CCD BV survey of 42 open clusters

Astronomy and Astrophysics (Impact Factor: 4.48). 04/2007; DOI: 10.1051/0004-6361:20066588
Source: arXiv

ABSTRACT We present results of a photometric survey whose aim was to derive structural and astrophysical parameters for 42 open clusters. While our sample is definitively not representative of the total open cluster sample in the Galaxy, it does cover a wide range of cluster parameters and is uniform enough to allow for simple statistical considerations. BV wide-field CCD photometry was obtained for open clusters for which photometric, structural, and dynamical evolution parameters were determined. The limiting and core radii were determined by analyzing radial density profiles. The ages, reddenings, and distances were obtained from the solar metallicity isochrone fitting. The mass function was used to study the dynamical state of the systems, mass segregation effect and to estimate the total mass and number of cluster members. This study reports on the first determination of basic parameters for 11 out of 42 observed open clusters. The angular sizes for the majority of the observed clusters appear to be several times larger than the catalogue data indicate. The core and limiting cluster radii are correlated and the latter parameter is 3.2 times larger on average. The limiting radius increases with the cluster's mass, and both the limiting and core radii decrease in the course of dynamical evolution. For dynamically not advanced clusters, the mass function slope is similar to the universal IMF slope. For more evolved systems, the effect of evaporation of low-mass members is clearly visible. The initial mass segregation is present in all the observed young clusters, whereas the dynamical mass segregation appears in clusters older than about log(age)=8. Low-mass stars are deficient in the cores of clusters older than log(age)=8.5 and not younger than one relaxation time. Comment: 13 pages, 8 figures

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Context: We investigate the nature of a sample of star cluster candidates detected as stellar overdensities towards the Galactic anticentre. Aims: Taken from the catalogue of Froebrich, Scholz, and Raftery (FSR), the sample contains 28 star cluster candidates located within |Δℓ|=20° of the anticentre. These are all the candidates in that sector classified by FSR with a high probability of being star clusters. Our main goals are to determine the fraction of such candidates that are unknown star clusters, to derive their astrophysical parameters, and to investigate the relationship of cluster parameters with position in the Galaxy. Methods: Properties of the star cluster candidates are investigated with field-star decontaminated 2MASS colour-magnitude diagrams and stellar radial density profiles. Results: All candidates present significant excesses in the radial density profiles, consistent with the method from which they were originally selected. Of the 28 candidates, 7 are previously known open clusters, 2 have been recently identified, and 6 are new ones with ages from 30 Myr to 1 Gyr. Among the remaining 13 candidates, 6 are uncertain cases that require deeper observations, while 7 appear to be important field fluctuations. The structure of part of the newly identified open clusters appears to be affected by interaction with giant molecular clouds in the Local and Perseus arms. Conclusions: When photometric and radial distribution properties are considered together, an important fraction of the stellar overdensities with a fluctuation level ⪆3σ are shown to be star clusters. Thus, catalogues of star cluster candidates, coupled to the present kind of study, are an important source for identifying unknown open clusters. Such efforts affect the understanding of the star-formation rate, cluster dynamical evolution, and Galactic structure, among others.
    Astronomy and Astrophysics 07/2008; 485(1):81-93. · 4.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have carried out high-precision B- and V-band time-series CCD photometry to investigate the physical nature of an oscillating EA-type binary system in the intermediate-age open cluster NGC 2126. Analysis of the light variability for about 500 stars in this field has led to the discovery of three new variables, two pulsating stars and one EA-type eclipsing binary. One of the former, GSC3382-0957, a probable cluster member, is shown to have both p- and g-mode pulsations. A frequency analysis reveals two confident pulsating modes at f 1 = 14.835 c/d and f 2 = 1.812 c/d from both the B- and V-band data. In the color-magnitude diagram, the star is located at the lower edge of the δ Scuti instability strip, where the δ Sct and γ Dor stars overlap. It is suggested that this is a probable hybrid γ Dor-δ Sct star.
    The Astronomical Journal 10/2012; 144(5):141. · 4.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The near infrared range has opened a new window to study stellar populations in the Galaxy, in the Local Groud and beyond. Despite the large and growing use of these data, insufficient efforts have been made in the direction to calibrate stellar physical parameters such as age, reddening and distance. This can also be achieved using near infrared and optical data together. Furthermore, the huge amounts of photometric data available now and in the incoming years, demand the development of automated and statistical isochrone fittings to cope with such data. With this in mind, we analyse 2MASS data in order to determine physical parameters for a sample of 9 open clusters. As a first step, we determined the age, reddening and distance values for each cluster applying the classical isochrone fitting (by eye). Subsequently, we employed an automated procedure which compares synthetic colour-magnitude diagrams to observed ones, making use of the likelihood statistics to find the best solution. We also carried out structural analyses of the clusters using stellar radial density profiles. Both classical and statistical isochrone fittings revealed that there can be disagreement between physical parameters obtained from near infrared data analysis and the literature corresponding ones, most based on optical and UV data. Concerning the observed cluster structures, they were studied for the first time. We found evidence of various dynamical stages in the sample.
    New Astronomy 07/2012; 17(5):488–497. · 1.24 Impact Factor

Full-text (2 Sources)

Available from
May 22, 2014