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ITSUKI SAKON

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Papers by ITSUKI SAKON

Discovery of Two Infrared Objects with Strong Ice Absorption in the Akari Slitless Spectroscopic Survey of the Galactic Plane

The Astrophysical Journal

We discover two infrared objects that show deep absorption features of H 2 O, CO 2 , and CO ices ... more We discover two infrared objects that show deep absorption features of H 2 O, CO 2 , and CO ices in the AKARI/Infrared Camera (IRC) slit-less spectroscopic survey of the Galactic plane in 2.5-13 µm. Both objects are located neither in known star-forming regions nor in known dense clouds. For one of the objects, Object 1, we successfully extract a spectrum from 2.5 to 13 µm, which also shows several absorption features in 5-13 µm, including deep silicate absorption at 10 µm. For the other object, Object 2, only a spectrum from 3.1 to 5 µm is reliably extracted due to the presence of nearby overlapping objects and faint nebulosity. Both objects show warm (> 100 K) CO gas absorption in addition to the ice absorption features, suggesting that they are embedded young stellar objects (YSOs). On the other hand, both objects have spectral energy distributions (SEDs) that peak at around 5 µm and decrease towards longer wavelengths. These characteristics of the SEDs and the presence of deep absorption features cannot easily be accounted for by standard YSO models. They may be explained as background stars behind dense clouds. We discuss possible nature of the objects and implications of the present discovery.

Origins Space Telescope science drivers to design traceability

Journal of Astronomical Telescopes, Instruments, and Systems

The Origins Space Telescope (Origins) concept is designed to investigate the creation and dispers... more The Origins Space Telescope (Origins) concept is designed to investigate the creation and dispersal of elements essential to life, the formation of planetary systems, and the transport of water to habitable worlds and the atmospheres of exoplanets around nearby K-and M-dwarfs to identify potentially habitable-and even inhabited-worlds. These science priorities are aligned with NASA's three major astrophysics science goals: How does the Universe work? How did we get here? and Are we alone? We briefly describe the science case that arose from the astronomical community and the science traceability matrix for Origins. The science traceability matrix prescribes the design of Origins and demonstrates that it will address the key science questions motivated by the science case. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

MICHI: a thermal-infrared instrument for the TMT

Ground-based and Airborne Instrumentation for Astronomy VII, 2018

With the imminent launch of the JWST, the field of thermal-infrared (TIR) astronomy will enjoy a ... more With the imminent launch of the JWST, the field of thermal-infrared (TIR) astronomy will enjoy a revolution. It is easy to imagine that all areas of infrared (IR) astronomy will be greatly advanced, but perhaps impossible to conceive of the new vistas that will be opened. To allow both follow-up JWST observations and a continuance of work started on the ground-based 8m's, we continue to plan the science cases and instrument design for a TIR imager and spectrometer for early operation on the TMT. We present the current status of our science cases and the instrumentation plans, harnessing expertise across the TMT partnership. This instrument will be proposed by the MICHI team as a second-generation instrument in any upcoming calls for proposals.

AKARI Infrared Observations of the Supernova Remnant G292.0+1.8: Unveiling Circumstellar Medium and Supernova

We present the results of AKARI observations of the O-rich supernova remnant G292.0+1.8 using six... more We present the results of AKARI observations of the O-rich supernova remnant G292.0+1.8 using six IRC and four FIS bands covering 2.7-26.5 µm and 50-180 µm, respectively. The AKARI images show two prominent structures; a bright equatorial ring structure along the east-west direction and an outer elliptical shell structure surrounding the remnant. The equatorial ring structure is clumpy and incomplete with its western end opened. The outer shell is almost complete and slightly squeezed along the north-south direction. The central position of the outer shell is ∼ 1 ′ northwest from the embedded pulsar and coincides with the center of the equatorial ring structure. In the northen and southwestern regions, there is also faint emission with a sharp boundary beyond the bright

The mid-infrared imager, spectrometer, coronagraph (MISC) for the Origins Space telescope (OST)

Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave, 2018

Mid-infrared spectrometer and camera for the Origins Space Telescope

Journal of Astronomical Telescopes, Instruments, and Systems, 2021

The mid-infrared spectrometer and camera transit spectrometer (MISC-T) is one of the three baseli... more The mid-infrared spectrometer and camera transit spectrometer (MISC-T) is one of the three baseline instruments for Origins Space Telescope (Origins) and provides the capability to assess the habitability of nearby exoplanets and search for signs of life. MISC-T employs a densified pupil optical design, and HgCdTe and Si:As detector arrays. This optical design allows the instrument to be relatively insensitive to minor line-of-sight pointing drifts and telescope aberrations, and the detectors do not require a sub-Kelvin refrigerator. MISC-T has three science spectral channels that share the same field-of-view by means of beam splitters, and all channels are operated simultaneously to cover the full spectral range from 2.8 to 20 μm at once with exquisite stability and precision (<5 ppm between 2.8 to 11 μm, <20 ppm between 11 and 20 μm). A Lyot-coronagraph-based tip-tilt sensor located in the instrument fore-optics uses the light reflected by a field stop, which corresponds to 0.3% of the light from the target, to send fine pointing information to the field steering mirror in the Origins telescope. An additional MISC Wide Field Imager (WFI) is studied as an upscope option for the Origins. MISC-WFI offers a wide field imaging (3 0 × 3 0) and low-resolution spectroscopic capability with filters and gratingprisms (grisms) covering 5 to 28 μm. The imaging capability of the MISC-WFI will be used for general science objectives. The low-resolution spectroscopic capability in MISC-WFI with a resolving power R (¼ λ∕Δλ) of a few hundreds will be used to measure the mid-infrared dust features and ionic lines at z up to ∼1 in the Origins mission's Rise of Metals and Black Hole

The Peculiar Type Ib Supernova 2006jc: A WC Star Explosion

We present a theoretical model for Type Ib supernova (SN) 2006jc associated with a luminous blue ... more We present a theoretical model for Type Ib supernova (SN) 2006jc associated with a luminous blue variable (LBV)-like event. We calculate the presupernova evolution of the progenitor star, hydrodynamics and nucleosynthesis of the SN explosion, and the SN bolometric light curve (LC). The observed bolometric LC is constructed by integrating the UV, optical, near-infrared (NIR), and midinfrared (MIR) fluxes. The progenitor is assumed to be as massive as 40M⊙ on the zero-age. The star undergoes extensive mass loss to reduce its mass down to as small as 6.9M⊙, thus becoming a WC Wolf-Rayet star at the presupernova stage. The WC star model has a thick carbon-rich layer, in which amorphous carbon grains can be formed during the explosion. This could explain the brightening in the NIR flux and the observed dust feature in MIR. The typical main-sequence mass of a WC WolfRayet star and thus the progenitor of SN 2006jc is more massive than 40M⊙. We suggest that the explosions of stars more mass...

Space Project for Astrophysical and Cosmological Exploration (SPACE), an ESA stand-alone mission and a possible contribution to the Origins Space Telescope

Experimental Astronomy, 2021

We propose a new mission called Space Project for Astrophysical and Cosmological Exploration (SPA... more We propose a new mission called Space Project for Astrophysical and Cosmological Exploration (SPACE) as part of the ESA long term planning Voyage 2050 programme. SPACE will study galaxy evolution at the earliest times, with the key goals of charting the formation of the heavy elements, measuring the evolution of the galaxy luminosity function, tracing the build-up of stellar mass in galaxies over cosmic time, and finding the first super-massive black holes (SMBHs) to form. The mission will exploit a unique region of the parameter space, between the narrow ultra-deep surveys with HST and JWST, and shallow wide-field surveys such as the Roman Space Telescope and EUCLID, and should yield by far the largest sample of any current or planned mission of very high redshift galaxies at z > 10 which are sufficiently bright for detailed follow-up spectroscopy. Crucially, we propose a wide-field spectroscopic near-IR + mid-IR capability which will greatly enhance our understanding of the fir...

Evolution of Planetary Nebulae and PAH features

Proceedings of The Life Cycle of Dust in the Universe: Observations, Theory, and Laboratory Experiments — PoS(LCDU2013), 2014

Near-to mid-infrared spectra of 17 Galactic Planetary Nebulae (PNe), which show prominent C-rich ... more Near-to mid-infrared spectra of 17 Galactic Planetary Nebulae (PNe), which show prominent C-rich dust features, were obtained with the AKARI/IRC and Spitzer/IRS. Relative intensities of Polycyclic Aromatic Hydrocarbon (PAH) features were measured. The evolutionary stage of PNe is estimated by the effective temperature of the central star. The evolution of the PAH emission is investigated in terms of the evolution of the central stars. As PNe evolve, the ionization fraction of PAHs decreases, the 3.4-3.5 µm aliphatic features become stronger and the peak position of the 6.2 µm feature moves toward shorter wavelengths. Possible mechanisms for the evolution of the PAH emission are discussed.

Spectral Evolution of Novae in the Near-Infrared Based on Akari Observations

Publications of The Korean Astronomical Society, 2017

We have carried out the near-infrared spectroscopic observations of recent classical novae (e.g.,... more We have carried out the near-infrared spectroscopic observations of recent classical novae (e.g., V2468Cyg, V1280Sco) within a few years from the outburst with AKARI as a part of AKARI Open Time Observing Program for Phase 3-II "Spectral Evolution of Novae in the Near-Infrared based on AKARI Observations (Proposal ID: SENNA)". The homogeneous datasets of near-infrared spectra from 2.5 µm to 5 µm with AKARI/IRC collected in this program are useful to infer the physical conditions of the shell formed by the ejected materials, to examine the chemical properties of the ejecta gas, and to examine the properties of dust formed in the nova ejecta.

