Physical properties of the ionized gas and brightness distribution in NGC 4736^*

¹ Dep. de Astronomia, Instituto de Física, Universidade Federal do Rio Grande do Sul, CP. 15051, Porto Alegre, 91501-970, RS, Brazil 

² Departamento de Astrofísica, Facultad de Física, Universidad de La Laguna, E-38071 La Laguna, Tenerife, Spain
³ Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain e-mail: jcn@iac.es; jvm@iac.es

Send offprint request to: I. Rodrigues

Received: 16 September 1996
Accepted: 27 August 1997

Abstract

In this work we study the galaxy NGC 4736, using narrow band interference filters imaging centered at the emission lines , , , , and and nearby continua. We have obtained sizes, positions, emission line absolute fluxes, and continua intensities for 90  regions, mainly distributed in a ring-like structure of 3.2 kpc  in diameter. The  luminosities are in the range . The  regions size distribution presents a characteristic diameter and verifies the relation . The temperature of the ionizing sources and the metallicity of the  regions are respectively in the ranges K and . The masses of the ionizing clusters are in the range . 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.