Homogeneous photometry and star counts in the field of 9 Galactic star clusters

Seleznev, A. F.; Carraro, G.; Costa, E.; Локтин, А. В.

doi:10.1016/j.newast.2009.05.011

Cited by 17 publications

(30 citation statements)

References 38 publications

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“…We adopt the age that they derived using PARSEC isochrones, 1.66 Gyr, which is similar to the age of 1.5 Gyr obtained by Seleznev et al (2010). At that time, only 13 giants had been observed and analyzed.…”

Section: Trumpler 20mentioning

confidence: 92%

TheGaia-ESO Survey: Sodium and aluminium abundances in giants and dwarfs

Smiljanić

Romano

Bragaglia

et al. 2016

A&A

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Context. Stellar evolution models predict that internal mixing should cause some sodium overabundance at the surface of red giants more massive than ∼1.5-2.0 M . The surface aluminium abundance should not be affected. Nevertheless, observational results disagree about the presence and/or the degree of Na and Al overabundances. In addition, Galactic chemical evolution models adopting different stellar yields lead to very different predictions for the behavior of [Na/Fe] and [Al/Fe] versus [Fe/H]. Overall, the observed trends of these abundances with metallicity are not well reproduced. Aims. We readdress both issues, using new Na and Al abundances determined within the Gaia-ESO Survey. Our aim is to obtain better observational constraints on the behavior of these elements using two samples: i) more than 600 dwarfs of the solar neighborhood and of open clusters and ii) low-and intermediate-mass clump giants in six open clusters. Methods. Abundances were determined using high-resolution UVES spectra. The individual Na abundances were corrected for nonlocal thermodynamic equilibrium effects. For the Al abundances, the order of magnitude of the corrections was estimated for a few representative cases. For giants, the abundance trends with stellar mass are compared to stellar evolution models. For dwarfs, the abundance trends with metallicity and age are compared to detailed chemical evolution models. Results. Abundances of Na in stars with mass below ∼2.0 M , and of Al in stars below ∼3.0 M , seem to be unaffected by internal mixing processes. For more massive stars, the Na overabundance increases with stellar mass. This trend agrees well with predictions of stellar evolutionary models. For Al, our only cluster with giants more massive than 3.0 M , NGC 6705, is Al enriched. However, this might be related to the environment where the cluster was formed. Chemical evolution models that well fit the observed [Na/Fe] vs. [Fe/H] trend in solar neighborhood dwarfs cannot simultaneously explain the run of [Al/Fe] with [Fe/H], and vice versa. The comparison with stellar ages is hampered by severe uncertainties. Indeed, reliable age estimates are available for only a half of the stars of the sample. We conclude that Al is underproduced by the models, except for stellar ages younger than about 7 Gyr. In addition, some significant source of late Na production seems to be missing in the models. Either current Na and Al yields are affected by large uncertainties, and/or some important Galactic source(s) of these elements has as yet not been taken into account.

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Section: Trumpler 20mentioning

confidence: 92%

TheGaia-ESO Survey: Sodium and aluminium abundances in giants and dwarfs

Smiljanić

Romano

Bragaglia

et al. 2016

A&A

Self Cite

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“…To determine the coordinates of the cluster centre, and to study the cluster 2-dimensional (2D) structure, we derived surface density maps (2D density distributions) by using a kernel estimator (see, for example, Seleznev et al 2010, andSeleznev 2012, and the detailed description of this method in Silverman 1986). Density maps were derived at varying the limiting magnitude.…”