Sensitivity Estimates for the SPICA Mid-Infrared Instrument (SMI)

Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 2016

We present the latest results of the sensitivity estimate for spectrometers of the SPICA Mid-Infr... more We present the latest results of the sensitivity estimate for spectrometers of the SPICA Mid-Infrared Instrument (SMI). SMI has three spectroscopic channels; low resolution spectrometer (LRS), medium resolution spectrometer (MRS) and high resolution spectrometer (HRS). Taking account of the results of optical design of each spectrometer and the latest information of the expected performance of detector arrays, the continuum sensitivity for a point source, the continuum sensitivity for an extended source, the line sensitivity for a point source, the line sensitivity for an extended source, and the saturation limit are calculated for LRS, MRS and HRS and are provided in this paper.

Mid-infrared vibrational study of deuterium-containing PAH variants

Planetary and Space Science, 2016

Polycyclic Aromatic Hydrocarbon (PAH) molecules have been long proposed to be a major carrier of ... more Polycyclic Aromatic Hydrocarbon (PAH) molecules have been long proposed to be a major carrier of 'Unidentified Infrared' (UIR) emission bands that have been observed ubiquitously in various astrophysical environments. These molecules can potentially be an efficient reservoir of deuterium. Once the infrared properties of the deuteriumcontaining PAHs are well understood both experimentally and theoretically, the interstellar UIR bands can be used as a valuable tool to infer the cause of the deuterium depletion in the ISM. Density Functional Theory (DFT) calculations have been carried out on deuteriumcontaining ovalene variants to study the infrared properties of these molecules. These include deuterated ovalene, cationic deuterated ovalene, deuteronated ovalene and deuterated-deuteronated ovalene. We present a D/H ratio calculated from our theoretical study to compare with the observationally proposed D/H ratio.

Theoretical study of deuteronated PAHs as carriers for IR emission features in the ISM

Monthly Notices of the Royal Astronomical Society, 2015

This work proposes deuteronated PAH (DPAH +) molecules as a potential carrier of the 4.4 and 4.65... more This work proposes deuteronated PAH (DPAH +) molecules as a potential carrier of the 4.4 and 4.65 µm mid-infrared emission bands that have been observationally detected towards the Orion and M17 regions. Density Functional Theory calculations have been carried out on DPAH + molecules to see the variations in the spectral behaviour from that of a pure polycyclic aromatic hydrocarbon (PAH). DPAH + molecules show features that arise due to the stretching of the aliphatic C-D bond. Deuterated PAHs have been previously reported as carriers for such features. However, preferred conditions of ionization of PAHs in the interstellar medium (ISM) indicates the possibility of the formation of DPAH + molecules. Comparison of band positions of DPAH + s shows reasonable agreement with the observations. We report the effect of size of the DPAH + molecules on band positions and intensities. This study also reports a D/H ratio ([D/H] sc ; the ratio of C-D stretch and C-H stretch bands per [D/H] num) that is decreasing with the increasing size of DPAH + s. It is noted that large DPAH + molecules (no. of C atoms ∼50) match the D/H ratio that has been estimated from observations. This ratio offers prospects to study the deuterium abundance and depletion in the ISM.

Properties of Newly Formed Dust by SN 2006JC Based on Near- to Mid-Infrared Observation with Akari

The Astrophysical Journal, 2009

We present our latest results on near-to mid-infrared observation of SN2006jc at 200 days after t... more We present our latest results on near-to mid-infrared observation of SN2006jc at 200 days after the discovery using the Infrared Camera (IRC) on board AKARI. The near-infrared (2-5µm) spectrum of SN2006jc is obtained for the first time and is found to be well interpreted in terms of the thermal emission from amorphous carbon of 800±10K with the mass of 6.9 ± 0.5 × 10 −5 M ⊙ that was formed in the supernova ejecta. This dust mass newly formed in the ejecta of SN 2006jc is in a range similar to those obtained for other several dust forming core collapse supernovae based on recent observations (i.e., 10 −3-10 −5 M ⊙). Midinfrared photometric data with AKARI/IRC MIR-S/S7, S9W, and S11 bands have shown excess emission over the thermal emission by hot amorphous carbon of 800K. This mid-infrared excess emission is likely to be accounted for by the emission from warm amorphous carbon dust of 320±10K with the mass of 2.7 +0.7 −0.5 ×10 −3 M ⊙ rather than by the band emission of astronomical silicate and/or

