Protoplanetary and Debris Disks A. Meredith Hughes Wesleyan University

Star and Planet Formation Overview cloudgrav. collapse protostar + disk + envelope + outflow PMS star + disk MS star + debris disk + planets? Adapted from Shu et al. 1987

1. Protoplanetary Disks

Exciting recent results: Gaps and Traps ALMA Partnership et al. (2015)Fukagawa et al. (2014) Exploring the interaction between circumstellar disks and planetary systems in formation

Exciting recent results: Snow Lines and Water Qi et al. (2013) Cleeves et al. (2014) Exploring the origin of the Solar System’s water and other ices: lots of planet- forming material available

Dust/Gas Dynamics Pinilla et al. (2015) Other Research Themes Low-Mass stars: Brown Dwarf Disks Ricci et al. (2014) Environment: Disks in Orion Mann et al. (2014) Chemistry: Organic molecules Oberg et al. (2015)

Future Questions and Capabilities: Terrestrial planet zones τ = 1 at λ = 1mm (ALMA) τ = 1 at λ = 3cm (NGVLA) Optical Depth: τ = Σ κ ν Don’t need to improve over ALMA resolution; need to make sensitivity/resolution of longer-λ facilities comparable

Future Questions and Capabilities: Dust, Gas, and the Meter-Size Barrier 1cm – 1m is VERY interesting grain size for theory of planet formation. Radial Drift Meter size barrier Time evolution: -Planet formation is quick after meter-size barrier crossed, but when/how does this happen? Brauer et al. (2007) C. Dullemond Modified from Fu et al. (2014)

Future Questions and Capabilities: Dust, Gas, and the Meter-Size Barrier Log [Emission Efficiency (Q)] Log λ 1 Turnover at 2πa a At a given wavelength, large grains (a>λ) are the most efficient emitters Log [Grain Size (a)] Log [Number of Grains (N)] dN/da ∞ a -3.5 Many more small grains than large. Small grains dominate surf area Net effect: Smallest grain that can emit efficiently will dominate flux at a given wavelength. Grain size ≈ Wavelength of observation Need long wavelengths to see pebbles

Future Questions and Capabilities: Dust, Gas, and the Meter-Size Barrier One more piece of the puzzle: κ ν ∞ λ -1 (opacity) (Surface density) Millimeter flux (optically thin): F ν ∞ Σ * κ ν * B ν (T) ∞ λ -3 (Planck function ∞ λ -2 ) The bottom line: Flux drops off like crazy with wavelength. Need LOTS of sensitivity to image pebbles.

2. Debris Disks

Exciting recent results: Surface Density Structures (mm & OIR) Ricci et al. (2014) 2015 ALMA – Hughes et al. (in prep) Interactions between disks and mature planetary systems are revealed by surface density structures; dynamics are different in OIR vs. radio

Exciting recent results: Molecular Gas in Debris Disks Dust CO Dent et al. (2014)Carpenter et al. (in prep) Molecular gas is commonly detected in A star debris disks β Pic is unusual in showing CO asymmetry

Future Questions and Capabilities: Multiwavelength Disk Dynamics Wyatt (2006) Already have plenty of angular resolution; need sensitivity to see subtle features, study disk-planet interaction, and do surveys – bring Solar System within reach! Macintosh et al. (2015)

Future Questions and Capabilities: Gas Chemistry Hughes et al. (in prep) Best prospects for spatially resolved chemistry in the radio; want to know composition of ices/volatiles in other solar systems

Debris Disks Summary and Conclusions Protoplanetary Disks Terrestrial planet zone Radial drift and the meter-size barrier Need lots of sensitivity at long wavelengths Multiwavelength dust dynamics – planet-disk interaction Gas chemistry Need lots of sensitivity, NOT angular resolution