336 research outputs found
Determination of Dark Energy by the Einstein Telescope: Comparing with CMB, BAO and SNIa Observations
A design study is currently in progress for a third generation
gravitational-wave (GW) detector called Einstein Telescope (ET). An important
kind of source for ET will be the inspiral and merger of binary neutron stars
(BNS) up to . If BNS mergers are the progenitors of short-hard
-ray bursts, then some fraction of them will be seen both
electromagnetically and through GW, so that the luminosity distance and the
redshift of the source can be determined separately. An important property of
these `standard sirens' is that they are \emph{self-calibrating}: the
luminosity distance can be inferred directly from the GW signal, with no need
for a cosmic distance ladder. Thus, standard sirens will provide a powerful
independent check of the CDM model. In previous work, estimates were
made of how well ET would be able to measure a subset of the cosmological
parameters (such as the dark energy parameter ) it will have access to,
assuming that the others had been determined to great accuracy by alternative
means. Here we perform a more careful analysis by explicitly using the
potential Planck CMB data as prior information for these other parameters. We
find that ET will be able to constrain and with accuracies and , respectively. These results are compared
with projected accuracies for the JDEM Baryon Acoustic Oscillations project and
the SNAP Type Ia supernovae observations.Comment: 28 pages, 5 figures, 5 tables; Published Versio
Gravitational wave astronomy and cosmology
The first direct observation of gravitational waves' action upon matter has
recently been reported by the BICEP2 experiment. Advanced ground-based
gravitational-wave detectors are being installed. They will soon be
commissioned, and then begin searches for high-frequency gravitational waves at
a sensitivity level that is widely expected to reach events involving compact
objects like stellar mass black holes and neutron stars. Pulsar timing arrays
continue to improve the bounds on gravitational waves at nanohertz frequencies,
and may detect a signal on roughly the same timescale as ground-based
detectors. The science case for space-based interferometers targeting
millihertz sources is very strong. The decade of gravitational-wave discovery
is poised to begin. In this writeup of a talk given at the 2013 TAUP
conference, we will briefly review the physics of gravitational waves and
gravitational-wave detectors, and then discuss the promise of these
measurements for making cosmological measurements in the near future.Comment: 11 pages. Proceedings writeup of a talk given at the 2013 Topics in
Astroparticle and Underground Physics (TAUP) conferenc
Gravitational waveforms from the inspiral of compact binaries in the Brans-Dicke theory in an expanding Universe
In modified gravity theories, such as the Brans-Dicke theory, the background
evolution of the Universe and the perturbation around it are different from
that in general relativity. Therefore, the gravitational waveforms used to
study standard sirens in these theories should be modified. The modifications
of the waveforms can be classified into two categories: wave generation effects
and wave propagation effects. Hitherto, the waveforms used to study standard
sirens in the modified gravity theories incorporate only the wave propagation
effects and ignore the wave generation effects; while the waveforms focusing on
the wave generation effects, such as the post-Newtonian waveforms, do not
incorporate the wave propagation effects and cannot be directly applied to the
sources with non-negligible redshifts in the study of standard sirens. In this
work, we construct the consistent waveforms for standard sirens in the
Brans-Dicke theory. The wave generation effects include the emission of the
scalar breathing polarization and the corrections to the tensor
polarizations and ; the wave propagation effect is the
modification of the luminosity distance for the gravitational waveforms. Using
the consistent waveforms, we analyze the parameter estimation biases due to the
ignorance of the wave generation effects. Considering the observations by the
Einstein Telescope, we find that the ratio of the theoretical bias to the
statistical error of the redshifted chirp mass is two orders of magnitude
larger than that of the source distance. For black hole-neutron star binary
systems like GW191219, the theoretical bias of the redshifted chirp mass can be
several times larger than the statistical error.Comment: 20 pages. Accepted for publication in PR
Measuring the Hubble Constant Near and Far in the Era of ELT's
Many of the fundamental physical constants in Physics, as a discipline, are
measured to exquisite levels of precision. The fundamental constants that
define Cosmology, however, are largely determined via a handful of independent
techniques that are applied to even fewer datasets. The history of the
measurement of the Hubble Constant (H0), which serves to anchor the expansion
history of the Universe to its current value, is an exemplar of the
difficulties of cosmological measurement; indeed, as we approach the centennial
of its first measurement, the quest for H0 still consumes a great number of
resources. In this white paper, we demonstrate how the approaching era of
Extremely Large Telescopes (ELTs) will transform the astrophysical measure of
H0 from the limited and few into a fundamentally new regime where (i) multiple,
independent techniques are employed with modest use of large aperture
facilities and (ii) 1% or better precision is readily attainable. This quantum
leap in how we approach H0 is due to the unparalleled sensitivity and spatial
resolution of ELT's and the ability to use integral field observations for
simultaneous spectroscopy and photometry, which together permit both familiar
and new techniques to effectively by-pass the conventional 'ladder' framework
to minimize total uncertainty. Three independent techniques are discussed --
(i) standard candles via a two-step distance ladder applied to metal, poor
stellar populations, (ii) standard clocks via gravitational lens cosmography,
and (iii) standard sirens via gravitational wave sources -- each of which can
reach 1% with relatively modest investment from 30-m class facilities.Comment: Submitted as an Astro2020 White Paper. Please send comments to both
Rachael Beaton & Simon Birrer. Development of this paper occurred as part of
the The US Extremely Large Telescope Program Workshop in Oct 2018. We wish to
acknowledge NOAO for bringing the co-authors together, in particular the
enthusiasm and tireless leadership of Mark Dickinso
Higher signal harmonics, LISA's angular resolution, and dark energy
It is generally believed that the angular resolution of the Laser
Interferometer Space Antenna (LISA) for binary supermassive black holes (SMBH)
will not be good enough to identify the host galaxy or galaxy cluster. This
conclusion, based on using only the dominant harmonic of the binary SMBH
signal, changes substantially when higher signal harmonics are included in
assessing the parameter estimation problem. We show that in a subset of the
source parameter space the angular resolution increases by more than a factor
of 10, thereby making it possible for LISA to identify the host galaxy/galaxy
cluster. Thus, LISA's observation of certain binary SMBH coalescence events
could constrain the dark energy equation of state to within a few percent,
comparable to the level expected from other dark energy missions.Comment: 15 pages, no figures. Final version to appear in Phys. Rev.
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