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20 April 2024 |
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A New Constraint on the Ly$alpha$ Fraction of UV Very Bright Galaxies at Redshift 7 | | Hisanori Furusawa
; Nobunari Kashikawa
; Masakazu A. R. Kobayashi
; James S. Dunlop
; Kazuhiro Shimasaku
; Tadafumi Takata
; Kazuhiro Sekiguchi
; Yoshiaki Naito
; Junko Furusawa
; Masami Ouchi
; Fumiaki Nakata
; Naoki Yasuda
; Yuki Okura
; Yoshiaki Taniguchi
; Toru Yamada
; Masaru Kajisawa
; Johan P. U. Fynbo
; Olivier Le Fevre
; | | Date: |
8 Apr 2016 | | Abstract: | We study the extent to which very bright (-23.0 < MUV < -21.75) Lyman-break
selected galaxies at redshifts z~7 display detectable Lya emission. To explore
this issue, we have 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 sq.deg
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 has yielded only one
possible detection of Lya at z=7.168 with a rest-frame equivalent width EW_0 =
3.7 (+1.7/-1.1) Angstrom. The relative weakness of this line, combined with our
failure to detect Lya emission from the other spectroscopic targets allows us
to place a new upper limit on the prevalence of strong Lya emission at these
redshifts. For conservative calculation and to facilitate comparison with
previous studies at lower redshifts, we derive a 1-sigma upper limit on the
fraction of UV bright galaxies at z~7 that display EW_0 > 50 Angstrom, which we
estimate to be < 0.23. This result may indicate a weak trend where the fraction
of strong Lya emitters ceases to rise, and possibly falls between z~6 and z~7.
Our results also leave open the possibility that strong Lya 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
Lya fraction in the bright galaxies. | | Source: | arXiv, 1604.2214 | | Services: | Forum | Review | PDF | Favorites | |
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