Astrometric Detection of Intermediate-Mass Black Holes At the Galactic Centre

Abstract

We assess the astrometric detectability of intermediate-mass black holes populating the inner parsec of the Milky Way Galaxy. The presence of these objects induces dynamical effects on Sgr A* and the star S2, which could be detected by next generation astrometric instruments that enable micro-arcsecond astrometry. An allowed population of ten $10^4{M}_{\odot }$ IMBHs within one parsec induces an angular shift of about 65 $\mu$as yr${}^{-1}$ on the position of Sgr A*, corresponding to a perpendicular velocity component magnitude of 1.6 km s${}^{-1}$. It also induces changes in the orbit of S2 that surpass those induced by general relativity but lie within observational constraints, generating a mean angular shift in periapse and apoapse of 62 $\mu$as and 970 $\mu$as respectively.

10 pages, 16 figures, 4 tables