NGC 2180: A disrupting open cluster?

Bonatto, Charles Jose; Bica, E.; Pavani, Daniela Borges

doi:10.1051/0004-6361:20040453

Cited by 22 publications

(44 citation statements)

References 34 publications

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“…This effect was shown for M 67 in Bica & Bonatto (2005a). The binary peak is also present in NGC 3680 (Bonatto et al 2004a). that coincides with the range in PM covered by the single and binary-star peaks of the MS distribution (panel a).…”

Section: Ucac2 Proper Motionsmentioning

confidence: 54%

Detection of K_s-excess stars in the 14 Myr open cluster NGC 4755

Bonatto

Bica

Ortolani

et al. 2006

A&A

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Aims. We derive the structure, distribution of MS and PMS stars and dynamical state of the young open cluster NGC 4755. We explore the possibility that, at the cluster age, some MS and PMS stars still present infrared excesses related to dust envelopes and proto-planetary discs. Methods. J, H and K s 2MASS photometry is used to build CMD and colour-colour diagrams, radial density profiles, luminosity and mass functions. Field-star decontamination is applied to uncover the cluster's intrinsic CMD morphology and detect candidate PMS stars. Proper motions from UCAC2 are used to determine cluster membership. Results. The radial density profile follows King's law with a core radius R core = 0.7 ± 0.1 pc and a limiting radius R lim = 6.9 ± 0.1 pc. The cluster age derived from Padova isochrones is 14 ± 2 Myr. Field-star decontamination reveals a low-MS limit at ≈1.4 M . The core MF (χ = 0.94 ± 0.16) is flatter than the halo's (χ = 1.58 ± 0.11). NGC 4755 contains ∼285 candidate PMS stars of age ∼1−15 Myr, and a few evolved stars. The mass locked up in PMS, MS and evolved stars amounts to ∼1150 M . Proper motions show that K s -excess MS and PMS stars are cluster members. K s -excess fractions in PMS and MS stars are 5.4 ± 2.1% and 3.9 ± 1.5% respectively, consistent with the cluster age. The core is deficient in PMS stars, as compared with MS ones. NGC 4755 hosts binaries in the halo but they are scarce in the core. Conclusions. Compared to open clusters in different dynamical states studied with similar methods, NGC 4755 fits relations involving structural and dynamical parameters in the expected locus for its age and mass. On the other hand, the flatter core MF probably originates from primordial processes related to parent molecular cloud fragmentation and mass segregation over ∼14 Myr. Star formation in NGC 4755 began ≈14 Myr ago and proceeded for about the same length of time. Detection of K s -excess emission in member MS stars suggests that some circumstellar dust discs survived for ∼10 7 yr, occurring both in some MS and PMS stars for the age and spread observed in NGC 4755.

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Section: Ucac2 Proper Motionsmentioning

confidence: 54%

Detection of K_s-excess stars in the 14 Myr open cluster NGC 4755

Bonatto

Bica

Ortolani

et al. 2006

A&A

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“…in NGC 3680 (Anthony- Twarog et al 1991;Bonatto et al 2004b) and M 67 , in which the presence of a core depleted of low-MS stars and a halo rich in low-mass stars have been confirmed with 2MASS photometry.…”

Section: Introductionmentioning

confidence: 77%

Spatial dependence of 2MASS luminosity and mass functions in the old open cluster NGC 188

Bonatto¹,

Bica²,

Santos

2005

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Abstract. Luminosity and mass functions in the old open cluster NGC 188 are analysed by means of J and H 2MASS photometry, which provides uniformity and spatial coverage for a proper background subtraction. With an age of about 6-8 Gyr, NGC 188 is expected to be suffering the effects of advanced dynamical evolution. Indeed, previous works in optical bands have suggested the presence of mass segregation. Within the uncertainties, the observed projected radial density profile of NGC 188 departs from the two-parameter King model in two inner regions, which reflects the non-virialized dynamical state and possibly, some degree of non-sphericity in the spatial shape of this old open cluster. Fits with two and three-parameter King models to the radial distribution of stars resulted in a core radius R core = 1.3 ± 0.1 pc and a tidal radius R tidal = 21 ± 4 pc, about twice as large as the visual limiting radius. The concentration parameter c = 1.2 ± 0.1 of NGC 188 makes this open cluster structurally comparable to the loose globular clusters. The present 2MASS analysis resulted in significant slope variations with distance in the mass function φ(m) ∝ m −(1+χ) , being flat in the central parts (χ = 0.6 ± 0.7) and steep in the cluster outskirts (χ = 7.2 ± 0.6). The overall mass function has a slope χ = 1.9 ± 0.7, slightly steeper than a standard Salpeter mass function. In this context, NGC 188 is similar to the 3.2 Gyr, dynamically evolved open cluster M 67. Solar metallicity Padova isochrone fits to the nearinfrared colour-magnitude diagram of NGC 188 resulted in an age of 7.0 ± 1.0 Gyr. The best fit, obtained with the 7.1 Gyr isochrone, produced a distance modulus (m − M) 0 = 11.1 ± 0.1, E(B − V) = 0.0, and a distance to the Sun d = 1.66 ± 0.08 kpc. The observed stellar mass (in the range 0.98 M −1.08 M ) in NGC 188 is m obs = 380 ± 12 M . A simple extrapolation of the observed overall mass function to stars with 0.08 M resulted in a total present mass of m tot ∼ (1.8 ± 0.7) × 10 4 M . On the other hand, for a more realistic initial mass function which flattens in the low-mass range, the total mass in NGC 188 drops to m tot ∼ (3.8 ± 1.6) × 10 3 M . Since mass-loss processes such as evaporation and tidal stripping have been occurring in this old open cluster for about 7 Gyr, the primordial mass in NGC 188 must have been significantly larger than ∼4 × 10 3 M . We also examined the consequences of the presence of unresolved binaries and concluded that, even if dominant in the CMD, binaries alone are not responsible for the flat central mass function, which supports the mass-segregation scenario.

