Broad search for gravitational waves from subsolar-mass binaries through LIGO and Virgo’s third observing run

We present a search for gravitational waves from the coalescence of binaries which contain at least one subsolar-mass component using data from the LIGO and Virgo observatories through the completion of their third observing run. The observation of a merger with a component below 1 M_ would be a clear sign of either new physics or the existence of a primordial black hole population; these black holes could also contribute to the dark matter distribution. Our search targets binaries where the primary has mass M₁ between 0. 1 and 100 M_ and the secondary has mass M₂ from 0. 1 to 1 M_ for M₁0. 5 M_ are also allowed to have orbital eccentricity up to e₁₀0. 3. This search region covers from comparable to extreme mass ratio sources up to 10^4: 1. We find no statistically convincing candidates and so place new upper limits on the rate of mergers; our analysis sets the first limits for most subsolar sources with 7M_20 M_ (M₁<7 M_). Using these limits, we constrain the dark matter fraction to below 0. 3 (0. 7) % for 1 (0. 5) M_ black holes assuming a monochromatic mass function. Due to the high merger rate of primordial black holes beyond the individual source horizon distance, we also use the lack of an observed stochastic background as a complementary probe to limit the dark matter fraction. We find that although the limits are, in general, weaker than those from the direct search, they become comparable at 0. 1 M_.