Photometric and spectroscopic study of low mass embedded star clusters in reflection nebulae

Soares, Jules Batista; Bica, E.; Ahumada, A. V.; Clariá, J. J.

doi:10.1051/0004-6361:20048242

Cited by 8 publications

(15 citation statements)

References 38 publications

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“…This associates a membership probability (P jon ) with each star in the on-cluster area. Details are given in Soares et al (2005). The 2CD analysis allows us to derive the mean extinction of the embedded clusters, using reddening vectors and intrinsic colours as in Soares et al (2005).…”

Section: Methods Of Analysismentioning

confidence: 99%

“…Details are given in Soares et al (2005). The 2CD analysis allows us to derive the mean extinction of the embedded clusters, using reddening vectors and intrinsic colours as in Soares et al (2005). In addition, the 2CD analysis provides information about the evolutionary stage of the cluster, through the fraction of stars with K s band excess, which is characteristic of pre-main sequence (PMS) stars (Carpenter et al 1993;Lada & Adams 1992).…”

Section: Methods Of Analysismentioning

confidence: 99%

“…The cluster age can be estimated by means of the K s excess method (Soares et al 2005, and references therein). In this radius (arcmin) radius (arcmin) method the essential information is given by those stars which present K s excess and by the total number of cluster members.…”

Section: Methods Of Analysismentioning

confidence: 99%

“…Interstellar extinction of the stars located in the domain of normal reddening in the ((J − H), (H − K s )) diagram, containing weak T Tauri stars, and in the domain of classical K s values can be obtained by using reddening vectors and intrinsic colours (Soares et al 2005).…”

Section: Structurementioning

confidence: 99%

“…On the other hand, lower mass embedded clusters are interesting because they may contain non-ionizing stars as their most massive members, thus producing particular interactions with the interstellar medium (Soares & Bica 2002Soares 2006). Optical stars were spectroscopically observed in Soares et al (2005) aiming at studying the more massive possible members.…”

Section: Introductionmentioning

confidence: 99%

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Near infrared photometric and optical spectroscopic study of 22 low mass star clusters embedded in nebulae

Soares¹,

Bica²,

Ahumada³

et al. 2007

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Aims. Among the star clusters in the Galaxy, those embedded in nebulae represent the youngest group, which has only recently been explored. The analysis of a sample of 22 candidate embedded stellar systems in reflection nebulae and/or HII environments is presented. Methods. We employed optical spectroscopic observations of stars in the directions of the clusters carried out at CASLEO (Argentina) together with near infrared photometry from the 2MASS catalogue. Our analysis is based on source surface density, colour−colour diagrams and on theoretical pre-main sequence isochrones. We take into account the field star contamination by carrying out a statistical subtraction. Results. The studied objects have the characteristics of low mass systems. We derive their fundamental parameters. Most of the cluster ages are younger than 2 Myr. The studied embedded stellar systems in reflection nebulae and/or HII region complexes do not have stars of spectral types earlier than B. The total stellar masses locked in the clusters are in the range 20−220 M . They are found to be gravitationally unstable and are expected to dissolve in a timescale of a few Myr.

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Section: Methods Of Analysismentioning

confidence: 99%

Section: Methods Of Analysismentioning

confidence: 99%

Section: Methods Of Analysismentioning

confidence: 99%

Section: Structurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Near infrared photometric and optical spectroscopic study of 22 low mass star clusters embedded in nebulae

Soares¹,

Bica²,

Ahumada³

et al. 2007

A&A

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The embedded cluster DBSB 48 in the nebula Hoffleit 18: Comparison with Trumpler 14

et al. 2008

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We derive fundamental parameters of the embedded cluster DBSB 48 in the southern nebula Hoffleit 18 and the very young open cluster Trumpler 14, by means of deep JHK s infrared photometry. We build colour-magnitude and colour-colour diagrams to derive reddening and age, based on main sequence and pre-main sequence distributions. Radial stellar density profiles are used to study cluster structure and guide photometric diagram extractions. Field-star decontamination is applied to uncover the intrinsic cluster sequences in the diagrams. Ages are inferred from Kexcess fractions. A prominent pre-main-sequence population is present in DBSB 48, and the K-excess fraction f K = 55 ± 6% gives an age of 1.1 ± 0.5 Myr. A mean reddening of A Ks = 0.9 ± 0.03 was found, corresponding to A V = 8.2 ± 0.3. The cluster CMD is consistent with the far kinematic distance of 5 kpc for Hoffleit 18. For Trumpler 14 we derived similar parameters as in previous studies in the optical, in particular an age of 1.7 ± 0.7 Myr. The fraction of stars with infrared excess in Trumpler 14 is f K = 28 ± 4%. Despite the young ages, both clusters are described by a King profile with core radii R core = 0.46 ± 0.05 pc and R core = 0.35 ± 0.04 pc, respectively for DBSB 48 and Trumpler 14. Such cores are smaller than those of typical open clusters. Small cores are probably related to the cluster formation and/or parent molecular cloud fragmentation. In DBSB 48, the magnitude extent of the upper main sequence is ∆ K s ≈ 2 mag, while in Trumpler 14 it is ∆ K s ≈ 5 mag, consistent with the estimated ages.

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Investigating the borderline between a young star cluster and a small stellar association: a test case with Bochum 1

Bica

Bonatto

Dutra

2008

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Context. Usually, a loose stellar distribution can be classified as an OB stellar group, an association, or a young open cluster. We compare data with the typical OB association Vul OB1. Aims. Here, we discuss the nature of Bochum 1, a typical example of an object affected by the above classification problem. Methods. Field-decontaminated 2MASS photometry is used to analyse colour-magnitude diagrams (CMDs) and stellar radial density profiles (RDPs) of the structures present in the region of Bochum 1. Results. The field-decontaminated CMD of Bochum 1 shows main sequence (MS) and pre-main sequence (PMS) stars. We report two new small angular-size, compact young clusters and one embedded cluster in the area of Bochum 1. Vul OB1 harbours the young open cluster NGC 6823 and the very compact embedded cluster Cr 404. The Vul OB1 association includes the H II region Sh2-86, and its stellar content is younger (≈3 Myr) than that of Bochum 1 (≈9 Myr), which shows no gas emission. Bochum 1 harbours one of the newly found compact clusters as its core. The RDP of Bochum 1 is irregular and cannot be fitted by a King-like profile, which suggests significant erosion or dispersion of stars from a primordial cluster. Similarly to Bochum 1, the decontaminated CMD of NGC 6823 presents conspicuous MS and PMS sequences. Taken separately, RDPs of MS and PMS stars follow a King-like profile. The core shows an excess density of MS stars that mimics the profile of a post-core collapse cluster. At such a young age, it can be explained by an excess of stars formed in the prominent core. Conclusions. The present study suggests that Bochum 1 is a star cluster fossil remain that might be dynamically evolving into an OB association. Bochum 1 may be a missing link connecting early star cluster dissolution with the formation of low-mass OB associations.

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Photometric and spectroscopic study of low mass embedded star clusters in reflection nebulae

Cited by 8 publications

References 38 publications

Near infrared photometric and optical spectroscopic study of 22 low mass star clusters embedded in nebulae

Near infrared photometric and optical spectroscopic study of 22 low mass star clusters embedded in nebulae

The embedded cluster DBSB 48 in the nebula Hoffleit 18: Comparison with Trumpler 14

Investigating the borderline between a young star cluster and a small stellar association: a test case with Bochum 1

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