Cosmic Microwave Background Anisotropy Data Research Articles

Cosmic Reionization in the JWST Era: Back to AGNs?

Deep surveys with the James Webb Space Telescope (JWST) have revealed an emergent population of moderate-luminosity, broad-line active galactic nuclei (AGNs) at 4 ≲ z ≲ 13 powered by accretion onto early massive black holes. The high number densities reported, together with the large Lyman-continuum (LyC) production efficiency and leakiness into the intergalactic medium that are typical of UV-selected AGNs, lead us to reassess a scenario where AGNs are the sole drivers of the cosmic hydrogen/helium reionization process. Our approach is based on the assumptions, grounded in recent observations, that (a) the fraction of broad-line AGNs among galaxies is around 10%–15%; (b) the mean escape fraction of hydrogen LyC radiation is high, at ≳80%, in AGN hosts and is negligible otherwise; and (c) internal absorption at 4 ryd or a steep ionizing EUV spectrum delay full reionization of He ii until z ≃ 2.8–3.0, in agreement with observations of the He ii Lyα forest. In our fiducial models, (1) hydrogen reionization is 99% completed by redshift z ≃ 5.3–5.5 and reaches its midpoint at z ≃ 6.5–6.7; (2) the integrated Thomson scattering optical depth to reionization is ≃0.05, consistent with constraints from cosmic microwave background anisotropy data; and (3) the abundant AGN population detected by JWST does not violate constraints on the unresolved X-ray background.

Deep Photometry of Suspected Gravitational Lensing Events: Potential Detection of a Cosmic String

Cosmic strings (CS) are one-dimensional cosmological-size objects predicted in realistic models of the early Universe. Analysis of the cosmic microwave background (CMB) anisotropy data from the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck surveys revealed several CS candidates. One of the candidates, CSc-1, was found to be most reliable because of the statistically significant chains of gravitational lensing (GL) candidates in its field. We observed the brightest of the objects in the CSc-1 field, a galaxy pair SDSSJ110429.61+233150.3. The significant correlation between the spectra of the two components indicates the possible GL nature of the pair. Our simulations of observational data in the CSc-1 field shows that a large number of pairs can be explained by the complex geometry of the CS. Simulations of the SDSSJ110429 galaxy pair has shown that the observed angle between the components of the pair can be explained if the CS is strongly inclined and, possibly, bent in the image plane. In our preliminary data, we also detected the sign of the sharp isophotal edge in one image, which along with CMB and spectral data strongly suggests the possibility of a CS detection.

H0=69.8±1.3 km s−1 Mpc−1 , Ωm0=0.288±0.017 , and other constraints from lower-redshift, non-CMB, expansion-rate data

We use updated Type Ia Pantheon+ supernova, baryon acoustic oscillation, and Hubble parameter (now also accounting for correlations) data, as well as new reverberation-measured C IV quasar data, and quasar angular size, H II starburst galaxy, reverberation-measured Mg II quasar, and Amati-correlated gamma-ray burst data to constrain cosmological parameters. We show that these data sets result in mutually consistent constraints and jointly use them to constrain cosmological parameters in six different spatially-flat and non-flat cosmological models. Our analysis provides summary model-independent determinations of two key cosmological parameters: the Hubble constant, $H_0=69.8\pm1.3$ $\rm{km \ s^{-1} \ Mpc^{-1}}$, and the current non-relativistic matter density parameter, $\Omega_{m0}=0.288\pm0.017$. Our summary error bars are 2.4 and 2.3 times those obtained using the flat $\Lambda$CDM model and Planck TT,TE,EE+lowE+lensing cosmic microwave background (CMB) anisotropy data. Our $H_0$ value is very consistent with that from the local expansion rate based on the Tip of the Red Giant Branch data, is 2$\sigma$ lower than that from the local expansion rate based on Type Ia supernova and Cepheid data, and is 2$\sigma$ higher than that in the flat $\Lambda$CDM model based on Planck TT,TE,EE+lowE+lensing CMB data. Our data compilation shows at most mild evidence for non-flat spatial hypersurfaces, but more significant evidence for dark energy dynamics, 2$\sigma$ or larger in the spatially-flat dynamical dark energy models we study.

