SPATIAL DISTRIBUTION OF STAR FORMATION ACTIVITY ON NGC 253 BY FIR AND RADIO EMISSION LINES

ABSTRACT The aim of this research is to reveal the spatial distribution of the star formation activity ofnearby galaxies by comparing CO molecular emission lines with the large area observation in far-infrared (FIR) lines. We report the imaging observations of NGC 253 by FIR forbidden lines viaFIS-FTS and CO molecular lines from low to high excitation levels with ASTE, which are goodtracers of star forming regions or photo-dissociation regions, especially spiral galaxies, in order toderive the information of the physical conditions of the ambient interstellar radiation elds. Thecombination of spatially resolved FIR and sub-mm data leads to the star formation eciency withingalaxy. The ratio between the FIR luminosity and molecular gas mass, L FIR /M H 2 , is expected tobe proportional to the number of stars formed in the galaxy per unit molecular gas mass and time.Moreover the FIR line ux shows current star formation activity directly. Furthermore these canbe systematic and statistical data for star formation history and evolution of spiral galaxies.Key words: nearby galaxy: NGC 253; star formation; spectroscopy: FIR, sub-mm1. INTRODUCTIONThe objectives of this observation is to reveal the sitesof star formation using suitable methods; (1) derivationof wide range spectral energy distribution (SED) fromNIR to radio for various type of galaxies, (2) estima-tion of current starforming activity (to the star forma-tion history in galaxies) by FIR ne structure lines, (3)sub-mm and radio data lead to physical parameters ofthe extended molecular gas around the disk, and con-sequently (4) derivation of star formation eciency bycomparison with sub-mm lines (CO) and FIR lines ([C