Extension of the C Star Rotation Curve of the Milky Way to 24 kpc

Demers and Battinelli published in 2007 the rotation curve of the Milky Way based on the radial velocity of carbon (C) stars outside the Solar circle. Since then we have established a new list of candidates for spectroscopy. The goal of this paper is to determine the rotation curve of the Galaxy, as far as possible from the Galactic center, using N-type C stars. The stars were selected from their dereddened 2MASS colors, then the spectra were obtained with the Dominion Astrophysical Observatory and Asiago 1.8 m telescopes. This publication adds radial velocities and Galactrocentric distances of 36 C stars, from which 20 are newly confirmed. The new results for stars up to 25 kpc from the Galactic center suggest that the rotation curve shows a slight decline beyond the Solar circle.