Disentangling Multiple Stochastic Gravitational Wave Background Sources in PTA Datasets. (arXiv:2208.02307v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Kaiser_A/0/1/0/all/0/1">Andrew R. Kaiser</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pol_N/0/1/0/all/0/1">Nihan S. Pol</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McLaughlin_M/0/1/0/all/0/1">Maura A. McLaughlin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_S/0/1/0/all/0/1">Siyuan Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hazboun_J/0/1/0/all/0/1">Jeffrey S. Hazboun</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kelley_L/0/1/0/all/0/1">Luke Zoltan Kelley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Simon_J/0/1/0/all/0/1">Joseph Simon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Taylor_S/0/1/0/all/0/1">Stephen R. Taylor</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vigeland_S/0/1/0/all/0/1">Sarah J. Vigeland</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Witt_C/0/1/0/all/0/1">Caitlin A. Witt</a>
With strong evidence of a common-spectrum stochastic process in the most
recent datasets from the NANOGrav Collaboration, the European Pulsar Timing
Array (PTA), Parkes PTA, and the International PTA, it is crucial to assess the
effects of the several astrophysical and cosmological sources that could
contribute to the stochastic gravitational wave background (GWB). Using the
same dataset creation and injection techniques as in Pol et al. (2021), we
assess the separability of multiple GWBs by creating single and multiple GWB
source datasets. We search for these injected sources using Bayesian PTA
analysis techniques to assess recovery and separability of multiple
astrophysical and cosmological backgrounds. For a GWB due to supermassive black
hole binaries and an underlying weaker background due to primordial
gravitational waves with a GW energy density ratio of
$Omega_{mathrm{PGW}}/Omega_{mathrm{SMBHB}} = 0.5$, the Bayes’ factor for a
second process exceeds unity at 17 years, and increases with additional data.
At 20 years of data, we are able to constrain the spectral index and amplitude
of the weaker GWB at this density ratio to a fractional uncertainty of 64% and
110%, respectively, using current PTA methods and techniques. Using these
methods and findings, we outline a basic protocol to search for multiple
backgrounds in future PTA datasets.
With strong evidence of a common-spectrum stochastic process in the most
recent datasets from the NANOGrav Collaboration, the European Pulsar Timing
Array (PTA), Parkes PTA, and the International PTA, it is crucial to assess the
effects of the several astrophysical and cosmological sources that could
contribute to the stochastic gravitational wave background (GWB). Using the
same dataset creation and injection techniques as in Pol et al. (2021), we
assess the separability of multiple GWBs by creating single and multiple GWB
source datasets. We search for these injected sources using Bayesian PTA
analysis techniques to assess recovery and separability of multiple
astrophysical and cosmological backgrounds. For a GWB due to supermassive black
hole binaries and an underlying weaker background due to primordial
gravitational waves with a GW energy density ratio of
$Omega_{mathrm{PGW}}/Omega_{mathrm{SMBHB}} = 0.5$, the Bayes’ factor for a
second process exceeds unity at 17 years, and increases with additional data.
At 20 years of data, we are able to constrain the spectral index and amplitude
of the weaker GWB at this density ratio to a fractional uncertainty of 64% and
110%, respectively, using current PTA methods and techniques. Using these
methods and findings, we outline a basic protocol to search for multiple
backgrounds in future PTA datasets.
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