AKARI FAR-INFRARED ALL-SKY SURVEY MAPS

Abstract

Far-infrared observations provide crucial data for the investigation and characterisation of the properties of dusty material in the Interstellar Medium (ISM), since most of its energy is emitted between ~ 100 and <TEX>$200{\mu}m$</TEX>. We present the first all-sky image from a sensitive all-sky survey using the Japanese AKARI satellite, in the wavelength range <TEX>$50-180{\mu}m$</TEX>. Covering > 99% of the sky in four photometric bands with four filters centred at <TEX>$65{\mu}m$</TEX>, <TEX>$90{\mu}m$</TEX>, <TEX>$140{\mu}m$</TEX>, and <TEX>$160{\mu}m$</TEX> wavelengths, this achieved spatial resolutions from 1 to 2 arcmin and a detection limit of < 10 MJy <TEX>$sr^{-1}$</TEX>, with absolute and relative photometric accuracies of < 20%. All-sky images of the Galactic dust continuum emission enable astronomers to map the large-scale distribution of the diffuse ISM cirrus, to study its thermal dust temperature, emissivity and column density, and to measure the interaction of the Galactic radiation field and embedded objects with the surrounding ISM. In addition to the point source population of stars, protostars, star-forming regions, and galaxies, the high Galactic latitude sky is shown to be covered with a diffuse filamentary-web of dusty emission that traces the potential sites of high latitude star formation. We show that the temperature of dust particles in thermal equilibrium with the ambient interstellar radiation field can be estimated by using <TEX>$90{\mu}m$</TEX>, <TEX>$140{\mu}m$</TEX>, and <TEX>$160{\mu}m$</TEX> data. The FIR AKARI full-sky maps provide a rich new data set within which astronomers can investigate the distribution of interstellar matter throughout our Galaxy, and beyond.