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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
Optical – near-infrared catalog for the AKARI north ecliptic pole Deep field
Oi, Nagisa,Matsuhara, Hideo,Murata, Kazumi,Goto, Tomotsugu,Wada, Takehiko,Takagi, Toshinobu,Ohyama, Youichi,Malkan, Matthew,Im, Myungshin,Shim, Hyunjin,Serjeant, Stephen,Pearson, Chris Springer-Verlag 2014 Astronomy and astrophysics Vol.566 No.-
THE 18 ㎛ LUMINOSITY FUNCTION OF GALAXIES WITH AKARI
Toba, Yoshiki,Oyabu, Shinki,Matsuhara, Hideo,Ishihara, Daisuke,Malkan, Matt,Wada, Takehiko,Ohyama, Youichi,Kataza, Hirokazu,Takita, Satoshi The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
We present the $18{\mu}m$ luminosity function (LF) of galaxies at 0.006 < z < 0.8 (the average redshift is ~ 0.04) using the AKARI mid-infrared All-Sky Survey catalogue. We have selected 243 galaxies at $18{\mu}m$ from the Sloan Digital Sky Survey (SDSS) spectroscopic region. These galaxies then have been classified into five types; Seyfert 1 galaxies (Sy1, including quasars), Seyfert 2 galaxies (Sy2), low ionization narrow emission line galaxies (LINER), galaxies that are likely to contain both star formation and Active Galactic Nuclei (AGN) activities (composites), and star forming galaxies (SF) using optical emission lines such as the line width of $H{\alpha}$ or the emission line ratios of [OIII]/$H{\beta}$ and [NII]/$H{\alpha}$. As a result of constructing the LF of Sy1 and Sy2, we found the following results; (i) the number density ratio of Sy2 to Sy1 is $1.64{\pm}0.37$, larger than the results obtained from optical LF and (ii) the fraction of Sy2 in the entire AGN population may decrease with $18{\mu}m$ luminosity. These results suggest that most of the AGNs in the local universe are obscured by dust and the torus structure probably depends on the mid-infrared luminosity.
AN EXTENSION OF A RELIABLE WAVELENGTH COVERAGE OF THE AKARI NG GRISM MODE
Shunsuke Baba,TAKAO NAKAGAWA,NAIKI ISOBE,MAI SHIRAHATA,YOUICHI OHYAMA,KENICHI YANO,CHIHIRO KOCHI 한국천문학회 2017 天文學論叢 Vol.32 No.1
The Infrared Camera onboard the \textit{AKARI} satellite carried out spectroscopic observations with a grism mode named \textit{NG}, whose wavelength coverage was 2.5--5.0~$\mu$m. We reinvestigate the current flux calibration for the \textit{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.
Yoshiki Toba,SHINKI OYABU,Hideo Matsuhara,DAISUKE ISHIHARA,Matt A. Malkan,Takehiko Wada,YOUICHI OHYAMA,Hirokazu Kataza,SATOSHI TAKITA,Chisato Yamauchi 한국천문학회 2017 天文學論叢 Vol.32 No.1
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 type2 AGN classification criteria.
THE 3.3 μm POLYCYCLIC AROMATIC HYDROCARBON EMISSION AS A STAR FORMATION RATE INDICATOR
Kim, Ji Hoon,Im, Myungshin,Lee, Hyung Mok,Lee, Myung Gyoon,Jun, Hyunsung David,Nakagawa, Takao,Matsuhara, Hideo,Wada, Takehiko,Oyabu, Shinki,Takagi, Toshinobu,Inami, Hanae,Ohyama, Youichi,Yamada, Rika IOP Publishing 2012 The Astrophysical journal Vol.760 No.2
<P>Polycyclic aromatic hydrocarbon (PAH) emission features dominate the mid-infrared spectra of star-forming galaxies and can be useful to calibrate star formation rates (SFRs) and diagnose ionized states of grains. However, the PAH 3.3 mu m feature has not been studied as much as other PAH features since it is weaker than others and resides outside of Spitzer capability. In order to detect and calibrate the 3.3 mu m PAH emission and investigate its potential as an SFR indicator, we carried out an AKARI mission program, AKARI mJy Unbiased Survey of Extragalactic Sources (AMUSES), and compared its sample with various literature samples. We obtained 2-5 mu m low-resolution spectra of 20 flux-limited galaxies with mixed spectral energy distribution classes, which yielded the detection of the 3.3 mu m PAH emission from 3 out of 20 galaxies. For the combined sample of AMUSES and literature samples, the 3.3 mu m PAH luminosities correlate with the infrared luminosities of star-forming galaxies, albeit with a large scatter (1.5 dex). The correlation appears to break down at the domain of ultraluminous infrared galaxies (ULIRGs), and the power of the 3.3 mu m PAH luminosity as a proxy for the infrared luminosity is hampered at log[L-PAH3.3 erg(-1) s(-1)] > similar to 42.0. Possible origins for this deviation in the correlation are discussed, including contributions from active galactic nuclei and strongly obscured young stellar objects, and the destruction of PAH molecules in ULIRGs.</P>