片坐 宏一

We carried out high spatial resolution N-band imaging and spectroscopic observations of the planetary nebula BD + 30 3639 with the Cooled Mid-Infrared Camera and Spectrometer (COMICS) mounted on the Subaru telescope. Mid-infrared images reveal a rectangle shell structure of the nebula extending over 400, which is supposed to be formed by the superwind from the central star. We have detected [ Ne-II] 12.8 mu m and the unidentified infrared (UIR) bands at 8.6 and 11.2 mu m, together with the broad plateau emission in 11-13 mu m. In addition, the spectra clearly indicate the presence of silicate absorption around 10 mu m for the first time, which increases sharply at the outside of the shell. This can be attributed to silicate grains that were formed in the O-rich phase of the central star, which is now C-rich. The present data indicate that these silicate grains are located in a very thin shell, suggesting that BD + 30 3639 underwent a short period (similar to 100 yr) of a high mass-loss rate (similar to 3 x 10(-3) M-circle dot yr(-1)) at the last epoch of the O-rich phase. N-band spectra show that the distribution of [ Ne-II] is not clearly different from that of the UIR band and suggest that the UIR band carriers coexist with the ionized gas to some extent. This may be attributed to a slow destruction of the band carriers in the ionized region of the high electron density. The 10 mu m continuum and the 11-13 mu m plateau emission are dominant in the shell region, while the UIR 11.2 mu m band becomes stronger in the outside of the shell, suggesting a change in the dust composition or the dust size distribution between the shell and the outside of the shell region. On the contrary, the peak wavelength of the UIR 11.2 mu m band agrees with the class B spectrum, which is often seen in planetary nebulae, and does not change between the shell and the outside of the shell region. These facts suggest that the UIR band carriers are originally formed in the carbon-rich stellar wind and partially destroyed in the shell by shocks. The change of the UIR band spectrum from class B to A, which is generally seen in H-II regions, should take place outside of the nebula.

Prolate (Pupil) Apodized Lyot Coronagraphs (PPALC) are known to offer optimal performances for a Lyot-type Coronagraph configuration, i.e. with all opaque occulting focal mask. One additional benefit of PPALC is its possible use in a multi-stage configuration. In theory, the coronagraphic performance can be Q(N), where Q is the energy rejection factor of one stage (the first one), and N the number of stages. Several ground-based telescopes are considering PPALC as all option for their high-contrast instrumentation (e.g. Gemini/GPI, EELT/EPICS, Subaru HiCIAO). Although the PPALC suffers from several limitations, several works are currently focused on fabricating entrance pupil apodizers and trying to find ways to overcome chromatism issues. In this work, we present the first experimental results from Multi-Stage PPALC (MS-PPALC) that was done in the context of the japanese space telescope SPICA coronagraph project. Our entrance Pupil apodizers use small diameter High Energy Beam Sensitive glass (HEBS-glass) from Canyon Materials Inc. The current results show modest coronagraphic performance due to uncompensated phase aberrations inherent to HEBS-glass material. In addition, and due to these uncompensated phase aberrations, the present optical configuration is an altered version of the originally planned set-up. However, we can demonstrate the validity the MS-PPALC concept and compare it to numerical simulations.

To set useful limits on the abundance of small-scale dark matter halos (subhalos) on a galaxy scale, we have carried out mid-infrared imaging and integral-field spectroscopy for a sample of quadruple-lens systems showing anomalous flux ratios. These observations using Subaru have been successful for distinguishing millilensing by subhalos from microlensing by stars. The current status for our lensing analysis of dark matter substructure is reported.

The SPace Infrared telescope for Cosmology and Astrophysics (SPICA) is a infrared space-borne telescope mission of the next generation following AKARI. SPICA will carry a telescope with a 3.5 m diameter monolithic primary mirror and the whole telescope will be cooled to 5 K. SPICA is planned to be launched in 2017, into the sun-earth L2 libration halo orbit by an H II-A rocket and execute infrared observations at wavelengths mainly between 5 and 200 micron. The large telescope aperture, the simple pupil shape, the capability of infrared observations from space, and the early launch gives us with the SPICA mission a unique opportunity for coronagraphic observation. We have started development of a coronagraphic instrument for SPICA. The primary target of the SPICA coronagraph is direct observation of extra-solar Jovian planets. The main wavelengths of observation, the required contrast and the inner working angle (IWA) of the SPICA coronagraph are set to be 5-27 micron (3.5-5 micron is optional), 10(-6), and a few lambda/D (and as small as possible), respectively, in which lambda is the observation wavelength and D is the diameter of the telescope aperture (3.5m). For our laboratory demonstration, we focused first on a coronagraph with a binary shaped pupil mask as the primary candidate for SPICA because of its feasibility. In an experiment with a binary shaped pupil coronagraph with a He-Ne laser (lambda=632.8nm), the achieved raw contrast was 6.7x10(-8), derived from the average measured in the dark region without active wavefront control. On the other hand, a study of Phase Induced Amplitude Apodization (PIAA) was initiated in an attempt to achieve better performance, i.e., smaller IWA and higher throughput. A laboratory experiment was performed using a He-Ne laser with active wavefront control, and a raw contrast of 6.5x10(-7) was achieved. We also present recent progress made in the cryogenic active optics for SPICA. Prototypes of cryogenic deformable by Micro Electro Mechanical Systems (MEMS) techniques were developed and a first demonstration of the deformation of their surfaces was performed with liquid nitrogen cooling. Experiments with piezo-actuators for a cryogenic tip-tilt mirror are also ongoing.

AKARI is the first Japanese astronomical infrared satellite mission orbiting around the Earth in a sun-synchronous polar orbit at the altitude of 700 kin. One of the major observation programs of the AKARI is an all-sky survey in the mid- to far-infrared spectral regions with 6 photometric bands. The mid-infrared part of the AKARI All-Sky Survey was carried out with the Infrared Camera (IRC) at the 9 and 18 mu m bands with the sensitivity of about 50 and 120 mJy (5(5 per scan), respectively. The spatial resolution is about 9.4 '' at both bands. AKARI mid-infrared (MIR) all-sky survey substantially improves the MIR dataset of the IRAS survey of two decades ago and provides a significant database for studies of various fields of astronomy ranging from star-formation and debris disk systems to cosmology. This paper describes the current status of the data reduction and the characteristics of the AKARI MIR all-sky survey data.

We describe the balloon-borne telescope (69cm aperture) for the project Tera-GATE (THz observation with GaAs photoconductors and a balloon-borne TElescope) aiming at the THz astronomical observations. THz region is the last frontier left not well explored and we are planning to make multiband photometric observations covering the wavelength from 50 mu m to 300 mu m and get completed SED data for some Young Stellar Objects in this band. The telescope, we are constructing, has image stabilizing system which cancels out pointing error (up to about +/- 0.3 degrees) of the balloon gondola, and enables us to take a long exposure needed for highly sensitive observations. We will show characteristics of the image stabilizing system, structure of the telescope, and cold stop design.

