片坐 宏一

SPICA is a cooled, single large-mirror space-telescope, which is under discussion as an succsesor of the ASTRO-F mission. One of the most ambitious challenges of the SPICA mission is the direct observations of exoplanets with a coronagraph instrument. We report cryogenic infrared optics to realize high quality wavefronts for the SPICA coronagraph. The SPICA satellite will be launched by an H-IIA rocket to Sun-Earth L2 Halo orbit early in the 2010s. The SPICA telescope is a Ritchey-Chretien optics with 3.5m diameter primary mirror, and cooled down to 4.5 K in orbit by radiation cooling and mechanical cryo-coolers. Main working wavelengths are 5-200 micron. Advantages of the SPICA coronagraph are the infrared wavelenths where the contrast between planets and central stars are smaller than the optical wavelengths, and that the cooled space telescope consists of monolithic mirrors. Development of light-weight cooled telescope is one of the most important tasks to realize SPICA. At the present, sintered SiC and carbon fiber reinforced SiC (C/SiC) composite are candidate materials for the mirrors, truss, and optical bench. For these materials, estimations and improvements of basic property and surface roughness in cryogenic temperatures have been carried out. Deformation of trial product mirrors by cooling is also examined. We are developing cryogenic deformable mirrors (DMs) because wave front accuracy of the SPICA telescope is 0.35 micron RMS, which is not enough for our coronagraphic instrument. For MEMS (Micro Electro Mechanical System) DM and some others, measurements of thermal deformation by cooling, electrical response, and heat generation are undergoing. Developments of a tip-tilt system for cryogenic usage started to cancel vibration caused by the cryo-coolers and other components and to realize a diffraction limit resolution. The first result of our binary mask coronagraph experiment is also shown. © 2006 International Astronomical Union.

As of early ∼2010's, the Japanese SPace Infrared telescope for Cosmology and Astrophysics (SPICA) space observatory will be launched. This actively cooled, cryogenic (4.5K), 3.5m telescope will operate in the mid and far infrared spectral regions. With its very high sensitivity, one of SPICA's aims will be the direct detection and characterization of extra-solar outer planets of nearby stars. The goal contrast ranges from 10 to 10 up to an angular separation of ∼5 arcsec. The relatively low angular resolution at MIR (5 to 20 μm) requires an efficient and robust coronagraphic mode working at cryogenic temperatures. In this presentation we describe several envisaged preliminary designs and assess their performance against the science goals and host telescope specifications. These are compared against numerical simulations and instrumental environment considerations, such as the need for an actively corrected wavefront. © 2006 International Astronomical Union. 5 6

We present configurations of shaped pupil coronagraphs optimized for a realistic telescope to directly detect extrasolar giant planets in the mid-IR wavelengths. This study is linked to the development of the coronagraphic instrument aboard SPICA (SPace Infrared telescope for Cosmology and Astrophysics). We made a systematic assessment of the performance of the "checkerboard" and "concentric ring" masks, introducing a large central obstruction (C.O.) due to a secondary mirror and its related support spiders. With a small secondary mirror, we also propose a modification to the original symmetrical checkerboard apodization, which enables us to achieve a 10 contrast level at 4.0 λ/D. The transmission through the optimal binary masks exhibits abrupt increases and plateaus as the inner working angle (IWA) is increased. We attribute these properties of binary apodization function to the existence of threshold IWAs that allow large openings in the pupil. © 2006 International Astronomical Union. -7

The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mission is the third Japanese astronomical infrared satellite project of a 3.5m cooled telescope optimized for mid- to far-infrared observations, following the Infrared Telescope in Space (IRTS) and the ASTRO-F missions. It will employ mechanical coolers and an efficient radiative cooling system, which allow us to have a cooled (4.5K) telescope of the aperture much larger than previous missions in space. The SPICA will attack a number of key problems in present-day astrophysics, ranging from the origin of the universe to the formation of planetary systems, owing to its high spatial resolution and unprecedented sensitivity in the mid- to far-infrared. The large aperture size for cryogenically use is, however, a great challenge and demands substantial technology developments for the telescope system. We adopt monolithic mirror design in the baseline model because of the technical feasibility and reliability. We set the optical performance requirement as being diffraction limited at 5μm at the operating temperature of 4.5K. The total weight attributed to the telescope system is 700kg, which requires a very light 3.5m primary mirror together with the mirror support structure. At present we are working on two candidate materials for the SPICA telescope: silicon carbide (SiC) and carbon-fiber reinforced silicon carbide (C/SiC). This presentation gives a general overview of the SPICA mission and reports the current design and status of the SPICA telescope system, including recent progress of the development of C/SiC mirrors.

beta Pictoris (beta Pic) is a main-sequence star with an edge-on dust disk(1-3) that might represent a state of the early Solar System. The dust does not seem to be a remnant from the original protoplanetary disk, but rather is thought to have been generated from large bodies like planetesimals and/or comets(4,5). The history and composition of the parent bodies can therefore be revealed by determining the spatial distribution, grain size, composition and crystallinity of the dust through high-resolution mid-infrared observations. Here we report that the sub-micrometre amorphous silicate grains around beta Pic have peaks in their distribution around 6, 16 and 30 AU (1 AU is the Sun-Earth distance), whereas the crystalline and micrometre-sized amorphous silicate grains are concentrated in the disk centre. As sub-micrometre grains are blown quickly out from the system by radiation pressure from the central star, the peaks indicate the locations of ongoing dust replenishment, which originates from ring-like distributions of planetesimals or 'planetesimal belts'.

