1511.00055
Quantifying discordance in the 2015 Planck CMB spectrum
Addision et al
Examine the internal consistency of the Planck 2015 CMB temperature anisotropy power spectrum. Show that tension exists between LCDM model parameters inferred from multipoles l<1000 (roughly those accessible to WMAP), and from l>=1000, particularly the CDM density, Omega_ch^2, which is discrepant at 2.5 sigma for a Planck-Motivated prior on the optical depth, tau=0.07±0.02. 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 l>=1000 constraints are also in tension with low-redshift data sets, including Planck's own measurement of the CMB lensing power spectrum (2.4 sigma), and the most precise BAO scale determination (2.5 sigma). The Hubble constant predicted by Planck from l>=1000, H0=64.1±1.7 km/s/Mpc, disagrees with the most precise local distance ladder measurement of 73.0±2.4 km/s/Mpc at the 3.0 sigma level, while the Planck value from l<1000, 69.7±1.7km/s/Mpc, is consistent within 1 sigma. A discrepancy between the Planck and SPT high-multipole CMB spectra disfavors interpreting these tensions as evidence for new physics. 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.
1511.00392
A detection of Baryon Acoustic Oscillations from the distribution of galaxy clusters
Hong, Han, Wen
Calculate the correlation function of 79k galaxy clusters in 0.05<z<0.5 selected from the WH15 cluster catalog. With a weight of cluster mass, a significant BAO peak is detected on the correlation function with a significance of 3.9 sigma. By fitting the correlation function with a LCDM model curve, find D_v(z=0.331) Rd^fid/Rd = 1269.4±58 Mpc which is consistent wit the Planck 2015 cosmology. Find that the correlation functions of the higher mass sub-samples show a higher amplitude at small scales of r<80 Mpc/h, which is consistent with the previous result. Find a clear signal of the FoG effect on the 2d correlation function of the whole sample, which indicates the random peculiar motion of central bright galaxies in the gravitational potential well of clusters.
1511.00663
Modeling the reconstructed BAO in Fourier space
Seo, Beutler, Ross, Saito
The density field reconstruction technique, which was developed to partially reverse the nonlinear degradation of BAO feature in the galaxy redshift surveys, has been successful in substantially improving the cosmo constraints from recent surveys such as BOSS. Estimate the efficiency of the reconstruction method as a function of various reconstruction details. To directly quantify the BAO information in NL density fields before and after reconstruction, calculate the cross-correlations (i.e., propagators) of the pre(post)-reconstructed density field with the initial linear field using a mock galaxy sample that is designed to mimic the clustering of the BOSS CMASS galaxies. The results directly provide the BAO damping as a function of wavenumber that can be implemented into the Fisher matrix analysis. Focus on investigating the dependence of the propagator on a choice of smoothing filters and on two major different conventions of the redshift-space density field reconstruction that have been used in literature. By estimating the BAO signal-to-noise for each case, predict constraints on the angular diameter distance and Hubble parameter using the Fisher matrix analysis. Thus determine an optimal Gaussian smoothing filter scale for the S/N level of the BOSS CMASS. Also present appropriate BAO fitting models for different reconstruction methods based on the first and second order Lagrangian perturbation theory in Fourier space. Using the mock data, show that the modified BAO fitting model can substantially improve the accuracy of the BAO position in the best fits as well as the goodness of the fits.
No comments:
Post a Comment