GILLETT SYMPOSIUM SUMMARY

1. GILLETT SYMPOSIUM SUMMARY 11- 13 April, 2002 Stephen E. Strom

2. Disk Accretion Phase

3. Disk Accretion Phase: Ubiquity • 100% for stars with M < 1 MO (observed) • 100% for higher mass stars (inferred) • Collimated jets • Evidence for ‘funnel flows’ • Rotational properties • J/M vs M is continuous • Accretion through disks enables assembly • Radiation pressure would otherwise reverse accretion

4. Disk Accretion Phase: Lifetimes • 0.1 < t < 10 Myr for solar-type stars • Upper limit not well established • Environment may affect lifetimes • Photoevaporation; tidal interactions • 0.1 <t < ? Myr for higher mass stars • Disk lifetimes are shorter than for 1 MO stars • Stellar rotation provides additional clues • N(vsini) for a Per requires disk lifetimes up to ~5 Myr • Rotation rates higher in high density regions • Shorter disk lifetimes? Higher accretion rates? • Caveat: PMS ages are highly uncertain for t < 3 Myr • Tracks • Birthline • Uncertainties in L, Teff

5. Inner Accretion Disk Lifetimes (Meyer)

6. Disk Accretion Phase: Masses • Total mass estimates based on dust mass • mm continuum emission • Range: Mdust ~ 10-3 to 10-5 MO • These are lower limits • Mass int > 1 regions underestimated • Large bodies not detected • Mass estimates depend on (uncertain) grain properties • No reliable estimates of gas content • The total mass available for planet building may well exceed the “minimum mass nebula” • Mass comprising star passes through a disk • Instantaneous disk mass is a lower limit

7. Disk Accretion Phase: Sizes • Largest centrifugally supported disks: ~ 300 AU • Larger, structures found, but no evidence of rotational support • Orion silhouette disks provide direct measurement • 20 < r < 200 AU (~ 50 disks) • Photo-evaporation and tidal encounters may truncate disks in rich, dense environments • Correlation between disk size and proximity to q Ori • Kuiper belt cutoff may reflect photo-evaporation (Hollenbach)

8. Disk Accretion Phase: Accretion Rates • Estimated from ultraviolet excess emission • Measures inner disk accretion rate • dM/dt increases with increasing mass • dM/dt ~ 10-7.5 for 0.5 MO; may increase ~ linearly with M • Instantaneous rates are lower than time-averaged rates • Accretion rates ~103 higher during FU Ori phase • Recall that total mass passing through the disk is large • Wide dispersion (> 10x) in dM/dt at fixed age and mass • Q: might this dispersion reflect the effects of planets? • Binarity and tidal encounters may affect dM/dt

9. Disk Accretion Phase: Larger Bodies • Growth of grains (to 1 cm) estimated from SEDs • Presence of larger bodies inferred from • FEBs (but cf Grady: now suggests accretion origin in HAeS) • Cyrstalline silicate emission in cold disk regions (?) • Evidence favors planet formation during accretion phase • N(a) for extrasolar planets suggests accretion-driven migration • Best (only?) time to form gas giants • Large O/IR telescopes and later, ALMA, should enable detection of ‘gaps’ diagnostic of forming giant planets • Establish the fraction of stars that form giant planets initially • Establish the N(a) during the accretion phase • Is there an (interesting) upper limit to a ?

10. Diagnosing Forming Planets

11. GSMT AURA-NIO Point Design

12. ALMA Star at 10pc

13. Debris Disk Phase

14. Debris Disk Phase • Sparsely-sampled photometry and SEDs • Statistics: <t>, s (t) vs age • Radial distribution t (r) , (if SED is well sampled) • mineralogical probes • Statistical studies suggest • Decrease of t with age (Ldust/ L* ~ t -1.75) • Possible rapid decline of t for stars with ages t > 400 Myr • Radial distributions: low t inner zones • Mineralogy • Solid state features can in principle be matched to source bodies

