J- and Ks-Band Galaxy Counts and Color Distributions in the AKARI North Ecliptic Pole Field

Abstract

We present the J- and K_s-band galaxy counts and galaxy colors covering 750 arcmin² in the deep AKARI north ecliptic pole (NEP) field, using the Florida Multi-object Imaging Near-IR Grism Observational Spectrometer on the Kitt Peak National Observatory 2.1 m telescope. The limiting magnitudes with a signal-to-noise ratio of 3 in the deepest regions are 21.85 and 20.15 in the J and K_s bands, respectively, in the Vega magnitude system. The J- and K_s-band galaxy counts in the AKARI NEP field are broadly in good agreement with those of other results in the literature; however, we find some indication of a change in the galaxy number count slope at J~19.5 and over the magnitude range 18.0<K_s<19.5. We interpret this feature as a change in the dominant population at these magnitudes because we also find an associated change in the B-K_s color distribution at these magnitudes, where the number of blue samples in the magnitude range 18.5<K_s<19.5 is significantly larger than that of K_s<17.5.