We have observed the 8-13 mum spectrum (R similar to 250) of the Vega-like star candidate HD 145263 using Subaru/COMICS. The spectrum of HD 145263 shows the broad trapezoidal silicate feature with the shoulders at 9.3 and 11.44 mum, indicating the presence of crystalline silicate grains. This detection implies that crystalline silicate may also be commonly present around Vega-like stars. The 11.44 mum feature is slightly shifted to a longer wavelength compared to the usual 11.2 - 3 mum crystalline forsterite feature detected toward Herbig Ae/Be stars and T Tauri stars. Although the peak shift due to the effects of the grain size cannot be ruled out, we suggest that Fe-bearing crystalline olivine explains the observed peak wavelength fairly well. Fe-bearing silicates are commonly found in meteorites and most interplanetary dust particles, which originate from planetesimal-like asteroids. According to studies of meteorites, Fe-bearing silicate must have been formed in asteroidal planetesimals, supporting the scenario that dust grains around Vega-like stars are of planetesimal origin, if the observed 11.44 mum peak is due to Fe-bearing silicates.

We carried out imaging and long-slit spectroscopic observations of the Red Rectangle in the N-band using the 8.2-m SUBARU telescope. The resulting images reveal a central bright core and an extended nebula. The central core is slightly extended in the N-band. The core radius is estimated to be similar to0.09", which corresponds to 60 AU. The core spectrum is well modeled by blackbody emission with a temperature of 358 K. The estimated size and temperature are in good agreement with the predictions of recent dusty torus models. In the north / south nebula, unidentified infrared (UIR) emission features at 8.6 mum and 11.2 mum are prominently observed. At radii > 1" they completely dominate the N-band spectra, suggesting that the nebula seen at N-band wavelengths is primarily brightened by the UIR-band emission, not by scattered light. We also detected shifts in the UIR-feature peaks with increasing distance from the center. These may be attributed to isotopic shifts due to the presence of C-13 in polycyclic aromatic hydrocarbons (PAH) like particles. In addition to the UIR emission, a broad feature at 11.27 mum is seen at a distance of 0.3" on all sides of the nebula. We attribute this to crystalline silicate olivine grains around the central torus.

The SPICA (Space Infrared Telescope for Cosmology and Astrophysics), which is a Japanese astronomical infrared satellite project with a 3.5-m telescope, is scheduled for launch in early 2010s. The telescope is cooled down to 4.5 K in space by a combination of mechanical coolers with an efficient radiative cooling system. The SPICA telescope has requirements for its total weight to be lighter than 700 kg and for the imaging performance to be diffraction-limited at 5 μm at 4.5 K. Two candidate materials, silicon carbide (SiC) and carbon-fiber-reinforced SiC (C/SiC composite), are currently under investigation for the primary mirror. A monolithic mirror design will be adopted in both cases because of the technical feasibility and reliability. This paper reports the current design and status of the SPICA telescope together with some of our recent results on laboratory cryogenic tests for the SiC and C/SiC composite mirrors.

We report the surface structure and roughness of the mirrors made of carbon fiber reinforced silicon carbide (C/SiC) composite improved for the SPICA (Space Infrared telescope for Cosmology and Astrophysics) mission. The improved C/SiC is a candidate of material for the SPICA light weight mirrors because of its superior properties: high toughness, high stiffness, small thermal deformation, feasibility to make large single dish mirror, low cost, and short term for production. The surface of the bare C/SiC composite consists of carbon fiber, silicon carbide and silicon, each of which has different hardness, so it is difficult to polish this surface smoothly. Our improved polishing technique achieved the surface roughness of better than 20nm RMS for the C/SiC composite flat mirror, which satisfies the requirement of the SPICA mission. For curved bare surface of the C/SiC mirror, the roughness is larger than 30 nm and now under improving. The Change of Bidirectional reflectance distribution function (BRDF) of the bare C/SiC composite at cryogenic temperature was measured with 632.8nm lasar. No significant difference was found between the BRDFs at 95K and that at room temperature. In order to improve surface roughness further, we are planning to apply the SiSiC slurry coating on the surface of the improved C/SiC composite. This combination can realize the surface roughness well enough to be applied even for optical telescopes.

MIR-L is a 12-26mum channel of Infrared Camera(IRC) onboard ASTRO-F. The camera employs a refractive optics which consists of 5 lenses (CsI - CsI - KRS-5 - CsI - KRS-5) and a large format Si:As IBC array detector (256 x 256 pixels). The design concept is to realize a wide field of view with a compact size. It has 2 observing modes: a wide field imaging with a field of view of 10.7 x 10.2arcmin(2) or a pixel resolution of 2.5 x 2.4arcsec(2) /pixel in 3 bands (12.5-18mum, 14-26mum, 22-26mum), and low resolution spectroscopy with a spectral resolution R = gimel/Deltagimel similar to 40 in 2 bands (11-19mum,18-26mum). It also has a small slit to adapt for spectroscopic observations of extended sources. We describe the current design of the optics and the mounting architecture of MIR-L and evaluation of the optical performance at cryogenic temperatures.

