A New View of Interstellar Dust as Revealed by Recent Observations Takashi Onaka (University of Tokyo) ASTRO-FISASSpitzerNASA Diffuse Emission from Galactic Plane Log S(W/m 2 /sr) COBE IRTS/MIRS Thermal Emission (submicron dust) Wavelength ( m) Excess emission (stochastically heated very small grains) UIR bands (~PAHs) Outline Systematic variations in the UIR band features in the Galactic plane Characteristics of the MIR excess emission Solid features in the diffuse IR emission other than the UIR bands X-ray observations of interstellar dust Future prospects PHT-S results of Galactic plane Wavelength ( m) Surface Brightness (10 -6 W m -2 mm -1 sr -1 ) Kahanp et al. (2003) A&A 405, 999 No systematic variations in the UIR bands on GP l = 5, 15, 30, 60 & b = 0, 1 (49 quiet regions) IRAS100 m & UIR7.7 m Area I l ~ -10 Area II l ~ +50 Area III l ~ -130 Area IV l ~ +170 IRAS100 m UIR7.7 m Sakon et al. (2004) ApJ, 609, 203 Good correlation between UIR & 100 m Typical spectra Wavelength ( m) Surface Brightness (x10 -7 W m -2 mm -1 sr -1 ) Area IArea II Area IIIArea IV UIR/FIR ratio UIR/FIR Wavelength ( m) inner outer UIR/FIR larger in the outer Galactic plane -> Difference in destruction/formation balance Shifts in peak wavelengths Wavelength ( m) Relative Number Peak shifts -> Profile variation (more tails at longer wavelengths in the inner Galaxy) 13 C effects or excitation and/or inclusion effects 6.2 m band 11.3 m band Correlation with radiation field U 12 m & UIR7.7 m band U F /FIR UIR7.7 m/FIR F (12 m)/FIR W51 & G.C. (IRTS) Carina (ISO) 25 m/FIR U F /FIR F (25 m)/FIR U Stochastic heating model 60 m/FIR F (60 m)/FIR U U F /FIR Correlation of excess emission with U Observations: Excess/FIR U (25 & 60 m) Multiphoton excitation cannot account for the observations because of the very broad nature of the excess emission Superposition of different radiation field components in the line-of-sight (Tokura et al. in preparation) (Dale et al. 2001, ApJ 549, 215) f(U, ) : emission with a particular U 25 m/FIR T(K) F /FIR Umin=0.1Umin=100 Umax=10 5 Umax=10 4 Umax=10 5 Umax=10 4 60 m/FIR T(K) F /FIR 12 m/FIR T(K) F /FIR MIR-FIR SED Good measure for the physical conditions & active region fraction (for galaxies) 65 m & 90 m features Wavelength ( m) Surface Brightness (x10 -6 Wm -2 m -1 sr -1 ) Onaka & Okada (2003) ApJ, 585, 872 Sharpless 171 region 65 m feature & diopside Wavelength ( m) Surface Brightness (x10 -6 Wm -2 m -1 sr -1 ) Diopside (CaMgSi 2 O 6 ) 65 m feature versus temperature (65 m)/ (100 m) Okada et al. in preparation 65 m feature Volatile species? 90 m feature & carbon onion T(K) Flux/Continuum Possible candidate: Carbon onion or curved graphite sheet Oxygen K edge structure Takei et al (2002) ApJ, 581, 307 Cyg X-2 Gas/Dust abundance can be estimated From X-ray Spectroscopy Gas/Dust ~( ) X-ray Absorption Fine Structure Ueda et al. (2005) ApJ, 620, 274 Si XAFS GX13+1 Silicates XAFS Estimate of dust abundance & Diagnostic of chemical state of element in solid phase Fe metal or oxide? -> ASTRO-E2 ASTRO-F All-sky survey in 4 bands in FIR ( m) + 2 bands in MIR (5-26 m) 70cm cooled telescope Sun synchronous orbit Target launch: 2006 Two instruments on board IRC (2-26 m) & FIS ( m) Pointed observations 9 bands in NIR-MIR 4 bands in FIR Spectroscopy in NIR-FIR (2-26 m; m) ASTRO-F observations of interstellar dust Wavelength ( m) Log S(W/m 2 /sr) ASTRO-F can separate each emission component IRACMIPS IRC FIS
