研究者業績
基本情報
論文
198-
SPECTRAL ENERGY DISTRIBUTION OF GALAXIES (284) 228-+ 2012年We present the first determination of the 18 mu m luminosity function (LF) of galaxies at 0.006 < z < 0.7 (the average redshift is similar to 0.04) using the AKARI mid-infrared All-Sky Survey catalogue. We have selected a 18 mu m flux-limited sample of 243 galaxies from the catalogue in the SDSS spectroscopic region. We then classified the sample into four types; Seyfert 1 galaxies (including QSOs), Seyfert 2 galaxies, LINERs and Star-Forming galaxies using mainly [OIII]/H beta vs. [NII]/H alpha line ratios obtained from the SDSS.As a result of constructing Seyfert 1 and Seyfert 2 LFs, we found the following results; (i) the number density ratio of Seyfert 2s to Seyfert 1s is 3.98 +/- 0.41 obtained from Sy1 and Sy2 LFs; this value is larger than the results obtained from optical LFs. (ii) the fraction of Sy2s in the entire AGNs may be anti-correlated with 18 mu m luminosity. These results suggest that the torus structure probably depends on the mid-infrared luminosity of AGNs and most of the AGNs in the local Universe are obscured by dust.
-
SPACE TELESCOPES AND INSTRUMENTATION 2012: OPTICAL, INFRARED, AND MILLIMETER WAVE 8442 2012年Mid-infrared Camera and Spectrometer (MCS) is one of focal plane instruments for SPICA (Space Infrared Telescope for Cosmology and Astrophysics), which have 3 m class 6 K cooled telescope. MCS will provide wide field imaging and low-, medium-, and high-resolution spectroscopic observing capabilities with 7 detectors in the wavelength range from 5 to 38 micron. Large format array detectors are required in order to realize wide field of view in imaging and wide spectral coverage in spectroscopy. We are planning to cover the wavelength range of 5-26 micron by Si: As IBC 2K x 2K and 20-38 micron by Si:Sb BIB 1K x 1K. The development status and their design including the electrical and thermal design are described.
-
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 63(5) 1117-1138 2011年10月We present the results of an unbiased asteroid survey in the mid-infrared wavelength region with the Infrared Camera (IRC) on board the Japanese infrared satellite AKARI. About 20% of the point source events recorded in the AKARI All-Sky Survey observations are not used for the IRC Point Source Catalog (IRC-PSC) in its production process because of a lack of multiple detection by position. Asteroids, which are moving objects on the celestial sphere, remain in these "residual events". We identify asteroids out of the residual events by matching them with the positions of known asteroids. For the identified asteroids, we calculate the size and albedo based on the Standard Thermal Model. Finally we have a new brand of asteroid catalog, named the Asteroid Catalog Using AKARI (AcuA), which contains 5120 objects, about twice as many as the IRAS asteroid catalog. The catalog objects comprise 4953 main belt asteroids, 58 near-Earth asteroids, and 109 Jovian Trojan asteroids. The catalog is publicly available via the Internet.
-
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 63(4) 823-834 2011年8月We present mid-infrared narrow-band images of the Orion BN/KL region, and N-band low-resolution spectra of IRc2 and the nearby radio source "I". The distributions of the silicate absorption strength and the color temperature have been revealed with a subarcsec resolution. The detailed structure of the 7.8 mu m/12.4 mu m color temperature distribution was resolved in the vicinity of IRc2. A mid-infrared counterpart to source I has been detected as a large color temperature peak. The color temperature distribution shows an increasing gradient from IRc2 toward source 1, and no dominant temperature peak is seen at IRc2. The spectral energy distribution of IRc2 could be fitted by a two-temperature component model, and the "warmer component" of the infrared emission from IRc2 could be reproduced by scattering of radiation from source I. IRc2 itself is not self-luminous, but is illuminated and heated by an embedded luminous young stellar object located at source I.
-
ADVANCES IN SPACE RESEARCH 48(2) 323-333 2011年7月We present the SPICA Coronagraphic Instrument (SCI), which has been designed for a concentrated study of extra-solar planets (exoplanets). SPICA. mission provides us with a unique opportunity to make high contrast observations because of its large telescope aperture, the simple pupil shape, and the capability for making infrared observations from space. The primary objectives for the SCI are the direct coronagraphic detection and spectroscopy of Jovian exoplanets in infrared, while the monitoring of transiting planets is another important target. The specification and an overview of the design of the instrument are shown. In the SCI, coronagraphic and non-coronagraphic modes are aplicable for both an imaging and a spectroscopy. The core wavelength range and the goal contrast of the coronagraphic mode are 3.5-27 mu m, and 10(-6), respectively. Two complemental designs of binary shaped pupil mask coronagraph are presented. The SCI has capability of simultaneous observations of one target using two channels, a short channel with an InSb detector and a long wavelength channel with a Si:As detector. We also give a report on the current progress in the development of key technologies for the SCI. (C) 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.
-
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC 123(905) 852-864 2011年7月The AKARI All-Sky Catalogues are an important infrared astronomical database for next-generation astronomy that take over the IRAS catalog. We have developed an online service, AKARI Catalogue Archive Server (AKARI-CAS), for astronomers. The service includes useful and attractive search tools and visual tools. One of the new features of AKARI-CAS is cached SIMBAD/NED entries, which can match AKARI catalogs with other catalogs stored in SIMBAD or NED. To allow advanced queries to the databases, direct input of SQL is also supported. In those queries, fast dynamic cross-identification between registered catalogs is a remarkable feature. In addition, multiwavelength quick-look images are displayed in the visualization tools, which will increase the value of the service. In the construction of our service, we considered a wide variety of astronomers' requirements. As a result of our discussion, we concluded that supporting users' SQL submissions is the best solution for the requirements. Therefore, we implemented an RDBMS layer so that it covered important facilities, including the whole processing of tables. We found that PostgreSQL is the best open-source RDBMS products for such purpose, and we wrote codes for both simple and advanced searches into the SQL stored functions. To implement such stored functions for fast radial search and cross-identification with minimum cost, we applied a simple technique that is not based on HTM or HEALPix. In contrast, the online application layer became compact and was written in simple procedural PHP codes. In total, our system realizes cost-effective maintenance and enhancements.
-
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC 123(903) 561-567 2011年5月We evaluate the effects of high-energy ionizing particles on the Si: As impurity band conduction (IBC) mid-infrared detector on board AKARI, the Japanese infrared astronomical satellite. IBC-type detectors are known to be little influenced by ionizing radiation. However, we find that the detector is significantly affected by in-orbit ionizing radiation even after spikes induced by ionizing particles are removed. The effects are described as changes mostly in the offset of detector output, but not in the gain. We conclude that the changes in the offset are caused mainly by increase in dark current. We establish a method to correct these ionizing radiation effects. The method is essential to improve the quality and to increase the sky coverage of the AKARI mid-infrared all-sky-survey map.
