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Cosmic Dust Enrichment and Dust Properties Investigated by ALMA

Cosmic Dust Enrichment and Dust Properties Investigated by ALMA. Hiroyuki Hirashita ( 平下 博之 ) (ASIAA, Taiwan). Topics. What Is “Known” about Galaxy Dust? Dust Enrichment (Especially at High- z ) More Detailed Look (Low- z ) Summary. To stimulate your idea!.

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Cosmic Dust Enrichment and Dust Properties Investigated by ALMA

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  1. Cosmic Dust Enrichment andDust Properties Investigated by ALMA Hiroyuki Hirashita (平下 博之) (ASIAA, Taiwan)

  2. Topics • What Is “Known” about Galaxy Dust? • Dust Enrichment (Especially at High-z) • More Detailed Look (Low-z) • Summary To stimulate your idea!

  3. 1. What Is “Known” about Galaxy Dust?

  4. Dust Extinction in the Milky Way Lund Observatory Optical (l ~ 0.5 mm) Scattering + Absorption (= Extinction) of stellar light by dust grains

  5. Extinction Curve Extinction (absorption+scattering) as a function of  i: grain species (silicate, graphite) a2Q(a): grain cross section Mathis et al. (1977) Grain size distribution Ndust(a) ∝ a with 0.005 m < a < 0.25 m optical UV (1) Only applicable for very nearby galaxies. (2) Evidently ALMA bands cannot do this.

  6. Milky Way in Far Infrared Thermal emission from dust COBE 140 mm

  7. Properties of Far-Infrared (FIR) Spectral Energy Distribution (SED) Excess by very small grains (VSGs) 140 m Intensity Large grains (LGs) in radiative equilibrium with the interstellar radiation field FIR sub-mm Wavelength (mm) Désert et al. (1990)

  8. Merits/Demerits of FIRSubmm SED is simple: I = CB(Tdust) (+) a few wavelengths are enough to observe (-) very limited information on dust material () (2) Depends on Tdust (+) good tracer of the interstellar radiation field (star formation activity) (-) a single wavelength observation is not enough (⇒ collaboration with AKARI, Spitzer, Herschel) (3) grain size <<  in FIR-submm ⇒ mass absorption coefficient is independent of grain size (-) no information for the grain size (+) good tracer of grain amount

  9. Nucleosythesis in the Universe C, N, O, …, Fe H, He, Li Metals (→ solid = dust) Dust already existed at z ~ 6 (Bertoldi et al. 2003). Beginning of Metal (dust) Production Grasp of “primeval galaxies” in the Universe ＝ Understanding of the initial metal/dust enrichment Dust in Cosmological Context t NASA

  10. Sub-mm for High-z Dust Tdust = 42 K LIR = 1.4 × 1012 L ALMA bands are suitable for high redshift. Detection limits: 100 arcmin2 survey with 500 h (Y. Tamura) 850 m

  11. 2. Dust Enrichment(Especially at High-z) The dust enrichment in the local Universe is already complicated (formation from supernovae, AGBs, ..., growth in interstellar clouds, destruction by shocks, etc.) High-redshift (z > 5) is simpler (formation/destruction by supernovae is dominated)!

  12. Ly Emitter One of the young populations found at the highest z. Iye et al. (2006) Kashikawa et al. (2006) Observational indication of dust E(BV) = 0.035  0.32 (Finkelstein et al. 2009) 0.025  0.3 (Pirzkal et al. 2007)

  13. Detectability of the first dust enrichment in the Universe Possible to Detect Early Dust Enrichment in the Universe? • Modeling of dust enrichment in LAEs. • Estimate of the FIR/sub-mm flux from a LAE. • Detectability by ALMA.

  14. Theoretical Framework Dayal, Hirashita, & Ferrara (2009) • Cosmological SPH simulation (75 h-1 Mpc)3 ⇔ 2000 arcmin2 • Dust enrichment and destruction by supernovae to obtain Mdust for each galaxy. GADGET homepage (Springel 2005)

  15. LIR Estimation for Each Galaxy Optical depth of dust for stellar UV light: UV = 3dust/(4as) dust = Mdust/(R2) Escape fraction of UV continuum fc = [1  exp(-UV)]/UV FIR luminosity LFIR = (1 fc)LUV0 Dust temperature and SED L = 4MdustB(Tdust) FIR (sub-mm) flux f = (1 + z)L(1 + z)/(4dL2) Dust size a = 0.05 m Material density s = 2.3 g/cm3

  16. ALMA Observation Strategy Dayal, Hirashita, & Ferrara (2010) Blue: 850 m Green: 1.4 mm Red: 3 mm 850 m is the most suitable. lines: detection limits with 1 hour integration (full ALMA) Early dust formation by stars (supernovae) can be quantified.

  17. 3. More Detailed Look(Low-z)

  18. Combination with FIR I = CB(Tdust) FIR data by AKARI, Spitzer, and Herschel help to estimate Tdust. high dust temperature 60 m / 100 m flux ratio Large range of dust temperature traced in FIR. Hirashita & Ichikawa (2009) 140 m / 100 m flux ratio

  19. Sub-mm can distinguish the difference. “Embedded” Cold Dust Shielded from Stellar Radiation Hirashita & Ichikawa (2009) increase of cold dust (1) UV↑ (shield)⇒ cold dust↑ (2) radiation field↑⇒ Tdust↓

  20. 4. SummaryI: Early Cosmic Dust Enrichment • Early production of dust by stars • How much dust forms in stars? • Prediction by nucleation theory (e.g., Nozawa et al. 2003) is correct? • How fast? (⇒ Evolution of dust optical depth ⇒ reionization) • Connection with the planet formation? • What should theory do? • Predict as many (global) quantities which dust concerns. ex. reionization, molecular hydrogen abundance, luminosity function from UV to FIR

  21. II: Detailed Look of Nearby Galaxies • Shielded (embedded) dust • Physical condition of dust grains in star-forming galaxies (especially the optical depth) • Geometry of dust distribution •  (silicate/graphite ~ 2; some amorphous ~ 1 1.5) • Combination with AKARI, Spitzer, and Herschel is crucial.

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