Optical properties of Dust-Obscured Galaxies viewed with Hyper Suprime- Cam

Akatoki Noboriguchi

Dust-Obscured Galaxies (DOGs) are red, dusty galaxies with F[24]/F[R] ≥ 1000, which implies dust heating by significant SF, AGN, or both. DOGs can be classified into two types: AGN- and SF-dominated DOGs based on their SEDs, and some authors have reported that the brighter mid-infrared (IR) DOGs are more AGN-dominated. Although particularly IR-bright DOGs could constitute a key population for understanding the co-evolution of galaxies and supermassive black holes, efficient searches for them have been difficult in previous surveys due to their low surface densities.Thanks to the advent of deep and wide imaging surveys with optical and mid-IR, Toba et al. (2015) successfully discovered 48 IR-bright DOGs based on Hyper Suprime-Cam (HSC) and WISE. In particular, they used near-IR data obtained from VIKING to reduce the mis-identification of DOGs due to the significant difference of the angular resolution for HSC and WISE. However, (i) it could be difficult to discuss their statistical properties robustly since sample size is small (48), (ii) the survey region was limited to the overlap area (∼ 10 deg^2) between HSC and VIKING, and (iii) since they used HSC early data (S14A 0) where only two band information are available, the optical properties of IR-bright DOGs is still unknown.In this work, we attempted to solve the above issues using new HSC data where five-band photometry are available. Combining the HSC S15A, VIKING DR2, ALLWISE data, we discovered 424 IR-bright DOGs in ∼ 55 deg^2, and we investigated their optical properties. We found that their g-z color distribution is bimodal: the SF-dominated DOGs occupy the redder parts while AGN-dominated DOGs occupy the bluer part. Possible impli- cations based on the obtained result will be also discussed.