-
ASTRONOMY & ASTROPHYSICS 529 2011年5月Aims. We present a new sample of active galactic nuclei (AGNs) identified using the catalog of the AKARI Mid-infrared (MIR) All-Sky Survey. Our MIR search has the advantage of detecting AGNs that are obscured at optical wavelengths by extinction.Methods. We first selected AKARI 9 mu m excess sources with F(9 mu m)/F(K-S) > 2 where K-S magnitudes were taken from the Two Micron All Sky Survey. We then obtained follow-up near-infrared spectroscopy with the AKARI/IRC to confirm that the excess is caused by hot dust. We also obtained optical spectroscopy with the Kast Double Spectrograph on the Shane 3-m telescope at Lick Observatory.Results. On the basis of these observations, we detected hot dust with a characteristic temperature of greater than or similar to 500 K in two luminous infrared galaxies. The hot dust is suspected to be associated with AGNs that exhibit their nonstellar activity not in the optical, but in the near- and mid-infrared bands, i.e., they harbor buried AGNs. The host galaxy stellar masses of similar to 4-6 x 10(9) M-circle dot are small compared with the hosts in optically-selected AGN populations. These objects were missed by previous surveys, demonstrating the power of the AKARI MIR All-Sky Survey to widen AGN searches to include more heavily obscured objects. The existence of multiple dusty star clusters with massive stars cannot be completely ruled out with our current data.
-
ASTRONOMY & ASTROPHYSICS 519 2010年9月Context. The first Japanese infrared astronomical satellite, AKARI, has completed an All-Sky Survey at mid-to far-infrared wavelengths with higher spatial resolutions and sensitivities than the previous survey with Infrared Astronomical Satellite (IRAS).Aims. We search for new T Tauri star (TTS) candidates with the mid-infrared (MIR) part of the AKARI All-Sky Survey at 9 and 18 mu m wavelengths.Methods. We used the point source catalogue (PSC) obtained by the Infrared Camera (IRC) on board AKARI. We combined the 2MASS PSC and the 3rd version of the USNO CCD Astrograph Catalogue (UCAC) with the AKARI IRC-PSC, and surveyed 517 known TTSs over a 1800-square-degree part of the Taurus-Auriga region to develop criteria to extract TTSs. We considered asymptotic giant branch (AGB) stars, post-AGB stars, planetary nebulae (PNe), and galaxies, which have similar MIR colours, to separate TTSs from these sources. We finally searched for new TTS candidates from AKARI IRC-PSC in the same Taurus-Auriga region.Results. Of the 517 known TTSs, we detected 133 sources with AKARI: 46 sources were not detected by IRAS. Based on the colour-colour and colour-magnitude diagrams made from the AKARI, 2MASS, and UCAC surveys, we propose the criteria to extract TTS candidates from the AKARI All-Sky data, and 68/133 AKARI detected TTSs have passed these criteria. On the basis of our criteria, we selected 176/14725 AKARI sources as TTS candidates that are located around the Taurus-Auriga region. Comparing these sources with SIMBAD, we found that 148 are previously identified sources including 115 young stellar objects (YSOs), and 28 unidentified sources.Conclusions. Based on SIMBAD identifications, we infer the TTS-identification probability using our criteria to be similar to 75%. We find 28 TTS candidates, of which we expect similar to 21 to be confirmed once follow-up observations can be obtained. Although the probability of similar to 75% is not so high, it is affected by the completeness of the SIMBAD database, and we can search for TTSs over the whole sky, and all star-forming regions.
-
ASTROPHYSICAL JOURNAL LETTERS 718(2) L199-L203 2010年8月The disk around AB Aur was imaged and resolved at 24.6 mu m using the Cooled Mid-infrared Camera and Spectrometer on the 8.2 m Subaru Telescope. The Gaussian full width at half-maximum of the source size is estimated to be 90 +/- 6 AU, indicating that the disk extends further out at 24.6 mu m than at shorter wavelengths. In order to interpret the extended 24.6 mu m image, we consider a disk with a reduced surface density within a boundary radius R(c), which is motivated by radio observations that suggest a reduced inner region within about 100 AU from the star. Introducing the surface density reduction factor f(c) for the inner disk, we determine that the best match with the observed radial intensity profile at 24.6 mu m is achieved with R(c) = 88 AU and f(c) = 0.01. We suggest that the extended emission at 24.6 mu m is due to the enhanced emission from a wall-like structure at the boundary radius (the inner edge of the outer disk), which is caused by a jump in the surface density at R(c). Such a reduced inner disk and geometrically thick outer disk structure can also explain the more point-like nature at shorter wavelengths. We also note that this disk geometry is qualitatively similar to a pre-transitional disk, suggesting that the AB Aur disk is in a pre-transitional disk phase.
-
Astronomy and Astrophysics 514(1) 2010年5月3日Context. The AKARI, a Japanese infrared space mission, has performed an All-Sky Survey in six infrared-bands from 9 to 180 μm with higher spatial resolutions and better sensitivities than IRAS. Aims. We investigate the mid-infrared (9 and 18 μm) point source catalog (PSC) obtained with the infrared camera (IRC) onboard AKARI, in order to understand the infrared nature of the known objects and to identify previously unknown objects. Methods. Color-color diagrams and a color-magnitude diagram were plotted with the AKARI-IRC PSC and other available all-sky survey catalogs. We combined the Hipparcos astrometric catalog and the 2MASS all-sky survey catalog with the AKARI-IRC PSC. We furthermore searched literature and SIMBAD astronomical database for object types, spectral types, and luminosity classes. We identified the locations of representative stars and objects on the color-magnitude and color-color diagram schemes. The properties of unclassified sources can be inferred from their locations on these diagrams. Results. We found that the (B-V) vs. (V-S9W) color-color diagram is useful for identifying the stars with infrared excess emerged from circumstellar envelopes or disks. Be stars with infrared excess are separated well from other types of stars in this diagram. Whereas (J-L18W) vs. (S9W-L18W) diagram is a powerful tool for classifying several object types. Carbon-rich asymptotic giant branch (AGB) stars and OH/IR stars form distinct sequences in this color-color diagram. Young stellar objects (YSOs), pre-main sequence (PMS) stars, post-AGB stars, and planetary nebulae (PNe) have the largest mid-infrared color excess and can be identified in the infrared catalog. Finally, we plot the L18W vs. (S9W-L18W) color-magnitude diagram, using the AKARI data together with Hipparcos parallaxes. This diagram can be used to identify low-mass YSOs and AGB stars. We found that this diagram is comparable to the [24] vs. ([8.0]-[24]) diagram of Large Magellanic Cloud sources using the Spitzer Space Telescope data. Our understanding of Galactic objects will be used to interpret color-magnitude diagram of stellar populations in the nearby galaxies that Spitzer Space Telescope observed. Conclusions. Our study of the AKARI color-color and color-magnitude diagrams will be used to explore properties of unknown objects in the future. In addition, our analysis highlights a future key project to understand stellar evolution with a circumstellar envelope, once the forthcoming astronometrical data with GAIA are available. © ESO, 2010.