We describe the optical design of balloon-borne telescope with an image stabilizing secondary mirror which correct the pointing error of the attitude control system and enable a long-time exposure. We adopted a Cassegrain-like two-mirror system, and investigated the best mirror surface figure by surveying Conic constant (K) of the primary mirror from -1 to 0, where the secondary mirror is a high order aspheric surface to cancel spherical aberration at each K. In the small pointing error region, the classical Cassegrain system (K=-1) provides a wide field of view. However, in the large pointing error region, systems with large K provide a wide FOV. For lambda t (target wavelength) =50 mu m and 69cm aperture, a spherical primary system has acceptable optical performances when we assume the pointing error around 0.3 degree.

We present a preliminary optical design and layout for the mid-infrared (4-18 mu m) high-resolution spectrograph for I SPICA, Japanese next-generation space IR observatory with 3.5 m telescope. MIR high-resolution spectroscopy is a powerful probe to study gas-phase molecules/atoms in a, variety of astronomical objects. Space observation provides a great opportunity to study many molecular lines especially in between the atmospheric windows. SPICA gives us a, chance to realize MIR high-resolution spectroscopy from space with the large telescope aperture. The major technical challenge is the size of the spectrograph, which tends to be too large for space. We hope to overcome this problem with a novel MIR immersion grating, which can make the instrument smaller by a factor of the refractive index of the grating material. We plan to fabricate a large pitch ZnSe (n = 2.4) immersion grating with the fly-cutting technique at LLNL (see Poster paper 7018-183 by Ikeda et al.(1) and 7018-181 by Kuzmenko et al.(2) in the proceedings of this conference). We show our preliminary spectrograph designs with a spectral resolution of similar to 30,000 in 4-8 mu m (short mode) and 12-18 mu m (long mode). The instrument size can be as small as 200 x 400 mm thanks to the MIR immersion gratings. With unprecedented spectral resolution in space, which is 10-times higher than ISO-SWS. the high-resolution spectrograph for SPICA (SPICA-HIRES) could be a unique instrument that can provide most sensitive and clear spectra of this kind.

The SPICA, Japanese next generation infrared space telescope with a cooled 3.5 m primary mirror, will be a quite unique observatory in the mid and far-infrared with unprecedented sensitivity and the spatial resolving power. Here we briefly describe the key scientific objectives which can be performed only with SPICA, based on its unique design concepts. We then describe the scientific requirements for the focal plane instruments, and summarize the constraints on the various resources available for the focal plane instruments, derived from the spacecraft system design. We also outline the concept of the planned focal plane instruments, and the future development plan.Within the focal-plane instrument space (2.5m diameter, 0.5m height), two major instruments are so far planned to be equipped: one is a mid-infrared instrument, consisting of a mid-infrared camera, mid-infrared spectrometers, and a mid-infrared coronagraph, while the another is a far-infrared camera and spectrometer. The mid-infrared camera will consist of four channels covering 5-38 mu m with approximately 25-40 square arcminutes, while the mid-infrared spectrometer will have high-dispersion (R=30000) channels at 4-18 mu m and moderate-dispersion (R=3000) channels at 16-38 mu m. The mid-infrared coronagraph will have both imaging and spectroscopic capability at 5-27 mu m, with the contrast higher than 10(-6). As for the far-infrared camera and spectrometer, a Fourier-type imaging spectrometer covering 30-210 mu m is proposed and extensively studied by the European consortium (SAFARI consortium). A far-infrared and sub-millimeter grating spectrometer instrument is also under consideration by the US SPICA team.

Mid Infrared Spectrometer with an Image Slicer (MIRSIS) is a compact mid-infrared spectrometer with an image slicer as a testbed of techniques for efficient observations with next generation telescopes. MIRSIS is a]Omicron band spectrometer for ground-based observations. Optics of MIRSIS is mostly composed of reflective ones. A key point of the development of MIRSIS is a fabrication of slicer optics, which consists of slice mirrors, pupil mirrors and pseudo slit mirrors. It is necessary to develop fabrication technique of slicer optics, because shapes and alignment of these mirrors are special. Here it is also important to choose the design matched to the processing method. In this paper, we report our fabrication of the slicer optics elements in detail. As a result, we achieved the slice mirror with the micro-roughness of RMS 12nm and the angle accuracy of under 0.0041deg, the pupil mirror with the micro-roughness of RMS 20nm and the shape accuracy of PV 3micron, and the pseudo slit mirror with the angle accuracy of 0.02deg. All of the parts fabricated satisfy the required specification.

We are developing a new infrared camera MAX38 (Mid-infrared Astronomical eXplorer) for long mid-infrared (25-40 micron) astronomy for the Univ. of Tokyo Atacama 1.0-meter telescope which is the world highest infrared telescope at 5,640m altitude. Thanks to the high altitude and dry weather condition of the Atacama site we can access the 30-micron wavelength region from ground-based telescopes for the first time in the world. We employ a Si:Sb 128x128 array detector to cover the wide mid-infrared wavelength range from 8 to 38 micron. The development of the MAX38 has been almost completed. Test observations in N-band wavelength at Hiroshima Kanata telescope (Hiroshima, Japan) was successfully carried out on June 2007 and March 2008. The first 30-micron observation at Atacama is scheduled in the spring of 2009.

We have developed a cold chopper system for mid-infrared observations. This system is installed into the newly developing mid-infrared instrument, MAX38, for the University of Tokyo Atacama 1.0-m telescope. It is cooled to about 9K. The cold chopper mirror is controlled by a piezoelectric actuator with a flexure hinge lever, and enables square-wave chopping at a frequency up to 7.8 Hz. At the moment, the maximum throw of the chopper is 30 arcseconds on the sky. This cooled chopping mirror system can also be applied to the tip-tilt mirror for SPICA infrared space telescope. We carried Out the first light with Kanata 1.5-m telescope at Higashi-Hiroshima Observatory (Hiroshima, Japan) in June 2007 and March 2008. In this observation, we demonstrated that the cold chopper could cancel out the atmospheric turbulence noise of a frequency of 5 Hz at 8.9 micron.

Mid-Infrared Spectrometer with an Image Slicer (MIRSIS) is a 10micron band spectrometer for ground-based observations. Based on the optical design reported in Okamoto et al. (2006),(1) we recently developed most of optical elements and their mounts. There, we adopted designs based on an ultra-precision cut for the slice mirrors and the pupil mirrors. We also designed and partly manufactured the optical parts with switching/adjusting mechanism with cryogenic step motors. Since MIRSIS has a very complicated stereoscopic configuration of optical elements, we developed a method to adjust the optical alignment where relative positional markers and a three-dimensional measuring system are combined. We confirmed that we can achieve position and angular adjustment with error down to 0.1mm and 0.05degree through alignment test with a pair of mirrors.

