Structure and kinematics of the Milky Way galaxy using atomic hydrogen

Abstract

Abstract The present study uses the hyper-fine transition of atomic hydrogen, HI (1420 MHz) to map the structure and kinematics of the Milky Way galaxy. The observation was carried out for galactic longitude 20° ≤ ℓ ≤ 220° and galactic latitude −20° ≤ b ≤ 20° each in 5° steps using the SALSA 2.3m Radio Telescope located at Onsala Space Observatory, Sweden. The velocity components of HI clouds were determined using Gaussian decomposition of the observed spectrum and these values were projected onto the Galactic plane for the identification of spiral structure of the galaxy. The Perseus, Local and Outer arms were identified using the Longitude velocity plots and x-y plots (face-on maps). The rotational velocities of the HI clouds were determined using the tangent-point method and the resulting rotation curve comes out to be consistent with the literature in the range 4 ≤ R ≤ 8 kpc.