マゼラン雲中の星形成領域、 分子雲中でのダストの性質 左近　樹、尾中 敬、金田英宏、 加藤大輔、河村晶子、大西利和、福井康雄 AKARI MP/ISMGN team, AKARI IRC team

Interstellar dust Composition Carbonaceous Dust (carbonaceous, silicate, etc.) Infrared emission from diffuse ISM Composition Submicron dust (in thermal equilibrium) (BGs; ~100nm) Polycyclic Aromatic Hydrocarbons (PAHs; ~10Å) Very Small Grains (graphites, small silicate ) (VSGs; 1~10nm, stochastic heating) PAH platelet (≡) 　Carbonaceous Dust PAH cluster (≡) PAH molecule C H Amorphous carbon

IRAS 12/25 and young star clusters (<10Myr) SED characteristics of dust emission around young star clusters in the LMC IRAS 12/25 and young star clusters (<10Myr) → enhancement of 25mm emission around young star clusters (young star clusters catalogue from Bica et al. 1996)

SED characteristics of dust emission around young star clusters in the LMC ISRF distribution; f(U)∝U-b for Umin < U < Umax U=1 corresponds to solar vicinity value (Mathis, Mezger, and Panagia 1983) Iexcess/FIR vs. TBGs 12mm Iexcess/FIR vs. TBGs 25mm Around the Young Star Clusters ; ( Umin , Umax ) = (1, 105) Regions without Young Star Clusters; ( Umin , Umax ) = (0.5, 102) (cf. Sakon et al. 2004, 2006,　Tokura et al. 2006, Hibi et al. 2006)

SED characteristics of dust emission in the CO Molecular Clouds in the LMC NANTEN 12CO(J=1->0) LMC survey data at l=2.7mm (Fukui 2002; Yamaguchi et al. 2001; Mizuno et al. 2001) HPBW 2.6’ at 115GHz Infrared SED; IRAS Sky Survey Atlas 12mm, 25mm, 60mm, 100mm beam size ; 4’ x 4’ -> only the data more than 16’ apart from the young (<30Myr) star clusters in the LMC are used large scatter in 12/25 color for I12CO < 5 K km s-1

SED characteristics of dust emission in the CO Molecular Clouds in the LMC ISRF distribution; f(U)∝U-b for Umin < U < Umax Umin ; CO 分子雲に特徴的な輻射場環境 Umin~0.1; TBGs~13K (Miville-Deschenes et al. 2002) Umax ; CO 分子雲の外部の輻射場環境によって決まる IRAS 12mm / 25mm vs. b for various (Umin , Umax ) b 大; CO分子雲領域が 　　　　領域内で支配的 　　　　（ I12CO 大に相当） b 小; CO分子雲領域 　　　　外側の輻射場 　　　　環境が支配的 　　　　（ I12CO 小に相当） (Umin , Umax ) = (0.1, 10) ; Arc I, Molecular Ridge South etc. (Sakon et al. 2006) (Umin , Umax ) = (0.1, 1000) ; Arc III, Molecular Ridge North etc.

Unidentified Infrared Bands Ubiquitous presence of UIR emission HII region, Reflection Nebulae, Planetary Nebulae, etc. (Tokunaga et al. 1997) Diffuse ISM (Onaka et al. 1996; Mattila et al. 1996) External Galaxies (e.g. Helou et al. 2000) even at z~2 (Yan et al. 2004) H C CH out-of-plane bending CH in-plane CH stretching CC stretching C H trio duo quartet solo UV photon energy UV photon IR photons

Focal plane of AKARI/IRC channels (Onaka et al. 2007)

System spectral response curves of AKARI/IRC imaging filters

System spectral response curves of AKARI/IRC spectroscopic filters (Ohyama et al. 2007) NP/NG: UIR 3.3mm SG1 : UIR 6.2mm, 7.7mm SG2 : UIR 8.6mm, 11.2mm