Real-time capabilities are required for a controller of a large format array to reduce a dead-time attributed by readout and data transfer. The real-time processing has been achieved by dedicated processors including DSP, CPLD, and FPGA devices. However, the dedicated processors have problems with memory resources, inflexibility, and high cost. Meanwhile, a recent PC has sufficient resources of CPUs and memories to control the infrared array and to process a large amount of frame data in real-time. In this study, we have developed an infrared array controller with a software real-time operating system (RTOS) instead of the dedicated processors. A Linux PC equipped with a RTAI extension and a dual-core CPU is used as a main computer, and one of the CPU cores is allocated to the real-time processing. A digital I/O board with DMA functions is used for an I/O interface. The signal-processing cores are integrated in the OS kernel as a real-time driver module, which is composed of two virtual devices of the clock processor and the frame processor tasks. The array controller with the RTOS realizes complicated operations easily, flexibly, and at a low cost.

We have developed bandpass filters for long mid-infrared astronomy in 25 to 40 mu m. Most of materials become opaque in wavelengths longer than 25 mu m. We have applied the metal mesh method to make filters of non-transparent materials. The mesh patterns are designed based oil the FDTD calculations and fabricated by the photolithography method. Measured transmittances of the fabricated filters agree with model calculations. The mesh filter has leakage In wavelengths shorter than the peak wavelength ill principle. The most effective way to achieve a high stopband rejection is to stack several identical mesh filters incoherently. A narrow bandwidth fitted to atmospheric windows is required in the ground-based 30 mu m observations. We have fabricated a thick mesh filter without dielectric Substrate, which is main source of internal absorption. The thick mesh leads to narrowing of the bandwidth due to the waveguide effect. The fabricated non-coated thick mesh filter has a peak transmittance of 0.8 and a bandwidth of lambda/d lambda=83 at 4 K. When stacking four of these mesh filters, it is expected to achieve a stopband rejection over 50dB, a peak transmittance of 0.41, and a bandwidth of lambda/d lambda=17.5.

We have carried out the mid-infrared slit spectroscopic observations of sources in the LMC and in NGC 6946 with AKARI/IRC. We investigate the properties of the UIR bands in terms of the star forming activities. We find systematically larger ratios of UIR bands in 6-9 mu m to 11.2 mu m band in active star forming regions than in the quiet regions. This behaviour is consistent with the photo-ionization model of PAHs. Our results suggest that the ratios of UIR bands in 6-9 mu m to 11.2 mu m band can be used as more efficient and vigorous tools to measure the extent of on-going star formation in remote galaxies rather than just the presence or absence of the features themselves.

Infrared Camera (IRC) onboard AKARI satellite has carried out more than 4000 pointed observations during the phases 1 and 2, a significant amount of which were performed in the spectroscopic mode. In this paper, we investigate the properties of the spectroscopic data taken with MIR-S channel and propose a new data reduction procedure for slit-less spectroscopy of sources embedded in complicated diffuse background structures. The relative strengths of the 0(th) to 1(st) order light as well as the efficiency profiles of the 2(nd) order light are examined for various objects taken with MIR-S dispersers. The boundary shapes of the aperture mask are determined by using the spectroscopic data of uniform zodiacal emission. Based on these results, if the appropriate template spectra of zodiacal light emission and the diffuse background emission are prepared and the geometries of the diffuse structures are obtained by the imaging data, we can reproduce the slit-less spectroscopic patterns made by a uniform zodiacal emission and the diffuse background emission by a convolution of those template profiles. This technique enables us to obtain the spectra of infrared sources in highly complicated diffuse background and/or foreground structures, such as in the Galactic plane and in nearby galaxies.

The Infrared Camera (IRC) is one of two focal-plane instruments on the AKARI satellite. It is designed for wide-field deep imaging and low-resolution spectroscopy in the near- to mid-infrared (1.8-26.5 micron) in the pointed observation mode of AKARI. The IRC is also operated in the survey mode to make an All-Sky Survey at 9 and 18 microns. The IRC is composed of three channels. The NIR channel (1.8-5.5 micron) employs a, 512x412 InSb photodiode array, whereas both the MIR-S (4.6-13.4 micron) and MIR-L (12.6-26.5 micron) channels use 256x256 Si:As impurity band conduction (IBC) arrays. Each of the three channels has a field-of-view of approximately 10x10 arcmin., and they are operated simultaneously. The NIR and MIR-S channels share the same field-of-view by virtue of a beam splitter. The MIR-L observes the sky about 25 arcmin. away from the NIR/MIR-S field-of-view. The in-flight performance of the IRC has been confirmed to be in agreement with the pre-flight expectation. More than 4000 pointed observations dedicated for the IRC are successfully completed, and more than 90% of the sky are covered by the all-sky survey before the exhaustion of the Akari's cryogen. The focal-plane instruments are currently cooled by the mechanical cooler and only the NIR channel is still working properly. Brief introduction, in-flight performance and scientific highlights from the IRC cool mission, together with the result of performance test in the,,arm mission, are presented.

The present status of the development of ail extrinsic photoconductor based on a high-purity GaAs is reported. This photoconductor utilizing the shallow donor levels in GaAs and is highly sensitive for incident terahertz photons in the wavelength range 150 to 300 micron. The n-type GaAs crystal has been growth by liquid phase epitaxial (LPE) method, which is suitable to obtain thick and high-purity GaAs. The impurity concentration in GaAs layer has been decreased to the order of 10(13) atoms/cm(-3). By doping the donors lightly in the LPE growth process, C/Si, (background doped) Se and Te doped GaAs layers has been fabricated. The GaAs photoconductors using these crystals are sensitive in longer wavelength region than Ge:Ga photoconductors used in the past far-infrared astronomical observations. The most sensitive detector is obtained with C or Si background doped GaAs, of which NEP is reached to 3x10(-16) W/Hz(0.5) at the temperature of 1.5 K, at 290 micron, the peak of its responsivity spectrum.A balloon-borne telescope utilizing our GaAs photoconductors, Tera-GATE (THz observation with GaAs photoconductors and a balloon-borne Telescope) is now under development. The Tera-GATE is a 69 cm diameter telescope. On its focal plane, a photoconductor array with Winston cone has 2-mm entrance aperture and leads the incident photons to a cavity where 0.5-mm size photoconductor is installed. Measured optical efficiency of the cone/cavity system is in an acceptable range similar to 40 percent.

