39 research outputs found
MOIRCS Deep Survey. VII: NIR Morphologies of Star-forming Galaxies at Redshift z~1
We investigate rest-frame near-infrared (NIR) morphologies of a sample of 139
galaxies with M_{s} >= 1 x 10^{10} M_{sun} at z=0.8-1.2 in the GOODS-North
field using our deep NIR imaging data (MOIRCS Deep Survey, MODS). We focus on
Luminous Infrared Galaxies (LIRGs), which dominate high star formation rate
(SFR) density at z~1, in the sample identified by cross-correlating with the
Spitzer/MIPS 24um source catalog. We perform two-dimensional light profile
fitting of the z~1 galaxies in the Ks-band (rest-frame J-band) with a single
component Sersic model. We find that at z~1, ~90% of LIRGs have low Sersic
indices (n<2.5, similar to disk-like galaxies) in the Ks-band, and those
disk-like LIRGs consist of ~60% of the whole disk-like sample above M_{s} >= 3
x 10^{10} M_{sun}. The z~1 disk-like LIRGs are comparable or ~20% small at a
maximum in size compared to local disk-like galaxies in the same stellar mass
range. If we examine rest-frame UV-optical morphologies using the HST/ACS
images, the rest-frame B-band sizes of the z~1 disk-like galaxies are
comparable to those of the local disk-like galaxies as reported by previous
studies on size evolution of disk-like galaxies in the rest-frame optical band.
Measuring color gradients (galaxy sizes as a function of wavelength) of the z~1
and local disk-like galaxies, we find that the z~1 disk-like galaxies have 3-5
times steeper color gradient than the local ones. Our results indicate that (i)
more than a half of relatively massive disk-like galaxies at z~1 are in violent
star formation epochs observed as LIRGs, and also (ii) most of those LIRGs are
constructing their fundamental disk structure vigorously. The high SFR density
in the universe at z~1 may be dominated by such star formation in disk region
in massive galaxies.Comment: 16 pages, 15 figures, accepted for publication in PASJ. Catalog data
will be available at http://astr.tohoku.ac.jp/MODS/wiki/index.php soo
Assembly of Massive Galaxies in a High-z Protocluster
We present the results of wide-field deep JHK imaging of the SSA22 field
using MOIRCS instrument equipped with Subaru telescope. The observed field is
112 arcmin^2 in area, which covers the z=3.1 protocluster characterized by the
overdensities of Ly Alpha emitters (LAEs) and Ly Alpha Blobs (LABs). The 5
sigma limiting magnitude is K_{AB} = 24.3. We extract the potential
protocluster members from the K-selected sample by using the multi-band
photometric-redshift selection as well as the simple color cut for distant red
galaxies (DRGs; J-K_{AB}>1.4). The surface number density of DRGs in our
observed fields shows clear excess compared with those in the blank fields, and
the location of the densest area whose projected overdensity is twice the
average coincides with the large-scale density peak of LAEs. We also found that
K-band counterparts with z_{phot} = 3.1 are detected for 75% (15/20) of the
LABs within their Ly Alpha halo, and the 40 % (8/20) of LABs have multiple
components, which gives a direct evidence of the hierarchical multiple merging
in galaxy formation. The stellar mass ofLABs correlates with their luminosity,
isophotal area, and the Ly Alpha velocity widths, implying that the physical
scale and the dynamical motion of Ly Alpha emission are closely related to
their previous star-formation activities. Highly dust-obscured galaxies such as
hyper extremely red objects (HEROs; J-K_{AB}>2.1) and plausible K-band
counterparts of submillimeter sources are also populated in the high density
region.Comment: 21pages, accepted for publication in Astrophysical Journa
High-Resolution Near-Infrared Imaging of the Powerful Radio Galaxy 3C 324 at z = 1.21 with the Subaru Telescope
We have obtained high-resolution K'-band images of the powerful z=1.206 radio
galaxy 3C 324 with the Subaru telescope under seeing conditions of 0.3--0.4
arcsec. We clearly resolved the galaxy and directly compared it to the optical
images obtained with the Hubble Space Telescope. The host galaxy of 3C 324 is
revealed to be a moderately luminous elliptical galaxy with a smooth light
profile. The effective radius of the galaxy, as determined by profile fitting,
is 1.3+-0.1 arcsec (1.2 kpc), which is significantly smaller than the value of
2.2 arcsec, published in Best et al. (1998, MNRAS, 292, 758). The peak of the
