The mass distribution and the rotation curve of the Milky Way Galaxy using NARIT 4.5 m small radio telescope and the 2.3 m Onsala radio telescope

Abstract

This study was aimed to make the neutral hydrogen (HI) mapping and rotation curve of the Milky Way at galactic longitude 0° to 90° in the galactic plane by using the 4.5 m Small Radio Telescope (SRT) of National Astronomical Research Institute of Thailand (NARIT) and the 2.3 m Onsala radio telescope. The HI spectra at wavelength of 21 cm can be used to analyze the dynamical properties of the Milky Way with Gaussian fitting software, which was developed by using Python programming language. SalsaJ is another free astronomical software which was also used in this study by analyzing the Gaussian spectra of the Onsala radio telescope. For making sure the performance of developed software, therefore, it will be tested between their observation spectra of NARIT 4.5 m SRT and the Onsala radio telescope together with the public international archive. The results showed that the positions of HI are distributed in a spiral - arms shape and the rotation curve is constant at the galactic distance (R) > 3 kpc. The spherical mass distribution (in terms of the surface mass density) was approximated by directly using rotation curve. Our results are in good agreement with the standard values.