Multi-wavelength analysis of 18 μm-selected galaxies in the akari/infrared-camera monitor field towards the north ecliptic pole

Toshinobu Takagi, Hideo Matsuhara, Takehiko Wada, Shinki Oyabu, Koji Imai, Chris P. Pearson, Hitoshi Hanami, Takashi Onaka, Naofumi Fujishiro, Daisuke Ishihara, Yoshifusa Ita, Hirokazu Kataza, Woojung Kim, Toshio Matsumoto, Hiroshi Murakami, Youichi Ohyama, Itsuki Sakon, Toshihiko Tanabé, Kazunori Uemizu, Munetaka UenoHidenori Watarai, Fumihiko Usui, Hyung Mok Lee, Myungshin Im, Stephen Serjeant, Richard S. Savage, Tsutomu Tange, Takao Nakagawa

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

We present an initial analysis of AKARI 18 μm-selected galaxies using all 9 photometric bands at 2-24 μm available in the Infrared Camera (IRC), in order to demonstrate new capabilities of AKARI cosmological surveys with this unprecedented wavelength coverage at mid-infrared (MIR) bands. We detected 72 sources at 18 μm in an area of 50.2 arcmin2 in the AKARI/IRC monitor field towards the North Ecliptic Pole (NEP). From this sample, 25 galaxies with probable redshifts of z ≳; 0.5 were selected with a single colour cut (N2-N3 ≳; 0.1) for a detailed spectral energy distribution (SED) analysis with ground-based BVRi′z′JK data. Using an SED radiative transfer model of starbursts covering the wavelength range UV-submm, we derived photometric redshifts from the optical-MIR SEDs of 18 μm-selected galaxies. From the best-fit SED models, we showed that the IRC all-band photometry is capable of tracing a steep rise in the flux at the blue side of the polycyclic aromatic hydrocarbon (PAH) 6.2 μm emission feature. This indicates that the IRC all-band photometry is useful to constrain the redshift of infrared galaxies, specifically for dusty galaxies with a less prominent 4000 Å;break. Also, we found that the flux dip between the PAH 7.7 and 11.2 μm emission feature is recognizable in the observed SEDs of galaxies at z ∼ 1. This pilot study suggests the possibility of detecting many interesting galaxy properties in the NEP-Deep and Wide surveys, such as a systematic difference in SEDs between high- and low-z Ultra-Luminous InfraRed Galaxies, and a large variation of the PAH inter-band strength ratio in galaxies at high redshifts.

Original languageEnglish
Pages (from-to)S557-S569
JournalPublications of the Astronomical Society of Japan
Volume59
Issue numberSPEC. ISS. 2
DOIs
Publication statusPublished - 2007
Externally publishedYes

Keywords

  • Galaxies: active
  • Galaxies: evolution
  • Galaxies: starburst
  • Infrared: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Takagi, T., Matsuhara, H., Wada, T., Oyabu, S., Imai, K., Pearson, C. P., Hanami, H., Onaka, T., Fujishiro, N., Ishihara, D., Ita, Y., Kataza, H., Kim, W., Matsumoto, T., Murakami, H., Ohyama, Y., Sakon, I., Tanabé, T., Uemizu, K., ... Nakagawa, T. (2007). Multi-wavelength analysis of 18 μm-selected galaxies in the akari/infrared-camera monitor field towards the north ecliptic pole. Publications of the Astronomical Society of Japan, 59(SPEC. ISS. 2), S557-S569. https://doi.org/10.1093/pasj/59.sp2.s557