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SCYON Issue 60 edited by Giovanni Carraro, Martin Netopil, and Ernst Paunzen http://www.univie.ac.at/scyon/ email: [email protected] SCYON Issue No. 61 August 19th, 2014 Dear subscribers, As many of you heard about, IAU is undergoing a major revolution. This initially involved re- structuring at Division level. Old divisions disappeared before last General Assembly in Beijing in 2012, and new Divisions took place. It is now the turn of Commissions to evolve into more active and better representing entities. Many old Commissions were in fact stagnant. This process touches also the actual Commission 37 Star Clusters and Associations, which will disappear soon before the next General Assembly in Honolulu in 2015. The process of reinstating a commission on star clusters within Division H (Interstellar Matter and Local Universe) already started. A team of active and well recognised colleagues in the field, led by Richard de Grijs, already submitted a Letter of Intent to the IAU secretariat. The team is composed by Richard who will act as new commission president, Amanda Karakas, who will act as new commission vice-president, Sally Oey, and Giovanni Carraro (as actual commission president). The Letter of Intent focused on stressing how active is the field of star clusters, from their birth to their dissolution, and their role as tracers of galaxy structure and evolution. Besides, the letter also remarks the importance of this newsletter (SCYON) as an information driver. In the future commission, we would like SCYON to be a sort of official commission newsletter. A full proposal will then be submitted by 31 January, 2015. CONTENTS About the Newsletter Abstracts of refereed papers . 2 SCYON publishes abstracts from any Star Forming Regions ..................2 area in astronomy, which are relevant to Galactic Open Clusters .................4 research on star clusters. We welcome all Galactic Globular Clusters .............7 kinds of submitted contributions (abstracts Clusters in the Magellanic clouds .......8 of refereed papers or conference proceedings, The most distant clusters ..............9 PhD summaries, and general announcements Dynamical evolution - Simulations . 12 of e.g. conferences, databases, tools, etc.) Miscellaneous .........................14 Conferences and Announcements .........16 The mission of this newsletter is to help all the researchers in the field with a quick and efficient link to the scientific activity in the field. We encourage everybody to contribute to the new releases! New abstracts can be submitted at any time using the webform on the SCYON homepage. http://www.univie.ac.at/scyon Star Forming Regions 2 §Star Forming Regions ¤ ¦ ¥ Testing the universality of the IMF with Bayesian statistics: young clusters Sami Dib 1;2 (1) Niels Bohr International Academy, Niels Bohr Institute, Copenhagen, Denmark; (2) Centre for Star and Planet Formation, University of Copenhagen, Copenhagen, Denmark The universality of the stellar initial mass function (IMF) is tested using Bayesian statistics with a sample of eight young Galactic stellar clusters (IC 348, ONC, NGC 2024, NGC 6611, NGC 2264, ρ Ophiuchi, Chameleon I, and Taurus). We infer the posterior probability distribution function (pPDF) of the IMF parameters when the likelihood function is described by a tapered power law function, a lognormal distribution at low masses coupled to a power law at higher masses, and a multi-component power law function. The inter-cluster comparison of the pPDFs of the IMF parameters for each likelihood function shows that these distributions do not overlap within the 1σ uncertainty level. Furthermore, the most probable values of the IMF parameters for most of the clusters deviate sub- stantially from their values for the Galactic field stellar IMF. We also quantify the effects of taking into account the completeness correction as well as the uncertainties on the measured masses. The inclusion of the former affects the inferred pPDFs of the slope of the IMF at the low mass end while considering the latter affects the pPDFs of the slope of the IMF in the intermediate- to high mass regime. As variations are observed in all of the IMF parameters at once and for each of the considered likelihood functions, even for completeness corrected samples, we argue that the observed variations are real and significant, at least for the sample of eight clusters considered in this work. The results presented here clearly show that the IMF is not universal. Accepted by : Monthly Notices of the Royal Astronomical Society http://arxiv.org/abs/1405.3287 .................................................................................................... NGC 7538 : Multiwavelength Study of Stellar Cluster Regions associated with IRS 13 and IRS 9 sources K. K. Mallick 1, D. K. Ojha 1, M. Tamura 2, and 7 co-authors (1) Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai, India; (2) National Astronomical Observatory of Japan, Tokyo, Japan We present deep and high-resolution (FWHM ∼ 0.400) near-infrared (NIR) imaging observations of the NGC 7538 IRS 1{3 region (in JHK bands), and IRS 9 region (in HK bands) using the 8.2m Subaru telescope. The NIR analysis is complemented with GMRT low-frequency observations at 325, 610, and 1280 MHz, molecular line observations of H13CO+ (J=1{0), and archival Chandra X-ray observations. Using the 'J-H/H-K' diagram, 144 Class II and 24 Class I young stellar object (YSO) candidates are identified in the IRS 1{3 region. Further analysis using 'K/H-K' diagram yields 145 and 96 red sources in the IRS 1{3 and IRS 9 regions, respectively. A total of 27 sources are found to have X-ray counterparts. The YSO mass function (MF), constructed using a theoretical mass-luminosity relation, shows peaks at substellar (∼0.08{0.18 M ) and intermediate (∼1{1.78 M ) mass ranges for the IRS 1{3 region. The MF can be fitted by a power law in the low mass regime with a slope of Γ ∼ 0.54{0.75, which is much shallower than the Salpeter value of 1.35. An upper limit of 10.2 is obtained for the star to brown dwarf ratio in the IRS 1{3 region. GMRT maps show a compact HII region associated with the IRS 1{3 sources, whose spectral index of 0.87±0.11 suggests optical thickness. Star Forming Regions 3 This compact region is resolved into three separate peaks in higher resolution 1280 MHz map, and the 'East' sub-peak coincides with the IRS 2 source. H13CO+ (J=1{0) emission reveals peaks in both IRS 1{3 and IRS 9 regions, none of which are coincident with visible nebular emission, suggesting the presence of dense cloud nearby. The virial masses are approximately of the order of 1000 M and 500 M for the clumps in IRS 1{3 and IRS 9 regions, respectively. Accepted by : Monthly Notices of the Royal Astronomical Society http://arxiv.org/abs/1407.1987 .................................................................................................... The orbital motion of the Quintuplet cluster - a common origin for the Arches and Quintuplet clusters? A. Stolte 1, B. Hussmann 1, M. R. Morris 2, and 6 co-authors (1) Argelander Institut f¨urAstronomie, Bonn, Germany; (2) Division of Astronomy and Astrophysics, UCLA, Los Angeles, USA We investigate the orbital motion of the Quintuplet cluster near the Galactic center with the aim of constraining formation scenarios of young, massive star clusters in nuclear environments. Three epochs of adaptive optics high-angular resolution imaging with Keck/NIRC2 and VLT/NACO were obtained over a time baseline of 5.8 years, delivering an astrometric accuracy of 0.5{1 mas/yr. Proper motions were derived in the cluster reference frame and were used to distinguish cluster members from the majority of field stars. Fitting the cluster and field proper motion distributions with 2D gaussian models, we derive the orbital motion of the cluster for the first time. The Quintuplet is moving with a 2D velocity of 132 ± 15 km s−1 with respect to the field along the Galactic plane, which yields a 3D orbital velocity of 167 ± 15 km s−1 when combined with the previously known radial velocity. From a sample of 119 stars measured in three epochs, we derive an upper limit to the velocity dispersion in −1 the core of the Quintuplet cluster of σ1D < 10 km s . Knowledge of the three velocity components of the Quintuplet allows us to model the cluster orbit in the potential of the inner Galaxy. Comparing the Quintuplet's orbit with the Arches orbit, we discuss the possibility that both clusters originated in the same area of the central molecular zone. [abridged] Accepted by : Astrophysical Journal http://arxiv.org/abs/1407.1854 Galactic Open Clusters 4 §Galactic Open Clusters ¤ ¦ ¥ A uvbyCaHbeta Analysis of the Old Open Cluster, NGC 6819 B. J. Anthony-Twarog 1, C. P. Deliyannis 2, and B. A. Twarog 1 (1) University of Kansas; (2) Indiana University NGC 6819 is a richly populated, older open cluster situated within the Kepler field. A CCD survey of the cluster on the uvbyCaHbeta system, coupled with proper-motion membership, has been used to isolate 382 highly probable, single-star unevolved main-sequence members over a 20-arcminute field centered on the cluster. From 278 F dwarfs with high precision photometry in all indices, a mean reddening of E(b-y) = 0.117 ± 0.005 or E(B-V) = 0.160 ± 0.007 is derived, where the standard errors of the mean include both internal errors and the photometric zero-point uncertainty. With the reddening fixed, the metallicity derived from the same 278 stars is [Fe/H] = −0.116 ± 0.101 from m1 and −0.055 ± 0.033 from hk, for a weighted average of [Fe/H] = −0.06 ± 0.04, where the quoted standard errors of the mean values include the internal errors from the photometric scatter plus the uncertainty in the photometric zero points.
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