15297769
Measurement and calibration of noise bias in weak lensing galaxy shape estimation
Weak gravitational lensing has the potential to constrain cosmological parameters to high 
precision. However, as shown by the Shear Testing Programmes and Gravitational lensing 
Accuracy Testing challenges, measuring galaxy shears is a non-trivial task: various methods 
introduce different systematic biases which have to be accounted for. We investigate how 
pixel noise on the image affects the bias on shear estimates from a maximum likelihood 
forward model-fitting approach using a sum of co-elliptical Sersic profiles, in complement 
to the theoretical approach of an associated paper. We evaluate the bias using a simple but 
realistic galaxy model and find that the effects of noise alone can cause biases of the order of 
1–10 per cent on measured shears, which is significant for current and future lensing surveys. 
We evaluate a simulation-based calibration method to create a bias model as a function of 
galaxy properties and observing conditions. This model is then used to correct the simulated 
measurements. We demonstrate that, for the simple case in which the correct range of galaxy 
models is used in the fit, the calibration method can reduce noise bias to the level required for 
estimating cosmic shear in upcoming lensing surveys.
118354862
Maximizing Kepler science return per telemetered pixel: Searching the habitable zones of the brightest stars 1
In today's mailing, Hogg et al. propose image modeling techniques to maintain 10-ppm-level precision photometry in Kepler data with only two working reaction wheels. While these results are relevant to many scientific goals for the repurposed mission, all modeling efforts so far have used a toy model of the Kepler telescope. Because the two-wheel performance of Kepler remains to be determined, we advocate for the consideration of an alternate strategy for a >1 year program that maximizes the science return from the "low-torque" fields across the ecliptic plane. Assuming we can reach the precision of the original Kepler mission, we expect to detect 800 new planet candidates in the first year of such a mission. Our proposed strategy has benefits for transit timing variation and transit duration variation studies, especially when considered in concert with the future TESS mission. We also expect to help address the first key science goal of Kepler: the frequency of planets in the habitable zone as a function of spectral type.
50599515
Gravitational Lensing Accuracy Testing 2010 (GREAT10) Challenge Handbook
GRavitational lEnsing Accuracy Testing 2010 (GREAT10) is a public image analysis challenge aimed at the development of algorithms to analyze astronomical images. Specifically, the challenge is to measure varying image distortions in the presence of a variable convolution kernel, pixelization and noise. This is the second in a series of challenges set to the astronomy, computer science and statistics communities, providing a structured environment in which methods can be improved and tested in preparation for planned astronomical surveys. GREAT10 extends upon previous work by introducing variable fields into the challenge. The "Galaxy Challenge" involves the precise measurement of galaxy shape distortions, quantified locally by two parameters called shear, in the presence of a known convolution kernel. Crucially, the convolution kernel and the simulated gravitational lensing shape distortion both now vary as a function of position within the images, as is the case for real data. In addition, we introduce the "Star Challenge" that concerns the reconstruction of a variable convolution kernel, similar to that in a typical astronomical observation. This document details the GREAT10 Challenge for potential participants. Continually updated information is also available from www.greatchallenges.info.
118584751
Sérsic galaxy models in weak lensing shape measurement: model bias, noise bias and their interaction
Cosmic shear is a powerful probe of cosmological parameters, but its potential can be fully utilised only if galaxy shapes are measured with great accuracy. Two major effects have been identified which are likely to account for most of the bias for maximum likelihood methods in recent shear measurement challenges. Model bias occurs when the true galaxy shape is not well represented by the fitted model. Noise bias occurs due to the non-linear relationship between image pixels and galaxy shape. In this paper we investigate the potential interplay between these two effects when an imperfect model is used in the presence of high noise. We present analytical expressions for this bias, which depends on the residual difference between the model and real data. They can lead to biases not accounted for in previous calibration schemes. By measuring the model bias, noise bias and their interaction, we provide a complete statistical framework for measuring galaxy shapes with model fitting methods from GRavitational lEnsing Accuracy Testing (GREAT) like images. We demonstrate the noise and model interaction bias using a simple toy model, which indicates that this effect can potentially be significant. Using real galaxy images from the Cosmological Evolution Survey (COSMOS) we quantify the strength of the model bias, noise bias and their interaction. We find that the interaction term is often a similar size to the model bias term, and is smaller than the requirements of the current and shortly upcoming galaxy surveys.
18408699
Broken R Parity, Neutrino Anomalies and Collider Tests
The solar and atmospheric neutrino anomalies constitute the only solid and most remarkable evidence for physics beyond the Standard Model, indicating that the lepton mixing matrix is fundamentally distinct from that describing the quarks. Here I will report on how supersymmetry with spontaneously or bilinearly broken R Parity provides a predictive theory for neutrino mass and mixing which leads to a solution of neutrino anomalies which can be clearly tested at high energy accelerators.