Detectability of lensed gravitational waves in matched-filtering searches

Creators: Chan, Juno C. L.¹; Seo, Eungwang²; Li, Alvin K. Y.^{3, 4, 5}; Fong, Heather⁶; Ezquiaga, Jose M.¹

1. University of Copenhagen
2. Scottish Universities Physics Alliance
3. University of Tokyo
4. Chinese University of Hong Kong
5. California Institute of Technology
6. University of British Columbia

Abstract

Gravitational lensing by compact, small-scale intervening masses causes frequency-dependent distortions to gravitational-wave events. The optimal signal-to-noise ratio (SNR) is often used as a proxy for the detectability of exotic signals in gravitational-wave searches. In reality, the detectability of such signals in a matched-filtering search requires comprehensive consideration of match-filtered SNR, signal-consistency test value, and other factors. In this work, we investigate for the first time the detectability of lensed gravitational waves from compact binary coalescences with a match-filtering search pipeline, GstLAL. Contrary to expectations from the optimal SNR approximation approach, we show that the strength of a signal (i.e., higher optimal SNR) does not necessarily result in higher detectability. We also demonstrate that lensed gravitational waves with wave optic effects can suffer significantly, from 90% (unlensed) to <1% (lensed) detection efficiency, due to downranking by the signal-consistency test values. These findings stress the need to extend current template banks to effectively search for lensed gravitational waves and to reassess current constraints on compact dark matter scenarios.

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Acknowledgement

The authors would also like to acknowledge Kipp Cannon, Luka Vujeva, Rico Ka Lok Lo, and Elwin Ka Yau Li for their useful suggestions. J. C. L. C. and J. M. E. acknowledge support from the Villum Investigator program supported by the VILLUM Foundation (Grants No. VIL37766 and No. VIL53101) and the DNRF Chair program (Grant No. DNRF162) by the Danish National Research Foundation. E. S. is supported by grants from the College of Science and Engineering of the University of Glasgow. K. Y. A. L. would like to acknowledge the support from Croucher Foundation. H. F. acknowledges support from the CITA National Fellows program, the NSERC DG program, and the Canada Research Chairs program. This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant Agreement No. 101131233. J. M. E. is also supported by the Marie Sklodowska-Curie Grant Agreement No. 847523 INTERACTIONS. The Tycho supercomputer hosted at the SCIENCE HPC center at the University of Copenhagen was used for supporting this work. This research has made use of data or software obtained from the Gravitational Wave Open Science Center [94], a service of the LIGO Scientific Collaboration, the Virgo Collaboration, and KAGRA. This material is based upon work supported by NSF’s LIGO Laboratory which is a major facility fully funded by the National Science Foundation, as well as the Science and Technology Facilities Council (STFC) of the United Kingdom, the Max-Planck-Society (MPS), and the State of Niedersachsen/Germany for support of the construction of Advanced LIGO and construction and operation of the GEO600 detector. Additional support for Advanced LIGO was provided by the Australian Research Council. Virgo is funded, through the European Gravitational Observatory (EGO), by the French Centre National de Recherche Scientifique (CNRS), the Italian Istituto Nazionale di Fisica Nucleare (INFN), and the Dutch Nikhef, with contributions by institutions from Belgium, Germany, Greece, Hungary, Ireland, Japan, Monaco, Poland, Portugal, and Spain. K. A. G. R. A. is supported by Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan Society for the Promotion of Science (JSPS) in Japan; National Research Foundation (NRF) and Ministry of Science and ICT (MSIT) in Korea; Academia Sinica (AS) and National Science and Technology Council (NSTC) in Taiwan.

Data Availability

The data that support the findings of this article are not publicly available upon publication because it is not technically feasible and/or the cost of preparing, depositing, and hosting the data would be prohibitive within the terms of this research project. The data are available from the authors upon reasonable request.

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