Sensitivity forecasts for the cosmological recombination radiation in the presence of foregrounds. (arXiv:2006.04826v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hart_L/0/1/0/all/0/1">Luke Hart</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rotti_A/0/1/0/all/0/1">Aditya Rotti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chluba_J/0/1/0/all/0/1">Jens Chluba</a>
The cosmological recombination radiation (CRR) is one of the inevitable
$Lambda$CDM spectral distortions of the cosmic microwave background (CMB).
While it shows a rich spectral structure across dm-mm wavelengths, it is also
one of the smallest signals to target. Here we carry out a detailed forecast
for the expected sensitivity levels required to not only detect but also
extract cosmological information from the CRR in the presence of foregrounds.
We use ${tt CosmoSpec}$ to compute the CRR including all important radiative
transfer effects and modifications to the recombination dynamics. We confirm
that detections of the overall CRR signal are possible with spectrometer
concepts like ${it SuperPIXIE}$. However, for real exploitation of the
cosmological information, a $simeq 50$ times more sensitive spectrometer is
required. While extremely futuristic, this could provide independent
constraints on the primordial helium abundance, $Y_p$, and probe the presence
of extra relativistic degrees of freedom during BBN and recombination.
Significantly improving the constraints on other cosmological parameters
requires even higher sensitivity (another factor of $simeq 5$) when
considering a combination of a CMB spectrometer with existing CMB data. To a
large part this is due to astrophysical foregrounds which interestingly do not
degrade the constraints on $Y_p$ and $N_{rm eff}$ as much. A future CMB
spectrometer could thus open a novel way of probing non-standard BBN scenarios,
dark radiation and sterile neutrinos. In addition, inflation physics could be
indirectly probed using the CRR in combination with existing and forthcoming
CMB anisotropy data.
The cosmological recombination radiation (CRR) is one of the inevitable
$Lambda$CDM spectral distortions of the cosmic microwave background (CMB).
While it shows a rich spectral structure across dm-mm wavelengths, it is also
one of the smallest signals to target. Here we carry out a detailed forecast
for the expected sensitivity levels required to not only detect but also
extract cosmological information from the CRR in the presence of foregrounds.
We use ${tt CosmoSpec}$ to compute the CRR including all important radiative
transfer effects and modifications to the recombination dynamics. We confirm
that detections of the overall CRR signal are possible with spectrometer
concepts like ${it SuperPIXIE}$. However, for real exploitation of the
cosmological information, a $simeq 50$ times more sensitive spectrometer is
required. While extremely futuristic, this could provide independent
constraints on the primordial helium abundance, $Y_p$, and probe the presence
of extra relativistic degrees of freedom during BBN and recombination.
Significantly improving the constraints on other cosmological parameters
requires even higher sensitivity (another factor of $simeq 5$) when
considering a combination of a CMB spectrometer with existing CMB data. To a
large part this is due to astrophysical foregrounds which interestingly do not
degrade the constraints on $Y_p$ and $N_{rm eff}$ as much. A future CMB
spectrometer could thus open a novel way of probing non-standard BBN scenarios,
dark radiation and sterile neutrinos. In addition, inflation physics could be
indirectly probed using the CRR in combination with existing and forthcoming
CMB anisotropy data.
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