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Observational Windows on the Dynamics of Open Clusters

Observational Windows on the Dynamics of Open Clusters. Robert D. Mathieu University of Wisconsin - Madison. “Typical” Open Cluster M = 300 M o R c = 1 pc R t = 20 pc s = 0.3 km s -1 r c = 10 M o pc -3. WIYN Open Cluster Study.

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Observational Windows on the Dynamics of Open Clusters

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  1. Observational Windowsonthe Dynamics of Open Clusters Robert D. Mathieu University of Wisconsin - Madison

  2. “Typical” Open Cluster M = 300 Mo Rc = 1 pc Rt = 20 pc s = 0.3 km s-1 rc = 10 Mo pc-3

  3. WIYN Open Cluster Study • Comprehensive and definitive photometric, astrometric, and spectroscopic databases for new fundamental open clusters. • A body of investigations which address critical astrophysical problems through study of open clusters.

  4. WOCS Senior Scientists • C. Deliyannis Indiana photometry, spectroscopy, abundances • P. Demarque Yale theoretical stellar evolution • T. Girard Yale astrometry, proper motions • K. Honeycutt Indiana photometric monitoring, compact binaries • R. Mathieu Wisconsin radial velocities, binary populations • I. Platais JHU astrometry, proper motions, photometry • A. Sarajedini Florida photometry, stellar evolution • W. van Altena Yale astrometry, proper motions • T. von Hippel Texas photometry, luminosity functions

  5. WOCS Clusters [Fe/H] Second Generation Log Age (Gyrs) First Generation

  6. WOCS Strategy • Imaging/Photometry • Deep UBVRI images of cluster cores • UBVRI wide-field surveys to tidal radii • Photometric monitoring for variability • Astrometry • Precise stellar positions • Deep, wide-field proper motions • Spectroscopy • Abundance determinations • Metallicity, CNO, and lithium • Precise radial velocities • Projected rotation velocities • Stellar activity

  7. NGC 188 1840 pc E(B-V) = 0.04 7 Gyr [Fe/H] = -0.12 ≈ 1000 Mo (d = +85o)

  8. Photometry Precision ≈ 0.012 mag (BVRI) ≈ 0.03 mag (U) Accuracy ≈ 0.02 mag (BVRI) Sarajedini et al. 1999; WOCS II

  9. Photometry Von Hippel et al. 1999; WOCS I

  10. Proper Motions 0.15 mas yr-1 Positions 0.2 mas 7812 objects V=21 0.75 deg2 Platais et al. 2004; WOCS XVII

  11. Radial Velocities 0.4 km s-1 500 VR/night V < 16.5 0.75 deg2 (WIYN 3.5m)

  12. VR

  13. 93 spectroscopic binaries 55 orbital solutions P < 3000d Mathieu et al. 2004; WOCS XVIII

  14. Outcomes for Stellar Dynamics • Superb 3-dimensional membership determination • for entire evolved cluster population to beyond tidal radius • Reliable 2-dimensional membership determination • to 0.5 Mo and beyond tidal radius • Photometric mass function to 0.1 Mo in cluster core • Complete census of short-period, solar-type binary population, • with orbital elements

  15. The Interface of Two Classical Fields:Stellar Astrophysics and Stellar Dynamics

  16. M67 4.5 Gyr [Fe/H] = -0.04 ≈ 1000 Mo 1.3 Mo

  17. Binary Frequency Spectroscopic Binaries • For P < 1000d • M67 19% ± 4 • Field 16% ± 3 Mathieu, Latham & Griffin 1990 Mathieu et al. 2004

  18. Mathieu et al. 2003 S1063 P=18.4 d e = 0.21 g = 34.3 km/s pm = 97% S1113 P=2.8 d e = 0 g = 33.4 km/s pm = 98%

  19. Tidal Circularization Rates

  20. NGC 188 7 Gyr Pcutoff = 14.9 days Mathieu et al. 2004

  21. Zahn & Bouchet 1989 Witte & Savonije 2002 Claret & Cunha 1997 (Zahn 1977) Meibom & Mathieu 2004

  22. Opening Thoughtson Choice of Open Cluster(s)

  23. WOCS Clusters [Fe/H] Second Generation Log Age (Gyrs) First Generation

  24. Optimal Cluster Properties (with an observational bias) • Richseveral thousand members to 0.1 Mo • evolution without complete evaporation • meaningful statistics • “Old”age greater than 1 Gyr • multiple relaxation times • solar-mass evolution • “Nearby”d < 2 kpc • accessible main-sequence binary population • Accessible-20o < d < +20o • observable from both hemispheres • Out of Plane| b | > 10o • minimize field-star contamination, especially at Rt

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