Leverage on small-scale primordial non-Gaussianity through cross-correlations between CMB E-mode and μ-distortion anisotropies

Measurements of the cosmic microwave background (CMB) spectral distortions (SDs) will open a new window on the very early universe, providing new information complementary to that gathered from CMB temperature and polarization anisotropies. In this paper, we study their synergy as a function of the characteristics of the considered experiments. In particular, we examine a wide range of sensitivities for possible SD measurements, spanning from FIRAS up to noise levels 1000 times better than PIXIE, and study their constraining power when combined with current or future CMB anisotropy experiments such as Planck or LiteBIRD plus CMB-S4. We consider a number of different cosmological models such as the ΛCDM, as well as its extensions with the running of the scalar spectral index, the decay or the annihilation of dark matter (DM) particles. While upcoming CMB anisotropy experiments will be able to decrease the uncertainties on inflationary parameters such as As and ns by about a factor 2 in the ΛCDM case, we find that an SD experiment 100 times more sensitive than PIXIE (comparable to the proposed Super-PIXIE satellite) could potentially further contribute to constrain these parameters. This is even more significant in the case of the running of the scalar spectral index. Furthermore, as expected, constraints on DM particles decaying at redshifts probed by SDs will improve by orders of magnitude even with an experiment 10 times worse than PIXIE as compared to CMB anisotropies or Big Bang Nucleosynthesis bounds. On the contrary, DM annihilation constraints will not significantly improve over CMB anisotropy measurements. Finally, we forecast the constraints obtainable with sensitivities achievable either from the ground or from a balloon.

We study anisotropic (patchy) screening induced by the resonant conversion of cosmic microwave background (CMB) photons into dark-sector massive vector bosons (dark photons) as they cross non-linear large scale structure (LSS). Resonant conversion takes place through the kinetic mixing of the photon with the dark photon, one of the simplest low energy extensions to the Standard Model. In the early Universe, resonant conversion can occur when the photon plasma mass, obtained as the photon propagates through the ionized interstellar and intergalactic media, matches the dark photon mass. After the epoch of reionization, resonant conversion occurs mainly in the ionized gas that occupies virialized dark matter halos, for a range of dark photon masses between 10-13 eV ≲ m A' ≲ 10-11 eV. This leads to new CMB anisotropies that are correlated with LSS, which we refer to as patchy dark screening, in analogy with anisotropies from Thomson screening. Its unique frequency dependence allows it to be distinguished from the blackbody CMB. In this paper, we use a halo model approach to predict the imprint of dark screening on the CMB temperature and polarization anisotropies, as well as their correlation with LSS. We then examine the two- and three-point correlation functions of the dark-screened CMB, as well as correlation functions between CMB and LSS observables, to project the sensitivity of future measurements to the kinetic mixing parameter and dark photon mass. We demonstrate that an analysis with existing CMB data can improve upon current constraints on the kinetic mixing parameter by two orders of magnitude with the two-point correlation functions, while data from upcoming CMB experiments and LSS surveys can further improve the reach by another order of magnitude with two- and three-point correlation functions.

To reliably detect the cosmic microwave background (CMB) anisotropy is of great importance in understanding the birth and evolution of the Universe. One of the difficulties in CMB experiments is the domination of measured CMB anisotropy maps by the Doppler dipole moment from the motion of the antenna relative to the CMB. For each measured temperature the expected dipole component has to be calculated separately and then subtracted from the data. A small error in dipole direction, antenna pointing direction, sidelobe pickup contamination, and/or timing synchronism, can raise significant deviation in the dipole cleaned CMB temperature. After a full-sky observational scan, the accumulated deviations will be structured with a pattern closely correlated to the observation pattern with artificial anisotropies on large scales, including artificial quadrupole, octopole etc in the final CMB map. Such scan-induced anisotropies on large scales can be predicted by the true dipole moment and observational scan scheme. Indeed, the expected scan-induced quadrupole pattern of the WMAP mission is perfectly in agreement with the published WMAP quadrupole. With the scan strategy of the Planck mission, we predict that scan-induced anisotropies will also produce an artificially aligned quadrupole. The scan-induced anisotropy is a common problem for all sweep missions and, like the foreground emissions, has to be removed from observed maps. Without doing so, CMB maps from COBE, WMAP, and Planck as well, are not reliable for studying the CMB anisotropy.