Primordial standard clock models and CMB residual anomalies

The residuals of the power spectra of WMAP and Planck's cosmic microwave background (CMB) anisotropies data are known to exhibit a few interesting anomalies at different scales with marginal statistical significance. Combining bottom-up and top-down model-building approaches and using a pipeline that efficiently compares model predictions with data, we construct a model of primordial standard clock that is able to link and address the anomalies at both the large and small scales. This model, and its variant, provide some of the best fits to the feature anomalies in CMB. According to Bayes evidences, these models are currently statistically indistinguishable from the Standard Model. We show that the difference between them will soon become statistically significant with various higher quality data on the CMB polarization. We demonstrate that such a model-building and data-analyses process may be used to uncover a portion of detailed evolutionary history of our universe during its primordial epoch.

Using lower-redshift, non-CMB, data to constrain the Hubble constant and other cosmological parameters

Abstract We use updated Hubble parameter and baryon acoustic oscillation data, as well as other lower-redshift Type Ia supernova, Mg ii reverberation-measured quasar, quasar angular size, H ii starburst galaxy, and Amati-correlated gamma-ray burst data, to jointly constrain cosmological parameters in six cosmological models. The joint analysis provides model-independent determinations of the Hubble constant, H0 = 69.7 ± 1.2 $\rm {km \ s^{-1} \ Mpc^{-1}}$, and the current non-relativistic matter density parameter, Ωm0 = 0.295 ± 0.017. These error bars are factors of 2.2 and 2.3 larger than the corresponding error bars in the flat ΛCDM model from Planck TT,TE,EE+lowE+lensing cosmic microwave background anisotropy data. Based on the deviance information criterion (DIC), the flat ΛCDM model is most favored but mild dark energy dynamics and a little spatial curvature are not ruled out.

Cosmological search for sterile neutrinos after Planck 2018

Sterile neutrinos can affect the evolution of the universe, and thus using the cosmological observations can search for sterile neutrinos. In this work, we use the cosmic microwave background anisotropy data from the Planck 2018 release, combined with the latest baryon acoustic oscillation, type Ia supernova, and Hubble constant data, to constrain the cosmological models with considering sterile neutrinos. In order to test the influences of the properties of dark energy on the results of searching for sterile neutrinos, in addition to the Λ cold dark matter (ΛCDM) model, we also consider the wCDM model and the holographic dark energy (HDE) model. We find that the existence of sterile neutrinos is not preferred when the H0 local measurement is not included in the data combination. When the H0 measurement is included in the joint constraints, it is found that ΔNeff>0 is favored at about 2.7σ level for the ΛCDM model and at about 1–1.7σ level for the wCDM model. However, mν,sterileeff still cannot be well constrained and only upper limits can be given. In addition, we find that the HDE model is definitely ruled out by the current data. We also discuss the issue of the Hubble tension, and we conclude that involving sterile neutrinos in the cosmological models cannot truly resolve the Hubble tension.