We have carried out mid-infrared 8-13 mum spectroscopic observations of C/2002 V1 (NEAT) and C/2001 RX14 (LINEAR) on 2003 January 10-11 UT using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the 8.2 m Subaru Telescope. The spectra of C/2002 V1 showed the broad silicate feature with the 11.2 mum peak, indicating the presence of crystalline olivine grains. The spectra of C/2001 RX14 also showed the broad trapezoidal silicate feature. The silicate feature profile of C/2002 V1 is explained by a combination of small (0.1 mum) amorphous olivine and pyroxene, large (2.0 mum) amorphous silicate, and small crystalline forsterite grains, while that of C/2001 RX14 is explained by small and large amorphous silicate grains without crystalline silicate grains. The ubiquity of large grains and crystalline silicate grains among these Oort Cloud comets indicates processing of the primordial interstellar matter in the early solar system and incorporation into the region where these cometary nuclei were formed.

An all-sky survey in two mid-infrared bands which cover wavelengths of 5-12mum and 12-26mum with a spatial resolution of similar to9" will be performed with the Infrared Camera (IRC) on board the ASTRO-F infrared astronomical satellite. The expected detection limits for point sources are few tens mJy. The all-sky survey will provide with the data of detection limits more than one order of magnitude deeper and of spatial resolutions an order of magnitude higher than those of the Infrared Astronomical Satellite (IRAS) survey.The IRC is optimally designed for deep imaging in pointing observations. It employs 256 x 256 Si:As IBC infrared focal plane arrays (FPA) for the two mid-infrared channels. In order to make observations with the IRC during the survey mode of the ASTRO-F, a new operation method for the arrays has been developed - the scan mode operation. In the scan mode, only 256 pixels in a single row aligned in the cross-scan direction on the array are used as the scan detector and sampled every 44ms. Special cares have been made to stabilize the temperature of the array in the scan mode, which enables to achieve a low readout noise compatible with that of the imaging mode (similar to30 e(-)). The flux calibration method in the scan mode observation is also investigated. Performance of the scan mode observations has been examined in computer simulations as well as in laboratory simulations by using the flight model camera and moving artificial point sources. In this paper we present the scan mode operation method of the array, results of laboratory performance tests, results of the computer simulation, and expected performance of the IRC all-sky survey observations.

The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mission is a Japanese astronomical infrared satellite project optimized for mid-to far-infrared observations. It will be launched at ambient temperature and cooled down on orbit by mechanical coolers on board with an efficient radiative cooling system, which allow us to have a 3.5m cooled (4.5 K) telescope in space. SPICA will answer a number of important problems in present-day astronomy, ranging from the star-formation history of the universe to the formation of planets, owing to its high spatial-resolution and unprecedented sensitivity in the mid- to far-infrared. The large aperture mirror for cryogenically use in space, however, demands a challenging development for the telescope system. A single-aperture design of the primary mirror will be adopted for the SPICA telescope rather than deployable mirror designs to avoid further complexity and ensure the feasibility. The number of actuators for the primary mirror, if needed, will be minimized. Silicon carbide and carbon-fiber reinforced silicon carbide are extensively investigated at present as the prime candidate materials for the SPICA primary mirror This presentation reports the current status of the SPICA telescope system development.

The Infrared Camera (IRC) is one of the focal-plane instruments on board the Japanese infrared astronomical space mission ASTRO-F. It will make wide-field deep imaging and low-resolution spectroscopic observations over a wide spectral range in the near- to mid-infrared (2-26mum) in the pointed observation mode of the ASTRO-F. The IRC will also be operated in the survey mode and make an all-sky survey at mid-infrared wavelengths. It comprises three channels. The NIR channel (2-5mum) employs a 512x412 InSb array, whereas both the MIR-S (5-12 mum) and the MIR-L (12-26mum) channels use 256x256 Si:As impurity band conduction (IBC) arrays. The three channels will be operated simultaneously. All the channels have 10'x10' fields of view with nearly diffraction-limited spatial resolutions. The NIR and MIR-S share the same field of view, while the MIR-L will observe the sky about 25' away from the NIR/MIR-S field of view. The IRC will give us deep insights into the formation and evolution of galaxies, the properties of brown dwarfs, the evolution of planetary disks, the process of star-formation, the properties of the interstellar medium under various physical environments, as well as the nature and evolution of solar system objects. This paper summarizes the latest laboratory measurements as well as the expected performance of the IRC.

One of the key technologies for next generation space telescope with a large-scale reflector is a material having high specific strength, high specific stiffness, low coefficient of thermal expansion and high coefficient of thermal conductivity. Several candidates such as fused silica, beryllium, silicon carbide and carbon fiber reinforced composites have been evaluated. Pitch-based carbon fiber reinforced SiC composites were developed for the SPICA space telescope mirror to comply with such requirements. Mechanical performance such as bending stiffness, bending strength and fracture toughness was significantly improved. Evaluation procedures of thermal expansion and thermal conductivity behavior at cryogenic temperatures (as low as 4.5K) were established and excellent performance for the SPICA mirror was demonstrated.

