Opening a Window of Discovery on the Dynamic Universe

The effective number density of galaxies for weak lensing measurements in the LSST project

Chang, Chiway et al.
Jarvis, M.; Jain, B.; Kahn, S. M.; Kirkby, D.; Connolly, A.; Krughoff, S.; Peng, E.-H.; Peterson, J. R.
Publication Date: 
Friday, July 19, 2013
Type: 
Journal Articles
Citable: 
no
Category: 
Monthly Notices of the Royal Astronomical Society
Volume: 
434 Issue 2
Page #: 
2 121
Abstract: 
Future weak lensing surveys potentially hold the highest statistical power for constraining cosmological parameters compared to other cosmological probes. The statistical power of a weak lensing survey is determined by the sky coverage, the inverse of the noise in shear measurements and the galaxy number density. The combination of the latter two factors is often expressed in terms of neff – the ‘effective number density of galaxies used for weak lensing measurements’. In this work, we estimate neff for the Large Synoptic Survey Telescope (LSST) project, the most powerful ground-based lensing survey planned for the next two decades. We investigate how the following factors affect the resulting neff of the survey with detailed simulations: (1) survey time, (2) shear measurement algorithm, (3) algorithm for combining multiple exposures, (4) inclusion of data from multiple filter bands, (5) redshift distribution of the galaxies and (6) masking and blending. For the first time, we quantify in a general weak lensing analysis pipeline the sensitivity of neff to the above factors. We find that with current weak lensing algorithms, expected distributions of observing parameters, and all lensing data (r and i band, covering 18 000 degree2 of sky) for LSST, neff ≈ 37 arcmin−2 before considering blending and masking, neff ≈ 31 arcmin−2 when rejecting seriously blended galaxies and neff ≈ 26 arcmin−2 when considering an additional 15 per cent loss of galaxies due to masking. With future improvements in weak lensing algorithms, these values could be expected to increase by up to 20 per cent. Throughout the paper, we also stress the ways in which neff depends on our ability to understand and control systematic effects in the measurements.
Reviewed Under: 
LSST Publication Policy (2015 or earlier)

Financial support for LSST comes from the National Science Foundation (NSF) through Cooperative Agreement No. 1258333, the Department of Energy (DOE) Office of Science under Contract No. DE-AC02-76SF00515, and private funding raised by the LSST Corporation. The NSF-funded LSST Project Office for construction was established as an operating center under management of the Association of Universities for Research in Astronomy (AURA).  The DOE-funded effort to build the LSST camera is managed by the SLAC National Accelerator Laboratory (SLAC).
The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 to promote the progress of science. NSF supports basic research and people to create knowledge that transforms the future.
NSF and DOE will continue to support LSST in its Operations phase. They will also provide support for scientific research with LSST data.   




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