Recent analyses of the cosmic microwave background (CMB) maps from the WMAP satellite have uncovered evidence for a hemispherical power anomaly, i.e. a dipole modulation of the CMB power spectrum at large angular scales with an amplitude of +/-14 percent. Erickcek et al have put forward an inflationary model to explain this anomaly. Their scenario is a variation on the curvaton scenario in which the curvaton possesses a large-scale spatial gradient that modulates the amplitude of CMB fluctuations. We show that this scenario would also lead to a spatial gradient in the amplitude of perturbations sigma_8, and hence to a dipole asymmetry in any highly biased tracer of the underlying density field. Using the high-redshift quasars from the Sloan Digital Sky Survey, we find an upper limit on such a gradient of |nabla sigma_8|/sigma_8<0.027/r_{lss} (99% posterior probability), where r_{lss} is the comoving distance to the last-scattering surface. This rules out the simplest version of the curvaton spatial gradient scenario.
Cosmic microwave background measurements show an agreement with the concordance cosmology model except for a few notable anomalies: Power Suppression, the lack of large scale power in the temperature data compared to what is expected in the concordance model, and Cosmic Hemispherical Asymmetry, a dipolar breakdown of statistical isotropy. An expansion of the CMB covariance in Bipolar Spherical Harmonics naturally parametrizes both these large-scale anomalies, allowing us to perform an exhaustive, fully Bayesian joint analysis of the power spectrum and violations of statistical isotropy up to t…
Hemispherical power asymmetry has emerged as a new challenge to cosmology in early universe. While the cosmic microwave background (CMB) measurements indicated the asymmetry amplitude $A \simeq 0.07$ at the CMB scale $k_{\rm CMB}\simeq 0.0045\,{\rm Mpc}^{-1}$, the high-redshift quasar observations found no significant deviation from statistical isotropy. This conflict can be reconciled in some scale-dependent asymmetry models. We put forward a new parameterization of scale-dependent asymmetric power spectrum, inspired by a multi-speed inflation model. The 21-cm power spectrum from the epoch of…
Observations indicate that large-scale anomalies exist in the fluctuations of the cosmic microwave background. In these anomalies, the hemispherical power amplitude asymmetry has a correlation length comparable to that of the observable universe. We propose that a topological defect created by spontaneous breaking of the U(1) symmetry prior to inflation generated an initial phase variation, $δθ$, across the observable region of the universe. The amplitude of this phase fluctuation is protected by topology if the defect is inside the horizon, and is frozen by causality if the defect exits the h…
Based on recent observations of the cosmic microwave background (CMB), claims of statistical anomalies in the properties of the CMB fluctuations have been made. Although the statistical significance of the anomalies remains only at the $\sim2-3σ$ significance level, the fact that there are many different anomalies, several of which support a possible deviation from statistical isotropy, has motivated a search for models that provide a common mechanism to generate them. The goal of this paper is to investigate whether these anomalies could originate from non-Gaussian cosmological models, and to…
We derive a general expression for the probability of observing deviations from statistical isotropy in the cosmic microwave background (CMB) if the primordial fluctuations are non-Gaussian and extend to superhorizon scales. The primary motivation is to properly characterize the monopole and dipole modulations of the primordial power spectrum that are generated by the coupling between superhorizon and subhorizon perturbations. Unlike previous proposals for generating the hemispherical power asymmetry, we do not assume that the power asymmetry results from a single large superhorizon mode. Inst…
We propose a new model for the hemispherical power asymmetry of the CMB based on modulated reheating. Non-Gaussianity from modulated reheating can be small enough to satisfy the bound from Planck if the dominant modulation of the inflaton decay rate is linear in the modulating field $σ$. $σ$ must then acquire a spatially-modulated power spectrum with a red scale-dependence. This can be achieved if the primordial perturbation of $σ$ is generated via tachyonic growth of a complex scalar field. Modulated reheating due to $σ$ then produces a spatially modulated and scale-dependent sub-dominant con…
We calculate the power spectrum and hemispherical asymmetry of isocurvature and curvaton perturbations due to a complex field Φwhich is evolving along the tachyonic part of its potential. Using a semi-classical evolution of initially sub-horizon quantum fluctuations, we compute the power spectrum, mean field and hemispherical asymmetry as a function of the number of e-foldings of tachyonic growth ΔN and the tachyonic mass term cH^2. We find that a large hemispherical asymmetry due to the modulation of |Φ| can easily be generated via the spatial modulation of |Φ| across the horizon, with Delta …