We present the observations of the reflection nebulae IC4954 and IC4955 region with the Infrared Camera and the Far-Infrared Surveyor (FIS) on board the infrared astronomical satellite AKARI during its performance verification phase. We obtained 7 band images from 7 to 160 mu m with higher spatial resolution and higher sensitivities than previous observations. The spatial variation in the mid-infrared color suggests that the star-formation in IC 4954/4955 is progressing from south-west to north-east. The FIS 4-band data from 65 mu m to 160 Am allow us to correctly estimate the total infrared luminosity from the region, which is about one sixth of the energy emitted from the existing stellar sources. Five candidates for young stellar objects have been detected as point sources for the first time in the 11 mu m image and it is suggested that that current star-formation has been triggered by previous star-formation activities. A wide area map of the size of about 1 degrees around the IC 4954/4955 region was created from the AKARI mid-infrared All-Sky Survey data. Together with the H 121 cm data, it suggests a large hollow structure of a degree scale, on whose edge the IC 4954/4955 region has been created, indicating star formation over three generations in largely different spatial scales.

We report on preliminary results of AKARI observations of two globular clusters, NGC 104 and NGC 362. Imaging data covering areas of about 10 x 10 arcmin(2) centered on the two clusters were obtained with the Infrared Camera (IRC) at 2.4, 3.2, 4.1, 7.0, 9.0, 11.0, 15.0, 18.0, and 24.0 mu m. We used IRC 11.0 mu m to 2MASS K-s 2 mu m flux-density ratio (F-11/F-2) and IRC 24.0 mu m to 7.0 mu m flux-density ratio (F-24/F-7) as diagnostics of circumstellar dust emission. Dust emissions are mainly detected from variable stars, obviously on the asymptotic giant branch, but some variable stars that reside below the tip of the first-ascending giant branch also show dust emissions. We found eight red sources with the F-24/F-7 ratio being greater than unity in NGC 362. Six out of the eight have no 2MASS counterparts. However, we found no such source in NGC 104.

We present the properties of 11 mu m selected sources detected in the early data of the North Ecliptic Pole Deep (NEP-Deep) Survey of AKARI. The data set covers 6 wavelength bands from 2.5 to 11 mu m, with exposure times of 10-20 minutes. This field lies within the CFHT survey with four filter bands (g', r', i', z'), enabling us to establish nearly continuous spectral energy distributions (SEDs) for wavelengths ranging from 0.4 to 11 mu m. The main sample studied here consists of 72 sources whose 11 mu m AB magnitudes are equal to or brighter than 18.5 (144 mu Jy), which is complete to more than 90%. The 11 mu m band has an advantage of sampling star-forming galaxies with low-to-medium redshifts, since the prominent PAH feature shifts into this band. As expected, we find that the majority (71%) of 11 mu m bright sources are star-forming galaxies at 0.2 less than or similar to z less than or similar to 0.7 with L-IR similar to 10(10)-10(12) L-circle dot based on detailed modelling of the SEDs. We also find four AGNs lying at various redshifts in the main sample. In addition, we discuss a few sources that have non-typical SEDs of the main sample, including a brown-dwarf candidate, a steep power-law source, a flat-spectrum object, and an early-type galaxy at moderate redshift.

We present the results of optical identifications for 257 mid-infrared sources detected with a deep 15 Am survey over approximately 80 arcmin(2) area in the AKARI performance verification field near the North Ecliptic Pole. The 15 mu m fluxes of the sources range from 1 mJy down to 40 mu Jy, approximately one half of which are below 100 mu Jy. Optical counterparts were searched for within a 2 ''-3 '' radius in both the BVRi'z' catalog generated by using the deep Subaru/Suprime-cam field, which covers one-third of the performance verification field, and the g'r'i'z' catalog based on observations made with MegaCam at CFHT. We found that the B - R and R - z' colors of sources with successful optical identifications are systematically redder than that of the entire optical sample in the same field. Moreover, approximately 40% of the 15 mu m sources show colors with R - L15 > 5, which cannot be explained by the spectral energy distribution (SED) of normal quiescent spiral galaxies, but are consistent with SEDs of redshifted (z > 1) starburst or ultraluminous infrared galaxies. This result indicates that the fraction of the ultraluminous infrared galaxies in our faint 15 mu m sample is much larger than that in our brighter 15 mu m sources, which is consistent with the evolving mid-infrared luminosity function derived by recent studies based on Spitzer 24 Am deep surveys. Based on an SED fitting technique, the nature of the faint 15 Am sources is further discussed for a selected number of sources with available K-s-band data.

AKARI, the first Japanese satellite dedicated to infrared astronomy, was launched on 2006 February 21, and started observations in May of the same year. AKARI has a 68.5 cm cooled telescope, together with two focal-plane instruments, which survey the sky in six wavelength bands from mid- to far-infrared. The instruments also have a capability for imaging and spectroscopy in the wavelength range 2-180 mu m in the pointed observation mode, occasionally inserted into a continuous survey operation. The in-orbit cryogen lifetime is expected to be one and a half years. The All-Sky Survey will cover more than 90% of the whole sky with a higher spatial resolution and a wider wavelength coverage than that of the previous IRAS all-sky survey. Point-source catalogues of the All-Sky Survey will be released to the astronomical community. Pointed observations will be used for deep surveys of selected sky areas and systematic observations of important astronomical targets. These will become an additional future heritage of this mission.

The Infrared Camera (IRC) is one of the two instruments on board the AKARI satellite. In addition to deep imaging from 1.8 to 26.5 mu m for the pointed observation mode of the AKARI, it has a spectroscopic capability in its spectral range. By replacing the imaging filters by transmission-type dispersers on the filter wheels, it provides low-resolution (lambda/delta lambda similar to 20-120) spectroscopy with slits, or in a wide imaging field-of-view (approximately 10' x 10'). The IRC spectroscopic mode is unique for space infrared missions in that it has the capability to perform sensitive wide-field spectroscopic surveys in the near- and mid-infrared wavelength ranges. This paper describes the specifications of the IRC spectrograph and its in-orbit performance.

The Infrared Camera (IRC) is one of two focal-plane instruments on the AKARI satellite. It is designed for wide-field deep imaging and low-resolution spectroscopy in the near- to mid-infrared (1.8-26.5 mu m) in the pointed observation mode of AKARI. The IRC is also operated in the survey mode to make an All-Sky Survey at 9 and 18 Am. It comprises three channels. The NIR channel (1.8-5.5 mu m) employs a 512 x 412 InSb array, whereas both the MIR-S (4.6-13.4 mu m) and MIR-L (12.6-26.5 mu m) channels use 256 x 256 Si:As impurity band conduction arrays. Each of the three channels has a field-of-view of about 10' x 10' and they are operated simultaneously. The NIR and MIR-S share the same field-of-view by virtue of a beam splitter. The MIR-L observes the sky about 25' away from the NIR/MIR-S field-of-view. The IRC gives us deep insights into the formation and evolution of galaxies, the evolution of planetary disks, the process of star-formation, the properties of interstellar matter under various physical conditions, and the nature and evolution of solar system objects. The in-flight performance of the IRC has been confirmed to be in agreement with the pre-flight expectation. This paper summarizes the design and the in-flight operation and imaging performance of the IRC.