FAR-INFRARED LUMINOUS SUPERNOVA REMNANT Kes 17

The Astrophysical Journal, 2011

We present the results of infrared (IR; 2.5-160 µm) observations of the supernova remnant (SNR) K... more We present the results of infrared (IR; 2.5-160 µm) observations of the supernova remnant (SNR) Kes 17 based on the data obtained with the AKARI and Spitzer satellites. We first detect bright continuum emission of its western shell in the mid-and far-IR wavebands together with its near-IR molecular line emission. We also detect hidden mid-IR emission of its southern shell after subtraction of the background emission in this region. The far-IR luminosity of the western shell is ∼ 8100 L ⊙ , which makes Kes 17 one of the few SNRs of significant far-IR emission. The fittings of the spectral energy distribution indicate the existence of two dust components: ∼ 79 K (hot) and ∼ 27 K (cold) corresponding to the dust mass of ∼ 6.2 × 10 −4 M ⊙ and ∼ 6.7 M ⊙ , respectively. We suggest that the hot component represents the dust emission of the material swept up by the SNR to its western and southern boundaries, compatible with the distribution of radio continuum emission overlapping the mid-IR emission in the western and southern shells. The existence of hot (∼ 2,000 K), shocked dense molecular gas revealed by the near-IR molecular line emission in the western shell, on the other hand, suggests that the cold dust component represents the dust emission related to the interaction between the SNR and nearby molecular gas. The excitation conditions of the molecular gas appear to be consistent with those from shocked, clumpy admixture gas of different temperatures. We discuss three possibilities for the origin of the bright far-IR emission of the cold dust in the western shell: the emission of dust in the inter-clump medium of shocked molecular clouds, the emission of dust in evaporating flows of molecular clouds engulfed by hot gas, and the emission of dust of nearby molecular clouds illuminated by radiative shocks.

Akariinfrared Observations of the Supernova Remnant G292.0+1.8: Unveiling Circumstellar Medium and Supernova Ejecta

The Astrophysical Journal, 2009

We present the results of AKARI observations of the O-rich supernova remnant G292.0+1.8 using six... more We present the results of AKARI observations of the O-rich supernova remnant G292.0+1.8 using six IRC and four FIS bands covering 2.7-26.5 µm and 50-180 µm, respectively. The AKARI images show two prominent structures; a bright equatorial ring structure along the east-west direction and an outer elliptical shell structure surrounding the remnant. The equatorial ring structure is clumpy and incomplete with its western end opened. The outer shell is almost complete and slightly squeezed along the north-south direction. The central position of the outer shell is ∼ 1 ′ northwest from the embedded pulsar and coincides with the center of the equatorial ring structure. In the northen and southwestern regions, there is also faint emission with a sharp boundary beyond the bright

AKARI Detection of the Infrared-Bright Supernova Remnant B0104Formula72.3 in the Small Magellanic Cloud

Publications of the Astronomical Society of Japan, 2007

We present a serendipitous detection of the infrared-bright supernova remnant (SNR) B0104−72.3 in... more We present a serendipitous detection of the infrared-bright supernova remnant (SNR) B0104−72.3 in the Small Magellanic Cloud by the Infrared Camera (IRC) onboard AKARI. An elongated, partially complete shell is detected in all four observed IRC bands covering 2.6-15 µm. The infrared shell surrounds radio, optical, and X-ray emission associated with the SNR and is probably a radiative SNR shell. This is the first detection of a SNR shell in this near/mid-infrared waveband in the Small Magellanic Cloud. The IRC color indicates that the infrared emission might be from shocked H 2 molecules with some possible contributions from ionic lines. We conclude that B0104−72.3 is a middle-aged SNR interacting with molecular clouds, similar to the Galactic SNR IC 443. Our results highlight the potential of AKARI IRC observations in studying SNRs, especially for diagnosing SNR shocks.

The Infrared Astronomical Mission AKARI

Publications of the Astronomical Society of Japan, 2007

AKARI, the first Japanese satellite dedicated to infrared astronomy, was launched on 2006 Februar... more 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 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.

Deep Extragalactic Surveys around the Ecliptic Poles with AKARI (ASTRO-F)

Publications of the Astronomical Society of Japan, 2006

AKARI (formerly ASTRO-F) is an infrared space telescope designed for an all-sky survey at 10-180 ... more AKARI (formerly ASTRO-F) is an infrared space telescope designed for an all-sky survey at 10-180 µm, and deep pointed surveys of selected areas at 2-180 µm. The deep pointed surveys with AKARI will significantly advance our understanding of galaxy evolution, the structure formation of the universe, the nature of buried AGNs, and the cosmic infrared background. We describe here the important characteristics of the AKARI mission, the orbit, and attitude control system, and investigate the optimum survey area based on the updated pre-flight sensitivities of AKARI, taking into account the cirrus confusion noise as well as the surface density of bright stars. The North Ecliptic Pole is concluded to be the best area for 2-26 µm deep surveys, while the low-cirrus noise regions around the South Ecliptic Pole are worth considering for 50-180 µm pointed surveys to high sensitivities limited by the galaxy confusion noise. Current observational plans concerning these pointed surveys are described in detail. Comparing these surveys with deep surveys using the Spitzer Space Telescope, the AKARI deep surveys are particularly unique in respect of their continuous wavelength coverage over the 2-26 µm range in broad-band deep imaging, and their slitless spectroscopy mode over the same wavelength range.

