1. Protoplanetary Disks: The Initial Conditions of Planet Formation Eric Mamajek University of Rochester, Dept. of Physics & Astronomy Astrobio 2010 – Santiago de Chile – 15 January 2010 Special thanks to: Michael Meyer (U. Arizona, ETH Zurich) Dan Watson (U. Rochester)

2. Spitzer Early Release Observations Why do circumstellar disks matter? - initial conditions of planet formation. - trace evolution of planetary systems. - attempt to place our solar system in context.

3. Mayor & Udry (2008) Motivation to understand disks: The formation and evolution of planetary systems

4. Mayor & Udry (2008) Motivation to understand disks: The formation and evolution of planetary systems

5. Cloud collapse 10 4 yr Planetary system + debris disk 10 9 yr 10 5 yr 100 AU 10 7 yr T star (K) L star / L Sun Main sequence 8,0005,000 10 1 2,000 Protostar+ primordial disk Planet building Pre-main Sequence Evolution

6. Evolution of Circumstellar Disks Primordial Accretion Disks Gas-rich, survive ~10 6-7 years. Dusty Debris Disks Gas-poor, dusty disks seen around stars of all ages. But dust lifetimes are ~10 3 -10 6 yrs (blowout, PR drag). Hence planetesimal reservoirs needed!

7. What disk properties do we care about? * Total disk mass: M disk, M disk /M * Outer & inner radii: R out, R in Surface density profile: Σ(r) = Σ o r -p Dust grain size distribution: n(a) ~ n o a -q ; a min, a max Dust grain opacity law: κ ν ~ ν β Optical depth: τ ν = κ ν Σ(r) Temperature profile: T(r) ~ T o r -q Scale height, Midplane density: H(r), ρ o (r) Viscosity: ν v = α c s H ~ ν vo r γ (MRI?) Composition (gas, dust), Ionization, Azimuthal asymmetry, etc. * While you are at it… we want to know the statistical moments of these parameters vary as a function of stellar parameters, orbital radius, birth environment, and TIME!

8. Mass Time Disk Surface Density Orbital Radius Primary Mass An Analytical Estimate of Protoplanet Growth Lodato et al. (2005) Recipe for planet growth is sensitive to disk surface density, orbital distance, stellar mass, time Ida & Lin (2004); Lodato et al. (2005); see also classic papers by Safronov (1969) & Pollack et al. (1996)

9. Star with magnetospheric accretion columns Accretion disk Disk driven bipolar outflow Infalling envelope Current Paradigm: Infall Rate: 10 -5 M sun /yr Accretion Rate: 10 -8 M sun /yr Shu, Adams, & Lizano ARAA (1987) Hartmann Cambridge Press (1998) Mass Loss Rate: 10 -9 M sun /yr

10. Primordial accretion disk signatures for T Tauri stars Spectroscopic: Emission lines from accreting gas (e.g. Hα) Photometric: Infrared/mm excess from disk (Mamajek+ 1999) (Domminik+2003)

11. Kenyon & Hartmann (1995) Ann Rev Ast Astrophys. FU Ori Outbursts Time M(accr)

12. Protostellar Disks (10 5 -10 6 yrs): Initial Conditions of Planet Formation Standard model: –Most of stellar mass passes through disk. Limits on disk masses: – < 10-25 % of central mass or disk is gravitationally unstable (Adams et al. 1990). Size of disk grows with time with viscous evolution, and accretion rate falls – Theory: R(disk) increases with specific angular momentum (Tereby et al. 1984). – Observations: e.g. Kitamura et al. (2002), Isella et al. (2009) Cloud Infall Rate >> Disk Accretion Rate: – Leads to disk instability and outburst (FU Ori stage). Outbursts decrease with time: –The last one fixes initial conditions of remnant disk (=> planets)

13. Mm/Sub-mm constraints on disk parameters Andrews & Williams (2005, 2007; SMA) Also Kitamura et al. (2002; NMA), Isella et al. (2009; CARMA)