K'-band light coincides with the position of the radio core, which implies that
the powerful AGN lies at the nucleus of the host galaxy. The peak also
coincides with the gap in the optical knotty structures which may be a dust
lane hiding the UV-optical emission of the AGN from our line of sight; it is
very likely that we are seeing the obscuring structure almost edge-on. We
clearly detected the `aligned component' in the K'-band image by subtracting a
model elliptical galaxy from the observed image. The red R_F702W-K color of the
outer region of the galaxy avoiding the aligned component indicates that the
near infrared light of the host galaxy is dominated by an old stellar
population.Comment: 21 pages (10 figures), accepted for publication in PAS
MOIRCS Deep Survey. I: DRG Number Counts
We use very deep near-infrared imaging data taken with Multi-Object InfraRed
Camera and Spectrograph (MOIRCS) on the Subaru Telescope to investigate the
number counts of Distant Red Galaxies (DRGs). We have observed a 4x7 arcmin^2
field in the Great Observatories Origins Deep Survey North (GOODS-N), and our
data reach J=24.6 and K=23.2 (5sigma, Vega magnitude). The surface density of
DRGs selected by J-K>2.3 is 2.35+-0.31 arcmin^-2 at K<22 and 3.54+-0.38
arcmin^-2 at K<23, respectively. These values are consistent with those in the
GOODS-South and FIRES. Our deep and wide data suggest that the number counts of
DRGs turn over at K~22, and the surface density of the faint DRGs with K>22 is
smaller than that expected from the number counts at the brighter magnitude.
The result indicates that while there are many bright galaxies at 2<z<4 with
the relatively old stellar population and/or heavy dust extinction, the number
of the faint galaxies with the similar red color is relatively small. Different
behaviors of the number counts of the DRGs and bluer galaxies with 2<z_phot<4
at K>22 suggest that the mass-dependent color distribution, where most of
low-mass galaxies are blue while more massive galaxies tend to have redder
colors, had already been established at that epoch.Comment: 6 pages, 4 figures, accepted for publication in PAS
Subaru/MOIRCS Near-Infrared Imaging in the Proto-Cluster Region at z=3.1
We present the results of deep near-infrared imaging observations of the
z=3.1 proto-cluster region in the SSA22a field taken by MOIRCS mounted on the
Subaru Telescope. We observed a 21.7 arcmin^2 field to the depths of J=24.5,
H=24.3, and K=23.9 (5 sigma). We examine the distribution of the K-selected
galaxies at z~3 by using the simple color cut for distant red galaxies (DRGs)
as well as the photometric-redshift selection technique. The marginal density
excess of DRGs and the photo-z selected objects are found around the two most
luminous Ly alpha blobs (LABs). We investigate the correlation between the
K-selected objects and the LABs, and find that several galaxies with stellar
mass M_* = 10^9-10^11 M_solar exist in vicinity of LABs, especially around the
two most luminous ones. We also find that 7 of the 8 LABs in the field have
plausible K_s-band counterparts and the sum of the stellar mass possibly
associated with LABs correlates with the luminosity and surface brightness of
them, which implies that the origin of Ly alpha emission may be closely
correlated with their stellar mass or their previous star formation phenomena.Comment: 15 pages, 9 figures, accepted for publication in PASJ Vol.60, No.
Current Performance and On-Going Improvements of the 8.2 m Subaru Telescope
An overview of the current status of the 8.2 m Subaru Telescope constructed
and operated at Mauna Kea, Hawaii, by the National Astronomical Observatory of
Japan is presented. The basic design concept and the verified performance of
the telescope system are described. Also given are the status of the instrument
package offered to the astronomical community, the status of operation, and
some of the future plans. The status of the telescope reported in a number of
SPIE papers as of the summer of 2002 are incorporated with some updates
included as of 2004 February. However, readers are encouraged to check the most
updated status of the telescope through the home page,
http://subarutelescope.org/index.html, and/or the direct contact with the
observatory staff.Comment: 18 pages (17 pages in published version), 29 figures (GIF format),
This is the version before the galley proo