Yukiko Kamata

Hyper Suprime-Cam

Hyper Suprime-Cam (HSC) is an 870 Mega pixel prime focus camera for the 8.2 m Subaru telescope. The wide field corrector delivers sharp image of 0.25 arc-sec FWHM in r-band over the entire 1.5 degree (in diameter) field of view. The collimation of the camera with respect to the optical axis of the primary mirror is realized by hexapod actuators whose mechanical accuracy is few microns. As a result, we expect to have seeing limited image most of the time. Expected median seeing is 0.67 arc-sec FWHM in i-band. The sensor is a p-ch fully depleted CCD of 200 micron thickness (2048 x 4096 15 μm square pixel) and we employ 116 of them to pave the 50 cm focal plane. Minimum interval between exposures is roughly 30 seconds including reading out arrays, transferring data to the control computer and saving them to the hard drive. HSC uniquely features the combination of large primary mirror, wide field of view, sharp image and high sensitivity especially in red. This enables accurate shape measurement of faint galaxies which is critical for planned weak lensing survey to probe the nature of dark energy. The system is being assembled now and will see the first light in August 2012.

Early Phase Obserbations of Extermely Luminous Type Ia Supernova 2009dc

We present early phase observations in optical and near-infrared wavelengths for the extremely luminous Type Ia supernova (SN Ia) 2009dc. The decline rate of the light curve is ?m 15(B) = 0.65 ? 0.03, which is one of the slowest among SNe Ia. The peak V-band absolute magnitude is estimated to be MV = ?19.90 ? 0.15?mag if no host extinction is assumed. It reaches MV = ?20.19 ? 0.19?mag if we assume the host extinction of AV = 0.29?mag. SN 2009dc belongs to the most luminous class of SNe Ia, like SNe 2003fg and 2006gz. Our JHKs -band photometry shows that this SN is also one of the most luminous SNe Ia in near-infrared wavelengths. We estimate the ejected 56Ni mass of 1.2 ? 0.3 M ? for the no host extinction case (and of 1.6 ? 0.4 M ? for the host extinction of AV = 0.29?mag). The C II ?6580 absorption line remains visible until a week after the maximum brightness, in contrast to its early disappearance in SN 2006gz. The line velocity of Si II ?6355 is about 8000?km?s?1 around the maximum, being considerably slower than that of SN 2006gz. The velocity of the C II line is similar to or slightly less than that of the Si II line around the maximum. The presence of the carbon line suggests that the thick unburned C+O layer remains after the explosion. Spectropolarimetric observations by Tanaka et?al. indicate that the explosion is nearly spherical. These observational facts suggest that SN 2009dc is a super-Chandrasekhar mass SN Ia.

Current performance and on-going improvements of the 8.2 m Subaru Telescope

An overview of the current status of the 8.2m 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.

Adaptive Optics Spectroscopy of the [Fe II] Outflow from DG Tauri

We present results of the velocity-resolved spectroscopy of the [Fe ii] � 1.644 lm emission line along the optical jet emanating from DG Tau. The slit spectrum, obtained with the Subaru Telescope adaptive optics system at an angular resolution of 0>16, shows strong, entirely blueshifted emission on the southwest side of the star. A faint, redshifted counterfeature was also detected on the northeast side with emission within 0>7 of the star being occulted by the circumstellar disk. The blueshifted emission has two distinct radial velocity components. The low-velocity component (LVC) has a peak radial velocity of �� 100 km s � 1 with a FWHM line width of � 100 km s � 1 , and it peaks at 0>2–0>5 from the star. The high-velocity component (HVC) peaks at 0>6–0>8 away from the star, showing a peak radial velocity of �� 220 km s � 1 with a line width of � 50 km s � 1 . These characteristics are remarkably similar to the [Fe ii] outflow from L1551 IRS 5, although the linear scales of the HVCs and LVCs are different for the two objects. We conclude, as an analogy to the case of L1551 IRS 5, that the HVC is a well-collimated jet launched from the region close to the star and that the LVC is a disk wind with a wide opening angle. Detailed comparison of emission parameters between the two sources, however, suggests that part of the LVC emission from DG Tau arises from the gas entrained and accelerated by the HVC, if we assume continuous steady state outflows. The presence of two distinct emission components clearly separated in space and velocity may favor theoretical models with two outflows: one is the LVC magnetohydrodynamically driven near the inner edge of an accretion disk, and the other is the HVC driven by the reconnection of dipolar stellar magnetic fields anchored to the disk. Subject headings: ISM: Herbig-Haro objects — ISM: individual (DG Tauri, HH 158) — ISM: jets and outflows — stars: formation — stars: pre–main-sequence — techniques: high angular resolution

HyperSuprime: project overview

HyperSuprime is a next generation wide field camera proposed for the 8.3 m Subaru Telescope. The targeted field of view is larger than 1.5 deg in diameter, which will give us roughly 10 times increase of the survey speed compared with the existing prime focus camera (Suprime-Cam). An overview of the current status of the feasibility study is given.

