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Ionized Gas Outflows in Infrared-bright Dust-obscured Galaxies Selected with<i>WISE</i>and SDSS
Toba, Yoshiki,Bae, Hyun-Jin,Nagao, Tohru,Woo, Jong-Hak,Wang, Wei-Hao,Wagner, Alexander Y.,Sun, Ai-Lei,Chang, Yu-Yen American Astronomical Society 2017 The Astrophysical journal Vol.850 No.2
<P>We present the ionized gas properties of infrared (IR)-bright dust-obscured galaxies (DOGs) that show an extreme optical/IR color, (i - [22])(AB) > 7.0, selected with the Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE). For 36 IR-bright DOGs that show [O III]lambda 5007 emission in the SDSS spectra, we performed a detailed spectral analysis to investigate their ionized gas properties. In particular, we measured the velocity offset (the velocity with respect to the systemic velocity measured from the stellar absorption lines) and the velocity dispersion of the [O III] line. We found that the derived velocity offset and dispersion of most IR-bright DOGs are larger than those of Seyfert 2 galaxies (Sy2s) at z < 0.3, meaning that the IR-bright DOGs show relatively strong outflows compared to Sy2s. This can be explained by the difference in IR luminosity contributed from active galactic nuclei, LIR (AGN), because we found that (i) L(IR ()AGN) correlates with the velocity offset and dispersion of [O III] and (ii) our IR-bright DOG sample has larger L-IR (AGN) than Sy2s. Nevertheless, the fact that about 75% IR-bright DOGs have a large (> 300 km s(-1)) velocity dispersion, which is a larger fraction compared to other AGN populations, suggests that IR-bright DOGs are good laboratories to investigate AGN feedback. The velocity offset and dispersion of [O III] and [Ne III]lambda 3869 are larger than those of [O II]lambda 3727, which indicates that the highly ionized gas tends to show stronger outflows.</P>
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.
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.
HYPER SUPRIME-CAMERA SURVEY OF THE AKARI NEP WIDE FIELD
Tomotsugu Goto,Yoshiki Toba,Yousuke Utsumi,Nagisa Oi,Toshinobu Takagi,Matt Malkan,Youichi Ohayma,Kazumi Murata,Paul Price,Marios Karouzos,Hideo Matsuhara,TAKAO NAKAGAWA,Takehiko Wada,Steve Serjeant,De 한국천문학회 2017 天文學論叢 Vol.32 No.1
The extragalactic background suggests half the energy generated by stars was reprocessed into the infrared (IR) by dust. At z$\sim$1.3, 90\% of star formation is obscured by dust. To fully understand the cosmic star formation history, it is critical to investigate infrared emission. AKARI has made deep mid-IR observation using its continuous 9-band filters in the NEP field (5.4 deg$^2$), using $\sim$10\% of the entire pointed observations available throughout its lifetime. However, there remain 11,000 AKARI infrared sources undetected with the previous CFHT/Megacam imaging ($r\sim$25.9ABmag). Redshift and IR luminosity of these sources are unknown. These sources may contribute significantly to the cosmic star-formation rate density (CSFRD). For example, if they all lie at 1$<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 mid-IR luminosity measurement, this will allow a complete census of cosmic star-formation/AGN accretion history obscured by dust.
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.