The AGN fraction of submm-selected galaxies and contributions to the submm/mm-wave extragalactic background light

TL;DR

This study compares submillimeter galaxy data with mid-infrared surveys to understand their contributions to the cosmic background light and the role of AGN activity, revealing different populations dominate at various wavelengths.

Contribution

It provides new insights into the AGN fraction in submm-selected galaxies and their contributions to the extragalactic background light using combined AKARI and Spitzer data.

Findings

AKARI 15um galaxies contribute >10% to 450 micron background.

Less than 4% of 1100 micron background is from AKARI 15um galaxies.

23-52% of submm galaxies have significant AGN bolometric fractions.

Abstract

We present a comparison of the SCUBA Half Degree Extragalactic Survey (SHADES) at 450, 850 and 1100 microns with deep guaranteed time 15 microns AKARI FU-HYU survey data and Spitzer guaranteed time data at 3.6-24 microns in the Lockman Hole East. The AKARI data was analysed using bespoke software based in part on the drizzling and minimum-variance matched filtering developed for SHADES, and was cross calibrated against Infrared Space Observatory (ISO) fluxes. Our stacking analyses find AKARI 15um galaxies with >~200 microJy contribute >10% of the 450 micron background, but only <4% of the 1100 micron background, suggesting that different populations contribute at mm-wavelengths. We confirm our earlier result that the ultra-deep 450 micron SCUBA-2 Cosmology Survey will be dominated by populations already detected by AKARI and Spitzer mid-infrared surveys. The superb mid-infrared wavelength coverage afforded by combining Spitzer and AKARI photometry is an excellent diagnostic of AGN contributions, and we find that (23-52)% of submm-selected galaxies have AGN bolometric fractions f_AGN>0.3.