Discovery of a Giant Lya Emitter Near the Reionization Epoch
astro-ph
/ Authors
Masami Ouchi, Yoshiaki Ono, Eiichi Egami, Tomoki Saito, Masamune Oguri, Patrick J. McCarthy, Duncan Farrah, Nobunari Kashikawa, Ivelina Momcheva, Kazuhiro Shimasaku
and 17 more authors
Kouichiro Nakanishi, Hisanori Furusawa, Masayuki Akiyama, James S. Dunlop, Angela M. J. Mortier, Sadanori Okamura, Masao Hayashi, Michele Cirasuolo, Alan Dressler, Masanori Iye, Matt. J. Jarvis, Tadayuki Kodama, Crystal L. Martin, Ross J. McLure, Kouji Ohta, Toru Yamada, Michitoshi Yoshida
/ Abstract
We report the discovery of a giant Lya emitter (LAE) with a Spitzer/IRAC counterpart near the reionization epoch at z=6.595. The giant LAE is found from the extensive 1 deg^2 Subaru narrow-band 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 narrow-band object with L(Lya) = 3.9+/-0.2 x 10^43 erg/s in our survey volume of 10^6 Mpc^3, but also a spatially extended Lya nebula with the largest isophotal area whose major axis is at least ~3''. This object is more likely to be a large Lya nebula with a size of >~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 v(FWHM)=251+/-21 km/s, and that the line-center velocity changes by ~60 km/s in a 10-kpc range. The stellar mass and star-formation rate are estimated to be 0.9-5.0 x 10^10 Mo and >34 Mo/yr, 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 inter-galactic medium.