2015/09/18 by Rupert A. C. Croft, Croft, Rupert A. C., Peter E. Freeman +5
Engineering · Mathematics · Physics and Astronomy · #Advanced Measurement and Metrology Techniques #Advanced Statistical Methods and Models #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena
paper · pdf · doi:10.48550/arxiv.1509.05619
openalex publication_date 2015/09/18 · openalex created_date 2022/10/01 · openalex updated_date 2026/07/28
The intrinsic scatter in the ellipticities of galaxies about the mean shape,\nknown as "shape noise," is the most important source of noise in weak lensing\nshear measurements. Several approaches to reducing shape noise have recently\nbeen put forward, using information beyond photometry, such as radio\npolarization and optical spectroscopy. Here we investigate how well the\nintrinsic ellipticities of galaxies can be predicted using other, exclusively\nphotometric parameters. These parameters (such as galaxy colours) are already\navailable in the data and do not necessitate additional, often expensive\nobservations. We apply two regression techniques, generalized additive models\n(GAM) and projection pursuit regression (PPR) to the publicly released data\ncatalog of galaxy properties from CFHTLenS. In our simple analysis we find that\nthe individual galaxy ellipticities can indeed be predicted from other\nphotometric parameters to better precision than the scatter about the mean\nellipticity. This means that without additional observations beyond photometry\nthe ellipticity contribution to the shear can be measured to higher precision,\ncomparable to using a larger sample of galaxies. Our best-fit model, achieved\nusing PPR, yields a gain equivalent to having 114.3% more galaxies. Using only\nparameters unaffected by lensing (e.g.~surface brightness, colour), the gain is\nonly ~12%.\n