We have developed a new operating method for the Raytheon 320 x 240 pixel Si: As IBC detector (hereafter 320 x 240 FPA), the largest mid-infrared array detector currently available designed for ground-based astronomy. The array shows quite a strange behavior when a bright source is observed. In images that contain a stellar object sufficiently brighter than the background flux, the signal level of the 320 x 240 FPA drops in the vicinity or along the same row or column of the stellar object. The level-drop phenomena are caused mainly by transient variations in the characteristics of the source followers in the detector readout circuit (ROIC). We successfully corrected the variations by correlated quadruple sampling, which reduces the level-drop phenomena appreciably. We evaluated the properties of the ROIC and optimized the bias voltages supplied for the array. The detective quantum efficiency of the 320 x 240 FPA was also estimated.

We report the results of mid-infrared (7.8 mu m-13.2 mu m) high-spatial resolution imaging and spectroscopic observations of the Galactic center region with the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the Subaru telescope. The images clearly show bright infrared sources and small structures in the diffuse emission. The spectra of all the observed positions show the 9.7 mu m silicate absorption feature. After corrected for the empirically-derived extinction, the intrinsic spectra of the infrared sources show either strong silicate emission or absorption, while the intrinsic diffuse emission has a power-law type spectrum. This difference indicates a possibility of dust processing due to the interaction between the infrared sources and their surrounding medium or a different origin of the dust grains surrounding the sources from those in the diffuse region.

We have carried out mid-infrared N-band spectroscopic observations of the T Tauri star Hen 3-600A in the TW Hydra association with the Cooled Mid-Infrared Camera and Spectrometer on the 8.2 m Subaru Telescope and found structured features in its spectrum. These structured features are well explained by a combination of crystalline forsterite, crystalline enstatite, silica, and glassy olivine grains. Among intermediate-mass young stellar objects (YSOs), crystalline silicates have already been detected, but no firm detection has been reported so far for low-mass YSOs such as T Tauri stars. This is the first clear detection of crystalline silicates in low-mass YSOs, and it shows that the crystallization event occurs even in the protoplanetary disk of low-mass YSOs in the T Tauri phase. The physical processes leading to the inferred dust composition in the Hen 3-600A system may be analogous to those that occurred in the early epoch of the solar system.

We have made imaging and spectroscopic observations of the ultracompact H II region K3-50A with a spatial resolution of 0".4 using a new mid-infrared instrument, the Cooled Mid-Infrared Camera and Spectrometer, on the 8.2 m Subaru Telescope. The spectra show thermal dust emission, 9.7 mum silicate absorption, and fine-structure line emissions of [Ne II] at 12.8 mum, [Ar III] at 8.99 mum, and [S IV] at 10.1 mum. From the maps of the continuum, line emissions, and/or derived dust parameters, we identify eight mid-infrared sources in K3-50A. Especially the central [Ne II] emission has been resolved into two peaks clearly. The ionization condition is investigated with the line flux ratios I([Ar III])/I([Ne II]) and I([S IV])/I([Ne II]). It is suggested that the spectral types of the ionizing stars in K3-50A correspond to B0-O8 V, which is much later than O5.5 V, the type estimated from radio continuum observations under a single-star assumption. The three line fluxes suggest a number of Ne+ ions greater than what is ionized by a single star of any spectral type, but the numbers of Ar2+ and S3+ are similar to that formed by a single O8-O9 V star and that by a single O7-O9 V star, respectively. From these features as well as the dust temperature and the correspondence of each identified source with the near-infrared source, we propose that K3-50A is excited by at least two (possibly three) ionizing stars. This is the first convincing example that a massive stellar cluster is ionizing an ultracompact H II region.

We report on the extensive tests to characterize the performance of the infrared detector arrays for the Infrared Camera (IRC) on board the next Japanese infrared astronomical satellite, ASTRO-F. The ASTRO-F will be launched early 2004 and the IRC is one of the focal plane instruments to make observations in 2-26 mum. For the near-infrared observations of 2-5mum, a 512x412 InSb array will be employed, while two 256x256 Si:As arrays will be used for the observations of 5-26mum in the IRC. Both arrays are manufactured by Raytheon IRO.To maximize the advantage of the cooled telescope and extremely low background radiation conditions in space, the dark current and readout noise must be minimized.. The heat dissipation of the arrays also has to be minimized. To meet these requirements and achieve the best performance of the arrays, we optimized the array driving clocks, the bias voltage, and the supply currents, and evaluated the temperature dependence of the performance. In particular, we found that the voltage between the gate and source of the FET of the, multiplexer SBRC-189 had a strong dependence on temperature. This effect becomes a dominant source for the noise unless the temperature is kept within 20mK. We have achieved the readout noises of about 30e(-) and 40e(-) with the correlated double sampling for the flight model readout circuits of the InSb and Si:As arrays, respectively. These noises ensure that the background-limited performance can be achieved for the observations of IRC in the 4-26mum range in the current observing scheme.In addition, we are now planning to make scan mode observations with IRC. We have developed a new operation way of the arrays to achieve the stable response and low readout noise in the scanning operation for, the first time.The IRC is now installed in the flight model cryostat and the first end-to-end test has just been completed. We report on the expected performance of the IRC together with the array test results.

