North Ecliptic Pole Wide Field Survey of AKARI: Survey Strategy and Data Characteristics

TL;DR

This paper details the AKARI NEP Wide Survey's strategy, data characteristics, source detection, and source classification, revealing the nature and distribution of infrared sources in the North Ecliptic Pole region.

Contribution

It introduces the survey strategy, data depth, and source characterization of the AKARI NEP Wide Survey, including source counts and galaxy types in infrared wavelengths.

Findings

Detected about 104,000 sources in the NEP region.

Most mid-infrared sources are star-forming disk galaxies.

Stellar fraction decreases with fainter sources.

Abstract

We present the survey strategy and the data characteristics of the North Ecliptic Pole (NEP) Wide Survey of AKARI. The survey was carried out for about one year starting from May 2006 with 9 passbands from 2.5 to 24 micron and the areal coverage of about 5.8 sq. degrees centered on NEP. The survey depth reaches to 21.8 AB magnitude near infrared (NIR) bands, and ~ 18.6 AB maggnitude at the mid infrared (MIR) bands such as 15 and 18 micron. The total number of sources detected in this survey is about 104,000, with more sources in NIR than in the MIR. We have cross matched infrared sources with optically identified sources in CFHT imaging survey which covered about 2 sq. degrees within NEP-Wide survey region in order to characterize the nature of infrared sources. The majority of the mid infrared sources at 15 and 18 micron band are found to be star forming disk galaxies, with smaller fraction of early type galaxies and AGNs. We found that a large fraction (60~80 %) of bright sources in 9 and 11 micron stars while stellar fraction decreases toward fainter sources. We present the histograms of the sources at mid infrared bands at 9, 11, 15 and 18 micron. The number of sources per magnitude thus varies as m^0.6 for longer wavelength sources while shorter wavelength sources show steeper variation with m, where m is the AB magnitude.