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.
Beschreibung
[1604.02214] A New Constraint on the Ly$\alpha$ Fraction of UV Very Bright Galaxies at Redshift 7
%0 Generic
%1 furusawa2016constraint
%A Furusawa, Hisanori
%A Kashikawa, Nobunari
%A Kobayashi, Masakazu A. R.
%A Dunlop, James S.
%A Shimasaku, Kazuhiro
%A Takata, Tadafumi
%A Sekiguchi, Kazuhiro
%A Naito, Yoshiaki
%A Furusawa, Junko
%A Ouchi, Masami
%A Nakata, Fumiaki
%A Yasuda, Naoki
%A Okura, Yuki
%A Taniguchi, Yoshiaki
%A Yamada, Toru
%A Kajisawa, Masaru
%A Fynbo, Johan P. U.
%A Fevre, Olivier Le
%D 2016
%K emitters evolution lya redshift
%T A New Constraint on the Ly$\alpha$ Fraction of UV Very Bright Galaxies
at Redshift 7
%U http://arxiv.org/abs/1604.02214
%X 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.
@misc{furusawa2016constraint,
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.},
added-at = {2016-04-11T17:52:28.000+0200},
author = {Furusawa, Hisanori and Kashikawa, Nobunari and Kobayashi, Masakazu A. R. and Dunlop, James S. and Shimasaku, Kazuhiro and Takata, Tadafumi and Sekiguchi, Kazuhiro and Naito, Yoshiaki and Furusawa, Junko and Ouchi, Masami and Nakata, Fumiaki and Yasuda, Naoki and Okura, Yuki and Taniguchi, Yoshiaki and Yamada, Toru and Kajisawa, Masaru and Fynbo, Johan P. U. and Fevre, Olivier Le},
biburl = {https://www.bibsonomy.org/bibtex/2d10bc733c4e76d9f4271130055554077/miki},
description = {[1604.02214] A New Constraint on the Ly$\alpha$ Fraction of UV Very Bright Galaxies at Redshift 7},
interhash = {182c3e1ae8aeef81b46a2af354393a78},
intrahash = {d10bc733c4e76d9f4271130055554077},
keywords = {emitters evolution lya redshift},
note = {cite arxiv:1604.02214Comment: 20 pages, 7 figures, accepted for publication in ApJ},
timestamp = {2016-04-11T17:52:28.000+0200},
title = {A New Constraint on the Ly$\alpha$ Fraction of UV Very Bright Galaxies
at Redshift 7},
url = {http://arxiv.org/abs/1604.02214},
year = 2016
}