INVESTIGADORES
PIATTI Andres Eduardo
artículos
Título:
Washington photometry of open cluster giants: two moderately metal-poor anticentre clusters
Autor/es:
PARISI, M.C.; CLARIA OLMEDO, JUAN JOSÉ; PIATTI, ANDRÉS E.; GEISLER, DOUG
Revista:
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Referencias:
Año: 2005 vol. 363 p. 1247 - 1256
ISSN:
0035-8711
Resumen:
New photometric data in the Washington system are presented for red
giant candidates in NGC 1817 and 2251, two open clusters located towards
the Galactic anticentre direction. In the case of NGC 2251, the
Washington data are supplemented with new UBV and David Dunlap
Observatory (DDO) photoelectric photometry. Published radial velocities
are used to separate field stars from cluster giants. The photometric
data yield an effective temperature and metal abundance for each cluster
member. Five independent Washington abundance indices yield mean
metallicities of [Fe/H]= 0.25 +/- 0.04 for NGC 1817 and 2251,
respectively. From combined BV and DDO data, we also derive E(B-V) =
0.21 +/- 0.03 and [Fe/H]DDO=-0.14 +/- 0.05 for NGC 2251. Both
objects are then found to be on the metal-poor side of the distribution
of open clusters, their metallicities being compatible with the
existence of a radial abundance gradient in the disc. Using the WEBDA
Open Cluster data base and the available literature, we re-examined the
overall properties of a sample of 30 clusters located towards the
Galactic anticentre with the distances, ages and metallicities
available. This cluster sample presents no evidence of an abundance
gradient perpendicular to the Galactic plane, nor is an age-metallicity
relation found. However, a radial abundance gradient of -0.093 dex
kpc-1 is derived over a Galactocentric distance of 14 kpc, a
gradient which is in keeping with most recent determinations. This value
practically does not change when all clusters with basic parameters
known up to this date are considered.