We report on the detection of an Ha emission line in the low-resolution spectrum of a quasar, RX J1759.4+6638, at a redshift of 4.3 with the Infrared Camera (IRC) onboard AKARI. This is the first spectroscopic detection of an Ha emission line in a quasar beyond z = 4. The overall spectral energy distribution (SED) of RX J1759.4+6638 in the near- and mid-infrared wavelengths agrees with a median SED of the nearby quasars; also, the flux ratio of F(Ly alpha)/F(H alpha) is consistent with those of previous reports for lower-redshift quasars.

We present results on mid-infrared imaging and spectroscopic observations of the nearby late-type spiral NGC 6946 with the Infrared Camera on board AKARI. Based on mid-infrared imaging with the S7 (7 mu m) and S11(11 mu m) bands, we found that the S7/S11 ratios have larger values in the arm region, containing many star-forming regions, than in the interarm. Slit spectra of an interarm and a star-forming region show a series of unidentified infrared (UIR) bands at 6.2, 7.7, 8.6, and 11.2 mu m. The strengths of the 6.2, 7.7, and 8.6 mu m bands are larger relative to the 11.2 mu m band in the star-forming region, than in the interarm, even if the interstellar extinction of A(V) = 3 mag towards the star-forming region is taken into account. The increase in the 6.2 mu m and 7.7 mu m features relative to the 11.2 mu m feature is consistent with the ionization model of PAHs. The ratio of the UIR features to the plateau emission under the 7.7 mu m and 8.6 mu m features and/or the ratio of the 7.6 mu m/7.8 mu m components in the 7.7 mu m feature increase in the star-forming region compared to the interarm. This variation can be accounted for by the hypothesis that the photo-evaporation of PAH clusters produce small free-flying PAHs in the star-forming region. The ratios of 6.2 mu m/11.2 mu m, 7.7 mu m/11.2 mu m, and 8.6 mu m/11.2 mu m may be tools to measure the star-formation activity in remote galaxies if these ratios and their variations are well examined and established for a large sample.

We present an initial analysis of AKARI 18 mu m-selected galaxies using all 9 photometric bands at 2-24 mu m available in the Infrared Camera (IRC), in order to demonstrate new capabilities of AKARI cosmological surveys with this unprecedented wavelength coverage at mid-infrared (MIR) bands. We detected 72 sources at 18 mu m in an area of 50.2 arcmin(2) in the AKARI/IRC monitor field towards the North Ecliptic Pole (NEP). From this sample, 25 galaxies with probable redshifts of z greater than or similar to 0.5 were selected with a single colour cut (N2 -N3 > 0.1) for a detailed spectral energy distribution (SED) analysis with ground-based BVRi'z' JK data. Using an SED radiative transfer model of starbursts covering the wavelength range UV-submm, we derived photometric redshifts from the optical-MIR SEDs of 18 mu m-selected galaxies. From the best-fit SED models, we showed that the IRC all-band photometry is capable of tracing a steep rise in the flux at the blue side of the polycyclic aromatic hydrocarbon (PAH) 6.2 mu m emission feature. This indicates that the IRC all-band photometry is useful to constrain the redshift of infrared galaxies, specifically for dusty galaxies with a less prominent 4000 A break. Also, we found that the flux dip between the PAH 7.7 and 11.2 mu m emission feature is recognizable in the observed SEDs of galaxies at z similar to 1. This pilot study suggests the possibility of detecting many interesting galaxy properties in the NEP-Deep and Wide surveys, such as a systematic difference in SEDs between high- and low-z Ultra-Luminous InfraRed Galaxies, and a large variation of the PAH inter-band strength ratio in galaxies at high redshifts.

We report on the first results of a near- and mid-infrared deep survey with the Infrared Camera (IRC) onboard AKARI in the performance-verification phase. Simultaneous observations by the Near-InfraRed (NIR), Mid-InfraRed Short (MIR-S), and Mid-InfraRed Long (MIR-L) channels of the IRC with effective integration times of 4529, 4908, and 44 17 seconds at 3, 7, and 15 mu m, covering 86.0, 70.3, and 77.3 arcmin(2) area, detected 955, 298, and 277 sources, respectively. The 5 or detection limits of the survey are 6.0, 31.5, and 71.2 mu Jy and the 50% completeness limit are 24.0, 47.5, and 88.1 mu Jy at 3, 7, and 15 mu m, respectively. Observation are limited by source confusion at 3 mu m. We have confirmed the turnover in the 15 mu m differential source counts around 400 mu Jy, previously detected by surveys with the Infrared Space Observatory. The faint end of 15 mu m raw source counts agrees with those from deep surveys in the GOODS fields, carried out with the Spitzer IRS peak up imager and predictions of current galaxy evolution models. These results indicate that deep surveys with comprehensive wavelength coverage at mid-infrared wavelength are very important to investigate the evolution of infrared galaxies at high redshifts.

We present the 3.5 m SPace Infrared telescope for Cosmology and Astrophysics (SPICA) space telescope, the launch of which is schedule around year 2015 by the Japanese HII-A rocket, and specifically discuss its use in the context of direct observation of extra-solar planets. This actively cooled (4.5 K), single aperture telescope will operate in the mid and far infrared spectral regions, and up to submillimetric wavelengths (200 mu m). The lowest spectral region (5 to 20 mu m), where the spatial resolution is the most favorable, will be dedicated to high contrast imaging with coronagraphy. This article describes the SPICA coronagraph project in terms of science, as well as our efforts to study a suitable instrumental concept, compatible with the constraints of the telescope architecture.

We present the results of mid-infrared N-band spectroscopy of the Herbig Ae/Be system MWC1080 using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on board the 8 m Subaru Telescope. The MWC1080 has a geometry such that the diffuse nebulous structures surround the central Herbig B0 type star. We focus on the properties of polycyclic aromatic hydrocarbons (PAHs) and PAH-like species, which are thought to be the carriers of the unidentified infrared (UIR) bands in such environments. A series of UIR bands at 8.6, 11.0, 11.2, and 12.7 µm is detected throughout the system and we find a clear increase in the UIR 11.0 µm/11.2 µm ratio in the vicinity of the central star. Since the UIR 11.0 µm feature is attributed to a solo-CH out-of-plane wagging mode of cationic PAHs while the UIR 11.2 µm feature to a solo-CH out-of-plane bending mode of neutral PAHs, the large 11.0 µm/11.2 µm ratio directly indicates a promotion of the ionization of PAHs near the central star.

