Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userE- and B-mode mixing from incomplete knowledge of the shear correlation
94
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Aims. We quantify the mixing of the measured cosmic-shear E- and B-modes caused by the lack of shear-correlation measurements on small and large scales, arising from a lack of close projected galaxy pairs and the finite field size, respectively. Methods. We calculate the aperture-mass statistics <M_{ap, perp}^2> and the E-/B-mode shear-correlation functions xi_{E, B +/-} where small- and large-scale cutoffs are taken into account. We assess the deviation of the obtained E-mode to the true E-mode and the introduction of a spurious B-mode. Results. The measured aperture-mass dispersion is underestimated by more than 10% on scales smaller than 12 times the lower cutoff. For a precise measurement of the E- and B-modes at the percent level using a combination of xi_{E, B +} and xi_{E, B -}, a field as large as 7 (2.4) degrees is necessary for ground-based (space-based) observations.
rate research
Read More
Cosmic shear is considered one of the most powerful methods for studying the properties of Dark Energy in the Universe. As a standard method, the two-point correlation functions $xi_pm(theta)$ of the cosmic shear field are used as statistical measures for the shear field. In order to separate the observed shear into E- and B-modes, the latter being most likely produced by remaining systematics in the data set and/or intrinsic alignment effects, several statistics have been defined before. Here we aim at a complete E-/B-mode decomposition of the cosmic shear information contained in the $xi_pm$ on a finite angular interval. We construct two sets of such E-/B-mode measures, namely Complete Orthogonal Sets of E-/B-mode Integrals (COSEBIs), characterized by weight functions between the $xi_pm$ and the COSEBIs which are polynomials in $theta$ or polynomials in $ln(theta)$, respectively. Considering the likelihood in cosmological parameter space, constructed from the COSEBIs, we study their information contents. We show that the information grows with the number of COSEBI modes taken into account, and that an asymptotic limit is reached which defines the maximum available information in the E-mode component of the $xi_pm$. We show that this limit is reached the earlier (i.e., for a smaller number of modes considered) the narrower the angular range is over which $xi_pm$ are measured, and it is reached much earlier for logarithmic weight functions. For example, for $xi_pm$ on the interval $1le thetale 400$, the asymptotic limit for the parameter pair $(Omega_m, sigma_8)$ is reached for $sim 25$ modes in the linear case, but already for 5 modes in the logarithmic case. The COSEBIs form a natural discrete set of quantities, which we suggest as method of choice in future cosmic shear likelihood analyses.
We present measurements of the $E$-mode ($EE$) polarization power spectrum and temperature-$E$-mode ($TE$) cross-power spectrum of the cosmic microwave background using data collected by SPT-3G, the latest instrument installed on the South Pole Telescope. This analysis uses observations of a 1500 deg$^2$ region at 95, 150, and 220 GHz taken over a four month period in 2018. We report binned values of the $EE$ and $TE$ power spectra over the angular multipole range $300 le ell < 3000$, using the multifrequency data to construct six semi-independent estimates of each power spectrum and their minimum-variance combination. These measurements improve upon the previous results of SPTpol across the multipole ranges $300 le ell le 1400$ for $EE$ and $300 le ell le 1700$ for $TE$, resulting in constraints on cosmological parameters comparable to those from other current leading ground-based experiments. We find that the SPT-3G dataset is well-fit by a $Lambda$CDM cosmological model with parameter constraints consistent with those from Planck and SPTpol data. From SPT-3G data alone, we find $H_0 = 68.8 pm 1.5 mathrm{km,s^{-1},Mpc^{-1}}$ and $sigma_8 = 0.789 pm 0.016$, with a gravitational lensing amplitude consistent with the $Lambda$CDM prediction ($A_L = 0.98 pm 0.12$). We combine the SPT-3G and the Planck datasets and obtain joint constraints on the $Lambda$CDM model. The volume of the 68% confidence region in six-dimensional $Lambda$CDM parameter space is reduced by a factor of 1.5 compared to Planck-only constraints, with only slight shifts in central values. We note that the results presented here are obtained from data collected during just half of a typical observing season with only part of the focal plane operable, and that the active detector count has since nearly doubled for observations made with SPT-3G after 2018.
We present a re-analysis of the CFHTLenS weak gravitational lensing survey using Complete Orthogonal Sets of E/B-mode Integrals, known as COSEBIs. COSEBIs provide a complete set of functions to efficiently separate E-modes from B-modes and hence allow for robust and stringent tests for systematic errors in the data. This analysis reveals significant B-modes on large angular scales that were not previously seen using the standard E/B decomposition analyses. We find that the significance of the B-modes is enhanced when the data is split by galaxy type and analysed in tomographic redshift bins. Adding tomographic bins to the analysis increases the number of COSEBIs modes, which results in a less accurate estimation of the covariance matrix from a set of simulations. We therefore also present the first compressed COSEBIs analysis of survey data, where the COSEBIs modes are optimally combined based on their sensitivity to cosmological parameters. In this tomographic CCOSEBIs analysis we find the B-modes to be consistent with zero when the full range of angular scales are considered.
We present measurements of $E$-mode polarization and temperature-$E$-mode correlation in the cosmic microwave background (CMB) using data from the first season of observations with SPTpol, the polarization-sensitive receiver currently installed on the South Pole Telescope (SPT). The observations used in this work cover 100~sqdeg of sky with arcminute resolution at $150,$GHz. We report the $E$-mode angular auto-power spectrum ($EE$) and the temperature-$E$-mode angular cross-power spectrum ($TE$) over the multipole range $500 < ell leq5000$. These power spectra improve on previous measurements in the high-$ell$ (small-scale) regime. We fit the combination of the SPTpol power spectra, data from planck, and previous SPT measurements with a six-parameter LCDM cosmological model. We find that the best-fit parameters are consistent with previous results. The improvement in high-$ell$ sensitivity over previous measurements leads to a significant improvement in the limit on polarized point-source power: after masking sources brighter than 50,mJy in unpolarized flux at 150,GHz, we find a 95% confidence upper limit on unclustered point-source power in the $EE$ spectrum of $D_ell = ell (ell+1) C_ell / 2 pi < 0.40 mu{mbox{K}}^2$ at $ell=3000$, indicating that future $EE$ measurements will not be limited by power from unclustered point sources in the multipole range $ell < 3600$, and possibly much higher in $ell.$
Aims. One of the main probes for systematic errors in the cosmic shear signal are the division of the shear field into E- and B-mode shear, where gravitational lensing only produces the former. As shown in a recent note, all currently used E-/B-mode separation methods for the shear correlation functions xi_pm require them to be measured to arbitrarily small and/or large separations which is of course not feasible in practice. Methods. We derive second-order shear statistics which provide a clean separation into E- and B-modes from measurements of xi_pm(theta) over a finite interval only. We call these new statistics the circle and ring statistics, respectively; the latter is obtained by an integral over the former. The mathematical properties of these new shear statistics are obtained, as well as specific expressions for applying them to observed data. Results. It is shown that an E-/B-mode separation can be performed on measurements of xi_pm over a finite interval in angular separation, using the ring statistics. We furthermore generalize this result to derive the most general class of second-order shear statistics which provide a separation of E- and B-mode shear on a given angular interval theta_min <= theta <= theta_max. Our results will be of practical use particularly for future cosmic shear surveys where highly precise measurements of the shear will become available and where control of systematics will be mandatory.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