Unfinished fabric of the three neutrino paradigm

In the current $3\ensuremath{\nu}$ paradigm, neutrino flavor oscillations probe three mixing angles $({\ensuremath{\theta}}_{12},{\ensuremath{\theta}}_{23},{\ensuremath{\theta}}_{13})$, one $CP$-violating phase $\ensuremath{\delta}$, and two independent differences between the squared masses ${m}_{i}^{2}$, that can be chosen as $\ensuremath{\delta}{m}^{2}={m}_{2}^{2}\ensuremath{-}{m}_{1}^{2}>0$ and $\mathrm{\ensuremath{\Delta}}{m}^{2}={m}_{3}^{2}\ensuremath{-}({m}_{1}^{2}+{m}_{2}^{2})/2$, where $\mathrm{sign}(\mathrm{\ensuremath{\Delta}}{m}^{2})=+(\ensuremath{-})$ for normal (inverted) mass ordering. Absolute $\ensuremath{\nu}$ masses can be probed by the effective mass ${m}_{\ensuremath{\beta}}$ in beta decay, by the total mass $\mathrm{\ensuremath{\Sigma}}$ in cosmology and---if neutrinos are Majorana---by another effective mass ${m}_{\ensuremath{\beta}\ensuremath{\beta}}$ in neutrinoless double beta decay. Within an updated global analysis of oscillation and nonoscillation data, we constrain these $3\ensuremath{\nu}$ parameters, both separately and in selected pairs, and highlight the concordance or discordance among different constraints. Five oscillation parameters $(\ensuremath{\delta}{m}^{2},|\mathrm{\ensuremath{\Delta}}{m}^{2}|,{\ensuremath{\theta}}_{12},{\ensuremath{\theta}}_{23},{\ensuremath{\theta}}_{13})$ are consistently measured, with an overall accuracy ranging from $\ensuremath{\sim}1%$ for $|\mathrm{\ensuremath{\Delta}}{m}^{2}|$ to $\ensuremath{\sim}6%$ for ${\mathrm{sin}}^{2}{\ensuremath{\theta}}_{23}$ (due to its persisting octant ambiguity). We find overall hints for normal ordering (at $\ensuremath{\sim}2.5\ensuremath{\sigma}$), as well as for ${\ensuremath{\theta}}_{23}<\ensuremath{\pi}/4$ and for $\mathrm{sin}\ensuremath{\delta}<0$ (both at 90% C.L.), and discuss some tensions among different datasets. Concerning nonoscillation data, we include the recent KATRIN constraints on ${m}_{\ensuremath{\beta}}$, and we combine the latest $^{76}\mathrm{Ge}$, $^{130}\mathrm{Te}$ and $^{136}\mathrm{Xe}$ bounds on ${m}_{\ensuremath{\beta}\ensuremath{\beta}}$, accounting for nuclear matrix element covariances. We also discuss some variants related to cosmic microwave background (CMB) anisotropy and lensing data, which may affect cosmological constraints on $\mathrm{\ensuremath{\Sigma}}$ and hints on $\mathrm{sign}(\mathrm{\ensuremath{\Delta}}{m}^{2})$. The default option, including all Planck results, irrespective of the so-called lensing anomaly, sets upper bounds on $\mathrm{\ensuremath{\Sigma}}$ at the level of $\ensuremath{\sim}{10}^{\ensuremath{-}1}\text{ }\text{ }\mathrm{eV}$, and further favors normal ordering up to $\ensuremath{\sim}3\ensuremath{\sigma}$. An alternative option, that includes recent ACT results plus other independent results (from WMAP and selected Planck data) globally consistent with standard lensing, is insensitive to the ordering but prefers $\mathrm{\ensuremath{\Sigma}}\ensuremath{\sim}\mathrm{few}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}1}\text{ }\text{ }\mathrm{eV}$, with different implications for ${m}_{\ensuremath{\beta}}$ and ${m}_{\ensuremath{\beta}\ensuremath{\beta}}$ searches. In general, the unfinished fabric of the $3\ensuremath{\nu}$ paradigm appears to be at the junction of diverse searches in particle and nuclear physics, astrophysics and cosmology, whose convergence will be crucial to achieve a convincing completion.

Hyrec-2: A highly accurate sub-millisecond recombination code

We present the new recombination code hyrec-2, which achieves the same accuracy as the state-of-the-art codes hyrec and cosmorec and, at the same time, surpasses the computational speed of the code recfast commonly used for cosmic microwave background (CMB) anisotropy data analyses. hyrec-2 is based on an effective four-level atom model, accounting exactly for the nonequilibrium of highly excited states of hydrogen, and very accurately for radiative transfer effects with a correction to the Lyman-$\ensuremath{\alpha}$ escape rate. The latter is computed with the original hyrec and tabulated as a function of temperature, along with its derivatives with respect to the relevant cosmological parameters. This enables the code to keep the same accuracy as the original hyrec over the full 99.7% confidence region of cosmological parameters currently allowed by Planck, while running in under one millisecond on a standard laptop. Our code leads to no noticeable bias in any cosmological parameters even in the case of an ideal cosmic-variance-limited experiment up to $\ensuremath{\ell}=5000$. Beyond CMB anisotropy calculations, hyrec-2 will be a useful tool to compute various observables that depend on the recombination and thermal history, such as the recombination spectrum or the 21-cm signal.

Extended reionization in models beyond ΛCDM with Planck 2018 data

We provide an update on the constraints on extended reionization histories with the Planck 2018 cosmic microwave background anisotropy data. The Planck 2018 data on large angular scales improve the measurement of the E-mode polarization reionization bump at low multipoles providing the possibility to improve our previous results [1]. Using a minor modification to the original Poly-reion model [2] for the reionization history, we find that the Planck 2018 data significantly improve all our previous results: we find as optical depth of τ=0.0572−0.0075+0.0064 at 68% CL, that early onsets of reionization are strongly disfavoured, i.e. redshift when the reionization begins, zxe=0=18.18−10.89 +1.61 at 68% CL, and that reionization duration (defined between 10% and 99% reionization) is significantly reduced, i.e. ΔzReion=4.59−2.45+1.67 at 68% CL . We explore possible correlations between reionization histories and cosmological parameters, including important extensions beyond ΛCDM . We find that the degeneracy between reionization and scalar spectral index, neutrino mass sum, spatial curvature, dark matter annihilation and other non-standard models are significantly reduced.The reduction of the error bars and the degeneracies, together with the shift towards lower values of the optical depth that we observe in the Poly-reion model are mainly driven by the new low-ℓ polarization likelihood of Planck 2018 baseline based on the HFI data. This is confirmed also by the results derived without this likelihood and the ones with different alternatives to the baseline that are presented for a subset of models.

