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Abstract: Using an AKARI multi-wavelength mid-infrared IR survey, we identifyluminous starburst galaxies at z> 0.5 based on the PAH luminosity, andinvestigate the nature of these PAH-selected starbursts. An extragalacticsurvey with AKARI towards the north ecliptic pole NEP, the NEP-Deep survey,is unique in terms of a comprehensive wavelength coverage from 2 to 24um usingall 9 photometric bands of the InfraRed Camera IRC. This survey allows us tophotometrically identify galaxies whose mid-IR emission is clearly dominated byPAHs. We propose a single colour selection method to identify such galaxies,using two mid-IR flux ratios at 11-to-7um and 15-to-9um PAH-to-continuum fluxratio in the rest-frame, which are useful to identify starburst galaxies atz~0.5 and 1, respectively. We perform a fitting of the spectral energydistributions SEDs from optical to mid-IR wavelengths, using an evolutionarystarburst model with a proper treatment of radiative transfer SBURT, in orderto investigate their nature. The SBURT model reproduces observedoptical-to-mid-IR SEDs of more than a half of PAH-selected galaxies. Based onthe 8um luminosity, we find ultra luminous infrared galaxies ULIRGs amongPAH-selected galaxies. Their PAH luminosity is higher than local ULIRGs with asimilar luminosity, and the PAH-to-total IR luminosity ratio is consistent withthat of less luminous starburst galaxies. They are a unique galaxy populationat high redshifts and we call these PAH-selected ULIRGs -PAH-luminous-galaxies. Although they are not as massive as submillimetre galaxies at z~2,they have the stellar mass of >3x10^{10} Msun and therefore moderately massive.

Author: T.Takagi, Y.Ohyama, T.Goto, H.Matsuhara, S.Oyabu, T.Wada, C.P.Pearson, H.M.Lee, M.Im, M.G.Lee, H.Shim, H.Hanami, T.Ishigaki, K.Im

Source: https://arxiv.org/


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