Dust Growth in Protoplanetary Disks: The First Step Toward Planet Formation. Laura Pérez Jansky Fellow NRAO

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1 Dust Growth in Protoplanetary Disks: The First Step Toward Planet Formation Laura Pérez Jansky Fellow NRAO

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3 From ISM Dust to Planetary Systems Size = µμm ISM Dust mm mm/cm observations Directly observable (IR à mm/cm) m? km Mm Planets Exo- planets Adapted from Chiang & Youdin (2009)

4 Growth of small grains: easy! Very small ISM dust grains coupled to the collapsing gas Initial (rapid) growth: Brownian motion 4

5 Growth of small grains: easy! Large particles decouple from gas Settling towards disk mid-plane Sweep up other particles à further growth F gas drag F grav* (z) 5

6 Grow of larger grains: it gets hard! Particles ~ few cm: sticking efficiencies drop v rel > 1 m/s: fragmentation or bouncing Also: Radial drift problem (Weidenschilling 1977) Timescale ~ yr Small dust ~ sub- Keplerian Large dust ~ Keplerian 6

7 From ISM Dust to Planetary Systems Radial drift Fragmentation Size = µμm mm m km Mm ISM Dust mm/cm observations? Planets Directly observable (IR à mm/cm) Exo- planets Adapted from Chiang & Youdin (2009)

8 Structure of disk impacts its emission Atomic + Molecular Gas = 99% of the disk mass Dust = 1% of the disk mass, but it carries 99% of the disk opacity Temperature

9 Different wavelengths probe different regions Full extent of disk is be_er probed at millimeter/centimeter wavelengths 2.2 µμm Cumulative Flux/Mass 10 µμm 1.3 mm mass

10 Different wavelengths probe different grain sizes A warm dust grain most efficiently emits energy at λ its size Small grains Large grains Single Grain Opacity 0.1 µμm k(λ) λ cm k(λ) λ 0

11 Different wavelengths probe different grain sizes A warm dust grain most efficiently emits energy at λ its size Single Grain Opacity Opacity for grain size distribution 0.1 µμm k(λ) λ cm k(λ) λ 0

12 Many global studies have inferred β<β ISM These observations imply growth from ISM sizes (µμm) to pebble sizes (cm) OVRO/CARMA JCMT/SMA VLA PdBI/IRAM ATCA Beckwith & Sargent (1990, 1991) Mannings & Sargent (1997,2000) Ricci et al. (2011a, 2012) Mannings & Emerson (1994) Wilner et al. (2000) Andrews & Williams (2005, Calvet et al. (2002) 2007) Testi et al. (2001,2003) Lommen et al. (2007) Na_a et al. (2004) Ricci et al. (2011b) Wilner et al. (2005) Rodmann et al. (2006) Ricci et al. (2011b) Dutrey et al. (1996) Na_a et al. (2004) Schaefer et al. (2009) Ricci et al. (2010) Lommen et al. (2007, 2009) Ricci et al. (2010) Ricci et al. (2011a)

13 Measuring dust size vs. orbital radius Multiwavelength observations can constrain beta(r) CARMA observations errorbar on β~ ± 1 log( ν 1 /ν 2 )ln10 " $ # ΔS ν1 S ν1 2 % ' & " + ΔS % ν 2 $ ' # & S ν mm 2.7 mm Isella et al. (2010) See also: Guilloteau et al. (2011) Banza_i et al. (2011) 13

14 Measuring dust size vs. orbital radius Going to longer wavelengths is important to constrain beta(r) PI: Claire Chandler A. Isella (Caltech) L. Perez (NRAO) A. Sargent (Caltech) L. Mundy (Maryland) S. Storm (Maryland) H. Linz (MPIA) J. Greaves (St. Andrews) S. Corder (NRAO) A. Deller (NRAO) S. Andrews (CfA) D. Wilner (CfA) J. Carpenter (Caltech) N. Calvet (Michigan) C. Dullemond (MPIA) J. Lazio (JPL) L. Testi (ESO) L. Ricci (ESO) T. Henning (MPIA)

15 Grain Growth in the AS 209 Protoplanetary Disk Dust grains in the inner disk are different from those in the outer disk 2.5 3σ 2σ 1σ β mm β ISM β C =1.0 Indicates difference with ISM dust Excludes β=const VLA SMA CARMA Disk Radius [AU]

16 Grain Size vs. Orbital Radius Maximum grain size throughout disk is consistent with population limited by radial drift Radial drift barrier Fragmentation barrier Grain growth models from Birnstiel et al. (2012)

17 How to overcome the radial drift barrier? Dust drifts toward pressure maxima à further growth may be possible here P gas (R) Adapted from P. Pinilla R

18 A dust trap in Oph IRS 48 ALMA Observations + near IR Van der Marel et al. (Science 2013)

19 ALMA is already revolutionizing this field! Fukagawa et al. (2013) Pérez et al. (2014)

20 Conclusions Observational constraints of dust growth require: Multi-wavelength observations High angular resolution and high SNR Future with new instruments like ALMA and VLA looks Protoplanetary disks have β < 1 at mm/cm wavelengths (from unresolved observations) Compelling evidence for grain growth in disks Spatially resolved observations can: o o Disentangle optical depth effects from grain growth Main limitation for further particle growth à radial drift of solids A way to overcome this problem: dust trapping of large particles Radially in rings, azimuthally in vortices These predictions can be currently tested with ALMA and VLA