15. Debris Disk Phase • Caveat regarding ages • Transformation to L,Teff a problem for t < 200 Myr • Large starspots + photosphere = composite spectral type • Cluster ages (t < 200 Myr) are uncertain at 0.3 dex level • Li-depletion ages • Systematic difference with upper MS turnoff • Rotation affects surface Li • Efficacious for selected spectral type ranges only • Activity-age estimates (e.g. Ca II) • Large dispersion • Conclude (Stauffer): • Relative age uncertainties for field stars up to 0.6 dex

16. Debris Disk Phase • Imaging: scattered light; thermal IR; mm • Radial distribution of dust • Selected cases reveal (cf Alycia Weinberger) • Low density inner zones • Warps • Rings • Non-axisymetric features • Q: do these provide evidence of planets? • Modeling suggests yes • Analysis of solar system zodi strongly supportive

17. Beta Pictoris

18. HR4796a

19. Epsilon Eridani

20. Debris Disk Phase • Spectroscopic searches for disk gas (steady state) • CO emission (mm-wave measurements) • H2 infrared features (ISO; ground) • H2; CO ultraviolet absorption features • Results • Significant differences between (uv; ground) and ISO • Concensus: [gas/dust] << ISM value • Not enough to build giant planets • Could mitigate dust migration; quantitative study needed • Suggestion that gas is ‘secondary’: evaporated volatiles • High priority for future work • SIRTF observations of H2 spanning wide age range • Knowledge of gas content key to modeling dust evolution • Key Focus: young (5 – 20 Myr) debris disk stars • Do post-accretion phase disks have gas sufficient to build giant planets?

21. Debris Disk Phase • Spectroscopic monitoring (time variable) • Episodic red-shifted absorption features from metals • Suggest presence of ‘falling, evaporating bodies’ • Limited results suggest origin in refractory bodies

22. Debris Disk Phase: The Future • SEDs from SIRTF • Well sampled from 3m – 160m • Diagnose t ( r ); infer presence of gaps • Mineralogical features: probe parent body composition • observe transition from ISM to debris-dominated disks • High angular resolution imaging from the ground • Map solid and gaseous components at sub-AU scales

23. Debris Disk Phase: Solar System Clues • Sources of dust: collisions • Outer solar system: Kuiper Belt objects • Inner solar system: Asteroid Belt objects • In both cases, orbits are ‘stirred’ by planets • Observed disk properties; evolution depend on • Planetesimal/cometesimal distribution; initial density • Planetary architecture • Effects of gravitational and drag forces • Warps; rings; offsets in zodi dust linked to planets • Density enhancements caused by resonant trapping

24. Debris Disk Phase: Solar System Clues • Dust injection into zodiacal cloud stochastic • Expect large variations in t • Large collisions may give rise to ‘dust waves’ • Timescales ~ 104.5 to 106 yrs • Possible significant climatic consequences • Kuiper belt primordial mass: > 10-4 MO • KB extends S ( r ) from inner solar system to > 100? AU • Slow Collisions produce 100-1000km bodies in ~ 100Myr • Fast Collisions erode initial KBOs • Produce dust (observed by Pioneer?); comets • Total KB mass has likely decreased 1000-fold over 5 Gyr • KB probably similar to outer regions of extrasolar disks

25. Extrasolar Planetary Systems

26. Extrasolar Planetary Systems • (Jovian) planet detection rate ~ 10% • Of these, multiple planet systems common (> 50%) • Unexpected distribution of a for giant planets • N(a) distribution suggests migration • What stops migration (cf Artymowicz)? • Favors formation during accretion phase • Stars with inner Jupiters may have higher Z • Caveats • N(a) suffers from strong observational bias • High M sini favored by Doppler techniques • Consistent analysis of metallicities is critical (underway) • Focus on F stars (thinner convection zones)

27. GSMT: www.aura-nio.noao.edu AURA-NIO Concept Direct detection with ExAO GSMT enables direct detection and analysis of planets

28. Debris Disks and the Formation of Planets A true celebration of Fred Gillett whose Insight Imagination Persistence Care Integrity Decency Generosity of spirit Sense of community are a continuing inspiration to us all