Using a high resolution radio image, we successfully resolve the two fold image components B and C of the quasar lens system SDSS J1029+2623. The flux anomalies associated with these two components in the optical regime persist, albeit less strongly, in our radio observations, suggesting that the cluster must be modeled by something more than a single central potential. We argue that placing substructure close to one of the components can account for a flux anomaly with negligible changes in the component positions. Our best fit model has a substructure mass of ~10^8 solar masses up to the mas…
A reassessment of LVE method and hemispherical power asymmetry in CMB temperature data from Planck PR4
Indian Institute of Technology (BHU)（印度理工学院（贝拿勒斯印度教大学））；Korea Astronomy and Space Science Institute (KASI)（韩国天文学与空间科学研究院）；University of Science and Technology (UST)（韩国科学技术院）
Flux ratio anomalies in strong gravitationally lensed quasars constitute a unique way to probe the abundance of non-luminous dark matter haloes, and hence the nature of dark matter. In this paper we identify double imaged quasars as a statistically efficient probe of dark matter, since they are 20 times more abundant than quadruply imaged quasars. Using N-body simulations that include realistic baryonic feedback, we measure the full distribution of flux ratios in doubly imaged quasars for cold (CDM) and warm dark matter (WDM) cosmologies. Through this method, we fold in two key systematics - q…
Several anomalies have been identified which may imply a breakdown of the statistical isotropy of the cosmic microwave background (CMB). In particular, an anomalous alignment of the quadrupole and octopole and a hemispherical power asymmetry have increased in significance as the data have improved. There have been several attempts to explain these observations which explore isotropy breaking mechanisms within the early universe, but little attention has been given to the possibility that these anomalies have their origin within the local universe. We explore such a mechanism by considering the…
We analyze an inflationary model in which part of the power in density perturbations arises due to particle production. The amount of particle production is modulated by an auxiliary field. Given an initial gradient for the auxiliary field, this model produces a hemispherical power asymmetry and a suppression of power at low multipoles similar to those observed by WMAP and Planck in the CMB temperature. It also predicts an additive contribution to $δT$ with support only at very small $l$ that is aligned with the direction of the power asymmetry and has a definite sign, as well as small oscilla…
Temporary domain walls are produced during the bifurcation era of multi-stream inflation. The observational effects from such a domain wall to spectator field perturbations are calculated, and we expect the inflationary perturbations share similarities with the case of spectator field. A domain wall induces a preferred direction in the sky, affecting the angular distribution of perturbations. A correlated suppression of multipoles together with an alignment of multipole moments on the preferred direction are generated. Other observational aspects of multi-stream inflation, including hemispheri…
We investigate the statistics of flux anomalies in gravitationally lensed QSOs as a function of dark matter halo properties such as substructure content and halo ellipticity. We do this by creating a very large number of simulated lenses with finite source sizes to compare with the data. After analyzing these simulations, our conclusions are: 1) The finite size of the source is important. The point source approximation commonly used can cause biased results. 2) The widely used R_cusp statistic is sensitive to halo ellipticity as well as the lens' substructure content. 3) For compact substructu…
Physical models for the hemispherical power asymmetry in the cosmic microwave background (CMB) reported by the Planck Collaboration must satisfy CMB constraints to the homogeneity of the Universe and quasar constraints to power asymmetries. We survey a variety of models for the power asymmetry and show that consistent models include a modulated scale-dependent isocurvature contribution to the matter power spectrum or a modulation of the reionization optical depth, gravitational-wave amplitude, or scalar spectral index. We propose further tests to distinguish between the different scenarios.
We present a microlensing analysis of 61 Chandra observations of 14 quadruply lensed quasars. X-ray flux measurements of the individual quasar images give a clean determination of the microlensing effects in the lensing galaxy and thus offer a direct assessment of the local fraction of stellar matter making up the total integrated mass along the lines of sight through the lensing galaxy. A Bayesian analysis of the ensemble of lensing galaxies gives a most likely local stellar fraction of 7%, with the other 93% in a smooth, dark matter component, at an average impact parameter R_c of 6.6 kpc fr…
Recent Planck data show the anomalies of CMB fluctuations on large angular scales, which confirms the early observations by WMAP. We continue studying an inflationary model, in which before the slow roll inflation the universe is in a contracting phase, and fit the model with the Planck data. It is showed that this model may generate not only the power deficit at low-l, but also a large hemispherical power asymmetry in CMB. We also discuss the implication of the result to the eternal inflation scenario.
