Foreground separation and constraints on primordial gravitational waves with the PICO space mission
Abstract PICO is a concept for a NASA probe-scale mission aiming to detect or constrain the tensor to scalar ratio r , a parameter that quantifies the amplitude of inflationary gravity waves. We carry out map-based component separation on simulations with five foreground models and input r values r...
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Published in | Journal of cosmology and astroparticle physics Vol. 2023; no. 6; pp. 34 - 71 |
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Main Authors | , , , , , , , , , , , , , , , , |
Format | Journal Article |
Language | English Norwegian |
Published |
Bristol
IOP Publishing
01.06.2023
Institute of Physics (IOP) |
Subjects | |
Online Access | Get full text |
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Summary: | Abstract
PICO is a concept for a NASA probe-scale mission aiming to detect or constrain the tensor to scalar ratio
r
, a parameter that quantifies the amplitude of inflationary gravity waves.
We carry out map-based component separation on simulations with five foreground models and input
r
values
r
in
= 0 and
r
in
= 0.003. We forecast
r
determinations using a Gaussian likelihood assuming either no delensing or a residual lensing factor
A
lens
= 27%. By implementing the first full-sky, post component-separation, map-domain delensing, we show that PICO should be able to achieve
A
lens
= 22% – 24%. For four of the five foreground models we find that PICO would be able to set the constraints
r
< 1.3 × 10
-4
to
r
< 2.7 × 10
-4
(95%) if
r
in
= 0, the strongest constraints of any foreseeable instrument. For these models,
r
= 0.003 is recovered with confidence levels between 18
σ
and 27
σ
. We find weaker, and in some cases significantly biased, upper limits when removing few low or high frequency bands. The fifth model gives a 3
σ
detection when
r
in
= 0 and a 3
σ
bias with
r
in
= 0.003. However, by correlating
r
determinations from many small 2.5% sky areas with the mission's 555 GHz data we identify and mitigate the bias. This analysis underscores the importance of large sky coverage. We show that when only low multipoles ℓ ≤ 12 are used, the non-Gaussian shape of the true likelihood gives uncertainties that are on average 30% larger than a Gaussian approximation. |
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ISSN: | 1475-7516 1475-7508 1475-7516 |
DOI: | 10.1088/1475-7516/2023/06/034 |