Evolution of protoplanetary disks

1. Evolution of protoplanetary disks N. Calvet (SAO) C. Briceno (CIDA) P. D’Alessio (UNAM) J. Hernandez (CIDA) L. Hartmann (SAO) J. Muzerolle (Steward Observatory) A. Sicilia-Aguilar (SAO)

2. Disk evolution • Disks evolve from optically thick dust+gas configurations to mostly solids debris disks HK Tau, Stapelfeldt et al. 1998 Characteristic timescales Physical processes

3. Disk evolution • Evolution from optically thick dust+gas configurations formed in the collapse of rotating molecular cores to debris disks with mostly solids to planetary systems • First: grain growth from mm studies (Beckwith & Sargent 1991; Dutrey et al. 1996) • Much research in recent years, SPITZER • Evolution of gas and dust (~ 1% of total)

4. Gas:accretion onto star Inner disk is truncated by stellar magnetic field at ~ 3-5 R*. Matter flows onto star following field lines – magnetospheric accretion flow Hartmann 1998

5. Evidence for magnetospheric accretion BP Tau Model Redshifted absorption if right inclination Redshifted absorption Broad emission lines (Ha,Brg,etc.) formed in magnetospheric flow Muzerolle et al. 1998a,b, c, 2001 Magnetospheric flow

6. Accretion shock Evidence for magnetospheric accretion Excess emission/veiling: consistent with accretion shock emission Veiling Excess Calvet & Gullbring 1998; Gullbring et al. 2000; Calvet et al. 2004

7. Accretion luminosity and mass accretion rate Excess emission over photosphere ~ Lacc = G M (dM/dt) / R Gullbring et al. (1998)

8. Evolution of mass accretion rate for Classical T Tauri stars (~ K5-M3) Viscous evolution - Gas Hartmann et al. (1998), Muzerolle et al. (2001), Calvet et al. (2005) .50 .23 .12 Fraction of accreting objects decreases with time (LAH talk) What stops accretion?

9. Dust evolution in inner disk • Good knowledge of timescales for dust evolution in inner disks – even more with SPITZER data (LAH ‘s talk) • What is happening to the dust? Hillenbrand, Carpenter, & Meyer 2005

10. Decrease of excess emission with age Near-IR colors of older population much lower Taurus, 1-2 Myr Ori OB1b, 3-5 Myr Briceno et al 2005 Calvet et al. 2005

11. Decrease of excess emission with age Taurus median SEDs of stars in Tr 37 ~ 3 Myr IRAC data Weaker than median of Taurus Accreting stars (C) without excesses Weak TTS (W) with excess Phot Sicilia-Aguilar et al 2005

12. Present picture of inner disk Near-IR emission mostly from wall at dust destruction radius

13. Art by Luis Belerique Excess decreases with age • large contribucion from wall to near-IR • decrease of dM/dt or • decrease of wall emitting area => height & Rui Azevedo

14. Grain growth in disks Median SED of Taurus quartiles amax = 1mm No silicate emission ISM Models with dust and gas distributed uniformly D’Alessio et al 2001

15. Spitzer/IRS spectra of T Tauri stars Midplane of optically thin outer disk silicate feature emission –> small grains Hot upper layers of optically thick inner disk SEDs -> large grains Grain Growth and Settling surface Calvet et al 1991; Meyer et al 2000 Forrest et al 2004

16. Settling of solids towards the midplane: effects on SED Depletion of upper layers: upp/st • Lower opacity of upper layers • Decrease capture of energy • Lower T, less emission Furlan et al 2005 D’Alessio et al 2005

17. Settling of solids toward midplane Depletion of upper layers: upp/st Furlan et al. 2005

18. Settling of solids toward midplane diameter a e range of i’s Furlan et al. 2005

19. Dust growth and settling • As disk ages, dust growths and settles toward midplane as expected from dust evolution theories t = 0 Population of big grains at midplane Upper layers get depleted Weidenschilling 1997 Observations agree with expectations, (although problem with timescales)

20. Settling of solids: TW Hya 3.5 cm flux ~ constant=> Dust emission Wilner et al. 2005 Jet/wind? Northermal emission?

21. Settling: bimodal grain size distribution Wilner et al. 2005 Small + 5-7mm Weidenschilling 1997 ~ 1/R

22. Inner disk clearing • Weak or absent near-IR excess in TW Hya: clearing of inner disk regions • ‘Wall’ at ~ 4 AU – edge of outer disk • Inner disk: gas and small amount of micron-size dust • Large solids - with low near-IR opacity - may be in inner disk Wall emission, T~ 130K Calvet et al 2002

23. Inner disk clearing • Tidal truncation by planet • Hydrodynamical simulations+Montecarlo transfer – SED consistent with gap created and maintained by planet – GM Aur: ~ 2MJ at ~ 2.5 AU – Rice et al. 2003 SED depends on mass of planet (and Reynolds number) 21 MJ 1.7 MJ Planet formation may explain why/how inner disk eventually disappears (near-IR excess and accretion) 0.085 MJ 43 MJ

24. Photosphere Inner disk clearing: planet(s)? Transitional disks Taurus median • Wall of optically thick disk = outer edge of gap at a few AU • Inner gas disk with minute amount of small dust – silicate feature but little near IR excess, T= Tthin wall Bryden et al 1999 , Bergin et al 2004

25. The FUV - disk structure connection • Emission “bump” in STISspectra of disks in transition • lack of spatial extent suggests this is inner disk emission • Bergin et al 2004

26. Electron Impact Excitation of H2? (fast e’s due to X-rays) Ly  pumped H2 Emission + • link between X-ray and UV radiation -- evidence for internally generated UV field • Gas in inner disk – planet forming region • JN’s talk Bergin et al 2004 models of H. Abgrall and E. Roueff

27. Inner disk clearing Spectra from IRS on board SPITZER TW Hya, ~ 4 AU ~ 10 Myr CoKu Tau 4, ~ 10 AU ~ 2 Myr No inner disk, WTTS Inner disk Forrest et al. 2004; D’Alessio et al. 2005 Uchida et al. 2004

28. Inner disk clearing CoKu Tau 4, wall at ~ 10 AU No inner disk, no accretion, no near-IR excess Planet-disk system with planet mass of 0.1 Mjup for CoKu Tau 4 Quillen et al. 2004 photosphere D’Alessio et al. 2005

29. Summary • Progress in understanding disk evolution in 1 – 10 Myr range • Good handle on WHEN, begining to understand HOW • SPITZER data crucial • Disks evolve accreting mass onto star and dust growing and settling to midplane • Accumulation of planetesimals begins at midplane, followed by gas accretion onto protoplanet • Giant planet(s) begins to form, gap, inner disk into star • What happens to material in outer disk • Theoretical timescales • Mass dependence

30. Disks around intermediate mass stars dissipate faster Hernandez et al 2005

31. Mass accretion rate vs stellar mass Muzerolle et al 2004