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“…The RDPs produced with the WEBDA coordinates presented in general a dip in the innermost bin. For these we searched for new coordinates that maximise the star-counts The statistical significance of astrophysical parameters depends directly on the quality and depth of the photometry (Bonatto et al 2004b. As a photometric quality constraint, 2MASS extractions were restricted to stars with magnitudes (i) brighter than those of the 99.9% Point Source Catalogue completeness limit in the cluster direction; and (ii) with errors in J, H, and K s smaller than 0.1 mag.…”

Section: The 2mass Photometrymentioning

confidence: 99%

“…This tool was previously applied to the structural analysis of the OCs M 67 (Bonatto & Bica 2003), NGC 3680 (Bonatto et al 2004b), NGC 188 , NGC 6611 ), NGC 4755 (Bonatto et al 2006c), M 52 and NGC 3690 (Bonatto & Bica 2006) and the faint OCs BH 63, Lyngå 2, Lyngå 12 and King 20 ). The filters were defined based on the distribution of the decontaminated star sequences in the CMDs of open clusters.…”

Section: Structural Parametersmentioning

confidence: 99%

Astrophysical parameters of 14 open clusters projected close to the Galactic plane

Camargo¹,

Bonatto²,

Bica³

2009

A&A

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Aims. Astrophysical parameters (age, reddening, distance, core and cluster radii) of 14 open clusters (OCs) projected close to the Galactic plane are derived with 2MASS photometry. The OCs are Be 63, Be 84, Cz 6, Cz 7, Cz 12, Ru 141, Ru 144, Ru 172, FSR 101, FSR 1430, FSR 1471, FSR 162, FSR 178, and FSR 198. The OCs Be 63, Be 84, Ru 141, Ru 144, and Ru 172 are studied in more detail than in previous works, while the others have astrophysical parameters derived for the first time. Methods. We analyse the colour−magnitude diagrams (CMDs) and stellar radial density profiles (RDPs) built after field-star decontamination and colour-magnitude filtered photometry. Field-star decontamination is applied to uncover the cluster's intrinsic CMD morphology, and colour−magnitude filters are used to isolate stars with a high probability of being cluster members in view of structural analyses.Results. The open clusters of the sample are located at d = 1.6−7.1 kpc from the Sun and at Galactocentric distances 5.5−11.8 kpc, with age in the range 10 Myr to 1.5 Gyr and reddening E(B−V) in the range 0.19−2.56 mag. The core and cluster radii are in the range 0.27−1.88 pc and 2.2−11.27 pc, respectively. Cz 6 and FSR 198 are the youngest OCs of this sample, with a population of pre-main sequence (PMS) stars, while FSR 178 is the oldest cluster.

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NGC 2180: A disrupting open cluster?

Cited by 22 publications

References 34 publications

Detection of K_s-excess stars in the 14 Myr open cluster NGC 4755

Detection of K_s-excess stars in the 14 Myr open cluster NGC 4755

Spatial dependence of 2MASS luminosity and mass functions in the old open cluster NGC 188

Astrophysical parameters of 14 open clusters projected close to the Galactic plane

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NGC 2180: A disrupting open cluster?

Cited by 22 publications

References 34 publications

Detection of Ks-excess stars in the 14 Myr open cluster NGC 4755

Detection of Ks-excess stars in the 14 Myr open cluster NGC 4755

Spatial dependence of 2MASS luminosity and mass functions in the old open cluster NGC 188

Astrophysical parameters of 14 open clusters projected close to the Galactic plane

Contact Info

Product

Resources

About

Detection of K_s-excess stars in the 14 Myr open cluster NGC 4755

Detection of K_s-excess stars in the 14 Myr open cluster NGC 4755