Publications of The Korean Astronomical Society (천문학논총)
The Korean Astronomical Society (KAS)
- 연3회간
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- 1225-1534(pISSN)
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- 2287-6936(eISSN)
Domain
- Earth Science(Earth/Atmosphere/Marine/Astronomy) > Astronomy
Aim & Scope
PKAS started as a second publication of the Korean Astronomical Society (KAS) in 1984, partly because the first KAS publication, the Journal of the Korean Astronomical Society (JKAS), had shifted to English-only publication. Thus, in 1986 PKAS became the sole publication which accepts astronomical and astrophysical articles either in English or Korean. Until 1998, the Journal was published once a year. Because the KAS itself was small and already operated a major journal, JKAS, the number of papers was very small. As the community grew, the volume steadily increased. The frequency of publication was increased to twice a year in 1999 and three times a year in 2000. Thanks to the increasing size of the community, especially the ancient astronomy community, as well as improvement of research environment, in 2016 PKAS became a candidate registration publication for Korean Citation Index (KCI) and in 2018 PKAS became a registration publication for KCI. PKAS is trying to increase the number of papers by inviting proceedings, review papers, and papers with specific topics such as ancient astronomy, astronomical instrumentation, research notes, etc., and by giving better service to authors.
http://www.kas.org/view/submitpaper.jsp?lang=eng KSCI KCIVolume 32 Issue 1
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Some after-dinner thoughts on the giants of infrared space astronomy. I here describe important events in infrared astronomy starting from 1964 when I started working on my PhD. Here I describe how I became involved in IRAS, Infrared Space Observatrory (ISO), Herschel, Spitzer and AKARI, together with important events that led to these great missions.
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This paper provides an overview of the AKARI mission, which was the first Japanese satellite dedicated to infrared astronomy. The AKARI satellite was launched in 2006, and performed both an all-sky survey and pointed observations during its 550 days in the He-cooled mission phases (Phases 1 and 2). After the He ran out, we continued near-infrared observations with mechanical cryocoolers (Phase 3). Due to a failure of its power supply, AKARI was turned off in 2011. The AKARI data are unique in terms of the observed wavelengths as well as the sky coverage, and provide a unique legacy resource for many astronomical studies. Since April 2013, a dedicated new team has been working to refine the AKARI data processing. The goal of this activity is to provide processed datasets for most of the AKARI observations in a Science Ready form, so that more users can utilize the AKARI data in their astronomical research. The data to be released will include revised All-Sky Point Source Catalogues, All-Sky Image Maps, as well as high-sensitivity images and spectra obtained by pointed observations. We expect that the data will be made public by in the Spring of 2016.
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Doi, Yasuo;Takita, Satoshi;Ootsubo, Takafumi;Arimatsu, Ko;Tanaka, Masahiro;Morishima, Takahiro;Kawada, Mitsunobu;Matsuura, Shuji;Kitamura, Yoshimi;Hattori, Makoto;Nakagawa, Takao;White, Glenn;Ikeda, Norio 11
We present the AKARI far-infrared (FIR) all-sky maps and describe its characteristics, calibration accuracy and scientific capabilities. The AKARI FIR survey has covered 97% of the whole sky in four photometric bands, which cover continuously 50-180 micron with band central wavelengths of 65, 90, 140, and 160 microns. The data have been publicly released in 2014 (Doi et al., 2015) with improved data quality that have been achieved since the last internal data release (Doi et al., 2012). The accuracy of the absolute intensity is${\leq}10%$ for the brighter regions. Quantitative analysis of the relative intensity accuracy and its dependence upon spatial scan numbers has been carried out. The data for the first time reveal the whole sky distribution of interstellar matter with arcminute-scale spatial resolutions at the peak of dust continuum emission, enabling us to investigate large-scale distribution of interstellar medium in great detail. The filamentary structure covering the whole sky is well traced by the all-sky maps. We describe advantages of the AKARI FIR all-sky maps for the study of interstellar matter comparing to other observational data. -
Makiuti, Sin'itirou;Yamamura, Issei;Koga, Tatsuya;Nakada, Tatsuya;AKARI team 17
The first version of the AKARI far-infrared All-Sky Bright Source Catalogue (BSC ver.1) was released to public in March 2010. It has been widely used for various astrophysical researches. We are continuing efforts to produce the next edition. The new version is expected to be improved in accuracy and reliability, as well as its volume. Many improvements to the next version are in progress. The time-line signal is being re-examined throughout the entire data processing. Correction processes for signal linearity and detector responsivity, and procedure for masking signal anomaly are revised. The source extraction process is further tuned and operating parameters will be optimized. These bring better reliability of the source detection and possibly an increase of source numbers. The position accuracy is expected to be improved. Systematic position error seen around the Galactic plane will also be corrected. We also plan to deliver the Faint Source Catalogue version 1. -
Sano, Hidetoshi;Amatsutsu, Tomoya;Kondo, Toru;Nakamichi, Keichiro;Yamagishi, Mitsuyoshi;Ishihara, Daisuke;Oyabu, Shinki;Kaneda, Hidehiro;Tachihara, Kengo;Fukui, Yasuo 21
We present a comparative study of CO and polycyclic aromatic hydrocarbon (PAH) emission toward a region including the massive star-forming regions of NGC 6334 and NGC 6357. We use the NANTEN$^{12}CO(J=1-0)$ data and the AKARI$9{\mu}m$ All-Sky diffuse map in order to evaluate the calibration accuracy of the AKARI data. We confirm that the overall CO distribution shows a good spatial correspondence with the PAH emission, and their intensities exhibit a good power-law correlation with a spatial resolution down to 4' over the region of$10^{\circ}{\times}10^{\circ}$ . We also reveal poorer correlation for small scale structures between the two quantities toward NGC 6357, due to strong UV radiation from local sources. Larger scatter in the correlation toward NGC 6357 indicates higher ionization degree and/or PAH excitation than that of NGC 6334. -
Amatsutsu, Tomoya;Ishihara, Daisuke;Kondo, Toru;Kaneda, Hidehiro;Oyabu, Shinki;Yamagishi, Mitsuyoshi;Nakamichi, Keichiro;Sano, Hidetoshi;Onaka, Takashi 25
We are creating all-sky diffuse maps from the AKARI mid-infrared survey data with the two photometric bands centered at wavelengths of 9 and$18{\mu}m$ . The AKARI mid-infrared diffuse maps achieve higher spatial resolution and higher sensitivity than the IRAS maps. In particular, the$9{\mu}m$ data are unique resources as an all-sky tracer of the emission of polycyclic aromatic hydrocarbons (PAHs). However, the original data suffer many artifacts. Thus, we have been developing correction methods. Among them, we have recently improved correction methods for the non-linearity and the reset anomaly of the detector response. These corrections successfully reduce the artifact level down to$0.1MJy\;sr^{-1}$ on average, which is essential for discussion on faint extended emission (e.g., the Galactic PAH emission). We have also made progress in the subtraction of the scattered light caused in the camera optics. We plan to release the improved diffuse maps to the public within a year. -
Nakamichi, Keichiro;Ishihara, Daisuke;Kaneda, Hidehiro;Oyabu, Shinki;Kondo, Toru;Amatsutsu, Tomoya;Sano, Hidetoshi;Onaka, Takashi 29
We plan to produce a faint source catalogue from the AKARI mid-infrared (IR) all-sky diffuse maps. In the publicly-available AKARI mid-IR point source catalogue (PSC), sources were extracted from single-scan images, and confirmed by using the other scan images. By stacking multiple scan images, we can detect fainter sources which are not listed in the PSC. We optimized the source extraction process using a$6^{\circ}{\times}6^{\circ}C$ area around the star-forming region, Cepheus B. Then, we divided the all-sky data into three seasonal images, and checked the positions and the fluxes of the detected sources on the images. As a result, our new source extraction method works well; 90% of the sources are also identified in the WISE catalogue. In this method, we obtain the detection limit twice deeper than that of the PSC. The number of sources increases by a factor of 2, as compared with the PSC. -
We have been working on data processing and calibration of AKARI/IRC images from pointed observations. As of September 2014, a data package for each pointing only contains raw data and quick-look data, so that users have to process them using the toolkit by themselves. We plan to change this situation and to provide science-ready data sets, which are easy-to-use for non-AKARI experts. For Phase 1&2, we have updated dark and flat calibrations, and also the toolkit itself to produce images more reliable and easier to use. A new data package includes fully calibrated images with WCS information. We released it for about 4000 pointings at the end of March 2015.
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Davidge, Helen;Serjeant, Stephen;Pearsonl, Chris 37
We present the first results of a new data analysis pipeline for processing extragalactic AKARI/IRC images. The main improvements of the pipeline over the standard analysis are the removal of Earth shine and image distortion correction. We present the differential number counts of the AKARI/IRC S11 filter in the IRAC validation field. The differential number counts are consistent with S11 AKARI NEP deep and$12{\mu}m$ WISE NEP number counts, and with a phenomenological backward evolution galaxy model, at brighter fluxes densities. There is a detection of fainter galaxies in the IRAC validation field. -
AKARI performed about 10,000 spectroscopic observations with the Infrared Camera (IRC) during its mission phase. These IRC observations provide unique spectroscopic data at near- and mid-infrared wavelengths for studies of the next few decades because of its high sensitivity and unique wavelength coverage. In this paper, we present the current status of the activity for improving the IRC spectroscopic data reduction process, including the toolkit and related data packages, and also discuss the goal of this project.
