1 Grain Growth in Protoplanetary Disks: the (Sub)Millimeter Sep 11, 2006 From Dust to Planetesimals, Ringberg David J. Wilner Harvard-Smithsonian Center for Astrophysics

2 Relevance of (Sub)Millimeter “vibrational” dust emission is dominant mechanism (thermal fluctuations in charge distribution) longest observable ’s for dust: 0.35 to 35 mm sensitive to cold dust, T<10’s of K low opacity, sample emission at all disk depths dependence of opacity diagnostic of dust properties (e.g. growth to millimeter size) no contrast issue with stellar photosphere major new facilities under construction: ALMA, eVLA PPV: Natta, Testi, Calvet, Henning, Waters & Wilner, astro-ph/

3 ISM  Protoplanetary Disks 0.85 mm Johnstone & Bally 1999 Williams, Andrews, Wilner 2005

4 T Tauri, Herbig Ae disks (d≤150 pc, 1-10 Myr) –integrated flux vs. (single dish bolometer) observe power law form, F ~ - , 2 <  < 3 –spatially resolved brightness (interferometer) HD Dent et al star dust F~ -2.5 (Sub)Millimeter Observables SMA Raman et al AU

5 mass opacity ( > 0.1 mm) power law form normalization, power law index , depend on dust properties: –composition –size distribution –geometry –… (see Draine 2006) Basics of “  ” Adams et al. 1988, following Draine & Lee 1984  ~ -2

6 flux density emitted by an element dA if  <<1 and h <<kT, then and  simply related to  F ~ -(2+  ) From  to 

7 Beckwith & Sargent (1991) Disk Dust appears Different early (sub)mm obs: disk ~1 vs. ISM  ~1.7 (e.g Weintraub et al. 1989, Adams et al. 1990, Beckwith et al. 1990, Beckwith & Sargent 1991, Mannings & Emerson 1994)  d =(  -2)(1+  )  0 1 2

8  ~1 Interpretations 1. changes in dust properties: –grain growth small, a << /2    =2 large, a >> /2    =0 mm size,  ~1 –  ~ -1 due to dust composition particle geometry 2. optically thick emission: –F ~ -2 (in part)   > (  - 2) Pollack et al mixture, compact, segregated spheres, n(a) ~ a -q, q=3.5 Calvet & D’Alessio 2001 a max =1 mm a max =10 cm

9 Testi et al. (2001) Dust Properties or Optical Depth? e.g. Herbig Ae stars UX Ori, CQ Tau: –  1.1-7mm ~ 2.0±0.3, 2.65±0.1 –  ~ 0 and large disk? any  and small disk?

10 Resolve Ambiguity observe spatial distribution of sub(mm) brightness arcsecond scales require interferometry –1.3, 3 mm: BIMA, OVRO, PdBI, NMA; ATCA, SMA –7 mm: VLA (thanks to CONACyT, MPIfR, NSF) longer : lever minimizes  uncertainty, probes larger dust; more concern about ionized gas

11 combine fluxes, images, improved disk models: –TW Hya –CQ Tau –7 (2) Herbig Ae stars –14 (10) Taurus PMS stars –10 (5) southern PMS stars –24 (20) Taurus/Oph PMS stars Interferometer Studies Calvet et al Testi et al Natta et al Rodmann et al Lommen et al Andrews & Williams 2007 T B vs. disk radius at 0.4, 3, and 7 mm, from two dust models of D’Alessio et al Calvet & D’Alessio 2001

12  =0.7  0.1 Calvet et al Grain Growth in TW Hya irradiated accretion disk model matches SED and VLA (and SMA) intensities from 10’s to R out ~ 200 AU shallow (sub)mm slope requires a max >> 1 mm observed 7 mm low brightness requires  << 1

13 Many (Barely) Resolved Disks VLA 7mm Rodmann et al ATCA 3mm Lommen et al VLA/PdBI/ OVRO Natta et al SMA 0.87/1.3mm Andrews & Williams

14  ≤1 for many/most resolved disks Many More  Determinations solid: Lommen et al dashed: Rodmann et al dotted: Natta et al. 2004

15  is an average, for any dust model –cannot disentangle all properties –  <1: hard to avoid substantial mass fraction a~O( ) Limitations/Complexity of  Natta & Testi 2004  1mm  1-7mm Natta & Testi 2004 a max 

16 TW Hya at 3.5 cm? disk model underpredicts 3.5 cm emission emission mechanism? –ionized protostellar wind if F cm  dM acc /dt, low by 10 3 x –spinning dust (Rafikov 2006) requires high (unrealistic) C fraction in nanoparticles/PAHs –synchrotron X-rays not stellar activity: dense, cool, and depleted  accretion (Stelzer & Schmitt 2004) –thermal dust,   const F ~ -2.6  0.1

17 Weidenschilling 1997Dullemond & Dominik 2005 Grain Size Evolution theory: growth, settling, destruction, … –depart from simple power law size distribution –create midplane population of ~cm size (timescale?)

18 TW Hya: Pebble Population toy model: small + ~cm size grains Wilner et al cm disk dust emission 1. not variable: weeks to years 2. resolved at arcsec scale, brightness only ~10 K 3. steep spectrum to 6 cm

19 no trend of  with stellar luminosity, mass, age tantalizing trends of  with mid-ir growth, settling indicators Any  Correlations? PPV: Natta et al Lommen et al Acke et al  

20 Remarks (sub)mm  <1: compelling evidence for growth –most of original dust mass in mm size particles no clear trends with stellar properties mm/cm sizes persist for Myrs –competition between agglomeration and collisions are the disks we can study in the (sub)mm the ones that will never form planets? –probably not: transition disks

21 Transition Disks: Inner Holes Spitzer IRS implies r~24 AU hole “... we remain skeptical of the existence of such a large central gap [5 AU] devoid of dust.” - Chiang & Goldreich (1999) Calvet et al Wilner et al. 2006

22 Transition Disks: Inner Holes mid-ir implies r~4 AU hole Calvet et al Hughes et al., in prep

23 Next Generation (Sub)mm Facilities 10 to 100x better sensitivity, resolution, image quality dust emission structure at 0.1 to 0.01 arcsec precision (sub)mm spectral index maps at the limits of ALMA Wolf & D’Angelo 2005

24 End