Planet Formation through Radio Eyes A. Meredith Hughes Wesleyan University Kevin Flaherty (Wesleyan), Amy Steele (Wesleyan), Jesse Lieman-Sifry (Wesleyan), David Wilner (CfA), Sean Andrews (CfA), John Carpenter (Caltech), Angelo Ricarte (Yale), Margaret Pan (GSFC), Hilke Schlichting (MIT), and others…

Star and Planet Formation Overview cloudgrav. collapse protostar + disk + envelope + outflow PMS star + disk MS star + debris disk + planets? Adapted from Shu et al Animation: JPL, M. Roessler

Circumstellar Disk Evolution Protoplanetary Pre-MS stars Gas-rich Primordial dust Debris_____ Main sequence No (or very little) gas Dust must be replenished planets? Some Questions: When and why do disks disperse? What can disks tell us about planet properties? AU Mic, Liu et al HH 30, Burrows et al. 1996

ALMA Observatory meter telescopes at 16,500 ft altitude in the Atacama Desert of northern Chile Person, for scale

The Bird’s-Eye View 1. Disk Dissipation When and why do primordial disks disperse? What can disks tell us about planet properties? 2. Resolving Debris Disk Structure

1. Disk Dissipation When and why do primordial disks disperse?

The standard story Then what is this? Dust looks like a debris disk… But still has lots of molecular gas! Lots of gas/dust left over from SF Gas/dust disappear (~10Myr) Debris dust only

Background: Gas in Debris Disks Zuckerman et al. (1995) Roberge et al. (2000)

Kospal et al. (2013) Moor et al. (2013) Resolved Observations Hughes et al. (2008) Dent et al. (2014) Continuum CO HD β Pictoris

The Mystery of Gas-Rich Debris Disks Is the gas primordial (Peter Pan disks) or second-generation (evaporating comets)? Gas/Dust morphology: Are they in the same place? Gas mass/lifetime: How does it compare to age of star? Gas chemistry: Is it more similar to a disk or a comet? Frequency: Are we seeing something common or unusual?

ALMA Observations of 49 Ceti Jesse Lieman-Sifry

ALMA Observations of 49 Ceti

This… …became this… …which is not symmetric

The Mystery of Gas-Rich Debris Disks Gas/Dust morphology: Are they in the same place? 49 Ceti: Essentially. Both gas and dust fill disk, with 100 AU β Pic: Essentially. Both gas and dust exhibit concentration on one limb HD 21997: No. Gas fills disk while dust is concentrated in a ring Gas mass/lifetime: How does it compare to age of star? All: Lifetime MUCH SHORTER than age of star (of order kyr) Gas chemistry: Is it more similar to a disk or a comet? We’ve only seen CO so far (upper limit on HCN from 49 Cet w/ALMA) From optical lines, 49 Cet and β Pic may be volatile-rich Frequency: Are these disks common or unusual? Free molecular gas with every ALMA-observed A star debris disk! (No CO around F-type HD or M-type AU Mic)

Summary 49 Ceti is an interesting debris disk in its own right. ALMA data dominated by smooth, extended flux component. Steeply rising Σ surrounded by slowly decreasing Σ. 90AU is special (gas+dust). Evidence leans towards second-generation gas, but primordial not ruled out. HD is unusual in mismatched gas/dust morphology. Need to evaporate lots of big comets for a long time.

2. Resolving Debris Disk Structure What can disks tell us about planet properties?

Debris Disks Fomalhaut Kalas et al. (2005) Weinberger et al. (1999) AU Mic Fitzgerald et al. (2007) HR 4796A Schneider et al. (1999) Heap et al. (2000) β Pictoris

Debris Disks If debris disks were primordial, they wouldn’t be there  dust ≤10 Myr Debris disks look different at different wavelengths 70  m; Su et al. (2005) 350  m; Marsh et al. (2006)850  m; Holland et al. (2006) At least 15% of nearby main-sequence stars have debris disks (Habing et al. 2001, Rieke et al. 2005, Trilling et al. 2008, Hillenbrand et al. 2008)

Debris Disks and Millimeter Interferometry Wyatt (2006) Why Millimeter? Few stellar radiation effects Good for tracing parent planetesimal belts and resonances Why Interferometry? Can resolve distant sources Particularly good at picking out clumps and rings

Our Solar System ~ 4.4Gyr ago? Uniform sample of debris disks spatially resolved using mm-wave interferometry Sample: young Solar analogues from FEPS Steele et al. in prep

Courtesy Amy Steele Grain size M disk M belt β Rin ΔR PA inclination

Results ParameterHD 377HD 8907 HD HD HD R in (AU) ΔR (AU)<70<10 <13109 a (μm) β M D (M  ) Axisymmetric? YYYYY Courtesy Amy Steele

Results – Axisymmetry Courtesy Amy Steele

Conclusions Most radii are similar to the Kuiper belt Grain sizes are comparable to the blowout grain size  1-3x larger than the BB radius Only one disk has a resolved width No detected asymmetries Ricci et al. (2014)

Vertical height of edge-on debris disks has been measured before, but only at optical wavelengths, where it is puffed up by starlight. Scale height at mm wavelengths directly measures the total mass of perturbing bodies in the disk. Ongoing: Vertical structure of edge-on debris disks Based on Pan & Schlichting (2012) Based on Thebault (2009)

Summary Debris disks with molecular gas inform deadline for giant planet formation. Second-generation evaporating comets are likely, but Peter Pan (primordial material) is still a possibility! Young Solar analogs w/bright debris look mostly like Kuiper belts. Debris disk dust is not actually very clumpy, despite planets! Edge-on debris disks measure total mass.