46 research outputs found
Localizing merging black holes with sub-arcsecond precision using gravitational-wave lensing
The current gravitational-wave localization methods rely mainly on sources
with electromagnetic counterparts. Unfortunately, a binary black hole does not
emit light. Due to this, it is generally not possible to localize these objects
precisely. However, strongly lensed gravitational waves, which are forecasted
in this decade, could allow us to localize the binary by locating its lensed
host galaxy. Identifying the correct host galaxy is challenging because there
are hundreds to thousands of other lensed galaxies within the sky area spanned
by the gravitational-wave observation. However, we can constrain the lensing
galaxy's physical properties through both gravitational-wave and
electromagnetic observations. We show that these simultaneous constraints allow
one to localize quadruply lensed waves to one or at most a few galaxies with
the LIGO/Virgo/Kagra network in typical scenarios. Once we identify the host,
we can localize the binary to two sub-arcsec regions within the host galaxy.
Moreover, we demonstrate how to use the system to measure the Hubble constant
as a proof-of-principle application.Comment: 5 pages (main text) + 5 pages (methods+references), 5 figures.
Accepted to MNRA
lensingGW: a Python package for lensing of gravitational waves
Advanced LIGO and Advanced Virgo could observe the first lensed gravitational
waves in the coming years, while the future Einstein Telescope could observe
hundreds of lensed events. Ground-based gravitational-wave detectors can
resolve arrival time differences of the order of the inverse of the observed
frequencies. As LIGO/Virgo frequency band spans from a few to a few , the typical time resolution of current interferometers is of the
order of milliseconds. When microlenses are embedded in galaxies or galaxy
clusters, lensing can become more prominent and result in observable time
delays at LIGO/Virgo frequencies. Therefore, gravitational waves could offer an
exciting alternative probe of microlensing. However, currently, only a few
lensing configurations have been worked out in the context of
gravitational-wave lensing. In this paper, we present lensingGW, a Python
package designed to handle both strong and microlensing of compact binaries and
the related gravitational-wave signals. This synergy paves the way for
systematic parameter space investigations and the detection of arbitrary lens
configurations and compact sources. We demonstrate the working mechanism of
lensingGW and its use to study microlenses embedded in galaxies.Comment: 11 pages, 10 figure
A fast and precise methodology to search for and analyse strongly lensed gravitational-wave events
Gravitational waves, like light, can be gravitationally lensed by massive
astrophysical objects such as galaxies and galaxy clusters. Strong
gravitational-wave lensing, forecasted at a reasonable rate in ground-based
gravitational-wave detectors such as Advanced LIGO, Advanced Virgo, and KAGRA,
produces multiple images separated in time by minutes to months. These images
appear as repeated events in the detectors: gravitational-wave pairs, triplets,
or quadruplets with identical frequency evolution originating from the same sky
location. To search for these images, we need to, in principle, analyze all
viable combinations of individual events present in the gravitational-wave
catalogs. An increasingly pressing problem is that the number of candidate
pairs that we need to analyse grows rapidly with the increasing number of
single-event detections. At design sensitivity, one may have as many as
event pairs to consider. To meet the ever-increasing
computational requirements, we develop a fast and precise Bayesian methodology
to analyse strongly lensed event pairs, enabling future searches. The
methodology works by replacing the prior used in the analysis of one strongly
lensed gravitational-wave image by the posterior of another image; the
computation is then further sped up by a pre-computed lookup table. We
demonstrate how the methodology can be applied to any number of lensed images,
enabling fast studies of strongly lensed quadruplets.Comment: 10 pages, 6 figure
Extreme Dark Matter Tests with Extreme Mass Ratio Inspirals
Future space-based laser interferometry experiments such as LISA are expected
to detect (100--1000) stellar-mass compact objects (e.g., black holes,
neutron stars) falling into massive black holes in the centers of galaxies, the
so-called extreme-mass-ratio inspirals (EMRIs). If dark matter forms a "spike"
due to the growth of the massive black hole, it will induce a gravitational
drag on the inspiraling object, changing its orbit and gravitational-wave
signal. We show that detection of even a single dark matter spike from the
EMRIs will severely constrain several popular dark matter candidates, such as
ultralight bosons, keV fermions, MeV--TeV self-annihilating dark matter, and
sub-solar mass primordial black holes, as these candidates would flatten the
spikes through various mechanisms. Future space gravitational wave experiments
could thus have a significant impact on the particle identification of dark
matter.Comment: 10 pages (main body: 5 pages), 2 figure
The return of GOLUM : improving distributed joint parameter estimation for strongly lensed gravitational waves
Owing to the forecasted improved sensitivity of ground-based gravitational-wave detectors, new research avenues will become accessible. This is the case for gravitational-wave strong lensing, predicted with a non-negligible observation rate in the coming years. However, because one needs to investigate all the event pairs in the data, searches for strongly lensed gravitational waves are often computationally heavy, and one faces high false-alarm rates. In this paper, we present upgrades made to the GOLUM software, making it more reliable while increasing its speed by re-casting the look-up table, imposing a sample control, and implementing symmetric runs on the two lensed images. We show how the recovered posteriors have improved coverage of the parameter space and how we increase the pipeline’s stability. Finally, we show the results obtained by performing a joint analysis of all the events reported until the GWTC-3 catalogue, finding similar conclusions to the ones presented in the literature
