30 research outputs found
Subaru Deep Survey V. A Census of Lyman Break Galaxies at z=4 and 5 in the Subaru Deep Fields: Photometric Properties
(abridged) We investigate photometric properties of Lyman Break Galaxies
(LBGs) at z=3.5-5.2 based on large samples of 2,600 LBGs detected in deep
(i'~27) and wide-field (1,200 arcmin^2) images taken in the Subaru Deep Field
(SDF) and the Subaru/XMM Deep Field (SXDF). The selection criteria for the LBG
samples are examined with 85 spectroscopically identified objects and by Monte
Carlo simulations. We find in the luminosity functions of LBGs (i) that the
number density of bright galaxies (M_{1700}<-22; corresponding to
SFR_{corr}>100 Msolar yr^{-1}) decreases significantly from z=4 to 5 and (ii)
that the faint-end slope of the luminosity function may become steeper towards
higher redshifts. We estimate dust extinction of z=4 LBGs with M<M^* from UV
slopes, and obtain E(B-V)=0.15+/-0.03 as the mean value. The dust extinction
remains constant with apparent luminosity, but increases with intrinsic
luminosity. We find no evolution in dust extinction between LBGs at z=3 and 4.
We investigate the evolution of UV-luminosity density at 1700A, rho, and find
that rho does not significantly change from z=3 to z=5, i.e.,
rho(z=4)/rho(z=3)=1.0+/-0.2 and rho(z=5)/rho(z=3)=0.8+/-0.4, thus the cosmic
star-formation rate (SFR) density remains constant. We find that the stellar
mass density estimated from the cosmic SFR is consistent with those derived
directly from the stellar mass function at z=0-1, but exceeds those at z~3 by a
factor of 3. We find that the ratio of the UV-luminosity density of Ly-a
emitters (LAEs) to that of LBGs is ~60% at z=5, and thus about a half of the
star formation at z=5 probably occurs in LAEs. We obtain a constraint on the
escape fraction of UV-ionizing photons produced by LBGs, f_{esc}>~0.13.Comment: 41 pages, 22 figures, ApJ in press. Paper with high resolution
figures is available at
http://hikari.astron.s.u-tokyo.ac.jp/~ouchi/work/astroph/SDS_V_VI/SDS_V.pdf
(PDF
Clustering Properties of Galaxies at z~4 in the Subaru/XMM Deep Survey Field
We study the clustering properties of about 1200 z~4 Lyman Break Galaxy (LBG)
candidates with i'<26 which are selected by color from deep BRi' imaging data
of a 618 arcmin^2 area in the Subaru/XMM-Newton Deep Field taken with Subaru
Prime Focus Camera. The contamination and completeness of our LBG sample are
evaluated, on the basis of the Hubble Deep Field North (HDFN) objects, to be
17% and 45%, respectively. We derive the angular correlation function over
theta = 2''-1000'', and find that it is fitted fairly well by a power law,
omega(theta)=A_omega theta^{-0.8}, with A_omega = 0.71 +/- 0.26. We then
calculate the correlation length r0 (in comoving units) of the two-point
spatial correlation function xi(r) = (r/r0)^{-1.8} from A_omega using the
redshift distribution of LBGs derived from the HDFN, and find r0=2.7
(+0.5/-0.6) h^{-1} Mpc in a Lambda-dominated universe (Omega_m=0.3 and
Omega_Lambda=0.7). This is twice larger than the correlation length of the dark
matter at z~4 predicted from an analytic model by Peacock & Dodds but about
twice smaller than that of bright galaxies predicted by a semi-analytic model
of Baugh et al. We find an excess of omega(theta) on small scales (theta < 5'')
departing from the power law fit over 3 sigma significance levels. Interpreting
this as due to galaxy mergers, we estimate the fraction of galaxies undergoing
mergers in our LBG sample to be 3.0 +/- 0.9%, which is significantly smaller
than those of galaxies at intermediate redshifts.Comment: 9 pages, 4 figures, to be published in ApJ Letter
Cosmic shear statistics in the Suprime-Cam 2.1 sq deg field: Constraints on Omega_m and sigma_8
We present measurements of the cosmic shear correlation in the shapes of
galaxies in the Suprime-Cam 2.1 deg^2 R_c-band imaging data. As an estimator of
the shear correlation originated from the gravitational lensing, we adopt the
aperture mass variance. We detect a non-zero E mode variance on scales between
2 and 40arcmin. We also detect a small but non-zero B mode variance on scales
larger than 5arcmin. We compare the measured E mode variance to the model
predictions in CDM cosmologies using maximum likelihood analysis. A
four-dimensional space is explored, which examines sigma_8, Omega_m, Gamma and
zs (a mean redshift of galaxies). We include three possible sources of error:
statistical noise, the cosmic variance estimated using numerical experiments,
and a residual systematic effect estimated from the B mode variance. We derive
joint constraints on two parameters by marginalizing over the two remaining
parameters. We obtain an upper limit of Gamma0.9 (68% confidence).
