DISCOVERY OF A GIANT Lyα EMITTER NEAR THE REIONIZATION EPOCH

We report the discovery of a giant Ly alpha emitter (LAE) with a Spitzer/Infrared Array Camera (IRAC) counterpart near the reionization epoch at z = 6.595. The giant LAE is found from the extensive 1 deg(2) Subaru narrowband survey for z = 6.6 LAEs in the Subaru/XMM-Newton Deep Survey (SXDS) field, and subsequently identified by deep spectroscopy of Keck/DEIMOS and Magellan/IMACS. Among our 207 LAE candidates, this LAE is not only the brightest narrowband object with L(Ly alpha) = 3.9 +/- 0.2 x 10(43) erg s(-1) in our survey volume of 10(6) Mpc(3), but also a spatially extended Ly alpha nebula with the largest isophotal area whose major axis is at least similar or equal to 3 ''. This object is more likely to be a large Ly alpha nebula with a size of greater than or similar to 17 kpc than to be a strongly lensed galaxy by a foreground object. Our Keck spectrum with medium-high spectral and spatial resolutions suggests that the velocity width is nu(FWHM) = 251 +/- 21 km s(-1), and that the line-center velocity changes by similar or equal to 60 km s(-1) in a 10 kpc range. The stellar mass and star formation rate are estimated to be 0.9-5.0 x 10(10) M-circle dot and >34 M-circle dot yr(-1), respectively, from the combination of deep optical to infrared images of Subaru, UKIDSS-Ultra Deep Survey, and Spitzer/IRAC. Although the nature of this object is not yet clearly understood, this could be an important object for studying cooling clouds accreting onto a massive halo, or forming-massive galaxies with significant outflows contributing to cosmic reionization and metal enrichment of intergalactic medium.