Multi-tracer Correlated Stacking: A Novel Way to Discover Anisotropy in nHz Stochastic Gravitational-wave Background
The isotropic stochastic gravitational-wave background (SGWB) generated by a population of supermassive black hole binaries (SMBHBs) provides a unique window into their cosmic evolution. In addition to the isotropic power spectrum, the anisotropic component of the signal carries additional informati...
Saved in:
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
|
| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/adbf92 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1849321310044291072 |
|---|---|
| author | Mohit Raj Sah Suvodip Mukherjee |
| author_facet | Mohit Raj Sah Suvodip Mukherjee |
| author_sort | Mohit Raj Sah |
| collection | DOAJ |
| description | The isotropic stochastic gravitational-wave background (SGWB) generated by a population of supermassive black hole binaries (SMBHBs) provides a unique window into their cosmic evolution. In addition to the isotropic power spectrum, the anisotropic component of the signal carries additional information about the supermassive black holes (BHs) and host galaxy connection. The measurement of this signal is usually carried out by angular power spectra, which is only a sufficient measure for a Gaussian and statistically isotropic distribution of SMBHBs, where the statistical properties of a field remain unchanged across the sky. In contrast, the contribution from SMBHBs in nHz SGWB will be hosted by fewer massive galaxies, making the nHz background anisotropic and non-Gaussian. As a result, the performance of angular power spectra in extracting the underlying physics is limited. In this work, we propose a novel technique called multi-tracer correlated stacking, which enables the detection of anisotropies in the SGWB by stacking the signal from regions of the sky with tracers of BHs such as active galactic nuclei (AGN), quasars, bright galaxies, etc., that can be mapped up to high redshift. We demonstrate this technique on a simulated population of SMBHBs using an AGN catalog, which maps the underlying matter distribution approximately up to redshift z = 5. This stacking technique uniquely distinguishes between isotropic and anisotropic distributions of SGWB sources, surpassing the capabilities of angular power spectrum-based methods in detecting anisotropic signals. This highlights the effectiveness of this technique in detecting anisotropic SGWB signals, and in the future, this technique can play a crucial role in its discovery. |
| format | Article |
| id | doaj-art-4253e480b86f4c6881b5e97c3c2eccf1 |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-4253e480b86f4c6881b5e97c3c2eccf12025-08-20T03:49:46ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198519210.3847/1538-4357/adbf92Multi-tracer Correlated Stacking: A Novel Way to Discover Anisotropy in nHz Stochastic Gravitational-wave BackgroundMohit Raj Sah0https://orcid.org/0009-0005-9881-1788Suvodip Mukherjee1https://orcid.org/0000-0002-3373-5236Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research , Mumbai 400005, India ; mohit.sah@tifr.res.in, suvodip@tifr.res.inDepartment of Astronomy and Astrophysics, Tata Institute of Fundamental Research , Mumbai 400005, India ; mohit.sah@tifr.res.in, suvodip@tifr.res.inThe isotropic stochastic gravitational-wave background (SGWB) generated by a population of supermassive black hole binaries (SMBHBs) provides a unique window into their cosmic evolution. In addition to the isotropic power spectrum, the anisotropic component of the signal carries additional information about the supermassive black holes (BHs) and host galaxy connection. The measurement of this signal is usually carried out by angular power spectra, which is only a sufficient measure for a Gaussian and statistically isotropic distribution of SMBHBs, where the statistical properties of a field remain unchanged across the sky. In contrast, the contribution from SMBHBs in nHz SGWB will be hosted by fewer massive galaxies, making the nHz background anisotropic and non-Gaussian. As a result, the performance of angular power spectra in extracting the underlying physics is limited. In this work, we propose a novel technique called multi-tracer correlated stacking, which enables the detection of anisotropies in the SGWB by stacking the signal from regions of the sky with tracers of BHs such as active galactic nuclei (AGN), quasars, bright galaxies, etc., that can be mapped up to high redshift. We demonstrate this technique on a simulated population of SMBHBs using an AGN catalog, which maps the underlying matter distribution approximately up to redshift z = 5. This stacking technique uniquely distinguishes between isotropic and anisotropic distributions of SGWB sources, surpassing the capabilities of angular power spectrum-based methods in detecting anisotropic signals. This highlights the effectiveness of this technique in detecting anisotropic SGWB signals, and in the future, this technique can play a crucial role in its discovery.https://doi.org/10.3847/1538-4357/adbf92Supermassive black holesGravitational wavesCosmology |
| spellingShingle | Mohit Raj Sah Suvodip Mukherjee Multi-tracer Correlated Stacking: A Novel Way to Discover Anisotropy in nHz Stochastic Gravitational-wave Background The Astrophysical Journal Supermassive black holes Gravitational waves Cosmology |
| title | Multi-tracer Correlated Stacking: A Novel Way to Discover Anisotropy in nHz Stochastic Gravitational-wave Background |
| title_full | Multi-tracer Correlated Stacking: A Novel Way to Discover Anisotropy in nHz Stochastic Gravitational-wave Background |
| title_fullStr | Multi-tracer Correlated Stacking: A Novel Way to Discover Anisotropy in nHz Stochastic Gravitational-wave Background |
| title_full_unstemmed | Multi-tracer Correlated Stacking: A Novel Way to Discover Anisotropy in nHz Stochastic Gravitational-wave Background |
| title_short | Multi-tracer Correlated Stacking: A Novel Way to Discover Anisotropy in nHz Stochastic Gravitational-wave Background |
| title_sort | multi tracer correlated stacking a novel way to discover anisotropy in nhz stochastic gravitational wave background |
| topic | Supermassive black holes Gravitational waves Cosmology |
| url | https://doi.org/10.3847/1538-4357/adbf92 |
| work_keys_str_mv | AT mohitrajsah multitracercorrelatedstackinganovelwaytodiscoveranisotropyinnhzstochasticgravitationalwavebackground AT suvodipmukherjee multitracercorrelatedstackinganovelwaytodiscoveranisotropyinnhzstochasticgravitationalwavebackground |