Oral Presentation

The importance of dust attenuation for quasar luminosity functions

Author(s): Hikari Shirakata, Takashi Okamoto (Hokkaido university), Motohiro Enoki (Tokyo Keizai university), Masahiro Nagashima (Bunkyo university), Masakazu Kobayashi (Ehime university), Tomoaki Ishiyama (Tsukuba university), and Ryu Makiya (Tokyo university)

Presenter: Hikari Shirakata (Hokkaido University)

We have studied the effect of dust attenuation on quasar luminosity functions by using a semi-analytic model.
This effect has not been considered explicitly in previous studies.
It is important to treat this effect consistently with galaxy properties.

We present our luminosity functions with the dust attenuation and compare it with observed quasar B-band luminosity functions. We find that quasars are dimmed by the dust attenuation ~2 mag. This result suggest that the dust attenuation cannot be negligible.

We also investigate the “delayed accretion model”, in which the gas accretion onto SMBHs is delayed by an order of the dynamical time of their host bulges.
The dust attenuation is weakened by this effect since the gas and dust which reside in SMBHs’ host galaxies are exhausted by starburst and ejected by feedback.

Thanks to the delayed accretion, we can reproduce quasar luminosity functions with more reasonable model parameters than in the case without the delay.

We find that the faint end slope of quasar luminosity functions is a good indicator of quasar lifetime, which can be constrained by the HSC survey.