After the sensational discovery of Cosmic Microwave Background (CMB) anisotropies by Differential Microwave Radiometer (DMR) boarded on the Cosmic Background Explore (COBE) (Smoot et al. 1992), the number of observational data of temperature fluctuations have been rapidly increasing (see e.g., White, Scott and Silk 1994) together with the understanding of physical processes of evolution of CMB anisotropies. Nowadays, CMB anisotropies are becoming one of the key observational object in the modern cosmology. CMB anisotropies provide us direct information at last scattering surface, i.e., redshift z ≈ 1000. Since the shape of the angular power spectrum of CMB anisotropies is highly sensitive to geometry of the universe, cosmological models and cosmological parameters, i.e., density parameter Ω0, Hubble constant h which is normalized by 100km/s/Mpc, cosmological constant Λ, baryon density ΩB and so on, CMB anisotropies are expected to be a new tool to understand our universe. Moreover, we can obtain information of thermal history of the universe after recombination (through the formation of secondary fluctuations and damping of primary fluctuations), physics of clusters of galaxies (through the Sunyaev-Zeldovich effect) and non-linear structure of the universe (through the gravitational lensing effect) from CMB anisotropies.

We examine the Planck 2015 cosmic microwave background (CMB) anisotropy data by using a physically consistent energy density inhomogeneity power spectrum generated by quantum-mechanical fluctuations during an early epoch of inflation in the non-flat XCDM model. Here dark energy is parameterized using a fluid with a negative equation of state parameter but with the speed of fluid acoustic inhomogeneities set to the speed of light. We find that the Planck 2015 data in conjunction with baryon acoustic oscillation distance measurements are reasonably well fit by a closed-XCDM model in which spatial curvature contributes a percent of the current cosmological energy density budget. In this model, the measured non-relativistic matter density parameter and Hubble constant are in good agreement with values determined using most other data. Depending on cosmological parameter values, the closed-XCDM model has reduced power, relative to the tilted, spatially flat ΛCDM case, and can partially alleviate the low multipole CMB temperature anisotropy deficit and can help partially reconcile the CMB anisotropy and weak lensing σ 8 constraints, at the expense of somewhat worsening the fit to higher multipole CMB temperature anisotropy data. However, the closed-XCDM inflation model does not seem to improve the agreement much, if at all, compared to the closed ΛCDM inflation case, even though it has one additional free parameter.

The cosmic microwave background (CMB) anisotropies in spherical 3-spaces with a non-trivial topology are studied. This paper discusses the special class of the so-called double-action manifolds, which are for the first time analysed with respect to their CMB anisotropies. The CMB anisotropies are computed for all prism double-action manifolds generated by a binary dihedral and a cyclic group with a group order of up to 180 leading to 33 different topologies. Several spaces are found which show a suppression of the CMB anisotropies on large angular distances as it is found on the real CMB sky. It turns out that two of these spaces possess Dirichlet domains which are not very far from highly symmetric polyhedra like Platonic or Archimedean ones.

Observations of the Cosmic Microwave Background (CMB) play a pivotal role in the development of modern cosmology. Most of the predictions of the Hot Big Bang model are now experimentally confirmed, and the parameters of the model have recently been constrained to good accuracy. The so-called Concordance cosmology, derived from observations of the CMB spectrum and anisotropy, from measurements of the large-scale distribution of galaxies, of the expansion of the Universe and of the abundance of light elements, requires significant contributions from dark matter (Ω m ∼ 0.3) and dark energy (Ω Λ ∼ 0.65). Also, an initial inflation phase is required for the model to be self consistent. Here we focus on CMB anisotropy and CMB polarization observations and on their role in constraining the model.

We combine COBE-DMR measurements of cosmic microwave background (CMB) anisotropy with a recent measurement of the mass power spectrum at redshift z = 2.5 from Lyα forest data to derive constraints on cosmological parameters and test the inflationary cold dark matter (CDM) scenario of structure formation. By treating the inflationary spectral index n as a free parameter, we are able to find successful fits to the COBE and Lyα forest constraints in Ωm = 1 models with and without massive neutrinos and in low-Ωm models with and without a cosmological constant. Within each class of model, the combination of COBE and the Lyα forest P(k) constrains, with different indices for each case. This new constraint breaks some of the degeneracies in cosmological parameter determinations from other measurements of large scale structure and CMB anisotropy. The Lyα forest P(k) provides the first measurement of the slope of the linear mass power spectrum on ∼ Mpc scales, ν = −2.25 ± 0.18, and it confirms a basic prediction of the inflationary CDM scenario: an approximately scale-invariant spectrum of primeval fluctuations (n ≈ 1) modulated by a transfer function that bends P(k)

