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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. - PowerPoint PPT Presentation
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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