva-Copenhagen survey of the Solar neighbourhood II

Abstract

Context. Ages, metallicities, space velocities, and Galactic orbits of stars in the Solar neighbourhood are fundamental observational constraints on models of galactic disk evolution. Understanding and minimising systematic errors and sample selection biases in the data is crucial for their interpretation. Aims. We aim to consolidate the calibrations of uvbyβ photometry into T eff , [Fe/H], distance, and age for F and G stars and rediscuss the results of the Geneva-Copenhagen Survey (Nordström et al. 2004;GCS) in terms of the evolution of the disk. Methods. We use recent V − K photometry, angular diameters, high-resolution spectroscopy, Hipparcos parallaxes, and extensive numerical simulations to re-examine and verify the temperature, metallicity, distance, and reddening calibrations for the uvbyβ system. We also highlight the selection effects inherent in the apparent-magnitude limited GCS sample. Results. We substantially improve the T eff and [Fe/H] calibrations for early F stars, where spectroscopic temperatures have large systematic errors. A slight offset of the GCS photometry and the non-standard helium abundance of the Hyades invalidate its use for checking metallicity or age scales; however, the distances, reddenings, metallicities, and age scale for GCS field stars require minor corrections only. Our recomputed ages are in excellent agreement with the independent determinations by Takeda et al. (2007), indicating that isochrone ages can now be reliably determined. Conclusions. The revised G-dwarf metallicity distribution remains incompatible with closed-box models, and the age-metallicity relation for the thin disk remains almost flat, with large and real scatter at all ages (σ intrinsic = 0.20 dex). Dynamical heating of the thin disk continues throughout its life; specific in-plane dynamical effects dominate the evolution of the U and V velocities, while the W velocities remain random at all ages. When assigning thick and thin-disk membership for stars from kinematic criteria, parameters for the oldest stars should be used to characterise the thin disk.

An Introduction to Gas Accretion onto Galaxies

“…Closed box galaxy evolution models produce a wider distribution of stellar metallicities than is observed and this has traditionally been referred to as the G-dwarf problem. This evidence for accretion is strongest in the local universe where the metallicity of individual long-lived stars can be measured (Holmberg et al, 2007;Kirby et al, 2013;Grillmair et al, 1996), but it is also consistent with the metallicities derived from the integrated stellar light observations of galaxies (e.g. Henry & Worhey et al, 1999;Bressan et al, 1994;Stott et al, 2014;Gallazzi et al, 2005).…”

Origin of the wide-orbit circumbinary giant planet HD 106906

“…Then, we searched the SIMBAD/CDS databases (Wenger et al 2000) for radial velocity information using the data mining tools available on the site. The radial velocities that we use in this work come from Wilson (1953), Duflot et al (1995), Barbier-Brossat & Figon (2000), Torres et al (2006), Gontcharov (2006), Holmberg et al (2007), Mermilliod et al (2009), Chen et al (2011), Song et al (2012, Kordopatis et al (2013) and Desidera et al (2015). We found radial velocity for 184 stars of our sample.…”

Chromospheric activities and kinematics for solar type dwarfs and subgiants: analysis of the activity distribution and the AVR

“…of kinematic data and revealed the kinematic space-component distributions to a higher significance than any that came before (Nordström et al 2004;Holmberg et al 2007).…”

“…We also employ a correction to the local standard of rest given in Dehnen (1998). Figure 14 shows a comparison between the space velocities U, V, and W obtained in this work and the values published in Holmberg et al (2007) for 231 stars that are common to our sample. We can see that the velocities are in good agreement with only a few outliers.…”

“…The upper left panel shows 11.4 ± 1.7 -58.1 ± 1.2 -6.9 ± 1.3 -33.8 ± 1.3 HIP112935 0.480 5.16 0.111 0.142 ± 0.004 -5.09 3.9 11.4 ± 1.7 -58.1 ± 1.2 -6.9 ± 1.3 -33.8 ± the kinematic U component binned into steps of 10 km s −1 . The distribution generally follows a broad Gaussian profile or a sinc function, but given that this is a biased sample in general, the overall shape does not fully follow the true distribution of dwarf and subgiant stars in the solar neighbourhood drawn from a kinematically unbiased sample (see Holmberg et al 2007). However, we see that it does broadly conform to a distribution that has been drawn from a Schwartzchild distribution function (SDF).…”