We present the status of the development of a coronagraph for the Space Infrared telescope for Cosmology and Astrophysics (SPICA). SPICA is the next generation of infrared space-borne telescope missions following to AKARI, led by Japan. SPICA will carry a telescope that has a 3.5 in diameter monolithic primary mirror and the whole telescope will be cooled to 4.5 K. It is planned to launch SPICA into the sun-earth L2 libration halo orbit using H II-A rocket in the middle of the 2010s and execute infrared observations at wavelengths mainly between 5 and 200 micron. The SPICA mission gives us a unique opportunity for coronagraph observations, because of the large telescope aperture, the simple pupil shape, the capability of infrared observations from space, and the early launch. We have started development of the SPICA coronagraph in which the primary target is direct observation of extra-solar Jovian planets. The main wavelengths of observation, the required contrast and the inner working angle (IWA) of the SPICA coronagraph instrument are set to be 5-27 micron, 10(-6), and a few VD (and as small as possible), respectively, in which A is the observation wavelength and D is the diameter of the telescope aperture (3.5m). We focused on a coronagraph with a binary shaped pupil mask as the primary candidate for SPICA because of its feasibility. Nano-fabrication technology using electron beam lithography was applied to manufacture a high precision mask and a laboratory experiment with a He-Ne laser (lambda=632.8nm) was performed in air without active wavefront control. The raw contrast derived from the average measured in the dark region reached 6.7x10(-8). On the other hand, a study of Phase Induced Amplitude Apodization (PIAA) was started in an attempt to achieve higher performance, i.e., smaller IWA and higher throughput. A hybrid solution using PIAA and a shaped pupil mask was proposed. A laboratory experiment was performed using a He-Ne laser with. active wavefront control via a 32x32 channel deformable mirror. A raw contrast of 6.5x 10(-7) was achieved. Designs of binary shaped pupil mask are presented for the actual SPICA pupil which is obstructed by the telescope's secondary mirror and its support. Subtraction of point spread function (PSF) was also evaluated.

SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is a Japanese astronomical infrared satellite project with a 3.5-m telescope. The target year for launch is 2017. The telescope is cooled down to 4.5 K in space by a combination of newly-developed mechanical coolers with an efficient radiative cooling system at the L2 point. 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 pm at 4.5 K. Material for the SPICA telescope mirrors is silicon carbide (SiC). Among various types of SiC, primary candidates comprise normally-sintered SiC, reaction-sintered SiC, and carbon-fiber-reinforced SiC; the latter two have been being developed in Japan. This paper reports the current design and status of the SPICA telescope along with our recent activities on the cryogenic optical testing of SiC and C/SiC composite mirrors, including the development of an innovative support mechanism for cryogenic mirrors, which are based on lessons learned from a SiC 70 cm telescope onboard the previous Japanese infrared astronomical mission AKARI.

We present high spatial resolutionmid-infrared (MIR) imaging and spectroscopic observations of the dwarf galaxy NGC1569 with COMICS on the Subaru telescope. The [S iv] 10.5 mu m image clearly shows four pointlike sources and one extended source together with the diffuse emission. The brightest MIR source (MIR1) coincides with the intense H ii region, which does not have a corresponding optical source and should thus be a source embedded in dust clouds. The infrared luminosity suggests that there are about 40 O7 stars associated with MIR1. The second brightest source located similar to 1."5 south of MIR1 (MIR2) is detected for the first time. This source is not seen in the radio continuum. These characteristics can be accounted for if ionizing regions in the source are compact and optically thick in the radio. The large infrared luminosity (similar to 2 x 10(8) L-circle dot) suggests that there are about 950 O7 stars in MIR2 and significant contributions from sources other than O-type stars, such as less massive stars and/or pre-main-sequence stars. If this interpretation is correct, MIR2 could be in a very early phase of massive star formation. The unidentified infrared (UIR) band at 11.2 mu m is also detected in the spectrum of MIR2. The strength of the UIR band decreases with the [S iv] emission, suggesting that the UIR band weakens and the band carriers are destroyed in strong radiation fields. Super star cluster (SSC) A is also detected in the N-band images. The mid-infrared characteristics support the difference in the ages between two components of SSC A.

We observed embedded super-star clusters (SSCs) in blue compact dwarf galaxies (BCDs) IIZw40 and He2-10 with N-band and Q-band imaging and spectroscopy using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on board the 8m Subaru Telescope. Our infrared images of Henize 210 resolve the radio knots (knots I-V Kobulnicky &amp Johnson 1999) and the N- and Q-band spectra show the strong [NeII] 12.8 m and the [SIII] 18.71 m together with relatively weak [SIV] 10.51 m and [ArIII] 8.99 m as well as the distinct unidentified infrared (UIR) bands at 8.6, 11.2 and 12.7 m. We find the typical stellar spectral type of the members in the SSCs is O9 using the CoStar model (Stasinska &amp Schaerer 1997) and that the ionization environment in the most deeply embedded SSC(POS/#D) is the softest among those SSCs. The UIR bands exhibit a flat distribution over the galaxy and do not show a correlation with the MIR continuum, suggesting that polycyclic aromatic hydrocarbons (PAHs) are not strongly associated with the SSCs. We also find a possible decrease in the UIR 12.7 m/11.2 m ratio inside the embedded SSCs, suggesting that smooth-edged large PAHs are dominant (Hony et al. 2001) there. The small UIR to continuum ratio inside the embedded SSCs also suggests that the size distribution of the carbonaceous dust is skewed to the larger ones inside the embedded SSCs. Possible destruction of smaller species by harsh radiation field in the vicinity of massive stars due to the smaller heat capacity and/or the coagulation process that have been undertaken in dense dusty embedded SSCs would explain our results consistently. From the mid-infrared spectroscopy of IIZw40, the UIR bands are detected only in the south-western border of the mid-infrared peaks, suggesting the uneven distribution of PAHs within 410 6yr (Vanzi et al. 1996) after the nuclear starburst triggered in the merging of two small original galaxies. © 2007 International Astronomical Union.

We have obtained 8 - 13 mu m spectra of 30 young (1-10 Myr) low- mass pre-main-sequence stars using COMICS on the 8.2m Subaru Telescope to examine dust evolution in protoplanetary disks. Most spectra show silicate emission features of various strengths and shapes, indicative of dust processing during the different stages of protoplanetary disk evolution. We have analyzed the observed silicate emission features using a simple model previously applied to the more massive and luminous Herbig Ae/Be systems. We determined the feature strength and shape and derived the composition and typical size of the silicate dust grains. We confirm the previously reported dependency of the silicate feature strength and shape on the grain size of the amorphous silicate dust. We examine the relation between the derived dust properties and stellar and circumstellar disk parameters, such as systemic age, luminosity of H alpha (LH alpha), disk mass, and opacity power-law index beta at radio wavelengths. A possible relation is found between silicate feature strength (grain size indicator) and the LH alpha, which may be an indicator of accretion activity. It implies that the turbulence induced by accretion activity may be important for grain size evolution in the disk. No clear correlation between the crystallinity and the stellar/disk parameters is found. We find that on average 5%-20% in mass of the silicate dust grains is in crystalline form, irrespective of systemic age. This latter finding supports the idea that crystalline silicate is formed at an early evolutionary phase, probably at the protostellar phase, and is remaining during the later stages.

