We present the results of a new search for galaxies at redshift z ~ 9 in the
first two Hubble Frontier Fields with completed HST WFC3/IR and ACS imaging. To
ensure robust photometric redshift solutions, and to minimize incompleteness,
we confine our search to objects with H_160 < 28.6 (AB mag), consider only
image regions with an rms noise sigma_160 > 30 mag (within a 0.5-arcsec
diameter aperture), and insist on detections in both H_160 and J_140. The
result is a survey covering an effective area (after accounting for
magnification) of 10.9 sq. arcmin, which yields 12 galaxies at 8.4 < z < 9.5.
Within the Abell-2744 cluster and parallel fields we confirm the three
brightest objects reported by Ishigaki et al. (2014), but recover only one of
the four z > 8.4 sources reported by Zheng et al. (2014). In the
MACSJ0416.1-240 cluster field we report five objects, and explain why each of
these eluded detection or classification as z ~ 9 galaxies in the published
searches of the shallower CLASH data. Finally, we uncover four z ~ 9 galaxies
from the previously unsearched MACSJ0416.1-240 parallel field. Based on the
published magnification maps we find that only one of these 12 galaxies is
likely boosted by more than a factor of two by gravitational lensing.
Consequently we are able to perform a fairly straightforward reanalysis of the
normalization of the z ~ 9 UV galaxy luminosity function as explored previously
in the HUDF12 programme. We conclude that the new data strengthen the evidence
for a continued smooth decline in UV luminosity density (and hence
star-formation rate density) from z ~ 8 to z ~ 9, contrary to recent reports of
a marked drop-off at these redshifts. This provides further support for the
scenario in which early galaxy evolution is sufficiently extended to explain
cosmic reionization.
Description
[1412.1472] New redshift z ~ 9 galaxies in the Hubble Frontier Fields: Implications for early evolution of the UV luminosity density
%0 Generic
%1 mcleod2014redshift
%A McLeod, Derek J.
%A McLure, Ross J.
%A Dunlop, James S.
%A Robertson, Brant E.
%A Ellis, Richard S.
%A Targett, Thomas T.
%D 2014
%K function highz luminosity
%T New redshift z ~ 9 galaxies in the Hubble Frontier Fields: Implications
for early evolution of the UV luminosity density
%U http://arxiv.org/abs/1412.1472
%X We present the results of a new search for galaxies at redshift z ~ 9 in the
first two Hubble Frontier Fields with completed HST WFC3/IR and ACS imaging. To
ensure robust photometric redshift solutions, and to minimize incompleteness,
we confine our search to objects with H_160 < 28.6 (AB mag), consider only
image regions with an rms noise sigma_160 > 30 mag (within a 0.5-arcsec
diameter aperture), and insist on detections in both H_160 and J_140. The
result is a survey covering an effective area (after accounting for
magnification) of 10.9 sq. arcmin, which yields 12 galaxies at 8.4 < z < 9.5.
Within the Abell-2744 cluster and parallel fields we confirm the three
brightest objects reported by Ishigaki et al. (2014), but recover only one of
the four z > 8.4 sources reported by Zheng et al. (2014). In the
MACSJ0416.1-240 cluster field we report five objects, and explain why each of
these eluded detection or classification as z ~ 9 galaxies in the published
searches of the shallower CLASH data. Finally, we uncover four z ~ 9 galaxies
from the previously unsearched MACSJ0416.1-240 parallel field. Based on the
published magnification maps we find that only one of these 12 galaxies is
likely boosted by more than a factor of two by gravitational lensing.
Consequently we are able to perform a fairly straightforward reanalysis of the
normalization of the z ~ 9 UV galaxy luminosity function as explored previously
in the HUDF12 programme. We conclude that the new data strengthen the evidence
for a continued smooth decline in UV luminosity density (and hence
star-formation rate density) from z ~ 8 to z ~ 9, contrary to recent reports of
a marked drop-off at these redshifts. This provides further support for the
scenario in which early galaxy evolution is sufficiently extended to explain
cosmic reionization.
@misc{mcleod2014redshift,
abstract = {We present the results of a new search for galaxies at redshift z ~ 9 in the
first two Hubble Frontier Fields with completed HST WFC3/IR and ACS imaging. To
ensure robust photometric redshift solutions, and to minimize incompleteness,
we confine our search to objects with H_{160} < 28.6 (AB mag), consider only
image regions with an rms noise sigma_{160} > 30 mag (within a 0.5-arcsec
diameter aperture), and insist on detections in both H_{160} and J_{140}. The
result is a survey covering an effective area (after accounting for
magnification) of 10.9 sq. arcmin, which yields 12 galaxies at 8.4 < z < 9.5.
Within the Abell-2744 cluster and parallel fields we confirm the three
brightest objects reported by Ishigaki et al. (2014), but recover only one of
the four z > 8.4 sources reported by Zheng et al. (2014). In the
MACSJ0416.1-240 cluster field we report five objects, and explain why each of
these eluded detection or classification as z ~ 9 galaxies in the published
searches of the shallower CLASH data. Finally, we uncover four z ~ 9 galaxies
from the previously unsearched MACSJ0416.1-240 parallel field. Based on the
published magnification maps we find that only one of these 12 galaxies is
likely boosted by more than a factor of two by gravitational lensing.
Consequently we are able to perform a fairly straightforward reanalysis of the
normalization of the z ~ 9 UV galaxy luminosity function as explored previously
in the HUDF12 programme. We conclude that the new data strengthen the evidence
for a continued smooth decline in UV luminosity density (and hence
star-formation rate density) from z ~ 8 to z ~ 9, contrary to recent reports of
a marked drop-off at these redshifts. This provides further support for the
scenario in which early galaxy evolution is sufficiently extended to explain
cosmic reionization.},
added-at = {2014-12-05T10:01:29.000+0100},
author = {McLeod, Derek J. and McLure, Ross J. and Dunlop, James S. and Robertson, Brant E. and Ellis, Richard S. and Targett, Thomas T.},
biburl = {https://www.bibsonomy.org/bibtex/2452d4bc3ac2b18db398e6e75bf3a1aee/miki},
description = {[1412.1472] New redshift z ~ 9 galaxies in the Hubble Frontier Fields: Implications for early evolution of the UV luminosity density},
interhash = {e70fec462e9ec759ff5d15da00a17bb9},
intrahash = {452d4bc3ac2b18db398e6e75bf3a1aee},
keywords = {function highz luminosity},
note = {cite arxiv:1412.1472Comment: 14 pages, 7 figures, submitted to MNRAS},
timestamp = {2014-12-05T10:01:29.000+0100},
title = {New redshift z ~ 9 galaxies in the Hubble Frontier Fields: Implications
for early evolution of the UV luminosity density},
url = {http://arxiv.org/abs/1412.1472},
year = 2014
}