Reducing the Impact of Weak-lensing Errors on Gravitational-wave Standard Sirens
The mergers of supermassive black hole binaries (SMBHBs) can serve as
standard sirens: the gravitational wave (GW) analog of standard candles. The
upcoming space-borne GW detectors will be able to discover such systems and
estimate their luminosity distances precisely. Unfortunately, weak
gravitational lensing can induce significant errors in the measured distance of
these standard sirens at high redshift, severely limiting their usefulness as
precise distance probes. The uncertainty due to weak lensing can be reduced if
the lensing magnification of the siren can be estimated independently, a
procedure called 'delensing'. With the help of up-to-date numerical
simulations, here we investigate how much the weak-lensing errors can be
reduced using convergence maps reconstructed from shear measurements. We also
evaluate the impact of delensing on cosmological parameter estimation with
bright standard sirens. We find that the weak-lensing errors for sirens at can be reduced by about a factor of two on average, but to achieve this
would require expensive ultra-deep field observations for every siren. Such an
approach is likely to be practical in only limited cases, and the reduction in
the weak-lensing error is therefore likely to be insufficient to significantly
improve the cosmological parameter estimation. We conclude that performing
delensing corrections is unlikely to be worthwhile, in contrast to the more
positive expectations presented in previous studies. For delensing to become
more practicable and useful in the future will require significant improvements
in the resolution/depth of the weak-lensing surveys themselves and/or the
accuracy of the methods to reconstruct convergence maps from these surveys.Comment: 19 pages, 22 figures, preparing for submitting to MNRA
Searching for ultralight bosons within spin measurements of a population of binary black hole mergers
Ultralight bosons can form clouds around rotating black holes if their
Compton wavelength is comparable to the black hole size. The boson cloud spins
down the black hole through a process called superradiance, lowering the black
hole spin to a characteristic value. It has been suggested that spin
measurements of the black holes detected by ground-based gravitational-wave
detectors can be used to constrain the mass of ultralight bosons.
Unfortunately, a measurement of the \emph{individual} black hole spins is often
uncertain, resulting in inconclusive results. Instead, we use hierarchical
Bayesian inference to \emph{combine} information from multiple
gravitational-wave sources and obtain stronger constraints. We show that
hundreds of high signal-to-noise ratio gravitational-wave detections are enough
to exclude (confirm) the existence of non-interacting bosons in the mass range
~eV
. The precise number depends on the
distribution of black hole spins at formation and the mass of the boson. From
the few uninformative spin measurements of binary black hole mergers detected
by LIGO and Virgo in their first two observing runs, we cannot draw
statistically significant conclusions.Comment: 10 pages, 4 figures, revised version after resubmissio
Lensed or not lensed: Determining lensing magnifications for binary neutron star mergers from a single detection
Advanced LIGO and Advanced Virgo could observe the first lensed gravitational
wave sources in the coming years, while the future Einstein Telescope could
observe hundreds of lensed events. It is, therefore, crucial to develop
methodologies to distinguish between lensed from unlensed gravitational-wave
observations. A lensed signal not identified as such will lead to biases during
the interpretation of the source. In particular, sources will appear to have
intrinsically higher masses. No robust method currently exists to distinguish
between the magnification bias caused by lensing and intrinsically high-mass
sources. In this work, we show how to recognize lensed and unlensed binary
neutron star systems through the measurement of their tidal effects for highly
magnified sources as a proof-of-principle. The proposed method could be used to
identify lensed binary neutron stars, which are the chief candidate for lensing
cosmography studies. We apply our method on GW190425, finding no evidence in
favor of lensing, mainly due to the poor measurement of the event's tidal
effects. However, we expect that future detections with better tidal
measurements can yield better constraints.Comment: 12 pages, 7 figure
Beyond the Detector Horizon:Forecasting Gravitational-Wave Strong Lensing
When gravitational waves pass near massive astrophysical objects, they can be
gravitationally lensed. The lensing can split them into multiple wave-fronts,
magnify them, or imprint beating patterns on the waves. Here we focus on the
multiple images produced by strong lensing. In particular, we investigate
strong lensing forecasts, the rate of lensing, and the role of lensing
statistics in strong lensing searches. Overall, we find a reasonable rate of
lensed detections for double, triple, and quadruple images at the
LIGO--Virgo--KAGRA design sensitivity. We also report the rates for A+ and LIGO
Voyager and briefly comment on potential improvements due to the inclusion of
sub-threshold triggers. We find that most galaxy-lensed events originate from
redshifts and report the expected distribution of lensing
parameters for the observed events. Besides forecasts, we investigate the role
of lensing forecasts in strong lensing searches, which explore repeated event
pairs. One problem associated with the searches is the rising number of event
pairs, which leads to a rapidly increasing false alarm probability. We show how
knowledge of the expected galaxy lensing time delays in our searches allow us
to tackle this problem. Once the time delays are included, the false alarm
probability increases linearly (similar to non-lensed searches) instead of
quadratically with time, significantly improving the search. For galaxy cluster
lenses, the improvement is less significant. The main uncertainty associated
with these forecasts are the merger-rate density estimates at high redshift,
which may be better resolved in the future