-
ASTROPHYSICAL JOURNAL LETTERS 714(1) L152-L156 2010年5月We present the Spitzer/Infrared Spectrograph spectrum of the main-sequence star HD165014, which is a warm (greater than or similar to 200 K) debris disk candidate discovered by the AKARI All-Sky Survey. The star possesses extremely large excess emission at wavelengths longer than 5 mu m. The detected flux densities at 10 and 20 mu m are similar to 10 and similar to 30 times larger than the predicted photospheric emission, respectively. The excess emission is attributable to the presence of circumstellar warm dust. The dust temperature is estimated as 300-750 K, corresponding to the distance of 0.7-4.4 AU from the central star. Significant fine-structured features are seen in the spectrum and the peak positions are in good agreement with those of crystalline enstatite. Features of crystalline forsterite are not significantly seen. HD165014 is the first debris disk sample that has enstatite as a dominant form of crystalline silicate rather than forsterite. Possible formation of enstatite dust from differentiated parent bodies is suggested according to the solar system analog. The detection of an enstatite-rich debris disk in the current study suggests the presence of large bodies and a variety of silicate dust processing in warm debris disks.
-
ASTRONOMY & ASTROPHYSICS 514 2010年5月Context. AKARI is the first Japanese astronomical satellite dedicated to infrared astronomy. One of the main purposes of AKARI is the all-sky survey performed with six infrared bands between 9 mu m and 200 mu m during the period from 2006 May 6 to 2007 August 28. In this paper, we present the mid-infrared part (9 mu m and 18 mu m bands) of the survey carried out with one of the on-board instruments, the infrared camera (IRC).Aims. We present unprecedented observational results of the 9 mu m and 18 mu m AKARI all-sky survey and detail the operation and data processing leading to the point source detection and measurements.Methods. The raw data are processed to produce small images for every scan, and the point sources candidates are derived above the 5 sigma noise level per single scan. The celestial coordinates and fluxes of the events are determined statistically and the reliability of their detections is secured through multiple detections of the same source within milli-seconds, hours, and months from each other.Results. The sky coverage is more than 90% for both bands. A total of 877 091 sources (851 189 for 9 mu m, 195 893 for 18 mu m) are confirmed and included in the current release of the point source catalog. The detection limit for point sources is 50 mJy and 90 mJy for the 9 mu m and 18 mu m bands, respectively. The position accuracy is estimated to be better than 2 ''. Uncertainties in the in-flight absolute flux calibration are estimated to be 3% for the 9 mu m band and 4% for the 18 mu m band. The coordinates and fluxes of detected sources in this survey are also compared with those of the IRAS survey and are found to be statistically consistent.
-
ASTRONOMY & ASTROPHYSICS 514 2010年5月Context. The AKARI, a Japanese infrared space mission, has performed an All-Sky Survey in six infrared-bands from 9 to 180 mu m with higher spatial resolutions and better sensitivities than IRAS. Aims. We investigate the mid-infrared (9 and 18 mu m) point source catalog (PSC) obtained with the infrared camera (IRC) onboard AKARI, in order to understand the infrared nature of the known objects and to identify previously unknown objects.Methods. Color-color diagrams and a color-magnitude diagram were plotted with the AKARI-IRC PSC and other available all-sky survey catalogs. We combined the Hipparcos astrometric catalog and the 2MASS all-sky survey catalog with the AKARI-IRC PSC. We furthermore searched literature and SIMBAD astronomical database for object types, spectral types, and luminosity classes. We identified the locations of representative stars and objects on the color-magnitude and color-color diagram schemes. The properties of unclassified sources can be inferred from their locations on these diagrams.Results. We found that the (B - V) vs. (V - S 9W) color-color diagram is useful for identifying the stars with infrared excess emerged from circumstellar envelopes or disks. Be stars with infrared excess are separated well from other types of stars in this diagram. Whereas (J - L18W) vs. (S 9W - L18W) diagram is a powerful tool for classifying several object types. Carbon-rich asymptotic giant branch (AGB) stars and OH/IR stars form distinct sequences in this color-color diagram. Young stellar objects (YSOs), pre-main sequence (PMS) stars, post-AGB stars, and planetary nebulae (PNe) have the largest mid-infrared color excess and can be identified in the infrared catalog. Finally, we plot the L18W vs. (S 9W - L18W) color-magnitude diagram, using the AKARI data together with Hipparcos parallaxes. This diagram can be used to identify low-mass YSOs and AGB stars. We found that this diagram is comparable to the [24] vs. ([8.0] - [24]) diagram of Large Magellanic Cloud sources using the Spitzer Space Telescope data. Our understanding of Galactic objects will be used to interpret color-magnitude diagram of stellar populations in the nearby galaxies that Spitzer Space Telescope observed.Conclusions. Our study of the AKARI color-color and color-magnitude diagrams will be used to explore properties of unknown objects in the future. In addition, our analysis highlights a future key project to understand stellar evolution with a circumstellar envelope, once the forthcoming astronometrical data with GAIA are available.
-
ASTRONOMY & ASTROPHYSICS 514 2010年5月Aims. We investigate the structure of the interstellar medium (ISM) and identify the location of possible embedded excitation sources from far-infrared (FIR) line and mid-infrared continuum emission maps.Methods. We carried out imaging spectroscopic observations of four giant Galactic star-forming regions with the Fourier transform spectrometer (FTS) onboard AKARI. We obtained [OIII] 88 mu m and [C II] 158 mu m line intensity maps of all the regions: G3.270-0.101, G333.6-0.2, NGC 3603, and M 17.Results. For G3.270-0.101, we obtained high-spatial-resolution [O III] 88 mu m line-emission maps and a FIR continuum map for the first time, which imply that [O III] 88 mu m emission identifies the excitation sources more clearly than the radio continuum emission. In G333.6-0.2, we found a local [O III] 88 mu m emission peak, which is indicative of an excitation source. This is supported by the 18 mu m continuum emission, which is considered to trace the hot dust distribution. For all regions, the [C II] 158 mu m emission is distributed widely as suggested by previous observations of star-forming regions.Conclusions. We conclude that [O III] 88 mu m emission traces the excitation sources more accurately than the radio continuum emission, especially where there is a high density and/or column density gradient. The FIR spectroscopy provides a promising means of understanding the nature of star-forming regions.