Sensitivity forecasts for the cosmological recombination radiation in the presence of foregrounds

ABSTRACT The cosmological recombination radiation (CRR) is one of the inevitable Lambda cold dark matter 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 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 SuperPIXIE. However, for a real exploitation of the cosmological information, an ≃ 50 times more sensitive spectrometer is required. While extremely futuristic, this could provide independent constraints on the primordial helium abundance, Yp, 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 ≃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 Yp and Neff 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.

Using quasar X-ray and UV flux measurements to constrain cosmological model parameters

ABSTRACT Risaliti and Lusso have compiled X-ray and UV flux measurements of 1598 quasars (QSOs) in the redshift range 0.036 ≤ z ≤ 5.1003, part of which, z ∼ 2.4 − 5.1, is largely cosmologically unprobed. In this paper we use these QSO measurements, alone and in conjunction with baryon acoustic oscillation (BAO) and Hubble parameter [H(z)] measurements, to constrain cosmological parameters in six different cosmological models, each with two different Hubble constant priors. In most of these models, given the larger uncertainties, the QSO cosmological parameter constraints are mostly consistent with those from the BAO + H(z) data. A somewhat significant exception is the non-relativistic matter density parameter Ωm0 where QSO data favour Ωm0 ∼ 0.5 − 0.6 in most models. As a result, in joint analyses of QSO data with H(z) + BAO data the 1D Ωm0 distributions shift slightly towards larger values. A joint analysis of the QSO + BAO + H(z) data is consistent with the current standard model, spatially-flat ΛCDM, but mildly favours closed spatial hypersurfaces and dynamical dark energy. Since the higher Ωm0 values favoured by QSO data appear to be associated with the z ∼ 2 − 5 part of these data, and conflict somewhat with strong indications for Ωm0 ∼ 0.3 from most z < 2.5 data as well as from the cosmic microwave background anisotropy data at z ∼ 1100, in most models, the larger QSO data Ωm0 is possibly more indicative of an issue with the z ∼ 2 − 5 QSO data than of an inadequacy of the standard flat ΛCDM model.

Constraints on active and sterile neutrinos in an interacting dark energy cosmology

We investigate the impacts of dark energy on constraining massive (active/sterile) neutrinos in interacting dark energy (IDE) models by using the current observations. We employ two typical IDE models, the interacting $w$ cold dark matter (I$w$CDM) model and the interacting holographic dark energy (IHDE) model, to make an analysis. To avoid large-scale instability, we use the parameterized post-Friedmann approach to calculate the cosmological perturbations in the IDE models. The cosmological observational data used in this work include the Planck cosmic microwave background (CMB) anisotropies data, the baryon acoustic oscillation data, the type Ia supernovae data, the direct measurement of the Hubble constant, the weak lensing data, the redshift-space distortion data, and the CMB lensing data. We find that the dark energy properties could influence the constraint limits of active neutrino mass and sterile neutrino parameters in the IDE models. We also find that the dark energy properties could influence the constraints on the coupling strength parameter $\beta$, and a positive coupling constant, $\beta>0$, can be detected at the $2.5\sigma$ statistical significance for the IHDE+$\nu_s$ model by using the all-data combination. In addition, we also discuss the "Hubble tension" issue in these scenarios. We find that the $H_0$ tension can be effectively relieved by considering massive sterile neutrinos, and in particular in the IHDE+$\nu_s$ model the $H_0$ tension can be reduced to be at the $1.28\sigma$ level.