Concurrent Formation of Carbon and Silicate Dust in Nova V1280 Sco

The Astrophysical Journal, 2016

We present infrared multi-epoch observations of the dust forming nova V1280 Sco over ∼2000 days f... more

Discovery of Two Infrared Objects with Strong Ice Absorption in the Akari Slitless Spectroscopic Survey of the Galactic Plane

The Astrophysical Journal

We discover two infrared objects that show deep absorption features of H 2 O, CO 2 , and CO ices ... more We discover two infrared objects that show deep absorption features of H 2 O, CO 2 , and CO ices in the AKARI/Infrared Camera (IRC) slit-less spectroscopic survey of the Galactic plane in 2.5-13 µm. Both objects are located neither in known star-forming regions nor in known dense clouds. For one of the objects, Object 1, we successfully extract a spectrum from 2.5 to 13 µm, which also shows several absorption features in 5-13 µm, including deep silicate absorption at 10 µm. For the other object, Object 2, only a spectrum from 3.1 to 5 µm is reliably extracted due to the presence of nearby overlapping objects and faint nebulosity. Both objects show warm (> 100 K) CO gas absorption in addition to the ice absorption features, suggesting that they are embedded young stellar objects (YSOs). On the other hand, both objects have spectral energy distributions (SEDs) that peak at around 5 µm and decrease towards longer wavelengths. These characteristics of the SEDs and the presence of deep absorption features cannot easily be accounted for by standard YSO models. They may be explained as background stars behind dense clouds. We discuss possible nature of the objects and implications of the present discovery.

Origins Space Telescope science drivers to design traceability

Journal of Astronomical Telescopes, Instruments, and Systems

The Origins Space Telescope (Origins) concept is designed to investigate the creation and dispers... more The Origins Space Telescope (Origins) concept is designed to investigate the creation and dispersal of elements essential to life, the formation of planetary systems, and the transport of water to habitable worlds and the atmospheres of exoplanets around nearby K-and M-dwarfs to identify potentially habitable-and even inhabited-worlds. These science priorities are aligned with NASA's three major astrophysics science goals: How does the Universe work? How did we get here? and Are we alone? We briefly describe the science case that arose from the astronomical community and the science traceability matrix for Origins. The science traceability matrix prescribes the design of Origins and demonstrates that it will address the key science questions motivated by the science case. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

MICHI: a thermal-infrared instrument for the TMT

Ground-based and Airborne Instrumentation for Astronomy VII, 2018

With the imminent launch of the JWST, the field of thermal-infrared (TIR) astronomy will enjoy a ... more With the imminent launch of the JWST, the field of thermal-infrared (TIR) astronomy will enjoy a revolution. It is easy to imagine that all areas of infrared (IR) astronomy will be greatly advanced, but perhaps impossible to conceive of the new vistas that will be opened. To allow both follow-up JWST observations and a continuance of work started on the ground-based 8m's, we continue to plan the science cases and instrument design for a TIR imager and spectrometer for early operation on the TMT. We present the current status of our science cases and the instrumentation plans, harnessing expertise across the TMT partnership. This instrument will be proposed by the MICHI team as a second-generation instrument in any upcoming calls for proposals.

AKARI Infrared Observations of the Supernova Remnant G292.0+1.8: Unveiling Circumstellar Medium and Supernova

We present the results of AKARI observations of the O-rich supernova remnant G292.0+1.8 using six... more We present the results of AKARI observations of the O-rich supernova remnant G292.0+1.8 using six IRC and four FIS bands covering 2.7-26.5 µm and 50-180 µm, respectively. The AKARI images show two prominent structures; a bright equatorial ring structure along the east-west direction and an outer elliptical shell structure surrounding the remnant. The equatorial ring structure is clumpy and incomplete with its western end opened. The outer shell is almost complete and slightly squeezed along the north-south direction. The central position of the outer shell is ∼ 1 ′ northwest from the embedded pulsar and coincides with the center of the equatorial ring structure. In the northen and southwestern regions, there is also faint emission with a sharp boundary beyond the bright

The mid-infrared imager, spectrometer, coronagraph (MISC) for the Origins Space telescope (OST)

Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave, 2018

Mid-infrared spectrometer and camera for the Origins Space Telescope

Journal of Astronomical Telescopes, Instruments, and Systems, 2021

The mid-infrared spectrometer and camera transit spectrometer (MISC-T) is one of the three baseli... more The mid-infrared spectrometer and camera transit spectrometer (MISC-T) is one of the three baseline instruments for Origins Space Telescope (Origins) and provides the capability to assess the habitability of nearby exoplanets and search for signs of life. MISC-T employs a densified pupil optical design, and HgCdTe and Si:As detector arrays. This optical design allows the instrument to be relatively insensitive to minor line-of-sight pointing drifts and telescope aberrations, and the detectors do not require a sub-Kelvin refrigerator. MISC-T has three science spectral channels that share the same field-of-view by means of beam splitters, and all channels are operated simultaneously to cover the full spectral range from 2.8 to 20 μm at once with exquisite stability and precision (<5 ppm between 2.8 to 11 μm, <20 ppm between 11 and 20 μm). A Lyot-coronagraph-based tip-tilt sensor located in the instrument fore-optics uses the light reflected by a field stop, which corresponds to 0.3% of the light from the target, to send fine pointing information to the field steering mirror in the Origins telescope. An additional MISC Wide Field Imager (WFI) is studied as an upscope option for the Origins. MISC-WFI offers a wide field imaging (3 0 × 3 0) and low-resolution spectroscopic capability with filters and gratingprisms (grisms) covering 5 to 28 μm. The imaging capability of the MISC-WFI will be used for general science objectives. The low-resolution spectroscopic capability in MISC-WFI with a resolving power R (¼ λ∕Δλ) of a few hundreds will be used to measure the mid-infrared dust features and ionic lines at z up to ∼1 in the Origins mission's Rise of Metals and Black Hole