-
ADVANCES IN SPACE RESEARCH 45(8) 1000-1006 2010年4月The SPace Infrared telescope for Cosmology and Astrophysics (SPICA) is a proposed mid-to-far infrared (4-200 mu m) astronomy misson, scheduled for launch in 2017. A single. 3.5 m aperture telescope would provide superior image quality at 5-200 mu m, and its very cold (similar to 5 K) instrumentation would provide superior sensitivity in the 25-200 mu m wavelength regimes. This would provide a breakthrough opportunity for studies of exoplanets, protoplanetary and debris disk, and small solar system bodies This paper summarizes the potential scientific Impacts for the proposed instrumentation (C) 2009 COSPAR Published by Elsevier Ltd All rights reserved
-
Proceedings of SPIE - The International Society for Optical Engineering 7735(PART 1) 2010年A mid-infrared (MIR) imager and spectrometer is being investigated for possible consideration for construction in the early operation of the Thirty Meter Telescope (TMT). Combined with adaptive optics for the MIR, the instrument will afford 15 times higher sensitivity (0.1mJy as 5 sigma detection in 1hour integration in the N-band imaging) and 4 times better spatial resolution (0.08'') at 10μm compared to 8m-class telescopes. In addition, its large light-gathering power allows high-dispersion spectroscopy in the MIR that will be unrivaled by any other facility. We, a collaborating team of Japanese and US MIR astronomers, have carefully considered the science drivers for the TMT MIR instrument. Such an instrument would offer both broad and potentially transformative science. Furthering the science cases for the MIRES1, where high-dispersion spectroscopy was emphasized, we discuss additional capabilities for the instrument drawn from the enlarged science cases. The science cases include broader areas of astronomical fields: star and planet formation, solar system bodies, evolved stars, interstellar medium (ISM), extragalaxies, and cosmology. Based on these science drivers, essential instrument capabilities and key enhancement are discussed (see the companion paper Tokunaga et al. 20102): specifically imaging, lowand high-spectral resolution modes, integral field spectroscopy, and polarimetry. © 2010 Copyright SPIE - The International Society for Optical Engineering.
-
Proceedings of SPIE - The International Society for Optical Engineering 7735(PART 1) 2010年Ground-based mid-infrared observations have two distinct advantages over space observations despite relatively lower sensitivity. One is the high spatial resolution and the other is the monitoring capability. These advantages can be emphasized particularly for the next coming ground-based infrared project University of Tokyo Atacama Observatory (TAO). Thanks to the low water vapor of the TAO site (5,640m) and the large aperture of the telescope (6.5meter), we can observe at 30 micron with a spatial resolution of 1 arcsec. It is about ten times higher than that of current space telescopes. The TAO is also useful for monitoring observations because of the ample observing time. To take these advantages we are now developing a new mid-infrared infrared instrument for the TAO 6.5-meter telescope. This covers a wide wavelength range from 2 to 38 micron with three detectors (Si:As, Si:Sb, and InSb). Diffraction limited spatial resolution can be achieved at wavelengths longer than 7 micron. Low-resolution spectroscopy can also be carried out with grisms. This instrument equips a newly invented "field stacker" for monitoring observations. It is an optical system that consists of two movable pick-up mirrors and a triangle shaped mirror, and combine two discrete fields of the telescope into camera's field of view. It will enable us to apply a differential photometry method and dramatically improve the accuracy and increase the feasibility of the monitoring observations at the mid-infrared wavelengths. © 2010 Copyright SPIE - The International Society for Optical Engineering.
-
PATHWAYS TOWARDS HABITABLE PLANETS 430 284-+ 2010年We present the SPICA Coronagraph Instrument for the direct imaging and spectroscopy of exoplanets. The SPICA mission gives us a unique opportunity for high-contrast observations because of the large telescope aperture, the simple pupil shape, and the capability for infrared observations from space. The primary goal of this coronagraph is the direct detection and spectroscopy of Jovian exoplanets. The specifications, performance, and the design of the instrument are shown. The main wavelengths and the contrast required for the observations are 3.5 - 27 mu m, and 10(-6), respectively. We also show the progress of the development of key technology to realize this instrument. The non-coronagraphic mode of this instrument is potentially useful for characterization of inner planets via observation of planetary transit and Color Differential Astrometry(CDA). We expect the SPICA coronagraph will provide drastic progress for understanding various planetary systems by it's unique capability, mid will be a fruitful precursor for a future mission targeting terrestrial planets.
-
SPACE TELESCOPES AND INSTRUMENTATION 2010: OPTICAL, INFRARED, AND MILLIMETER WAVE 7731 2010年SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is an astronomical mission optimized for mid- and far-infrared astronomy, envisioned for launch in 2018. Mid-infrared instruments for SPICA are required to have three basic capabilities; a wide-field imaging, spectroscopic capability, and coronagraphic capability as an option. First two capabilities are implemented by three instruments; MIRACLE(Mid-infRAred Camera w/o Lens), MIRMES(Mid-IR Medium-resolution Echelle Spectrometer), and MIRHES(Mid-IR High-resolution Echelle Spectrometer). Here, we present an optical architecture of the union of MIRACLE, MIRMES, and MIRHES. MIRACLE has two channels (-S for short wavelength and -L for long wavelength) to cover the wavelength range 5 to 40 micron. MIRACLE-L and MIRMES are packaged into one unit with common optical bench and MIRACLE-S and MIRHES are packaged into another unit. Two units are independent with each other and occupy different field of view of the SPICA telescope. Each unit has common fore-optics shared by MIRACLE and MIR(M/H)ES. This fore-optics is designed using reflective mirror optics only, and has wide filed of view(FOV). Most of the FOV is used by MIRACLE and small part of the FOV is used by MIRMES or MIRHES. This structure of the instruments reduces the size and weight of the instruments. This benefit outweigh the complexity of the instruments.
-
GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY III 7735 2010年We successfully carried out 30-micron observations from the ground-based telescope for the first time with our newly developed mid-infrared instrument, MAX38, which is mounted on the University of Tokyo Atacama 1.0-m telescope (miniTAO telescope). Thanks to the high altitude of the miniTAO (5,640m) and dry weather condition of the Atacama site, we can access the 30-micron wavelength region from ground-based telescopes. To achieve the observation at 30-micron wavelength, remarkable devices are employed in MAX38. First, a Si:Sb 128x128 array detector is installed which can detect long mid-infrared light up to 38-micron. Second, we developed metal mesh filters for 30-micron region band-pass filter, which are composed of several gold thin-films with cross-shaped holes. Third, a cold chopper, a 6-cm square plane mirror controlled by a piezoelectric actuator, is built into the MAX38 optics for canceling out the atmospheric turbulence noise. It enables square-wave chopping with a 50-arcsecound throw at a frequency more than 5-Hz. Finally, a low-dispersion grism spectrometer (R similar to 50) will provide information on the transmission spectrum of the terrestrial atmosphere in 20 to 40 micron. In this observation, we clearly demonstrated that the atmospheric windows around 30-micron can be used for the astronomical observations at the miniTAO site.
