CCD UBV(RI)C photometry of twenty open clusters

Abstract

Fundamental astrophysical parameters have been derived for 20 open clusters (OCs) using CCD UBV(RI) C photometric data observed with the 84 cm telescope at the San Pedro Mártir National Astronomical Observatory, México.The interstellar reddenings, metallicities, distances, and ages have been compared to the literature values. Significant differences are usually due to the usage of diverse empirical calibrations and differing assumptions, such as concerning cluster metallicity, as well as distinct isochrones which correspond to differing element-abundance ratios, internal stellar physics, and photometric systems. Different interstellar reddenings, as well as varying reduction and cluster-membership techniques, are also responsible for these kinds of systematic differences and errors.The morphological ages, which are derived from the morphological indices (δV and δ1) in the CM diagrams, are in good agreement with the isochrone ages of 12 OCs, those with good red clump (RC) and red giant (RG) star candidates. No metal abundance gradient is detected for the range 6.82 ≤ R GC ≤ 15.37 kpc, nor any correlation between the cluster ages and metal abundances for these 20 OCs.Young, metal-poor OCs, observed here in the third Galactic quadrant, may be associated with stellar over-densities, such as that in Canis Major (Martin et al.) and the Monoceros Ring (Newberg et al.), or signatures of past accretion events, as discussed by Yong et al. and Carraro et al.

On the metallicity of open clusters

“…We note that there are also some other recent photometric approaches (e.g. Oliveira et al 2013;Oralhan et al 2015), but so far the overlap with our sample is too small for a proper comparison.…”

“…There is only one object in the defined older group (NGC 2360) that shows a large spread among the six compiled age determinations so that even a marginal interference with the young group might be possible. Although the most recent multicolour study of this object (Oralhan et al 2015) also pointed to an old age, we excluded this cluster from the group for the sake of reliability. The mean error of the age based on the compilation results in about 80 and 400 Myr for the young and old group, respectively, and there is no overlap between the groups even if taking the full error ranges into account.…”

The Galactic metallicity gradient shown by open clusters in the light of radial migration

“…M 𝜆 , 𝜂 𝜆 , 𝜁 𝜆 are standard magnitude, transformation coefficient and photometric zero point, respectively. More details about the data reduction can be found in the papers by Akkaya Oralhan et al (2010Oralhan et al ( , 2015Oralhan et al ( , 2019Oralhan et al ( , 2020, Schuster et al (2007), Tapia et al (2010).…”

CCD UBVRI photometry of the open cluster Berkeley 8

“…M λ , η λ , and ζ λ are standard magnitude, atmospheric extinction-corrected instrumental magnitude, transformation coefficient, and photometric zero point, respectively. The other details of data reduction can be found in the papers of Akkaya et al [16,17]. Air-mass range and exposure times in each band during the observations are given in rows 5-10 of Table 1.…”

“…Here the solar heavy metal content is adopted as Z ⊙ = +0.015. The isochrone is varied until a satisfactory fit to the data has been obtained through the observed main-sequence (MS), turn-off (TO), sub-giant (SG), and Red Giant/Red Clump (RG/RC) sequences on the CMDs, as we followed the papers of Akkaya et al [16,17] and Güneş et al [25].…”