Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session V09: Gravitational Wave Lensing and Cosmology |
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Sponsoring Units: DGRAV Chair: Amanda Farah, University of Chicago Room: Conrad B/C - 2nd Floor |
Tuesday, April 18, 2023 3:45PM - 3:57PM |
V09.00001: Search for gravitational-lensing signatures in the full third observing run of the LIGO–Virgo network Justin Janquart Gravitational lensing by massive objects in between the source and observer leads to distortions to gravitational-wave signals that may reveal additional information about fundamental physics, cosmology, and astrophysics. In this work, we have extended the search for lensing signatures to all black hole binary events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap between the intrinsic parameters and sky location, 3) comparing the similarities of the spectrograms, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to study the lensing rate based on the latest merger-rate estimates and set constraints on the dark matter fraction of (dark) compact objects. |
Tuesday, April 18, 2023 3:57PM - 4:09PM |
V09.00002: Observability of lensing of gravitational waves from massive black hole binaries with Laser Interferometer Space Antenna Mesut Çaliskan, Lingyuan Ji, Roberto Cotesta, Emanuele Berti, Marc P Kamionkowski, Sylvain Marsat The gravitational waves emitted by massive black hole binaries in the LISA band can be lensed. Wave-optics effects in the lensed signal are crucial when the Schwarzschild radius of the lens is smaller than the wavelength of the radiation. These frequency-dependent effects can enable us to infer the lens parameters, possibly with a single detection alone. In this work, we assess the observability of wave-optics effects with LISA by performing an information-matrix analysis using analytical solutions for both point-mass and singular isothermal sphere lenses. We use gravitational-waveform models that include the merger, ringdown, higher harmonics, and aligned spins to study how waveform models and source parameters affect the measurement errors in the lens parameters. We find that previous work underestimated the observability of wave-optics effects and that LISA can detect lensed signals with higher impact parameters and lower lens masses. Comparing lens populations obtained from the Press-Schechter mass function and the measured velocity function based on the SDSS, we find that the probability of observing wave-optics effects is highly sensitive to the abundance of low-mass lenses such as late-type galaxies and sub-halos and that this probability can be significantly higher than the probability of observing strong lensing. |
Tuesday, April 18, 2023 4:09PM - 4:21PM |
V09.00003: An effective method to search for sub-threshold lensed gravitational waves with a targeted population model Alvin Ka Yue Li, Heather Kin Yee Fong, Juno Chun Lung Chan Strong gravitational lensing of gravitation waves (GW) from the same source can produce identical signals (with the same intrinsic parameters, e.g., masses and spins) with varying amplitudes and arrival times. One scenario is when some signals are magnified that are strong enough to be identified as GWs (super-threshold), and some are demagnified and buried in the noise, remaining unidentified (sub-threshold). There have been efforts that assume confirmed GWs as strongly lensed signals and attempt to search for their sub-threshold lensed counterparts. As LVK detectors' sensitivities improve, we expect to observe more super-threshold GWs in upcoming observing runs. We present an effective method built based on the traditional targeted search method to search for possible sub-threshold lensed GWs for a given target event efficiently, with a targeted population model created based on the component-mass posterior distribution of the target. Without additional re-filtering, the likelihood of being a real GW is re-evaluated for each candidate from the general search for GWs using the targeted population model. Candidates with masses similar to the target will be up-ranked, and those that are not will be down-ranked. Candidates in the reranked list with ranking statistics passing a given threshold will then be identified as possible lensed counterparts and followed up with other analyses to determine how likely they are lensed counterparts to the given target. This method will be applied in future LVK collaboration-wide lensing analyses. |
Tuesday, April 18, 2023 4:21PM - 4:33PM |
V09.00004: Gravitational-wave millilensing as a probe of dark matter substructures Anna Liu, Isaac C. F. Wong, Samson H. W. Leong, Anupreeta More, Otto A Hannuksela, Tjonnie Li Gravitational waves will bring forth an altogether new way to probe millilensing, which may allow us to probe the existence of dark matter substructures, and ultimately shed light on the nature of dark matter. Theoretically predicted dark matter objects, such as small subhalos and primordial black holes, can act as millilenses and introduce beating patterns in gravitational waves - if they exist. While millilensing has been investigated more traditionally in the electromagnetic band, gravitational waves present a new complementary approach to millilensing. Here we show that should millilensing signatures appear in the observed gravitational waves, current-generation gravitational-wave detectors are not only able to detect them, but also reveal the astrophysical nature of the lens. Furthermore, we discuss the advantages of using gravitational waves to probe millilensing. |
Tuesday, April 18, 2023 4:33PM - 4:45PM |
