Using Hubble Space Telescope ( HST ) and Spitzer IRAC imaging , we report the discovery of a very bright strongly lensed Lyman break galaxy ( LBG ) candidate at z \sim 7.6 in the field of the massive galaxy cluster Abell 1689 ( z = 0.18 ) .
The galaxy candidate , which we refer to as A1689-zD1 , shows a strong z _ { 850 } - J _ { 110 } break of at least 2.2 mag and is completely undetected ( < 1 \sigma ) in HST Advanced Camera for Surveys ( ACS ) g _ { 475 } , r _ { 625 } , i _ { 775 } , and z _ { 850 } data .
These properties , combined with the very blue J _ { 110 } - H _ { 160 } and H _ { 160 } - [ 4.5 \mu m ] colors , are exactly the properties of an z \sim 7.6 LBG and can only be reasonably fit by a star-forming galaxy at z = 7.6 \pm 0.4 ( \chi ^ { 2 } _ { \nu } = 1.1 ) .
Attempts to reproduce these properties with a model galaxy at z < 4 yield particularly poor fits ( \chi ^ { 2 } _ { \nu } \geq 25 ) .
A1689-zD1 has an observed ( lensed ) magnitude of 24.7 AB ( 8 \sigma ) in the NICMOS H _ { 160 } band and is \sim 1.3 mag brighter than the brightest-known z _ { 850 } -dropout galaxy .
When corrected for the cluster magnification of \sim 9.3 at z \sim 7.6 , the candidate has an intrinsic magnitude of H _ { 160 } = 27.1 AB , or about an L _ { * } galaxy at z \sim 7.6 .
The source-plane deprojection shows that the star formation is occurring in compact knots of size \lesssim 300 pc .
The best-fit stellar population synthesis models yield a median redshift of 7.6 , stellar masses ( 1.6 - 3.9 ) \times 10 ^ { 9 } M _ { \sun } , stellar ages 45 - 320 Myr , star-formation rates \lesssim 7.6 M _ { \sun } yr ^ { -1 } , and low reddening with A _ { V } \leq 0.3 .
These properties are generally similar to those of LBGs found at z \sim 5 - 6 .
The inferred stellar ages suggest a formation redshift of z \sim 8 - 10 ( t \lesssim 0.63 Gyr ) .
A1689-zD1 is the brightest observed , highly reliable z > 7.0 galaxy candidate found to date .