Hyper-luminous dust-obscured galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE

Abstract

We present the photometric properties of a sample of infrared (IR) bright dust-obscured galaxies (DOGs). Combining wide and deep optical images obtained with the Hyper Suprime-Cam on the Subaru Telescope and all-sky mid-IR (MIR) images taken with Wide- Field Infrared Survey Explorer, we discovered 48 DOGs with i − Ks > 1.2 and i − [22] > 7.0, where i, Ks, and [22] represent AB magnitude in the i-band, Ks-band, and 22 μm, respectively, in the GAMA 14 hr field (∼ 9deg2). Among these objects, 31 (∼ 65%) show power-law spectral energy distributions (SEDs) in the near-IR (NIR) and MIR regime, while the remainder show an NIR bump in their SEDs. Assuming that the redshift distribution for our DOGs sample is Gaussian, with mean and sigma z = 1.99 ± 0.45, we calculated their total IR luminosity using an empirical relation between 22μm luminosity and total IR luminosity. The average value of the total IR luminosity is (3.5± 1.1) × 1013 L , which classifies them as hyper-luminous infrared galaxies. We also derived the total IR luminosity function (LF) and IR luminosity density (LD) for a flux-limited subsample of 18 DOGs with 22 μm flux greater than 3.0mJy and with i-band magnitude brighter than 24 AB magnitude. The derived space density for this subsample is log φ = − 6.59 ± 0.11 [Mpc−3]. The IR LF for DOGs including data obtained from the literature is fitted well by a double-power law. The derived lower limit for the IR LD for our sample is ρIR ∼ 3.8 × 107 [L Mpc−3] and its contributions to the total IR LD, IR LD of all ultra- luminous infrared galaxies, and that of all DOGs are > 3%, > 9%, and > 15%, respectively.