ABSTRACT We examine the internal consistency of the Planck 2015 cosmic microwave background (CMB) temperature anisotropy power spectrum. We show that tension exists between cosmological constant cold ...dark matter ( ) model parameters inferred from multipoles (roughly those accessible to Wilkinson Microwave Anisotropy Probe), and from , particularly the CDM density, , which is discrepant at for a Planck -motivated prior on the optical depth, . We find some parameter tensions to be larger than previously reported because of inaccuracy in the code used by the Planck Collaboration to generate model spectra. The Planck constraints are also in tension with low-redshift data sets, including Planck 's own measurement of the CMB lensing power spectrum ( ), and the most precise baryon acoustic oscillation scale determination ( ). The Hubble constant predicted by Planck from , km s Mpc−1, disagrees with the most precise local distance ladder measurement of km s Mpc−1 at the level, while the Planck value from , km s Mpc−1, is consistent within . A discrepancy between the Planck and South Pole Telescope high-multipole CMB spectra disfavors interpreting these tensions as evidence for new physics. We conclude that the parameters from the Planck high-multipole spectrum probably differ from the underlying values due to either an unlikely statistical fluctuation or unaccounted-for systematics persisting in the Planck data.
THE 1% CONCORDANCE HUBBLE CONSTANT Bennett, C L; Larson, D; Weiland, J L ...
The Astrophysical journal,
10/2014, Volume:
794, Issue:
2
Journal Article
Peer reviewed
The determination of the Hubble constant has been a central goal in observational astrophysics for nearly a hundred years. Extraordinary progress has occurred in recent years on two fronts: the ...cosmic distance ladder measurements at low redshift and cosmic microwave background (CMB) measurements at high redshift. The CMB is used to predict the current expansion rate through a best-fit cosmological model. Complementary progress has been made with baryon acoustic oscillation (BAO) measurements at relatively low redshifts. While BAO data do not independently determine a Hubble constant, they are important for constraints on possible solutions and checks on cosmic consistency. A precise determination of the Hubble constant is of great value, but it is more important to compare the high and low redshift measurements to test our cosmological model. Significant tension would suggest either uncertainties not accounted for in the experimental estimates or the discovery of new physics beyond the standard model of cosmology. In this paper we examine in detail the tension between the CMB, BAO, and cosmic distance ladder data sets. We find that these measurements are consistent within reasonable statistical expectations and we combine them to determine a best-fit Hubble constant of 69.6 + or - 0.7 km s super(-1) Mpc super(-1). This value is based upon WMAP9+SPT+ACT+6dFGS+BOSS/DR11+H sub(0)/Riess; we explore alternate data combinations in the text. The combined data constrain the Hubble constant to 1%, with no compelling evidence for new physics.
We examine the impact of baryon acoustic oscillation (BAO) scale measurements on the discrepancy between the value of the Hubble constant (H0) inferred from the local distance ladder and that from ...Planck cosmic microwave background (CMB) data. While the BAO data alone cannot constrain H0, we show that combining the latest BAO results with WMAP, Atacama Cosmology Telescope (ACT), or South Pole Telescope (SPT) CMB data produces values of H0 that are lower than the distance ladder, independent of Planck, and that this downward pull was less apparent in some earlier analyses that used only angle-averaged BAO scale constraints rather than full anisotropic information. At the same time, the combination of BAO and CMB data also disfavors the lower values of H0 preferred by the Planck high-multipole temperature power spectrum. Combining galaxy and Ly forest BAO with a precise estimate of the primordial deuterium abundance produces km s−1 Mpc−1 for the flat model. This value is completely independent of CMB anisotropy constraints and is lower than the latest distance ladder constraint, although tension also exists between the galaxy BAO and Ly BAO. These results show that it is not possible to explain the H0 disagreement solely with a systematic error specific to the Planck data. The fact that tensions remain even after the removal of any single data set makes this intriguing puzzle all the more challenging to resolve.
We constrain cosmological parameters using combined measurements of the baryon acoustic oscillation (BAO) feature in the correlation function of galaxies and Lyα absorbers that together cover 0.1 < z ...< 2.4. The BAO position measurements alone - without fixing the absolute sound horizon 'standard ruler' length with cosmic microwave background (CMB) data - constrain Ωm = 0.303 ± 0.040 (68 per cent confidence) for a flat Λ cold dark matter (ΛCDM) model, and
,
for a flat wCDM model. Adding other large-scale structure (LSS) clustering constraints - correlation function shape, the Alcock-Paczynski test and growth rate information - to the BAO considerably tightens constraints (Ωm = 0.290 ± 0.019, H
0 = 67.5 ± 2.8 km s−1 Mpc−1, σ8 = 0.80 ± 0.05 for ΛCDM, and w = −1.14 ± 0.19 for wCDM). The LSS data mildly prefer a lower value of H
0, and a higher value of Ωm, than local distance ladder and Type IA supernovae (SNe) measurements, respectively. While tension in the combined CMB, SNe and distance ladder data appear to be relieved by allowing w < −1, this freedom introduces tension with the LSS σ8 constraint from the growth rate of matter fluctuations. The combined constraint on w from CMB, BAO and LSS clustering for a flat wCDM model is w = −1.03 ± 0.06.
