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AKARI INFRARED OBSERVATIONS OF EMBEDDED YSOs IN THE MAGELLANIC CLOUDS
Shimonishi, T.,Onaka, T.,Kato, D.,Sakon, I.,Ita, Y.,Kawamura, A.,Kaneda, H. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
Spectroscopic studies of extragalactic YSOs have shown a great progress in the last few years. Infrared observations with AKARI made significant contributions to that progress. In this proceeding, we are going to introduce our current research on the infrared observations of ices and dust around embedded YSOs in the Magellanic Clouds.
AKARI INFRARED CAMERA SURVEY OF THE LARGE MAGELLANIC CLOUD
T. Shimonishi,D. KATO,Y. ITA,T.ONAKA 한국천문학회 2017 天文學論叢 Vol.32 No.1
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 $\sim$20) equipped with \textit{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 \textit{AKARI} LSLMC catalogues with other infrared point source catalogues of the LMC possesses scientific potential that can be applied to various astronomical studies.
Yamagishi, Mitsuyoshi,Kaneda, Hidehiro,Ishihara, Daisuke,Oyabu, Shinki,Onaka, Takashi,Shimonishi, Takashi,Suzuki, Toyoaki,Minh, Young Chol IOP Publishing 2013 ASTROPHYSICAL JOURNAL LETTERS - Vol.773 No.2
<P>With AKARI, we obtain the spatially resolved near-infrared (NIR) (2.5-5.0 mu m) spectra for the nearby starburst galaxy M 82. These spectra clearly show absorption features due to interstellar ices. Based on the spectra, we created the column density maps of H2O and CO2 ices. As a result, we find that the spatial distribution of H2O ice is significantly different from that of CO2 ice; H2O ice is widely distributed, while CO2 ice is concentrated near the galactic center. Our result reveals for the first time variations in CO2/H2O ice abundance ratio on a galactic scale, suggesting that an ice-forming interstellar environment changes within a galaxy. We discuss the cause of the spatial variations in the ice abundance ratio, utilizing spectral information on the hydrogen recombination Br alpha and Br beta lines and the polycyclic aromatic hydrocarbon 3.3 mu m emission appearing in the AKARI NIR spectra.</P>
SYSTEMATIC STUDY OF INTERSTELLAR ICES IN NEARBY GALAXIES
Yamagishi, M.,Kaneda, H.,Oyabu, S.,Ishihara, D.,Onaka, T.,Shimonishi, T.,Suzuki, T. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
The absorption features due to interstellar ices, especially $H_2O$ and $CO_2$ ices, provide us with crucial information on present and past interstellar environments, and thus the evolutionary histories of galaxies. Before AKARI, however, few detections of ices were reported for nearby galaxies. The AKARI's unique capability of near-infrared spectroscopy with high sensitivity enables us to systematically study ices in nearby galaxies. Thus we have explored many near-infrared spectra ($2.5-5{\mu}m$) of the 211 pointed observations, searching for the absorption features of ices. As a result, out of 122 nearby galaxies, we have significantly detected $H_2O$ ice from 36 galaxies and $CO_2$ ice from 9 galaxies. It is notable that the ices are detected not only in late-type galaxies but also in early-type galaxies. We find that $CO_2$ ice is more compactly distributed near the galactic center than $H_2O$ ice. Finally, we suggest that the gas density of a molecular cloud and UV radiation may be important factors to determine the abundance of ices.
STUDY OF CO2/H2O ICE ABUNDANCE RATIOS IN NEARBY GALAXIES WITH THE AKARI NEAR-INFRARED SPECTROSCOPY
MITSUYOSHI YAMAGISHI,HIDEHIRO KANEDA,SHINKI OYABU,DAISUKE ISHIHARA,TAKASHI ONAKA,TAKASHI SHIMONISHI,Toyoaki Suzuki 한국천문학회 2017 天文學論叢 Vol.32 No.1
We study $\mathrm{CO_2/H_2O}$ ice abundance ratios in nearby galaxies using $AKARI$ near-infrared slit spectroscopy. Past studies of the ices intensively examined $\mathrm{CO_2/H_2O}$ ratios mainly in our Galaxy, and found that there were considerable variations in the $\mathrm{CO_2/H_2O}$ 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 $\mathrm{CO_2/H_2O}$ ratios are in a range of 0.05--0.30. In the dataset, we find that the $\mathrm{CO_2/H_2O}$ 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 $\mathrm{CO_2/H_2O}$ 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 $\mathrm{CO_2/H_2O}$ ratios are enhanced in active star-forming regions and young galaxies.
