The primordial information content of Rayleigh Anisotropies. (arXiv:2010.10481v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Coulton_W/0/1/0/all/0/1">William R. Coulton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Beringue_B/0/1/0/all/0/1">Benjamin Beringue</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Meerburg_P/0/1/0/all/0/1">P. Daniel Meerburg</a>
Anisotropies in the cosmic microwave background (CMB) are primarily generated
by Thomson scattering of photons by free electrons. Around recombination, the
Thomson scattering probability quickly diminishes as the free electrons combine
with protons to form neutral hydrogen off which CMB photons can scatter through
Rayleigh scattering. Unlike Thomson scattering, Rayleigh scattering is
frequency dependent resulting in the generation of anisotropies with a
different spectral dependence. Unfortunately the Rayleigh scattering efficiency
rapidly decreases with the expansion of the neutral universe, with the result
that only a small percentage of photons are scattered by neutral hydrogen.
Although the effect is very small, future CMB missions with higher sensitivity
and improved frequency coverage are poised to measure Rayleigh scattering
signal. The uncorrelated component of the Rayleigh anisotropies contains unique
information on the primordial perturbations that could potentially be leveraged
to expand our knowledge of the early universe. In this paper we explore whether
measurements of Rayleigh scattering anisotropies can be used to constrain
primordial non-Gaussianity (NG) and examine the hints of anomalies found by
WMAP and textit{Planck} satellites. We show that the additional Rayleigh
information has the potential to improve primordial NG constraints by $30%$,
or more. Primordial bispectra that are not of the local type benefit the most
from these additional scatterings, which we attribute to the different scale
dependence of the Rayleigh anisotropies. Unfortunately this different scaling
means that Rayleigh measurements can not be used to constrain anomalies or
features on large scales. On the other hand, anomalies that may persist to
smaller scales, such as the potential power asymmetry seen in WMAP and
textit{Planck}, could be improved by the addition of Rayleigh measurements.
Anisotropies in the cosmic microwave background (CMB) are primarily generated
by Thomson scattering of photons by free electrons. Around recombination, the
Thomson scattering probability quickly diminishes as the free electrons combine
with protons to form neutral hydrogen off which CMB photons can scatter through
Rayleigh scattering. Unlike Thomson scattering, Rayleigh scattering is
frequency dependent resulting in the generation of anisotropies with a
different spectral dependence. Unfortunately the Rayleigh scattering efficiency
rapidly decreases with the expansion of the neutral universe, with the result
that only a small percentage of photons are scattered by neutral hydrogen.
Although the effect is very small, future CMB missions with higher sensitivity
and improved frequency coverage are poised to measure Rayleigh scattering
signal. The uncorrelated component of the Rayleigh anisotropies contains unique
information on the primordial perturbations that could potentially be leveraged
to expand our knowledge of the early universe. In this paper we explore whether
measurements of Rayleigh scattering anisotropies can be used to constrain
primordial non-Gaussianity (NG) and examine the hints of anomalies found by
WMAP and textit{Planck} satellites. We show that the additional Rayleigh
information has the potential to improve primordial NG constraints by $30%$,
or more. Primordial bispectra that are not of the local type benefit the most
from these additional scatterings, which we attribute to the different scale
dependence of the Rayleigh anisotropies. Unfortunately this different scaling
means that Rayleigh measurements can not be used to constrain anomalies or
features on large scales. On the other hand, anomalies that may persist to
smaller scales, such as the potential power asymmetry seen in WMAP and
textit{Planck}, could be improved by the addition of Rayleigh measurements.
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