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Chemical evolution of r-process elements in the Draco dwarf spheroidal galaxy

Published online by Cambridge University Press:  09 May 2016

M. N. Ishigaki ,
T. Tsujimoto ,
T. Shigeyama  and
W. Aoki
M. N. Ishigaki
Affiliation:
Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo 5-1-5 Kashiwanoha, Kashiwa, 277-8583, Japan email: [email protected]
T. Tsujimoto
Affiliation:
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan email: [email protected]
T. Shigeyama
Affiliation:
Research center for the early universe, University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan email: [email protected]
W. Aoki
Affiliation:
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan email: [email protected]
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Abstract

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A dominant astrophysical site for r-process, which is responsible for producing heavy neutron-capture elements, is unknown. Dwarf spheroidal galaxies around the Milky Way halo provide ideal laboratories to investigate the origin and evolution of r-process elements. We carried out high-resolution spectroscopic observations of three giant stars in the Draco dwarf spheroidal galaxy to estimate their europium abundances. We found that the upper-limits of [Eu/H] are very low in the range [Fe/H] < −2, while this ratio is nearly constant at higher metallicities. This trend is not well reproduced with models which assume that Eu is produced together with Fe by SNe, and may suggest the contribution from other objects such as neutron-star mergers.

Keywords

stars:abundancesgalaxies:dwarfgalaxies:individual (Draco)
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. 310 - 311
Copyright
Copyright © International Astronomical Union 2016 

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