Baryons still trace dark matter: probing CMB lensing maps for hidden isocurvature

Daniel Grin; Julian B. Mu\~noz; Kyle Yee; Rhiannon Smith; Tristan L. Smith

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Baryons still trace dark matter: probing CMB lensing maps for hidden isocurvature

Tristan L. Smith, Julian B. Muñoz, Rhiannon Smith, Kyle Yee, Daniel Grin

Cosmology and Nongalactic Astrophysics · Submitted 11 Apr 2017

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim The method presented here is currently the most sensitive probe of the amplitude of a scale-invariant CIP power spectrum placing an upper limit of $A_{\rm CIP}< 0.017$ at 95% CL.

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arXiv ID1704.03461 (version 2)

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CitationDaniel Grin, Julian B. Mu\~noz, Kyle Yee, Rhiannon Smith, Tristan L. Smith. "Baryons still trace dark matter: probing CMB lensing maps for hidden isocurvature." arXiv:1704.03461 (2017). https://pith.science/paper/RI24SMZ7

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Compensated isocurvature perturbations (CIPs) are primordial fluctuations that balance baryon and dark-matter isocurvature to leave the total matter density unperturbed. The effects of CIPs on the cosmic microwave background (CMB) anisotropies are similar to those produced by weak lensing of the CMB: smoothing of the power spectrum, and generation of non-Gaussian features. Previous work considered the CIP effects on the CMB power-spectrum but neglected to include the CIP effects on estimates of the lensing potential power spectrum (though its contribution to the non-Gaussian, connected, part of the CMB trispectrum). Here, the CIP contribution to the standard estimator for the lensing potential power-spectrum is derived, and along with the CIP contributions to the CMB power-spectrum, Planck data is used to place limits on the root-mean-square CIP fluctuations on CMB scales, $\Delta_{\rm rms}^2(R_{\rm CMB})$. The resulting constraint of $\Delta_{\rm rms}^2(R_{\rm CMB}) < 4.3 \times 10^{-3}$ using this new technique improves on past work by a factor of $\sim 3$. We find that for Planck data our constraints almost reach the sensitivity of the optimal CIP estimator. The method presented here is currently the most sensitive probe of the amplitude of a scale-invariant CIP power spectrum placing an upper limit of $A_{\rm CIP}< 0.017$ at 95% CL. Future measurements of the large-scale CMB lensing potential power spectrum could probe CIP amplitudes as low as $\Delta_{\rm rms}^2(R_{\rm CMB}) = 8 \times 10^{-5}$ ($A_{\rm CIP} = 3.2 \times 10^{-4}$).

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#	sentence	role	the authors' own work	states the main conclusion	strength
s0	Compensated isocurvature perturbations (CIPs) are primordial fluctuations that balance baryon and dark-matter isocurvature to leave the total matter density unperturbed.	background 1.00	0.05	0.03	asserted 1.00
s1	The effects of CIPs on the cosmic microwave background (CMB) anisotropies are similar to those produced by weak lensing of the CMB: smoothing of the power spectrum, and generation of non-Gaussian features.	background 1.00	0.08	0.03	asserted 1.00
s2	Previous work considered the CIP effects on the CMB power-spectrum but neglected to include the CIP effects on estimates of the lensing potential power spectrum (though its contribution to the non-Gaussian, connected, part of the CMB trispectrum).	gap 1.00	0.06	0.03	asserted 1.00
s3	Here, the CIP contribution to the standard estimator for the lensing potential power-spectrum is derived, and along with the CIP contributions to the CMB power-spectrum, Planck data is used to place limits on the root-mean-square CIP fluctuations on CMB scales, $\Delta_{\rm rms}^2(R_{\rm CMB})$.	contribution 0.68	0.97	0.10	asserted 1.00
s4	The resulting constraint of $\Delta_{\rm rms}^2(R_{\rm CMB}) < 4.3 \times 10^{-3}$ using this new technique improves on past work by a factor of $\sim 3$.	result 0.99	0.94	0.47	asserted 1.00
s5	We find that for Planck data our constraints almost reach the sensitivity of the optimal CIP estimator.	interpretation 0.58	0.96	0.12	asserted 1.00
s6	The method presented here is currently the most sensitive probe of the amplitude of a scale-invariant CIP power spectrum placing an upper limit of $A_{\rm CIP}< 0.017$ at 95% CL.	result 0.60	0.90	0.63	asserted 1.00
s7	Future measurements of the large-scale CMB lensing potential power spectrum could probe CIP amplitudes as low as $\Delta_{\rm rms}^2(R_{\rm CMB}) = 8 \times 10^{-5}$ ($A_{\rm CIP} = 3.2 \times 10^{-4}$).	future work 0.98	0.41	0.07	hedged possibility 1.00

