Ionized gas in the Sgr A complex -- VLA observations of H168α and H270α recombination lines

Abstract

Radio recombination lines at λ = 20 cm reveal the presence of an extended component of ionized gas of lower density (~100 cm3) in the Sgr A complex. This component extends well beyond the thermal `mini-spiral' Sgr A-West which seem to be embedded in it. The low-density component is present over the entire extent of Sgr A East and possibly beyond and it is responsible for the turnover in the spectrum of Sgr A East and the halo observed by Pedlar et al (1989) at λ = 90 cm. The radial velocity of the extended ionized gas ranges from +50 kms- to --200 kms- with minima of emission near --50 and --150 kms. The total mass of the low-density component is estimated to be ~104 Modot. A possible extended feature at a high velocity of 470 kms- is also detected, but needs further observations to confirm it.