Population Synthesis of Black Hole Binaries with Normal-Star Companions:
  I. Detached Systems
  Optical observations of normal-stars in binary systems with massive unseen
objects have been proposed to search for candidate black holes (BHs) and
provide a direct measurement of their dynamical masses. In this paper, we have
performed binary population synthesis calculations to simulate the potential
population of detached binaries containing BHs and normal-star companions in
the Galaxy. We focus on the influence of the BH progenitors. In the traditional
model, BHs in binaries evolve from stars more massive than $ \sim25M_{\odot} $.
However, it is difficult for this model to produce BH low-mass X-ray binaries.
Recent investigations on massive star evolution suggest that the BH progenitors
may have masses as low as $ \sim15M_{\odot} $. Based on this model, we provide
the expected distributions of various parameters for detached BH binaries with
normal-star companions, including the component masses, the orbital parameters
of the binary systems, the radial velocity semi-amplitudes, and the astrometric
signatures of the optical companions. %the detached BH systems with low-mass
companions can be easily produced in our simulations. Our calculations show
that there are more than thousands of such detached binaries in the Galaxy, and
hundreds of them are potentially observable systems with luminous companions
brighter than 20 mag. In addition, detached BH binaries are dominated by those
with main-sequence companions and only a few percent of them are expected to
have giant companions.