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Baba, Shunsuke;Nakagawa, Takao;Isobe, Naoki;Shirahata, Mai;Ohyama, Youichi;Yano, Kenichi;Kochi, Chihiro 45
The Infrared Camera onboard the AKARI satellite carried out spectroscopic observations with a grism mode named NG, whose wavelength coverage was$2.5-5.0{\mu}m$ . We reinvestigate the current flux calibration for the NG grism mode, with which calculated flux density implausibly decreases at$4.9{\mu}m$ especially for red objects due to the second-order light contamination. We perform a new spectral response calibration using blue and red standard objects simultaneously. New response curves which contain both the first-and second-order light are able to separate each contribution consistently and useful for studies of red objects such as CO ro-vibrational absorption in active galactic nuclei. -
Toth, L. Viktor;Marton, Gabor;Zahorecz, Sarolta;Balazs, Lajos G.;Nagy, Andrea 49
The point sources in the Bright Source Catalogue of the AKARI Far-Infrared Surveyor (FIS) were classified based on their FIR and mid-IR fluxes and colours into young stellar object (YSO) and extragalactic source types using a Quadratic Discriminant Analysis method (QDA) and Support Vector Machines (SVM). The reliability of the selection of YSO candidates is high, and the number of known YSO candidates were increased significantly, that we demonstrate in the case of the nearby open cluster IC348. Our results show that we can separate galactic and extragalactic AKARI point sources in the multidimensioal space of FIR fluxes and colours with high reliability, however, differentiating among the extragalactic sub-types needs further information. -
Usui, Fumihiko;Hasegawa, Sunao;Ishiguro, Masateru;Muller, Thomas G.;Ootsubo, Takafumi 55
Presently, the number of known asteroids is more than 710,000. Knowledge of size and albedo is essential in many aspects of asteroid research, such as the chemical composition and mineralogy, the size-frequency distribution of dynamical families, and the relationship between small bodies in the outer solar system or comets. Recently, based on the infrared all-sky survey data obtained by IRAS, AKARI, and WISE, the large asteroid catalogs containing size and albedo data have been constructed. In this paper, we discuss the compositional distribution in the main belt regions based on the compiled data on size, albedo, and separately obtained taxonomic type information. -
Kondo, Toru;Ishihara, Daisuke;Kaneda, Hidehiro;Oyabu, Shinki;Amatsutsu, Tomoya;Nakamichi, Keichiro;Sano, Hidetoshi;Ootsubo, Takafumi;Onaka, Takashi 59
The AKARI 9 and 18 µm diffuse maps reveal the all-sky distribution of the interstellar medium with relatively high spatial resolution of ~6". The zodiacal light is a dominant foreground component in the mid-infrared. Thus, removal of the zodiacal light is a critical issue to study low surface brightness Galactic diffuse emission. We carried out modeling of the zodiacal light based on the Kelsall model which is constructed from the COBE data. In the previous study, only a time-varying component of the zodiacal light brightness was used for determination of the model parameters. However, there remains a residual component of the zodiacal light around the ecliptic plane even after removal with the model. Therefore, instead of using a time-varying component, we use the absolute brightness of the zodiacal light and we find that the new model can better remove the residual component. As a result, the best-fit model parameters are changed from those in the previous study. We discuss the properties of the zodiacal light based on our new result. -
Ootsubo, Takafumi;Doi, Yasuo;Takita, Satoshi;Matsuura, Shuji;Kawada, Mitsunobu;Nakagawa, Takao;Arimatsu, Ko;Tanaka, Masahiro;Kondo, Toru;Ishihara, Daisuke;Usui, Fumihiko;Hattori, Makoto 63
The zodiacal light emission is the thermal emission from the interplanetary dust and the dominant diffuse radiation in the mid- to far-infrared wavelength region. Even in the far-infrared, the contribution of the zodiacal emission is not negligible at the region near the ecliptic plane. The AKARI far-infrared all-sky survey covered 97% of the whole sky in four photometric bands with band central wavelengths of 65, 90, 140, and$160{\mu}m$ . AKARI detected the small-scale structure of the zodiacal dust cloud, such as the asteroidal dust bands and the circumsolar ring, in far-infrared wavelength region. Although the most part of the zodiacal light structure in the AKARI far-infrared all-sky image can be well reproduced with the DIRBE zodiacal light model, there are discrepancies in the small-scale structures. In particular, the intensity and the ecliptic latitude of the peak position of the asteroidal dust bands cannot be reproduced precisely with the DIRBE models. The AKARI observational data during more than one year has advantages over the 10-month DIRBE data in modeling the full-sky zodiacal dust cloud. The resulting small-scale zodiacal light structure template has been used to subtract the zodiacal light from the AKARI all-sky maps. -
Ishihara, Daisuke;Takeuchi, Nami;Kondo, Toru;Kobayashi, Hiroshi;Kaneda, Hidehiro;Inutsuka, Shu-ichiro;Oyabu, Shinki;Nagayama, Takahiro;Fujiwara, Hideaki;Onaka, Takashi 67
Debris disks are circumstellar dust disks around main-sequence stars. They are important observational clues to understanding the planetary system formation. The zodiacal light is the thermal emission from the dust disk in our Solar system. For a comprehensive understanding of the nature and the evolution of dust disks around main-sequence stars, we try a comparative study of debris disks and the zodiacal light. We search for debris disks using the AKARI mid-infrared all-sky point source catalog. By applying accurate flux estimate of the photospheric emission based on the follow-up near-infrared observations with IRSF, we have improved the detection rate of debris disks. For a detailed study of the structure and grain properties in the zodiacal dust cloud, as an example of dust disks around main-sequence stars, we analyze the AKARI mid-infrared all-sky diffuse maps. As a result of the debris disks search, we found old (>1 Gyr) debris disks which have large excess emission compared to their age, which cannot be explained simply by the conventional steady-state evolution model. From the zodiacal light analysis, we find the possibility that the dust grains trapped in the Earth's resonance orbits have increased by a factor of ~3 in the past ~20 years. Combining these results, we discuss the non-steady processes in debris disks and the zodiacal light. -
Takeuchi, Nami;Ishihara, Daisuke;Kaneda, Hidehiro;Oyabu, Shinki;Kobayashi, Hiroshi;Nagayama, Takahiro;Onaka, Takashi;Fujiwara, Hideaki 73
Debris disks are important observational clues to understanding on-going planetary system formation. They are usually identified by significant mid-infrared excess on top of the photospheric emission of a central star on the basis of prediction from J-, H-, and Ks-band fluxes and the stellar model spectra. For bright stars, 2MASS near-infrared fluxes suffer large uncertainties due to the near-infrared camera saturation. Therefore we have performed follow-up observations with the IRSF 1.4 m near-infrared telescope located in South Africa to obtain accurate J-, H-, and Ks-band fluxes of the central stars. Among 754 main-sequence stars which are detected in the AKARI$18{\mu}m$ band, we have performed photometry for 325 stars with IRSF. As a result, we have successfully improved the flux accuracy of the central stars from 9.2 % to 0.5 % on average. Using this dataset, we have detected$18{\mu}m$ excess emission from 57 stars in our samples with a$3{\sigma}$ level. We find that some of them have high ratios of the excess to the photospheric emission even around very old stars, which cannot be explained by the current planet-formation theories. -
Onaka, Takashi;Mori, Tamami I.;Ohsawa, Ryou;Sakon, Itsuki;Bell, Aaron C.;Hammonds, Mark;Shimonishi, Takashi;Ishihara, Daisuke;Kaneda, Hidehiro;Okada, Yoko;Tanaka, Masahiro 77
A wide spectral coverage from near-infrared (NIR) to far-infrared (FIR) of AKARI both for imaging and spectroscopy enables us to efficiently study the emission from gas and dust in the interstellar medium (ISM). In particular, the Infrared Camera (IRC) onboard AKARI offers a unique opportunity to carry out sensitive spectroscopy in the NIR ($2-5{\mu}m$ ) for the first time from a spaceborn telescope. This spectral range contains a number of important dust bands and gas lines, such as the aromatic and aliphatic emission bands at 3.3 and$3.4-3.5{\mu}m$ ,$H_2O$ and$CO_2$ ices at 3.0 and$4.3{\mu}m$ , CO,$H_2$ , and H I gas emission lines. In this paper we concentrate on the aromatic and aliphatic emission and ice absorption features. The balance between dust supply and destruction suggests significant dust processing taking place as well as dust formation in the ISM. Detailed analysis of the aromatic and aliphatic bands of AKARI observations for a number of H ii regions and H ii region-like objects suggests processing of carbonaceous dust in the ISM. The ice formation process can also be studied with IRC NIR spectroscopy efficiently. In this review, dust processing in the ISM divulged by recent analysis of AKARI data is discussed. -
Shimonishi, T.;Kato, D.;Ita, Y.;Onaka, T.;AKARI/IRC LMC team 83
We conducted an unbiased near- to mid-infrared imaging and spectroscopic survey of the Large Magellanic Cloud (LMC) as a part of the AKARI Mission Program "Large-area Survey of the LMC" (LSLMC, PI: T. Onaka). An area of about 10 square degrees of the LMC was observed by five photometric bands (3.2, 7, 11, 15, and$24{\mu}m$ ) and a low-resolution slitless prism ($2-5{\mu}m$ , R ~20) equipped with AKARI /IRC. We constructed and publicly released photometric and spectroscopic catalogues of point sources in the LMC based on the survey data. The catalogues provide a large number of near-infrared spectral data, coupled with complementary broadband photometric data. Combined use of the present AKARI LSLMC catalogues with other infrared point source catalogues of the LMC possesses scientific potential that can be applied to various astronomical studies. -
