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- 저자 : TAKAONAKAGAWA (검색결과 7 건)
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THE NEXT-GENERATION INFRARED SPACE MISSION SPICA: PROJECT UPDATES
TAKAO NAKAGAWA,Hiroshi Shibai,HIDEHIRO KANEDA,Kotaro Kohno,Hideo Matsuhara,Hiroyuki Ogawa,TAKASHI ONAKA,Peter Roelfsema,Toru Yamada 한국천문학회 2017 天文學論叢 Vol.32 No.1
We present project updates of the next-generationinfrared space mission SPICA (Space Infrared Telescope for Cosmology and Astrophysics)as of November 2015. SPICA isoptimized for mid- and far-infrared astronomy with unprecedented sensitivity, which will be achievedwith a cryogenically cooled (below 8 K), large (2.5~m) telescope. SPICA is expected to address a number ofkey questions in various fields of astrophysics, ranging from studies of the star-formation history in theuniverse 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.
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HIGHLY EXCITED CO LINES IN ACTIVE GALAXIES BOTH IN ABSORPTION AND IN EMISSION
TAKAO NAKAGAWA,Mai Shirahata,Tomonori Usuda 한국천문학회 2017 天文學論叢 Vol.32 No.1
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\textit{AKARI}. We also made follow-upCO absorption observations at higher spectral resolution (R = 5000 ~ 1000) with \textit{Subaru}. Recently, \textit{Herschel}made extensive observations of highly-excited CO lines in emission in the far-infrared. The two datasets (absorption and emission) sometimes provide us with apparently inconsistent results. One case is starburst galaxies:\textit{Subaru} observations showed low temperature of molecular gas toward the starburstNGC253, while \textit{Herschel} detected highly excited CO lines in the starburst. This suggests that warmmolecular clouds are more deeply embedded than newly formed star clusters. The other case is obscured AGNs;\textit{Herschel} detected highly excited CO lines in emission in nearby AGNs,while \textit{AKARI} and\textit{Subaru} observations showed CO absorptiononly 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 observationsas an effective tool to reveal geometry of warm molecular clouds in activegalaxies.
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THE AKARI PROJECT: LEGACY AND DATA PROCESSING STATUS
TAKAO NAKAGAWA,ISSEI YAMAMURA 한국천문학회 2017 天文學論叢 Vol.32 No.1
This paper provides an overview of the AKARI mission,which was the first Japanese satellitededicated to infrared astronomy. The \textit{AKARI} satellite was launched in 2006, and performed both an all-sky survey and pointedobservations during its 550 days in the He-cooled mission phases (Phases 1 and 2). After the He ranout, we continued near-infrared observations with mechanical cryocoolers (Phase 3). Due to a failureof its power supply, AKARI was turned off in 2011.
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INFRARED – X-RAY CONNECTION IN NEARBY ACTIVE GALACTIC NUCLEI; AKARI AND MAXI RESULTS
Naoki Isobe,TAKAONAKAGAWA,Kenichi Yano,Shunsuke Baba,SHINKI OYABU,Yoshiki Toba,Yoshihiro Ueda,Taiki Kawamuro 한국천문학회 2017 天文學論叢 Vol.32 No.1
Combining the AKARI Point Source Catalog andthe 37-month Monitor of All-sky X-ray Image (MAXI) catalog,the infrared and X-ray properties of nearby active galactic nucleiwere 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 galaxiestends to be lower for the infrared luminosity than the Seyfert I galaxies. This suggests thatthe X-ray absorption is significant in the Seyfert II galaxies. The Seyfert II galaxies seem to havea bimodal distribution of the IR color between $18~\mu$m and $90~\mu$m. Especially, a large fraction of the Seyfert II galaxiesexhibits 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.
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NEAR-INFRARED SPECTROSCOPY OF CO RO-VIBRATIONAL ABSORPTION TOWARD HEAVILY OBSCURED AGNs
MAI SHIRAHATA,TAKAONAKAGAWA,SHINKI OYABU,Tomonori Usuda 한국천문학회 2017 天文學論叢 Vol.32 No.1
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 AGNsin order to reveal physical characteristics of molecular clouds,especially focused on the CO fundamental ro-vibrational absorption around 4.7 $\rm{\mu m}$. We have made systematic moderate-resolution spectroscopic observations toward 30 representative (U)LIRGsusing the {\it 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$+$3915, UGC~05101, and IRAS~01250$+$2832, we have also made high-resolutionspectroscopic observations using the Subaru/IRCS. We have successfully detected many absorption linesup to highly excited rotational levels, and these lines are very deep and extremely broad. The derived physical conditions of molecular clouds are extreme; the gas temperatureis as high as several~100 to a 1000 K, the H$_2$ column density is larger than 10$^{22}$ $\rm{cm^{-2}}$,and the gas density is greater than 10$^7$ $\rm{cm^{-3}}$. Such hot and dense molecular cloudsmust exist around the central engine of the AGN.
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AKARI SPECTROSCOPY OF QUASARS AT 2.5 - 5 MICRON
임명신,전현성,김도형,이형목,Youichi Ohyama,김지훈,TAKAONAKAGAWA 한국천문학회 2017 天文學論叢 Vol.32 No.1
Utilizing a unique capability of {\it AKARI} that allowsdeep spectroscopy at 2.5 -- 5.0 $\mu$m, we performed a spectroscopy study of more than 200 quasarsthrough one of the {\it 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 opticalspectra 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 featuresof active galactic nuclei to gain useful information such as the dust-extinction-freeblack 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 highlightsfrom 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
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