Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-10-27
Astrophys.J.636:L85-L88,2006
Astronomy and Astrophysics
Astrophysics
ApJ Letter, accepted, in press
Scientific paper
10.1086/500207
Star counts, obtained from a 2 x 2 degree area centered on NGC 6822 have revealed an optical image of this galaxy composed of two components: in addition to the well-known HI disk with its young stellar component, there is a spheroidal stellar structure as extensive as its HI disk but with its major axis at roughly right angles to it which we traced to at least 36 arcmin. Radial velocities of over 100 intermediate-age carbon stars found within this structure display kinematics contrasting strongly with those of the HI disk. These C stars belong to the spheroid. Although devoid of gas, the spheroid rotation is consistent with the I-band Tully-Fisher relation. The orientation of the rotation axis which minimizes the stellar velocity dispersion coincides with the minor axis of the stellar population ellipsoid, lying very nearly in the plane of the HI disk. We conclude: that the HI disk is a polar ring and the spheroidal component an erstwhile disk, a fossil remainder of a past close encounter episode.
Battinelli Paolo
Demers Serge
Kunkel William E.
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