In the context of a cold big bang (CBB) cosmological model, I estimate the temperature, calculate the evolution, and discuss the anisotropies of a homogeneous radiation background emitted at high redshift by Population III objects and thermalized by a mixture of carbon/silicate dust and iron or carbon whiskers. Assuming that Population III objects supply dark matter remnants and produce the universal helium abundance of ~24%, the resulting radiation, if thermal, should have temperature 0.5 K T0 9 K. To calculate its thermalization I limit standard dust density using constraints from maximum allowed metallicity, quasar reddening, Type Ia supernova observations, and high-redshift object visibility and assume a small mass ratio of whiskers to standard dust. For high redshift of generation (zi 100) and highly conducting, high aspect ratio (length/diameter 1000) iron whiskers, the final spectrum meets the FIRAS spectral distortion limits and does not exceed limits on IR-background light. Energetic considerations probably require zi 40Ωb if the observed cosmic microwave background (CMB) is star generated. Such a model is marginally viable with baryon density Ωb = 1, but probably ruled out if Ωb 0.5. I comment briefly on possible other thermalization mechanisms. In whisker-thermalized models, CMB anisotropies are imprinted at lower redshift and through somewhat different physical processes than in the hot big bang (HBB). Nonlocal thermal equilibrium of the dust causes the Sachs-Wolfe effect to disappear on small angular scales. Radiation pressure probably ejects whiskers from luminous regions such as galaxies. If significant intergalactic magnetic fields are absent, CMB radiation drag probably fixes whiskers in the CMB frame, hence large-scale Doppler anisotropies (other than the dipole) do not exist. Intrinsic temperature fluctuations and the integrated Sachs-Wolfe effect operate essentially as in the HBB. Numerical results for the horizon, diffusion, and other length scales relevant to CMB anisotropies for fiducial thermalization models are provided. Finally, I note that CMB polarization may be higher in the whisker model than in the HBB and that acoustic oscillations should not appear in the CBB power spectrum, and I comment on the amplitude and possible frequency dependence of the anisotropies.

Recently, BICEP2 measurements of the cosmic microwave background (CMB)\n$B$-mode polarization at degree angular scales has indicated the presence of\ntensor modes with a high tensor-to-scalar ratio of $r=0.2$ when assuming nearly\nscale-invariant tensor and scalar spectra, although the signal may be\ncontaminated by dust emission as implied by the recent {\\em Planck}\npolarization data. This result is in conflict with the {\\em Planck} best-fit\nLambda Cold Dark Model with $r<0.11$. Due to the fact that inflaton has to be\ninteracting with other fields so as to convert its potential energy into\nradiation to reheat the Universe, the interacting inflaton may result in a\nsuppression of the scalar spectrum at large scales. This suppression has been\nused to explain the observed low quadrupole in the CMB anisotropy. In this\npaper, we show that a combination of the tensor modes measured by BICEP2 and\nthe large-scale suppressed scalar modes contributes to the CMB anisotropy in\nsuch a way that the resultant CMB anisotropy and polarization power spectra are\nconsistent with both {\\em Planck} and BICEP2 data. We also project our findings\nto cases in which $r$ may become reduced in future CMB polarization\nmeasurements.\n

view Abstract Citations (60) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Search for Small-Scale Anisotropy in the Cosmic Microwave Background Tucker, G. S. ; Griffin, G. S. ; Nguyen, H. T. ; Peterson, J. B. Abstract We report the preliminary result of a search for cosmic microwave background (CMB) anisotropy. We made observations using a specially designed radiometer and on-axis Cassegrain telescope. The beam size was 12' at a frequency of 90 GHz. Observations were made during 1993 January from the South Pole. We observed five regions of sky near declination -75^deg^, and set a 95% confidence level upper limit of {DELTA}T < 2.3 x 10^-5^T_CMB_ on Gaussian-correlated CMB anisotropy at an angular scale of 0.15^deg^. This is the lowest upper limit to date on CMB anisotropy at this angular scale. Publication: The Astrophysical Journal Pub Date: December 1993 DOI: 10.1086/187133 Bibcode: 1993ApJ...419L..45T Keywords: COSMOLOGY: COSMIC MICROWAVE BACKGROUND; COSMOLOGY: OBSERVATIONS full text sources ADS |

