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Date and Time of the Query: 2019-06-20 T02:49:29 PDT
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For refcode 1993ApJ...406...60R:
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Copyright by American Astronomical Society. Reproduced by permission
1993ApJ...406...60R THE IONIZED GAS IN THE CENTER AND IN THE BAR OF THE SPIRAL GALAXY NGC 6946 JEAN-RENE ROY Departement de Physique, and Observatoire du Mont Megantic, Universite Laval, Quebec, Que, Canada GIK 7P4 AND JULIEN BELLEY Centre Universitaire St-Louis-Maillet, Edmunston, NB, Canada E3V 258 Received 1992 May 4; accepted 1992 September 23 ABSTRACT Spectrophotometric data based on narrow-band images at H{alpha}, H{beta}, [O III] {lambda}5007 and [N II] {lambda}6584 for 189 H II regions in the spiral galaxy NGC 6946 are presented, with emphasis on the inner regions (R <= 2.5 kpc). The properties of the ionized gas are compared with those of the CO molecular bar. The possible influence of the bar on the ionized interstellar gas and star formation is discussed. The relatively high number of H II regions in the center is consistent with an enhancement of massive star formation as revealed by infrared and molecular observations the molecular gas bar in NGC 6946 is a favorable environment for massive star formation. The excitation and abundance indicators [O III] ({lambda}{lambda}5007 + 4959)/H{beta} and [N II] ({lambda}{lambda}6584 + 6548)/[O III] ({lambda}{lambda}5007+4959) show an unusual behavior as a function of galactocentric distances, and their radial trend is consistent with a flattening of the global O/H gradient in the inner regions of NGC 6946. This may be evidence of dilution by low-metallicity gas from outer regions due to strong radial flow along the molecular bar. Subject headings: galaxies: ISM galaxies: individual (NGC 6946) - galaxies: spiral - H II regions - ISM: abundances - ISM: molecules
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