37 research outputs found
Number Density of Bright Lyman-Break Galaxies at z~6 in the Subaru Deep Field
We report on the bright Lyman-break galaxies (LBGs) selected in a 767
arcmin^2 area of the Subaru Deep Field. The selection is made in the i-zR vs
zB-zR plane, where zB and zR are new bandpasses with a central wavelength of
8842A and 9841A, respectively. This set of bandpasses enables us to separate
well z~6 LBGs from foreground galaxies and Galactic cool stars. We detect 12
LBG candidates down to zR=25.4, and calculate the normalization of the
rest-frame far-ultraviolet (FUV: 1400A) luminosity function at MFUV = -21.6 to
be \phi(-21.6) = (2.6+/-0.7) x 10^{-5} mag^{-1} Mpc^{-3}. This must be the most
reliable measurement ever obtained of the number density of bright z~6 LBGs,
because it is more robust against both contamination and cosmic variance than
previous values. The FUV luminosity density contributed from LBGs brighter than
MFUV = -21.3 is (2.8+/-0.8) x 10^{24} ergs/s/Hz/Mpc^3, which is equivalent to a
star formation rate density of (3.5+/-1.0) x 10^{-4} Msun/yr/Mpc^3. Combining
our measurement with those at z<6 in the literature, we find that the FUV
luminosity density of bright galaxies increases by an order of magnitude from
z~6 to z~3 and then drops by 10^3 from z~3 to the present epoch, while the
evolution of the total luminosity density is much milder. The evolutionary
behavior of bright LBGs resembles that of luminous dusty star-forming galaxies
and bright QSOs. The redshift of z~3 appears to be a remarkable era in the
cosmic history when massive galaxies were being intensively formed.Comment: 12 pages, accepted for PASJ, a high resolution version is available
at http://hikari.astron.s.u-tokyo.ac.jp/~shima/z6LBGs
Subaru Deep Survey VI. A Census of Lyman Break Galaxies at z=4 and 5 in the Subaru Deep Fields: Clustering Properties
We investigate the clustering properties of 2,600 Lyman Break Galaxies (LBGs)
at z=3.5-5.2 in two large blank fields, the Subaru Deep Field and the
Subaru/XMM Deep Field (600arcmin^2 each). The angular correlation functions of
these LBGs show a clear clustering at both z~4 and 5. The correlation lengths
are r_0= 4.1^{+0.2}_{-0.2} and 5.9^{+1.3}_{-1.7} h_{100}^{-1} Mpc (r_0=
5.1^{+1.0}_{-1.1} and 5.9^{+1.3}_{-1.7} h_{100}^{-1} Mpc) for all the detected
LBGs (for L>L* LBGs) at z~4 and 5, respectively. These correlation lengths
correspond to galaxy-dark matter biases of b_g= 2.9^{+0.1}_{-0.1} and
4.6^{+0.9}_{-1.2} (b_g=3.5^{+0.6}_{-0.7} and 4.6^{+0.9}_{-1.2}), for all the
detected LBGs (for L>L^* LBGs) at z~4 and 5, respectively. These results,
combined with estimates for z~3 LBGs in the literature, show that the
correlation length of L>L^* LBGs is almost constant, ~5 h_{100}^{-1} Mpc, over
z~3-5, while the bias monotonically increases with redshift at z>3. We also
find that for LBGs at z~4 the clustering amplitude increases with UV-continuum
luminosity and with the amount of dust extinction. We estimate the mass of dark
halos hosting various kinds of high-z galaxies including LBGs with the analytic
model given by Sheth & Tormen (1999). We find that the typical mass of dark
halos hosting L>L^* LBGs is about 1x10^{12} h_{70}^{-1}Msol over z~3-5, which
is comparable to that of the Milky Way Galaxy. A single dark halo with ~10^{12}
h_{70}^{-1} Msol is found to host 0.1-0.3 LBG on average but host about four
K-band selected galaxies.Comment: 33 pages, 12 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_VI.pdf
(PDF) (The abstract was reduced by the revision.
The Subaru/XMM-Newton Deep Survey (SXDS). IV. Evolution of Lya Emitters from z=3.1 to 5.7 in the 1 deg^2 Field: Luminosity Functions and AGN
We present luminosity functions (LFs) and various properties of Lya emitters
(LAEs) at z=3.1, 3.7, and 5.7, in a 1 deg^2 sky of the Subaru/XMM-Newton Deep
Survey (SXDS) Field. We obtain a photometric sample of 858 LAE candidates based
on deep Subaru/Suprime-Cam imaging data, and a spectroscopic sample of 84
confirmed LAEs from Subaru/FOCAS and VLT/VIMOS spectroscopy in a survey volume
of ~10^6 Mpc^3 with a limiting Lya luminosity of ~3x10^42 erg/s. We derive the
LFs of Lya and UV-continuum (~1500 \AA) for each redshift, taking into account
the statistical error and the field-to-field variation. We find that the
apparent Lya LF shows no significant evolution between z=3.1 and 5.7 within
factors of 1.8 and 2.7 in L* and phi*, respectively. On the other hand, the UV
LF of LAEs increases from z=3.1 to 5.7, indicating that galaxies with Lya
emission are more common at earlier epochs. We identify six LAEs with AGN
activities from our spectra combined with VLA, Spitzer, and XMM-Newton data.
Among the photometrically selected LAEs at z=3.1 and 3.7, only ~1 % show AGN
activities, while the brightest LAEs with logL(Lya) >~ 43.4-43.6 erg/s appear
to always host AGNs. Our LAEs are bluer in UV-continuum color than dropout
galaxies, suggesting lower extinction and/or younger stellar populations. Our
stacking analyses provide upper limits to the radio luminosity and the
f(HeII)/f(Lya) line fraction, and constrain the hidden star formation
(+low-luminosity AGN) and the primordial population in LAEs.Comment: 75 pages, 27 figures; ApJS in press. High resolution version at
http://www.ociw.edu/~ouchi/work/astroph/sxds_LAEs/ouchi_SXDSLAE_ApJS.pd
Narrow band imaging in [OIII] and Halpha to search for ICPNe in the Virgo cluster
We have identified intracluster planetary nebulae in a Virgo cluster core
field by imaging with the Subaru Suprime-Cam through two narrow band filters
centered at the redshifted wavelengths of the [OIII] \AA and the
H \AA lines; broad-band images in V and R were
acquired to check for emission in the adjacent continuum. Emission line objects
in Virgo are then selected from the two-color diagram ([OIII] -- Halpha) vs.
([OIII] -- (V+R)), which is calibrated using PNe in M84 (Jacoby et al. 1990).
Using both [OIII] and Halpha allows us to distinguish bona-fide planetary
nebulae from high redshift emission-line galaxies at the bright end of the
[OIII] luminosity function. Spectroscopic observations of a subsample of these
objects were made at the TNG and at the VLT, in a region around M84 and in an
intracluster field respectively. The observations confirm the efficiency of the
combined [OIII]+H imaging to identify true PNe. We also obtained the
first spectrum of an intracluster PN which shows the [OIII] doublet with S/N >
10 and its Halpha emission. From the results based on the spectroscopic
follow-up, we derive a lower limit to the fraction of the Virgo cluster light
contributed by the intracluster stars at the surveyed position in the cluster
core: it amounts to 10%.Comment: 32 pages,11 figures, in press on AJ, February 200