The Peculiar Type Ib Supernova 2006jc: A WC Star Explosion

We present a theoretical model for Type Ib supernova (SN) 2006jc associated with a luminous blue ... more We present a theoretical model for Type Ib supernova (SN) 2006jc associated with a luminous blue variable (LBV)-like event. We calculate the presupernova evolution of the progenitor star, hydrodynamics and nucleosynthesis of the SN explosion, and the SN bolometric light curve (LC). The observed bolometric LC is constructed by integrating the UV, optical, near-infrared (NIR), and midinfrared (MIR) fluxes. The progenitor is assumed to be as massive as 40M⊙ on the zero-age. The star undergoes extensive mass loss to reduce its mass down to as small as 6.9M⊙, thus becoming a WC Wolf-Rayet star at the presupernova stage. The WC star model has a thick carbon-rich layer, in which amorphous carbon grains can be formed during the explosion. This could explain the brightening in the NIR flux and the observed dust feature in MIR. The typical main-sequence mass of a WC WolfRayet star and thus the progenitor of SN 2006jc is more massive than 40M⊙. We suggest that the explosions of stars more mass...

Space Project for Astrophysical and Cosmological Exploration (SPACE), an ESA stand-alone mission and a possible contribution to the Origins Space Telescope

Experimental Astronomy, 2021

We propose a new mission called Space Project for Astrophysical and Cosmological Exploration (SPA... more We propose a new mission called Space Project for Astrophysical and Cosmological Exploration (SPACE) as part of the ESA long term planning Voyage 2050 programme. SPACE will study galaxy evolution at the earliest times, with the key goals of charting the formation of the heavy elements, measuring the evolution of the galaxy luminosity function, tracing the build-up of stellar mass in galaxies over cosmic time, and finding the first super-massive black holes (SMBHs) to form. The mission will exploit a unique region of the parameter space, between the narrow ultra-deep surveys with HST and JWST, and shallow wide-field surveys such as the Roman Space Telescope and EUCLID, and should yield by far the largest sample of any current or planned mission of very high redshift galaxies at z > 10 which are sufficiently bright for detailed follow-up spectroscopy. Crucially, we propose a wide-field spectroscopic near-IR + mid-IR capability which will greatly enhance our understanding of the fir...

Evolution of Planetary Nebulae and PAH features

Proceedings of The Life Cycle of Dust in the Universe: Observations, Theory, and Laboratory Experiments — PoS(LCDU2013), 2014

Near-to mid-infrared spectra of 17 Galactic Planetary Nebulae (PNe), which show prominent C-rich ... more Near-to mid-infrared spectra of 17 Galactic Planetary Nebulae (PNe), which show prominent C-rich dust features, were obtained with the AKARI/IRC and Spitzer/IRS. Relative intensities of Polycyclic Aromatic Hydrocarbon (PAH) features were measured. The evolutionary stage of PNe is estimated by the effective temperature of the central star. The evolution of the PAH emission is investigated in terms of the evolution of the central stars. As PNe evolve, the ionization fraction of PAHs decreases, the 3.4-3.5 µm aliphatic features become stronger and the peak position of the 6.2 µm feature moves toward shorter wavelengths. Possible mechanisms for the evolution of the PAH emission are discussed.

Spectral Evolution of Novae in the Near-Infrared Based on Akari Observations

Publications of The Korean Astronomical Society, 2017

We have carried out the near-infrared spectroscopic observations of recent classical novae (e.g.,... more We have carried out the near-infrared spectroscopic observations of recent classical novae (e.g., V2468Cyg, V1280Sco) within a few years from the outburst with AKARI as a part of AKARI Open Time Observing Program for Phase 3-II "Spectral Evolution of Novae in the Near-Infrared based on AKARI Observations (Proposal ID: SENNA)". The homogeneous datasets of near-infrared spectra from 2.5 µm to 5 µm with AKARI/IRC collected in this program are useful to infer the physical conditions of the shell formed by the ejected materials, to examine the chemical properties of the ejecta gas, and to examine the properties of dust formed in the nova ejecta.

