Volume 566, June 2014
|Number of page(s)||6|
|Published online||25 June 2014|
Polycyclic aromatic hydrocarbon feature deficit of starburst galaxies in the AKARI North Ecliptic Pole Deep field
1 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, 229-8510 Kanagawa, Japan
2 Department of Space and Astronautical Science, The Graduate University for Advanced Studies, 753-8511 Yamaguchi, Japan
3 National Optical Astronomy Observatory, Tucson AZ 85719, USA
4 Institute of Astronomy and Department of Physics, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan, ROC
5 Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena CA 91125, USA
6 RAL Space, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
7 Department of Physical Sciences, The Open University, Milton Keynes, MK7 6AA, UK
8 Oxford Astrophysics, Oxford University, Keble Road, Oxford OX1 3RH, UK
9 Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, Baja California, Mexico
Received: 3 March 2014
Accepted: 4 April 2014
We study the behaviour of polycyclic aromatic hydrocarbon (PAH) emission in galaxies at z = 0.3–1.4 using 1868 samples from the revised catalogue of AKARI North Ecliptic Pole Deep survey. The continuous filter coverage at 2–24 μm makes it possible to measure 8 μm luminosity, which is dominated by PAH emission, for galaxies at up to z = 2. We compare the IR8 (≡LIR/L(8)) and 8 μm to 4.5 μm luminosity ratio (νL(8) /νL(4.5)) with the starburstiness, RSB, defined as excess of specific star-formation rate over that of main-sequence galaxy. All AGN candidates were excluded from our sample using a spectral energy distribution fitting. We find νL(8) /νL(4.5) increases with starburstiness at log RSB< 0.5 and stays constant at higher starburstiness. On the other hand, IR8 is constant at log RSB< 0, while it increases with starburstiness at log RSB> 0. This behaviour is seen in all redshift range of our study. These results indicate that starburst galaxies have deficient PAH emission compared with main-sequence galaxies. We also find that galaxies with extremely high νL(8) /νL(4.5) ratio have only moderate starburstiness. These results suggest that starburst galaxies have compact star-forming regions with intense radiation, which destroys PAHs, and/or have dusty HII regions resulting in a lack of ionising photons.
Key words: galaxies: starburst / galaxies: evolution / infrared: galaxies
© ESO, 2014
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