Prospects for improving cosmological parameter estimation with gravitational-wave standard sirens from Taiji

Taiji, a space-based gravitational-wave observatory, consists of three satellites forming an equilateral triangle with arm length of 3×106 km, orbiting around the Sun. Taiji is able to observe the gravitational-wave standard siren events of massive black hole binary (MBHB) merger, which is helpful in probing the expansion of the universe. In this paper, we preliminarily forecast the capability of Taiji for improving cosmological parameter estimation with the gravitational-wave standard siren data. We simulate five-year standard siren data based on three fiducial cosmological models and three models of MBHB's formation and growth. It is found that the standard siren data from Taiji can effectively break the cosmological parameter degeneracies generated by the cosmic microwave background (CMB) anisotropies data, especially for dynamical dark energy models. The constraints on cosmological parameters are significantly improved by the data combination CMB + Taiji, compared to the CMB data alone. Compared to the current optical cosmological observations, Taiji can still provide help in improving the cosmological parameter estimation to some extent. In addition, we consider an ideal scenario to investigate the potential of Taiji on constraining cosmological parameters. We conclude that the standard sirens of MBHB from Taiji will become a powerful cosmological probe in the future.

Planck 2015 constraints on spatially-flat dynamical dark energy models

We determine constraints on spatially-flat tilted dynamical dark energy XCDM and $\phi $CDM inflation models by analyzing Planck 2015 cosmic microwave background (CMB) anisotropy data and baryon acoustic oscillation (BAO) distance measurements. XCDM is a simple and widely used but physically inconsistent parameterization of dynamical dark energy, while the $\phi $CDM model is a physically consistent one in which a scalar field $\phi $ with an inverse power-law potential energy density powers the currently accelerating cosmological expansion. Both these models have one additional parameter compared to standard $\varLambda $CDM and both better fit the TT + lowP + lensing + BAO data than does the standard tilted flat-$\varLambda $CDM model, with $\Delta \chi ^{2} = -1.26\ (-1.60)$ for the XCDM ($\phi $CDM) model relative to the $\varLambda $CDM model. While this is a 1.1$\sigma $ (1.3$\sigma $) improvement over standard $\varLambda $CDM and so not significant, dynamical dark energy models cannot be ruled out. In addition, both dynamical dark energy models reduce the tension between the Planck 2015 CMB anisotropy and the weak lensing $\sigma _{8}$ constraints.

Using the Tilted flat-ΛCDM and the Untilted Non-flat ΛCDM Inflation Models to Measure Cosmological Parameters from a Compilation of Observational Data

Abstract We use the physically consistent tilted spatially flat and untilted non-flat ΛCDM inflation models to constrain cosmological parameter values with the Planck 2015 cosmic microwave background (CMB) anisotropy data and recent SNe Ia measurements, baryonic acoustic oscillations (BAO) data, growth rate observations, and Hubble parameter measurements. The most dramatic consequence of including the four non-CMB data sets is the significant strengthening of the evidence for non-flatness in the non-flat ΛCDM model, from 1.8σ for the CMB data alone to 5.1σ for the full data combination. The BAO data is the most powerful of the non-CMB data sets in more tightly constraining model-parameter values and in favoring a spatially closed universe in which spatial curvature contributes about a percent to the current cosmological energy budget. The untilted non-flat ΛCDM model better fits the large-angle CMB temperature anisotropy angular spectrum and is more consistent with the Dark Energy Survey constraints on the current value of the rms amplitude of mass fluctuations (σ 8) as a function of the current value of the nonrelativistic matter-density parameter (Ω m ) but does not provide as good a fit to the smaller-angle CMB temperature anisotropy data, as does the tilted flat-ΛCDM model. Some measured cosmological parameter values differ significantly between the two models, including the reionization optical depth and the baryonic matter density parameter, both of whose 2σ ranges (in the two models) are disjointed or almost so.

Measuring the Hubble constant and spatial curvature from supernova apparent magnitude, baryon acoustic oscillation, and Hubble parameter data

Cosmic microwave background (CMB) anisotropy (spatial inhomogeneity) data provide the tightest constraints on the Hubble constant, matter density, spatial curvature, and dark energy dynamics. Other data, sensitive to the evolution of only the spatially homogeneous part of the cosmological model, such as Type Ia supernova apparent magnitude, baryon acoustic oscillation distance, and Hubble parameter measurements, can be used in conjunction with the CMB data to more tightly constrain parameters. Recent joint analyses of CMB and such non-CMB data indicate that slightly closed spatial hypersurfaces are favored in nonflat untilted inflation models and that dark energy dynamics cannot be ruled out, and favor a smaller Hubble constant. We show that the constraints that follow from these non-CMB data alone are consistent with those that follow from the CMB data alone and so also consistent with, but weaker than, those that follow from the joint analyses of the CMB and non-CMB data.