Sensitivity Estimates for the SPICA Mid-Infrared Instrument (SMI)

Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 2016

We present the latest results of the sensitivity estimate for spectrometers of the SPICA Mid-Infr... more We present the latest results of the sensitivity estimate for spectrometers of the SPICA Mid-Infrared Instrument (SMI). SMI has three spectroscopic channels; low resolution spectrometer (LRS), medium resolution spectrometer (MRS) and high resolution spectrometer (HRS). Taking account of the results of optical design of each spectrometer and the latest information of the expected performance of detector arrays, the continuum sensitivity for a point source, the continuum sensitivity for an extended source, the line sensitivity for a point source, the line sensitivity for an extended source, and the saturation limit are calculated for LRS, MRS and HRS and are provided in this paper.

Mid-infrared vibrational study of deuterium-containing PAH variants

Planetary and Space Science, 2016

Polycyclic Aromatic Hydrocarbon (PAH) molecules have been long proposed to be a major carrier of ... more Polycyclic Aromatic Hydrocarbon (PAH) molecules have been long proposed to be a major carrier of 'Unidentified Infrared' (UIR) emission bands that have been observed ubiquitously in various astrophysical environments. These molecules can potentially be an efficient reservoir of deuterium. Once the infrared properties of the deuteriumcontaining PAHs are well understood both experimentally and theoretically, the interstellar UIR bands can be used as a valuable tool to infer the cause of the deuterium depletion in the ISM. Density Functional Theory (DFT) calculations have been carried out on deuteriumcontaining ovalene variants to study the infrared properties of these molecules. These include deuterated ovalene, cationic deuterated ovalene, deuteronated ovalene and deuterated-deuteronated ovalene. We present a D/H ratio calculated from our theoretical study to compare with the observationally proposed D/H ratio.

Theoretical study of deuteronated PAHs as carriers for IR emission features in the ISM

Monthly Notices of the Royal Astronomical Society, 2015

This work proposes deuteronated PAH (DPAH +) molecules as a potential carrier of the 4.4 and 4.65... more This work proposes deuteronated PAH (DPAH +) molecules as a potential carrier of the 4.4 and 4.65 µm mid-infrared emission bands that have been observationally detected towards the Orion and M17 regions. Density Functional Theory calculations have been carried out on DPAH + molecules to see the variations in the spectral behaviour from that of a pure polycyclic aromatic hydrocarbon (PAH). DPAH + molecules show features that arise due to the stretching of the aliphatic C-D bond. Deuterated PAHs have been previously reported as carriers for such features. However, preferred conditions of ionization of PAHs in the interstellar medium (ISM) indicates the possibility of the formation of DPAH + molecules. Comparison of band positions of DPAH + s shows reasonable agreement with the observations. We report the effect of size of the DPAH + molecules on band positions and intensities. This study also reports a D/H ratio ([D/H] sc ; the ratio of C-D stretch and C-H stretch bands per [D/H] num) that is decreasing with the increasing size of DPAH + s. It is noted that large DPAH + molecules (no. of C atoms ∼50) match the D/H ratio that has been estimated from observations. This ratio offers prospects to study the deuterium abundance and depletion in the ISM.

Properties of Newly Formed Dust by SN 2006JC Based on Near- to Mid-Infrared Observation with Akari

The Astrophysical Journal, 2009

We present our latest results on near-to mid-infrared observation of SN2006jc at 200 days after t... more We present our latest results on near-to mid-infrared observation of SN2006jc at 200 days after the discovery using the Infrared Camera (IRC) on board AKARI. The near-infrared (2-5µm) spectrum of SN2006jc is obtained for the first time and is found to be well interpreted in terms of the thermal emission from amorphous carbon of 800±10K with the mass of 6.9 ± 0.5 × 10 −5 M ⊙ that was formed in the supernova ejecta. This dust mass newly formed in the ejecta of SN 2006jc is in a range similar to those obtained for other several dust forming core collapse supernovae based on recent observations (i.e., 10 −3-10 −5 M ⊙). Midinfrared photometric data with AKARI/IRC MIR-S/S7, S9W, and S11 bands have shown excess emission over the thermal emission by hot amorphous carbon of 800K. This mid-infrared excess emission is likely to be accounted for by the emission from warm amorphous carbon dust of 320±10K with the mass of 2.7 +0.7 −0.5 ×10 −3 M ⊙ rather than by the band emission of astronomical silicate and/or

