A photometric study of the double ring structure of NGC 4736

Munoz-Tunon, C.; Prieto, M.; Beckman, J.; Cepa, J.
Bibliographical reference

(Instituto de Astrofisica de Canarias and Comision Interministerial de Ciencia y Tecnologia, Summer School on Evolutionary Phenomena in Galaxies, Puerto de la Cruz, Spain, July 4-15, 1988) Astrophysics and Space Science (ISSN 0004-640X), vol. 156, no. 1-2, June 1989, p. 301-313.

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Photometric results for the galaxy NGC 4736 are presented, including IR and visible profiles. After correction for the extinction within the galaxy based on measured neutral gas surface densities, the profiles in the individual bands and in color indices are interpreted in terms of the radial distribution of stellar populations. The behavior of the two rings, an inner ring some 40-50 arc sec from the nucleus, and an outer ring some 300 arc sec away, are examined. The results suggest that the inner ring is connected with an outflow of gas observed via its H II regions, and is probably the result of an axisymmetric starburst, while the outer ring is a site of star formation which appears to be further from the center than the typical resonant structures associated with a density wave.