COMICS is an observatory mid-infrared instrument for the 8.2 m Subaru Telescope. It is designed for imaging and spectroscopic observations in the N- (8-13 micron) and Q-bands (16-25 micron) atmospheric windows. The design and very preliminary performances at the first light observations in December 1999 were reported at the SPIE meeting in 2000. We describe here the improved performances of COMICS and capability of high spectral resolution spectrocopy which became available from December 2001. We will also briefly report prelimnary scientific results.

We developed a new data, acquisition device for COMICS, a mid infrared instrument of the Subaru telescope. The new device was installed in place of our previous data acquisition device with a lower data transfer speed. The new device is 32 bit PCI bus and PC Linux based and provides bug-master DMA transfer function. It consists of a clock, pattern generator, frame memories, and a image co-adder. In order to achieve high operational efficiency for mid infrared instruments, the data handling speed is essential as well as the speed of A/D converter. The data transfer to the hard disk drive on the PC is made during acquiring the data at the rate higher than the data generation rate. As a result, we succeeded to reduce the dead time due to the data transfer procedure. from 60 see to less than 1 sec for 200 frames (64M bytes). Furthermore by replacing the host computer by a higher performance PC, the observation efficiency of COMICS was improved from 44% to 74% in the imaging mode. This PCI based data acquisition device can also be applied to the other instruments that have fast data rates.

The infrared camera(IRC) onboard ASTRO-F is designed for wide-field imaging and spectroscopic observations at near- and mid-infrared wavelengths. The IRC consists of three channels; NIR, MIR-S and MIR-L, each of which covers wavelengths of 2-5, 5-12 and 12-26 micron, respectively. All channels adopt compact refractive optical designs. Large format array detectors (InSb 512x412 and Si:As IBC 256x256) are employed. Each channel has 10x10 arcmin wide FOV with diffraction-limited angular resolution of the 67cm telescope of ASTRO-F at wavelengths over 5 micron. A 6-position filter wheel is placed at the aperture stop in each channel, and has three band-pass filters, two grisms/prisms and a mask for dark current measurements. The 5 sigma sensitivity of one pointed observation is estimated to be 2, 11 and 62 micro-Jy at 4, 9, 20 micron bands, respectively. Because ASTRO-F is a low-earth orbiting satellite, the observing duration of each pointing is limited to 500 seconds. In addition to pointed observations, we plan to perform mid-infrared scanning observation. Fabrications of the flight-model of NIR, MIR-S, and the warm electronics have been mostly completed, while that of MIR-L is underway. The performance evaluation of the IRC in the first end-to-end test (including the satellite system) is presented.

The design and the current development status of the Infrared Camera (IRC) onboard ASTRO-F is described. The IRC is designed for wide field imaging and slit-less spectroscopic observations at near- and mid-infrared wavelengths. The IRC consists of three channels, NIR, MIR-S and MIR-L, which cover wavelengths of 2-5, 5-12 and 12-26 micron, respectively. All of them consist of refractive optics. State-of-the-art large format array detectors are placed at the focal plane. Each channel has 10 x 10 arcmin wide field-of-view with diffraction-limited spatial resolution of 70 cm aperture of ASTRO-F telescope at wavelengths over 5 micron. We plan to have more than 7000 pointing observations dedicated for the IRC. The observational time of each pointing is limited to 500 seconds because of its low earth sun-synchronous polar orbit. The 5 sigma sensitivity of one pointing observation is estimated to be 2, 30 and 120 micro-Jy at 5, 9, 20 micron bands, respectively. Fabrication of the prototype model has been completed, and the performance tests are underway. (C) 2002 Published by Elsevier Science Ltd on behalf of COSPAR.

Mid-infrared (7.8-13.5 mum) imaging and low-resolution spectroscopic observations were made for the massive star-forming region W51 IRS 2 with spatial resolution of 1". IRS 2 was resolved into seven sources based on the continuum and the emission line maps. The nature of these sources was investigated using their thermal dust emission, the 9.7 mum absorption feature, and/or three fine-structure emission lines of [Ne II] at 12.8 mum, [Ar III] at 8.99 mum, and [S IV] at 10.51 mum Four of the sources were identified as ultracompact H II regions and one as an embedded protostar candidate. The spectral types of the ionizing sources are derived from the line ratios to be all around O9, which is much later than those (O5.5 and O7.5) derived from the radio continuum fluxes. The observed line ratios of (ultra-) compact H II regions in IRS 2 and in the literature follow a single excitation track, but it is different from that predicted from model calculations. We propose two possible resolutions for the discrepancy: (1) the employed models for the stellar atmosphere are not sufficiently accurate in the UV range, or (2) the (ultra-) compact H II regions are ionized by stellar clusters.

We have observed the Red Rectangle by our newly developed instrument COMICS attached on the SUBARU 8.2 m telescope, and obtained images and spectra in the N-band (8-13.2 mum). Diffraction limited spatial resolution (similar to 0.35 arcsec) was almost achieved, revealing differences of dust emission profiles with its distance from the central star. In the nebula region (distance > 260 AU), UIR emissions at 7.7, 8.6, 11.27, and 12.7 mum were prominent, while spectra around the central star (distance < 260 AU) are dominated by strong continuum emissions.

