AKARI NEP field: Point source catalogs from GALEX and Herschel observations and selection of candidate lensed sub-millimeter galaxies
The AKARI Wide North Ecliptic field is one of the most important cosmological fields because it lies in the continuous viewing zones for many space telescopes, e.g., Herschel, HST, and JWST, and it is also a natural high-visibility field from the L2 halo orbit. The field will be also the location of the deep survey for the Euclid mission. Finally, AKARI has made deep mid-IR observations using its nine continuous band filters in the North Ecliptic Pole (NEP) field. We analyzed GALEX and Herschel observations in the NEP field to build catalogs in seven bands: GALEX far UV and near UV, Herschel PACS 100 μm and 250 μm, and SPIRE 250 μm, 350 μm, and 500 μm with quality checks. The SPIRE catalogs are used to identify 61 (6 in a main list and 55 in a supplementary list) candidate lensed galaxies through red 350 μm to 500 μm colors. For the brightest of these candidates with 500 μm flux densities >100 mJy, follow-up observations in millimeter wavelengths have been carried out with the NOEMA interferometer. The high quality of these observations has allowed us to study and compare their morphology beyond that possible using Herschel data alone. We find that the majority of them appear as multiple objects. The redshift distribution of the sources in the main list is found to be in the range 1.5 < z < 2.3. Their IR luminosities confirm that these sources are very likely strongly lensed galaxies.