AKARI/IRC spectroscopy of Diffuse ISM in the LMC Molecular Cloud with Young star cluster near N159 Molecular Cloud without young star clusters IRAS 12mm/25mm

AKARI/IRC spectroscopy of Diffuse ISM in the LMC ① ② ③ [NeII] ① ② ③ Molecular Cloud with Young star cluster near N159 [SIV] [ArIII] -69 -70 -71 -72 90 89 88 87 86 R.A. (B1950) (deg) DEC (B1950) (deg) UIR6.2 UIR7.7 UIR8.6 UIR11.2 UIR12.7 [NeII] [SIV] [ArIII] Molecular Cloud without young star clusters Molecular Cloud with Young star cluster (①, ②) : small 12mm/25mm, large UIR 7.7/11.2 Molecular Cloud without Young star cluster (③) : large 12mm/25mm, small UIR 7.7/11.2

AKARI/IRC Slit-spectroscopy of diffuse ISM in NGC6946

UIR bands in NGC6946 IRC MIR-S/SG1 & SG2 spectra: Arm region, Inter-arm region ※ Zodiacal emission is not subtracted as for (a) and (b) [ArIII] [SIV] Band strengths of UIR 6.2mm and 7.7mm features relative to that of UIR 11.2mm feature become stronger in the arm region than in the inter-arm region : inter-arm arm star forming region UIR 6.2, 7.7mm UIR 6.2, 7.7mm UIR 6.2, 7.7mm < < UIR 11.2mm UIR 11.2mm UIR 11.2mm

Properties of PAHs in NGC6946 UIR band ratios of 6.2mm/11.2mm, 7.7mm/11.2mm, 8.6mm/11.2mm UIR band ratio Inter-Arm*1 Arm*2 S.F.Region*2 [6.2 / 11.2] ext.corr. 0.84(±0.14) 1.33(±0.13) 2.36(±0.64) [7.7 / 11.2] ext.corr. 2.27(±0.32) 3.32(±0.35) 5.51(±1.44) [8.6 / 11.2] ext.corr. 0.50(±0.14) 0.56(±0.09) 0.66(±0.28) *1 no extinction correction for the extreme case *2 Taking account of the extinction of Av=3 mag (Ferguson, Gallagher & Wyse 1998). - As a valid measure of the on-going star formation cf. second plateau component in Peeters et al.2002 UIR band / Plateau Emission in7-9mm ⇒ gas-phase PAHs (20 - 100 NC) / PAH clusters (~500NC) UIR band / plateau emission in7-9mm Feature Inter-Arm Arm S.F.Region UIR* / plateau 0.60(±0.018) 0.65(±0.009) 0.70(±0.016) * Total intensity of UIR 6.2mm + 7.7mm + 8.6mm features More abundant small sized (free-flying) PAHs in Star forming Region possibly as a result of photo-evaporation of PAH clusters into free-flying PAHs

PAHs and PAH clusters (Rapacioli, Joblin and Boissel 2005, A&A, 429, 193) Peak position of “7.7mm” complex UIR7.7/11.2 A : ionized PAHs large 7.57mm B : neutral PAHs small 7.63mm C : PAH clusters -- 7.85mm -> 7.6mm / 7.8mm ratios: PAHs/PAH clusters

PAHs and PAH clusters Results of the fit 7.6mm component 7.8mm component ratio lcenter(fixed) h7.6(free) D7.6(free) lcenter(fixed) h7.8(free) D7.8(free) I(7.6) / I(7.8) (mm) (W/m2/um/pixel) (mm) (mm) (W/m2/um/pixel) (mm) Arm region 7.60 1.34E-16 0.16 7.83 1.40E-16 0.29 0.53 Inter-arm region 7.60 5.84E-17 0.16 7.83 6.95E-17 0.36 0.37 Larger ratio of I(7.6)/I(7.8) in star forming region -> More abundant small sized (free-flying) PAHs in Star forming Region as a result of photo-evaporation of PAH clusters into free-flying PAHs