Ohsawa, R.;Onaka, O.;Sakon, I.;Mori, T. I.;Kaneda, H.;Matsuura, M. 87
Polycyclic aromatic hydrocarbons (PAHs) are considered to be carriers of the unidentified infrared bands, which are ubiquitously observed in the Universe. PAHs are mainly formed around evolved carbon-rich stars and injected into interstellar space. Planetary nebulae (PNe), a late stage of low- and intermediate stellar mass evolution, are suitable objects to investigate the formation and evolution of PAHs. The shortest PAH feature is located in$3.3{\mu}m$ , which is important to examine the excitation and size distribution of PAHs. While the number of samples had been limited before, the high sensitivity of AKARI /IRC has drastically increased the number of samples. We obtained the$2-5{\mu}m$ spectra of Galactic PNe with AKARI /IRC and compiled a near-infrared spectral catalog, containing 73 PNe. We investigate the detection rate and the evolution of the PAH features. The characteristics of the catalog are illustrated and the origin of the evolution of the PAH features is discussed. -
Hammonds, Mark;Mori, Tamami;Usui, Fumihiko;Onaka, Takashi 93
The existence of polycyclic aromatic hydrocarbons (PAHs) astronomically is well accepted, but the specific molecular forms observed remain uncertain. To better understand the molecular structures which may be present along a given sightline, the$3.0-3.6{\mu}m$ region is modelled with careful consideration given to the underlying sub-features arising from specific structures within emitting molecules. -
Bell, Aaron C.;Onaka, Takashi;Doi, Yasuo;Sakon, Itsuki;Usui, Fumihiko;Sakon, Itsuki;Ishihara, Daisuke;Kaneda, Hidehiro;Giard, Martin;Wu, Ronin;Ohsawa, Ryou;Mori-Ito, Tamami;Hammonds, Mark;Lee, Ho-Gyu 97
Our understanding of dust emission, interaction, and evolution, is evolving. In recent years, electric dipole emission by spinning dust has been suggested to explain the anomalous microwave excess (AME), appearing between 10 and 90 Ghz. The observed frequencies suggest that spinning grains should be on the order of 10nm in size, hinting at polycyclic aromatic hydrocarbon molecules (PAHs). We present data from the AKARI/Infrared Camera (IRC) due to its high sensitivity to the PAH bands. By inspecting the IRC data for a few AME regions, we find a preliminary indication that regions well-fitted by a spinning-dust model have a higher$9{\mu}m$ than$18{\mu}m$ intensity vs. non-spinning-dust regions. Ongoing efforts to improve the analysis by using DustEM and including data from the AKARI Far Infrared Surveyor (FIS), IRAS, and Planck High Frequency Instrument (HFI) are described. -
Sakon, Itsuki;Onaka, Takashi;Usui, Fumihiko;Shimamoto, Sayaka;Ohsawa, Ryou;Wada, Takehiko;Matsuhara, Hideo;Arai, Akira 101
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$2.5{\mu}m$ to$5{\mu}m$ 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. -
Mori, Tamami I.;Onaka, Takashi;Sakon, Itsuki;Ohsawa, Ryou;Kaneda, Hidehiro;Yamagishi, Mitsuyoshi;Okada, Yoko;Tanaka, Masahiro;Shimonishi, Takashi 105
We present results of AKARI/IRC near-infrared (NIR) slit-spectroscopy ($2.5-5.0{\mu}m$ , R ~ 100) of Galactic sources, focusing on ice absorption features. We investigate the abundance of$H_2O$ and$CO_2$ ices and other ice species (CO and XCN ices) along lines of sight towards Galactic H$\small{II}$ regions, massive YSOs, and infrared diffuse sources. Even among those different kinds of astronomical objects, the abundance ratio of$CO_2$ to$H_2O$ ices does not vary significantly, suggesting that the pathway to$CO_2$ ice formation driven by UV irradiation is not effective at least among the present targets. -
Shimamoto, Sayaka;Sakon, Itsuki;Onaka, Takashi;Usui, Fumihiko;Ootsubo, Takafumi;Doi, Yasuo;Ohsawa, Ryou;Ishihara, Daisuke 109
We detected bright mid- to far-infrared emission from the helium nova V445 Puppis in the AKARI all-sky survey data taken in 2006. Assuming an optically thin condition, we decomposed the spectral energy distribution (SED) of V445 Puppis in October 2006 by model fitting and found that the SED can be explained by a combination of cold amorphous carbon (125 K and the mass of$4.5^{+6.6}_{-2.7}{\times}10^{-4}M_{\odot}$ ) and warm amorphous carbon (250 K and the mass of$1.8^{+1.0}_{-0.5}{\times}10^{-5}M_{\odot}$ ). Assuming that the former is pre-existing dust formed in the past nova outbursts and the latter is newly formed dust in December 2000's nova wind, this result suggests that the amount of dust formed around V445 Puppis in a single outburst is larger than$10^{-5}M_{\odot}$ , which is larger than those in any other classical novae ever reported. -
Toth, L. Viktor;Doi, Yasuo;Zahorecz, Sarolta;Agas, Marton;Balazs, Lajos G.;Forro, Adrienn;Racz, Istvan I. 113
A significant number of the parameters of a gamma-ray burst (GRB) and its host galaxy are calculated from the afterglow. There are various methods obtaining extinction values for the necessary correction for galactic foreground. These are: galaxy counts, from HI 21 cm surveys, from spectroscopic measurements and colors of nearby Galactic stars, or using extinction maps calculated from infrared surveys towards the GRB. We demonstrate that AKARI Far-Infrared Surveyor sky surface brightness maps are useful uncovering the fine structure of the galactic foreground of GRBs. Galactic cirrus structures of a number of GRBs are calculated with a 2 arcminute resolution, and the results are compared to that of other methods. -
Ward-Thompson, D.;Pattle, K.;Kirk, J.M.;Andre, P.;Di Francesco, J. 117
We show Akari data, Herschel data and data from the SCUBA2 camera on JCMT, of molecular clouds. We focus on pre-stellar cores within the clouds. We present Akari data of the L1147-1157 ring in Cepheus and show how the data indicate that the cores are being externally heated. We present SCUBA2 and Herschel data of the Ophiuchus region and show how the environment is also affecting core evolution in this region. We discuss the effects of the magnetic field in the Lupus I region, and how this lends support to a model for the formation and evolution of cores in filamentary molecular clouds. -
Hattori, Yasuki;Kaneda, Hidehiro;Ishihara, Daisuke;Yamagishi, Mitsuyoshi;Kondo, Toru;Sano, Hidetoshi 123
We present our AKARI study of massive star forming regions where a large-scale cloud-cloud collision possibly contributes to massive star formation. Our targets are Spitzer bubbles, which consist of two types of bubbles, closed and broken ones; the latter is a candidate of the objects created by cloud-cloud collisions. We performed mid- and far-infrared surface photometry toward Spitzer bubbles to obtain the relationship between the total infrared luminosity,$L_{IR}$ , and the bubble radius, R. As a result, we find that$L_{IR}$ is roughly proportional to$R^{\beta}$ where${\beta}=2.1{\pm}0.4$ . Broken bubbles tend to have larger radii than closed bubbles for the same$L_{IR}$ . -
Takita, Satoshi;Doi, Yasuo;Arimatsu, Ko;Ootsubo, Takafumi;AKARI Team 127
We have observed ~60 Weak-line T Tauri stars (WTTSs) toward the Chamaeleon star forming region using the AKARI Far-Infrared Surveyor (FIS) All-Sky maps. We could not detect any significant emission from each source even at the most sensitive WIDE-S band. Then, we have performed stacking analysis of these WTTSs using the WIDE-S band images to improve the sensitivity. However, we could not detect any significant emission in the resultant image with a noise level of$0.05MJy\;sr^{-1}$ , or 3 mJy for a point source. The three-sigma upper limit of 9 mJy leads to the disk dust mass of$0.01M_{\oplus}$ . This result suggests that the disks around Chamaeleon WTTSs are already evolved to debris disks. -
Sorahana, Satoko;Suzuki, Takeru K.;Yamamura, Issei 131
We present the latest results from the Mission Program NIRLT (PI: I.Yamamura), the near-infrared spectroscopy of brown dwarfs using the AKARI/IRC grism mode with the spectral resolution of ~ 120. The near-infrared spectra in the wavelength range between 2.5 and$5.0{\mu}m$ are especially important to study the brown dwarf atmospheres because of the presence of major molecular bands, including$CH_4$ at$3.3{\mu}m$ ,$CO_2$ at$4.2{\mu}m$ , CO at$4.6{\mu}m$ , and$H_2O$ around$2.7{\mu}m$ . We observed 27 sources, and obtained 16 good spectra. Our model fitting reveals deviations between theoretical model and observed spectra in this wavelength range, which may be attributed to the physical condition of the upper atmosphere. The deviations indicate additional heating, which we hypothesize to be due to chromospheric activity. We test this effect by modifying the brown dwarf atmosphere model to artificially increase the temperature of the upper atmosphere, and compare the revised model with observed spectra of early- to mid-L type objects with$H{\alpha}$ emission. We find that the chemical structure of the atmosphere changes dramatically, and the heating model spectra of early-type brown dwarfs can be considerably improved to match the observed spectra. Our result suggests that chromospheric activity is essential to understand early-type brown dwarf atmospheres. -
Kaneda, Hidehiro;Kokusho, Takuma;Yamada, Rika;Ishihara, Daisuke;Oyabu, Shinki;Kondo, Toru;Yamagishi, Mitsuyoshi;Yasuda, Akiko;Onaka, Takashi;Suzuki, Toyoaki 135