-
SPACE TELESCOPES AND INSTRUMENTATION 2010: OPTICAL, INFRARED, AND MILLIMETER WAVE 7731 2010年Bright source catalogues based on the new mid- and far-infrared all-sky survey by the infrared astronomical satellite AKARI were released into the public domain in March 2010. The mid- infrared catalogue contains more than 870 thousand sources observed at 9 and 18 mu m, and the far-infrared catalogue provides information of about 427 thousand sources at 65, 90, 140, and 160 mu m. The AKARI catalogues will take over the IRAS catalogues and will become one of the most important catalogues in astronomy. We present the characteristics of the AKARI infrared source catalogues as well as current activity for the future versions.
-
SPACE TELESCOPES AND INSTRUMENTATION 2010: OPTICAL, INFRARED, AND MILLIMETER WAVE 7731 2010年The Mid-Infrared Medium-Resolution Eschelle Spectrometer (MIRMES) is one of the focal-plane instrument onboard SPICA mission proposed in the pre-project phase. It is designed for measuring the strengths and the profiles of lines and bands emitted from various phases of materials including ionized gas, gas-phase molecules, solid-phase molecules and dust particles in the wavelengths from 10 to 40 mu m. The MIRMES provides a medium resolution (R = 700-1500) spectroscopic capability in the mid-infrared spectral range (10-36 mu m) with integrated field units of a field-of-view of about 12 '' x 6 '' for shorter wavelength range (10-20 mu m) and 12 '' x 12 ''. 5 for longer wavelength range (20-36 mu m). The science targets of the MIRMES and the results of the concept study on its optical design and the expected performance are described.
-
GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY III 7735 2010年A mid-infrared imager and spectrometer is under consideration for construction in the first decade of the Thirty-Meter Telescope (TMT) operation (see the companion paper by Okamoto). MIRES, a mid-infrared high-spectral resolution optimized instrument, was previously proposed to provide these capabilities to the TMT community. We have revised the design in order to provide an improved optical design for the high-spectral resolution mode with R=120,000, improved imaging with sky chopping, low-spectral resolution mode with an integral field spectrograph, and polarimetry. In this paper we describe the optical design concepts currently under consideration.
-
SPACE TELESCOPES AND INSTRUMENTATION 2010: OPTICAL, INFRARED, AND MILLIMETER WAVE 7731 2010年Mid-InfRAred Camera w/o LEns (MIRACLE) is a focal plane instrument for the future JAXA/ESA infrared astronomical mission, SPICA. MIRACLE is designed for wide field imaging (5' x 5') and low-resolution spectroscopic observations (R similar to 100) over a wide spectral range in the mid-infrared wavelengths (5-38 mu m). Thanks to the SPICA's large aperture (3-m class) and cold (<6K) telescope, MIRACLE has a better sensitivity than JWST/MIRI at the wavelength over 20 mu m (3.5 mu Jy at 20 mu m, R=5, S/N=5, 3600 seconds) and its wider field of view (FOV) provides a faster mapping speed in its full spectral range for point sources. Confocal off-axis reflective imaging system provides a wide FOV with diffraction limited image quality over wide spectral range. MIRACLE consists of two channels: MIRACLE-S and MIRACLE-L, which are optimized for 5-26 mu m and 2038 mu m, respectively. Each of them consists of a fore-optics and a rear-optics, each of which has a pupil position equipped with a filter wheel and a grating wheel, respectively. A field stop wheel, which provides optimal slits in the spectroscopic mode and a wide FOV in the imaging mode, is installed at the focal plane of the fore-optics. A large format array detector (Si:As 2Kx2K for MIRACLE-S and Si:Sb 1Kx1K for MIRACLE-L) is installed at the focal plane of the rear-optics in order to achieve Nyquist sampling of the point spread function. Contiguous wavelength coverage is considered in choice of the filter bands from the experiences in the Spitzer and AKARI observations. We will present the results of conceptual design study including sensitivity analysis.
-
ASTROPHYSICAL JOURNAL 706(1) 665-675 2009年11月We made mid-infrared (MIR) observations of the 10M(circle dot) Herbig Be star HD200775 with the Cooled Mid-Infrared Camera and Spectrometer on the 8.2 m Subaru Telescope. We discovered diffuse emission of an elliptical shape extended in the north-south direction in an similar to 1000 AU radius around unresolved excess emission. The diffuse emission is perpendicular to the cavity wall formed by the past outflow activity and is parallel to the projected major axis of the central close binary orbit. The centers of the ellipse contours of the diffuse emission are shifted from the stellar position, and the amount of the shift increases as the contour brightness level decreases. The diffuse emission is well explained in all of geometry (the shape and the shift), size, and configuration by an inclined flared disk where only its surface emits the MIR photons. Our results give the first well-resolved infrared disk images around a massive star and strongly support that HD200775 is formed through the disk accretion. The disk survives the main accretion phase and shows a structure similar to that around lower mass stars with "disk atmosphere." At the same time, the disk also shows properties characteristic of massive stars such as photoevaporation traced by the 3.4 mm free-free emission and unusual silicate emission with a peak at 9.2 mu m, which is shorter than that of many astronomical objects. It provides a good place to compare the disk properties between massive and lower mass stars.
-
ASTROPHYSICAL JOURNAL 697(1) 610-618 2009年5月We present mid-infrared imaging at 11.7 mu m for the quadruple lens systems, MG0414+0534 and Q2237+030, using the cooled mid-infrared camera and spectrometer attached on the Subaru telescope. MG0414+0534 is characterized by a bright pair of lensed images (A1, A2) and their optical flux ratio A2/A1 deviates significantly from the prediction of a smooth-lens model. Q2237+030 is "the Einstein Cross" being comprised of four lensed images, which are significantly affected by microlensing in a foreground lensing galaxy. Our mid-infrared observations of these lensed images have revealed that the mid-infrared flux ratio for A2/A1 of MG0414+0534 is nearly unity (0.90 +/- 0.04). We find that this flux ratio is systematically small, at 4-5 sigma level, compared with the prediction of a best smooth-lens model (1.09) represented by a singular isothermal ellipsoid and external shear. The smooth-lens model, which also considers the additional lensing effect of the possible faint satellite, object X, still provides a large flux ratio of A2/A1=1.06, thereby suggesting the presence of more substructures that can explain our observational result. In contrast, for Q2237+030, our high signal-to-noise observation indicates that the mid-infrared flux ratios between all the four images of Q2237+030 are virtually consistent with the prediction of a smooth-lens model. Based on the size estimate of the dust torus surrounding the nuclei of these QSOs, we set limits on the mass of a substructure in these lens systems, which can cause anomalies in the flux ratios. For MG0414+0534, since the required mass of a substructure inside its Einstein radius is greater than or similar to 360 M(circle dot), millilensing by a cold dark matter substructure is most likely. If it is modeled as a singular isothermal sphere, the mass inside a radius of 100 pc is given as greater than or similar to 1.0 x 10(5) M(circle dot). For Q2237+030, there is no significant evidence of millilensing, so the reported anomalous flux ratios in shorter wavelengths are entirely caused due to microlensing by stars.