We present the final nine-year maps and basic results from the Wilkinson Microwave Anisotropy Probe (WMAP) mission. The full nine-year analysis of the time-ordered data provides updated ...characterizations and calibrations of the experiment. We also provide new nine-year full sky temperature maps that were processed to reduce the asymmetry of the effective beams. Temperature and polarization sky maps are examined to separate cosmic microwave background (CMB) anisotropy from foreground emission, and both types of signals are analyzed in detail.We provide new point source catalogs as well as new diffuse and point source foreground masks. An updated template-removal process is used for cosmological analysis; new foreground fits are performed, and new foreground reduced are presented.We nowimplement an optimal C(exp -1)1 weighting to compute the temperature angular power spectrum. The WMAP mission has resulted in a highly constrained Lambda-CDM cosmological model with precise and accurate parameters in agreement with a host of other cosmological measurements. When WMAP data are combined with finer scale CMB, baryon acoustic oscillation, and Hubble constant measurements, we find that big bang nucleosynthesis is well supported and there is no compelling evidence for a non-standard number of neutrino species (N(sub eff) = 3.84 +/- 0.40). The model fit also implies that the age of the universe is (sub 0) = 13.772 +/- 0.059 Gyr, and the fit Hubble constant is H(sub 0) = 69.32 +/- 0.80 km/s/ Mpc. Inflation is also supported: the fluctuations are adiabatic, with Gaussian random phases; the detection of a deviation of the scalar spectral index from unity, reported earlier by the WMAP team, now has high statistical significance (n(sub s) = 0.9608+/-0.0080); and the universe is close to flat/Euclidean (Omega = −0.0027+0.0039/−0.0038). Overall, the WMAP mission has resulted in a reduction of the cosmological parameter volume by a factor of 68,000 for the standard six-parameter Lambda-CDM model, based on CMB data alone. For a model including tensors, the allowed seven-parameter volume has been reduced by a factor 117,000. Other cosmological observations are in accord with the CMB predictions, and the combined data reduces the cosmological parameter volume even further.With no significant anomalies and an adequate goodness of fit, the inflationary flat Lambda-CDM model and its precise and accurate parameters rooted in WMAP data stands as the standard model of cosmology.
ABSTRACT
We evaluate the ability of convolutional neural networks (CNNs) to predict galaxy cluster masses in the BAHAMAS hydrodynamical simulations. We train four separate single-channel networks ...using: stellar mass, soft X-ray flux, bolometric X-ray flux, and the Compton y parameter as observational tracers, respectively. Our training set consists of ∼4800 synthetic cluster images generated from the simulation, while an additional ∼3200 images form a validation set and a test set, each with 1600 images. In order to mimic real observation, these images also contain uncorrelated structures located within 50 Mpc in front and behind clusters and seen in projection, as well as instrumental systematics including noise and smoothing. In addition to CNNs for all the four observables, we also train a ‘multichannel’ CNN by combining the four observational tracers. The learning curves of all the five CNNs converge within 1000 epochs. The resulting predictions are especially precise for halo masses in the range $10^{13.25}\, \mathrm{M}_{\odot }\lt M\lt 10^{14.5}\, \mathrm{M}_{\odot }$, where all five networks produce mean mass biases of order ≈1 per cent with a scatter of ≲20 per cent. The network trained with Compton y parameter maps yields the most precise predictions. We interpret the network’s behaviour using two diagnostic tests to determine which features are used to predict cluster mass. The CNNs trained with stellar mass images detect galaxies (not surprisingly), while CNNs trained with gas-based tracers utilize the shape of the signal to estimate cluster mass.
ABSTRACT
The location of a galaxy cluster’s centroid is typically derived from observations of the galactic and/or gas component of the cluster, but these typically deviate from the true centre. This ...can produce bias when observations are combined to study average cluster properties. Using data from the BAryons and HAloes of MAssive Systems (BAHAMAS) cosmological hydrodynamic simulations, we study this bias in both two and three dimensions for 2000 clusters over the 1013–1015 M⊙ mass range. We quantify and model the offset distributions between observationally motivated centres and the ‘true’ centre of the cluster, which is taken to be the most gravitationally bound particle measured in the simulation. We fit the cumulative distribution function of offsets with an exponential distribution and a Gamma distribution fit well with most of the centroid definitions. The galaxy-based centres can be seen to be divided into a mis-centred group and a well-centred group, with the well-centred group making up about $60{{\ \rm per\ cent}}$ of all the clusters. Gas-based centres are overall less scattered than galaxy-based centres. We also find a cluster-mass dependence of the offset distribution of gas-based centres, with generally larger offsets for smaller mass clusters. We then measure cluster density profiles centred at each choice of the centres and fit them with empirical models. Stacked, mis-centred density profiles fit to the Navarro–Frenk–White dark matter profile and Komatsu–Seljak gas profile show that recovered shape and size parameters can significantly deviate from the true values. For the galaxy-based centres, this can lead to cluster masses being underestimated by up to $10{{\ \rm per\ cent}}$.