We have performed systematic studies of the properties of dust in various environments of nearby galaxies with AKARI. The unique capabilities of AKARI, such as near-infrared (near-IR) spectroscopy combined with all-sky coverage in the mid- and far-IR, enable us to study processing of dust, particularly carbonaceous grains includings polycyclic aromatic hydrocarbons (PAHs), for unbiased samples of nearby galaxies. In this paper, we first review our recent results on individual galaxies, highlighting the uniqueness of AKARI data for studies of nearby galaxies. Then we present results of our systematic studies on nearby starburst and early-type galaxies. From the former study based on the near-IR spectroscopy and mid-IR all-sky survey data, we find that the properties of PAHs change systematically from IR galaxies to ultraluminous IR galaxies, depending on the IR luminosity of a galaxy or galaxy population. From the latter study based on the mid- and far-IR all-sky survey data, we find that there is a global correlation between the amounts of dust and old stars in early-type galaxies, giving an observational constraint on the origin of the dust. -
Yamagishi, Mitsuyoshi;Kaneda, Hidehiro;Oyabu, Shinki;Ishihara, Daisuke;Onaka, Takashi;Shimonishi, Takashi;Suzuki, Toyoaki 141
We study$CO_2/H_2O$ ice abundance ratios in nearby galaxies using AKARI near-infrared slit spectroscopy. Past studies of the ices intensively examined$CO_2/H_2O$ ratios mainly in our Galaxy, and found that there were considerable variations in the$CO_2/H_2O$ ratios from object to object. The cause of the variations is, however, still under debate. As a result of the analysis of our sample that includes 1031 regions in 158 galaxies, the$CO_2/H_2O$ ratios are in a range of 0.05-0.30. In the dataset, we find that the$CO_2/H_2O$ ratios positively correlate with the$Br{\alpha}/PAH$ $3.3{\mu}m$ ratios which reflect the massive star formation activity. Furthermore, we find that the$CO_2/H_2O$ ratios positively correlate with the specific star formation rates of the galaxies where the ices are detected, that reflect the evolutionary stage of a galaxy. These results suggest that the$CO_2/H_2O$ ratios are enhanced in active star-forming regions and young galaxies. -
Since the launch of the Herschel Space Observatory, our understanding about the photo-dissociation regions (PDR) has taken a step forward. In the bandwidth of the Fourier Transform Spectrometer (FTS) of the Spectral and Photometric Imaging REceiver (SPIRE) on board Herschel, ten CO rotational transitions, including J = 4 - 3 to J = 13 - 12, and three fine structure lines, including [
$C{\small{I}}$ ] 609, [$C{\small{I}}$ ] 370, and [$N{\small{II}}$ ]$205{\mu}m$ , are covered. I present our findings from the FTS observations at the nuclear region of M83, based on the spatially resolved physical parameters derived from the CO spectral line energy distribution (SLED) map and the comparisons with the dust properties and star-formation tracers. This article discusses (1) the potential of using [$N{\small{II}$ ] 205 and [$C{\small{I}}$ ]$370{\mu}m$ as star-formation tracers; (2) the excitation mechanisms of warm CO in the nuclear region of M83. -
Kokusho, Takuma;Kaneda, Hidehiro;Kondo, Toru;Oyabu, Shinki;Yamagishi, Mitsuyoshi;Murata, Katsuhiro 151
Early-type galaxies (ETGs) are generally dominated by old low-mass stars, which are not very productive of dust, and hot interstellar plasmas, which are very destructive of dust. Thus ETGs provide harsh environments for survival of dust. It has been found that some ETGs contain a large amount of dust, and yet its supply mechanism is not understood well. We present the result of a systematic study of dust in ETGs with the AKARI mid- and far-infrared all-sky surveys. From the AKARI result and the Ks band data obtained by ground-based telescopes, we find that there is a global correlation between the dust mass and stellar luminosity. We also compare the AKARI all-sky survey result with the CO data to discuss origins of dust in ETGs. -
Oyabu, Shinki;Kaneda, Hidehiro;Izuhara, Masaya;Tomita, Keisuke;Ishihara, Daisuke;Kawara, Kimiaki;Matsuoka, Yoshiki 157
The dusty torus of Active Galactic Nuclei (AGNs) is one of the important components for the unification theory of AGNs. The geometry and properties of the dusty torus are key factors in understanding the nature of AGNs as well as the formation and evolution of AGNs. However, they are still under discussion. Infrared observation is useful for understanding the dusty torus as thermal emission from hot dust with the dust sublimation temperature (~ 1500 K) has been observed in the infrared. We have analyzed infrared spectroscopic data of low-redshift and high-redshift quasars, which are luminous AGNs. For the low-redshift quasars, we constructed the spectral energy distributions (SEDs) with AKARI near-infrared and Spitzer mid-infrared spectra and decomposed the SEDs into a power-law component from the nuclei, silicate features, and blackbody components with different temperatures from the dusty torus. From the decomposition, the temperature of the innermost dusty torus shows the range between 900-2000 K. For the high-redshift quasars, AKARI traced rest-frame optical and near-infrared spectra of AGNs. Combining with WISE data, we have found that the temperature of the innermost dusty torus in high redshift quasars is lower than that in typical quasars. The hydrogen$H{\alpha}$ emission line from the braod emission line region in the quasars also shows narrow full width at half maximum of$3000-4000km\;s^{-1}$ . These results indicate that the dusty torus and the broad emission line region are more extended than those of typical quasars. -
Im, Myungshin;Jun, Hyunsung;Kim, Dohyeong;Lee, Hyung Mok;Ohyama, Youichi;Kim, Ji Hoon;Nakagawa, Takao;QSONG Team 163
Utilizing a unique capability of AKARI that allows deep spectroscopy at$2.5-5.0{\mu}m$ , we performed a spectroscopy study of more than 200 quasars through one of the AKARI mission programs, QSONG (Quasar Spectroscopic Observation with NIR Grism). QSONG targeted 155 high redshift (3.3 < z < 6.42) quasars and 90 low redshift active galactic nuclei (0.002 < z < 0.48). In order to provide black hole mass estimates based on the rest-frame optical spectra, the high redshift part of QSONG is designed to detect the$H{\alpha}$ line and the rest-frame optical spectra of quasars at z > 3.3. The low redshift part of QSONG is geared to uncover the rest-frame$2.5-5.0{\mu}m$ spectral features of active galactic nuclei to gain useful information such as the dust-extinction-free black hole mass estimators based on the Brackett lines and the temperatures of the hot dust torus. We outline the program strategy, and present some of the scientific highlights from QSONG, including the detection of the$H{\alpha}$ line from a quasar at z > 4.5 which indicates a rigorous growth of black holes in the early universe, and the$Br{\beta}$ -based black hole mass estimators and the hot dust temperatures (~ 1100 K) of low redshift AGNs. -
Shirahata, Mai;Nakagawa, Takao;Oyabu, Shinki;Usuda, Tomonori 169
We provide a new physical insight on the hot molecular clouds near the nucleus of the obscured AGNs. We performed near-infrared spectroscopic observations of heavily obscured AGNs in order to reveal physical characteristics of molecular clouds, especially focused on the CO fundamental ro-vibrational absorption around$4.7{\mu}m$ . We have made systematic moderate-resolution spectroscopic observations toward 30 representative (U)LIRGs using the AKARI/IRC, and some of the ULIRGs showed the strong CO absorption feature. For three bright (U)LIRGs that show a steep red continuum with the deep CO absorption feature, IRAS 08572+3915, UGC 05101, and IRAS 01250+2832, we have also made high-resolution spectroscopic observations using the Subaru/IRCS. We have successfully detected many absorption lines up to highly excited rotational levels, and these lines are very deep and extremely broad. The derived physical conditions of molecular clouds are extreme; the gas temperature is as high as several 100 to a 1000 K, the$H_2$ column density is larger than$10^{22}cm^{-2}$ , and the gas density is greater than$10^7cm^{-3}$ . Such hot and dense molecular clouds must exist around the central engine of the AGN. -
Nakagawa, Takao;Shirahata, Mai;Usuda, Tomonori 175
In order to reveal physical conditions of molecular gas in active galaxies (active galaxies mean both starbursts and AGNs in this paper), we carried out systematic observations (R = 19 ~ 120) of CO fundamental band at$4.7{\mu}m$ in absorption with AKARI. We also made follow-up CO absorption observations at higher spectral resolution (R = 5000 ~ 1000) with Subaru. Recently, Herschel made extensive observations of highly-excited CO lines in emission in the far-infrared. The two data sets (absorption and emission) sometimes provide us with apparently inconsistent results. One case is starburst galaxies: Subaru observations showed low temperature of molecular gas toward the starburst NGC 253, while Herschel detected highly excited CO lines in the starburst. This suggests that warm molecular clouds are more deeply embedded than newly formed star clusters. The other case is obscured AGNs; Herschel detected highly excited CO lines in emission in nearby AGNs, while AKARI and Subaru observations showed CO absorption only in some of the obscured AGNs. This could reflect the difference of nature of molecular tori in these AGNs. We propose the combination of the absorption and emission observations as an effective tool to reveal geometry of warm molecular clouds in active galaxies. -
AKARI and the subsequent Herschel Space Observatory have yielded tremendous advancement in our knowledge of the infrared-submillimeter properties of active galaxies and active galactic nuclei, AGN. This short review describes some highlights. Active galaxies are found to do what they are supposed to do: build up their stellar bodies while building up their central black holes.
