Radio Emission on Sub-Parsec Scales from the Intermediate-Mass Black Hole in NGC 4395

Abstract

The Seyfert 1 nucleus of NGC 4395 is energized by a black hole of 360,000 Solar masses (Peterson et al.), making it one of only two nuclear black holes of intermediate mass, one thousand to one million Solar masses, detected in the radio regime. Building upon UV and X-ray evidence for outflows from this Seyfert nucleus, the VLBI High Sensitivity Array was used at 1.4 GHz to search for extended structure on scales greater than 5 mas (0.1 pc). Elongated emission was discovered, extending over 15 mas (0.3 pc) and suggesting an outflow on sub-parsec scales from this intermediate-mass black hole. The Seyfert nucleus is located at the center of an elliptical star cluster, and the elongation position angle of the sub-parsec radio structure is only 19 degrees from the star cluster's minor axis.