The MeerKAT Pulsar Timing Array: Maps of the gravitational wave sky with the 4.5-yr data release

ABSTRACT In an accompanying publication, the MeerKAT Pulsar Timing Array (MPTA) Collaboration reports tentative evidence for the presence of a stochastic gravitational wave background, following observations of similar signals from the European and Indian Pulsar Timing Arrays, the North American Nanohertz Observatory for Gravitational Waves, the Parkes Pulsar Timing Array, and the Chinese Pulsar Timing Array. If such a gravitational wave background signal originates from a population of inspiraling supermassive black hole binaries, the signal may be anisotropically distributed in the sky. In this paper, we evaluate the anisotropy of the MPTA signal using a spherical harmonic decomposition. We discuss complications arising from the covariance between pulsar pairs and the regularization of the Fisher matrix. Applying our method to the $4.5 \hbox{-}\text{yr}$ data set, we obtain two forms of sky maps for the three most sensitive MPTA frequency bins between $7 \ {\rm and} \ 21 \, {\rm nHz}$. Our ‘clean maps’ estimate the distribution of gravitational wave strain power with minimal assumptions. Our radiometer maps answer the question: Is there a statistically significant point source? We find a noteworthy hotspot in the $7 \, \mathrm{nHz}$ clean map with a p-factor of $p=0.015$ (not including trial factors). Future observations are required to determine if this hotspot is of astrophysical origin.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2024-12-03
DOI
https://doi.org/10.1093/mnras/stae2573
Citations
11
Primary Topic
Pulsars and Gravitational Waves Research
Type
article
Field-Weighted Citation Impact
3.65

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article

The MeerKAT Pulsar Timing Array: Maps of the gravitational wave sky with the 4.5-yr data release

P. D. Lasky, Jaikhomba Singha, Sarah Buchner, D. J. Champion et al.
11 citations
Monthly Notices of the Royal Astronomical Society
Pulsars and Gravitational Waves Research
3.65
article

The MeerKAT Pulsar Timing Array: Maps of the gravitational wave sky with the 4.5-yr data release

P. D. Lasky, Jaikhomba Singha, Sarah Buchner, D. J. Champion, Kathrin Grunthal, Rowina S Nathan, R. M. Shannon, Daniel J. Reardon, A. Parthasarathy, Atharva Kulkarni, M. Kramer, Marisa Geyer, Federico Abbate, V. Venkatraman Krishnan, A D Cameron, M. J. Keith, E. Thrane, Matthew T. Miles, Pratyasha Gitika
article en
11 citations

Abstract

ABSTRACT In an accompanying publication, the MeerKAT Pulsar Timing Array (MPTA) Collaboration reports tentative evidence for the presence of a stochastic gravitational wave background, following observations of similar signals from the European and Indian Pulsar Timing Arrays, the North American Nanohertz Observatory for Gravitational Waves, the Parkes Pulsar Timing Array, and the Chinese Pulsar Timing Array. If such a gravitational wave background signal originates from a population of inspiraling supermassive black hole binaries, the signal may be anisotropically distributed in the sky. In this paper, we evaluate the anisotropy of the MPTA signal using a spherical harmonic decomposition. We discuss complications arising from the covariance between pulsar pairs and the regularization of the Fisher matrix. Applying our method to the $4.5 \hbox{-}\text{yr}$ data set, we obtain two forms of sky maps for the three most sensitive MPTA frequency bins between $7 \ {\rm and} \ 21 \, {\rm nHz}$. Our ‘clean maps’ estimate the distribution of gravitational wave strain power with minimal assumptions. Our radiometer maps answer the question: Is there a statistically significant point source? We find a noteworthy hotspot in the $7 \, \mathrm{nHz}$ clean map with a p-factor of $p=0.015$ (not including trial factors). Future observations are required to determine if this hotspot is of astrophysical origin.

Monthly Notices of the Royal Astronomical SocietyVol. 536(2)
University of Cape Town (ZA), University of Manchester (GB), South African Radio Astronomy Observatory (ZA), ARC Centre of Excellence for Gravitational Wave Discovery (AU), Astronomical Institute of the Slovak Academy of Sciences (SK), Osservatorio Astronomico di Cagliari (IT), Max Planck Institute for Radio Astronomy (DE), Monash University (AU), Swinburne University of Technology (AU), University of Amsterdam (NL), Netherlands Institute for Radio Astronomy (NL)
Astronomical Society of Australia, Swinburne University of Technology, Max-Planck-Gesellschaft, Universität zu Köln, Rheinische Friedrich-Wilhelms-Universität Bonn, National Science Foundation, United Arab Emirates, Science and Technology Facilities Council, Australian Research Council, H2020 European Research Council
Openalex Percentile: Top 7%
Pulsars and Gravitational Waves Research
3.65
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