Massive-Star Supernovae as Major Dust Factories

1. Massive-Star Supernovae as Major Dust Factories Ben E. K. Sugerman, Barbara Ercolano, M. J. Barlow, A. G. G. M. Tielens, Geoffrey C. Clayton, Albert A. Zijlstra, Margaret Meixner, Angela Speck, Tim M. Gledhill, Nino Panagia, Martin Cohen, Karl D. Gordon, Martin Meyer, Joanna Fabbri, Janet. E. Bowey, Douglas L. Welch, Michael W. Regan, Robert C. Kennicutt Jr. Science, 313 (14 July 2006), 196-200 Reviewed by Koji Wada, 21 Nov. 2006

2. Abstract Type II Supernova 2003gd in the galaxy NGC 628 Optical & Mid-Infrared observation by Spitzer Space Telescope and others 499-678 days after outburst: • Mid-IR excesses • Increasing optical extinction • Asymmetries in the emission line profile (blueshift) Radiative-transfer model (3-D Monte Carlo radiative-transfer code: MOCASSIN) Dust formed within the Supernova ejecta ～< 0.02 M Massive-star supernovae may be major dust producers!

3. Introduction How to produce interstellar dust in the early universe: • Gentle winds of low-mass AGB stars? → too long time • Massive stars’ Type II supernovae (SNe) ? →Theoretically possible (0.08-1M), but very low (10-4M ) in previous observations (SNe 1987A, 1999em) Difficult to confirm, because… • SNe are rare and far apart • Remnants are too cold (<30K) to distinguish dust cloud (Spitzer’s IR camera : 50 – 500 K ) Type II-P SN 2003gd (progenitor mass of 8+4-2M ) Rare case of cotemporaneous optical and mid-IR observations!

4. Data in support dust production • Mid-IR excess • Asymmetric blue-shifted emission lines ※ Dust obscures more emission from receding gas. • Increase in optical extinction

5. 1. Mid-IR excess Spitzer mid-IR Hubble 670 days 499 days 3.6, 4.5, 5.8, 8.0 mm 678 days, Multiband Imaging Secptrometer 24 mm Black body fit(5.8,8.0mm@499days): 480 K, L = 4.6×105L r = 6.8×1015 cm

6. 2.Asymmetric blue-shifted emission line Asymmetry Dust with an increasing optical depth is located within and expanding sphere of uniform emission. • Optical extinction AR < 5 for 521 days

7. 3. Increasing optical extinction (1) g-rays from 56Co decay for SN1987A Average opacity: t56 = 0.033 cm2/g Column depth: f0 = 7×104 g/cm2 at t0 = 11.6 days Estimated Extinction

8. Dust-mass analysis 3-D Monte Carlo radiative-transfer code MOCASSIN • Within Spherical, expanding shell with r = rin～ Y rin • r ∝ r -2 • illuminating radiation proportional to the dust density • Grain size distribution : a-3.5 for a = 0.005 – 0.05 mm • Dust composition : 15% amorphous carbon, 85% silicates • source L : according to (1) • T : constant • Dust distribution : “smooth” model & “clumpy” model Rayleigh-Talyor unstable • Spherical clump size rc = 0.025 (Y rin) • Volume filling factor fc • Density contrast a = rc/r • Uniformly distributed Lower mass limit Upper mass limit

9. Y = 7, rin = 5×1015 cm, L = 6.6×105L , T = 5000 K ( fc = 0.02 for clumpy model ) Y = 7, rin = 6.8×1015 cm, L = 9.2×104L , T = 5000 K ( fc = 0.05 for clumpy model ) Model results 499 days 678 days High !

10. Interpretation of dust mass clumpy model mass : 2×10-3M(499 days) - 2×10-2M(678 days) >> analytic estimates 5×10-4M(499 days) - 2×10-3M(678 days) 10-4M for SN 1987A, 1999em → should be revisited >> or ~ mega-grains approximation For smooth dust : 10-5M(499 days) - 4×10-4M(678 days) For clumpy dust : 5×10-3M(499 days) limited use after clumps become optically thick

11. < 0.12 Discussion & Conclusion Condensation efficiency Mass of refractory elements condensed into dust = Mass of refractory elements in ejecta 0.02 M progenitor of SN 2003gd : = 0.16 - 0.42 M • 10 - 12 M • solar metallicity assumed close to 0.2 needed for SNe to account for the dust content of high-redshift galaxies ∴ Supernovae play an important role in the production of dust in the early universe.