The Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) will provide all-sky spectral survey data covering optical to mid-infrared wavelengths with a spatial resolution of 6.′′2, which can be widely used to study galaxy formation and evolution. We investigate the galaxy-galaxy blending in SPHEREx datasets using the mock galaxy catalogs generated from cosmological simulations and observational data. Only ∼0.7% of the galaxies will be blended with other galaxies in all-sky survey data with a limiting magnitude of 19 AB mag. However, the fraction of blended galaxies dramatically increases to ∼7–9% in the deep survey area around the ecliptic poles, where the depth reaches ∼22 AB mag. We examine the impact of the blending in the number count and luminosity function analyses using the SPHEREx data. We find that the number count can be overestimated by up to 10–20% in the deep regions due to the flux boosting, suggesting that the impact of galaxy-galaxy blending on the number count is moderate. However, galaxy-galaxy blending can marginally change the luminosity function by up to 50% over a wide range of redshifts. As we only employ the magnitude limit at Ks-band for the source detection, the blending fractions determined in this study should be regarded as lower limits.

We present the mid-infrared (MIR) luminosity function (LF) of local (z < 0.3) star-forming (SF) galaxies in the North Ecliptic Pole (NEP) field. This work is based on the NEP-Wide point source catalogue and the spectroscopic redshift (z) data for  1700 galaxies obtained by the optical follow-up survey with MMT/Hectospec and WIYN/Hydra. The AKARI's continuous 2 - 24 μm coverage and the spectroscopic redshifts enable us to determine the spectral energy distribution (SED) in the mid-infrared and derive the luminosity functions of galaxies. Our 8 μm LF finds good agreements with the results from SWIRE field over the wide luminosity range, while showing signicant difference from the NOAO deep data in the faint end. The comparison with higher-z sample shows significant luminosity evolution from z > 0.3 to local universe. 12 μm LF also shows a clear indication of luminosity evolution.

We present the 18μm luminosity function (LF) of galaxies at 0.006 < z < 0.8 (the average redshift is ~ 0.04) using the AKARI mid-infrared All-Sky Survey catalogue. We have selected 243 galaxies at 18μm from the Sloan Digital Sky Survey (SDSS) spectroscopic region. These galaxies then have been classified into five types; Seyfert 1 galaxies (Sy1, including quasars), Seyfert 2 galaxies (Sy2), low ionization narrow emission line galaxies (LINER), galaxies that are likely to contain both star formation and Active Galactic Nuclei (AGN) activities (composites), and star forming galaxies (SF) using optical emission lines such as the line width of H α or the emission line ratios of [OIII]/ Hβ and [NII]/ Hα . As a result of constructing the LF of Sy1 and Sy2, we found the following results; (i) the number density ratio of Sy2 to Sy1 is 1.64±0.37 , larger than the results obtained from optical LF and (ii) the fraction of Sy2 in the entire AGN population may decrease with 18μm luminosity. These results suggest that most of the AGNs in the local universe are obscured by dust and the torus structure probably depends on the mid-infrared luminosity.