A Local Group Polar Ring Galaxy: NGC 6822 | Zendy

S. Demers | Zendy; P. Battinelli | Zendy; W. E. Kunkel | Zendy

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A Local Group Polar Ring Galaxy: NGC 6822

Author(s) -

S. Demers,

P. Battinelli,

W. E. Kunkel

Publication year - 2005

Publication title -

the astrophysical journal

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 2.376

H-Index - 489

eISSN - 1538-4357

pISSN - 0004-637X

DOI - 10.1086/500207

Subject(s) - physics , astrophysics , stellar population , galaxy , rotation (mathematics) , thick disk , velocity dispersion , local group , polar , stars , population , galaxy rotation curve , astronomy , dwarf galaxy , star formation , geometry , galaxy formation and evolution , halo , mathematics , demography , sociology

Star counts, obtained from a 2 x 2 degree area centered on NGC 6822 haverevealed an optical image of this galaxy composed of two components: inaddition to the well-known HI disk with its young stellar component, there is aspheroidal stellar structure as extensive as its HI disk but with its majoraxis 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 thisstructure display kinematics contrasting strongly with those of the HI disk.These C stars belong to the spheroid. Although devoid of gas, the spheroidrotation is consistent with the I-band Tully-Fisher relation. The orientation of the rotation axis which minimizes the stellar velocitydispersion 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 isa polar ring and the spheroidal component an erstwhile disk, a fossil remainderof a past close encounter episode.Comment: ApJ Letter, accepted, in pres

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