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Isobe, Naoki;Nakagawa, Takao;Yano, Kenichi;Baba, Shunsuke;Oyabu, Shinki;Toba, Yoshiki;Ueda, Yoshihiro;Kawamuro, Taiki 185
Combining the AKARI Point Source Catalog and the 37-month Monitor of All-sky X-ray Image (MAXI) catalog, the infrared and X-ray properties of nearby active galactic nuclei were investigated. The 37-month MAXI catalog tabulates 100 nearby Seyfert galaxies, 73 of which are categorized into Seyfert I galaxies. Among these Seyfert galaxies, 69 ones were found to have an AKARI infrared counterpart. For the Seyfert I galaxies in this sample, a well-known correlation was found between the infrared and X-ray luminosities. However, the observed X-ray luminosity of the Seyfert II galaxies tends to be lower for the infrared luminosity than the Seyfert I galaxies. This suggests that the X-ray absorption is significant in the Seyfert II galaxies. The Seyfert II galaxies seem to have a bimodal distribution of the IR color between$18{\mu}m$ and$90{\mu}m$ . Especially, a large fraction of the Seyfert II galaxies exhibits a redder IR color than the Seyfert I galaxies. A possible origin of the redder IR color is briefly discussed, in relation to the star formation activity in the host galaxy, and to the X-ray absorption. -
Yano, Kenichi;Nakagawa, Takao;Isobe, Naoki;Shirahata, Mai 189
We performed systematic observations of the H$\small{I}$ $Br{\alpha}$ line ($4.05{\mu}m$ ) in 51 nearby (z<0.3) ultraluminous infrared galaxies (ULIRGs), using AKARI near-infrared spectroscopy. The$Br{\alpha}$ line is predicted to be the brightest among the H${\small{I}}$ recombination lines in ULIRGs with visual extinction higher than 15 mag. We detected the$Br{\alpha}$ line in 33 ULIRGs. In these galaxies, the relative contribution of starburst to the total infrared luminosity ($L_{IR}$ ) is estimated on the basis of the ratio of the$Br{\alpha}$ line luminosity ($L_{Br{\alpha}}$ ) to$L_{IR}$ . The mean$L_{Br{\alpha}}/L_{IR}$ ratio in LINERs or Seyferts is significantly lower (~50%) than that in H$\small{II}$ galaxies. This result indicates that active galactic nuclei contribute significantly (~50%) to$L_{IR}$ in LINERs, as well as Seyferts. We also estimate the absolute contribution of starburst to$L_{IR}$ using the ratio of star formation rates (SFRs) derived from$L_{Br{\alpha}}$ ($SFR_{Br{\alpha}}$ ) and those needed to explain$L_{IR}$ ($SFR_{IR}$ ). The mean$SFR_{Br{\alpha}}/SFR_{IR}$ ratio is only 0.33 even in H$\small{II}$ galaxies, where starburst is supposed to dominate the luminosity. We attribute this apparently low$SFR_{Br{\alpha}}/SFR_{IR}$ ratio to the absorption of ionizing photons by dust within H$\small{II}$ regions. -
Toba, Yoshiki;Oyabu, Shinki;Matsuhara, Hideo;Ishihara, Daisuke;Malkan, Matt A.;Wada, Takehiko;Ohyama, Youichi;Kataza, Hirokazu;Takita, Satoshi;Yamauchi, Chisato 193
We demonstrate the luminosity dependence of the covering factor (CF) of active galactic nuclei (AGNs), based on AKARI mid-infrared all-sky survey catalog. Combining the AKARI with Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 243 galaxies at$9{\mu}m$ and 255 galaxies at$18{\mu}m$ . We then identified 64 AGNs at$9{\mu}m$ and 105 AGNs at$18{\mu}m$ by their optical emission lines. Following that, we estimated the CF as the fraction of type 2 AGN in all AGNs. We found that the CF decreased with increasing$18{\mu}m$ luminosity, regardless of the choice of type 2 AGN classification criteria. -
Castro, Angel;Miyaji, Takamitsu;Shirahata, Mai;Ichikawa, Kohei;Oyabu, Shinki;Clark, David;Imanishi, Masatoshi;Nakagawa, Takao;Ueda, Yoshihiro 197
Using the InfraRed Camera (IRC) on board the infrared astronomical satellite AKARI we study the${3.3{\mu}m}$ polycyclic aromatic hydrocarbon (PAH) feature and its connection to active galactic nucleus (AGN) properties for a sample of 54 hard X-ray selected bright AGN, including both Seyfert 1 and Seyfert 2 type objects. The sample is selected from the 9-month Swift/BAT survey in the 14-195 keV band and all of the sources have known neutral hydrogen column densities ($N_H$ ). The${3.3{\mu}m}$ PAH luminosity ($L_{3.3{\mu}m}$ ) is used as a proxy for star-formation (SF) activity and hard X-ray luminosity ($L_{14-195keV}$ ) as an indicator of the AGN power. We explore for possible difference of SF activity between type 1 (un-absorbed) and type 2 (absorbed) AGN. We use several statistical analyses taking the upper-limits of the PAH lines into account utilizing survival analysis methods. The results of our log($L_{14-195keV}$ ) versus log($L_{3.3{\mu}m}$ ) regression shows a positive correlation and the slope for the type 1/unobscured AGN is steeper than that of type 2/obscured AGN at a$3{\sigma}$ level. Also our analysis shows that the circum-nuclear SF is more enhanced in type 2/absorbed AGN than type 1/un-absorbed AGN for low$L_{14-195keV}$ luminosity/low Eddington ratio AGN, while there is no significant dependence of SF activity on the AGN type in the high$L_{14-195keV}$ luminosities/Eddington ratios. -
Karouzos, Marios;Im, Myungshin;Trichas, Markos;Goto, Tomogotsu;Malkan, Matthew;Ruiz, Angel;Jeon, Yiseul;Kim, Ji Hoon;Lee, Hyung Mok;Kim, Seong Jin;Oi, Nagisa;Matsuhara, Hideo;Takagi, Toshinobu;Murata, Kazumi;Wada, Takehiko;Wada, Kensuke;Shim, Hyunjin;Hanami, Hitoshi;Serjeant, Stephen;White, Glenn;Pearson, Chris;Ohyama, Youichi 201
There exists strong evidence supporting the co-evolution of central supermassive black holes and their host galaxies; however it is still under debate how such a relation comes about and whether it is relevant for all or only a subset of galaxies. An important mechanism connecting AGN to their host galaxies is AGN feedback, potentially heating up or even expelling gas from galaxies. AGN feedback may hence be responsible for the eventual quenching of star formation and halting of galaxy growth. A rich multi-wavelength dataset ranging from the X-ray regime (Chandra), to far-IR (Herschel), and radio (WSRT) is available for the North Ecliptic Pole field, most notably surveyed by the AKARI infrared space telescope, covering a total area on the sky of 5.4 sq. degrees. We investigate the star formation properties and possible signatures of radio feedback mechanisms in the host galaxies of 237 radio sources below redshift z = 2 and at a radio 1.4 GHz flux density limit of 0.1 mJy. Using broadband SED modelling, the nuclear and host galaxy components of these sources are studied simultaneously as a function of their radio luminosity. Here we present results concerning the AGN content of the radio sources in this field, while also offering evidence showcasing a link between AGN activity and host galaxy star formation. In particular, we show results supporting a maintenance type of feedback from powerful radio-jets. -
Denis, Burgarella;Mederic, Boquien;Veronique, Buat;Laure, Ciesla;Yannick, Rhoelly 205
Modelling and fitting the spectral energy distribution (SED) of galaxies or regions of galaxies is one of the most useful methods available to the astronomer nowadays. By modelling the SEDs and comparing the models to the observations, we can collect important information on the physical processes at play in the formation and evolution of galaxies. The models allow to follow the evolution of the galaxies from their formation on. The versatility of code is crucial because of the diversity of galaxies. The analysis is only relevant and useful if the models can correctly reproduce this diversity now and across (as best as possible) all redshifts. On the other hand, the code needs to run fast to compare several million or tens of millions of models and to select the best (on a probabilistic basis) one that best resembles the observations. With this important point in mind, it seems logical that we should efficiently make use of the computer power available to the average astronomer. For instance, it seems difficult, today, to model and fit SEDs without a parallelized code. We present the new Python version of CIGALE SED fitting code and its characteristics. CIGALE comes in two main flavours: CIGALE Classic to fit SEDs and CIGALE Model to create spectra and SEDs of galaxies at all redshifts. The latest can potentially be used in conjunction with galaxy evolution models of galaxy formation and evolution such as semi-analytic ones. -
Kochi, Chihiro;Nakagawa, Takao;Isobe, Naoki;Shirahata, Mai;Yano, Kenichi;Baba, Shunsuke 209
We performed Principle Component Analysis (PCA) over 264 galaxies in the IRAS Revised Bright Galaxy Sample (Sanders et al., 2003) using 12, 25, 60 and$100{\mu}m$ flux data observed by IRAS and 9, 18, 65, 90 and$140{\mu}m$ flux data observed by AKARI. We found that (i)the first principle component was largely contributed by infrared to visible flux ratio, (ii)the second principal component was largely contributed by the flux ratio between IRAS and AKARI, (iii)the third principle component was largely contributed by infrared colors. -