(abridged) Gravitationally lensed quasars can be used as powerful cosmological and astrophysical probes. We can (i) infer the Hubble constant based on the time-delay technique, (ii) unveil substructures along the l.o.s. toward distant galaxies, and (iii) compare the shape and the slope of baryons and dark matter distributions in galaxies. To reach these goals, we need high-accuracy astrometry and morphology measurements of the lens. In this work, we first present new astrometry for 11 lenses with measured time delays. Using MCS deconvolution on NIC2 HST images, we reached an astrometric accura…
We explore the weak lensing effects by ministructures in the line-of-sight in a quadruply lensed quasar MG0414+0534 that shows an anomaly in the flux-ratios. We find that the observed flux-ratio anomaly can be explained by a presence of either a minifilament or a minivoid in the line-of-sight with a surface mass density of the order of 10^(8-9) h^(-1) solar mass /arcsec^2 without taking into account any subhalos in the lensing galaxy. The astrometric perturbation by a possible minifilament/minivoid is <~ 0.001 arcsec and the amplitudes of convergence perturbations due to these perturbers are ~…
Several unexpected features have been observed in the microwave sky at large angular scales, both by WMAP an by Planck. Among those features is a lack of both variance and correlation on the largest angular scales, alignment of the lowest multipole moments with one another and with the motion and geometry of the Solar System, a hemispherical power asymmetry or dipolar power modulation, a preference for odd parity modes and an unexpectedly large cold spot in the Southern hemisphere. The individual p-values of the significance of these features are in the per mille to per cent level, when compar…
Quasars provide our farthest-reaching view of the Universe. The Sloan Survey now contains over 100,000 quasar candidates. A careful look at the angular distribution of quasar magnitudes shows a surprising intensity enhancement with a "bulls eye" pattern toward (alpha,delta) ~ (195°, 0°) for all wavelengths from UV through infrared. The angular pattern and size of the enhancement is very similar for all wavelengths, which is inconsistent with a Doppler shift due to a large peculiar velocity toward that direction. The shift is also too large to explain as a systematic error in the quasar magnitu…
Flux-ratio anomalies in cusp quasars reveal dark matter beyond CDM
Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；School of Astronomy and Space Sciences, University of Science and Technology of China（中国科学技术大学天文与空间科学学院）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Institute for Frontier in Astronomy and Astrophysics, Beijing Normal University（北京师范大学前沿天文与天体物理研究所）
(Abridged) A simple six-parameter LCDM model provides a successful fit to WMAP data, both when the data are analyzed alone and in combination with other cosmological data. Even so, it is appropriate to search for any hints of deviations from the now standard model of cosmology, which includes inflation, dark energy, dark matter, baryons, and neutrinos. The cosmological community has subjected the WMAP data to extensive and varied analyses. While there is widespread agreement as to the overall success of the six-parameter LCDM model, various "anomalies" have been reported relative to that model…
We perform an analysis of the CMB temperature data taken by the Planck satellite investigating if there is any significant deviation from cosmological isotropy. We look for differences in the spectrum between two opposite hemispheres and also for dipolar modulations. We propose a new way to avoid biases due to partial-sky coverage by producing a mask symmetrized in antipodal directions, in addition to the standard smoothing procedure. We also properly take into account both Doppler and aberration effects due to our peculiar velocity and the anisotropy of the noise, since these effects induce a…
Several unexpected features are observed at large angular scales in the CMB temperature anisotropy measurements by both WMAP and Planck. These include the lack of both variance and correlation, alignment of the lowest multipole moments with one another, hemispherical power asymmetry, and an odd-to-even parity excess. In this work, we study the statistics of eight representative large-angle CMB features in order to evaluate their covariance in LCDM. We do so using two sets of simulated CMB temperature maps; an ensemble of 100,000 simple Gaussian simulations, and 1000 Full Focal Plane (FFP) simu…
Multiply-imaged quasars and AGNs observed in the mid-infrared (MIR) range are commonly assumed to be unaffected by the microlensing produced by the stars in their lensing galaxy. In this paper, we investigate the validity domain of this assumption. Indeed, that premise disregards microlensing of the accretion disc in the MIR range, and does not account for recent progress in our knowledge of the dusty torus. To simulate microlensing, we first built a simplified image of the quasar composed of an accretion disc, and of a larger ring-like torus. The mock quasars are then microlensed using an inv…
