Three-dimensional Analysis of the Minispiral at the Galactic Center: Orbital Parameters, Periods, and the Mass of the Black Hole

Abstract

Abstract In this paper we simultaneously fit the orbits and line-of-sight velocities of the ionized gas around the supermassive black hole, Sagittarius A* (Sgr A*), at the center of the Milky Way. The data we use are taken with the K-band Multi Object Spectrograph (KMOS), presented in Feldmeier-Krause et al., and cover the central ∼2 pc of the Milky Way. From the brightest gas emission line in the K-band, the Brγ line, we derive the spatial distribution and line-of-sight velocities of the gas in the minispiral. Using the flux distribution and the line-of-sight velocity information, we perform a fit to the three main gas streamers in the minispiral, the Northern Arm, Eastern Arm, and Western Arc, using a Bayesian modeling method, and are able to reconstruct the three-dimensional orbits of these gas streamers. With the best-fit orbital parameters and the measured line-of-sight velocities, we constrain the mass of Sgr A*. The orbit of the Eastern Arm is the one that is best constrained using our data. It gives a best-fit orbital period of yr and results in an enclosed mass of