TY - GEN
T1 - AKARI near-infrared spectroscopy of 3 micron PAH and 4 micron PAD features
AU - Onaka, T.
AU - Sakon, I.
AU - Ohsawa, R.
AU - Shimonishi, T.
AU - Okada, Y.
AU - Tanaka, M.
AU - Kaneda, H.
PY - 2011
Y1 - 2011
N2 - Near-infrared (NIR; 2.5-5 μm) low-resolution (λ/Δλ ~ 100) spectra were obtained for a number of Galactic and extragalactic objects with the Infrared Camera (IRC) in the AKARI warm mission. These data provide us with the first opportunity to make a systematic study of the 3.3-3.5 μm PAH features in a galactic scale as well as within an object. Whereas the 3.3 μm band is well resolved in most spectra, the 3.5 μm band is not clearly separated from the 3.4 μm band in the IRC spectrum. The intensity ratio of the summation of the 3.4 and 3.5 μm bands to the 3.3 μm band shows a tendency to increase towards the Galactic center, although a large variation in the ratio is also seen in a local scale. A search for deuterated PAH features in the 4 μm region is carried out in IRC NIR spectra. Emission lines originating from the ionized gas together with the detector anomaly hamper an accurate search at certain wavelengths, but little convincing evidence has so far been obtained for the presence of significant features in 4.2-4.7 μm. A conservative upper limit of a few percents is obtained for the integrated intensity ratio of the 4.4-4.7 μm possible features to the 3.3-3.5 μm PAH features in the spectra so far obtained.
AB - Near-infrared (NIR; 2.5-5 μm) low-resolution (λ/Δλ ~ 100) spectra were obtained for a number of Galactic and extragalactic objects with the Infrared Camera (IRC) in the AKARI warm mission. These data provide us with the first opportunity to make a systematic study of the 3.3-3.5 μm PAH features in a galactic scale as well as within an object. Whereas the 3.3 μm band is well resolved in most spectra, the 3.5 μm band is not clearly separated from the 3.4 μm band in the IRC spectrum. The intensity ratio of the summation of the 3.4 and 3.5 μm bands to the 3.3 μm band shows a tendency to increase towards the Galactic center, although a large variation in the ratio is also seen in a local scale. A search for deuterated PAH features in the 4 μm region is carried out in IRC NIR spectra. Emission lines originating from the ionized gas together with the detector anomaly hamper an accurate search at certain wavelengths, but little convincing evidence has so far been obtained for the presence of significant features in 4.2-4.7 μm. A conservative upper limit of a few percents is obtained for the integrated intensity ratio of the 4.4-4.7 μm possible features to the 3.3-3.5 μm PAH features in the spectra so far obtained.
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U2 - 10.1051/eas/1146006
DO - 10.1051/eas/1146006
M3 - Conference contribution
AN - SCOPUS:84874352860
SN - 9782759806249
T3 - EAS Publications Series
SP - 55
EP - 60
BT - PAHs and the Universe
T2 - PAHs and the Universe: A Symposium to Celebrate the 25th Anniversary of the PAH Hypothesis
Y2 - 31 May 2010 through 4 June 2010
ER -