Mid-infrared (MIR) galaxies in the northern sky: their mysterious PAHs emissions

Seong-Jin KIM^1*, Tomotsugu GOTO¹, Matt MALKAN², Nagisa OI³, Daryl Joe Santos¹, NEP team⁴

¹IoA, NTHU, Hsinchu, Taiwan
²Tokyo University of Science, Tokyo, Japan
³Department of physics and astronomy, UCLA, L.A, USA
⁴Division of space science, KASI, Daejeon, Korea

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

We know that polycyclic aromatic hydrocarbons (PAHs) are out in space, essentially everywhere in the dust or gas phases of the interstellar medium (ISM), near our Galaxy and others far away. However, we do not know their exact structures or origins. Their complexity of the spectra makes the actual interpretation difficult. The infrared space telescopes have been trying to reveal even a small part of clues to these puzzles. For example, the Spitzer telescope gave large contributions to the PAH astrophysics with high sensitivity. But the MIR range, where we can observe a series of strong emission features (at 3.3, 6.2, 7.7, 8.6, 11.3, 12.7 μm), has never been fully covered. Yet the mysterious connections to galaxy evolution or star-forming activities have never been cleared out.   However, we have valuable observation data continuously covering this MIR range, through the legacy NEP survey of AKARI, taking advantage of the unique filter bands covering these wavelengths. However, this data set has not been fully available due to the unsatisfactory supplementary optical data and serious lack of photometric redshifts. Now, with the recently reduced HSC optical survey data over this field and newly released photometric redshift, more detailed analyses are possible, especially based on the physically motivated modeling using the mixture of various star formation scenario, AGN, and ISM (e.g., dust) models. We will discuss the detailed results at the conference.

Keywords: Galaxy Evolution, Cosmology, Infrared Galaxies, PAH