INVESTIGADORES
PIATTI Andres Eduardo
artículos
Título:
Photometric and spectroscopic study of the southern open clusters Pismis 18, Pismis 19, NGC 6005 and NGC 6253
Autor/es:
PIATTI, ANDRÉS E.; CLARIA OLMEDO, JUAN JOSÉ; BICA, EDUARDO; GEISLER, DOUG; MINNITI, DANTE
Revista:
ASTRONOMICAL JOURNAL
Referencias:
Año: 1998 vol. 116 p. 801 - 812
ISSN:
0004-6256
Resumen:
CCD observations in the B, V, and I passbands have been used to generate
color-magnitude diagrams (CMDs) for the southern open cluster candidates
Pismis 18, Pismis 19, and NGC 6005, as well as for the old open cluster
NGC 6253. The sample consists of about 1550 stars reaching down to V ~
19 mag. From analysis of the CMDs, the physical reality of the three
cluster candidates is confirmed and their reddening, distance, and age
are derived, as well as those of NGC 6253. In addition, integrated
spectra for Pismis 18, Pismis 19, and NGC 6253 covering a range from
3500 to 9200 Å were obtained. The reddening, age, and metallicity
of these three clusters were derived from Balmer and Ca ii triplet
equivalent widths by comparing the observed spectra with those of
template clusters. The photometric and spectroscopic results allow us to
conclude that Pismis 18, Pismis 19, and NGC 6005 are intermediate-age (t
~ 1 Gyr), genuine open clusters, while NGC 6253 has an age t ~ 5 Gyr.
All these clusters are located approximately toward the Galactic center,
between 1.5 and 2.7 kpc from the Sun. Their metallicities range over
values that are typical of moderately metal-poor to moderately
metal-rich open clusters.