For a prior Gamma\in[0.1,0.4] and zs\in[0.6,1.4], we find
sigma_8=(0.50_{-0.16}^{+0.35})Omega_m^{-0.37} for flat cosmologies and
sigma_8=(0.51_{-0.16}^{+0.29})Omega_m^{-0.34}$ for open cosmologies (95%
confidence). If we take the currently popular LCDM model, we obtain a
one-dimensional confidence interval on sigma_8 for the 95.4% level,
0.62<\sigma_8<1.32 for zs\in[0.6,1.4]. Information on the redshift distribution
of galaxies is key to obtaining a correct cosmological constraint. An
independent constraint on Gamma from other observations is useful to tighten
the constraint.Comment: 12 pages, 12 figures, accepted for publication in Ap
Searching for dark matter halos in the Suprime-Cam 2 sq deg field
We report the first result of weak gravitational lensing survey on a 2.1 sq
deg Rc-band image taken with a wide field camera (Suprime-Cam) on the prime
focus of 8.2 m Subaru Telescope. The weak lensing mass reconstruction is
applied to the data to search for dark matter halos of cluster scale; M >=
10^14 solar mass. The reconstructed convergence field is divided by 1-sigma
noise to obtain the signal-to-noise ratio map (S/N-map) of the detection. Local
maxima and minima are searched on the S/N-map and the probability distribution
function (PDF) of the peaks are created to compare with model predictions. We
found excess over noise PDF created from the randomized realization on both
positive and negative sides. Negative peaks imply the presence of voids in the
dark matter distribution and this is the first report of the detection.
Positive peaks, on the other hand, represent the dark matter halos and the
number count of the halos on the 2.1 sq deg image is 4.9 +- 2.3 for S/N > 5
where the Gaussian smoothing radius of the convergence map is 1'. The result is
consistent with the prediction assuming the Press-Schechter mass function and
the NFW halo profile under the cluster normalized CDM cosmology. Although the
present statistics is not enough due to the limited field of view, this work
demonstrates that dark matter halo count via weak lensing is a promising way to
test the paradigm of structure formation and cosmological model.Comment: 4 pages, 3 figures, Accepted for publication in ApJ
A Search for Lyman alpha Emitters at Redshift 3.7
We present the results of a survey for emission-line objects based on optical
intermediate-band ( = 5736 \AA ~ and = 280
\AA) and broad-band (, , , and ) observations of the
Subaru/XMM-Newton Deep Field on the 8.2 m Subaru telescope with the Subaru
Prime Focus Camera, Suprime-Cam. All the data were obtained during the
guaranteed time observations of the Suprime-Cam instrument. The
intermediate-band image covered a sky area with 10\minpoint62 \times
12\minpoint40 \approx 132 arcmin in the Subaru/XMM-Newton Deep Field
(Ouchi et al.).
Using this image, we have found 23 emission-line sources whose observed
emission-line equivalent widths are greater than 250 \AA. Their optical
multicolor properties indicate that six emission-line sources are Ly
emitters at 3.7 (). They are either intense
starburst galaxies or active galactic nuclei like quasars at 3.7.
Two more emission-line sources may also be Ly emitters at
3.7 although their multicolor properties are marginal. Among the remaining 15
emission-line objects, eight objects appear strong emission-line galaxies at
lower redshift; e.g., [O {\sc ii}] 3727 emitters at ,
H at , or [O {\sc iii}]5007 emitters at . The remaining seven objects are unclassified because they are
too faint to be detected in broad-band images. We discuss observational
properties of these strong emission-line sources. In particular, our data allow
us to estimate the star formation density at for the first
time.Comment: Accepted for publication in AJ;14 pages, 26 figures (all figures are
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