14. Lifetimes of Primordial Disks Plotted are the fraction of stars in clusters with primordial disks traced by Hα excess and/or Spitzer IRAC infrared excess All stars: τ ~ 2.5 Myr High mass stars (>1.3 Msun) τ ~ 1 Myr Brown dwarfs (<0.08 Msun) τ ~ 3 Myr See also Hernandez+2008, Haisch+2001 Mamajek (2009; arXiv:0906.5011; Subaru meeting on Exoplanets & Disks)

15. Lifetime of solar systems protoplanetary disk? Castillo-Rogez et al. 2007 Modeling thermal history of Iapetus (constraints on shape, heating by short-lived radionuclides) Saturn formed from gas-rich disk within 2.5-5 Myr of CAIs

16. Factors Influencing Disk Evolution Stellar mass: –Disk masses are proportional to stellar masses –Lifetimes inversely related to mass (Carpenter et al. 2006, Mamajek 2009) Close companions: –dynamical clearing of gaps (Jensen et al. 1995; 1997; Meyer et al. 1997b; Ghez et al. 1997; Prato et al. 1999; White et al. 2001). Formation environment: –cluster versus isolated star formation (Hillenbrand et al. 1998; Kim et al. 2005; and Sicilia-Aguilar et al. 2004).

17. Transitional disk R. Hurt, SSC/JPL/Caltech/NASA Transitional disks

18. GM Aur (Calvet et al. 2005) Model of IRS spectrum: 1.05 M classical T Tau star Wall of optically thick disk = outer edge of gap at 24 AU. Radial gap, 5-24 AU, with very little dust. Inner gas disk with radius 5 AU, and a minute amount of small dust grains. In agreement with submillimeter image of cold dust in the disk (Wilner et al. 2007).

19. Typical Disk Parameters ParameterMedian~1σ Range Log(M(disk)/M(star))[all ~1 Myr] [detected disks only] -3.0 dex -2.3 dex ±1.3 dex ±0.5 dex Disk lifetime2-3 Myr1-6 Myr Temperature power law [T(r) ~ r -q ]0.60.4-0.7 Taken from (or interpolated/extrapolated from): Muzerolle et al. (2003), Andrews & Williams (2007), Hernandez et al. (2008), Isella et al. (2009) ParameterMedian~1σ Range R(inner)0.1 AU~0.08-0.4 AU R(outer)200 AU~90-480 AU Surface density power [Σ(r) ~ r -p ] [Hayashi min. mass solar nebula] [steady state viscous α disk] 0.6 1.5 1.0 0.2-1.0 (predicted) Surface density norm. Σ o (5AU) 14 g cm -2 ±1 dex

20. Chemistry Differences in organic chemistry important as a function of stellar mass? e.g. HCN/C 2 H 2 (Pascucci+ 2009, Daniel Apais talk). Ionization levels may vary significantly from protostar to protostar (X-ray/UV fluences from central star & neighboring stars? Cosmic rays?) Water in young protoplanetary disks – Where? How much? (Bill Dents talk is next)

21. Points to take away… Planet formation is relevant after M(disk)/M(star) < 10 -1 -10 -2, and T Tauri disks are observed to typically have M(disk)/M(star) ~ 10 -3±1. Protoplanetary disk lifetimes have big dispersion t ~ 10 6.4±0.4 years. Disks survive longer around low-mass stars. Evolution is not just age. There are hidden variables in disk evolution! UV photoevaporation can disperse disks within 10 Myr; A mechanism for short transition times and mass-dependence of disk lifetimes? Transition disks: does planet formation help drive disk evolution? Preliminary evidence of stellar mass-dependent disk chemistry. Disk ionization controls MRI (viscosity mechanism) and disk chemistry, and so control disk evolution and some aspects of planet formation

22. More observations (imaging and spectroscopy; especially resolved observations) of disks in the IR/mm/radio are needed to improve constraints on the properties of gas and dust in protoplanetary disks, and thereby constrain the initial conditions of planet formation!