研究成果・発表論文

The Discovery of Two Lyman \ensuremathα Emitters beyond Redshift 6 in the Subaru Deep Field

Kodaira, Keiichi,   Taniguchi, Yoshiaki,   Kashikawa, Nobunari,   Kaifu, Norio,   Ando, Hiroyasu,   Karoji, Hiroshi,   Ajiki, Masaru,   Akiyama, Masayuki,   Aoki, Kentaro,   Doi, Mamoru,   Fujita, Shinobu S.,   Furusawa, Hisanori,   Hayashino, Tomoki,   Imanishi, Masatoshi,   Iwamuro, Fumihide,   Iye, Masanori,   Kawabata, Koji S.,   Kobayashi, Naoto,   Kodama, Tadayuki,   Komiyama, Yutaka,   Kosugi, George,   Matsuda, Yuichi,   Miyazaki, Satoshi,   Mizumoto, Yoshihiko,   Motohara, Kentaro,   Murayama, Takashi,   Nagao, Tohru,   Nariai, Kyoji,   Ohta, Kouji,   Ohyama, Youichi,   Okamura, Sadanori,   Ouchi, Masami,   Sasaki, Toshiyuki,   Sekiguchi, Kazuhiro,   Shimasaku, Kazuhiro,   Shioya, Yasunori,   Takata, Tadafumi,   Tamura, Hajime,   Terada, Hiroshi,   Umemura, Masayuki,   Usuda, Tomonori,   Yagi, Masafumi,   Yamada, Toru,   Yasuda, Naoki,   & Yoshida, Michitoshi


要旨
We performed a deep optical imaging survey using a narrow-band filter (NB921) centered at \ensuremathłambda = 9196 ̊A together with i' and z'broadband filters covering an 814 arcmin$^2$area of the Subaru Deep Field. We obtained a sample of 73 strongNB921-excess objects based on the following two color criteria: z - NB921 > 1 andi' - z'> 1.3.We then obtained optical spectroscopy of nine objects in our NB921-excess sample, and identified at least two Ly\ensuremathα emitters atz=6.541 \ensuremath± 0.002 andz=6.578 \ensuremath± 0.002, each of which shows the characteristic sharp cutofftogether with continuum depression at wavelengths shortward of the line peak.The latter object is more distant than HCM-6A at z = 6.56, which is the most distant known object that has been found so far.These new data allow us to estimate the first meaningful lower limit of the star-formation rate density beyond redshift 6; \ensuremath\o̊$_SFR$ ̃ 5.2 × 10$^-4$M$_☉$yr$^-1$ Mpc$^-3$.Since it is expected that the actual density is several times higher than this value, our new observation reveals that a moderately high level of star formation activity already occurred at z ̃ 6.6.






Image
Image
Image