217 research outputs found
The First Systematic Survey for Lyman Alpha Emitters at z=7.3 with Red-sensitive Subaru/Suprime-Cam
We have performed deep imaging surveys for LyA emitters (LAEs) at redshift
~7.3 in two blank fields, the Subaru Deep Field (SDF) and the Subaru/XMM-Newton
Deep survey Field (SXDF), using the Subaru/Suprime-Cam equipped with new
red-sensitive CCDs and a new narrow-band filter, NB1006 (lambda_c=10052 Ang,
FWHM=214 Ang). We identified four objects as LAE candidates that exhibit
luminosity excess in NB1006. By carrying out deep follow-up spectroscopy for
three of them using Subaru/FOCAS and Keck/DEIMOS, a definitively asymmetric
emission line is detected for one of them, SXDF-NB1006-2. Assuming this line is
LyA, this object is a LAE at z=7.215 which has luminosity of 1.2^{+1.5}_{-0.6}
x 10^43 [erg s-1] and a weighted skewness S_w=4.90+-0.86. Another object,
SDF-NB1006-2, shows variable photometry and is thus probably a quasar (QSO) or
an active galactic nucleus (AGN). It shows an asymmetric emission line at 10076
Ang, which may be due to either LyA at z=7.288 or [OII] at z=1.703. The third
object, SDF-NB1006-1, is likely a galaxy with temporal luminosity enhancement
associated with a supernova explosion, as the brightness of this object varies
between the observed epochs. Its spectrum does not show any emission lines. The
inferred decrease in the number density of LAEs toward higher redshift is
n_LyA(z=7.3)/n_LyA(z=5.7) = 0.05^+0.11_-0.05 from z=5.7 to 7.3 down to
L(LyA)=1.0 x 10^43 [erg s-1]. The present result is consistent with the
interpretation in previous studies that the neutral hydrogen fraction is
rapidly increasing from z=5.7 to 7.3.Comment: 12 pages, 11 figures, Accepted to Ap
The Subaru/XMM-Newton Deep Survey (SXDS) -VII. Clustering Segregation with Ultraviolet and Optical Luminosities of Lyman-Break Galaxies at z~3
We investigate clustering properties of Lyman-break galaxies (LBGs) at z~3
based on deep multi-waveband imaging data from optical to near-infrared
wavelengths in the Subaru/XMM-Newton Deep Field. The LBGs are selected by U-V
and V-z' colors in one contiguous area of 561 arcmin^2 down to z'=25.5. We
study the dependence of the clustering strength on rest-frame UV and optical
magnitudes, which can be indicators of star formation rate and stellar mass,
respectively. The correlation length is found to be a strong function of both
UV and optical magnitudes with brighter galaxies being more clustered than
faint ones in both cases. Furthermore, the correlation length is dependent on a
combination of UV and optical magnitudes in the sense that galaxies bright in
optical magnitude have large correlation lengths irrespective of UV magnitude,
while galaxies faint in optical magnitude have correlation lengths decreasing
with decreasing UV brightness. These results suggest that galaxies with large
stellar masses always belong to massive halos in which they can have various
star formation rates, while galaxies with small stellar masses reside in less
massive halos only if they have low star formation rates. There appears to be
an upper limit to the stellar mass and the star formation rate which is
determined by the mass of hosting dark halos.Comment: 16 pages, 15 figures, accepted for publication in Ap
Properties of host haloes of Lyman-break galaxies and Lyman-alpha Emitters from their number densities and angular clustering
We explore empirical relations between three different populations of
high-redshift galaxies and their hosting dark halos employing the halo model
approach. Specifically we consider Lyman-break galaxies at z\sim4 and at
z\sim5, and Lyman-Alpha emitters at z\simeq 4.86. We adopt a halo occupation
function prescription to parameterize the properties of their hosting halos and
the efficiency of halo-dependent star formation. We find that the two LBG
samples are well described by the halo model with an appropriate HOF. We obtain
constraints on properties of their hosting halos. A typical mass of hosting
halos for LBGs is 5\times10^{11}h^{-1}M_\odot and the expected number of LBGs
per halo is \sim0.5, therefore there is an approximate one-to-one
correspondence between halos and LBGs. We also find a sign of the minimum mass
of LBG hosting halos decreasing with time. We discuss implications of these
findings on the star formation history of LBGs. On the other hand, for LAEs,
our simple HOF prescription fails to reproduce simultaneously the observed
angular correlation function and the number density. This might imply either
that the distribution of LAEs within hosting halos differs from that of dark
matter, or that the strong large-scale correlation is due to the existence of
an unusual, large overdense region, and so the survey region is not a
representative of the z\sim5 universe, the definite answer should wait for a
much wider survey of LAEs at high redshifts.Comment: 12 pages, 14 figures, revised version accepted for Publication in
MNRA
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