Some considerations on disk models Antonella Natta Osservatorio di Arcetri Schloss Ringberg, April 13-17, 2004

What is a protoplanetary disk ? A star A disk of gas (dominant in mass ) and dust (dominates the opacity) Mdisk << Mstar (but..) Material moves radially toward the star: accretion disk Schloss Ringberg, April 13-17, 2004

Schloss Ringberg, April 13-17, 2004 What is a disk model ? Which are the dominant physical processes (angular momentum transfer, ionization, heating, etc.) T, r, chemical composition, ionization fraction, etc. etc. in each point for gas and dust  a large range of (very high) density and temperature  very optically thick (RT)  dust is highly processed How all of this changes with time The environment is important (binaries, clusters, etc.) Everything is coupled Schloss Ringberg, April 13-17, 2004

Schloss Ringberg, April 13-17, 2004 Outline: A little history One (or two) examples Some comments Schloss Ringberg, April 13-17, 2004

Lyndell-Bell and Pringle 1974 The viscous a-disk Shakura and Sunyaev 1973 Lyndell-Bell and Pringle 1974 (Pringle ARAA 1981) Viscosity n = a Cs H Temperature TMacc1/4 R-3/4 Surface density S  R-3/4 a-1 r(R,z) = r(R,0) exp(-z2/2H2) There is a relation between Macc and n Question: what is the physical mechanism behind viscosity? Challenge: to account for the observed accretion rates Schloss Ringberg, April 13-17, 2004

Observed Macc in PMS Objects Macc decreases with Mstar Macc decreases with age r-Oph Taurus Cha Calvet et al. 2000 Muzerolle et al. 2003 Natta et al. 2004 Schloss Ringberg, April 13-17, 2004

Irradiated disks: the stellar radiation heats the disk Geometrically thin, optically thick (blackbody) disks: T~ 0.67 Tstar (R/Rstar) -3/4 Same SED (but different LD) for active and passive BB disks (most TTS have passive disks) Do models reproduce the observations? No parametric power-law disks: T  R-q, S  R-p Form Beckwith et al. 1990 Schloss Ringberg, April 13-17, 2004

Irradiated Flared Disks Kenyon & Hartmann 1987: Disks in hydrostatic equilibrium (between stellar gravity and thermal pressure along z) are flared (i.e., the opening angle increases with R) Calvet et al. 1994: Irradiated disks are hotter on the surface than in the midplane  emission features Chiang & Goldreich 1997: 2-layer approximation Schloss Ringberg, April 13-17, 2004

Irradiated Flared Disks They intercept a larger fraction of Lstar The temperature profile is flatter Shapes SEDs Emission features Nice range of temperatures for chemistry Schloss Ringberg, April 13-17, 2004

The story of the HAe SEDs and the inner rim High near-IR excess The 3 mm bump A ring on the sky Hillenbrand et al. 1995 Natta et al. 2001 Millan-Gabet et al. 2001 Dullemond et al. 2001 Schloss Ringberg, April 13-17, 2004

When all we have are few points on the SED: BD disks Flat or flared? Large or small silicates? Pascucci et al. 2003 All flavors, as TTS Mohanty et al., submitted Natta & Testi 2002 Schloss Ringberg, April 13-17, 2004

Grain growth, settling, planetesimals and planets All these processes occurr in PMS disks and change them (opacity, decoupling gas and dust, dynamical interactions, etc.) Observational tests are in their infancy very large grains (sand and pebbles) in the outer disks of many PMS stars (Calvet et al. 2002; Natta et al. 2004) gaps We may have underestimated significantly disk masses in PMS stars Schloss Ringberg, April 13-17, 2004

A never-ending discussion: disks or envelopes? What is an envelope? matter with a more spherically-symmetric geometry infalling envelopes (early phases) wind (if dusty) ? Important effects (due to scattering and emission) on the heating of the outer disk If the emission in the far-IR is very extended, it is likely to be due to an envelope One needs to worry on a case-by-case basis Schloss Ringberg, April 13-17, 2004

From BB disks to radiation transfer codes (DUST) 2-layers: features from the optically thin surface, approximate SEDs 1D: vertical temperature profile, scattering 2D: axially-symmetric structures (disk+envelopes,rims) 3D : spirals, vortices See Pascucci et al. 2004a,b for a banchmark study of several 2D and 3D RT codes Schloss Ringberg, April 13-17, 2004

What do we want to do with the RT codes? Predict observable quantities: SED Features Intensity maps Everything else How? Integrating radiation transfer into physical models (D’Alessio et al., Bell et al.) Using disk structure from “physical” models (e.g., S, grain properties, etc.) as an input for RT Schloss Ringberg, April 13-17, 2004

Grain growth, settling, planetesimals and planets Schloss Ringberg, April 13-17, 2004

Schloss Ringberg, April 13-17, 2004 The rho-Oph sample [Natta et al. 2002] ] [see also Pascucci et al. 2003] Schloss Ringberg, April 13-17, 2004

Schloss Ringberg, April 13-17, 2004 GY11 : a ~8-15 MJ object with a flared disk Schloss Ringberg, April 13-17, 2004 [Testi et al. 2002]

BDs are actively accreting: Broad Ha Macc from veiling (TTS) or by fitting Ha profiles with magnetospheric accretion models r-Oph CAM 032 [Muzerolle et al. 2003, Natta et al. 2004] Schloss Ringberg, April 13-17, 2004

Disks and accretion in TTS: A. Dutrey, 2001 Schloss Ringberg, April 13-17, 2004

First detections at mm wavelengths of two BDs in Taurus [Klein et al, ApJ submitted; SCUBA at JCMT] Disks models: Flat disk If flared, large inner hole and high rim [Pascucci et al, ApJ in press] Schloss Ringberg, April 13-17, 2004