Matsuhara, H.;Wada, T.;Oi, N.;Takagi, T.;Nakagawa, T.;Murata, K.;Goto, T.;Oyabu, S.;Takeuchi, T.T.;Malek, K.;Solarz, A.;Ohyama, Y.;Miyaji, T.;Krumpe, M.;Lee, H.M.;Im, M.;Serjeant, S.;Pearson, C.P.;White, G.J.;Malkan, M.A.;Hanami, H.;Ishigaki, T.;Burgarella, D.;Buat, V.;Pollo, A. 213
The recent updates of the North Ecliptic Pole deep ($0.5deg^2$ , NEP-Deep) multi-wavelength survey covering from X-ray to radio-wave is presented. The NEP-Deep provides us with several thousands of$15{\mu}m$ or$18{\mu}m$ selected galaxies, which is the largest sample ever made at these wavelengths. A continuous filter coverage in the mid-infrared wavelength (7, 9, 11, 15, 18, and 24 µm) is unique and vital to diagnose the contributions from starbursts and AGNs in the galaxies out to z=2. The new goal of the project is to resolve the nature of the cosmic star formation history at the violent epoch (e.g. z=1-2), and to find a clue to understand its decline from z=1 to present universe by utilizing the unique power of the multiwavelength survey. The progress in this context is briefly mentioned. -
Pearson, Chris;Cheale, Ryan;Serjeant, Stephen;Matsuhara, Hideo;White, Glenn J.;Burgarella, Denis;Valtchanov, Ivan;Altieri, Bruno;Clements, David L.;Hopwood, Ros 219
The preliminary data reduction, analysis and first results from the Herschel survey of the AKARI NEP field are presented. Herschel SPIRE observations of the NEP-Wide region and PACS observations of the NEP-Deep region have yielded galaxy catalogues of 4000 and 900 sources respectively down to flux density levels of approximately 15 mJy at 100-250 microns. Source counts produced from these catalogues reach cosmologically significant depths tracing the evolutionary upturn and turnover in the source counts. The source counts are in agreement with other large area surveys carried out with Herschel bridging the gap between the shallow and deep Herschel surveys. -
Goto, Tomotsugu;Toba, Yoshiki;Utsumi, Yousuke;Oi, Nagisa;Takagi, Toshinobu;Malkan, Matt;Ohayma, Youichi;Murata, Kazumi;Price, Paul;Karouzos, Marios;Matsuhara, Hideo;Nakagawa, Takao;Wada, Takehiko;Serjeant, Steve;Burgarella, Denis;Buat, Veronique;Takada, Masahiro;Miyazaki, Satoshi;Oguri, Masamune;Miyaji, Takamitsu;Oyabu, Shinki;White, Glenn;Takeuchi, Tsutomu;Inami, Hanae;Perason, Chris;Malek, Katarzyna;Marchetti, Lucia;Lee, HyungMoK;Im, Myung;Kim, Seong Jin;Koptelova, Ekaterina;Chao, Dani;Wu, Yi-Han;AKARI NEP Survey team;AKARIAll Sky Survey Team 225
The extragalactic background suggests half the energy generated by stars was reprocessed into the infrared (IR) by dust. At z~1.3, 90% of star formation is obscured by dust. To fully understand the cosmic star formation history, it is critical to investigate infrared emission. AKARI has made deep mid-IR observation using its continuous 9-band filters in the NEP field ($5.4deg^2$ ), using ~10% of the entire pointed observations available throughout its lifetime. However, there remain 11,000 AKARI infrared sources undetected with the previous CFHT/Megacam imaging (r ~25.9ABmag). Redshift and IR luminosity of these sources are unknown. These sources may contribute significantly to the cosmic star-formation rate density (CSFRD). For example, if they all lie at 1< z <2, the CSFRD will be twice as high at the epoch. We are carrying out deep imaging of the NEP field in 5 broad bands (g, r, i, z, and y) using Hyper Suprime-Camera (HSC), which has 1.5 deg field of view in diameter on Subaru 8m telescope. This will provide photometric redshift information, and thereby IR luminosity for the previously-undetected 11,000 faint AKARI IR sources. Combined with AKARI's mid-IR AGN/SF diagnosis, and accurate midIR luminosity measurement, this will allow a complete census of cosmic star-formation/AGN accretion history obscured by dust. -
White, Glenn J.;Soto, Laia Barrufet de;Pearson, Chris;Serjeant, Stephen;Lim, Tanya;Matsuhara, Hideo;Sirothia, S.K.;Pal, S.;Karouzos, Marios;AKARI-NEP Team 231
We have imaged the AKARI Deep Field with the GMRT radio telescope at 610 MHz, detecting 1224 radio components, which are optically identified with 455 optical galaxies having a mean r' magnitude brighter of 22.5 (to a completeness limit of 25.4 mag), and an average redshift ~ 0.8. -
Miyaji, T.;Krumpe, M.;Brunner, H.;Ishigaki, T.;Hanami, H.;Markowitz, A.;Takagi, T.;Goto, T.;Malkan, M.A.;Matsuhara, H.;Pearson, C.;Ueda, Y.;Wada, T. 235
The AKARI NEP Deep Field Survey is an international multiwavelength survey over$0.4deg^2$ of the sky. This is the deepest survey made by the InfraRed Camera (IRC) of the infrared astronomical satellite AKARI with 9 filters continuously covering the$2-25{\mu}m$ range, including three filters in the Spitzer gap between the IRAC and MIPS coverages. This enabled us to make sensitive MIR detection of AGN candidates at z~ 1, based on hot dust emission in the AGN torus. It is also efficient in detecting highly obscured Compton-thick AGN population. In this article, we report the first results of X-ray observations on this field. The field was covered by 15 overlapping Chandra ACIS-I observations with a total exposure of ~300 ks, detecting${\approx}450$ X-ray sources. We utilize rest-frame stacking analysis of the MIR AGN candidates that are not detected individually. Our preliminary analysis shows a marginal detection of the rest-frame stacked Fe$k{\alpha}$ line from our strong Compton-thick candidates. -
Marchetti, L.;Feltre, A.;Berta, S.;Baronchelli, I.;Serjeant, S.;Vaccari, M.;Bulgarella, D.;Karouzos, M.;Murata, K.;Oi, N.;Pearson, C.;Rodighiero, G.;Segdwick, C.;White, G.J. 239
How does the presence of an AGN influence the total SFR estimates of galaxies and change their distribution with respect to the Galaxy Main Sequence? To contribute to solving this question, we study a sample of 1133 sources detected in the North Ecliptic Pole field (NEP) by AKARI and Herschel. We create a multi-wavelength dataset for these galaxies and we fit their multi-wavelength Spectral Energy Distribution (SED) using the whole spectral regime (from 0.1 to$500{\mu}m$ ). We perform the fit using three procedures: LePhare and two optimised codes for identifying AGN tracers from the SED analysis. In this work we present an overview of the comparison between the estimates of the Infrared bolometric luminosities (between 8 and$1000{\mu}m$ ) and the AGN fractions obtained exploiting these different procedures. In particular, by estimating the AGN contribution in four different wavelength ranges ($5-40{\mu}m$ ,$10-20{\mu}m$ ,$20-40{\mu}m$ and$8-1000{\mu}m$ ) we show how the presence of an AGN affects the PAH emission by suppressing the ratio$\frac{L_{8{\mu}m}}{L_{4.5{\mu}m}}$ as a function of the considered wavelength range. -
Oi, Nagisa;Matsuhara, Hideo;Pearson, Chris;Buat, Veronique;Burgarella, Denis;Malkan, Matt;Miyaji, Takamitsu;AKARI-NEP team 245
We selected 47 DOGs at z ~ 1.5 using optical R (or r'), AKARI$18{\mu}m$ , and$24{\mu}m$ color in the AKARI North Ecliptic Pole (NEP) Deep survey field. Using the colors among 3, 4, 7, and 9µm, we classified them into 3 groups; bump DOGs (23 sources), power-law DOGs (16 sources), and unknown DOGs (8 sources). We built spectral energy distributions (SEDs) with optical to far-infrared photometric data and investigated their properties using SED fitting method. We found that AGN activity such as a AGN contribution to the infrared luminosity and a Chandra detection rate for bump and power-law DOGs are significantly different, while stellar component properties like a stellar mass and a star-formation rate are similar to each other. A specific star-formation rate range of power-law DOGs is slightly higher than that of bump DOGs with wide overlap. Herschel/PACS detection rates are almost the same between bump and power-law DOGs. On the other hand SPIRE detection rates show large differences between bump and power-law DOGs. These results might be explained by differences in dust temperatures. Both groups of DOGs host hot and/or warm dust (~ 50 Kelvin), and many bump DOGs contain cooler dust (${\leq}30$ Kelvin). -
Submillimetre and millimetre-wave surveys with Herschel and the South Pole Telescope have revolutionised the discovery of strong gravitational lenses. Their follow-ups have been greatly facilitated by the multi-wavelength supplementary data in the survey fields. The forthcoming Euclid optical/near-infrared space telescope will also detect strong gravitational lenses in large numbers, and orbital constraints are likely to require placing its deep survey at the North Ecliptic Pole (the natural deep field for a wide class of ground-based and space-based observatories including AKARI, JWST and SPICA). In this paper I review the current status of the multi-wavelength survey coverage in the NEP, and discuss the prospects for the detection of strong gravitational lenses in forthcoming or proposed facilities such as Euclid, FIRSPEX and SPICA.
