Mapas de densidade e velocidade e estimativa de distância da região H II galáctica NGC 2579

Abstract

An observational study was accomplished about the range of eletron density in the HIIregion NGC 2579 and estimate its distance from the 8un and from the centre of the Galaxy. Long slit spectrophotometric data with high noise signal in the 6000 to 7000 Á were obtained by using the 1.60 m telescope of the Laboratório Nacional de Astrofísica LNA), MG. We observed the Hllregion at 15 distinct positions in the direetion North-8outh; the distance among the slit's positions was 5", the size of the slit was 5.63' and its orientation-was East-West. Photometry was used in the BVR filters on 0.60 m telescope of the LNA, and the U and nebulars filters, centred in HQ and 6450 Á on 1.50 telescope of the Observatório Astronômico Nacional, 8an Pedro Mártir, México. Unidimendionals spectra were extracted by each bidimensional speetrum with sectors of size 5" in the direction East- West. The electron density was estimate by [811] ()'6716 / ),6731) line ratio, which showed a variation from 1 900 em -3, in eenter of the H 11 region, to 70 cm -3, in the edge of the nebula. Through the data obtained, it was possible to build a eletron density map, with space resolution of 5" x 5", it suggesting a strong gradient of eletron density, characterized as the ehampange effect in the H 11 region NGC 2579. An HQ map was built and, throught the shift owing to Doppler effect, it was possible to compute the velocity in each point over NGC 2579 and build a radial velocity map, both have a space resolution of 5" x 5". An additional result showed that the Hllregion NGC 2579 is formed by two ionized gas mass, one more bright central nebulosity and a nebulosity with less brightness at southeast of the first. In the photometry, we found the visual aparent magnitude (V) and the colors (U-B) and (B- V) for the ionizing stars of the nebula. Finally, we used three differents methods to compute the distance of the H 11 region. We found the heliocentric distance ranging from 7.11 to 10.53 kpc, and the distance from the Galactic center ranging from 12.44 to 15.18 kpc depending on the methods used.