Schedule Aug 03, 2012
Cosmology Without EM Counterparts: Standard Sirens in the Advanced Era and Beyond
Stephen Taylor (Univ. Cambridge)

The era of advanced ground-based gravitational-wave (GW) detectors is approaching. By the end of this decade we will have a global network of instruments capable of making detections of inspiraling double neutron-star binary systems out to an average luminosity distance of ~200 Mpc. These systems are self-calibrating standard sirens, with the luminosity distance encoded in the amplitude of the waveform and measurable by interferometer-network triangulation. To extract cosmological parameters from these detections, we need a measure of the source redshift. Whilst electromagnetic (EM) counterparts (in the form of short-duration gamma-ray bursts, or host galaxy identification) can give us redshift measurements, the fraction of GW-events with which we can associate an EM signal is likely to be <10%. We perform an analysis of mock catalogs of DNS inspiral detections using only GW information. The best-determined parameter is likely to be the redshifted chirp mass. Recent analysis of Galactic DNS systems indicates the mass distribution of NS's in these systems is narrow (~0.06 solar masses, centered around ~1.35 solar masses). Hence we already have a good idea of what the masses in these systems will be, allowing us to extract candidate redshift distributions from the redshifted chirp mass, and compare with the measured distance to deduce the Hubble constant to ~20%. This method provides complementary constraints on cosmological parameters, being independent of the local distance ladder, and can be extended to constrain the astrophysical distribution of these systems, and to future proposed detectors such as the Einstein Telescope.

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