155 research outputs found
Rotation-Resolved Spectroscopy of a Very Young Asteroid, (1270) Datura
(1270) Datura is the largest member of a very young asteroid cluster that was
thought to be broken-up 0.45 Myr ago. The light-curve and the rotation-resolved
reflectance spectra (0.6 um - 1.0 um) were observed in order to find "fresh"
surface. Our data show no significant spectral variation along the rotation
phase. The depth of the 0.95 um absorption band, which indicates the degree of
space weathering, was similar to that of an old S-type asteroid. This suggests
that the reflectance spectrum in this wavelength range changes rapidly and
saturates the depth of the 0.95 um absorption in less than 0.45 Myr in the main
belt environment.Comment: 8 pages, 3 figures, accepted for publication in the ApJ Lette
Thermal Infrared and Optical Photometry of Asteroidal Comet C/2002 CE
C/2002 CE is an object in a retrograde elliptical orbit with Tisserand
parameter indicating a likely origin in the Oort Cloud. It appears to
be a rather inactive comet since no coma and only a very weak tail was detected
during the past perihelion passage. We present multi-color optical photometry,
lightcurve and thermal mid-IR observations of the asteroidal comet.
\textcolor{blue}{ With the photometric analysis in , the surface color is
found to be redder than asteroids, corresponding to cometary nuclei and
TNOs/Centaurs. The time-resolved differential photometry supports a rotation
period of 8.190.05 h. The effective diameter and the geometric albedo are
17.90.9 km and 0.030.01, respectively, indicating a very dark
reflectance of the surface. The dark and redder surface color of C/2002
CE may be attribute to devolatilized material by surface aging suffered
from the irradiation by cosmic rays or from impact by dust particles in the
Oort Cloud. Alternatively, C/2002 CE was formed of very dark refractory
material originally like a rocky planetesimal. In both cases, this object lacks
ices (on the surface at least). The dynamical and known physical
characteristics of C/2002 CE are best compatible with those of the
Damocloids population in the Solar System, that appear to be exhaust cometary
nucleus in Halley-type orbits. The study of physical properties of rocky Oort
cloud objects may give us a key for the formation of the Oort cloud and the
solar system.Comment: 9 pages, 4 figures accepted to Icaru
Design and performance of a F/#-conversion microlens for Prime Focus Spectrograph at Subaru Telescope
The PFS is a multi-object spectrograph fed by 2394 fibers at the prime focus
of Subaru telescope. Since the F/# at the prime focus is too fast for the
spectrograph, we designed a small concave-plano negative lens to be attached to
the tip of each fiber that converts the telescope beam (F/2.2) to F/2.8. We
optimized the lens to maximize the number of rays that can be confined inside
F/2.8 while maintaining a 1.28 magnification. The microlenses are manufactured
by glass molding, and an ultra-broadband AR coating (<1.5% for lambda=0.38-1.26
um) will be applied to the front surface.Comment: 7 pages, 8 figures, SPIE201
The Subaru FMOS Galaxy Redshift Survey (FastSound). III. The mass-metallicity relation and the fundamental metallicity relation at
We present the results from a large near-infrared spectroscopic survey with
Subaru/FMOS (\textit{FastSound}) consisting of 4,000 galaxies at
with significant H detection. We measure the gas-phase
metallicity from the [N~{\sc ii}]6583/H emission line ratio of
the composite spectra in various stellar mass and star-formation rate bins. The
resulting mass-metallicity relation generally agrees with previous studies
obtained in a similar redshift range to that of our sample. No clear dependence
of the mass-metallicity relation with star-formation rate is found. Our result
at is roughly in agreement with the fundamental metallicity relation
at with fiber aperture corrected star-formation rate. We detect
significant [S~{\sc ii}]6716,6731 emission lines from the
composite spectra. The electron density estimated from the [S~{\sc
ii}]6716,6731 line ratio ranges from 10 -- 500 cm, which
generally agrees with that of local galaxies. On the other hand, the
distribution of our sample on [N~{\sc ii}]6583/H vs. [S~{\sc
ii}]6716,6731/H is different from that found locally.
