Large-Scale Cosmic Shear Measurements

Nick Kaiser; Gillian Wilson; Gerard A. Luppino

paper

Large-Scale Cosmic Shear Measurements

arXiv:astro-ph/0003338

Abstract

We present estimates of the gravitational lensing shear variance obtained from images taken at the CFHT using the UH8K CCD mosaic camera. Six fields were observed for a total of 1 hour each in V and I, resulting in catalogs containing approximately 20,000 $g a l a x i es p er f i e l d, w i t h p r o p er l y c a l ib r a t e d an d o pt ima l l y w e i g h t e d s h e a r es t ima t es . T h ese w er e a v er a g e d in ce l l so f s i z esr an g in g f r o m 1^{'} .875 t o 3 0^{'} t oo b t ain es t ima t eso f t h ecos mi cs h e a r v a r ian ce$ <\barγ^2> $, w i t h u n cer t ain t y es t ima t e df r o m t h esc a tt er am o n g t h ees t ima t es f or t h e 6 f i e l d s . O u r m os t r e l iab l ees t ima t or f or cos mi cs h e a r i s p r o v i d e d b y t h ecr oss - cor r e l a t i o n o f t h es h e a r m e a s u r e d in t h e tw o p a ss ban d s . A t sc a l es$ \lsim 10' $t h er es u l t s a r e in g oo d a g r ee m e n tw i t h t h oseo f v anW a er b e k ee t a l .2000, B a co n e t a l .2000 an d W i tt man e t a l .2000 an d w i t h c u r r e n tl y f a s hi o nab l ecos m o l o g i c a l m o d e l s . A tl a r g er sc a l es t h es h e a r v a r ian ce f a l l s b e l o w t h e t h eor e t i c a l p r e d i c t i o n s, an d o n t h e l a r g es t sc a l es w e f in d an u l l d e t ec t i o n o f s h e a r v a r ian ce a v er a g e d in 3 0^{'} ce l l so f$ <\barγ^2 > = (0.28 \pm 1.84) \times 10^{-5}$.

submitted to ApJ Letters