Evolution of mid-infrared galaxy luminosity functions from the entire AKARI NEP-Deep field with new CFHT photometry

TL;DR

This study uses new CFHT optical/near-IR data to improve the accuracy of infrared galaxy luminosity functions in the AKARI NEP-Deep field, covering a wide redshift range and providing more reliable measurements of cosmic infrared luminosity density evolution.

Contribution

It presents the first comprehensive mid-infrared galaxy luminosity functions over the entire AKARI NEP-Deep field with improved photometric redshifts and filter coverage, reducing uncertainties compared to previous studies.

Findings

Luminosity functions are consistent with previous work but with reduced uncertainties.

The cosmic infrared luminosity density evolves as (1+z)^{4.2±0.4}.

Accurate restframe 8μm, 12μm, and TIR luminosities are derived without large extrapolations.

Abstract

We present infrared galaxy luminosity functions (LFs) in the AKARI North Ecliptic Pole (NEP) deep field using recently-obtained, wider CFHT optical/near-IR images. AKARI has obtained deep images in the mid-infrared (IR), covering 0.6 deg$^2$ of the NEP deep field. However, our previous work was limited to the central area of 0.25 deg$^2$ due to the lack of optical coverage of the full AKARI NEP survey. To rectify the situation, we recently obtained CFHT optical and near-IR images over the entire AKARI NEP deep field. These new CFHT images are used to derive accurate photometric redshifts, allowing us to fully exploit the whole AKARI NEP deep field. AKARI's deep, continuous filter coverage in the mid-IR wavelengths (2.4, 3.2, 4.1, 7, 9, 11, 15, 18, and 24$\mu$m) exists nowhere else, due to filter gaps of other space telescopes. It allows us to estimate restframe 8$\mu$m and 12$\mu$m luminosities without using a large extrapolation based on spectral energy distribution (SED) fitting, which was the largest uncertainty in previous studies. Total infrared luminosity (TIR) is also obtained more reliably due to the superior filter coverage. The resulting restframe 8$\mu$m, 12$\mu$m, and TIR LFs at $0.15<z<2.2$ are consistent with previous works, but with reduced uncertainties, especially at the high luminosity-end, thanks to the wide field coverage. In terms of cosmic infrared luminosity density ($\Omega_{\mathrm{IR}}$), we found that the $\Omega_{\mathrm{IR}}$ evolves as $\propto (1+z)^{4.2\pm 0.4}$.