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Kinematics in Kapteyn's Selected Area 76: Orbital Motions Within the Highly Substructured Anticenter Stream

Carlin, Jeffrey L. and Casetti-Dinescu, Dana I. and Grillmair, Carl J. and Majewski, Steven R. and Girard, Terrence M. (2010) Kinematics in Kapteyn's Selected Area 76: Orbital Motions Within the Highly Substructured Anticenter Stream. Astrophysical Journal, 725 (2). pp. 2290-2311. ISSN 0004-637X.

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We have measured the mean three-dimensional kinematics of stars in Kapteyn's Selected Area (SA) 76 (l = 209°.3, b = 26°.4) that were selected to be Anticenter Stream (ACS) members on the basis of their radial velocities (RVs), proper motions (PMs), and location in the color-magnitude diagram. From a total of 31 stars ascertained to be ACS members primarily from its main-sequence turnoff, a mean ACS RV (derived from spectra obtained with the Hydra multi-object spectrograph on the WIYN 3.5 m telescope) of V_helio = 97.0 ± 2.8 km s^(–1) was determined, with an intrinsic velocity dispersion σ_o = 12.8 ± 2.1 km s^(–1). The mean absolute PMs of these 31 ACS members are μ_α cos δ = –1.20 ± 0.34 mas yr^(–1) and μ_δ = –0.78 ± 0.36 mas yr^(–1). At a distance to the ACS of 10 ± 3 kpc, these measured kinematical quantities produce an orbit that deviates by ~30° from the well-defined swath of stellar overdensity constituting the ACS in the western portion of the Sloan Digital Sky Survey footprint. We explore possible explanations for this and suggest that our data in SA 76 are measuring the motion of a kinematically cold sub-stream among the ACS debris that was likely a fragment of the same infalling structure that created the larger ACS system. The ACS is clearly separated spatially from the majority of claimed Monoceros ring detections in this region of the sky; however, with the data in hand, we are unable to either confirm or rule out an association between the ACS and the poorly understood Monoceros structure.

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Carlin, Jeffrey L.0000-0002-3936-9628
Grillmair, Carl J.0000-0003-4072-169X
Majewski, Steven R.0000-0003-2025-3147
Additional Information:© 2010 American Astronomical Society. Received 2010 June 30; accepted 2010 October 10; published 2010 December 6. We thank the anonymous referee for a careful reading of the manuscript, and appreciate useful discussions with Ricardo Muñoz. We gratefully acknowledge support by NSF grant AST-0807945 and NASA/JPL contract 1228235. D.I.C. acknowledges the support of NSF grant AST-0406884. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSSWeb site is The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck- Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. Facilities: WIYN (Hydra), Sloan
Group:Infrared Processing and Analysis Center (IPAC)
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Subject Keywords:astrometry; galaxies: dwarf; Galaxy: kinematics and dynamics; Galaxy: stellar content; Galaxy: structure; Local Group; stars: abundances; stars: kinematics and dynamics
Issue or Number:2
Classification Code:PACS: 98.35.Df; 98.38.Dq; 98.35.Ln
Record Number:CaltechAUTHORS:20110307-112333014
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Official Citation:Jeffrey L. Carlin et al. 2010 ApJ 725 2290 doi: 10.1088/0004-637X/725/2/2290
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:22691
Deposited By: Jason Perez
Deposited On:09 Mar 2011 21:48
Last Modified:09 Mar 2020 13:19

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