Evolution of protoplanetary disks N Calvet SAO C

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)

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

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)

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

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

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

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

Evolution of mass accretion rate for Classical T Tauri stars (~ K 5 -M 3) Viscous evolution - Gas . 50. 23. 12 Hartmann et al. (1998), Muzerolle et al. (2001), Calvet et al. (2005) Fraction of accreting objects decreases with time (LAH talk) What stops accretion?

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

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

Decrease of excess emission with age 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 Sicilia-Aguilar et al 2005 Taurus median Phot

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

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

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

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 surface Calvet et al 1991; Meyer et al 2000 SEDs -> large grains Grain Growth and Settling Forrest et al 2004

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 D’Alessio et al 2005 Furlan et al 2005

Settling of solids toward midplane Depletion of upper layers: upp/ st Furlan et al. 2005

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

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

Settling of solids: TW Hya 3. 5 cm flux ~ constant => Dust emission Jet/wind? Northermal emission? Wilner et al. 2005

Wilner et al. 2005 Settling: bimodal grain size distribution Small + 57 mm Weidenschilling 1997 ~ 1/R

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~ 130 K Calvet et al 2002

Inner disk clearing • Tidal truncation by planet • Hydrodynamical simulations+Montecarlo transfer – SED consistent with gap created and maintained by planet – GM Aur: ~ 2 MJ 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

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

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

Ly pumped H 2 Emission + Electron Impact Excitation of H 2? (fast e’s due to X-rays) Bergin et al 2004 models of H. Abgrall and E. Roueff • link between X-ray and UV radiation -- evidence for internally generated UV field • Gas in inner disk – planet forming region • JN’s talk

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

Inner disk clearing Co. Ku Tau 4, wall at ~ 10 AU No inner disk, no accretion, no near-IR excess photosphere D’Alessio et al. 2005 Planet-disk system with planet mass of 0. 1 Mjup for Co. Ku Tau 4 Quillen et al. 2004

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

Disks around intermediate mass stars dissipate faster Hernandez et al 2005

Mass accretion rate vs stellar mass Muzerolle et al 2004