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The ringed X-galaxy NGC 7020The southern SO (sup +) galaxy NGC 7020 presents an unusual morphology: it includes a very regular outer ring which is completely detached and which envelops an inner ring/lens zone with a hexagon surrounding an X shape. The outer ring has a high contrast compared to those usually observed in barred galaxies, yet NGC 7020 is not obviously barred. The morphology of this galaxy poses an interesting puzzle in that the hexagonal/X zone is not a typical type of feature to find in the interior of such a regular ring. Instead, the zone bears a striking resemblance to the edge-on galaxy IC 4767, recently studied by Whitmore and Bell (1988 = WB88) and dubbed by them as the X-galaxy because its inner regions appear to be crossed by two distinct enhancements lined at plus or minus 22 deg with respect to the major axis. The observation of a similar phenomenon in NGC 7020 is interesting because of the suggestion by WB88 that X structures could be related to accretion of matter associated with a merger or tidal encounter between an SO and a small satellite galaxy. If this interpretation is correct for NGC 7020, then it has important implications for the nature of the outer ring. An alternative interpretation is that the inner hexagonal/X zone is a region where resonant periodic orbits in a weak bi-symmetric potential perturbation are influencing the morphology more strongly than might be expected. A brief summary of a more extensive paper (Buta 1990c = B90c) and a few other details concerning this interesting galaxy are given.
Document ID
19910007572
Document Type
Conference Paper
Authors
Buta, Ronald
(Alabama Univ. Tuscaloosa, AL, United States)
Date Acquired
September 6, 2013
Publication Date
November 1, 1990
Publication Information
Publication: NASA, Marshall Space Flight Center, Paired and Interacting Galaxies: International Astronomical Union Colloquium No. 124
Subject Category
Astrophysics
Accession Number
91N16885
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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