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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
(Tomonori Usuda, Kumiko S. Usuda, Masayuki Akiyama)
by email : sseminar_at_subaru.naoj.org (please change"_at" to @).
May 18, Friday at 11:00 am
" Lyman Alpha Emitters in the Hierarchically Clustering Galaxy Formation "
Masakazu Kobayashi
(Kyoto University)
We present a new theoretical model for the luminosity functions (LFs)
of Lyman alpha (Lya) emitting galaxies in the framework of hierarchical
galaxy formation. We extend a semi-analytic model of galaxy formation
which reproduces a number of observations for local galaxies, without
changing the original model parameters but introducing just a few new
physically-motivated parameters to describe the escape fraction of
Lya photons from host galaxies (fesc). Though a previous study using
a semi-analytic model simply assumed a constant and universal value
of fesc, we introduce two new effects on fesc: extinction by interstellar
dust and effect of galactic-scale outflow induced as a feedback of star
formation. It is found that the new model nicely reproduces all the
observational Lya LFs of the Lya emitters (LAEs) at different redshifts.
Our model predicts that galaxies with strong outflows are dominant in
the observed LFs with fesc ~ 1, which is consistent with available
observational estimates of outflow and fesc, and in contrast to
the universal fesc model that requires fesc << 1.
We then apply our model to estimate the ionization fraction of the universe
at z > 6, and find that the IGM transmission to the Lya emission is less
than unity at z ~ 6, consistent with the recent constraints by other methods.