Open Cluster Groups and Complexes Dissertation zur Erlangung des akademischen Grades "doctor rerum naturalium" (Dr. rer. nat.) in der Wissenschaftsdisziplin "Astrophysik" eingereicht an der Mathematisch-Naturwissenschaftlichen Fakultat¨ der Universitat¨ Potsdam angefertigt am Leibnitz-Institut fur¨ Astrophysik Potsdam (AIP) von Dipl.Phys.Claudia Conrad unter Betreuung von:Prof.Dr.Matthias Steinmetz, Dr.Roelof S. de Jong, Dr.Ralf-Dieter Scholz, Dr.Olivier V. Schnurr Potsdam,June 15, 2015 Published online at the Institutional Repository of the University of Potsdam: URN urn:nbn:de:kobv:517-opus4-77605 http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-77605 ”Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist. Be curious. And however difficult life may seem, there is always something you can do and succeed at. It matters that you don’t just give up.“ Stephen Hawking (In an Interview with Diane Sawyer, for ABC News, June 2010) Contents List of Figures ............................. vii List of Tables ............................. xi Abstract ................................1 Zusammenfassung ...........................3 1 Introduction .............................5 1.1 General aspects ...........................5 1.1.1 Open clusters..........................5 1.1.2 Stellar associations........................9 1.2 The hierarchy of star formation .....................9 1.3 Galactic structure and dynamics .................... 12 1.4 Past investigations on open clusters and stellar associations .......... 13 1.5 Studies on structures in the open cluster population ............. 14 1.6 Outline of this thesis ......................... 15 2 The Catalogues ........................... 17 2.1 Catalogues on Galactic open clusters................... 17 2.1.1 DAML............................ 17 2.1.2 The COCD and CSOCA...................... 18 2.1.3 The CRVAD and CRVOCA..................... 20 2.2 The RAdial Velocity Experiment (RAVE)................. 21 2.2.1 Binary studies in RAVE...................... 23 2.2.2 Dedicated open cluster observations in RAVE.............. 24 3 Sample characteristics ........................ 25 3.1 Open cluster members ........................ 25 3.1.1 Sample selection and data quality................... 26 3.1.2 Radial velocities......................... 30 3.1.3 Metallicities.......................... 33 3.2 Open cluster mean values ....................... 36 3.2.1 Radial velocities......................... 36 3.2.2 Binarity fraction......................... 39 3.2.3 Metallicities.......................... 39 3.2.4 Summary on the RAVE data..................... 42 3.3 Final set of parameters for my open cluster working sample ......... 43 3.3.1 Combined radial velocities..................... 43 3.3.2 Distances........................... 45 3.3.3 Proper motions......................... 46 3.3.4 Ages............................. 49 3.3.5 Metallicities.......................... 50 4 Open cluster groups and complexes .................. 53 4.1 6D phase-space information ...................... 53 4.2 Identification of open cluster groupings.................. 55 4.3 Verification of open cluster groupings .................. 58 4.3.1 The reference catalogue...................... 58 4.3.2 Monte-Carlo simulations...................... 68 4.4 Characterisation of the found open cluster groupings ............ 76 4.4.1 Comparison to the literature..................... 82 5 Discussion and Outlook ....................... 87 Acknowledgment ........................... 93 Bibliography.............................. 95 Appendix .............................. 101 A Tables for the results from RAVE ................... 101 A.1 Radial Velocities .......................... 101 A.2 Metallicities ............................ 102 B Tables for the final working sample from the COCD .......... 111 C Additional information on the found OC groupings .......... 139 C.1 For linking lengths 100 pc and 10 km/s .................. 139 C.2 For linking lengths 100 pc and 20 km/s .................. 159 Bibliography for the Appendix ..................... 165 List of Figures 1.1 Colour-magnitude diagrams generated for four Galactic open clusters from the COCD . .6 1.2 Images of known Galactic open clusters . .7 1.3 Histograms for the radii and number of members in Galactic open clusters . .8 1.4 Spatial distribution of Galactic open clusters . .8 1.5 Images of known Galactic stellar associations . .9 1.6 Illustration of mass segregation . 10 1.7 Visualisation of simulated mass loss in open clusters . 11 1.8 Distribution in Z with respect to cluster age for Galactic open clusters . 12 1.9 Schematic for hierarchical star formation . 14 2.1 Schematic for the membership selection procedure in the COCD . 18 2.2 Comparison between the computed and literature RV data in the CRVOCA . 20 2.3 Footprint of RAVE DR4 . 23 3.1 Spatial distribution of stars in open cluster areas in the RAVE footprint . 25 3.2 eRV∗ vs. SNR distribution of my high-quality RV sample in RAVE DR4 . 