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A Nuclear Ring in the Sa(r!) Galaxy NGC 7742

Published online by Cambridge University Press:  12 April 2016

K. Wakamatsu ,
M. Hamabe ,
M. T. Nishida  and
A. Tomita
K. Wakamatsu*
Affiliation:
Physics Department, Gifu University, Gifu 501-11, Japan
M. Hamabe
Affiliation:
Institute of Astronomy, The University of Tokyo, Mitaka 181, Japan
M. T. Nishida*
Affiliation:
Physics Department, Gifu University, Gifu 501-11, Japan
A. Tomita
Affiliation:
Department of Astronomy, Kyoto University, Kyoto 606, Japan
*
1Visiting Astronomer, Cerro Tololo Inter-American Observatory. CTIO is operated by AURA, Inc. under cooperative agreement with the National Science Foundation
1Visiting Astronomer, Cerro Tololo Inter-American Observatory. CTIO is operated by AURA, Inc. under cooperative agreement with the National Science Foundation

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NGC 7742 is well known for its prominent blue nuclear ring around an EO-like core, and so appears as a Hoag-type galaxy, an elliptical galaxy with an outer ring (Schweizer et al. 1987). The galaxy is classified as Sa(r!) in the Revised Shapley-Ames Catalog (Sandage and Tammann 1987) with an exclamation mark to emphasize the prominence of the ring. Its photographs are published in Laustsen et al. (1987), Wray (1988), and Sandage & Bedke (1994).

The ring has a diameter of 19″ = 1.6 kpc at a distance of 17.1 Mpc (Buta & Crocker 1993), and so should be a nuclear ring of the galaxy. Nuclear rings and pseudorings are often detected in strongly barred (SB) galaxies, and interpreted to be linked to the inner Lindblad resonance (Buta & Crocker 1993). These nuclear features are, however, also found in some weakly-barred (SAB) and non-barred (SA) galaxies. NGC 7742 is a galaxy of the highest circular symmetry in its core, ring, and main body, and so the best object for a detailed study of formation mechanisms of nuclear rings in non-barred galaxies.

Type
Part II. Observations of Barred Galaxies: Star Formation, IR Emission, Abundances
Information
International Astronomical Union Colloquium , Volume 157: Barred Galaxies , 1996 , pp. 83 - 85
Copyright
Copyright © Astronomical Society of the Pacific 1996

References

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