40 research outputs found
A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). II. Physical Properties derived from the SED Fitting with Optical, Infrared, and Radio Data
We present physical properties of radio galaxies (RGs) with 1 mJy discovered by Subaru Hyper Supreme-Cam (HSC) and VLA Faint Images of
the Radio Sky at Twenty-Centimeters (FIRST) survey. For 1056 FIRST RGs at with HSC counterparts in about 100 deg, we compiled
multi-wavelength data of optical, near-infrared (IR), mid-IR, far-IR, and radio
(150 MHz). We derived their color excess (), stellar mass, star
formation rate (SFR), IR luminosity, the ratio of IR and radio luminosity
(), and radio spectral index () that are
derived from the SED fitting with CIGALE. We also estimated Eddington ratio
based on stellar mass and integration of the best-fit SEDs of AGN component. We
found that , SFR, and IR luminosity clearly depend on redshift
while stellar mass, , and do not significantly
depend on redshift. Since optically-faint () RGs that are
newly discovered by our RG survey tend to be high redshift, they tend to not
only have a large dust extinction and low stellar mass but also have high SFR
and AGN luminosity, high IR luminosity, and high Eddington ratio compared to
optically-bright ones. The physical properties of a fraction of RGs in our
sample seem to differ from a classical view of RGs with massive stellar mass,
low SFR, and low Eddington ratio, demonstrating that our RG survey with HSC and
FIRST provides us curious RGs among entire RG population.Comment: 30 pages, 20 figures, and 4 tables, accepted for publication in ApJS.
The catalog and SED template of radio galaxies will be accessible through an
online servic
Hyper-luminous Dust Obscured Galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE
We present the photometric properties of a sample of infrared (IR) bright
dust obscured galaxies (DOGs). Combining wide and deep optical images obtained
with the Hyper Suprime-Cam (HSC) on the Subaru Telescope and all-sky mid-IR
(MIR) images taken with Wide-Field Infrared Survey Explorer (WISE), we
discovered 48 DOGs with and , where
, , and [22] represent AB magnitude in the -band,
-band, and 22 m, respectively, in the GAMA 14hr field
( 9 deg). Among these objects, 31 ( 65 %) show power-law
spectral energy distributions (SEDs) in the near-IR (NIR) and MIR regime, while
the remainder show a NIR bump in their SEDs. Assuming that the redshift
distribution for our DOGs sample is Gaussian, with mean and sigma = 1.99
0.45, we calculated their total IR luminosity using an empirical relation
between 22 m luminosity and total IR luminosity. The average value of the
total IR luminosity is (3.5 1.1) L, which
classifies them as hyper-luminous infrared galaxies (HyLIRGs). We also derived
the total IR luminosity function (LF) and IR luminosity density (LD) for a
flux-limited subsample of 18 DOGs with 22 m flux greater than 3.0 mJy and
with -band magnitude brighter than 24 AB magnitude. The derived space
density for this subsample is log = -6.59 0.11 [Mpc]. The
IR LF for DOGs including data obtained from the literature is well fitted by a
double-power law. The derived lower limit for the IR LD for our sample is
3.8 10 [L Mpc] and
its contributions to the total IR LD, IR LD of all ultra-luminous infrared
galaxies (ULIRGs), and that of all DOGs are 3 %, 9 %, and 15 %,
respectively.Comment: 15 pages, 15 figures, and 3 tables, accepted for publication in PASJ
(Subaru special issue
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
Discovery of a Large Scale Clumpy Structure around the Lynx Supercluster at z~1.27
We report the discovery of a probable large scale structure composed of many
galaxy clumps around the known twin clusters at z=1.26 and z=1.27 in the Lynx
region. Our analysis is based on deep, panoramic, and multi-colour imaging
(26.4'x24.1') in VRi'z'-bands with the Suprime-Cam on the 8.2m Subaru
telescope. This unique, deep and wide-field imaging data-set allows us for the
first time to map out the galaxy distribution in the highest redshift
supercluster known. We apply a photometric redshift technique to extract
plausible cluster members at z~1.27 down to i'=26.15 (5sigma) corresponding to
\~M*+2.5 at this redshift. From the 2-D distribution of these photometrically
selected galaxies, we newly identify seven candidates of galaxy groups or
clusters where the surface density of red galaxies is significantly high
(>5sigma), in addition to the two known clusters. These candidates show clear
red colour-magnitude sequences consistent with a passive evolution model, which
suggests the existence of additional high density regions around the Lynx
superclusters.Comment: 6 pages, 5 figures, accepted for publication in MNRA
Down-Sizing in Galaxy Formation at z~1 in the Subaru/XMM-Newton Deep Survey (SXDS)
We use the deep wide-field optical imaging data of the Subaru/XMM-Newton Deep
Survey (SXDS) to discuss the luminosity (mass) dependent galaxy colours down to
z'=25.0 (5 x 10^9 h_{70}^{-2} Msun) for z~1 galaxies in colour-selected high
density regions. We find an apparent absence of galaxies on the red
colour-magnitude sequence below z'~24.2, corresponding to ~M*+2 (~10^{10} Msun)
with respect to passively evolving galaxies at z~1. Galaxies brighter than
M*-0.5 (8 x 10^{10} Msun), however, are predominantly red passively evolving
systems, with few blue star forming galaxies at these magnitudes.
This apparent age gradient, where massive galaxies are dominated by old
stellar populations while less massive galaxies have more extended star
formation histories, supports the `down-sizing' idea where the mass of galaxies
hosting star formation decreases as the Universe ages. Combined with the lack
of evolution in the shape of the stellar mass function for massive galaxies
since at least z~1, it appears that galaxy formation processes (both star
formation and mass assembly) should have occurred in an accelerated way in
massive systems in high density regions, while these processes should have been
slower in smaller systems. This result provides an interesting challenge for
modern CDM-based galaxy formation theories which predict later formation epochs
of massive systems, commonly referred to as ``bottom-up''.Comment: proof corrected version (MNRAS in press), 10 pages, 12 figures (of
which 3 are in jpg format