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A Second Shell in the Fornax dSph Galaxy

Published online by Cambridge University Press:  05 March 2013

M. G. Coleman  and
G. S. Da Costa
M. G. Coleman
Affiliation:
Research School of Astronomy & Astrophysics, Institute of Advanced Studies, Australian National University, Weston Creek ACT 2611, Australia
G. S. Da Costa*
Affiliation:
Research School of Astronomy & Astrophysics, Institute of Advanced Studies, Australian National University, Weston Creek ACT 2611, Australia
*
BCorresponding author. Email: [email protected]
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Abstract

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In the search for tidal structure in Galactic satellite systems, we have conducted a photometric survey over a 10 deg2 area centred on the Fornax dSph galaxy. The survey was made in two colours, and the resulting colour–magnitude data were used as a mask to select candidate Fornax RGB stars, thereby increasing the contrast of Fornax stars to background sources in the outer regions. Previously, we reported the presence of a shell (age 2 Gyr) located towards the centre of Fornax. In this contribution we reveal a second shell, significantly larger than the first, located 1.3° north-west from the centre of Fornax, outside the nominal tidal radius. Moreover, the distribution of Fornax RGB stars reveals two lobes extending to the spatial limit of our survey, and aligned with the minor axis and with the two shells. These results support the hypothesis of a merger between Fornax and a gas-rich companion approximately 2 Gyr ago.

Keywords

galaxies: dwarfgalaxies: individual (Fornax)galaxies: photometrygalaxies: stellar contentgalaxies: interactionsGalaxy: halo
Type
ASA Conference 2004
Information
Publications of the Astronomical Society of Australia , Volume 22 , Issue 2 , 2005 , pp. 162 - 165
Copyright
Copyright © Astronomical Society of Australia 2005

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