Bibcode
Allende Prieto, C.; Kawata, Daisuke; Cropper, Mark
Referencia bibliográfica
Astronomy and Astrophysics, Volume 596, id.A98, 7 pp.
Advertised on:
12
2016
Revista
Número de citas
0
Número de citas referidas
0
Descripción
Aims: Previous studies have found that the Galactic rotation
velocity-metallicity (V-[Fe/H]) relations for the thin and thick disk
populations show negative and positive slopes, respectively. The first
Gaia data release includes the Tycho-Gaia Astrometric Solution (TGAS)
information, which we use to analyze the V-[Fe/H] relation for a
strictly selected sample with high enough astrometric accuracy. We aim
to present an explanation for the slopes of the V-[Fe/H] relationship.
Methods: We have identified a sample of stars with accurate Gaia
TGAS data and SDSS APOGEE [α/Fe] and [Fe/H] measurements. We
measured the V-[Fe/H] relation for thin and thick disk stars classified
on the basis of their [α/Fe] and [Fe/H] abundances.
Results: We find dV/ d [Fe/H] = -18 ± 2 km s-1
dex-1 for stars in the thin disk and dV/ d [Fe/H] = +23
± 10 km s-1 dex-1 for thick disk stars, and
thus we confirm the different signs for the slopes. The negative value
of dV/d[Fe/H] for thin disk stars is consistent with previous work, but
the combination of TGAS and APOGEE data provides higher precision, even
though systematic errors could exceed ±5 km s-1
dex-1. Our average measurement of dV/d[Fe/H] for local thick
disk stars shows a somewhat flatter slope than in previous studies, but
we confirm a significant spread and a dependence of the slope on the
[α/Fe] ratio of the stars. Using a simple N-body model, we
demonstrate that the observed trends for the thick and thin disk can be
explained by the measured radial metallicity gradients and the
correlation between orbital eccentricity and metallicity in the thick
disk. Conclusions: We conclude that the V-[Fe/H] relation for
thin disk stars is well determined from our TGAS-APOGEE sample, and a
direct consequence of the radial metallicity gradient and the
correlation between Galactic rotation and mean Galactocentric distance.
Stars formed farther away from the solar circle tend to be near their
orbital pericenter, showing larger velocities and on average lower
metallicities, while those closer to the Galactic center are usually
closer to their orbital apocenter, therefore moving slower and with
higher metallicities. The positive dV/d[Fe/H] for the thick disk sample
is likely connected to the correlation between orbital eccentricity and
metallicity for that population.