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Original abstract

Compensated isocurvature perturbations (CIPs) are primordial fluctuations that balance baryon and dark-matter isocurvature to leave the total matter density unperturbed. The effects of CIPs on the cosmic microwave background (CMB) anisotropies are similar to those produced by weak lensing of the CMB: smoothing of the power spectrum, and generation of non-Gaussian features. Previous work considered the CIP effects on the CMB power-spectrum but neglected to include the CIP effects on estimates of the lensing potential power spectrum (though its contribution to the non-Gaussian, connected, part of the CMB trispectrum). Here, the CIP contribution to the standard estimator for the lensing potential power-spectrum is derived, and along with the CIP contributions to the CMB power-spectrum, Planck data is used to place limits on the root-mean-square CIP fluctuations on CMB scales, $\Delta_{\rm rms}^2(R_{\rm CMB})$. The resulting constraint of $\Delta_{\rm rms}^2(R_{\rm CMB}) < 4.3 \times 10^{-3}$ using this new technique improves on past work by a factor of $\sim 3$. We find that for Planck data our constraints almost reach the sensitivity of the optimal CIP estimator. The method presented here is currently the most sensitive probe of the amplitude of a scale-invariant CIP power spectrum placing an upper limit of $A_{\rm CIP}< 0.017$ at 95% CL. Future measurements of the large-scale CMB lensing potential power spectrum could probe CIP amplitudes as low as $\Delta_{\rm rms}^2(R_{\rm CMB}) = 8 \times 10^{-5}$ ($A_{\rm CIP} = 3.2 \times 10^{-4}$).

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References

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Cited by 3 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

Probing correlated compensated isocurvature perturbations using scale-dependent galaxy bias
astro-ph.CO 2019-08 conditional novelty 6.0 of 10

kSZ tomography with future CMB and galaxy surveys could constrain correlated compensated isocurvature perturbations to sigma_A = 0.25, more than an order of magnitude better than galaxy surveys alone.
The galaxy power spectrum take on spatial curvature and cosmic concordance
astro-ph.CO 2020-10 conditional novelty 5.0 of 10

Planck plus the BOSS DR12 full-shape galaxy power spectrum gives a curvature parameter of 0.0023 ± 0.0028, flat to sub-percent precision, but only by combining two datasets that disagree at high significance when curv...
CMB-S4 Science Case, Reference Design, and Project Plan
astro-ph.IM 2019-07 unverdicted novelty 3.0 of 10

Presents the science case, reference design, and project plan for the CMB-S4 ground-based CMB experiment.

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19 arXiv papers cite this in 48 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 29 sentences without a confident label

Uses its method or tool 1 paper

Here we use the equivalent notation of Ref. [ref] .

Probing spatial variation of the fine-structure constant using the CMB · Off-diagonal correlations · 0.88

Uses its data or values 3 papers

By taking $R=R_CMB∼125 Mpc$ [ref] , the CMB constraints on the CIP variance imply [equation] where [equation]

Magnetic Fields from Compensated Isocurvature Perturbations · Compensated isocurvature perturbations · 0.88
In that case the upper limit on $A_CIP$ is dominated by large-scale CMB-anisotropy constraint, which with our convention[Ref. [ref] define $P_CIP(k) = A_CIP/k^3$ instead of our $2 π^2 A_CIP/k^3$] is $A_CIP ≤0.88 ×10^-3$ [ref] .

Magnetic fields from small-scale primordial perturbations · Comparison with Flitter et al. 2023 CITEMARK41Z · 0.95
In the main body of the paper we took half of the $2σ$ bound from Ref. [ref] , $|A| ≲360$, as a rough estimate of the typical constraining power of the CMB on uncorrelated CIP (cf. Fig. [ref]); the derivation of more precise bounds needs to take into account the fact that $Δ_rms^2(R_CMB)$ and $|A|$ have different probability density distributions.

Constraints on compensated isocurvature perturbations from BOSS DR12 galaxy data · Recent CMB constraints and forecasts · 0.91

Compares with it 1 paper

Our limits are consistent with much tighter limits on the compensated isocurvature modes considered in [ref] and [ref] , because we consider modes that exist only on very large, super-horizon scales.

Superhorizon isocurvature fluctuations relax tensions · Discussion & Conclusions · 1.00

Cites it as background 10 papers

Interestingly, however, there is a mode of isocurvature perturbations that largely escapes the constraining power of the CMB data; these are called compensated isocurvature perturbations (CIP) [ref] .

Compensated Isocurvature Perturbations in the Galaxy Power Spectrum · Introduction · 0.89
We now move to the case of the compensated isocurvature, often labelled CIP, for Compensated Isocurvature Perturbation [ref] .

The intrinsic bispectrum of the CMB from isocurvature initial conditions · Compensated isocurvature · 0.99
A few such probes of CIPs have been proposed so far, e.g. gas fraction of galaxy clusters [ref] , primordial non-Gaussianities [ref] and 21cm measurements [ref] (see Ref. [ref] for a more comprehensive review).

