Ly{alpha} EMITTERS AT z = 7 IN THE SUBARU/XMM-NEWTON DEEP SURVEY FIELD: PHOTOMETRIC CANDIDATES AND LUMINOSITY FUNCTION

• Published in: The Astrophysical journal Vol. 722; no. 1
• Main Authors: Ota, Kazuaki, Ouchi, Masami, Iye, Masanori, Kashikawa, Nobunari, Kobayashi, Masakazu A. R., Morokuma, Tomoki, Furusawa, Hisanori, Shimasaku, Kazuhiro, Totani, Tomonori, Nagashima, Masahiro, Harayama, Atsushi, Kodaka, Natsuki, Tajitsu, Akito, Hattori, Takashi
• Format: Journal Article
• Language: English
• Published: United States 10.10.2010
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BOSONS; COSMIC GAMMA BURSTS; COSMIC RADIATION; COSMIC RADIO SOURCES; COSMOLOGY; ELEMENTARY PARTICLES; ELEMENTS; EVOLUTION; GALACTIC EVOLUTION; GALAXIES; HYDROGEN; IONIZING RADIATIONS; LUMINOSITY; MASSLESS PARTICLES; NONMETALS; OPTICAL PROPERTIES; PHOTONS; PHYSICAL PROPERTIES; PRIMARY COSMIC RADIATION; QUASARS; RADIATIONS; TELESCOPES; UNIVERSE
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/722/1/803

We conducted a deep narrowband NB973 (FWHM = 200 A centered at 9755 A) survey of z = 7 Ly{alpha} emitters (LAEs) in the Subaru/XMM-Newton Deep Survey Field, using the fully depleted CCDs newly installed on the Subaru Telescope Suprime-Cam, which is twice more sensitive to z = 7 Ly{alpha} at {approx}1 {mu}m than the previous CCDs. Reaching the depth 0.5 mag deeper than our previous survey in the Subaru Deep Field that led to the discovery of a z = 6.96 LAE, we detected three probable z = 7 LAE candidates. Even if all the candidates are real, the Ly{alpha} luminosity function (LF) at z = 7 shows a significant deficit from the LF at z = 5.7 determined by previous surveys. The LAE number and Ly{alpha} luminosity densities at z = 7 are {approx}7.7%-54% and {approx}5.5%-39%, respectively, of those at z = 5.7, to the Ly{alpha} line luminosity limit of L(Ly{alpha}) {approx}> 9.2 x 10{sup 42} erg s{sup -1}. This could be due to evolution of the LAE population at these epochs as a recent galaxy evolution model predicts that the LAE modestly evolves from z = 5.7 to 7. However, even after correcting for this effect of galaxy evolution on the decrease in LAE number density, the z = 7 Ly{alpha} LF still shows a deficit from z = 5.7 LF. This might reflect the attenuation of Ly{alpha} emission by neutral hydrogen remaining at the epoch of reionization and suggests that reionization of the universe might not be complete yet at z = 7. If we attribute the density deficit to reionization, the intergalactic medium transmission for Ly{alpha} photons at z = 7 would be 0.4 {<=} T {sup IGM}{sub Ly{alpha} {<=}} 1, supporting the possible higher neutral fraction at the earlier epochs at z > 6 suggested by the previous surveys of z = 5.7-7 LAEs, z {approx} 6 quasars, and z > 6 gamma-ray bursts.