We have developed a near-infrared (1-2.5 mum) camera and spectrograph, called OASIS (Okayama Astrophysical System for Infrared imaging and Spectroscopy). OASIS was designed for the 188 cm telescope at Okayama Astrophysical Observatory, and developed as a common-use facility instrument. It has two observing capabilities: imaging with a field of view of 4' x 4' and long-slit spectroscopy with a resolving power of similar to 1000. This paper describes the design of OASIS and reports on the total system performance of the camera+telescope+atmosphere at the Okayama Observatory, together with the performance of an array detector, NICMOS 3, which OASIS utilizes.

A new design for an aberration-corrected concave grating for the spectral region near 10 mu m is presented. It was designed for use in the ground-based astronomical medium-resolution (lambda/Delta lambda similar to 100) Mid-Infrared Camera and Spectrometer (MICS). It provides a flat focal plane for a wide spectral range (7.5-13.5 mu m) with small aberrations, permitting efficient long-slit observations in the mid-infrared region. It permits a simple design of the spectrometer without collimator and camera mirrors, which is quite advantageous for cryogenic instruments. The grating has variable spacing grooves to reduce aberrations. In addition, the grating surface figure is designed to be toroidal and in the direction perpendicular to the grooves, aspherical, to suppress the aberrations further over a wide spectral range. The angle of the grooves is also varied to yield better efficiency near the blaze angle. The grating was fabricated by high-quality ultraprecision machining, which made these features possible. Test observations confirmed that the designed spectral resolution was achieved. (C) 2000 Optical Society of America.

We have obtained N-band spectra for 18 M Mira variables with the Mid-Infrared Camera and Spectrometer (MICS) to investigate the dust materials formed around M Mira variables. The observed spectra show a wide variety; 15 of them show a strong feature at 10 mu m, and eight and seven stars show 11 and 13 mu m bumps, respectively. We have made an analysis of oxygen-rich dust spectra by using two representative spectra empirically derived. One is the 10 mu m feature, and the other is the 11 mu m feature. Linear combinations of the two dust spectra together with the stellar continuum can describe all the observed spectra quite successfully, indicating the presence of two kinds of dust materials around M Mira variables. The 10 mu m feature is ascribed to silicate grains, while we propose to attribute the 11 mu m feature to amorphous alumina grains. We found that crystalline silicates do not appear necessary to fit any component of the spectrum. We have compared the strengths of the dust emissions with the parameters of stellar variability. We found that the strength of the silicate emission increases as the light curve becomes asymmetric, while that of the alumina emission stays constant against the change of the asymmetry factor. This can be interpreted in terms of the differences in the dust-forming region.

This paper describes the firsst light and subsequent test observations with the 8.2 m aperture Subaru Telescope constructed at the summit of Mauna Kea. Following the engineering first light, which started 1998 December, the astronomical first light and test observations were carried out in 1999 January with 4 testing instruments under seeing conditions of 0."2-0."5 for near-infrared and 0."3-0."6 for optical wavelengths. The actively supported primary mirror was shown to achieve an overall imaging performance of 0."1 (FWHM) or better in the absence of any atmospheric disturbance. The pointing accuracy of the telescope is about 1" rms, and a closed-loop tracking accuracy of less than or similar to 0."07 rms has been achieved. Infrared images of the Orion Nebula covering 5' x 5', obtained with J, K', and H-2 v = 1-0S(1) filters, have revealed much finer and fainter details of the BN/KL region, the bright bar, and other conspicuous features compared with previous observations. K' band photometry of 516 point sources yielded a luminosity funcion with a peak at K' similar to 12 mag with a long tail in K' similar to 13 mag down to K' similar to 17 mag, suggesting a fairly large number of young brown dwarfs existing in the Trapezium cluster. Several new features around the Orion BN/KL region are also reported.

In this paper, we present the design and test performance of the COMICS, the mid-IR instrument for the 8.2 m Subaru Telescope at Mauna Kea. The instrument has both imaging and long slit grating spectroscopy capabilities in the 8 - 26 mu m wavelength range. In the camera section, there are selectable three sets of lens assembly, one for the 10 mu m imaging, another for the 20 mu m imaging, and the other for the 10 mu m pupil imaging. This camera section has an SBRC 320 x 240 Si:As IBC array and serves as a slit viewer and as a camera pixel scale of 0.130 arcsec. The spectrograph section is designed to have five SBRC 320 x 240 Si:As IBC arrays. Five arrays will cover 8 13 mu m wavelength range in two positions of the grating with resolving power around 2500. So far, two arrays are installed for the spectrograph section and full spectral region is covered with tilting the grating. Selectable four sets of gratings provide spectral resolution ranging from 250 to 10000 in the N band and around 2500 in the Q band.