Quasars provide our farthest-reaching view of the Universe. The Sloan Survey now contains over 100,000 quasar candidates. A careful look at the angular distribution of quasar spectra shows a surprising "bullseye" pattern on the sky toward (RA, Dec) ~ (190°, 0°) for all wavelengths from UV through infrared. The angular distribution of the shift in the UV suggests a large peculiar velocity vp toward that direction. However, the size of the shift would indicate a vp ~0.2 c, which is two orders of magnitude larger than measures of our peculiar velocity from nearby galaxies and cosmic microwave bac…
We examine all-sky cosmic microwave background (CMB) temperature maps on large angular scales to compare their consistency with two scenarios: the standard inflationary quantum picture, and a distribution constrained to have a universal variance of primordial curvature perturbations on great circles. The latter symmetry is not a property of standard quantum inflation, but may be a symmetry of holographic models with causal quantum coherence on null surfaces. Since the variation of great-circle variance is dominated by the largest angular scale modes, in the latter case the amplitude and direct…
Measurements of the Cosmic Microwave Background (CMB) temperature anisotropies on large angular scales have uncovered a number of anomalous features of marginal statistical significance, such as a hemispherical power asymmetry, lack of power on large angular scales, and features in the power spectrum. Because the primary CMB temperature has been measured at the cosmic variance limit, determining if these anomalies are hints of new physics as opposed to foregrounds, systematics, or simply statistical flukes, requires new observables. In this paper, we highlight the potential contribution that f…
If the hemispherical power asymmetry observed in the cosmic microwave background (CMB) on large angular scales is attributable to a superhorizon curvaton fluctuation, then the simplest model predicts that the primordial density fluctuations should be similarly asymmetric on all smaller scales. The distribution of high-redshift quasars was recently used to constrain the power asymmetry on scales k ~ 1.5h/Mpc, and the upper bound on the amplitude of the asymmetry was found to be a factor of six smaller than the amplitude of the asymmetry in the CMB. We show that it is not possible to generate an…
Since WMAP and Planck some anomalous features appeared in the Cosmic Microwave Background (CMB) large-angle anisotropy, the so-called anomalies. One of these is the hemispherical power asymmetry, i.e. a difference in the average power on the two hemispheres centered around (l, b) = (221, -20), which shows a relatively high level of significance. Such an anomaly could be the signature of a departure from statistical isotropy on large scales. Here we investigate the physical origin of this anomaly using the Cosmological Gravitational Wave Background (CGWB) detectable by future GW detectors. Inde…
The foundation of modern cosmology relies on the so-called cosmological principle which states an homogeneous and isotropic distribution of matter in the universe on large scales. However, recent observations, such as the temperature anisotropy of the cosmic microwave background (CMB) radiation, the motion of galaxies in the universe, the polarization of quasars and the acceleration of the cosmic expansion, indicate preferred directions in the sky. If these directions have a cosmological origin, the cosmological principle would be violated, and modern cosmology should be reconsidered. In this …
A dark energy model (DE) is proposed based on Ginzburg-Landau theory of phase transition (GLT). This model, GLTofDE, surprisingly provides a framework to study not only temporal tensions in cosmology e.g. $H_0$ tension but also spatial anomalies of CMB e.g. the hemispherical power asymmetry and quadrupole-octopole alignment. In the mean field (or Landau) approximation of GLTofDE, there is a spontaneously symmetry breaking exactly like the Higgs potential. We modeled this transition, phenomenologically, and showed that GLTofDE can resolve both the $H_0$ tension and Lyman-$α$ anomaly in a non-tr…
We consider the possibility that the primordial curvature perturbation is direction-dependent. To first order this is parameterised by a quadrupolar modulation of the power spectrum and results in statistical anisotropy of the CMB, which can be quantified using `bipolar spherical harmonics'. We compute these for the Planck DR2-2015 SMICA map and estimate the noise covariance from Planck Full Focal Plane 9 simulations. A constant quadrupolar modulation is detected with 2.2 sigma significance, dropping to 2 sigma when the primordial power is assumed to scale with wave number k as a power law. Go…
