Mapa de densidade eletrônica da região HII RCW 71

Abstract

The goal of this work is to determine spatial variations of the electron density (n e ) of the HII Region RCW 71 through the ratio of the forbidden lines of the once-ionized sulfur [S II] λλ6716, 6731. Moreover, we aim to build a map to describe these variations. Point-to-point measurements of the electron density in photoionized nebulae are important to verify fluctuations of this parameter within a given region. A previous work about RCW 71 indicated large variations in the electron density of this object. The data were obtained at the Pico dos Dias Observatory (OPD), at Brasópolis - MG, using the Cassegrain spectrograph installed on the 1.6-m diameter telescope. Over the RCW 71 Region, 20 long slits, each with a 5" width, were positioned along the East-West direction, covering a range of 50" S to 45" N across the nebula. The reference slit (0") was positioned on the ionizing source of RCW 71. The data reduction followed the standard procedures using IRAF: bias and flat-field corrections, cosmic ray removal, and extraction of the one-dimensional spectra. The line profiles were fitted with a Gaussian function, and the electron densities were calculated using the equation proposed by Proxauf et al. (2014). Electron density fluctuations were detected throughout the RCW 71 region, with typical values for an HII Region. It is possible to identify the presence of one element that is blocking the expansion of the ionized gas in some directions, since large density variations are seen in such regions. The existence of density fluctuations in RCW 71 indicates that average values, in general, are not adequate to study the physical and chemical properties of an HII region.