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A&A Supplement series, Vol. 128, March II 1998, 545-560

Received September 16, 1996; accepted August 27, 1997

Physical properties of the ionized gas and brightness distribution in NGC4736gif

I. Rodriguestex2html_wrap2580,gif - H. Dottoritex2html_wrap2580 - J. Cepatex2html_wrap2584gif - J. Vilcheztex2html_wrap2586,gif

Send offprint request: I. Rodrigues

tex2html_wrap2588  Dep. de Astronomia, Instituto de Fı sica, Universidade Federal do Rio Grande do Sul, CP. 15051, Porto Alegre, 91501-970, RS, Brazil
tex2html_wrap2590  Departamento de Astrofísica, Facultad de Física, Universidad de La Laguna, E-38071 La Laguna, Tenerife, Spain
tex2html_wrap2592  Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife, Spain


In this work we study the galaxy NGC4736, using narrow band interference filters imaging centered at the emission lines [OII]tex2html_wrap_inline2542, Htex2html_wrap_inline2544 , [OIII]tex2html_wrap_inline2546, Htex2html_wrap_inline2548 , [SII]tex2html_wrap_inline2550 and [SIII]tex2html_wrap_inline2552 and nearby continua. We have obtained sizes, positions, emission line absolute fluxes, and continua intensities for 90 HII regions, mainly distributed in a ring-like structure of 3.2kpc in diameter. The Htex2html_wrap_inline2548 luminosities are in the range tex2html_wrap_inline2556. The HII regions size distribution presents a characteristic diameter tex2html_wrap_inline2558 and verifies the relation tex2html_wrap_inline2560. The temperature of the ionizing sources and the metallicity of the HII regions are respectively in the ranges tex2html_wrap_inline2562K and tex2html_wrap_inline2564. The masses of the ionizing clusters are in the range tex2html_wrap_inline2566. The continua radial surface brightness distribution is better fitted by the superposition of a de Vaucouleurs', a thin and a thick exponential disk laws. The monochromatic colors show that outside the star forming ring the disk presents a younger stellar population than inside it.

keywords: galaxies: individual: NGC4736 -- galaxies: abundances -- galaxies: ISM -- galaxies: spiral -- galaxies: structure

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