V09.00005: Measuring the polarization content of gravitational waves with strongly lensed binary black hole mergers Ignacio Magana Hernandez Alternative modified theories of gravity predict up to six distinct polarization modes for gravitational-wave (GW) sources. In order to measure the relative amplitudes for each mode, we require at least six linearly-independent GW detectors, as they measure the projection of the GW signal onto their geometry. This projection is encoded in the antenna pattern functions of the instruments, which modulate the detectability of each mode as a function of time due to Earth's rotation. Strong gravitational lensing of gravitational waves allows us to probe the polarization content of these signals by effectively increasing the number of possible observations from the same astrophysical source. Given that the lensed images will arrive at different times, each measures a different projection of the GW waveform originating from the same astrophysical system, effectively doubling the number of detectors that observe the same event (for a pair of lensed events) and allowing us to measure the relative amplitudes of additional polarization modes. To measure these amplitudes, we jointly fit the lensed image observations to a single GW signal model, taking into account the image magnifications, time delays, and polarization mode amplitudes. We show that for specific GW signals from binary black hole mergers, we can make a measurement of the relative mode amplitudes for strongly lensed events with at least two detectable images. |
Tuesday, April 18, 2023 4:45PM - 4:57PM |
V09.00006: Effect of precession on golden dark sirens Ish M Gupta, Arnab Dhani, Bangalore S Sathyaprakash Gravitational-wave observations from binary black hole (BBH) mergers, also called dark sirens, provide an estimate of the luminosity distance. For some dark siren events, the sky position is measured well enough to uniquely identify the host galaxy and measure its redshift. Together with the luminosity distance measurement, this provides a method independent of the cosmic distance ladder to calculate the Hubble-Lemaître constant (H0). A fraction of these dark siren events can be golden events that individually measure H0 to better than 2% precision, which is enough to resolve the H0 tension. In this work, we study the effect of precession in the measurement of H0 for BBH systems. We also report the number of golden dark siren events that are expected to be detected in the next LIGO-Virgo observing run (O4). |
Tuesday, April 18, 2023 4:57PM - 5:09PM |
V09.00007: Estimating systematic bias in gravitational-wave dark siren cosmology measurements Alexandra G Hanselman, Aditya Vijaykumar, Daniel Holz The discovery of GW170817 provided the first direct gravitational-wave measurement of the Hubble constant, H0, demonstrating the potential power of standard-siren cosmology. The dark siren approach can be utilized for gravitational-wave sources in the absence of an electromagnetic counterpart: one considers all galaxies contained within the localization volume as potential hosts. This method can be improved by weighting the potential host galaxies by their luminosities to account for physically-motivated prescriptions (e.g., tracing star formation or stellar mass). Using mock galaxy catalogs, we explore the impact of these weightings on the measurement of H0, focusing on the bias in H0 inference that results from incorrectly weighted prescriptions. |
Tuesday, April 18, 2023 5:09PM - 5:21PM |
V09.00008: Bounds on the spatial anisotropy of foreground binary black hole merger detections in the third LIGO-Virgo-KAGRA catalog Marco Cavaglia, Jacob Golomb, Nikolaos Kouvatsos, Arianna Renzini, Mairi Sakellariadou, Yanyan Zheng The detection of about one hundred binary black hole mergers in the first three LIGO-Virgo-KAGRA observing runs has turned GW astrophysics into a precision observational science. In large-scale astrophysics and observational cosmology, the two-point auto-correlation function (or its homolog in the frequency space, the power spectrum) is commonly used to describe the spatial distribution of galaxies or the density fluctuations in the cosmic microwave background. We measure the level of anisotropy in the observed spatial distribution of gravitational-wave binary black hole mergers by computing the power spectrum and the two-dimensional correlation function of detections from the third LIGO-Virgo-KAGRA catalog, GWTC-3. The degree of clustering in the spatial and angular distribution of BBH mergers at different angular scales is measured by comparing the observed power spectrum with the power spectrum of uniformly distributed synthetic data sets produced according to the latest GWTC-3 rate and population functions. This method complements traditional stochastic gravitational-wave background searches as it probes anisotropy through resolved foreground sources. Even though the two methods essentially target the same signal in the limit of a large number of detections, the foreground analysis is expected to have higher resolution at smaller angular scales. With the expected rapid growth in the number of binary black hole coalescence detections and the improvement in their sky localizations, this method could be used in the future to produce direct upper limits on the degree of correlation between gravitational-wave sources and other populations of extragalactic objects. |
Tuesday, April 18, 2023 5:21PM - 5:33PM |
V09.00009: Gravitational-waves in the LSD band from a Galactic population of axion clouds Jacob Sprague The Levitated Sensor Detector (LSD), currently under development at Northwestern University, is a next-generation gravitational-wave (GW) instrument operating in the 10 kHz - 300 kHz band. Axion clouds will radiate in the LSD band if the boson's mass is in the range 2 x 10-11 eV - 6 x 10-10 eV. To estimate the number of axion clouds in the Milky Way, we must adopt models for the spatial, mass, and age distributions of Galactic black holes. In this talk, we will describe our simulated population, and we will present the resultant set of signals for different assumed spin distributions. |
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