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Buat, V.;Oi, N.;Burgarella, D.;Malek, K.;Matsuhara, H.;Murata, K.;Serjeant, S.;Takeuchi, T.T.;Malkan, M.;Pearson, C.;Wada, T. 257
We built a$8{\mu}m$ selected sample of galaxies in the NEP-AKARI field by defining 4 redshift bins with the four AKARI bands at 11, 15, 18 and 24 microns (0.15 < z < 0.49, 0.75 < z < 1.34, 1.34 < z < 1.7 and 1.7 < z < 2.05). Our sample contains 4079 sources, 599 are securely detected with Herschel/PACS. Also adding ultraviolet (UV) data from GALEX, we fit the spectral energy distributions using the physically motivated code CIGALE to extract the star formation rate, stellar mass, dust attenuation and the AGN contribution to the total infrared luminosity ($L_{IR}$ ). We discuss the impact of the adopted attenuation curve and that of the wavelength coverage to estimate these physical parameters. We focus on galaxies with a luminosity close the characteristic$L^*_{IR}$ in the different redshift bins to study the evolution with redshift of the dust attenuation in these galaxies. -
Kim, Seong Jin;Lee, Hyung Mok;Jeong, Woong-Seob;NEP team 263
We present the mid-infrared (MIR) luminosity function (LF) of local (z < 0.3) star-forming (SF) galaxies in the North Ecliptic Pole (NEP) field. This work is based on the NEP-Wide point source catalogue and the spectroscopic redshift (z) data for ~ 1700 galaxies obtained by the optical follow-up survey with MMT/Hectospec and WIYN/Hydra. The AKARI's continuous$2-24{\mu}m$ coverage and the spectroscopic redshifts enable us to determine the spectral energy distribution (SED) in the mid-infrared and derive the luminosity functions of galaxies. Our$8{\mu}m$ LF finds good agreements with the results from SWIRE field over the wide luminosity range, while showing significant difference from the NOAO deep data in the faint end. The comparison with higher-z sample shows significant luminosity evolution from z > 0.3 to local universe.$12{\mu}m$ LF also shows a clear indication of luminosity evolution. -
Barrufet, Laia;White, Glenn J.;Pearson, Chris;Serjeant, Stephen;Lim, Tanya;Matsuhara, Hideo;Oi, Nagisa;Karouzos, Marios;AKARI-NEP Team 267
We report the results of a multi-wavelength study in the North Ecliptic Pole (NEP) deep field and examine the far infrared-radio correlation (FIRC) for high and low redshift objects. We have found a correlation between the GMRT data at 610 MHz and the Herschel data at$250{\mu}m$ that has been used to define a spectral index. This spectral index shows no evolution against redshift. As a result of the study, we show a radio colour-infrared diagram that can be used as a redshift indicator. -
Soto, Laia Barrufet de;White, Glenn J.;Pearson, Chris;Serjeant, Stephen;Lim, Tanya;Matsuhara, Hideo;Oi, Nagisa;Karouzos, Marios;AKARI-NEP Team 271
The AKARI North Ecliptic Pole Deep Field is a natural location to accomplish deep extragalactic surveys. It is supported by comprehensive ancillary data extending from radio to X-ray wavelengths, which have been used to classify radio sources as radio-loud and radio-quiet objects and to create a catalogue of Active Galactic Nuclei (AGN). This has been achieved by using a radio-optical classification and colour-colour diagrams rather than the more usual way based on spectroscopy Furthermore, we explore whether this technique can be extended by using a far-Infrared (FIR) colour-colour diagram which has been used to identify 268 high redshift candidates. -
The AKARI Deep Field South (ADF-S) is a large extragalactic survey field that is covered by multiple instruments, from optical to far-IR and radio. I summarise recent results in this and related fields prompted by the release of the Herschel far-IR/submm images, including studies of cold dust in nearby galaxies, the identification of strongly lensed distant galaxies, and the use of colour selection to find candidate very high redshift sources. I conclude that the potential for significant new results from the ADF-S is very great. The addition of new wavelength bands in the future, eg. from Euclid, SKA, ALMA and elsewhere, will boost the importance of this field still further.
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Sedgwick, Chris;Serjeant, Stephen;Pearson, Chris;Matsuura, Shuji;Shirahata, Mai;Matsuhara, Hideo;Marchetti, Lucia;White, Glenn J.;Vaccari, Mattia;Baronchelli, Ivano;Rodighiero, Giulia;Hadsukade, Bunyo;Clements, David L.;Amber, Simon 281
We present a summary of our spectroscopic redshift catalogue of 404 sources in the AKARI Deep Field South (ADF-S). We have used the AAOmega spectrograph to target mid-infrared and far-infrared sources selected primarily from AKARI observations in this field for which we were able to obtain optical counterparts. Our sources with identified redshifts include 316 with$H{\alpha}$ detections at$z{\leq}0.345$ and 15 sources at z > 1 with MgII or$Ly{\alpha}$ emission lines. About 13% of our$z{\leq}0.345$ sources are dominated by active galactic nuclei (AGN) emission, although many show emission from both star formation and AGNs. The median Balmer decrement is 5.9. Ultra-luminous infrared galaxies (ULIRGs) were found only in the higher-redshift sources. Optical and near infrared data will be available shortly, enabling calibration of the line luminosities and spectral energy distribution (SED) fitting for these sources. -
We present the results of our mid-infrared (MIR) observations of distant clusters of galaxies with AKARI. The wide-field of view of IRC/AKARI (
$10^{\prime}{\times}10^{\prime}$ ) is ideally suited for studying dust-obscured star-formation (SF) activity of galaxies along the cosmic web in the distant universe. We performed a deep and wide-field$15{\mu}m$ (rest-frame${\approx}8{\mu}m$ ) imaging observation of the RXJ1716+6708 cluster (z = 0.81) with IRC. We find that$15{\mu}m$ -detected cluster member galaxies (with total infrared luminosities of$L_{IR}{\geq}10^{11}L_{\odot}$ ) are most preferentially located in the cluster outskirt regions, whilst such IR-luminous galaxies avoid the cluster centre. Our$H{\alpha}$ follow-up study of this field confirmed that a significant fraction of$15{\mu}m$ -detected cluster galaxies are heavily obscured by dust (with$AH{\alpha}$ >3 mag in extreme cases). The environment of such dusty star-burst galaxies coincides with the place where we see a sharp "break" of the colour-density relation, suggesting an important link between dust-obscured SF activity and environmental quenching. We also report the discovery of a new cluster candidate around a radio galaxy at z = 1.52 (4C 65.22), where we obtained one of the deepest IRC imaging datasets with all the nine filters at$2-24{\mu}m$ . This field will provide us with the final, excellent laboratory for studying the dust-enshrouded SF activity in galaxies along the cosmic web at the critical epoch of cluster galaxy evolution with AKARI. -
We discuss a new IRAS Faint Source Catalog galaxy redshift catalogue (RIFSCz) which incorporates data from Galex, SDSS, 2MASS, WISE, AKARI and Planck. AKARI fluxes are consistent with photometry from other far infrared and submillimetre missions provided an aperture correction is applied. Results from the Hermes-SWIRE survey in Lockman are also discussed briefly, and the strong contrast between the galaxy populations selected at 60 and
$500{\mu}m$ is summarized. -
We crossmatch AKARI all-sky survey with the Sloan Digital Sky Survey Data Release 10 (SDSS DR10) and the Final Data Release of the Two-Degree Field Galaxy Redshift Survey (2dFGRS) and identify 118 Ultraluminous Infrared Galaxies (ULIRGs) and one Hyperluminous Infrared Galaxy (HLIRG). We find 40 new ULIRGs and one new HLIRG. ULIRGs in our sample are interacting galaxies or ongoing/post mergers. This is consistent with the fact that ULIRGs are major mergers of disk galaxies. We find that compared to local star forming SDSS galaxies of similar mass, local ULIRGs have lower oxygen abundances and this is consistent with the previous studies.
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Sedgwick, Chris;Serjeant, Stephen;Pearson, Chris;Yamamura, I.;Makiuti, S.;Ikeda, N.;Fukuda, Y.;Oyabu, S.;Koga, T.;Amber, S.;White, Glenn J. 305
We have identified 22 quasars in the AKARI far-infrared all-sky Bright Source Catalogue, using a matching radius of < 10", and excluding matches which are close to foreground extended sources or cirrus. We have confirmed a relation between quasar optical luminosity and far-infrared luminosity which was found in an earlier study. In addition, we have found that the 11 sources which are at redshift z > 1 are magnified with respect to the predicted far-infrared luminosity, and consider this may be due to gravitational lensing. If confirmed, this would provide a new way to identify lenses; if not, we may have identified an interesting new population of extreme starbursting quasars. -
Properties of ULIRGs (Ultra Luminous InfraRed Galaxies) are important to understand the cosmic star formation history. To investigate their properties up to z=0.3, we search for ULIRGs identified by using the AKARI/FIS Bright Source Catalogue and the WISE All-Sky catalog. By matching the AKARI
$90{\mu}m$ catalogue with the WISE catalog, we selected 3,452 galaxies. Additionally, combined with the SDSS DR10 spectroscopic data, we selected 952 galaxies with spec-z. We then computed total infrared luminosities using SED fitting technique, and identified 31 ULIRGs, 561 LIRGs and 344 IRGs. For these galaxies, we found an indication that ULIRGs selected by AKARI change the SED shape with redshift (z = 0.1 - 0.3). -
Fujishiro, Naofumi;Hanami, Hitoshi;Ishigaki, Tsuyoshi 313
We present physical properties of$24{\mu}m$ galaxies detected by AKARI and Spitzer and their evolution between redshifts 0.4 < z < 2. Using multi-wavelength data from X-ray to radio observations in NEP Deep Field (for AKARI) and Subaru/XMM-Newton Deep Field (for Spitzer), we derive photometric redshift, stellar mass, star-formation rate (SFR), dust extinction magnitude and rest-frame luminosities/colors of the$24{\mu}m$ galaxies from photometric SED fitting. We infer the SFRs from rest-frame ultraviolet luminosity and total infrared luminosity calibrated against Herschel photometric data. For both survey fields, we obtain complete samples with stellar mass of >$10^{10}M_{\odot}$ and SFR of >$30M_{\odot}/yr$ up to z = 2. We find that specific SFRs evolves with redshift at all stellar masses in NON-power-law galaxies (non-PLGs) as star-formation dominant luminous infrared galaxies (LIRGs). The correlations between specific SFR and stellar mass in the Spitzer and AKARI galaxy samples are well consistent with trends of the main sequence galaxies. We also discuss nature of PLGs and their evolution. -
