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Title: | Deep Multi-telescope Photometry of NGC 5466. II. The Radial Behavior of the Mass Function Slope | Authors: | Beccari, G. Dalessandro, Emanuele Lanzoni, B. Ferraro, F. R. BELLAZZINI, Michele SOLLIMA, ANTONIO LUIGI |
Issue Date: | 2015 | Journal: | THE ASTROPHYSICAL JOURNAL | Number: | 814 | Issue: | 2 | First Page: | 144 | Abstract: | We use a combination of data acquired with the Advanced Camera for Survey on board the Hubble Space Telescope and the Large Binocular Camera (LBC-blue) mounted on the Large Binocular Telescope to sample the main sequence (MS) stars of the globular cluster (GC) NGC 5466 in the mass range 0.3 < M/M<SUB>☉</SUB> < 0.8. We derive the cluster's Luminosity Function (LF) in several radial regions, from the center of the cluster out to the tidal radius. After corrections for incompleteness and field contamination, this was compared to theoretical LFs, obtained by multiplying a simple power-law mass function in the form dN/dm \propto {m}<SUP>α </SUP> by the derivative of the mass-luminosity relationship of the best-fit isochrone. We find that α varies from -0.6 in the core region to -1.9 in the outer region. This fact allows us to prove by observation that the stars in NGC 5466 have experienced the effects of mass segregation. We compare the radial variation of α from the center out to 5 core radii (r<SUB>c</SUB>) in NGC 5466 and the GC M10, finding that the gradient of α in the first 5r<SUB>c</SUB> is more than a factor of 2 shallower in NGC 5466 than in M10, in line with the differences in the clusters’ relaxation timescales. NGC 5466 is dynamically younger than M10, with two-body relaxation processes only recently starting to shape the distribution of MS stars. This result fully agrees with the conclusion obtained in our previous works on the radial distribution of blue straggler stars, further confirming that this can be used as an efficient clock to measure the dynamical age of stellar systems. <P />Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia. | Acknowledgments: | We wish to thank the anonymous referee for insightful comments that have helped to improve the presentation of our work. This research is part of the project COSMIC-LAB funded by the European Research Council (under contract ERC-2010-AdG-267675). This research used the facilities of the Italian Center for Astronomical Archive (IA2) operated by INAF at the Astronomical Observatory of Trieste. Also based on observations made with the NASA/ESA Hubble Space Telescope , obtained from the data archive at the Space Telescope Institute. STScI is operated by the association of Universities for Research in Astronomy, Inc. under the NASA contract NAS 5-26555. | URI: | http://hdl.handle.net/20.500.12386/23510 | URL: | https://iopscience.iop.org/article/10.1088/0004-637X/814/2/144 | ISSN: | 0004-637X | DOI: | 10.1088/0004-637X/814/2/144 | Bibcode ADS: | 2015ApJ...814..144B | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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