BAO Modulation as a Probe of Compensated Isocurvature Perturbations · Introduction · 0.91

What it cites · 71 sentences without a confident label

Contests 1 paper

When using the Planck estimates of the lensing power spectrum, Ref. [ref] neglects to include the CIP contribution to the estimator of the lensing-potential power spectrum.

Power Spectra Based Planck Constraints on Compensated Isocurvature, and Forecasts for LiteBIRD and CORE Space Missions · Past CMB bounds · contest 0.79

Uses the method or tool of 12 papers

The full analysis [ref] , which includes both CMB temperature and polarization maps, computes a minimum variance (mv) estimator from all possible CMB map auto- and cross-correlations, as discussed in detail in Appendix [ref] and [ref].

Planck 2015 results. XV. Gravitational lensing · CIPs and the CMB · 0.87
In the flat-sky approximation, a minimum-variance estimator for the weak-lensing deflection field, $d(L⃗) ≡√(L(L+1))ϕ(L⃗)$ can be built out of off-diagonal correlations of the CMB temperature fluctuations, and is [ref] [equation] where [equation] The lensing potential power spectrum is estimated from the expectation value of the estimator in Eq. [ref] [equation] where $πM/L$ is the angular coordinate of $L⃗$ and $B(L)$ are the standard Gaussian and non-Gaussian contributions to the full four-point correlation [ref] .

CMB Lensing Reconstruction on the Full Sky · CIPs and the CMB · 0.91
In the flat-sky approximation, a minimum-variance estimator for the weak-lensing deflection field, $d(L⃗) ≡√(L(L+1))ϕ(L⃗)$ can be built out of off-diagonal correlations of the CMB temperature fluctuations, and is [ref] [equation] where [equation] The lensing potential power spectrum is estimated from the expectation value of the estimator in Eq. [ref] [equation] where $πM/L$ is the angular coordinate of $L⃗$ and $B(L)$ are the standard Gaussian and non-Gaussian contributions to the full four-point correlation [ref] .

Mass Reconstruction with CMB Polarization · CIPs and the CMB · 0.91

Uses data or values from 4 papers

In this work we investigate constraints to compensated isocurvature perturbations (CIPs) using observations of the CMB made by the Planck satellite [ref] .

Planck 2015 results. I. Overview of products and scientific results · Introduction · 0.95
In addition to the temperature and polarization power spectra we use the Planck estimate of the lensing potential power spectrum [ref] .

Planck 2015 results. XV. Gravitational lensing · Constraints to CIPs from Planck measurements of the CMB · 0.99
Using tracers of the total matter and luminous matter on large scales ($R ∼100$ Mpc) Ref. [ref] found an upper limit of $A_CIP < 0.064$ which translates into $Δ_rms^2(R=100 Mpc) < 0.0165$.

Large scale distribution of total mass versus luminous matter from Baryon Acoustic Oscillations: First search in the SDSS-III BOSS Data Release 10 · Baryon-gas fraction bounds · 0.88

Compares with 1 paper

Our full analysis thus improves upon the constraint in Ref. [ref] by a factor of $∼3$.

Power Spectra Based Planck Constraints on Compensated Isocurvature, and Forecasts for LiteBIRD and CORE Space Missions · Past CMB bounds · 0.89

Cites as background 16 papers

The main effect of CIPs on the CMB is the spatial modulation in the photon/baryon sound speed [ref] .

Compensated isocurvature perturbations in the curvaton model · CIPs and the CMB · 0.81
Past work has concentrated on placing constraints on the CIP amplitude through off-diagonal contributions to the CMB four-point correlation function [ref] , smoothing of the small-scale CMB power spectra [ref] , fluctuations in the baryon fraction of galaxy clusters [ref] , spatial variation in the primordial deuterium to hydrogen (D/H) ratio measured in quasar absorption lines [ref] , and an additional offset between the large-scale distribution of total mass from luminous (i.e. baryonic) matter [ref] .

Power Spectra Based Planck Constraints on Compensated Isocurvature, and Forecasts for LiteBIRD and CORE Space Missions · Previous constraints to compensated isocurvature perturbations · 0.95
Past work has concentrated on placing constraints on the CIP amplitude through off-diagonal contributions to the CMB four-point correlation function [ref] , smoothing of the small-scale CMB power spectra [ref] , fluctuations in the baryon fraction of galaxy clusters [ref] , spatial variation in the primordial deuterium to hydrogen (D/H) ratio measured in quasar absorption lines [ref] , and an additional offset between the large-scale distribution of total mass from luminous (i.e. baryonic) matter [ref] .

Baryons do trace dark matter 380,000 years after the big bang: Search for compensated isocurvature perturbations with WMAP 9-year data · Previous constraints to compensated isocurvature perturbations · 0.95

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