Evolution of protoplanetary disks

C. Briceno (CIDA)P. D’Alessio (UNAM)J. Hernandez (CIDA)L. Hartmann (SAO)J. Muzerolle (Steward Observatory)A. Sicilia-Aguilar (SAO)

N. Calvet (SAO)

• Disks evolve from optically thick dust+gas configurations to mostly solids debris disks

Disk evolution

Characteristic timescales Physical processes

HK Tau, Stapelfeldt et al. 1998

• 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)

Disk evolution

Gas: accretion onto starInner 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

Magnetospheric flow

Broad emission lines (HBr,etc.)formed in magnetospheric flow

Muzerolle et al. 1998a,b, c, 2001

BP Tau

Model

Redshiftedabsorption

Redshifted absorption if right inclination

Evidence for magnetospheric accretion

Calvet & Gullbring 1998; Gullbring et al. 2000; Calvet et al. 2004

Excess emission/veiling: consistent with accretion shock emission

Accretion shock

Excess

Veiling

Accretion luminosity and mass accretion rate

Gullbring et al. (1998)

Excess emission over photosphere ~ Lacc = G M (dM/dt) / R

Evolution of mass accretion rate for Classical T Tauri stars (~ K5-M3)

Hartmann et al. (1998), Muzerolle et al. (2001), Calvet et al. (2005)

Fraction of accreting objects decreases with time (LAH talk) What stops accretion?

.50 .23 .12

Viscous evolution - Gas

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

Calvet et al. 2005

Taurus, 1-2 Myr

Ori OB1b, 3-5 MyrBriceno et al 2005

Near-IR colors of older population much lower

Decrease of excess emission with age

SEDs of stars in Tr 37 ~ 3 MyrIRAC dataWeaker than median of

TaurusAccreting stars (C)

without excessesWeak TTS (W) with excess

Taurus median

Phot

Sicilia-Aguilar et al 2005

Present picture of inner diskNear-IR emission mostly from wall at dust destruction

radius

Excess decreases with age

•large contribucion from wall to near-IR•decrease of dM/dt or•decrease of wall emitting area => height

Art by Luis Belerique& Rui Azevedo

Grain growth in disks

Median SED of Taurus

ISM

amax = 1mm

D’Alessio et al 2001

quartiles

Models with dust and gas distributed uniformly

No silicateemission

Spitzer/IRS spectra of T Tauri stars

silicate featureemission –>small grains

Forrest et al 2004

SEDs -> large grains

Grain Growth and Settlingsurface

Hot upper layers of optically thick inner disk

Calvet et al 1991;Meyer et al 2000

Midplane of optically thin outer disk

Settling of solids towards the midplane: effects on SED

Furlan et al 2005

•Lower opacity of upper layers•Decrease capture of energy•Lower T, less emission

D’Alessio et al 2005

Depletion of upper layers: upp/st

Settling of solids toward midplane

Furlan et al. 2005

Depletion of upper layers: upp/st

Settling of solids toward midplane

Furlan et al. 2005

diameter range of i’s

Dust growth and settling

•As disk ages, dust growths and settles toward midplane as expected from dust evolution theories

Weidenschilling 1997

Upper layers get depleted

t = 0

Population of big grains at midplane

Observations agree with expectations, (although problem with timescales)

Settling of solids: TW Hya

3.5 cm flux ~ constant =>Dust emission

Wilner et al. 2005Jet/wind?Northermal emission?

Settling: bimodal grain size distribution

Weidenschilling 1997

Wilner et al. 2005

Small + 5-7mm

~ 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

Calvet et al 2002

Wall emission, T~ 130K

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)

0.085 MJ

1.7 MJ

21 MJ

43 MJ

Planet formation may explain why/how inner disk eventually disappears (near-IR excess and accretion)

Inner disk clearing: planet(s)?

●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

,Bergin et al 2004

Taurus median

Bryden et al 1999

Transitional disks

Photosphere

wall

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

• link between X-ray and UV radiation -- evidence for internally generated UV field

• Gas in inner disk – planet forming region

• JN’s talk

models of H. Abgrall and E. Roueff

Electron Impact Excitation of H2? (fast e’s due to X-rays)

Ly pumped H2 Emission +

Bergin et al 2004

Inner disk clearing

Uchida et al. 2004Forrest et al. 2004;

D’Alessio et al. 2005

Spectra from IRS on board SPITZER

CoKu Tau 4, ~ 10 AU~ 2 Myr

TW Hya, ~ 4 AU~ 10 Myr

Inner disk

No inner disk, WTTS

Inner disk clearing

D’Alessio et al. 2005

CoKu Tau 4, wall at ~ 10 AUNo inner disk, no accretion, no near-IR excess

Planet-disk system withplanet mass of 0.1 Mjup

for CoKu Tau 4Quillen et al. 2004

photosphere

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