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Rozo E.,University of Chicago | Rozo E.,Kavli Institute for Cosmological Physics | Bartlett J.G.,University Paris Diderot | Bartlett J.G.,Jet Propulsion Laboratory | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

We demonstrate that optical data from Sloan Digital Sky Survey, X-ray data from ROSAT and Chandra, and Sunyaev-Zel'dovich (SZ) data from Planck can be modelled in a fully self-consistent manner. After accounting for systematic errors and allowing for property covariance, we find that scaling relations derived from optical and X-ray selected cluster samples are consistent with one another. Moreover, these cluster scaling relations satisfy several non-trivial spatial abundance constraints and closure relations. Given the good agreement between optical and X-ray samples, we combine the two and derive a joint set of LX-M and YSZ-M relations. Our best-fitting YSZ-M relation is in good agreement with the observed amplitude of the thermal SZ power spectrum for a Wilkinson Microwave Anisotropy Probe 7 cosmology, and is consistent with the masses for the two CLASH galaxy clusters published thus far. We predict the halo masses of the remaining z ≤ 0.4 CLASH clusters, and use our scaling relations to compare our results with a variety of X-ray and weak lensing cluster masses from the literature. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Source

Schmidt F.,California Institute of Technology | Rozo E.,University of Chicago | Rozo E.,Kavli Institute for Cosmological Physics
Astrophysical Journal | Year: 2011

Large catalogs of shear-selected peaks have recently become a reality. In order to properly interpret the abundance and properties of these peaks, it is necessary to take into account the effects of the clustering of source galaxies, among themselves and with the lens. In addition, the preferred selection of magnified galaxies in a flux- and size-limited sample leads to fluctuations in the apparent source density that correlate with the lensing field. In this paper, we investigate these issues for two different choices of shear estimators that are commonly in use today: globally normalized and locally normalized estimators. While in principle equivalent, in practice these estimators respond differently to systematic effects such as magnification and cluster member dilution. Furthermore, we find that the answer to the question of which estimator is statistically superior depends on the specific shape of the filter employed for peak finding; suboptimal choices of the estimator+filter combination can result in a suppression of the number of high peaks by orders of magnitude. Magnification and size bias generally act to increase the signal-to-noise ν of shear peaks; for high peaks the boost can be as large as Δν 1-2. Due to the steepness of the peak abundance function, these boosts can result in a significant increase in the observed abundance of shear peaks. A companion paper investigates these same issues within the context of stacked weak-lensing mass estimates. © 2011. The American Astronomical Society. All rights reserved. Source

Rozo E.,University of Chicago | Rozo E.,Kavli Institute for Cosmological Physics | Wu H.-Y.,Kavli Institute for Particle Astrophysics and Cosmology | Schmidt F.,California Institute of Technology
Astrophysical Journal | Year: 2011

When extracting the weak lensing shear signal, one may employ either locally normalized or globally normalized shear estimators. The former is the standard approach when estimating cluster masses, while the latter is the more common method among peak finding efforts. While both approaches have identical signal-to-noise in the weak lensing limit, it is possible that higher order corrections or systematic considerations make one estimator preferable over the other. In this paper, we consider the efficacy of both estimators within the context of stacked weak lensing mass estimation in the Dark Energy Survey (DES). We find that the two estimators have nearly identical statistical precision, even after including higher order corrections, but that these corrections must be incorporated into the analysis to avoid observationally relevant biases in the recovered masses. We also demonstrate that finite bin-width effects may be significant if not properly accounted for, and that the two estimators exhibit different systematics, particularly with respect to contamination of the source catalog by foreground galaxies. Thus, the two estimators may be employed as a systematic cross-check of each other. Stacked weak lensing in the DES should allow for the mean mass of galaxy clusters to be calibrated to 2% precision (statistical only), which can improve the figure of merit of the DES cluster abundance experiment by a factor of 3 relative to the self-calibration expectation. A companion paper investigates how the two types of estimators considered here impact weak lensing peak finding efforts. © 2011. The American Astronomical Society. All rights reserved. Source

Dodelson S.,Fermi National Accelerator Laboratory | Dodelson S.,University of Chicago | Dodelson S.,Kavli Institute for Cosmological Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

One of the most promising ways of detecting primordial gravitational waves generated during inflation is to observe B-modes of polarization, generated by Thomson scattering after reionization, in the cosmic microwave background. Large scale foregrounds though are expected to be a major systematic issue, so-in the event of a tentative detection-an independent confirmation of large scale gravitational waves would be almost essential. Previous authors have suggested searching for the analogous mode of cosmic shear in weak lensing surveys but have shown that the signal to noise of this mode is marginal at best. This argument is reconsidered here, accounting for the cross correlations of the polarization and lensing B-modes. A lensing survey can potentially strengthen the argument for a detection of primordial gravitational waves, although it is unlikely to help constrain the amplitude of the signal. © 2010 The American Physical Society. Source

News Article | December 19, 2011
Site: techcrunch.com

Struq, a retargeting ad platform is currently in negotiations to close an $8 million financing round, according to CEO Sam Barnett as quoted by the Financial Times over the weekend. Competitors include Criteo, Teracent and Tumri have similar platforms, which ‘re-target’ ads based on a user’s behaviour online, but Struq has grown form a bootstrapped base so it looks like this will be a growth funding round rather than a Series A.

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