-
ASTROPHYSICAL JOURNAL LETTERS 695(1) L88-L91 2009年4月Photometry of the A0 V main-sequence star HD 106797 with AKARI and Gemini/T-ReCS is used to detect excess emission over the expected stellar photospheric emission between 10 and 20 mu m, which is best attributed to hot circumstellar debris dust surrounding the star. The temperature of the debris dust is derived as T-d similar to 190 K by assuming that the excess emission is approximated by a single temperature blackbody. The derived temperature suggests that the inner radius of the debris disk is similar to 14 AU. The fractional luminosity of the debris disk is 1000 times brighter than that of our own zodiacal cloud. The existence of such a large amount of hot dust around HD 106797 cannot be accounted for by a simple model of the steady state evolution of a debris disk due to collisions, and it is likely that transient events play a significant role. Our data also show a narrow spectral feature between 11 and 12 mu m attributable to crystalline silicates, suggesting that dust heating has occurred during the formation and evolution of the debris disk of HD 106797.
-
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 61(2) 291-299 2009年4月We report on observations of the mysterious object TYC 3159-6-1 located toward the Cygnus X region. It shows interesting characteristics in the AKARI mid-infrared All-Sky Survey. The central star is clearly detected as a point Source at 9 mu m, while no point-like source, but a large shell-like Structure is seen around the source at 18 mu m. The optical spectrum indicates the presence of the weak H alpha emission oil the red smooth continuum, whereas the mid-infrared N-band spectrum shows neither excess emission nor significant silicate absorption. Interferometric continuum observations at 104 GHz do not show any appreciable peak at the position of the star. On the basis of these observations, we investigate three possibilities of concerning the nature of TYC 3159-6-1: a nearby young stellar object, a heavily extincted high-mass star, and ail asymptotic giant branch (AGB) star with a detached shell. We conclude that none of these cases can account for the observations consistently, and the nature of TYC 3159-6-1 remains a mystery.
-
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC 121(877) 260-265 2009年3月We present our first results on the development and evaluation of a cryogenic deformable mirror (DM) based on Micro Electro Mechanical Systems (MEMS) technology. A MEMS silicon-based DM chip with 32 channels, in which each channel is 300 mu m x 300 mu m in size, was mounted on a silicon substrate in order to minimize distortion and prevent it from being permanently damaged by thermal stresses introduced by cooling. The silicon substrate was oxidized to obtain electric insulation and had a metal fan-out pattern on the surface. For cryogenic tests, we constructed a measurement system consisting of a Fizeau interferometer, a cryostat cooled by liquid N-2, zooming optics, electric drivers. The surface of the mirror at 95 K deformed in response to the application of a voltage, and no significant difference was found between the deformation at 95 K and that at room temperature. The power dissipation by the cryogenic DM was also measured, and we suggest that this is small enough for it to be used in a space cryogenic telescope. The properties of the DM remained unchanged after five cycles of vacuum pumping, cooling, warming, and venting. We conclude that fabricating cryogenic DMs employing MEMS technology is a promising approach. Therefore, we intend to develop a more sophisticated device for actual use, and to look for potential applications including the Space Infrared Telescope for Cosmology & Astrophysics (SPICA), and other missions.
-
EXPERIMENTAL ASTRONOMY 23(1) 193-219 2009年3月The Space Infrared telescope for Cosmology and Astrophysics (SPICA) is planned to be the next space astronomy mission observing in the infrared. The mission is planned to be launched in 2017 and will feature a 3.5 m telescope cooled to < 5 K through the use of mechanical coolers. These coolers will also cool the focal plane instruments thus avoiding the use of consumables and giving the mission a long lifetime. SPICA's large, cold aperture will provide a two order of magnitude sensitivity advantage over current far infrared facilities (> 30 microns wavelength). We describe the scientific advances that will be made possible by this large increase in sensitivity and give details of the mission, spacecraft and focal plane conceptual design.
-
SPICA JOINT EUROPEAN/JAPANESE WORKSHOP 2009年SPICA coronagraph will be operating from 3.5 to 27 micron and primarily aims at directly imaging extra-solar planets of nearby stars. A strong limitation of the coronagraph for the 3.5 m telescope is its angular resolution which allows planet detectability farther than a few AUs at best. Color Differential Astrometry (CDA) is a spectrophotometric method which would push the detection range to very close-in planets and up to a few AUs, thus nicely complementing the imaging coronagraph. We present the method and show how it can be implemented within the host coronagraph without major impacts on its optical setup. We give preliminary estimates of its sensitivity according to different extra-solar planetary systems configurations. Critical instrumental requirements are discussed, especially regarding detector gain stability.
-
ASTRONOMY & ASTROPHYSICS 494(1) 157-178 2009年1月Context. Massive young stellar objects (MYSO) are surrounded by massive dusty envelopes, whose physical structure and geometry are determined by the star formation process.Aims. Our principal aim is to establish the density structure of MYSO envelopes on scales of similar to 1000 AU. This constitutes an increase of a factor similar to 10 in angular resolution compared to similar studies performed in the (sub) mm.Methods. We have obtained diffraction-limited (0.6 '') 24.5 mu m images (field of view of 40 '' x 30 '') of 14 well-known massive star formation regions with the COMICS instrument mounted on the 8.2 m Subaru telescope. We construct azimuthally averaged intensity profiles of the resolved MYSO envelopes and build spectral energy distributions (SEDs) from archival data and the COMICS 24.5 mu m flux density. The SEDs range from near-infrared to millimeter wavelengths. Self-consistent 1-D radiative transfer models described by a density dependence of the form n(r)proportional to r(-p) are used to simultaneously compare the intensity profiles and SEDs to model predictions.Results. The images reveal the presence of discrete MYSO sources which are resolved on arcsecond scales, and, to first-order, the observed emission is circular on the sky. For many sources, the spherical models are capable of satisfactorily reproducing the 24.5 mu m intensity profile, the 24.5 mu m flux density, the 9.7 mu m silicate absorption feature, and the submm emission. They are described by density distributions with p = 1.0 +/- 0.25. Such distributions are shallower than those found on larger scales probed with single-dish (sub) mm studies. Other sources have density laws that are shallower/steeper than p = 1.0 and there is evidence that these are viewed near edge-on or near face-on respectively. In these cases spherical models fail to provide good fits to the data. The images also reveal a diffuse component tracing somewhat larger scale structures, particularly visible in the regions S 140, AFGL 2136, IRAS 20126+4104, Mon R2, and CepA.Conclusions. We find a flattening of the MYSO density law going from scales probed with single-dish submm observations down to scales of similar to 1000 AU probed with the observations presented here. We propose that this may be evidence of rotational support of the envelope. This finding will be explored further in a future paper using 2-D axisymmetric radiative transfer models.
