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Contributions to the Galactic halo from in-situ, kicked-out, and accreted stars

Published online by Cambridge University Press:  09 May 2016

Allyson A. Sheffield ,
Kathryn V. Johnston ,
Katia Cunha ,
Verne V. Smith  and
Steven R. Majewski
Allyson A. Sheffield
Affiliation:
LaGuardia Community College, City University of New York, Department of Natural Sciences, 31-10 Thomson Ave., Long Island City, NY, 11101, USA email: [email protected]
Kathryn V. Johnston
Affiliation:
Columbia University, Dept. of Astronomy, Mail Code 5246, New York, NY, 10027, USA
Katia Cunha
Affiliation:
Observatório Nacional, Rua General José Cristino, 77, 20921-400 São Cristóvão, Rio de Janeiro, RJ, Brazil
Verne V. Smith
Affiliation:
National Optical Astronomy Observatories, Tucson, AZ, 98765, USA
Steven R. Majewski
Affiliation:
University of Virginia, Dept. of Astronomy, P.O. Box 400325, Charlottesville, VA, 22904, USA
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Abstract

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We report chemical abundances for a sample of 66 M giants with high S/N high-resolution spectroscopy in the inner halo of the Milky Way. The program giant stars have radial velocities that vary significantly from those expected for stars moving on uniform circular orbits in the Galactic disk. Thus, based on kinematics, we expect a sample dominated by halo stars. Abundances are derived for α-elements and neutron capture elements. By analyzing the multi-dimensional abundance space, the formation site of the halo giants – in-situ or accreted – can be assessed. Of particular interest are a class of stars that form in-situ, deep in the Milky Way's gravitational potential well, but are “kicked out” of the disk into the halo due to a perturbation event. We find: (1) our sample is dominated by accreted stars and (2) tentative evidence of a small kicked-out population in our Milky Way halo sample.

Keywords

Galaxy: haloGalaxy: structurestars: abundances
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , Issue S317: The General Assembly of Galaxy Halos: Structure, Origin and Evolution , August 2015 , pp. 241 - 246
Copyright
Copyright © International Astronomical Union 2016 

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