The Eighty Six H alpha Spectra from the Orion Nebula (M42, Sh2-281) with DEFPOS

Abstract

In this study, eighty six H alpha (6563 angstrom) emission line spectra from the central region (similar to 40' x 40') of the Orion Nebula (NGC1976, M42, Sh2-281) have been obtained using DEFPOS spectrometer with a circular field of view of 4' at TUBITAK National Observatory (TUG, Antalya, Turkey). Measurements provide information about the intensities, line widths, and radial velocities of the gas surrounding the Sh2-281 HII-region. The intensities, the radial velocities and the line widths of the Ha emission line were found in the range of from 319.85 R to 6009.08 R (mean 2006 +/- 400 R), from -14.91 km s(-1) to +5.40 km s(-1) (mean -4.51 +/- 3.80 km s(-1)), and from 27.83 km s(-1) to 49.60 km s(-1) (mean 41.09 +/- 7.74 km s(-1)), respectively. Moreover, the mean emission measure (EM) calculated from I-H alpha values was obtained as 4513.02 cm(-6) pc. The mean LSR velocity of the nebula was found to be -4.51 km s(-1) and was compared with some previous works. The intensity values of DEFPOS data were also compared with the data obtained from VTSS, SkyView, and SHASSA maps using APER and SKY codes. We found that our results were approximately the similar variation with VTSS (mean 2002.04 R), SkyView (mean 2680.05 R), and SHASSA (mean 2400.06 R) maps. We believe that DEFPOS spectrometer with a 4' diameter field of view is able to provide a powerful tool for the study of diffuse ionized gas and this new results may have significant contribution to the literature.