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The Subaru Seminar is usually held in Room 104 of the Hilo Base Facility, adjacent to the main lobby. Everyone is welcome to attend. If you are interested in giving a seminar, please contact Subaru seminar organizers (Tadayuki Kodama, Kumiko S. Usuda, Naoyuki Tamura, Tomonori Usuda) by email : (please change"_at_" to @).

August 03, Wednesday, at 11:00 am

" Near- to Mid-Infrared Spectroscopy of ULIRGs: Collaborative Observations with AKARI and Subaru "

Mai Shirahata

(Subaru Telescope)

We present the results of near- to mid-infrared spectroscopic observations of heavily obscured ultra-luminous infrared galaxies (ULIRGs). ULIRGs radiate most of their extremely large, quasar-like luminosities (>10^12 L_sun) as infrared dust emission. Since the energy source of the ULIRGs are thought to be buried within the thick dust and thus not easy to observed from UV to optical, the observations at longer wavelength, i.e., infrared observations play an important role to study them. We have carried out continuous and high-sensitivity infrared spectroscopic observations at 2-13um toward 24 obscured ULIRGs with AKARI/IRC slit-less spectroscopy, which is one of the unique capability of AKARI. The 2-5um spectra are especially valuable, because Spitzer does not have spectroscopic capability in this wavelength region. The spectra show many absorption and emission features from dust, molecules, atoms, and ions. In addition to the many PAH emission features (tracers of starburst activity) and some dust absorption features (tracers of obscured AGNs), we have successfully detected absorption feature due to water ice (indicating the presence of cold molecular gas) and absorption feature caused by gaseous CO (evidence of the existence of warm molecular gas). In order to reveal physical conditions of molecular clouds in ULIRGs directly, we are now making high-resolution spectroscopic observations of fundamental ro-vibration absorption lines of gaseous CO in M-band using the IRCS+AO188 on the Subaru Telescope. This is a unique technique which enable us to determine temperature and column densities of molecular clouds very accurately. We will show these observation results and discuss the physical condition of the molecular clouds in ULIRGs,

Seminars are also held at JAC, CFHT, and IfA.

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