Spatially Resolved 3 Micron Spectroscopy of IRAS 22272+5435: Formation and Evolution of Aliphatic Hydrocarbon Dust in Proto-Planetary Nebulae*

We present medium-resolution 3 lm spectroscopy of the carbon-rich proto–planetary nebula IRAS 22272+5435. Spectroscopy with the Subaru Telescope adaptive optics system revealed a spatial variation of hydrocarbon molecules and dust surrounding the star. The rovibrational bands of acetylene (C2H2) and hydrogen cyanide (HCN) at 3.0 lm are evident in the central star spectra. The molecules are concentrated in the compact region near the center. The 3.3 and 3.4 lm emission of aromatic and aliphatic hydrocarbons is detected at 600–1300 AU from the central star. The separation of spatial distribution between gas and dust suggests that the small hydrocarbon molecules are indeed the source of solid material and that the gas left over from the grain formation is being observed near the central star. The intensity of aliphatic hydrocarbon emission relative to the aromatic hydrocarbon emission decreases with distance from the central star. The spectral variation is well matched to that of a laboratory analog thermally annealed with different temperatures. We suggest that either the thermal process after the formation of a grain or the variation in the temperature in the dust-forming region over time determines the chemical composition of the hydrocarbon dust around the proto–planetary nebula. Subject headings: circumstellar matter — dust, extinction — infrared: ISM — ISM: evolution — stars: AGB and post-AGB — stars: individual (IRAS 22272+5435)

Wide-field one-shot optical polarimeter: HOWPol

For prompt optical polarimetry of gamma-ray burst (GRB) afterglow, we require wide-field imaging polarimeter which can produce both Stokes Q and U parameters from only a single exposure, as well as quickly-moving telescope and enclosure system. HOWPol is an optical imaging polarimeter which provides four linearly polarized images at position angles of 0°, 45°, 90° and 135°, i.e., Stokes I, Q, U, simultaneously. The key device is the wedged double Wollaston prism described by Oliva (1997)1 and Pernechele et al. (2003).2 The images are focused on two 2k×4k fully depleted CCDs. We report the design and development of the optical devices of HOWPol, which will be mounted to the 1.5-m Kanata telescope at Hiroshima University and stand by the GRB alert.

Adaptive optics system for Cassegrain focus of Subaru 8.2-m telescope

The adaptive optics system for Subaru 8.2m telescope of the National Astronomical Observatory Japan has been developed for the Cassegrain ear-IR instruments, CIAO and IRCS. The system consists of a wavefront curvature sensor with 36 subaperture photon-counting avalanche photodiode modules and a bimorph deformable mirror with 36 electrodes. The expected Strehl ratio at K band exceeds 0.4 for objects that are located close enough to a bright guide star as faint as R equals 16 mag at the median seeing of 0.45 arcsec at Mauna Kea. The system will be in operation in 1999 as a natural guide star system, and will eventually be upgraded to a laser guide star system in cooperating an IR wavefront tilt sensor to provide nearly full sky. The construction of this common use system to Subaru telescope is now underway in our laboratory in Tokyo. Prior to starting the fabrication of this common use system, a full size prototype system was constructed and tested with the 1.6 m IR telescope at our observatory in Tokyo. This system has the identical optical design, deformable mirror, loop control computer to those for the Subaru system, while the wavefront sensing detectors were less-sensitive analog APDs. We succeeded in getting closed loop images of stars in K band with diffraction limited core. The Strehl ratio was around 0.5 and the factor of improvement was about 20 at K-band under the average seeing of 2 arcsec during the observation. The loop sped of the system was 2 K corrections per second.

Diffraction-Limited 3 μm Spectroscopy of IRAS 04296+3429 and IRAS 05341+0852: Spatial Extent of Hydrocarbon Dust Emission and Dust Evolutionary Sequence*

We present 3 μm spectroscopy of the carbon-rich protoplanetary nebulae IRAS 04296+3429 and IRAS 05341+0852, conducted with the adaptive optics system at the Subaru Telescope. We utilize the nearly diffraction-limited spectroscopy to probe the spatial extent of the hydrocarbon dust emitting zone. We find a hydrocarbon emission core extending up to 100-160 mas from the center of IRAS 04296+3429, corresponding to a physical diameter of 400-640 AU, assuming a distance of 4 kpc. However, we find that IRAS 05341+0852 is not spatially resolved with this instrumentation. The physical extent of these protoplanetary nebulae, along with the reanalyzed data of IRAS 22272+5435 published previously, suggests a correlation between the physical extent of the hydrocarbon dust emission and the spectral evolution of the aliphatic to aromatic features in these post-AGB stars. These measurements represent the first direct test of the proposed chemical synthesis route of carbonaceous dust in the circumstellar environment of evolved stars.

Carbon Isotope Ratio in 12CO/13CO toward Local Molecular Clouds with Near-Infrared High-Resolution Spectroscopy of Vibrational Transition Bands

We report the carbon monoxide isotope ratio in local molecular clouds toward LkHα 101, AFGL 490, and Mon R2 IRS 3. The vibrational transition bands of 12CO ν = 2 ← 0 and 13CO ν = 1 ← 0 were observed with high-resolution near-infrared spectroscopy (R = 23,000) to measure the 12CO/13CO ratio. The isotopic ratios are 12CO/13CO = 137 ± 9 (LkHα 101), 86 ± 49 (AFGL 490), and 158 (Mon R2 IRS 3), which are 1.5-2.8 times higher than the local interstellar medium value of 12CO/13CO = 57 ± 5 from millimeter C18O emission observations. This is not easily explained by saturation of the 13CO absorption. It is also questionable whether the selective photodestruction of 13CO can account for the difference between the Galactic trend and the present observation, because the molecular clouds are with high visible extinction (AV = 10-70 mag), well shielded from destructive FUV radiation. The molecular gas associated with AFGL 490 and Mon R2 IRS 3 consists of multiple temperature components lying in the lines of sight. In the cool component (Tex < 100 K), the excitation temperature of 12CO is twice that of 13CO. We attribute the temperature discrepancy to the photon-trapping effect, which makes the radiative cooling of the main isotopomer less effective.