Search for Optically Dark Infrared Galaxies without Counterparts of Subaru Hyper Suprime-Cam in the AKARI North Ecliptic Pole Wide Survey Field

TL;DR

This study identifies and characterizes highly obscured, high-redshift infrared galaxies lacking optical counterparts, revealing their physical properties and potential for future JWST observations.

Contribution

It presents a new sample of optically dark infrared galaxies with detailed multi-wavelength analysis, highlighting their high redshifts and dust obscuration, which were previously missed by optical surveys.

Findings

Objects without HSC counterparts have higher redshifts, up to z~4.

They exhibit larger stellar masses, star formation rates, and dust attenuation.

Sample includes luminous, heavily obscured SFGs/AGNs at z~1-4.

Abstract

We present the physical properties of AKARI sources without optical counterparts in optical images from the Hyper Suprime-Cam (HSC) on the Subaru telescope. Using the AKARI infrared (IR) source catalog and HSC optical catalog, we select 583 objects that do not have HSC counterparts in the AKARI North Ecliptic Pole (NEP) wide survey field ($\sim 5$ deg$^{2}$). Because the HSC limiting magnitude is deep ($g_{\rm AB}$ $\sim 28.6$), these are good candidates for extremely red star-forming galaxies (SFGs) and/or active galactic nuclei (AGNs), possibly at high redshifts. We compile multi-wavelength data out to 500 $\mu$m and use it for Spectral Energy Distribution (SED) fitting with CIGALE to investigate the physical properties of AKARI galaxies without optical counterparts. We also compare their physical quantities with AKARI mid-IR selected galaxies with HSC counterparts. The estimated redshifts of AKARI objects without HSC counterparts range up to $z\sim 4$, significantly higher than that of AKARI objects with HSC counterparts. We find that: (i) 3.6 $-$ 4.5 $\mu$m color, (ii) AGN luminosity, (iii) stellar mass, (iv) star formation rate, and (v) $V$-band dust attenuation in the interstellar medium of AKARI objects without HSC counterparts are systematically larger than those of AKARI objects with counterparts. These results suggest that our sample includes luminous, heavily dust-obscured SFGs/AGNs at $z\sim 1-4$ that are missed by previous optical surveys, providing very interesting targets for the coming James Webb Space Telescope era.