  Starting from the evidence that dark matter indeed exists and permeates the
entire cosmos, various bounds on its properties can be estimated. Beginning
with the cosmic microwave background and large scale structure, we summarize
bounds on the ultralight bosonic dark matter (UBDM) mass and cosmic density.
These bounds are extended to larger masses by considering galaxy formation and
evolution, and the phenomenon of black hole superradiance. We then discuss the
formation of different classes of UBDM compact objects including solitons/axion
stars and miniclusters. Next, we consider astrophysical constraints on the
couplings of UBDM to Standard Model particles, from stellar cooling (production
of UBDM) and indirect searches (decays or conversion of UBDM). Throughout,
there are short discussions of "hints and opportunities" in searching for UBDM
in each area.
