The relatively young, metal-poor and distant open cluster NGC 2324

We have obtained CCD photometry in the Johnson V, Kron-Cousins I and CT1 Washington systems for NGC 2324, a rich open cluster located ∼35° from the Galactic anticentre direction. We measured V magnitudes and V - I colours for 2865 stars and T1 magnitudes and C - T 1 colours for 1815 stars in an area...

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Detalles Bibliográficos
Autores principales: Piatti, A.E., Clariá, J.J., Ahumada, A.V.
Formato: JOUR
Materias:
Galaxy: general
Galaxy: open clusters and associations: individual: NGC 2324
Techniques: photometric
Astrophysics
Charge coupled devices
Cosmic rays
Galaxies
Light absorption
Photometry
Galactic disc
Isochrone fitting procedures
Open clusters and association
Astronomy
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00046361_v418_n3_p979_Piatti
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
Descripción
Sumario:We have obtained CCD photometry in the Johnson V, Kron-Cousins I and CT1 Washington systems for NGC 2324, a rich open cluster located ∼35° from the Galactic anticentre direction. We measured V magnitudes and V - I colours for 2865 stars and T1 magnitudes and C - T 1 colours for 1815 stars in an area of 13′.6 × 13′.6. The comparison of the cluster colour-magnitude diagrams with isochrones of the Geneva group yield E(V - 1) = 0.33 ± 0.07 and V - Mv = 13.70 ± 0.15 for log t = 8.65 (t = 440 Myr) and Z = 0.008 ([Fe/H] = -0.40), and E(C - T1) = 0.40 ± 0.10 and T 1 - MT1 = 13.65 ± 0.15 for the same age and metallicity level. The resulting E(V - I) reddening value implies E(B - V) = 0.25 ± 0.05 and a distance from the Sun of (3.8 ± 0.5) kpc. Star counts carried out within and outside the cluster region allowed us to estimate the cluster angular radius as 5′.3 ± 0′.3 (5.9 pc). When using the E(B - V) reddening value here derived and the original Washington photometric data of Geisler et al. (1991) for the stars confirmed as red cluster giants from Coravel radial velocities, we found [Fe/H] = -0.31 ± 0.04, which is in good agreement with the best fits of isochrones. Therefore, NGC 2324 is found to be a relatively young, metal-poor and distant open cluster located beyond the Perseus spiral arm. A comparison of NGC 2324 with 10 well-known open clusters of nearly the same age shows that the cluster metal abundance and its position in the Galaxy are consistent with the existence of a radial abundance gradient of -0.07 dex kpc-1 in the Galactic disc.

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