FAR-INFRARED LUMINOUS SUPERNOVA REMNANT Kes 17

The Astrophysical Journal, 2011

We present the results of infrared (IR; 2.5-160 µm) observations of the supernova remnant (SNR) K... more We present the results of infrared (IR; 2.5-160 µm) observations of the supernova remnant (SNR) Kes 17 based on the data obtained with the AKARI and Spitzer satellites. We first detect bright continuum emission of its western shell in the mid-and far-IR wavebands together with its near-IR molecular line emission. We also detect hidden mid-IR emission of its southern shell after subtraction of the background emission in this region. The far-IR luminosity of the western shell is ∼ 8100 L ⊙ , which makes Kes 17 one of the few SNRs of significant far-IR emission. The fittings of the spectral energy distribution indicate the existence of two dust components: ∼ 79 K (hot) and ∼ 27 K (cold) corresponding to the dust mass of ∼ 6.2 × 10 −4 M ⊙ and ∼ 6.7 M ⊙ , respectively. We suggest that the hot component represents the dust emission of the material swept up by the SNR to its western and southern boundaries, compatible with the distribution of radio continuum emission overlapping the mid-IR emission in the western and southern shells. The existence of hot (∼ 2,000 K), shocked dense molecular gas revealed by the near-IR molecular line emission in the western shell, on the other hand, suggests that the cold dust component represents the dust emission related to the interaction between the SNR and nearby molecular gas. The excitation conditions of the molecular gas appear to be consistent with those from shocked, clumpy admixture gas of different temperatures. We discuss three possibilities for the origin of the bright far-IR emission of the cold dust in the western shell: the emission of dust in the inter-clump medium of shocked molecular clouds, the emission of dust in evaporating flows of molecular clouds engulfed by hot gas, and the emission of dust of nearby molecular clouds illuminated by radiative shocks.

Akariinfrared Observations of the Supernova Remnant G292.0+1.8: Unveiling Circumstellar Medium and Supernova Ejecta

The Astrophysical Journal, 2009

We present the results of AKARI observations of the O-rich supernova remnant G292.0+1.8 using six... more We present the results of AKARI observations of the O-rich supernova remnant G292.0+1.8 using six IRC and four FIS bands covering 2.7-26.5 µm and 50-180 µm, respectively. The AKARI images show two prominent structures; a bright equatorial ring structure along the east-west direction and an outer elliptical shell structure surrounding the remnant. The equatorial ring structure is clumpy and incomplete with its western end opened. The outer shell is almost complete and slightly squeezed along the north-south direction. The central position of the outer shell is ∼ 1 ′ northwest from the embedded pulsar and coincides with the center of the equatorial ring structure. In the northen and southwestern regions, there is also faint emission with a sharp boundary beyond the bright

AKARI Detection of the Infrared-Bright Supernova Remnant B0104Formula72.3 in the Small Magellanic Cloud

Publications of the Astronomical Society of Japan, 2007

We present a serendipitous detection of the infrared-bright supernova remnant (SNR) B0104−72.3 in... more We present a serendipitous detection of the infrared-bright supernova remnant (SNR) B0104−72.3 in the Small Magellanic Cloud by the Infrared Camera (IRC) onboard AKARI. An elongated, partially complete shell is detected in all four observed IRC bands covering 2.6-15 µm. The infrared shell surrounds radio, optical, and X-ray emission associated with the SNR and is probably a radiative SNR shell. This is the first detection of a SNR shell in this near/mid-infrared waveband in the Small Magellanic Cloud. The IRC color indicates that the infrared emission might be from shocked H 2 molecules with some possible contributions from ionic lines. We conclude that B0104−72.3 is a middle-aged SNR interacting with molecular clouds, similar to the Galactic SNR IC 443. Our results highlight the potential of AKARI IRC observations in studying SNRs, especially for diagnosing SNR shocks.

The Infrared Astronomical Mission AKARI

Publications of the Astronomical Society of Japan, 2007

AKARI, the first Japanese satellite dedicated to infrared astronomy, was launched on 2006 Februar... more 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 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.

Deep Extragalactic Surveys around the Ecliptic Poles with AKARI (ASTRO-F)

Publications of the Astronomical Society of Japan, 2006

AKARI (formerly ASTRO-F) is an infrared space telescope designed for an all-sky survey at 10-180 ... more AKARI (formerly ASTRO-F) is an infrared space telescope designed for an all-sky survey at 10-180 µm, and deep pointed surveys of selected areas at 2-180 µm. The deep pointed surveys with AKARI will significantly advance our understanding of galaxy evolution, the structure formation of the universe, the nature of buried AGNs, and the cosmic infrared background. We describe here the important characteristics of the AKARI mission, the orbit, and attitude control system, and investigate the optimum survey area based on the updated pre-flight sensitivities of AKARI, taking into account the cirrus confusion noise as well as the surface density of bright stars. The North Ecliptic Pole is concluded to be the best area for 2-26 µm deep surveys, while the low-cirrus noise regions around the South Ecliptic Pole are worth considering for 50-180 µm pointed surveys to high sensitivities limited by the galaxy confusion noise. Current observational plans concerning these pointed surveys are described in detail. Comparing these surveys with deep surveys using the Spitzer Space Telescope, the AKARI deep surveys are particularly unique in respect of their continuous wavelength coverage over the 2-26 µm range in broad-band deep imaging, and their slitless spectroscopy mode over the same wavelength range.

Concurrent Formation of Carbon and Silicate Dust in Nova V1280 Sco

The Astrophysical Journal, 2016

We present infrared multi-epoch observations of the dust forming nova V1280 Sco over ∼2000 days f... more