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Millimeter Observations of the b Pic and AU Mic Debris Disks

David J. Wilner Harvard-Smithsonian Center for Astrophysics. Millimeter Observations of the b Pic and AU Mic Debris Disks. S.Andrews , M. MacGregor , K. Rosenfeld (Harvard-Smithsonian CfA ) A.M. Hughes, E. Chiang, P. Kalas , J. Graham (U.C. Berkeley)

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Millimeter Observations of the b Pic and AU Mic Debris Disks

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  1. David J. Wilner Harvard-Smithsonian Center for Astrophysics Millimeter Observations of the bPic and AU Mic Debris Disks S.Andrews, M. MacGregor, K. Rosenfeld (Harvard-Smithsonian CfA) A.M. Hughes, E. Chiang, P. Kalas, J. Graham (U.C. Berkeley) B. Matthews, M. Booth (HIA), G. Kennedy (IoA), B. Sibthorpe (SRON) New Trends in Radio Astronomy in the ALMA Era, 2012 Dec 5, Hakone NASA/JPL-Caltech/T. Pyle

  2. Sister Stars with Edge-on Debris Disks members of bPic Moving Group (age ~12 Myr) • Pic • A6 type • 19.4 pc • Rdisk > 800 AU AU Mic M1 type 9.9 pc Rdisk > 200 AU Kalas 2004

  3. Scattered Light Midplane Profiles both disks show broken power-law profiles with similar slopes Liu 2004 Golimowski et al. 2006 AU Mic break at R ~35 AU bPic break at R ~120 AU R-1 R-4 R-1 R-4

  4. The “Birth Ring” Paradigm • assume a collisional ring of dust-producing planetesimals • small grains blown out by stellar radiation (bPic) and stellar winds (AU Mic) • large grains stay close to birth ring • size-dependent dust dynamics explains scattered light profile Strubbe & Chiang 2006 (also see Augereau & Beust 2006) scattered light b = F*/Fgrav Krivov 2010 (see Wyatt 2006)

  5. SMA: 1.3 Millimeter Emission Belts bPic AU Mic contours: ±2,4,6 x 0.4 mJy Wilner et al. 2012 contours: ±2,4,6,8 x 0.6 mJy Wilner et al. 2011

  6. Emission Models and Belt Locations • bPic • R = 94±8 AU • DR = 34+44 AU • F = 15±2 mJy -32 AU Mic R = 36+7 AU DR = 10+13 AU F = 8.2±1.2 mJy -16 -8

  7. AU Mic ALMA Cycle 0 Observations 2011.0.00142.S PI Wilner 2011.0.00274.S PI Ertel • 4 SB executions in 2012 April and June • l= 1.3 mm (band 6) • 16 to 20 antennas • beam 0.8 x 0.7 arcsec (8 x 7 AU) • rms = 30 μJy >10x better sensitivity, >10x smaller beam area than SMA study MacGregor et al. 2012, arXiv:1211.5148

  8. Emission Model Fits contours: ±4,8,12,.. x 30 μJy outer belt + central peak

  9. Remarks on AU Mic Modeling • central peak • photosphere + additional unresolved emission • stellar flares? no detectable variability, hours to months • stellar corona? low radio flux limits in quiescence • asteroid-like belt at a few AU? compatible with no excess < 25 μm • outer dust belt • extends to R=40 AU, to the break in scattered light profile • appears truncated, reminiscent of classical Kuiper Belt initial condition? or result of dynamical interaction? • rising surface density profile: S ~ r2.8inner collisional depletion? • no detectable asymmetries in structure or position offset limitcompatible with presence of Uranus-like planet

  10. Summary • debris disks are governed by size dependent dust dynamics • millimeter emission traces dust-producing planetesimals • SMA reveals millimeter emission belts in bPic and AU Mic disks at locations of “birth rings” predicted from scattered light profiles • ALMA Cycle 0 AU Mic data already providing much more detail and showing surprises

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