Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userOn the impact of large angle CMB polarization data on cosmological parameters
138
0
0.0
(
0
)
Added by
Massimiliano Lattanzi
Publication date
2016
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
(abridged) We study the impact of the large-angle CMB polarization datasets publicly released by the WMAP and Planck satellites on the estimation of cosmological parameters of the $Lambda$CDM model. To complement large-angle polarization, we consider the high-resolution CMB datasets from either WMAP or Planck, as well as CMB lensing as traced by Planck. In the case of WMAP, we compute the large-angle polarization likelihood starting over from low-resolution frequency maps and their covariance matrices, and perform our own foreground mitigation technique, which includes as a possible alternative Planck 353 GHz data to trace polarized dust. We find that the latter choice induces a downward shift in the optical depth $tau$, of order ~$2sigma$, robust to the choice of the complementary high-l dataset. When the Planck 353 GHz is consistently used to minimize polarized dust emission, WMAP and Planck 70 GHz large-angle polarization data are in remarkable agreement: by combining them we find $tau = 0.066 ^{+0.012}_{-0.013}$, again very stable against the particular choice for high-$ell$ data. We find that the amplitude of primordial fluctuations $A_s$, notoriously degenerate with $tau$, is the parameter second most affected by the assumptions on polarized dust removal, but the other parameters are also affected, typically between $0.5$ and $1sigma$. In particular, cleaning dust with plancks 353 GHz data imposes a $1sigma$ downward shift in the value of the Hubble constant $H_0$, significantly contributing to the tension reported between CMB based and direct measurements of $H_0$. On the other hand, we find that the appearance of the so-called low $ell$ anomaly, a well-known tension between the high- and low-resolution CMB anisotropy amplitude, is not significantly affected by the details of large-angle polarization, or by the particular high-$ell$ dataset employed.
rate research
Read More
Cosmic microwave background polarization encodes information not only on the early universe but also dark energy, neutrino mass, and gravity in the late universe through CMB lensing. Ground based surveys such as ACTpol, PolarBear, SPTpol significantly complement cosmological constraints from the Planck satellite, strengthening the CMB dark energy figure of merit and neutrino mass constraints by factors of 3-4. This changes the dark energy probe landscape. We evaluate the state of knowledge in 2017 from ongoing experiments including dark energy surveys (supernovae, weak lensing, galaxy clustering), fitting for dynamical dark energy, neutrino mass, and a modified gravitational growth index. Adding a modest strong lensing time delay survey improves those dark energy constraints by a further 32%, and an enhanced low redshift supernova program improves them by 26%.
In this paper we present a parameter estimation analysis of the polarization and temperature power spectra from the second and third season of observations with the QUaD experiment. QUaD has for the first time detected multiple acoustic peaks in the E-mode polarization spectrum with high significance. Although QUaD-only parameter constraints are not competitive with previous results for the standard 6-parameter LCDM cosmology, they do allow meaningful polarization-only parameter analyses for the first time. In a standard 6-parameter LCDM analysis we find the QUaD TT power spectrum to be in good agreement with previous results. However, the QUaD polarization data shows some tension with LCDM. The origin of this 1 to 2 sigma tension remains unclear, and may point to new physics, residual systematics or simple random chance. We also combine QUaD with the five-year WMAP data set and the SDSS Luminous Red Galaxies 4th data release power spectrum, and extend our analysis to constrain individual isocurvature mode fractions, constraining cold dark matter density, alpha(cdmi)<0.11 (95 % CL), neutrino density, alpha(ndi)<0.26 (95 % CL), and neutrino velocity, alpha(nvi)<0.23 (95 % CL), modes. Our analysis sets a benchmark for future polarization experiments.
The anomalous lack of large angle temperature correlations has been a surprising feature of the cosmic microwave background (CMB) since first observed by COBE-DMR and subsequently confirmed and strengthened by the Wilkinson Microwave Anisotropy Probe. This anomaly may point to the need for modifications of the standard model of cosmology or may indicate that our Universe is a rare statistical fluctuation within that model. Further observations of the temperature auto-correlation function will not elucidate the issue; sufficiently high precision statistical observations already exist. Instead, alternative probes are required. In this work we explore the expectations for forthcoming polarization observations. We define a prescription to test the hypothesis that the large-angle CMB temperature perturbations in our Universe represent a rare statistical fluctuation within the standard cosmological model. These tests are based on the temperature-$Q$ Stokes parameter correlation. Unfortunately these tests cannot be expected to be definitive. However, we do show that if this $TQ$-correlation is observed to be sufficiently large over an appropriately chosen angular range, then the hypothesis can be rejected at a high confidence level. We quantify these statements and optimize the statistics we have constructed to apply to the anticipated polarization data. We find that we can construct a statistic that has a 25 per cent chance of excluding the hypothesis that we live in a rare realization of LCDM at the 99.9 per cent confidence level.
Cosmological CPT violation will rotate the polarized direction of CMB photons, convert partial CMB E mode into B mode and vice versa. It will generate non-zero EB, TB spectra and change the EE, BB, TE spectra. This phenomenon gives us a way to detect the CPT-violation signature from CMB observations, and also provides a new mechanism to produce B mode polarization. In this paper, we perform a global analysis on tensor-to-scalar ratio $r$ and polarization rotation angles based on current CMB datasets with both low $ell$ (Planck, BICEP2/Keck Array) and high $ell$ (POLARBEAR, SPTpol, ACTPol). Benefited from the high precision of CMB data, we obtain the isotropic rotation angle $bar{alpha} = -0.01^circ pm 0.37^circ $ at 68% C.L., the variance of the anisotropic rotation angles $C^{alpha}(0)<0.0032,mathrm{rad}^2$, the scale invariant power spectrum $D^{alphaalpha}_{ell in [2, 350]}<4.71times 10^{-5} ,mathrm{rad}^2$ and $r<0.057$ at 95% C.L.. Our result shows that with the polarization rotation effect, the 95% upper limit on $r$ gets tightened by 17%.
Accurate cosmological parameter estimates using polarization data of the cosmic microwave background (CMB) put stringent requirements on map calibration, as highlighted in the recent results from the Planck satellite. In this paper, we point out that a model-dependent determination of polarization calibration can be achieved by the joint fit of the TE and EE CMB power spectra. This provides a valuable cross-check to band-averaged polarization efficiency measurements determined using other approaches. We demonstrate that, in $Lambda$CDM, the combination of the TE and EE constrain polarization calibration with sub-percent uncertainty with Planck data and 2% uncertainty with SPTpol data. We arrive at similar conclusions when extending $Lambda$CDM to include the amplitude of lensing $A_{rm L}$, the number of relativistic species $N_{rm eff}$, or the sum of the neutrino masses $sum m_{ u}$. The uncertainties on cosmological parameters are minimally impacted when marginalizing over polarization calibration, except, as can be expected, for the uncertainty on the amplitude of the primordial scalar power spectrum $ln(10^{10} A_{rm s})$, which increases by $20-50$%. However, this information can be fully recovered by adding TT data. For current and future ground-based experiments, SPT-3G and CMB-S4, we forecast the cosmological parameter uncertainties to be minimally degraded when marginalizing over polarization calibration parameters. In addition, CMB-S4 could constrain its polarization calibration at the level of $sim$0.2% by combining TE and EE, and reach $sim$0.06% by also including TT. We therefore conclude that relying on calibrating against Planck polarization maps, whose statistical uncertainty is limited to $sim$0.5%, would be insufficient for upcoming experiments.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