-
SPICA JOINT EUROPEAN/JAPANESE WORKSHOP 2009年We present the SPICA Coronagraph Instrument (SCI) for the direct imaging and spectroscopy of exo-planets. The SPICA mission gives us a unique opportunity for high-contrast observations because of the large telescope aperture, the simple pupil shape, and the capability for infrared observations from space. The primary target of SCI is Jovian exo-planets. Using the spectroscopy mode of SCI, we will try the detection and the characterization of mid-infrared line features of the atmosphere of exo-planets. The specifications, performance and the design of the instrument are shown. The main wavelengths and the contrast required for the observations are 3.5-27 mu m, and 10(-6), respectively. We also show the progress of the development of key technology to realize SCI. Laboratory demonstration of the principle of coronagraph, realistic design and fabrication of masks, and the development of cryogenic active optics have been carried out, or are successfully ongoing. We are preparing a cryogenic chamber for the tests of the whole infrared coronagraph. A potentially important by-product of the instrument, transit monitoring for characterization of exo-planets, is also described. We expect that SCI will provide drastic progress in the understanding of various planetary systems and will be a unique capability in the SPICA era.
-
EXOPLANETS AND DISKS: THEIR FORMATION AND DIVERSITY 1158 89-+ 2009年As a result of IRAS observations, main-sequence stars that have circumstellar debris disks and thus show infrared excess have been discovered. Since debris disks are thought to be the final stage of planet formation, it is very important to investigate the properties and evolution of debris disks statistically. Especially, mid-infrared observations become a key method for planet formation study because mid-infrared excess traces the thermal emission from debris dust in planet-forming regions. We are carrying on an unbiased survey of debris disk candidates that show mid-infrared excess by using the AKARI/ARC mid-infrared all-sky survey data. So far, we have identified seven new debris disk candidates that show large 18 gm excess. Here, we present the initial results of the debris disk survey.
-
AKARI, A LIGHT TO ILLUMINATE THE MISTY UNIVERSE 418 109-+ 2009年Following the IRAS observations, many main-sequence stars that have circumstellar debris disks have been discovered through their infrared excesses. Since debris disks are thought trace the final stages of planet formation, it is very important to statistically investigate the properties and evolution of debris disks. Observations at mid-infrared wavelengths are important for planet formation studies because mid-IR excesses trace the thermal emission from debris dust in their planet forming regions. We are carrying on an unbiased survey of debris disk candidates showing mid-infrared excesses by using the AKARI/IRC mid-infrared all-sky survey data. So far, we have identified 7 new debris disk candidates that show large 18 mu m excess. Here, we present the initial results of the debris disk survey.
-
EXOPLANETS AND DISKS: THEIR FORMATION AND DIVERSITY 1158 127-+ 2009年AKARI All-sky Survey observations were carried out in the mid- to far-infrared spectral region with six photometric bands during the cryogenic mission phase of AKARI from May 8, 2006 to August 26, 2007. This paper reports the mid-infrared part of the AKARI all-sky survey. It was carried out with two mid-infrared broad bands centered at 9 and 18 gm. More than 90 percent of entire sky was observed by both bands during this period. The 5 sigma sensitivities for point sources are about 50 and 120 mJy, respectively. The spatial resolution is better than 10 '' at both bands. The AKARI mid-infrared survey achieved a deeper sensitivity and a finer spatial resolution than the previous IRAS survey. the AKARI mid-infrared survey has the sensitivity to detect a debris disk of beta Pic at a distance of 100 pc and several new debris disk candidates have already been discovered at 18 mu m in a preliminary study, separately discussed by Fujiwara et al. (in this volume). More debris disk candidates are expected to be found in further investigations, which will make a significant impact on the statistical study of debris disks.
-
AKARI, A LIGHT TO ILLUMINATE THE MISTY UNIVERSE 418 9-+ 2009年AKARI is the first Japanese astronomical infrared satellite mission orbiting around the Earth in a sun-synchronous polar orbit at the altitude of 700 km. 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 sigma 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.
-
EXOPLANETS AND DISKS: THEIR FORMATION AND DIVERSITY 1158 387-+ 2009年We describe the development of the image-stabilized telescope for project "Tera-GATE". This telescope can move the secondary mirror and cancel the image motion that arises from the gondola attitude error. We also report on the feedback system for the image stabilization and give an image quality estimation for the telescope.
-
SPICA JOINT EUROPEAN/JAPANESE WORKSHOP 2009年Mid-infrared spectroscopic capabilities, conceptual design, and estimated performances are described. We have low resolution spectroscopic capability as part of the wide field camera, medium resolution spectroscopic capability with image slicer based IFU, and high resolution spectroscopic capability based on immersion grating. Estimated noise equivalent flux for a point source with medium resolution is 150 mu Jy / 700 mu Jy for 10 to 19 mu m / 19 to 35 mu m respectively.
-
EXOPLANETS AND DISKS: THEIR FORMATION AND DIVERSITY 1158 395-+ 2009年We are developing a new infrared camera - MAX38 (Mid-infrared Astronomical eXplorer) - for ground-based mid-infrared (8-38 microns) observations. This spectral region will be very important for the study of planetary disks. The MAX38 will be attached on the University of Tokyo Atacama 1.0-meter telescope, which is the world's highest infrared telescope, at the summit of Co. Chajnantor (altitude 5,640 meters), in Chile's Atacama Desert. Thanks to the high altitude and dry weather condition of the site we can access the 30-micron wavelength region from ground-based telescopes for the first time.
