We derive astrophysical and structural parameters of the poorly studied open clusters NGC 6866, NGC 7062, and NGC 2360 based on filtered 2MASS (J, J − H) diagrams, and stellar radial density profiles. The field star decontamination technique is utilised for selecting high-probability cluster members. The E(B − V ) reddening values of the three clusters derived from 2MASS JHK s agree with those inferred from UBV and uvby −β photometries. We find that the core mass function slopes are flatter than the halo's for the three clusters. The large core and cluster radii of NGC 6866 and NGC 2360 indicate an expanded core, which may suggest the presence of stellar mass black-holes. NGC 2360 is located in the third quadrant (ℓ = 229• .80), where Giant Molecular Clouds are scarce that, together with its relatively large mass (∼ 1800 m ⊙ ), might explain its longevity (∼ 1.8 Gyr) in the Galaxy.

We investigate the dynamical evolution of 40 open clusters (OCs) by means of their astrophysical parameters derived from field-decontaminated 2MASS photometry. We find a bifurcation in the planes' core radius versus age and cluster radius versus age, in which part of the clusters appear to expand with time probably due to the presence of stellar black holes while others seem to shrink due to dynamical relaxation. Mass functions (MFs) are built for three-fourth of the sample (31 OCs), which are used to search for indications of mass segregation and external dynamical processes by means of relations between astrophysical, structural, and evolutionary parameters. We detect a flattening of MF slopes occurring at the evolutionary parameters core ≤ 32 and overall ≤ 30, respectively. Within the uncertainties involved, the overall MF slopes of 14 out of 31 OCs with m overall > 500 M ⊙ are consistent with Kroupa's initial mass function, implying little, or no dynamical evolution for these clusters. The remaining 17 OCs with MF slopes departing from that of Kroupa show mild/large-scale mass segregation due to dynamical evolution. KEYWORDS CCD 2 MASS photometry -open clusters and associations -stars1

Abstract:We study the metal abundances of F and G type stars in the Galactic disk and halo using the CanadaFrance-Hawaii Telescope Legacy Survey D4 field. For a sample of stars within 7 kpc of the Galactic plane, we derive mean abundance values of [Fe/H] = −0.77 ± 0.36 dex for the thick disk, and [Fe/H] = −1.42 ± 0.98 dex for the stellar halo, respectively. These metallicites are consistent with the metallicity estimates from the Sloan Digital Sky Survey Data Release 6. We do not find a vertical abundance gradient for the thick disk between 1 kpc and 4 kpc. However, stars within 1 kpc of the Galactic plane are saturated in our dataset, and therefore we cannot rule out the observed vertical metallicity gradient for the thick disk stars in the SDSS. Moreover, we find a negative trend in the halo metallicity with increasing distance from the Galactic plane. This trend could be due to a contribution from an increasing number of very metal poor stars that belong to the outer halo. However, systematic effects in photometric metallicities are largest for the most metal poor stars, and therefore these effects cannot be ruled out.