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Consistency of JWST Black Hole Observations with NANOGrav Gravitational Wave Measurements
/ Ellis, John (King's Coll. London ; CERN) ; Fairbairn, Malcolm (King's Coll. London) ; Hütsi, Gert (Unlisted, EE) ; Urrutia, Juan (Unlisted, EE ; NICPB, Tallinn) ; Vaskonen, Ville (Unlisted, EE ; Padua U. ; INFN, Padua) ; Veermäe, Hardi (Unlisted, EE)
JWST observations have opened a new chapter in studies of supermassive black holes (SMBHs), stimulating discussion of two puzzles: the abundance of SMBHs in the early Universe and the fraction of dual AGNs. In this paper we argue that the answers to these puzzles may be linked to an interpretation of the data on the nHz gravitational wave (GWs) discovered by NANOGrav and other Pulsar Timing Arrays (PTAs) in terms of SMBH binaries losing energy by interactions with their environments as well as by GW emission. [...]
arXiv:2403.19650; KCL-PH-TH/2024-16; CERN-TH-2024-038; AION-REPORT/2024-03.-
2024-11-01 - 9 p.
- Published in : Astron. Astrophys. 691 (2024) A270
Fulltext: 2403.19650 - PDF; Publication - PDF; document - PDF;
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Probing Supermassive Black Hole Seed Scenarios with Gravitational-wave Measurements
/ Ellis, John (King's Coll. London ; CERN) ; Fairbairn, Malcolm (King's Coll. London) ; Urrutia, Juan ; Vaskonen, Ville
The process whereby the supermassive black holes populating the centers of galaxies have been assembled remains to be established, with the relative importance of seeds provided by collapsed Population-III stars, black holes formed in nuclear star clusters via repeated mergers, or direct collapses of protogalactic disks yet to be determined. In this paper we study the prospects for casting light on this issue by future measurements of gravitational waves emitted during the inspirals and mergers of pairs of intermediate-mass black holes, discussing in particular the roles of prospective measurements by LISA and the proposed atom interferometers AION and AEDGE. [...]
arXiv:2312.02983; KCL-PH-TH/2023-69; CERN-TH-2023-227.-
2024-03-11 - 7 p.
- Published in : Astrophys. J. 964 (2024) 11
Fulltext: document - PDF; 2312.02983 - PDF;
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What is the source of the PTA GW signal?
/ Ellis, John (NICPB, Tallinn ; King's Coll. London ; CERN) ; Fairbairn, Malcolm (King's Coll. London) ; Franciolini, Gabriele (Rome U. ; INFN, Rome) ; Hütsi, Gert (NICPB, Tallinn) ; Iovino, Antonio (NICPB, Tallinn ; Rome U. ; INFN, Rome) ; Lewicki, Marek (Warsaw U.) ; Raidal, Martti (NICPB, Tallinn) ; Urrutia, Juan (NICPB, Tallinn ; Tallinn U. Tech.) ; Vaskonen, Ville (NICPB, Tallinn ; Padua U. ; INFN, Padua) ; Veermäe, Hardi (NICPB, Tallinn)
The most conservative interpretation of the nHz stochastic gravitational wave background (SGWB) discovered by NANOGrav and other Pulsar Timing Array (PTA) Collaborations is astrophysical, namely that it originates from supermassive black hole (SMBH) binaries. However, alternative cosmological models have been proposed, including cosmic strings, phase transitions, domain walls, primordial fluctuations and "audible" axions. [...]
arXiv:2308.08546; KCL-PH-TH/2023-43; CERN-TH-2023-153; AION-REPORT/2023-08.-
2024-01-15 - 22 p.
- Published in : Phys. Rev. D 109 (2024) 023522
Fulltext: PDF;
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Gravitational Waves from SMBH Binaries in Light of the NANOGrav 15-Year Data
/ Ellis, John (Unlisted, EE ; King's Coll. London ; CERN) ; Fairbairn, Malcolm (King's Coll. London) ; Hütsi, Gert (Unlisted, EE) ; Raidal, Juhan (Unlisted, EE) ; Urrutia, Juan (Unlisted, EE ; NICPB, Tallinn) ; Vaskonen, Ville (Unlisted, EE ; Padua U. ; INFN, Padua) ; Veermäe, Hardi (Unlisted, EE)
The NANOGrav Collaboration has recently announced evidence for nHz gravitational waves (GWs), in the form of a Hellings-Downs angular correlation in the common-spectrum process that had been observed previously by them and other Pulsar Timing Arrays (PTAs). We analyze the possibility that these GWs originate from binary supermassive black holes (SMBHs) with total masses $\gtrsim 10^9\, M_{\odot}$. [...]
arXiv:2306.17021; KCL-PH-TH/2023-37; CERN-TH-2023-120; AION-REPORT/2023-06.-
2024-01-10 - 11 p.
- Published in : Phys. Rev. D 109 (2024) L021302
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Axion Star Explosions: A New Source for Axion Indirect Detection
/ Escudero, Miguel (CERN) ; Pooni, Charis Kaur (King's Coll. London) ; Fairbairn, Malcolm (King's Coll. London) ; Blas, Diego (Barcelona, Autonoma U. ; Barcelona, IFAE) ; Du, Xiaolong (Carnegie Inst. Observ. ; UCLA) ; Marsh, David J.E. (King's Coll. London)
If dark matter is composed of axions, then axion stars form in the cores of dark matter halos. These stars are unstable above a critical mass, decaying to radio photons that heat the intergalactic medium, offering a new channel for axion indirect detection. [...]
arXiv:2302.10206; KCL-PH-TH-2023-16; CERN-TH-2023-029.-
2024-02-08 - 16 p.
- Published in : Phys. Rev. D 109 (2024) 043018
Fulltext: Publication - PDF; 2302.10206 - PDF; External link: TheConversation article
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Prospects for Future Binary Black Hole GW Studies in Light of PTA Measurements
/ Ellis, John (CERN ; King's Coll. London ; Unlisted, EE) ; Fairbairn, Malcolm (King's Coll. London) ; Hütsi, Gert (Unlisted, EE) ; Raidal, Martti (Unlisted, EE) ; Urrutia, Juan (Unlisted, EE ; NICPB, Tallinn) ; Vaskonen, Ville (Unlisted, EE ; Padua U. ; INFN, Padua) ; Veermäe, Hardi (Unlisted, EE)
NANOGrav and other Pulsar Timing Arrays (PTAs) have discovered a common-spectrum process in the nHz range that may be due to gravitational waves (GWs): if so, they are likely to have been generated by black hole (BH) binaries with total masses $> 10^9 M_{\odot}$. Using the Extended Press-Schechter formalism to model the galactic halo mass function and a simple relation between the halo and BH masses suggests that these binaries have redshifts $z = {O}(1)$ and mass ratios $\gtrsim 10$, and that the GW signal at frequencies above ${O}(10)$~nHz may be dominated by relatively few binaries that could be distinguished experimentally and would yield observable circular polarization. [...]
arXiv:2301.13854; KCL-PH-TH/2023-04; CERN-TH-2023-008; AION-REPORT/2023-1.-
2023-08-01 - 13 p.
- Published in : Astron. Astrophys. 676 (2023) A38
Fulltext: document - PDF; Publication - PDF; 2301.13854 - PDF;
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