We estimate the nitrogen-to-oxygen abundance ratio (N/O) from the N2S2 index,
and find that the N/O in galaxies at is significantly higher than
the local values at a fixed metallicity and stellar mass. The metallicity at
recalculated with this N/O enhancement taken into account decreases
by 0.1 -- 0.2 dex. The resulting metallicity is lower than the local
fundamental metallicity relation.Comment: 14 pages, 10 figures, 2 tables, accepted for publication in PAS
The Subaru FMOS Galaxy Redshift Survey (FastSound). II. The Emission Line Catalog and Properties of Emission Line Galaxies
We present basic properties of 3,300 emission line galaxies detected by
the FastSound survey, which are mostly H emitters at 1.2-1.5
in the total area of about 20 deg, with the H flux sensitivity
limit of at 4.5 sigma. This
paper presents the catalogs of the FastSound emission lines and galaxies, which
will be open to the public in the near future. We also present basic properties
of typical FastSound H emitters, which have H luminosities of
- erg/s, SFRs of 20--500 /yr, and stellar masses
of -- . The 3D distribution maps for the four
fields of CFHTLS W1--4 are presented, clearly showing large scale clustering of
galaxies at the scale of 100--600 comoving Mpc. Based on 1,105 galaxies
with detections of multiple emission lines, we estimate that contamination of
non-H lines is about 4% in the single-line emission galaxies, which are
mostly [OIII]5007. This contamination fraction is also confirmed by
the stacked spectrum of all the FastSound spectra, in which H,
[NII]6548,6583, [SII]6717, 6731, and
[OI]6300,6364 are seen.Comment: 17 pages, 15 figures, accepted for publication in PAS
Metrology Camera System of Prime Focus Spectrograph for Subaru Telescope
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber
spectrograph designed for the prime focus of the 8.2m Subaru telescope. PFS
will cover a 1.3 degree diameter field with 2394 fibers to complement the
imaging capabilities of Hyper SuprimeCam. To retain high throughput, the final
positioning accuracy between the fibers and observing targets of PFS is
required to be less than 10um. The metrology camera system (MCS) serves as the
optical encoder of the fiber motors for the configuring of fibers. MCS provides
the fiber positions within a 5um error over the 45 cm focal plane. The
information from MCS will be fed into the fiber positioner control system for
the closed loop control. MCS will be located at the Cassegrain focus of Subaru
telescope in order to to cover the whole focal plane with one 50M pixel Canon
CMOS camera. It is a 380mm Schmidt type telescope which generates a uniform
spot size with a 10 micron FWHM across the field for reasonable sampling of
PSF. Carbon fiber tubes are used to provide a stable structure over the
operating conditions without focus adjustments. The CMOS sensor can be read in
0.8s to reduce the overhead for the fiber configuration. The positions of all
fibers can be obtained within 0.5s after the readout of the frame. This enables
the overall fiber configuration to be less than 2 minutes. MCS will be
installed inside a standard Subaru Cassgrain Box. All components that generate
heat are located inside a glycol cooled cabinet to reduce the possible image
motion due to heat. The optics and camera for MCS have been delivered and
tested. The mechanical parts and supporting structure are ready as of spring
2016. The integration of MCS will start in the summer of 2016.Comment: 11 pages, 15 figures. SPIE proceeding. arXiv admin note: text overlap
with arXiv:1408.287
Visible camera cryostat design and performance for the SuMIRe Prime Focus Spectrograph (PFS)
We describe the design and performance of the SuMIRe Prime Focus Spectrograph
(PFS) visible camera cryostats. SuMIRe PFS is a massively multi-plexed
ground-based spectrograph consisting of four identical spectrograph modules,
each receiving roughly 600 fibers from a 2394 fiber robotic positioner at the
prime focus. Each spectrograph module has three channels covering wavelength
ranges 380~nm -- 640~nm, 640~nm -- 955~nm, and 955~nm -- 1.26~um, with the
dispersed light being imaged in each channel by a f/1.07 vacuum Schmidt camera.
The cameras are very large, having a clear aperture of 300~mm at the entrance
window, and a mass of 280~kg. In this paper we describe the design of the
visible camera cryostats and discuss various aspects of cryostat performance
Conceptual Design of the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) for the Subaru Telescope
Recent developments in high-contrast imaging techniques now make possible
both imaging and spectroscopy of planets around nearby stars. We present the
conceptual design of the Coronagraphic High Angular Resolution Imaging
Spectrograph (CHARIS), a lenslet-based, cryogenic integral field spectrograph
(IFS) for imaging exoplanets on the Subaru telescope. The IFS will provide
spectral information for 140x140 spatial elements over a 1.75 arcsecs x 1.75
arcsecs field of view (FOV). CHARIS will operate in the near infrared (lambda =
0.9 - 2.5 microns) and provide a spectral resolution of R = 14, 33, and 65 in
three separate observing modes. Taking advantage of the adaptive optics systems
and advanced coronagraphs (AO188 and SCExAO) on the Subaru telescope, CHARIS
will provide sufficient contrast to obtain spectra of young self-luminous
Jupiter-mass exoplanets. CHARIS is in the early design phases and is projected
to have first light by the end of 2015. We report here on the current
conceptual design of CHARIS and the design challenges
NIR Spectroscopy of Star-Forming Galaxies at z~1.4 with Subaru/FMOS: The Mass-Metallicity Relation
We present near-infrared spectroscopic observations of star-forming galaxies
at z~1.4 with FMOS on the Subaru Telescope. We observed K-band selected
galaxies in the SXDS/UDS fields with K10^{9.5}
Msun, and expected F(Halpha)>10^{-16} erg s^{-1} cm^{-2}. 71 objects in the
sample have significant detections of Halpha. For these objects, excluding
possible AGNs identified from the BPT diagram, gas-phase metallicities are
obtained from [NII]/Halpha line ratio. The sample is split into three stellar
mass bins, and the spectra are stacked in each stellar mass bin. The
mass-metallicity relation obtained at z~1.4 is located between those at z~0.8
and z~2.2. We constrain an intrinsic scatter to be ~0.1 dex or larger in the
mass-metallicity relation at z~1.4; the scatter may be larger at higher
redshifts. We found trends that the deviation from the mass-metallicity
relation depends on the SFR and the half light radius: Galaxies with higher SFR
and larger half light radii show lower metallicities at a given stellar mass.
One possible scenario for the trends is the infall of pristine gas accreted
from IGM or through merger events. Our data points show larger scatter than the
fundamental metallicity relation (FMR) at z~0.1 and the average metallicities
slightly deviate from the FMR. The compilation of the mass-metallicity
relations at z~3 to z~0.1 shows that they evolve smoothly from z~3 to z~0
without changing the shape so much except for the massive part at z~0.Comment: 20 pages, 18 figures, accepted for publication in PAS
- …