Can the Density Distribution and Shape of the Galactic Dark Halo Be Determined by Low-Frequency Gravitational Waves?

摘要

Under the assumption that the Milky Way's dark halo consists of primordial black hole MACHOs (PBH MACHOs), the mass density of the halo can be measured by the low-frequency gravitational waves (10-3 νgw 10-1 Hz) from PBH MACHO binaries whose fraction is ~10-6. We find that 10 yr of observations by the Laser Interferometer Space Antenna (LISA) should detect ~700 PBH MACHO binaries and enable us to determine the power index of the density profile within 10% (20%) and the core radius within 25% (50%) at about a 90% (99%) confidence level, respectively. The axial ratios of the halo may also be determined within ~10%. LISA and the Orbiting Medium Explorer for Gravitational Astrophysics (OMEGA) may give us a unique observational method to determine the density profile and the shape of the dark halo to open a new field of observational astronomy.