We study the complementarity between the cosmological information obtainable with the Planck Surveyor and the large-scale structure (LSS) redshift surveys in Λ cold+hot dark matter (ΛCHDM) cosmologies. We compute the initial full phase-space neutrino distribution function for ΛCHDM models by using numerical simulations. As initial conditions, we adopt the HDM density fluctuation power spectrum normalized on the basis of the analysis of the local cluster X-ray temperature function and derive the initial neutrino phase-space distribution at each spatial wavenumber k by using the Zel'dovich approximation. These initial neutrino phase-space distributions are implemented in the CMBFAST code for the integration of the coupled linearized Einstein, Boltzmann, and fluid equations in k-space. We find that the relative bias between the cosmic microwave background (CMB) temperature fluctuations and the underlying matter density fluctuation power spectrum in COBE Differential Microwave Radiometer normalization is given by the CDM component normalized according to the abundance of rich clusters at the present time. We use the Fisher information matrix approximation to constrain a multidimensional parameterization of the ΛCHDM model by jointly considering CMB and large-scale structure data according to the Planck and the Sloan Digital Sky Survey experimental specifications and by taking into account redshift distortions and nonlinear effects on the matter power spectrum. We found that, although the CMB anisotropy and polarization measurements tend to dominate the constraints on most of the cosmological parameters, the additional small-scale LSS data help to break the parameter degeneracies. This work has been done in the framework of the Planck Low Frequency Instrument activities.

We study the cosmic microwave background (CMB) anisotropy due to spherically symmetric nonlinear structures in flat universes with dust and a cosmological constant. By modeling a time-evolving spherical compensated void/lump by Lemaitre-Tolman-Bondi spacetimes, we numerically solve the null geodesic equations with the Einstein equations. We find that a nonlinear void redshifts the CMB photons that pass through it regardless of the distance to it. In contrast, a nonlinear lump blueshifts (or redshifts) the CMB photons if it is located near (or sufficiently far from) us. The present analysis comprehensively covers previous works based on a thin-shell approximation and a linear/second-order perturbation method and the effects of shell thickness and full nonlinearity. Our results indicate that, if quasilinear and large ($\ensuremath{\gtrsim}100\text{ }\text{ }\mathrm{Mpc}$) voids/lumps would exist, they could be observed as cold or hot spots with temperature variance $\ensuremath{\gtrsim}{10}^{\ensuremath{-}5}\text{ }\text{ }\mathrm{K}$ in the CMB sky.

Astrophysical magnetic fields decay primarily via two processes, namely ambipolar diffusion and turbulence. Constraints on the strength and the spectral index of nonhelical magnetic fields have been derived earlier in the literature through the effect of the above-mentioned processes on the cosmic microwave background (CMB) radiation. A helical component of the magnetic field is also produced in various models of magnetogenesis, which can explain larger coherence length magnetic field. In this study, we focus on studying the effects of post-recombination decay of maximally helical magnetic fields through ambipolar diffusion and decaying magnetic turbulence and the impact of this decay on CMB. We find that helical magnetic fields lead to changes in the evolution of baryon temperature and ionization fraction which in turn lead to modifications in the CMB temperature and polarization anisotropy. These modifications are different from those arising due to nonhelical magnetic fields with the changes dependent on the strength and the spectral index of the magnetic field power spectra.

One of the major goals of future cosmic microwave background (CMB) B-mode polarization experiments is the detection of primordial gravitational waves through an unbiased measurement of the tensor-to-scalar ratio r. Robust detection of this signal will require mitigating all possible contamination to the B-mode polarization from astrophysical origins. One such extragalactic contamination arises from the patchiness in the electron density during the reionization epoch. Along with the signature on CMB polarization, the patchy reionization can source secondary anisotropies on the CMB temperature through the kinetic Sunyaev–Zeldovich (kSZ) effect. In order to study the impact of this foreground for the upcoming CMB missions, we present a self-consistent framework to compute the CMB anisotropies based on a physically motivated model of reionization. We show that the value of r can bias towards a higher value if the secondary contribution from reionization is neglected. However, combining small-scale kSZ signal, large-scale E-mode polarization, and B-mode polarization measurements, we can put constraints on the patchiness in electron density during reionization and can mitigate its impact on the value of r. CMB missions such as CMB-S4 and PICO may experience a bias of &amp;gt;0.17σ which can go as high as ∼0.73σ for extreme reionization models allowed by the Planck and SPT CMB measurements. As future experiments target to measure r at 5σ, this is likely to affect the measurement significance and hence possibly affect the claim of detection of r, if not mitigated properly by using joint estimations of different reionization observables.