The combination of seven-year data from WMAP and improved astrophysical data rigorously tests the standard cosmological model and places new constraints on its basic parameters and extensions. By ...combining the WMAP data with the latest distance measurements from the baryon acoustic oscillations (BAO) in the distribution of galaxies and the Hubble constant (H 0) measurement, we determine the parameters of the simplest six-parameter Delta *LCDM model. The power-law index of the primordial power spectrum is ns = 0.968 ? 0.012 (68% CL) for this data combination, a measurement that excludes the Harrison-Zel'dovich-Peebles spectrum by 99.5% CL. The other parameters, including those beyond the minimal set, are also consistent with, and improved from, the five-year results. We find no convincing deviations from the minimal model. The seven-year temperature power spectrum gives a better determination of the third acoustic peak, which results in a better determination of the redshift of the matter-radiation equality epoch. Notable examples of improved parameters are the total mass of neutrinos, Delta *Sm Delta *n < 0.58 eV(95%CL), and the effective number of neutrino species, N eff = 4.34+0.86 --0.88 (68% CL), which benefit from better determinations of the third peak and H 0. The limit on a constant dark energy equation of state parameter from WMAP+BAO+H 0, without high-redshift Type Ia supernovae, is w = --1.10 ? 0.14 (68% CL). We detect the effect of primordial helium on the temperature power spectrum and provide a new test of big bang nucleosynthesis by measuring Yp = 0.326 ? 0.075 (68% CL). We detect, and show on the map for the first time, the tangential and radial polarization patterns around hot and cold spots of temperature fluctuations, an important test of physical processes at z = 1090 and the dominance of adiabatic scalar fluctuations. The seven-year polarization data have significantly improved: we now detect the temperature-E-mode polarization cross power spectrum at 21 Delta *s, compared with 13 Delta *s from the five-year data. With the seven-year temperature-B-mode cross power spectrum, the limit on a rotation of the polarization plane due to potential parity-violating effects has improved by 38% to (68% CL). We report significant detections of the Sunyaev-Zel'dovich (SZ) effect at the locations of known clusters of galaxies. The measured SZ signal agrees well with the expected signal from the X-ray data on a cluster-by-cluster basis. However, it is a factor of 0.5-0.7 times the predictions from 'universal profile' of Arnaud et al., analytical models, and hydrodynamical simulations. We find, for the first time in the SZ effect, a significant difference between the cooling-flow and non-cooling-flow clusters (or relaxed and non-relaxed clusters), which can explain some of the discrepancy. This lower amplitude is consistent with the lower-than-theoretically expected SZ power spectrum recently measured by the South Pole Telescope Collaboration.
The reionization optical depth is the most poorly determined of the six ΛCDM parameters fit to CMB anisotropy data. Instrumental noise and systematics have prevented uncertainties from reaching their ...cosmic variance limit. At present, the data sets providing the most statistical constraining power are the WMAP, Planck LFI, and Planck HFI full-sky polarization maps. As the reprocessed HFI data with reduced systematics are not yet publicly unavailable, we examine determinations of τ using 9 year WMAP and 2015 Planck LFI data, with an emphasis on characterizing potential systematic bias resulting from foreground template and masking choices. We find evidence for a low-level systematic in the LFI polarization data with a roughly common-mode morphology across the LFI frequencies and a spectrum consistent with leakage of intensity signal into the polarization channels. We demonstrate significant bias in the optical depth derived when using the LFI 30 GHz map as a template to clean synchrotron from WMAP data, and recommend against the use of the 2015 LFI 30 GHz polarization data as a foreground template for non-LFI data sets. We find an inconsistency between versions of the 2015 polarized 353 GHz dust templates reconstructed from the Planck likelihood and those from delivered maps, which can affect τ at the 1 level. The spread in τ values over the ensemble of data combinations we study suggests that systematic uncertainties still contribute significantly to the current uncertainty in τ, but all values are consistent with the range of τ = 0.07 0.02.
We report on the discovery and analysis of bursts from nine new repeating fast radio burst (FRB) sources found using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. These ...sources span a dispersion measure (DM) range of 195-1380 pc cm−3. We detect two bursts from three of the new sources, three bursts from four of the new sources, four bursts from one new source, and five bursts from one new source. We determine sky coordinates of all sources with uncertainties of ∼10′. We detect Faraday rotation measures (RMs) for two sources, with values −20(1) and −499.8(7) rad m−2, that are substantially lower than the RM derived from bursts emitted by FRB 121102. We find that the DM distribution of our events, combined with the nine other repeaters discovered by CHIME/FRB, is indistinguishable from that of thus far non-repeating CHIME/FRB events. However, as previously reported, the burst widths appear statistically significantly larger than the thus far non-repeating CHIME/FRB events, further supporting the notion of inherently different emission mechanisms and/or local environments. These results are consistent with previous work, though are now derived from 18 repeating sources discovered by CHIME/FRB during its first year of operation. We identify candidate galaxies that may contain FRB 190303.J1353+48 (DM = 222.4 pc cm−3).
PDF
