Subaru Seminars
- Press
Releases
- Preprint&Reprint
- Subaru Seminars
- Resources
- Links
- Preprint&Reprint
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 : sseminar_at_subaru.naoj.org (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.