-
AKARI, A LIGHT TO ILLUMINATE THE MISTY UNIVERSE 418 85-+ 2009年We report the results of imaging spectroscopic observations of four giant Galactic star-forming regions with Fourier Transform Spectrometer (FTS) onboard AKARI. We obtained [O III] 88 mu m and [C II] 158 mu m line intensity maps for all the regions: G3.270-0.101, G333.6-0.2, NGC 3603, and M17. In G3.270-0.101, we obtained high spatial resolution of the [O III] 88 mu m line emission maps and the far-infrared continuum map for the first time. In G333.6-0.2, we found a local [O III] 88 mu m emission peak, which indicates the presence of an excitation source. We suggest that the [O III] 88 mu m emission locates the excitation sources better than the radio continuum emission does. We discuss the structure of the ISM and a possible embedded excitation source from these far-infrared line and mid-infrared continuum emission maps.
-
AKARI, A LIGHT TO ILLUMINATE THE MISTY UNIVERSE 418 415-+ 2009年The formation of massive stars is not yet well understood. One of the problems is that massive stars form in clusters at relatively large distances, and it is difficult to resolve individual massive YSOs. Here we report our project of cataloguing massive star forming regions with AKARI's All-Sky Survey data.
-
EXOPLANETS AND DISKS: THEIR FORMATION AND DIVERSITY 1158 153-+ 2009年A series of emission bands in the mid-infrared, mainly at 3.3, 6.2, 7.6-7.8, 8.6 and 11.2 mu m, have been ubiquitously observed in various astrophysical environments. They are originally termed unidentified infrared (UIR) bands and many previous studies based on laboratory experiments and theoretical quantum chemical calculations have lead us to the general consensus that the carriers of these features are carbonaceous materials, including polycyclic aromatic hydrocarbons (PAHs). The relative band strengths, the profiles and the peak positions of these features are expected to vary according to the different physical conditions of the carriers. Recent observational studies have revealed the variations in the spectral properties of the UIR bands among sources with different stellar spectral types. In this proceedings we plan to give a brief introduction of our latest observational studies on the properties and the spatial distribution of the UIR bands in several objects, including both the early-type (O5--O6) and the late-type (K2) stars based on observations with Cooled Mid-Infrared Camera and Spectrometer (COMICS) on board Subaru telescope.
-
AKARI, A LIGHT TO ILLUMINATE THE MISTY UNIVERSE 418 419-+ 2009年We present deep and wide-field (10' x 10') NIR and MIR 4-band images of star-forming regions with the AKARI/IRC. We conducted observations of about 200 fields as the ATLAS in Phase 1 which cover various nearby star forming regions with stellar clusters and IR nebulae. We will statistically discuss about the distribution of young stars and their luminosity (mass) functions including young brown dwarfs.
-
EXOPLANETS AND DISKS: THEIR FORMATION AND DIVERSITY 1158 165-+ 2009年We are now searching for new T Tauri Stars (TTSs) over the whole sky on the basis of the AKARI All-Sky Survey data. As a part of our project, this study searched 285 TTSs over a 2,000-square-degree area of the Taurus-Auriga star-forming region. Our sample sources were selected from the Roentgen Satellite (ROSAT) all-sky survey and also from the previously known TTSs with infrared (IR) excess emission for comparison. Our preliminary search has succeeded in detecting 72 TTSs; 31 of 72 are newly detected with good quality.
-
SPICA JOINT EUROPEAN/JAPANESE WORKSHOP 2009年SPICA will provide the best sensitivity and image quality than ever at 5-210 mu m. This will revolutionize our understanding of exoplanets, protoplanetary disks, debris disks, and Solar system small bodies. This paper summarizes such key sciences with SPICA discussed so far among the Japanese SPICA Science Working Group, stressing on the planetary formation, and exoplanet detection and characterization.
-
SPICA JOINT EUROPEAN/JAPANESE WORKSHOP 2009年Mid-InfRAred Camera w/wo LEns (MIRACLE) is the focal plane instrument designed for wide field imaging (6' x 6') and low-resolution spectroscopic observations (R = 100) over a wide spectral range in the mid-infrared wavelength (5-38 mu m). Thanks to the SPICA's cooled telescope, MIRACLE has a better sensitivity than JWST/MIRI at wavelengths over 20 mu m and its wider FOV provides a faster mapping speed in 5-26 mu m. MIRACLE opens a new wavelength region of 26-38 mu m. Contiguous wavelength coverage is considered in the choice of the filter bands from the experiences in the Spitzer and AKARI observations. MIRACLE is equipped with a field stop wheel, which provides optimal slits in the spectroscopic mode and a wide FOV in the imaging mode. The results of a conceptual design study including sensitivity analysis are presented.
-
EXOPLANETS AND DISKS: THEIR FORMATION AND DIVERSITY 1158 399-401 2009年The far-infrared (around 1 terahertz (THz)) extrinsic photoconductor is fabricated by a LPE-grown GaAs semiconductor. This GaAs detector can detect longer wavelength photons than the stressed Ge:Ga conventionally used for astronomical infrared observation. We applied the liquid phase epitaxy to obtain a suitable purity of GaAs crystals, and the test N-GaAs photoconductor device shows spectroscopic response over a wide wavelength range of 150-300 micron. The best sample shows 30 A/W of responsivity and 10-(16) W/Hz(0.5) of NEP is expected at 295 micron of wavelength and T=1.6 K. In addition, we constructed the terahertz photometer module (TG-ZERO) using our N-GaAs photoconductors. TG-ZERO has four channel bands with N-GaAs and Ge:Ga photoconductors. The development process, the result of experiments, and the basic specifications of TG-ZERO are all reported in this paper.
-
ASTROPHYSICAL JOURNAL LETTERS 685(1) L75-L78 2008年9月We present diffraction-limited (0.6 '') 24.5 mu m Subaru COMICS images of the red supergiant mu Cep. We report the detection of a circumstellar nebula, which was not detected at shorter wavelengths. It extends to a radius of at least 6 '' in the thermal infrared. On these angular scales, the nebula is roughly spherical; in contrast, it displays a pronounced asymmetric morphology closer in. We simultaneously model the azimuthally averaged intensity profile of the nebula and the observed spectral energy distribution ( SED) using spherical dust radiative transfer models. The models indicate a constant mass-loss process over the past 1000 years, for mass-loss rates of a few x 10(-7) M(circle dot) yr(-1). This work supports the idea that at least part of the asymmetries in shells of evolved massive stars and supernovae may be due to the mass- loss process in the red supergiant phase.
MISC
155共同研究・競争的資金等の研究課題
25-
日本学術振興会 科学研究費助成事業 2014年4月 - 2018年3月
-
日本学術振興会 科学研究費助成事業 2011年4月 - 2016年3月
-
日本学術振興会 科学研究費助成事業 2007年 - 2010年
-
日本学術振興会 科学研究費助成事業 2007年 - 2008年
-
日本学術振興会 科学研究費助成事業 2004年 - 2008年