We present sets of configurations of binary-shaped pupil coronagraphs optimized for a realistic space telescope to directly detect extrasolar giant planets. For the purpose of mid-infrared observations, the target contrast ratio is set to 10(-7). We made a systematic assessment of the performance of two recently proposed pupil shapes, "checkerboard" and "concentric ring" masks, where a large central obstruction due to a secondary mirror and its related support spiders was introduced into the telescope pupil. It turned out that, if the secondary mirror diameter is smaller than similar to 15% of the diameter of the primary, the checkerboard-type masks are more promising in terms of the total high-contrast area. With such a small secondary, we propose to modify the original symmetrical checkerboard apodization function. This modification enables us to achieve a 10(-7) contrast at an inner working angle (IWA) of 4.0 lambda/D. On the other hand, when the secondary mirror size cannot be reduced to that level, the concentric ring masks are preferable because of their larger transmission. It was also found that the transmission through the optimal binary masks exhibits two characteristic features as the IWA increases: firstly, abrupt increases and secondly, plateaus. We attribute this nature of the binary apodization functions to the existence of threshold]WAS that allow large openings in the pupil.

Faint standard stars in the mid-infrared region ( less than a few hundred millijanskys at 9 mu m) are required for the on-orbit calibration of the Infrared Camera (IRC) on board ASTRO-F because of its high sensitivity, as well as the small dynamic range. Mid-infrared low-resolution (lambda/Delta lambda similar to 250) spectra of six faint K and M giant stars (70 - 180 mJy at 9 mu m, K1.5-M0 III), which are located in the north ecliptic polar region and are thus suitable for calibrators for the IRC, are obtained by using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the Subaru telescope to test the faint-infrared standard-star network recently constructed for space-borne instruments. The spectra are directly calibrated relative to Vega (A0 V). The present results indicate that the spectra of the faint standard K - M0 giant stars show good agreement with those predicted in the standard network within 10% accuracy on average. The overall spectral shapes are also in agreement with the predictions. In particular, the observed SiO absorption feature in the 8 mu m region matches well with the prediction for an M0 III star. The present observations directly connect a primary standard calibrator (Vega) to faint K giant calibrators of the network in the 10 mu m region and validate several faint (similar to 0.1 Jy) members of the standard-star network for the first time. Absolute calibrations are provided for five of the medium-band filters of the COMICS instrument in the 10 mu m window.

An all-sky survey in two mid-infrared bands covering wavelengths from 6 to 12 and 14 to 26 mu m, with a spatial resolution of similar to 9 ''.4-10 '', will be performed with the Infrared Camera (IRC) on board the ASTRO-F infrared astronomical satellite. The expected detection limit for point sources is 80-130 mJy (5 sigma). The all-sky survey will provide data with a detection limit and a spatial resolution an order of magnitude deeper and higher, respectively, than those of the Infrared Astronomical Satellite survey. The IRC is optimally designed for deep imaging in staring observations. It employs 256 x 256 Si: As IBC infrared focal plane arrays for the two mid-infrared channels. In order to make observations with the IRC during the scanning observations for the all-sky survey, a new method of operation for the arrays has been developed - "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 they are sampled every 44 ms. Special care has been taken to stabilize the temperature of the array in scan mode, which enables the user to achieve a low readout noise, comparable to that in the imaging mode (20-30 e(-)). The accuracy of the position determination and the flux measurement for point sources is examined both in computer simulations and laboratory tests with the flight model camera and moving artificial point sources. In this paper we present the scan mode operation of the array, the results of the computer simulation and the laboratory performance test, and the expected performance of the IRC all-sky survey observations.

We present the status of the development of a coronagraph for the Space Infrared telescope for Cosmology and Astrophysics (SPICA). SPICA is the next generation infrared space-borne telescope missions led by Japan. The SPICA satellite will be equipped with a telescope that has a 3.5 m diameter monolithic primary mirror and the whole telescope will be cooled to 4.5 K. The satellite is planed be launched early in the 2010s into the sun-earth L2 libration halo orbit and execute infrared observations at wavelengths mainly between 5 and 200 micron. The SPICA mission gives us a unique opportunity for coronagraph observations, because of the large telescope aperture, a simple pupil shape, capability of infrared observations from space and the early launch. We have started development of the SPICA coronagraph in which the primary target is direct observation of extra-solar Jovian planets. The main wavelengths of observation, the required contrast and the inner working angle (IWA) of the SPICA coronagraph instrument are set to be 5-20 micron, 10(6), and approximately 5 lambda/D respectively, where lambda is the observation wavelength and D is the diameter of the telescope aperture. Coronagraphs using a checkerboard mask and a concentric ring mask have been investigated. We found some solutions for the SPICA-pupil, which has a large obstruction due to the secondary mirror and its supports. We carried out laboratory experiments to examine coronagraphs obtained using checkerboard-type pupil masks with a central obstruction. Nano-fabrication technology with electron beam was applied to manufacture a high precision mask consisting of a patterned aluminum film on a glass substrate and its performance was confirmed by experiments with visible light. Contrast higher than 10(6) was achieved. In the future, we will be developing a cryogenic mid-infrared test-bed to investigate the SPICA coronagraphs.

We present our high spectral resolution tandem Fabry-Perot (FP) spectrometer for detecting the pure rotational transition line of molecular Hydrogen S (1) at 17.035 mu m. It is designed to be attached to a new dedicated 1 m telescope planned to be put at a dry and high-altitude site. The spectrometer has two sequentially placed FP units (order 1000 and 99 with finesse > 50) consisting of ZnSe etalons and one narrow band filter. We will be able to obtain high spectral resolution of R=50,000 at 17.035 mu m. The ZnSe etalons of 110mm diameter with > 94% reflectance are to be provided from Barr Associates. The interval and tilt of etalons are sensed and regulated by piezo actuators and newly-developed capacitance sensors, which resolve 100nm in vacuum and 30K environment. By changing the interval, we change the wavelength of transmission up to 17.2 pm, corresponding to v = 3000 km/s. We adopt an on-axis catadioptric system, in which the two FP units are placed. The focal plane detector is a Raytheon SB-774, 320 x 240 pixel array of Si:As, yielding 9.1 x 6.8 arcmin(2) field of view with 1.7 arcsec pixel scale. To suppress the thermal background radiation and dark current of the SiAs detector, the system is cooled down to 6K at the detector and 35K for the whole optical system by two refrigerators. The development of spectrometer will be completed in 2007.

A spectrometer with integral field units on large optical/ infrared telescopes enables efficient spectroscopy of moderately extended objects. In future mid-infrared observations with 30m class telescopes, where circumstellar disks larger than the spatial resolution will be major targets, such efficient observations are strongly desirable. Here we present an optical design of our new N-band image slicing spectrometer to test basic techniques for future image slicing spectrometers on larger telescopes. Our prototype image slicer follows the idea of the advanced image slicer considering not only object images but also pupil images 1 and is optimized for the N-band (10 micron atmospheric window). Five slicing mirrors and five pupil mirrors are used to slice the field of view and make a rearranged pseudo slit image. The pseudo slit image is collimated, dispersed by a grating, and imaged on a Si:As 320x240 array. For the slicing mirrors, we plan to use polished stainless mirrors of 300 micron width 2. The spectral resolution is set as about 200. We plan to put an imaging optics module for target aquisition in addition to the simple image slicer module. The whole optics is designed to be compact (about 600 mm x 450 mm x 300 mm), which will allow us to make test observations easily with various telescopes.

