Gravitational Lensing Distorts Counts of Very High Redshift Galaxies Stuart Wyithe (Univ. Melbourne), Haojing Yan (Ohio State Univ.), Rogier Windhorst (Arizona State Unv.), Shude Mao (Univ. Manchester & NAOC, China) (Based on Publication in Nature, Jan 12, 2011) AAS 217 th Meeting, Seattle, WA January 12, 2011 Stuart Wyithe (Univ. Melbourne), Haojing Yan (Ohio State Univ.), Rogier Windhorst (Arizona State Unv.), Shude Mao (Univ. Manchester & NAOC, China) (Based on Publication in Nature, Jan 12, 2011) AAS 217 th Meeting, Seattle, WA January 12, 2011

Gravitational Lensing Is Well Known Lensing of background objects by foreground galaxy clusters Lensing of background objects by individual foreground galaxies (1990) (2005) (1996)

Implication for High-redshift Studies Yet to Be Fully Explored Gravitational lensing by individual foreground galaxies amplifies background high-redshift galaxies It happens more often than we used to think The effect manifests itself by concentration of high- redshift galaxies around foreground galaxies Credit: NASA, ESA, Z. Levay and A. Feild (STScI)

High Lensing Rate at Very High Redshifts: Initial Evidence Hubble Ultra Deep Field Image, Optical + IR

About 20% of candidate galaxies at redshifts ~ are found to be very close to foreground galaxies, consistent with our prediction

Blue Band Red Band Y-band “dropouts”: candidate galaxies at redshifts ~ 8 J-band “dropouts”: candidate galaxies at redshifts ~ 10

Why This Is Important Bright distribution of galaxies at very high redshifts is crucial to our understanding of how the universe was forming galaxies in its infancy High incidence of lensing implies that there are many very faint galaxies at these very high redshifts