Observational constraints on the tilted flat-XCDM and the untilted nonflat XCDM dynamical dark energy inflation parameterizations

We constrain tilted spatially-flat and untilted nonflat XCDM dynamical dark energy inflation parameterizations using Planck 2015 cosmic microwave background (CMB) anisotropy data and recent baryonic acoustic oscillations distance measurements, Type Ia supernovae data, Hubble parameter observations, and growth rate measurements. Inclusion of the four non-CMB data sets results in a significant strengthening of the evidence for nonflatness in the nonflat XCDM model from 1.1$\sigma$ for the CMB data alone to 3.4$\sigma$ for the full data combination. In this untilted nonflat XCDM case the data favor a spatially-closed model in which spatial curvature contributes a little less than a percent of the current cosmological energy budget; they also mildly favor dynamical dark energy over a cosmological constant at 1.2$\sigma$. These data are also better fit by the flat-XCDM parameterization than by the standard $\Lambda$CDM model, but only at 0.3$\sigma$ significance. Current data is unable to rule out dark energy dynamics. The nonflat XCDM parameterization is compatible with the Dark Energy Survey limits on the present value of the rms mass fluctuations amplitude ($\sigma_8$) as a function of the present value of the nonrelativistic matter density parameter ($\Omega_m$), however it does not provide as good a fit to the higher multipole CMB temperature anisotropy data as does the standard tilted flat-$\Lambda$CDM model. A number of measured cosmological parameter values differ significantly when determined using the tilted flat-XCDM and the nonflat XCDM parameterizations, including the baryonic matter density parameter and the reionization optical depth.

Planck 2015 Constraints on the Non-flat XCDM Inflation Model

Abstract 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.

Observational Constraints on the Tilted Spatially Flat and the Untilted Nonflat ϕCDM Dynamical Dark Energy Inflation Models

Abstract We constrain spatially flat tilted and nonflat untilted scalar field (ϕ) dynamical dark energy inflation (ϕCDM) models by using Planck 2015 cosmic microwave background (CMB) anisotropy measurements and recent baryonic acoustic oscillation distance observations, Type Ia supernovae apparent magnitude data, Hubble parameter measurements, and growth rate data. We assume an inverse power-law scalar field potential energy density . We find that the combination of the CMB data with the four non-CMB data sets significantly improves parameter constraints and strengthens the evidence for nonflatness in the nonflat untilted ϕCDM case from 1.8σ for the CMB measurements only to more than 3.1σ for the combined data. In the nonflat untilted ϕCDM model, current observations favor a spatially closed universe with spatial curvature contributing about two-thirds of a percent of the present cosmological energy budget. The flat tilted ϕCDM model is a 0.4σ better fit to the data than is the standard flat tilted ΛCDM model: current data allow for the possibility that dark energy is dynamical. The nonflat tilted ϕCDM model is in better accord with the Dark Energy Survey bounds on the rms amplitude of mass fluctuations now (σ 8) as a function of the nonrelativistic matter density parameter now (Ω m ) but it does not provide as good a fit to the larger-multipole Planck 2015 CMB anisotropy data as does the standard flat tilted ΛCDM model. A few cosmological parameter value measurements differ significantly when determined using the tilted flat and the untilted nonflat ϕCDM models, including the cold dark matter density parameter and the reionization optical depth.

Planck 2015 Constraints on the Nonflat ϕCDM Inflation Model

Abstract We perform Markov chain Monte Carlo analyses to put constraints on the nonflat ϕCDM inflation model using Planck 2015 cosmic microwave background (CMB) anisotropy data and baryon acoustic oscillation distance measurements. The ϕCDM model is a consistent dynamical dark energy model in which the currently accelerating cosmological expansion is powered by a scalar field ϕ slowly rolling down an inverse power-law potential energy density. We also use a physically consistent power spectrum for energy density inhomogeneities in this nonflat model. We find that, like the closed-ΛCDM and closed-XCDM models, the closed-ϕCDM model provides a better fit to the lower multipole region of the CMB temperature anisotropy data compared to that provided by the tilted flat-ΛCDM model. Also, like the other closed models, this model reduces the tension between the Planck and the weak lensing σ 8 constraints. However, the higher multipole region of the CMB temperature anisotropy data are better fit by the tilted flat-Λ model than by the closed models.