New structures near the compact radio source at the Galactic Centre

Sixteen years ago, a bright compact radio source, Sgr A*, was found at the Galactic Centre, as had been predicted. The characteristics of its emission and the kinematics of gas near it have been used to argue for the presence of a black hole of 500-5 x 106 solar masses at the Galactic Centre. Here we present high-resolution (<0.2 arcsec) radio images, made at 2-cm wavelength, of the central arcsecond of the Galaxy. Sgr A* is surrounded by at least four satellite radio features. Interpreted as thermally emitting blobs of plasma, they have typical sizes <1,700 AU and are within a projected distance of 3,500 AU from Sgr A*. Another set of larger radio features, 2-4 arcsec from Sgr A*, shows a regular progression of galactocentric distance with position angle. The placement and appearance of all these structures lead us to suggest that they are physically associated with Sgr A*; if so, they can be used as probes of the immediate vicinity of the possible massive black hole at the Galactic Centre. (author)