Wada, Takehiko;Egami, Eiichi;Fujishiro, Naofumi;Goto, Tomotsugu;Imanishi, Masatoshi;Inami, Hanae;Ishihara, Daisuke;Kaneda, Hidehiro;Kohno, Kotaro;Koyama, Yusei;Matsuhara, Hideo;Matsuura, Shuji;Nagao, Tohru;Ohyama, Youichi;Onaka, Takashi;Oyabu, Shinki;Pearson, Chiris;Sakon, Itsuki;Takeuchi, Tsutomu T.;Tomita, Keisuke;Yamada, Toru;Yamagishi, Mitsuhosi 317
We propose a cosmological survey to probe star formation and nuclear activity in galaxies at redshifts of z=2-4 by polycyclic aromatic hydrocarbon (PAH) features using the SPICA mid-infrared instrument (SMI) with a spectral resolution of R=20. We will cover a wavelength range of$20-36{\mu}$ that corresponds to z=2-4 for the PAH features (11.3, 7.7, and$6.2{\mu}$ ). The sensitivity will be$1{\times}10^{-19}W/m^2(5{\sigma})$ in case of a reference survey that covers 4 arcmin2 field in a one-hour observation. It corresponds to$L_{IR}=2{\times}10^{11}L_{\odot}$ at z=3 and will give us more than 10000 galaxies in a 450 hour survey. -
Kohji, Tsumura;Toshio, Matsumoto;Shuji, Matsuura;Itsuki, Sakon;Takehiko, Wada 321
We analyzed spectral data of the astrophysical diffuse emission obtained with the low-resolution spectroscopy mode on the AKARI InfraRed Camera (IRC) in the$1.8-5.3{\mu}m$ wavelength region. Advanced reduction methods specialized for slit spectroscopy of diffuse sky spectra have been developed, and a catalog of 278 spectra of the diffuse sky covering a wide range of Galactic and ecliptic latitudes was constructed. Using this catalog, two other major foreground components, the zodiacal light (ZL) and the diffuse Galactic light (DGL), were separated and subtracted by taking correlations with ZL brightness estimated by the DIRBE ZL model and with the$100{\mu}m$ dust thermal emission, respectively. The isotropic emission was interpreted as the extragalactic background light (EBL), which shows significant excess over the integrated light of galaxies at <$4{\mu}m$ . -
Seo, H.J.;Lee, H.M.;Matsumoto, T.;Jeong, W.S.;Lee, M.G.;Pyo, J. 327
We report a spatial fluctuation analysis of the sky brightness in the near-infrared from observations towards the north ecliptic pole (NEP) by AKARI at 2.4 and$3.2{\mu}m$ . As a follow up study of our previous work on the Monitor field of AKARI, we used NEP deep survey data, which covered a circular area of about 0.4 square degrees, in order to extend fluctuation analysis at angular scales up to 1000". After pre-processing, additional correction procedures were done to correct time varying components and instrumental effects such as MUXbleed. To remove resolved objects, we applied$2{\sigma}$ clipping and point spread function (PSF) subtraction. We finally obtained mosaicked images which can be used for the study of various diffuse emissions in the near-infrared sky and found that there are spatial structures in the mosaicked images using a power spectrum analysis. -
Nakagawa, Takao;Shibai, Hiroshi;Kaneda, Hidehiro;Kohno, Kotaro;Matsuhara, Hideo;Ogawa, Hiroyuki;Onaka, Takashi;Roelfsema, Peter;Yamada, Toru;SPICA Team 331
We present project updates of the next-generation infrared space mission SPICA (Space Infrared Telescope for Cosmology and Astrophysics) as of November 2015. SPICA is optimized for mid- and far-infrared astronomy with unprecedented sensitivity, which will be achieved with a cryogenically cooled (below 8 K), large (2.5 m) telescope. SPICA is expected to address a number of key questions in various fields of astrophysics, ranging from studies of the star-formation history in the universe to the formation and evolution of planetary systems. The international collaboration framework of SPICA has been revisited. SPICA under the new framework passed the Mission Definition Review by JAXA in 2015. A proposal under the new framework to ESA is being prepared. The target launch year in the new framework is 2027/28. -
This paper reviews the requirements for far-infrared astronomy in the period following the SPICA satellite in the late 2020's. We take a very long view of the state of FIR astronomy and what facilities will be required in a twenty year timeframe. We show that spatial resolution to match that of observatories operating in the optical and mid-infrared and the radio will be a necessity. Moreover this high spatial resolution must be combined with high spectral and photometric sensitivity to provide the data required to further our understanding of planetary formation mechanisms, the history of star formation through cosmic time and the feedback between active galactic nuclei and their host galaxies in controlling star formation. We review three possible conceptual mission scenarios and comment on the possibility of realising them in the coming deades.
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We present the development of a spectral dispersion device for wideband spectroscopy for which the primary scientific objective is the characterization of transiting exoplanets. The principle of the disperser is simple: a grating is fabricated on the surface of a prism. The direction of the spectral dispersion power of the prism is crossed with the grating. Thus, the prism separates the spectrum into individual orders while the grating produces a spectrum for each order. In this work, ZnS was selected as the material for the cross disperser, which was designed to cover the wavelength region,
${\lambda}=0.6-13{\mu}m$ , with a spectral resolving power,$R{\geq}50$ . A disperser was fabricated, and an evaluation of its surface was conducted. Two spectrometer designs, one adopting ZnS (${\lambda}=0.6-13{\mu}m$ ,$R{\geq}300$ ) and the other adopting CdZnTe (${\lambda}=1-23{\mu}m$ ,$R{\geq}250$ ), are presented. The spectrometers, each of which has no moving mechanical parts, consist simply of a disperser, a focusing mirror, and a detector. -
This paper reviews the legacy of the SPCIA Coronagraph Instrument (SCI) of which the primary scientific objective is the characterization of Jovian exoplanets by coronagraphic spectroscopy in the infrared. Studies on binary shaped pupil mask coronagraphs are described. Cryogenic active optics is discussed as another key technology. Then approaches to observing habitable zones in exoplanetary systems with a passively-cooled space infrared telescope are discussed. The SCI was dropped in a drastic change of the SPICA mission. However, its legacy is useful for space-borne infrared telescopes dedicated for use in exoplanetary science in the future, especially for studies of biomarkers.
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Hanaoka, Misaki;Kaneda, Hidehiro;Oyabu, Shinki;Hattori, Yasuki;Tanaka, Kotomi;Ukai, Sota;Shichi, Kazuyuki;Wada, Takehiko;Suzuki, Toyoaki;Watanabe, Kentaroh;Nagase, Koichi;Baba, Shunsuke;Kochi, Chihiro 351
To realize large-format compact array detectors covering a wide far-infrared wavelength range up to 200 µm, we have been developing Blocked-Impurity-Band (BIB) type Ge detectors with the room-temperature surface-activated wafer bonding technology provided by Mitsubishi Heavy Industries. We fabricated various types of$p^+-i$ junction devices which possessed a BIB-type structure, and evaluated their spectral response curves using a Fourier transform spectrometer. From the Hall effect measurement, we also obtained the physical characteristics of the$p^+$ layers which constituted the$p^+-i$ junction devices. The overall result of our measurement shows that the$p^+-i$ junction devices have a promising applicability as a new far-infrared detector to cover a wavelength range of$100-200{\mu}m$ . -
Nishiyama, Miho;Kaneda, Hidehiro;Ishihara, Daisuke;Oseki, Shinji;Takeuchi, Nami;Nagayama, Takahiro;Wada, Takehiko 355
For future space IR missions, such as SPICA, it is crucial to establish an experimental method for evaluating the performance of mid-IR detectors. In particular, the wavelength dependence of the sensitivity is important but difficult to be measured properly. We are now preparing a testing system for mid-IR Si:As/Si:Sb detectors on SPICA. We have designed a cryogenic optical system in which IR signal light from a pinhole is collimated, passed through an optical filter, and focused onto a detector. With this system, we can measure the photoresponse of the detector for various IR light using optical filters with different wavelength properties. We have fabricated aluminum mirrors which are adopted to minimize thermal distortion effects and evaluated the surface figure errors. The total wavefront error of the optical system is$1.3{\mu}m$ RMS, which is small enough for the target wavelengths ($20-37{\mu}m$ ) of SPICA. The point spread function measured at a room temperature is consistent with that predicted by the simulation. We report the optical performance of the system at cryogenic temperatures. -
Oseki, Shinji;Oyabu, Shinki;Ishihara, Daisuke;Enya, Keigo;Haze, Kanae;Kotani, Takayuki;Kaneda, Hidehiro;Nishiyama, Miho;Abe, Lyu;Yamamuro, Tomoyasu 359
We report our research on aluminum mirror optics for future infrared astronomical satellites. For space infrared missions, cooling the whole instrument is crucial to suppress the infrared background and detector noise. In this aspect, aluminum is appropriate for cryogenic optics, because the same material can be used for the whole structure of the instrument including optical components thanks to its excellent machinability, which helps to mitigate optical misalignment at low temperatures. We have fabricated aluminum mirrors with ultra-precision machining and measured the wave front errors (WFEs) of the mirrors with a Fizeau interferometer. Based on the power spectral densities of the WFEs, we confirmed that the surface accuracy of all the mirrors satisfied the requirements for the SPICA Coronagraph Instrument. We then integrated the mirrors into an optical system, and examined the image quality of the system with an optical laser. As a result, the total WFE is estimated to be 33 nm (rms) from the Strehl ratio. This is consistent with the WFEs estimated from the measurement of the individual mirrors. -
Yamanaka, Asa;Kaneda, Hidehiro;Yamagishi, Mitsuyoshi;Kondo, Toru;kokusho, Takuma;Tanaka, Kotomi;Hanaoka, Misaki;Nakagawa, Takao;Kawada, Mitsunobu;Isobe, Naoki;Arai, Toshiaki;Onaka, Takashi 363
The telescope to be onboard SPICA (Space Infrared Telescope for Cosmology and Astrophysics) has an aperture diameter of 2.5 m and its imaging performance is to be diffraction-limited at a wavelength of$20{\mu}m$ at the operating temperature of <8 K. Because manufacturing precise autocollimating flat mirrors (ACFs) with sizes comparable to the SPICA telescope is not technically feasible, we plan to use sub-aperture stitching interferometry through ACFs for optical testing of the telescope. We have verified the applicability of the sub-aperture stitching technique to the SPICA telescope by performing stitching experiments in a vacuum at a room temperature, using the 800-mm telescope and a 300-mm ACF. We have also developed a new method to reduce uncertainties possibly caused by cryogenic and gravitational deformations of ACFs.