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The Arcturus Moving Group: Its Place in the Galaxy

Published online by Cambridge University Press:  01 June 2008

Mary E. K. Williams ,
Ken C. Freeman  and
Amina Helmi
Mary E. K. Williams
Affiliation:
Mt Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611, Australia email: [email protected]; [email protected] Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482, Potsdam, Germany
Ken C. Freeman
Affiliation:
Mt Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611, Australia email: [email protected]; [email protected]
Amina Helmi
Affiliation:
Kapteyn Institute, P.O. Box 800, 9700 AV Groningen, the Netherlands email: [email protected]
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Abstract

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The Arcturus moving group is a well-populated example of phase space substructure within the disk of our Galaxy. With its large rotational lag (V = −100 kms−1), metal poor nature ([Fe/H] ~ −0.6) and significant age (10 Gyr) it belongs to the Galaxy's thick disk. Traditionally regarded as the remains of a dissolved open cluster, it has recently been suggested to be a remnant of a satellite accreted by our Galaxy.

We confirm via further kinematic studies using the Nordstöm et al. (2004), Schuster et al. (2004) and RAdial Velocity Experiment (RAVE) surveys (Steinmetz et al. 2004) the existence of the group, finding it to possibly favour negative U velocities and also possibly a solar-circle phenomenon. We undertook a high-resolution spectroscopic abundance study of Arcturus group members and candidates to investigate the origin of the group. Examining abundance of Fe, Mg, Ca, Ti, Cr, Ni, Zn, Ce, Nd, Sm and Gd for 134 stars we found that the group is chemically similar to disk stars and does not exhibit a clear chemical homogeneity.

The origin of the group still remains unresolved: the chemical results are consistent with a dynamical origin but do not entirely rule out a merger one. Certainly, the Arcturus group provides a challenge to our understanding of the nature and origin of the Galaxy's thick disk.

Keywords

Galaxy: abundancesgalaxy: kinematics and dynamicsgalaxy: structure
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Issue S254: The Galaxy Disk in Cosmological Context , June 2008 , pp. 139 - 144
Copyright
Copyright © International Astronomical Union 2009

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