The Milky Way Bulge Extra-Tidal Star Survey: NGC 6569
Year: 2025
Type: preprint
Abstract: We present spectroscopic evidence for tidal debris associated with the bulge globular cluster NGC 6569, based on medium-resolution (R ~ 11,000) Anglo-Australian Telescope spectra of 303 stars. Targets were selected using Blanco DECam Bulge Survey (BDBS) photometry and Gaia DR3 astrometry, spanning 7-30 arcmin (~1-5 rt, where rt is the King-model tidal radius) from the cluster center. Orbit-based modeling predicts a strongly time-variable Jacobi radius, with rJ ~ 8-11 arcmin near pericenter and ~18-22 arcmin near apocenter, so stars just outside rt can be unbound and feeding leading and lagging tidal tails. We identify 40 stars with kinematics and abundances consistent with previous, or borderline, cluster membership. The seven highest-quality candidates (S/N > 30) have mean [Fe/H] = -0.83 +/- 0.14 and [alpha/Fe] = +0.38 +/- 0.06 dex, matching the bound population. Interpreting these stars as recently stripped debris implies a present-day mass-loss rate of 1.0-1.6 solar masses per Myr, or 5.6 +/- 1.3% of the current cluster mass per Gyr. These results indicate ongoing tidal stripping of NGC 6569 and quantify its contribution to the bulge field. This paper is part of the Milky Way Bulge Extra-Tidal Star Survey (MWBest) and is our first detailed debris study of a massive bulge globular cluster.
Source: arXiv (Cornell University)
Authors: Hughes, Joanne, Kunder, Andrea, Covey, Kevin, Devine, Kathryn, Larson, Kristen A., Campos, Carlos, Price-Whelan, Adrian M., McEwen, Joseph E., Perren, Gabriel I., Johnson, Christian I., Horton, Craig, Smith, Luke, Torset, Sarah, Luna, Cynthia, Kolmanovsky, Matthew, Kovisto, Fiona, Villarta, Leander, Vuong, Vy, Simion, Iulia T., Webster, Kyle, Silva, Erika, Pilachowski, Catherine A., Rich, R. Michael, Kader, Justin A., Koch-Hansen, Andreas J., Joyce, Meridith, McAdam, Sean, Benda, Faith
Institutions: Seattle University, Saint Martin's University, Western Washington University, College of Idaho, National Solar Observatory, Flatiron Institute, Consejo Nacional de Investigaciones Científicas y Técnicas, National University of Rosario, Institute of Physics Rosario, Space Telescope Science Institute, Shanghai Normal University, Fernbank Museum of Natural History, Indiana University Bloomington, Indiana University, University of California, Los Angeles, University of California, Irvine, Heidelberg University, University of Wyoming
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7117115304
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