We have developed the Mid-Infrared Camera and Spectrometer (MICS), which is optimized for ground based observations in the N-band (7.6 - 13.6 micron) atmospheric window. The MICS has two observing capabilities, imaging and long slit low-resolution spectroscopy. The major characteristics of the MICS we nearly diffraction-limited performance, both in imaging and in spectroscopy and the capability to take a spectrum of the whole N-band range with a spectral resolving power of 100 under one exposure. The MICS employs a 2-dimensional array of 128 x 128 Si:As BIB detector, an aberration-corrected concave grating, and a high-speed read out system of a compact design with high sensitivity. In mid-infrared observations from the ground, there is a large background radiation from the telescope and the sky. The fluctuation of the background radiation is not well understood so far. We measured the sky fluctuation in the N-band region with the MICS on the UKIRT. These mesurements have revealed that (1) the sky noise was dominant below 0.5 He when the sky condition was good, and (2) the sky noise has strong excess at the positions of atmospheric water vapor lines than those without water vapor lines. In this paper, we describe the design of the MICS, including optics, cryogenics, and electronics, and its performance when used on the UKIRT. We also discuss sky noise measured by the MICS in the N-band region.

We have developed the Mid-Infrared Camera and Spectrometer (MICS), which is optimized for ground-based observations in the N-band (7.6-13.6 mu m) atmospheric window. The MICS has two observing capabilities: imaging and long slit low-resolution spectroscopy. The major characteristics of the MICS are nearly diffraction-limited performance, both in imaging and in spectroscopy and the capability to take a spectrum of the whole N-band range with a spectral resolving power of 100. The MICS employs a state-of-the-art two-dimensional array of 128 x 128 Si:As BIB detector, an aberration-corrected concave grating, and a high-speed readout system, which allows a compact design with high sensitivity.In this paper, we describe the design of MICS, including optics, cryogenics, and electronics, and its performance when used on the United Kingdom Infrared Telescope (UKIRT). We also discuss sky noise in the N band and observational techniques for efficient mid-infrared observations.

We have developed a high-speed data acquisition system, Messia-III (Modularized Extensible SyStem for Image Acquisition) for Subaru, Japanese 8.2m telescope. Messia has a direct 1-Gbps link to a host UNIX workstation. Messia is a VMEbus-based system but it does not have local OS nor CPU's in order to minimize software development and maintenance.

The infrared instrumentation plan for the Subaru Telescope is described. Four approved infrared instruments and one test observation system are now in the construction phase. They are Coronagraph Imager using Adaptive Optics (CIAO), Cooled Mid-infrared Camera and Spectrograph (COMICS), Infrared Camera and Spectrograph (IRCS), OH-Airglow Suppresser Spectrograph (OHS) and Mid-Infrared Test Observation System (MIRTOS). Their performance goals and construction schedules are summarized. The plan for procurement and evaluation of infrared arrays required by these instruments is briefly described.

In the Bright Bar region, the H-2 2-1 S(1) / 1-0 S(1) line ratio (= R2-1/1-0) has a tendency to be anti-correlated to the intensity of 1-0 S(1) (= I1-OS(1)) On the other hand, in a typical shocked gas of a bipolar outflow source, R2-1/1-0 is independent of I1-OS(1) (e.g., Orion KL). From a comparison of our results with theoretical models of high density PDRs, the Bright Bar region consists of a medium-deaf (10(4) similar to 10(5) cm(-3)) cloud and a smalt number of denser ( greater than or equal to 10(6) cm(-3)) clumps. In a global, view of the Orion Nebula, the compact distribution of Br gamma relative to H-2 1-0 S(1) indicates the existence of a PDR surrounding the H II region. Moreover, the intensity ratio of H-2 1-0 S(1) from PDRs to Br gamma is 0.17 in Orion Nebula.

We obtained spectral maps of the central 6' x 8' (0.9 pc x 1.2 pc) region of the Orion Nebula. H-2 v = 1-0 S(1), 2-1 S(1) [S(1) means J = 3-1], and Br gamma maps were obtained with the wide field Fabry-Perot imager at the Nasmyth focus of the Communications Research Laboratory 1.5 m telescope, FINAC.In the Bright Bar, a typical photodissociation region (PDR), the H-2 2-1 S(1)/1-0 S(1) line ratio (=R(2-1/1-0)) is between 0.2 and 0.6 and has a tendency to be anticorrelated to the intensity of H-2 1-0 S(1) [=I-1-0S(1)]. From a comparison of the observed R(2-1/1-0) versus I-1-0S(1) relation with theoretical models, we conclude that the H-2 thermal component in this region is due not to shock heating caused by the expansion of the H II region, but to the collisional de-excitation of the lower vibrational levels populated by cascade after UV pumping. Our results strongly suggest that the Bright Bar region is a PDR consisting of a medium density (similar to 10(4)-10(5) cm(-3)) cloud and a small number of denser (greater than or similar to 10(6) cm(-3)) clumps whose size is smaller than our spatial resolution (8 '' = 0.02 pc). We also find that the ''south region'' and ''east region'' of the Orion Nebula can be described as PDRs similar to the Bright Bar region.In the Orion KL region, a typical shocked gas of a bipolar outflow source, we find that R(2-1/1-0) is independent of I-1-0S(1). R(2-1/1-0) is similar to 0.08 near the central area of KL, the curved bridgelike structure, and the finger-like filaments of the Orion KL region (''finger region''). On the other hand, R(2-1/1-0) is similar to 0.05 at the edge of the central area. The difference in the ratio suggests that high-velocity shacks exist at the center of KL, while low-velocity shocks surround the central area. The Orion S region contains some thermal H-2 clumps which may be shock excited. The distribution of these shocked-H-2 clumps, CO J = 2-1 dumps, and far-infrared sources suggests the existence of at least two sets of bipolar outflows associated with young stellar objects in this area.In a global view of the Orion Nebula, the compact distribution of Bry relative to H-2 1-0 S(1) indicates the existence of a PDR surrounding the H II region. Moreover the intensity ratio H-2 1-0 S(1) from PDRs (R(2-1/1-0) greater than or similar to 0.15; i.e., the PDR including dense molecular clumps) to Br gamma (=R(1-0(PDR)/Br gamma)) is 0.17. By comparing this value for Orion to those for starburst galaxies (cf. R(1-0/Br gamma) = 0.4-0.9), we conclude that the typical starburst region has larger H-2-emitting areas surrounding H rr regions and/or a later average spectral type for exciting stars than the Orion Nebula, if the H, emission from starburst galaxies is predominantly fluorescent.

