Polycyclic aromatic hydrocarbons (PAHs) are considered to be carriers of the unidentified infrared bands, which are ubiquitously observed in the Universe. PAHs are mainly formed around evolved carbon-rich stars and injected into interstellar space. Planetary nebulae (PNe), a late stage of low- and intermediate stellar mass evolution, are suitable objects to investigate the formation and evolution of PAHs. The shortest PAH feature is located in 3.3 μm, which is important to examine the excitation and size distribution of PAHs. While the number of samples had been limited before, the high sensitivity of AKARI/IRC has drastically increased the number of samples. We obtained the 2-5 μm spectra of Galactic PNe with AKARI/IRC and compiled a near-infrared spectral catalog, containing 73 PNe. We investigate the detection rate and the evolution of the PAH features. The characteristics of the catalog are illustrated and the origin of the evolution of the PAH features is discussed.

ABSTRACT
1. INTRODUCTION
2. NIR SPECTRAL CATALOG OF GALACTIC PNe
3. EVOLUTION OF THE 3μm PAH FEATURES
4. DISCUSSION
5. SUMMARY
REFERENCES

• R. Ohsawa(Institute of Astronomy, Graduate School of Science, The University of Tokyo)
• O. Onaka(Department of Astronomy, Graduate School of Science, The University of Tokyo)
• I. Sakon(Department of Astronomy, Graduate School of Science, The University of Tokyo)
• T. I. Mori(Department of Astronomy, Graduate School of Science, The University of Tokyo)
• H. Kaneda(Division of Particle and Astrophysical Sciences, G, Nagoya University)
• M. Matsuura(Department of Physics & Astronomy, University College London)