Search for Subsolar-Mass Binaries in the First Half of Advanced LIGO’s and Advanced Virgo’s Third Observing Run

We report on a search for compact binary coalescences where at least one binary component has a mass between $0.2M_{\odot }$ and $1.0M_{\odot }$ in Advanced LIGO and Advanced Virgo data collected between 1 April 2019 1500 UTC and 1 October 2019 1500 UTC. We extend our previous analyses in two main ways: we include data from the Virgo detector and we allow for more unequal mass systems, with mass ratio $q\ge 0.1$. We do not report any gravitational-wave candidates. The most significant trigger has a false alarm rate of $0.14{\mathrm{yr}}^{-1}$. This implies an upper limit on the merger rate of subsolar binaries in the range $[220-24200]{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$, depending on the chirp mass of the binary. We use this upper limit to derive astrophysical constraints on two phenomenological models that could produce subsolar-mass compact objects. One is an isotropic distribution of equal-mass primordial black holes. Using this model, we find that the fraction of dark matter in primordial black holes in the mass range $0.2M_{\odot }<m_{\mathrm{PBH}}<1.0M_{\odot }$ is $f_{\mathrm{PBH}}\equiv {\mathrm{\Omega }}_{\mathrm{PBH}}/{\mathrm{\Omega }}_{\mathrm{DM}}\lesssim 6\%$. This improves existing constraints on primordial black hole abundance by a factor of $\sim 3$. The other is a dissipative dark matter model, in which fermionic dark matter can collapse and form black holes. The upper limit on the fraction of dark matter black holes depends on the minimum mass of the black holes that can be formed: the most constraining result is obtained at $M_{\min }=1M_{\odot }$, where $f_{\mathrm{DBH}}\equiv {\mathrm{\Omega }}_{\mathrm{DBH}}/{\mathrm{\Omega }}_{\mathrm{DM}}\lesssim 0.003\%$. These are the first constraints placed on dissipative dark models by subsolar-mass analyses.

Figure 1

Upper limit on the merger rate of binaries with at least one SSM component as a function of source frame chirp mass. The dotted, dashed, and solid lines represent the 90% confidence limits obtained by gstlal, mbta, and pycbc, respectively.

Figure 2

Constraints on the fraction of dark matter in PBHs. The horizontal axis shows the source frame mass of the black hole in each model; for LVK results this is the component mass for each object in the binary. Each constraint shown carries a model dependency. Shown (pink) are the LVK results from O1 [98], O2 [99], and O3a (this work); (orange) microlensing constraints from MACHO [155], EROS [156], and OGLE [157]; (green) dynamical constraints from observations of Segue I [158] and Eridanus II [159] dwarf galaxies; (blue) supernova lensing constraints from the Joint Light-curve Analysis and Union 2.1 datasets [160]. LVK results use the Planck “$\mathrm{TT},\mathrm{TE},\mathrm{EE}+\mathrm{lowP}+\text{lensing}+\mathrm{ext}$” cosmology [142].

Figure 3

Constraints on the fraction of dark matter $f_{\mathrm{DBH}}$ in black holes formed from cooling of dissipative dark matter and their minimum possible source frame mass $M_{\min }$.