Characteristics of mid-IR emission from star-forming galaxies observed by AKARI and Hershel

Seong-Jin KIM^1*, Woong-Seob JEONG², Tomotsugu GOTO¹, Hyung Mok Lee², Hyunjin SHIM³, Chris PEARSON⁴

¹Institute of Astronomy, National Tsing Hua University, Hsinchu, Taiwan
²Space Science Division, Korea Astronomy and Space Science Institute, Daejeon, Korea
³Department of Earth Science Education, Kyungpook National University, Daegu, Korea
⁴RAL space, Ruthorford Appleton Laboratory, Oxfordshire, UK

* Presenter:Seong-Jin KIM, email:seongini@gmail.com

Evolutionary properties of infrared (IR) luminous galaxies are important keys to understand dust-obscured star formation history and galaxy evolution. Based on the near- to mid-IR imaging with 9 continuous filters of AKARI space telescope, we present the characteristics of dusty star-forming (SF) galaxies observed by the North Ecliptic Pole (NEP) wide field survey of AKARI and Herschel. All the sample galaxies from the AKARI/NEP-Wide data are selected based both on the Herschel/SPIRE 250 μm detection and optical spectroscopic redshift data. The physical modeling of spectral energy distribution (SED) using all available data points from u∗ to 500 μm band, including WISE and PACS data where available, takes unique advantages of the continuous near- to mid-IR coverage, reliable constraint on far-IR peak, spectroscopically determined accurate redshifts. This enables us to derive physically meaningful and accurate total infrared luminosity and 8 μm (or PAH) luminosity consistently. Majority of our sample appears to be normal SF/spiral populations showing PAH features near the 8 μm. These SF galaxies showing PAHs in the mid-IR include various types from quiescent to starbursts. Some of our sample show shortage of 8 μm luminosity compared to the total IR luminosity and this PAH deficit gets severe in more luminous IR galaxies, suggesting PAH molecules in these galaxies destroyed by strong radiation field from SF region or a large amount of cold dust in ISM. Our sample shows mass dependent time evolution which is consistent with downsizing evolutionary pattern. We'll discuss the characteristics of our galaxies

Keywords: galaxies: evolution, infrared: galaxies, cosmology: observations