AKARI INFRARED CAMERA SURVEY OF THE LARGE MAGELLANIC CLOUD. I. POINT-SOURCE CATALOG
Kato, Daisuke,Ita, Yoshifusa,Onaka, Takashi,Tanabé,, Toshihiko,Shimonishi, Takashi,Sakon, Itsuki,Kaneda, Hidehiro,Kawamura, Akiko,Wada, Takehiko,Usui, Fumihiko,Koo, Bon-Chul,Matsuura, Mikako,Tak American Institute of Physics 2012 The Astronomical journal Vol.144 No.6
<P>We present a near- to mid-infrared point-source catalog of five photometric bands at 3.2, 7, 11, 15, and 24 μm for a 10 deg<SUP>2</SUP> area of the Large Magellanic Cloud (LMC) obtained with the Infrared Camera on board the AKARI satellite. To cover the survey area the observations were carried out at three separate seasons from 2006 May to June, 2006 October to December, and 2007 March to July. The 10σ limiting magnitudes of the present survey are 17.9, 13.8, 12.4, 9.9, and 8.6 mag at 3.2, 7, 11, 15, and 24 μm, respectively. The photometric accuracy is estimated to be about 0.1 mag at 3.2 μm and 0.06-0.07 mag in the other bands. The position accuracy is 0<img entity='farcs' SRC='http://ej.iop.org/icons/Entities/farcs.gif' ALT='farcs' ALIGN='BOTTOM' />3 at 3.2, 7, and 11 μm and 1<img entity='farcs' SRC='http://ej.iop.org/icons/Entities/farcs.gif' ALT='farcs' ALIGN='BOTTOM' />0 at 15 and 24 μm. The sensitivities at 3.2, 7, and 24 μm are roughly comparable to those of the Spitzer SAGE LMC point-source catalog, while the AKARIcatalog provides the data at 11 and 15 μm, covering the mid-infrared spectral range contiguously. Two types of catalog are provided: a Catalog and an Archive. The Archive contains all the detected sources, while the Catalog only includes the sources that have a counterpart in the Spitzer SAGE point-source catalog. The Archive contains about 650,000, 140,000, 97,000, 43,000, and 52,000 sources at 3.2, 7, 11, 15, and 24 μm, respectively. Based on the catalog, we discuss the luminosity functions at each band, the color-color diagram, and the color-magnitude diagram using the 3.2, 7, and 11 μm band data. Stars without circumstellar envelopes, dusty C-rich and O-rich stars, young stellar objects, and background galaxies are located at distinct regions in the diagrams, suggesting that the present catalog is useful for the classification of objects toward the LMC.</P>
PROCESSING OF INTERSTELLAR MEDIUM AS DIVULGED BY AKARI
TAKASHI ONAKA,TAMAMI I. MORI,RYOU OHSAWA,ITSUKI SAKON,AARON C. BELL,MARK HAMMONDS,TAKASHI SHIMONISHI,DAISUKE ISHIHARA,HIDEHIRO KANEDA,YOKO OKADA,MASAHIRO TANAKA 한국천문학회 2017 天文學論叢 Vol.32 No.1
A wide spectral coverage from near-infrared (NIR) to far-infrared (FIR) of {\it AKARI} both for imaging and spectroscopy enablesus to efficiently study the emission from gas and dust in the interstellar medium (ISM). In particular, the Infrared Camera(IRC) onboard {\it 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 emissionbands at 3.3 and 3.4--3.5\,$\mu$m, H$_2$O and CO$_2$ ices at 3.0 and 4.3\,$\mu$m, CO, H$_2$, and \ion{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 takingplace as well as dust formation in the ISM. Detailed analysis of the aromatic and aliphatic bands of {\it AKARI} observations for a number of\ion{H}{ii} regions and \ion{H}{ii} region-like objectssuggests processing of carbonaceous dust in the ISM. The ice formation process canalso be studied with IRC NIR spectroscopy efficiently. In this review, dust processing in the ISM divulged by recentanalysis of {\it AKARI} data is discussed.
ICE ABSORPTION FEATURES IN NIR SPECTRA OF GALACTIC OBJECTS
TAMAMI I. MORI,TAKASHI ONAKA,ITSUKI SAKON,RYOU OHSAWA,HIDEHIRO KANEDA,MITSUYOSHI YAMAGISHI,YOKO OKADA,MASAHIRO TANAKA,TAKASHI SHIMONISHI 한국천문학회 2017 天文學論叢 Vol.32 No.1
We present results of AKARI/IRC near-infrared (NIR) slit-spectroscopy (2.5--5.0\,$\mu$m, $R \sim 100$) of Galactic sources,focusing on ice absorption features. We investigate the abundance of H$_2$O and CO$_2$ ices and other ice species (CO and XCN ices)along lines of sight towards Galactic \ion{H}{ii} regions, massive YSOs, and infrared diffuse sources. Even among those different kinds of astronomical objects,the abundance ratio of CO$_2$ to H$_2$O ices does not vary significantly,suggesting that the pathway to CO$_2$ ice formation driven by UV irradiation is not effectiveat least among the present targets.