Searching for Stellar Mass Black Holes in the Solar Neighborhood

We propose a strategy for searching for isolated stellar mass black holes inthe solar neighborhood with the Sloan Digital Sky Survey. Due to sphericalaccretion of the inter-stellar medium and the ambient magnetic field, anisolated black hole is expected to emit a blended, thermal synchrotron spectrumwith a roughly flat peak from the optical down to the far infra-red. We findthat the Sloan Survey will be able to detect isolated black holes, in theconsidered mass range of 1--100$M_{\odot}$, out to a few hundred parsecs,depending on the local conditions of the ISM. We also find that the black holesare photmetrically distinguishable from field stars and they have a photometrysimilar to QSOs. They can be further singled out from QSO searches because theyhave a featureless spectrum with no emission lines. The Sloan Survey willlikely find hundreds of objects that meet these criteria, and to further reducethe number of candidates, we suggest other selection criteria such as infra-redsearches and proper motion measurements. Estimates indicate that dozens ofblack holes may exist out to a few hundred parsecs. If no black hole candidatesare found in this survey, important limits can be placed on the local densityof black holes and the halo fraction in black holes, especially for massesgreater than about $20 M_{\odot}$.