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

¹ Instituto de Astronomía y Física del Espacio, CC 67, Suc. 28, 1428 Buenos Aires, Argentina
² Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, 5000 Córdoba, Argentina e-mail: claria@mail.oac.uncor.edu;andrea@mail.oac.uncor.edu

Corresponding author: A. E. Piatti, andres@iafe.uba.ar

Received: 12 January 2004
Accepted: 21 January 2004

Abstract

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  colours for 2865 stars and T₁ magnitudes and  colours for 1815 stars in an area of 136  136. The comparison of the cluster colour–magnitude diagrams with isochrones of the Geneva group yield  = 0.33 ± 0.07 and  = 13.70 ± 0.15 for log t = 8.65 (t = 440 Myr) and Z = 0.008 ([Fe/H] = -0.40), and  = 0.40 ± 0.10 and  = 13.65 ± 0.15 for the same age and metallicity level. The resulting reddening value implies  = 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 53 ± 03 (5.9 pc). When using the reddening value here derived and the original Washington photometric data of [CITE] 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.