Section: Surface Density Maps and Cluster Centermentioning

confidence: 99%

On the mass of the Galactic star cluster NGC 4337

Seleznev

Carraro

Capuzzo-Dolcetta

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Only a small number of galactic open clusters survives for longer than few hundred million years. Longer lifetimes are routinely explained in term of larger initial masses, particularly quiet orbits, and off-plane birth-places. We derive in this work the actual mass of NGC 4337, one of the few open clusters in the Milky Way inner disk that managed to survive for about 1.5 Gyr. We derive its mass in two different ways. First, we exploit an unpublished photometric data set in the UBVI passbands to estimate -using star counts-the cluster luminosity profile, and luminosity and mass function, and hence its actual mass both from the luminosity profile and from the mass function.This data-set is also used to infer crucial cluster parameters, as the cluster half-mass radius and distance. Second, we make use of a large survey of cluster star radial velocities to derive dynamical estimates for the cluster mass. Under the assumption of virial equilibrium and neglecting the external gravitational field leads to values for the mass significantly larger than those obtained by mean of observed density distribution or with the mass function but still marginally compatible with the inferred values of the invisible mass in form of both low mass stars or remnants of high mass stars in the cluster. Finally, we derive the cluster initial mass by computing the mass loss experienced by the cluster during its lifetime, and adopting the various estimates of the actual mass.

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“…Surface density maps (SDMs) were constructed for all fields under investigation to determine the reality and size of the cluster. Examples of the application of this technique can be found in Prisinzano et al (2001), Pancino et al (2003) and Seleznev et al (2010) We refer the reader to these papers for further details.…”

Section: Star Counts Clusters’ Reality and Sizementioning

confidence: 99%

“…The technique we used is based on the analysis of the colour–colour and colour–magnitude diagrams of groups of stars properly selected after having performed star counts and defined clusters’ reality and size (see Seleznev et al 2010 for details).…”

Section: Introductionmentioning

confidence: 99%

UBVI CCD photometry and star counts in nine inner disc Galactic star clusters★

Carraro

Seleznev

2011

Monthly Notices of the Royal Astronomical Society

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We present and discuss new CCD-based photometric material in the UBVI passbands for nine Galactic star clusters located inside the solar ring, for which no CCD data are currently available. These star clusters are IC 2714, NGC 4052, ESO 131SC09, NGC 5284, NGC 5316, NGC 5715, VdB-Hagen 164, NGC 6268 and Czernik 38. The main aim of this study is to establish the nature of real clusters or random field star enhancements and, when real, estimate their fundamental parameters. To this aim, we first perform star counts by combining our optical photometry with 2MASS, and derive cluster sizes and radial density profiles. The fundamental parameters such as age, reddening and distance are then inferred from the analysis of the star distribution in the colour-colour and colour-magnitude diagrams of only the spatially selected likely members. Our analysis shows that ESO 131SC09, NGC 5284 and VdB-Hagen 164 are most probably not clusters, but random enhancements of a few bright stars along the line of sight, with properties much similar to so-called open cluster remnants. The remaining clusters are physical groups and are all younger than about 1 Gyr. We use the newly derived set of parameters, in particular distance and reddening, to investigate their position in the Galaxy in the context of the spiral structure of the Milky Way. We find that the youngest clusters (IC 2714, NGC 5316 and NGC 6268) are located close to or inside the Carina-Sagittarius arm, and are therefore bona fide spiral structure tracers. On the other hand, the oldest clusters (Czernik 38, NGC 4052 and NGC 5715) are floating in the interarm space between the Carina-Sagittarius and the more distant Scutum-Crux arm. Interestingly enough, the oldest clusters of this sample - Czernik 38 and NGC 5715 - are among the few known open clusters to be older or as old as the Hyades in the inner Galactic disc, where star clusters are not expected to survive for a long time, because of the strong tidal field and the higher probability of close encounter

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Homogeneous photometry and star counts in the field of 9 Galactic star clusters

Cited by 17 publications

References 38 publications

TheGaia-ESO Survey: Sodium and aluminium abundances in giants and dwarfs

TheGaia-ESO Survey: Sodium and aluminium abundances in giants and dwarfs

On the mass of the Galactic star cluster NGC 4337

UBVI CCD photometry and star counts in nine inner disc Galactic star clusters★

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