26 3.3 eRV∗ vs. R distribution of my high-quality RV sample in RAVE DR4 . 26 3.4 eRV∗ vs. corr_RV distribution of my high-quality RV sample in RAVE DR4 . 27 3.5 Histograms for eRV∗ for the different RV samples . 28 3.6 Magnitude dependent eRV∗ histograms for my high-quality RV sample . 29 3.7 Distribution of eRV∗ with respect to log g for the selective RV samples . 30 3.8 Distribution of eRV∗ and log g with respect to b for the selective RV samples . 30 3.9 VJohnson histograms in RAVE and CRVAD-2 . 31 3.10 RV comparison between RAVE and CRVAD-2 . 32 3.11 RV difference distributions between RAVE and the CRVAD-2 source catalogues . 33 3.12 Distribution of e[M=H]∗ with respect to SNR for my high-quality RV sample . 34 3.13 [M=H] distribution with respect to SNR for my high-quality RV sample . 34 3.14 [M=H] distribution with respect to R for my high-quality RV sample . 34 3.15 [M=H] distribution with respect to VJohnson for my high-quality [M=H] sample . 35 3.16 Histogram for the number of individual measurements/stars used to derive RV ......... 37 3.17 RV comparison between RAVE and reference values . 37 3.18 Comparison between σRV and eRV∗ in CRVAD-2 and RAVE . 38 3.19 Histogram for the number of individual measurements/stars used to obtain [M=H]....... 40 3.20 [M=H] comparison between RAVE DR4 and DAML . 41 3.21 [M=H] comparison between the RAVE chemical pipeline and DAML . 41 vii 3.22 Summarised histograms for the number of individual measurements used to compute RV and for the resulting eRV for my final working sample . 43 3.23 Radial velocity dependence on Galactic longitude . 44 3.24 Histogram for open cluster distances from the COCD . 45 3.25 Histogram for the proper motion uncertainties in my working sample . 46 3.26 Tangential velocity dependence on Galactic longitude . 47 3.27 Histogram for the uncertainties in the tangential velocities . 48 3.28 Histogram for the open cluster ages in the COCD . 49 3.29 Relation between brightest member and age of clusters in the COCD . 49 3.30 Age-metallicity relation for my working sample . 50 3.31 Radial and vertical metallicity gradients . 51 4.1 Velocity field and UVW dependency on Galactic longitude in the working sample . 54 4.2 Histograms for the UVW uncertainties in my working sample . 55 4.3 Nearest neighbour histograms in 6D phase-space for the working sample . 56 4.4 Distribution of identified open cluster groupings in coordinate and velocity space . 57 4.5 Histograms for the size of the identified open cluster groupings for both sets of linking lengths 58 4.6 Density profile in the XY-plane of open clusters in the MWSC within 1.8 kpc . 58 4.7 Effect of extinction and Galactic spiral arms on the spatial distribution of MWSC clusters . 59 4.8 Comparison of the spatial distribution between COCD and MWSC . 60 4.9 Comparison in the Galactic coordinates between COCD and MWSC . 60 4.10 Comparison for the location of the identified open cluster groupings between the COCD and MWSC.............................................. 61 4.11 Comparison of the separation histograms for the nearest neighbours in the COCD and MWSC 61 4.12 Comparison of the distributions for the Cartesian XYZ-coordinates and UVW-velocities be- tween the COCD and MWSC . 62 4.13 Difference distributions for the Cartesian coordinates and velocities in the COCD and MWSC 63 4.14 Difference distributions for the cluster distances, proper motions, tangential and radial veloci- ties in the COCD and MWSC . 64 4.15 Distributions of the XYZ-coordinates and UVW-velocities for the randomised sample of the MCMWS C and my working sample . 66 4.16 Distributions for the spatial separation and velocity difference of the nearest neighbours in XYZ for the randomised sample of the MCMWS C and my working sample . 67 4.17 Histograms for the number and size of identified open cluster groupings for the MCMWS C using 100 pc and 10 km/s and in comparison with the results from my working sample . 67 4.18 Histograms for the number and size of identified open cluster groupings for the MCMWS C using 100 pc and 20 km/s and in comparison with the results from my working sample . 68 4.19 Distributions for the spatial separation and velocity difference of the nearest neighbours in XYZ for the randomised sample of the MCUni and my working sample . 69 4.20 Histograms for the number and size of identified open cluster groupings for the MCUni using linking lengths of 100 pc and 10 km/s in comparison with my working sample . 69 4.21 Histograms for the number and size of identified open cluster groupings for the MCUni using linking lengths of 100 pc and 20 km/s in comparison with my working sample . 70 4.22 Distributions for the Cartesian coordinates and velocities for the MCUni in comparison with the distributions for my working sample . 71 4.23 Distribution in X and Y for the MCXYcheck compared to the distributions in the MWSC . 72 4.24 2D-Histogram for the number density of COCD clusters in the XY-plane .