We present mid-infrared imaging at 11.7 mu m for the quadruple lens systems PG 1115+080 and B1422+231 using the cooled mid-infrared camera and spectrometer ( COMICS) attached on the Subaru Telescope. These lensed QSOs are characterized by their anomalous optical and radio flux ratios, as obtained for A1 and A2 images of PG 1115+080 and A, B, and C images of B1422+231, respectively, i.e., such flux ratios are hardly able to be reproduced by lens models with a smooth mass distribution. Our mid-infrared observations for these images have revealed that the mid-infrared flux ratio A2/A1 of PG 1115+080 is virtually consistent with smooth lens models (but inconsistent with the optical flux ratio), whereas for B1422+231, the mid- infrared flux ratios among the A, B, and C images are in good agreement with the radio flux ratios. We also identify a clear infrared bump in the spectral energy distributions of these QSOs, thereby indicating that the observed mid- infrared fluxes originate from a hot dust torus around a QSO nucleus. Based on the size estimate of the dust torus, we place limits on the mass of a substructure in these lens systems causing the anomalous optical or radio flux ratios. For PG 1115+ 080, the mass of a substructure inside an Einstein radius M-E is less than or similar to 16M(circle dot), corresponding to either a star or a low-mass CDM subhalo having a mass of M-100(SIS) less than or similar to 2.2 x 10(4) M-circle dot inside a radius of 100 pc if modeled as a singular isothermal sphere (SIS). For B1422+231, we obtain M-E greater than or similar to 209 M-circle dot, indicating that a CDM subhalo is more likely, having a mass of M-100(SIS) greater than or similar to 7.4 x 10(4) M-circle dot.

The birth of very massive stars is not well understood(1-3), in contrast to the formation process of low-mass stars like our Sun(4,5). It is not even clear that massive stars can form as single entities; rather, they might form through the mergers of smaller ones born in tight groups(6,7). The recent claim of the discovery of a massive protostar in M17 (a nearby giant ionized region) forming through the same mechanism as low-mass stars(8) has therefore generated considerable interest. Here we show that this protostar has an intermediate mass of only 2.5 to 8 solar masses (M.), contrary to the earlier claim of 20. (ref. 8). The surrounding circumstellar envelope contains only 0.09M. and a much more extended local molecular cloud has 4-9M..

We report the negative detection of the S( 1) pure rotational line emission of molecular hydrogen at 17.035 mum for four young stars, HD 163296, MWC 863, CQ Tau, and LkCa 15, for which Infrared Space Observatory ( ISO) observations detected the S( 1) emission, with the Cooled Mid- Infrared Camera and Spectrometer ( COMICS) on the 8.2 m Subaru Telescope. We did not detect the line emission toward the central star nor within 1500 of the central star along the slit for any of the present targets. Upper limits of the present observations are much smaller than previous line flux estimates based on ISO Short Wavelength Spectrometer ( SWS) observations, irrespective of the intrinsic line width. The present results indicate that the emission detected by the ISO SWS is not concentrated within the disk. Our detection limit of the H-2 S( 1) emission corresponds to upper limits of the disk masses of ( 0: 72 3: 8); 10(-4) M. within a radius of similar to30 - 45 AU for the optically thin emission from the gas of 150 K. The upper limits of the disk masses are significantly lower than those of the warm molecular hydrogen mass predicted by the model ( Chiang & Goldreich 1997), suggesting that the optically thick emission from dust dominates in the radiation from the disks in the mid- infrared wavelength. We point out that detectability of the H-2 emission in young stars depends on the evolution of the disks, particularly in the sedimentation and growth of dust grains in the disk.

The MIR-L is the mid-IR (12-26 μm) instrument for Japanese infrared astronomical satellite, the ASTRO-F. The instrument has 2 observing modes: a wide field imaging mode with a field of view of 10.7 × 10.2 arcmin 2 and a low resolution spectroscopic mode with a spectral resolution R -λ/Δλ about 20. The spectroscopic mode provides with not only slit-spectroscopy for extended sources but also slitless-spectroscopy for point sources. We describe here the design, manufacturing, and performance evaluation of the cryogenic optical system of the MIR-L. The concept of the optical system design is to realize wide field observations with a compact size. The instrument employs a refractive optics of 5 lenses (CsI - CsI - KRS-5 - Csl - KRS-5) with a 256 × 256 pixel Si:As IBC array detector, 3 filters, and 2 grisms. The refractive indices of CsI and KRS-5 at the operating temperature of about 6 K have ambiguities because of the difficulty of the measurements. We therefore designed the MIR-L optics with tolerances for the uncertainties of the indices. Since both CsI and KRS-5 have the fragility and the large thermal expansion, we designed a specialized mounting architecture to prevent from making damages and/or decentrations of the lenses at cryogenic temperatures under the serious vibration during the launch. As a result, the optical system of the MIR-L has passed both vibration and thermal cycle tests without damage and performance degradation, and achieved diffraction limited performance over its full wavelength range at the operating temperature.

The ASTRO-F is an on-going infrared satellite mission covering 2-200 μm infrared wavelengths. Not only the all-sky survey in the mid-IR and far-IR, but also deep pointing observations are planned especially at 2-26 μm. In this paper, we focus on the near-infrared (NIR) channel of the infrared camera (IRC) on board ASTRO-F, and describe its design, and results of the imaging mode performance evaluation as a single component. The NIR consists of 4 lenses (Silicon - Silicon - Germanium - Silicon) with a 412 × 512 In:Sb detector. Three broad-band filters, and two spectroscopic elements are installed covering 2-5 μm wavelengths. Since the ASTRO-F telescope and the focal plane are cooled to 6 K, the evaluation of adjustment of the focus and the end-to-end test of the whole NIR camera assembly have to be done at cryogenic temperature. As a result of measurements, we found that the transverse magnification and distortion are well matched with the specification value (1 versus 1.017 and 1 %), while the chromatic aberration, point spread function, and encircled energy are slightly degraded from the specification (300 μm from 88 μm, >1pixel from ∼1pixel, 80 % encircled energy radius >1pixel from ∼1pixel). However, with these three measured values, in-flight simulations show the same quality as specification without degradation. In addition to the image quality, we also verified the ghost image generated from the optical element (1 % energy fraction to the original image) and the slightly narrowed field of view (10' × 9.5' from 10' × 10'). For the responsivity, the NIR shows expected response. Totally, the NIR imaging mode shows satisfactory results for the expected in-flight performance.