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Subaru Seminars are usually held in Room 104 of the Hilo Base Facility, adjacent to the main lobby. Everyone is welcome to attend. If you would like to give a seminar, please contact Subaru seminar organizers (Thayne Currie, Tae-Soo Pyo, Nagayoshi Ohashi) by email : (please change"_at" to @).

August 14, Monday, 11am in 104A

" AGN Variability and Cosmology "

Shintaro Koshida (Subaru)

In this seminar, a new method of distance measurement of Active Galactic Nuclei (AGNs) using the reverberation mapping method on dust tori is presented. AGNs are known for their photometric variability over wide range of wavelength, not only by their high luminosity. Photometric monitoring of AGN revealed that variation patterns of type 1 AGNs in optical/UV wavelength were reproduced as near infra-red (NIR) variation patterns with certain time lags (e.g. Clavel et al. 1989). The time lag can be interpreted according to the unified model of AGNs as the difference of light path between optical/UV emission from accretion disk around super massive black hole traveling directly to an observer, and NIR emission from dust torus surrounding the accretion disk as a thermally reprocessed emission of the dust heating UV emission from the accretion disk. In other words, the lag is a good indicator of an inner radius of a dust torus. Inner radii of dust tori could be calculated with a certain thermal reprocessing model so that it is possible to estimate the intrinsic optical/UV luminosity of AGNs from the time lag. MAGNUM project (e.g. Yoshii 2002) have executed an accurate and frequent photometric monitor of AGN up to redshift 0.6 in optical and NIR wavelength though 8 years from 2000 to 2008. They showed that there is a strong correlation between the time lag and the optical absolute magnitude (Minezaki et al. 2004, Suganuma et al, 2006, Koshida et al, 2014), that dust thermal reprocessing model parameters that is generally accepted explains the correlation (Yoshii et al 2014), and that the distances measured by the reverberation mapping method consists the distance estimated by type Ia supernovae (Koshida et al. 2017). This distance measurement method is new and physical based method, independent of any other distance ladder methods. The preliminary results from AGN variability study using the HSC SSP catalog data will be also introduced in the seminar.

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

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