Millimeter Observations of the  Pic and AU Mic Debris Disks David J. Wilner Harvard-Smithsonian Center for Astrophysics NASA/JPL-Caltech/T. Pyle 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

Sister Stars with Edge-on Debris Disks  Pic A6 type 19.4 pc R disk > 800 AU AU Mic M1 type 9.9 pc R disk > 200 AU Kalas members of  Pic Moving Group (age ~12 Myr)

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

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

SMA: 1.3 Millimeter Emission Belts Wilner et al  Pic contours: ±2,4,6,8 x 0.6 mJy Wilner et al AU Mic contours: ±2,4,6 x 0.4 mJy 5

Emission Models and Belt Locations  Pic R = 94±8 AU  R = AU F = 15±2 mJy -32 AU Mic R = AU  R = AU F = 8.2±1.2 mJy

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

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

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 μ m 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:  ~ r 2.8 inner collisional depletion? – no detectable asymmetries in structure or position offset limit compatible with presence of Uranus-like planet 9

Summary debris disks are governed by size dependent dust dynamics millimeter emission traces dust-producing planetesimals SMA reveals millimeter emission belts in  Pic 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 10