Source Counts at 15 microns from the AKARI NEP Survey
  We present galaxy counts at 15 microns using the Japanese AKARI satellite's
NEP-deep and NEP-wide legacy surveys at the North Ecliptic Pole. The total
number of sources detected are approximately 6700 and 10,700 down to limiting
fluxes of 117 and 250 microJy (5 sigma) for the NEP-deep and NEP-wide survey
respectively. We construct the Euclidean normalized differential source counts
for both data sets (assuming 80 percent completeness levels of 200 and 270
microJy respectively) to produce the widest and deepest contiguous survey at 15
microns to date covering the entire flux range from the deepest to shallowest
surveys made with the Infrared Space Observatory (ISO) over areas sufficiently
significant to overcome cosmic variance, detecting six times as many sources as
the largest survey carried out with ISO.We compare the results from AKARI with
the previous surveys with ISO at the same wavelength and the Spitzer
observations at 16 microns using the peek-up camera on its IRS instrument. The
AKARI source counts are consistent with other results to date reproducing the
steep evolutionary rise at fluxes less than a milliJansky and super-Euclidean
slopes. We find the the AKARI source counts show a slight excess at fluxes
fainter than 200 microJanskys which is not predicted by previous source count
models at 15 microns. However, we caution that at this level we may be
suffering from the effects of source confusion in our data. At brighter fluxes
greater than a milliJansky, the NEP-wide survey source counts agree with the
Northern ISO-ELAIS field results, resolving the discrepancy of the bright end
calibration in the ISO 15 micron source counts.
