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FIR VIEW OF DISKS OF WEAK-LINE T TAURI STARS
SATOSHI TAKITA,YASUO DOI,KO ARIMATSU,TAKAFUMI OOTSUBO 한국천문학회 2017 天文學論叢 Vol.32 No.1
We have observed $\sim$60 Weak-line T Tauri stars (WTTSs) toward the Chamaeleon star forming region using the AKARI Far-Infrared Surveyor (FIS) All-Sky maps. We could not detect any significant emission from each source even at the most sensitive WIDE-S band. Then, we have performed stacking analysis of these WTTSs using the WIDE-S band images to improve the sensitivity. However, we could not detect any significant emission in the resultant image with a noise level of 0.05~MJy~sr$^{-1}$, or 3 mJy for a point source. The three-sigma upper limit of 9~mJy leads to the disk dust mass of 0.01~M$_{\oplus}$. This result suggests that the disks around Chamaeleon WTTSs are already evolved to debris disks.
ADVANTAGES OF THE AKARI FIR ALL-SKY MAPS
YASUO DOI,SATOSHI TAKITA,TAKAFUMI OOTSUBO,KO ARIMATSU,MASAHIRO TANAKA,TAKAHIRO MORISHIMA,MITSUNOBU KAWADA,SHUJI MATSUURA,YOSHIMI KITAMURA,MAKOTO HATTORI,TAKAO NAKAGAWA,GLENN WHITE,NORIO IKEDA 한국천문학회 2017 天文學論叢 Vol.32 No.1
We present the {\it AKARI} far-infrared (FIR) all-sky maps and describe its characteristics, calibration accuracy and scientific capabilities. The {\it 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 \citep{2015PASJ...67...50D} with improved data quality that have been achieved since the last internal data release \citep{2012PKAS...27..111D}. The accuracy of the absolute intensity is $\leq10$\% 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 ofinterstellar matter with arcminute-scale spatial resolutions at the peakof dust continuum emission, enabling us to investigate large-scaledistribution of interstellar medium in great detail. The filamentarystructure 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.
THE FILAMENTARY WEB OF STAR FORMATION
White, Glenn J.,Doi, Yasuo,Komugi, Shinya,Kawada, Mitsunobu,Takita, Satoshi,Arimatsu, Ko,Ikeda, Norio,Kato, Daisuke,Kitamura, Yoshimi,Nakagawa, Takao,Ootsubo, Takafumi,Morishima, Takahiro,Hattori, Mak The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
Following the first Public Release of the AKARI Point Source catalogues, we have worked on the production of a new far-infrared All-Sky Diffuse mapping product. In this paper we report first results from the All Sky diffuse maps that will shortly be released to the community, based on analysis of data from the Far Infrared Surveyor ($65{\mu}m-160{\mu}m$) instrument. These data are likely to have a strong impact on studies of extended structures, and the diffuse ISM.
AKARI FAR-INFRARED ALL-SKY SURVEY MAPS
Doi, Yasuo,Komugi, Shinya,Kawada, Mitsunobu,Takita, Satoshi,Arimatsu, Ko,Ikeda, Norio,Kato, Daisuke,Kitamura, Yoshimi,Nakagawa, Takao,Ootsubo, Takafumi,Morishima, Takahiro,Hattori, Makoto,Tanaka, Masa The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
Far-infrared observations provide crucial data for the investigation and characterisation of the properties of dusty material in the Interstellar Medium (ISM), since most of its energy is emitted between ~ 100 and $200{\mu}m$. We present the first all-sky image from a sensitive all-sky survey using the Japanese AKARI satellite, in the wavelength range $50-180{\mu}m$. Covering > 99% of the sky in four photometric bands with four filters centred at $65{\mu}m$, $90{\mu}m$, $140{\mu}m$, and $160{\mu}m$ wavelengths, this achieved spatial resolutions from 1 to 2 arcmin and a detection limit of < 10 MJy $sr^{-1}$, with absolute and relative photometric accuracies of < 20%. All-sky images of the Galactic dust continuum emission enable astronomers to map the large-scale distribution of the diffuse ISM cirrus, to study its thermal dust temperature, emissivity and column density, and to measure the interaction of the Galactic radiation field and embedded objects with the surrounding ISM. In addition to the point source population of stars, protostars, star-forming regions, and galaxies, the high Galactic latitude sky is shown to be covered with a diffuse filamentary-web of dusty emission that traces the potential sites of high latitude star formation. We show that the temperature of dust particles in thermal equilibrium with the ambient interstellar radiation field can be estimated by using $90{\mu}m$, $140{\mu}m$, and $160{\mu}m$ data. The FIR AKARI full-sky maps provide a rich new data set within which astronomers can investigate the distribution of interstellar matter throughout our Galaxy, and beyond.
INTERSTELLAR DUST IN M51 FROM IRC IMAGES
Egusa, Fumi,Sakon, I.,Onaka, T.,Matsuhara, H.,Arimatsu, K.,Suzuki, T.,Wada, T.,The IRC team, The IRC team The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
We present the IRC images of M51, a pair of interacting galaxies. Given the high angular resolution (7.4") and the wide field of view (~ 10') covering almost the entire M51 system, we investigate dust properties and their connection to the spiral arm structure. We have applied image-filtering processes including the wavelet analysis to the N3 image, which traces the total stellar mass best among the IRC bands. From this filtered image, the center, arm, and interarm regions are defined. A color, or flux ratio among the MIR bands, has been measured at each pixel (3.7" in size). We find a wide variety of S7/S11 with a difference between arm and interarm regions. We also find that at some positions S11 seems to be higher than predicted by MW dust models. Estimated contributions from the stellar continuum and gas emission lines to the band are not enough to explain this discrepancy. From these results, we deduce that the PAH ionization condition and its fraction to the total dust mass in M51 are different from those in MW.