(Proposal ID) S15B-013

(PI) Goto, Tomotsugu

(Proposal Title)
Extremely dusty objects in the AKARI NEP field

(Abstract)
The extragalactic background suggests half the energy generated by stars 
reprocessed into the infrared (IR) by dust. Especially, at z~1.3, 90% of star 
formation is obscured by dust. To fully understand the cosmic star formation 
history, it is critical to investigate infrared emission. AKARI has made deep 
mid-infrared (IR) observation using its continuous 9-band filters in the NEP 
field (5.4 deg^2), using ~10% of the entire pointed observations available 
throughout its lifetime. However, there remain 11,000 AKARI's infrared sources 
undetected with the CFHT/MegaCam imaging (r~25.9ABmag). Redshift and IR 
luminosity of these sources are unknown. These sources may carry a significant 
amount of cosmic star-formation rate density (CSFRD). For example, if they all 
lie at 1<z<2, the CSFRD will be twice as high at the epoch. We propose deep 
imaging of the NEP field in remaining 4 broad bands of HSC (r-band HSC data 
taken last year). This will provide  photometric redshift information, and 
thereby IR luminosity for the previously-undetected 11,000 faint AKARI IR 
sources. Combined with AKARI's mid-IR AGN/SF diagnosis, and accurate mid-IR 
luminosity measurement, this will provide a complete census of cosmic star-
formation/AGN accretion history obscured by dust.