{"date_published":"2025-04-04T00:00:00Z","issue":"7","status":"public","language":[{"iso":"eng"}],"month":"04","scopus_import":"1","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","main_file_link":[{"url":"https://doi.org/10.48550/arXiv.2412.12726","open_access":"1"}],"quality_controlled":"1","year":"2025","publication_identifier":{"eissn":["1361-6382"],"issn":["0264-9381"]},"citation":{"apa":"Kis-Tóth, Á., Haiman, Z., &#38; Frei, Z. (2025). Can quasars, triggered by mergers, account for NANOGrav’s stochastic gravitational wave background? <i>Classical and Quantum Gravity</i>. IOP Publishing. <a href=\"https://doi.org/10.1088/1361-6382/adbda6\">https://doi.org/10.1088/1361-6382/adbda6</a>","ieee":"Á. Kis-Tóth, Z. Haiman, and Z. Frei, “Can quasars, triggered by mergers, account for NANOGrav’s stochastic gravitational wave background?,” <i>Classical and Quantum Gravity</i>, vol. 42, no. 7. IOP Publishing, 2025.","short":"Á. Kis-Tóth, Z. Haiman, Z. Frei, Classical and Quantum Gravity 42 (2025).","mla":"Kis-Tóth, Ágnes, et al. “Can Quasars, Triggered by Mergers, Account for NANOGrav’s Stochastic Gravitational Wave Background?” <i>Classical and Quantum Gravity</i>, vol. 42, no. 7, 075007, IOP Publishing, 2025, doi:<a href=\"https://doi.org/10.1088/1361-6382/adbda6\">10.1088/1361-6382/adbda6</a>.","chicago":"Kis-Tóth, Ágnes, Zoltán Haiman, and Zsolt Frei. “Can Quasars, Triggered by Mergers, Account for NANOGrav’s Stochastic Gravitational Wave Background?” <i>Classical and Quantum Gravity</i>. IOP Publishing, 2025. <a href=\"https://doi.org/10.1088/1361-6382/adbda6\">https://doi.org/10.1088/1361-6382/adbda6</a>.","ama":"Kis-Tóth Á, Haiman Z, Frei Z. Can quasars, triggered by mergers, account for NANOGrav’s stochastic gravitational wave background? <i>Classical and Quantum Gravity</i>. 2025;42(7). doi:<a href=\"https://doi.org/10.1088/1361-6382/adbda6\">10.1088/1361-6382/adbda6</a>","ista":"Kis-Tóth Á, Haiman Z, Frei Z. 2025. Can quasars, triggered by mergers, account for NANOGrav’s stochastic gravitational wave background? Classical and Quantum Gravity. 42(7), 075007."},"abstract":[{"text":"The stochastic gravitational wave (GW) background recently discovered by several pulsar timing array experiments is consistent with arising from a population of coalescing super-massive black hole binaries. The amplitude of the background is somewhat higher than expected in most previous population models or from the local mass density observations. Such binaries are expected to be produced in galaxy mergers, which are also thought to trigger bright quasar activity. Under the assumptions that (i) a fraction fbin∼1 of all quasars are associated with mergers, (ii) the typical quasar lifetime is tQ∼108 yr, and (iii) adopting Eddington ratios fEdd∼0.25 for the luminosity of quasars, we compute the GW background associated directly with the empirically measured quasar luminosity function. This approach bypasses the need to model the cosmological evolution of black holes or galaxy mergers from simulations or semi-analytical models. We find the amplitude matching the value measured by NANOGrav. Our results are consistent with most quasars being associated with black hole binaries and being the sources of the GW background, and imply a joint constraint on tQ, fEdd and the typical mass ratio q≡M2/M1. The signal in this case would be dominated by relatively distant ∼109M⊙ sources at z≈2−3, at the peak of quasar activity. Similarly to other models, our results remain in tension with the local super-massive black hole mass density.","lang":"eng"}],"day":"04","date_created":"2025-04-06T22:01:32Z","acknowledgement":"We thank Chengcheng Xin and Girish Kulkarni for useful discussions. ZH gratefully acknowledges the hospitality of Eötvös University during an extended sabbatical visit, where this work began. ZH acknowledges support from NSF Grant AST-2006176 and NASA Grants 80NSSC22K0822 and 80NSSC24K0440. ZF acknowledges support from the Hungarian National Research, Development and Innovation Office (NKFIH) through the Institutional Excellence Program No. TKP2021-NKTA-64.","OA_type":"green","volume":42,"external_id":{"arxiv":["2412.12726"]},"OA_place":"repository","title":"Can quasars, triggered by mergers, account for NANOGrav’s stochastic gravitational wave background?","article_type":"original","arxiv":1,"author":[{"last_name":"Kis-Tóth","first_name":"Ágnes","full_name":"Kis-Tóth, Ágnes"},{"last_name":"Haiman","id":"7c006e8c-cc0d-11ee-8322-cb904ef76f36","full_name":"Haiman, Zoltán","orcid":"0000-0003-3633-5403","first_name":"Zoltán"},{"last_name":"Frei","first_name":"Zsolt","full_name":"Frei, Zsolt"}],"publisher":"IOP Publishing","publication_status":"published","date_updated":"2025-05-14T11:37:21Z","department":[{"_id":"ZoHa"}],"doi":"10.1088/1361-6382/adbda6","article_number":"075007","intvolume":"        42","_id":"19497","type":"journal_article","article_processing_charge":"No","publication":"Classical and Quantum Gravity","oa":1,"oa_version":"Preprint"}