TY - JOUR
T1 - A NEW CONSTRAINT on the Lyα FRACTION of UV VERY BRIGHT GALAXIES at REDSHIFT 7
AU - Furusawa, Hisanori
AU - Kashikawa, Nobunari
AU - Kobayashi, Masakazu A.R.
AU - Dunlop, James S.
AU - Shimasaku, Kazuhiro
AU - Takata, Tadafumi
AU - Sekiguchi, Kazuhiro
AU - Naito, Yoshiaki
AU - Furusawa, Junko
AU - Ouchi, Masami
AU - Nakata, Fumiaki
AU - Yasuda, Naoki
AU - Okura, Yuki
AU - Taniguchi, Yoshiaki
AU - Yamada, Toru
AU - Kajisawa, Masaru
AU - Fynbo, Johan P.U.
AU - Fèvre, Olivier Le
PY - 2016/5/1
Y1 - 2016/5/1
N2 - We study the extent to which very bright (-23.0 < MUV < -21.75) Lyman-break-selected galaxies at redshifts z ≃ 7 display detectable Lyα emission. To explore this issue, we obtained follow-up optical spectroscopy of 9 z ≃ 7 galaxies from a parent sample of 24 z ≃ 7 galaxy candidates selected from the 1.65 deg2 COSMOS-UltraVISTA and SXDS-UDS survey fields using the latest near-infrared public survey data, and new ultra-deep Subaru z-band imaging (which we also present and describe in this paper). Our spectroscopy yielded only one possible detection of Lyα at z=7.168 with a rest-frame equivalent width = EW 3.7+ 1.7-0 1.1 The relative weakness of this line, combined with our failure to detect Lyα emission from the other spectroscopic targets, allows us to place a new upper limit on the prevalence of strong Lyα emission at these redshifts. For conservative calculation and to facilitate comparison with previous studies at lower redshifts, we derive a 1 upper limit on the fraction of UV-bright galaxies at z ≃ 7 that display EW0 > 50 A, which we estimate to be <0.23. This result may indicate a weak trend where the fraction of strong Lyα emitters ceases to rise, and possibly falls between z≃6 and z ≃ 7. Our results also leave open the possibility that strong Lyα may still be more prevalent in the brightest galaxies in the reionization era than their fainter counterparts. A larger spectroscopic sample of galaxies is required to derive a more reliable constraint on the neutral hydrogen fraction at z ∼ 7 based on the Lyα fraction in the bright galaxies.
AB - We study the extent to which very bright (-23.0 < MUV < -21.75) Lyman-break-selected galaxies at redshifts z ≃ 7 display detectable Lyα emission. To explore this issue, we obtained follow-up optical spectroscopy of 9 z ≃ 7 galaxies from a parent sample of 24 z ≃ 7 galaxy candidates selected from the 1.65 deg2 COSMOS-UltraVISTA and SXDS-UDS survey fields using the latest near-infrared public survey data, and new ultra-deep Subaru z-band imaging (which we also present and describe in this paper). Our spectroscopy yielded only one possible detection of Lyα at z=7.168 with a rest-frame equivalent width = EW 3.7+ 1.7-0 1.1 The relative weakness of this line, combined with our failure to detect Lyα emission from the other spectroscopic targets, allows us to place a new upper limit on the prevalence of strong Lyα emission at these redshifts. For conservative calculation and to facilitate comparison with previous studies at lower redshifts, we derive a 1 upper limit on the fraction of UV-bright galaxies at z ≃ 7 that display EW0 > 50 A, which we estimate to be <0.23. This result may indicate a weak trend where the fraction of strong Lyα emitters ceases to rise, and possibly falls between z≃6 and z ≃ 7. Our results also leave open the possibility that strong Lyα may still be more prevalent in the brightest galaxies in the reionization era than their fainter counterparts. A larger spectroscopic sample of galaxies is required to derive a more reliable constraint on the neutral hydrogen fraction at z ∼ 7 based on the Lyα fraction in the bright galaxies.
KW - cosmology: observations
KW - dark ages, reionization, first stars
KW - galaxies: evolution
KW - galaxies: highredshift
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U2 - 10.3847/0004-637X/822/1/46
DO - 10.3847/0004-637X/822/1/46
M3 - Article
AN - SCOPUS:84968830579
VL - 822
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
M1 - 46
ER -