Circumventing Cosmic Variance via Remote Quadrupole Measurements

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Hauptverfasser: Adil, Arsalan, Koutras, Reid, Bunn, Emory F.
Format: Preprint
Veröffentlicht: 2024
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author Adil, Arsalan
Koutras, Reid
Bunn, Emory F.
author_facet Adil, Arsalan
Koutras, Reid
Bunn, Emory F.
contents A number of important cosmological questions can be addressed only by probing perturbation modes on the largest accessible scales. One promising probe of these modes is the Kamionkowski-Loeb effect, i.e., the polarization induced in the cosmic microwave background (CMB) by Thomson scattering in galaxy clusters, which is proportional to the CMB quadrupole measured at the cluster's location and look-back time. We develop a Fisher formalism for assessing the amount of new information that can be obtained from a future remote quadrupole survey. To demonstrate the constraining power of such a survey, we apply our formalism to a model that suppresses the primordial power spectrum on large scales but is poorly constrained with existing CMB data. We find that the constraints can be improved by over $3σ$ for a survey that measures around 100 clusters over $20\%$ of the sky with a signal-to-noise ratio of $3$. In the most optimistic case with a low-noise survey with dense full-sky coverage and only a single degree of freedom in the theory, the constraint improves to over $7σ$ beyond local CMB data. Our formalism, which is based in real space rather than harmonic space, can be used to explore a wide range of survey designs, and our results paint an optimistic picture for the utility of remote quadrupole measurements to probe physics on the largest observable scales in the Universe.
format Preprint
id arxiv_https___arxiv_org_abs_2410_07412
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Circumventing Cosmic Variance via Remote Quadrupole Measurements
Adil, Arsalan
Koutras, Reid
Bunn, Emory F.
Cosmology and Nongalactic Astrophysics
High Energy Physics - Theory
A number of important cosmological questions can be addressed only by probing perturbation modes on the largest accessible scales. One promising probe of these modes is the Kamionkowski-Loeb effect, i.e., the polarization induced in the cosmic microwave background (CMB) by Thomson scattering in galaxy clusters, which is proportional to the CMB quadrupole measured at the cluster's location and look-back time. We develop a Fisher formalism for assessing the amount of new information that can be obtained from a future remote quadrupole survey. To demonstrate the constraining power of such a survey, we apply our formalism to a model that suppresses the primordial power spectrum on large scales but is poorly constrained with existing CMB data. We find that the constraints can be improved by over $3σ$ for a survey that measures around 100 clusters over $20\%$ of the sky with a signal-to-noise ratio of $3$. In the most optimistic case with a low-noise survey with dense full-sky coverage and only a single degree of freedom in the theory, the constraint improves to over $7σ$ beyond local CMB data. Our formalism, which is based in real space rather than harmonic space, can be used to explore a wide range of survey designs, and our results paint an optimistic picture for the utility of remote quadrupole measurements to probe physics on the largest observable scales in the Universe.
title Circumventing Cosmic Variance via Remote Quadrupole Measurements
topic Cosmology and Nongalactic Astrophysics
High Energy Physics - Theory
url https://arxiv.org/abs/2410.07412