Limits on stellar-mass compact objects as dark matter from gravitational
  lensing of type Ia supernovae
  The nature of dark matter (DM) remains unknown despite very precise knowledge
of its abundance in the universe. An alternative to new elementary particles
postulates DM as made of macroscopic compact halo objects (MACHO) such as black
holes formed in the very early universe. Stellar-mass primordial black holes
(PBHs) are subject to less robust constraints than other mass ranges and might
be connected to gravitational-wave signals detected by the Laser Interferometer
Gravitational-Wave Observatory (LIGO). New methods are therefore necessary to
constrain the viability of compact objects as a DM candidate. Here we report
bounds on the abundance of compact objects from gravitational lensing of type
Ia supernovae (SNe). Current SNe datasets constrain compact objects to
represent less than 35.2% (Joint Lightcurve Analisis) and 37.2% (Union 2.1) of
the total matter content in the universe, at 95% confidence-level. The results
are valid for masses larger than $\sim 0.01M_\odot$ (solar-masses), limited by
the size SNe relative to the lens Einstein radius. We demonstrate the mass
range of the constraints by computing magnification probabilities for realistic
SNe sizes and different values of the PBH mass. Our bounds are sensitive to the
total abundance of compact objects with $M \lesssim 0.01M_\odot$ and
complementary to other observational tests. These results are robust against
cosmological parameters, outlier rejection, correlated noise and selection
bias. PBHs and other MACHOs are therefore ruled out as the dominant form of DM
for objects associated to LIGO gravitational wave detections. These bounds
constrain early-universe models that predict stellar-mass PBH production and
strengthen the case for lighter forms of DM, including new elementary
particles.