Sensitive molecular line observations carried out with the Nobeyama 45 m telescope have resulted in the detection of the (CO)-C-12 (d = 1-0) and (CO)-C-13 (J = 1-0) emission centered on the young classical T Tauri star, DM Tau. The derived peak antenna temperatures are 0.3 K in (CO)-C-12 and 0.1 K in (CO)-C-13. NO (CO)-O-18 emission was detected at an upper limit (3 a) of 45 mK. The emission feature has a line width of 1.7 km s(-1) and is centered at upsilon(LSR) = 5.9 km s(-1), which coincides well with the reported radial velocity for DM Tau (5.9 +/- 2.1 km s(-1)). The (CO)-C-13 profile shows a symmetric double peak, suggesting a Keplerian rotating disk. These observations suggest that the molecular gas is associated with and is most probably gravitationally bound to DM Tau. The derived radius of the gaseous disk is about 1000 AU using an optically thick disk model and a Keplerian rotating disk model. The gaseous mass is between 7 x 10(-4) and 1 x 10(-3) M. from the (CO)-C-13 intensity and the upper limit of (CO)-O-18 intensity. Our results suggest that molecular gas is depleted from the standard gas-to-dust mass ratio or that mass distribution in the disk is steeper than the standard law, r(-1.5), although our observations cannot detect emission from an optically thick gaseous component inward of r < 100 AU, if the emission comes from a Keplerian rotating disk.

The velocity field of the H-2 v = 1-0 S(1) line in the Orion-KL region was measured using a Fabry-Perot imager with 24 km s(-1) resolution. The peak velocity is bluest near the central source, approaching the rest velocity of the ambient molecular cloud with increasing distance from the center. This spatial variation of the peak velocity can be explained by an expanding spherical shell. The radius of the shell is coincident with the extent of the high-velocity molecular outflow, which drives the shell expansion. Blue wings, which reflect the motion of shocked gas in the outflow, show also an approximately spherical expansion. These results imply a more or less originally isotropic flow from the central source. A curved, bridgelike structure that encroaches on the inner edge of a disk structure is noticeable in the peak velocity map, with the bluest peak velocities. This structure is considered to be a region where the isotropic outflow from the central source strongly collides with the inner edge of the disk, which imposes a bipolar appearance on the flow.

An infrared camera has been designed and constructed for the 1.5 m telescope of the Communications Research Laboratory (CRL) using a 128 x 128 HgCdTe array detector with a switched C-MOS multiplexer (TCM 1000B). The large storage capacity (3 x 10(7) e-) of the array is advantageous for astronomical observations with long exposure in order to store many photo-electrons and under high-background conditions. We have designed a cooled optical system with a field of view of 4'.2 x 4'.2 and a resolution of 2'' pixel-1 at the Nasmyth focus of the telescope. The large field of view is important for studying large extended astronomical objects. The cooled optical system and a kTC-noise limited readout circuit has achieved high efficiency of the camera system. The array detector has been found to have a small nonlinearity in the responsivity, increasing with the stored charge, which is different from a decrease of the responsivity due to a change in the capacitance of detector, which is common in arrays without an external integration capacitance. The magnitudes of infrared standard stars taken by this infrared camera at the CRL 1.5 m telescope are compared with those of the CIT (California Institute of Technology) system, in which observations were made using a single detector; the magnitude and color transformation formulas were obtained as a function of infrared colors. The difference between the two photometric systems is small in both magnitude and color. The infrared camera system has been used to take two-dimensional infrared images of galaxies, planets, and comets, and has also been combined with a Fabry-Perot spectrometer to observe interstellar gas in a star-formation region and a supernova remnant.

We obtained an H-2 1-0 S(1) image of the south-east ridge in the supernova remnant IC 443 by using a Fabry-Perot imager. The H-2 emitting region was resolved into many clumps which had not been seen by previous observations with larger beams. The H-2 image was compared with a 21-cm H I map in order to investigate the H-2 excitation mechanism. Although the H-2 emitting area roughly overlaps the H I area, no one-to-one correlation between the peaks of H-2 and H I is found. This morphology indicates that although the H I 21-cm line is due to molecular dissociation by J-shocks, the H-2 emission peaks are caused by C-shocks in dense clumps. Consequently, the coexistence of C-shocks and J-shocks is suggested to be present at the molecular ridge of IC 443.