Johan Olofsson MPIA Heidelberg

Planetary formation in
transition and debris disks
Johan Olofsson
MPIA Heidelberg
Benisty, M.; Henning, Th.; Augereau, J.-C.; Le Bouquin, J.-B.

Motivation

Giant & telluric planetary formation
‣ Giant planetary formation (Olofsson et al. 2013a)
‣ The transition disk around TCha: how to sculpt a disk
‣ I’m confused, is there a planet in the end
‣ Terrestrial planetary formation (Olofsson et al. 2013b)
‣ The warm debris disk around HD 113766 A
‣ The origin of the transient dust: a massive collision

The transition disk around TCha
‣ Main characteristics of TCha:
‣ Solar-type star (G8), 7 Myr old
‣ Far-IR excess (cold dust)
‣ Near-IR excess (warm dust)
‣ Lack of mid-IR (no dust)

The transition disk around TCha
‣ Fact: the disk is dissipating. Question: how
‣ (hint: there is a strong near-IR excess)
‣ Circumbinary disk Single star (optical spectroscopy)
‣ Grain growth Would affect the innermost regions first
‣ Photo-evaporation Same as above
‣ Gap opened by a planet
‣ We need spatially resolved observations !

The power of interferometry
‣ Near- & mid-IR interferometry at the VLTI
‣ High angular resolution: few milli-arcsec (1 mas, 0.1 AU @ 100 pc)
‣ Near-IR: sensitive to warm dust
‣ Let’s use all possible VLTI facilities !
‣ AMBER (Olofsson et al. 2011)
‣ PIONIER, MIDI, NaCo/SAM (Olofsson et al. 2013a)
‣ MCFOST = SED + raytraced images (V 2 , closure phases)
‣ Multi-techniques, multi-wavelength, multi-resolution

The inner disk
‣ Narrow disk: 0.07-0.11 AU
‣ High temperatures: sublimation of smallest silicates (1500 K)
‣ Large scale height: H/R = 0.2
‣ High temperature gas
‣ (Thi et al. 2011)
‣ Warped disk (optical variability
‣ Schisano et al. 2009)
‣ ISAAC proposal: time monitoring

The outer disk
‣ Most likely narrow: 12-25 AU (Cieza, Olofsson et al. 2011)

The outer disk
‣ Most likely narrow: 12-25 AU (Cieza, Olofsson et al. 2011)
SED Pionier - V 2 NaCo SAM - V 2
MIDI
Pionier - CP

The importance of the field-of-view
‣ The outer disk is in the Pionier, MIDI and SAM field-of-view
‣ Over-resolved, extended emission: drop in V 2 at short baselines
‣ Constraints on the outer disk, even with Pionier

A candidate companion
‣ Huélamo et al. (2011): NaCo/SAM closure phases w/ binary model
‣ L’-band detection, distance of 6.7 AU (in the gap), mass < 80 M Jup
‣ Closure phases: departure from centro-symmetry
‣ Anisotropic (forward) scattering: asymmetric surface brightness

A candidate companion
‣ Equivalent goodness of fit for the disk and binary models
‣ Assumptions made are not equivalent
Companion model
T Cha
MCFOST model
5
5
5
v (meters)
0
v (meters)
0
v (meters)
0
−5
−5
−5
−1 deg −0.5 deg 0.5 deg 1 deg
−1 deg −0.5 deg 0.5 deg 1 deg
−1 deg −0.5 deg 0.5 deg 1 deg
5
0
−5
5
0
−5
5
0
−5
u (meters)
u (meters)
u (meters)
‣ Companion has to be unambiguously detected

Hints for a companion
‣ Large gap in the disk: several AU
‣ A narrow outer disk (12-25 AU), why
‣ Herschel PACS & SPIRE observations (Cieza, Olofsson et al. 2011)
‣ Pressure maximum caused by a 1-15 M Jup planet
‣ Pile-up of mm-sized grains: good far-IR emitters
‣
Pinilla, Benisty & Birnstiel (2012)

Giant planetary formation in TCha
‣ Narrow inner disk at the sublimation temperature
‣ Large gap: room for one or more planet of a few M Jup
‣ Still to be detected
‣ Narrow outer disk: consequence of planet-disk interactions
‣ May appear truncated in the population of mm-sized grains
‣ Could be more extended for other grains sizes
‣ Need for direct imaging: ALMA, NaCo/ADI !

Debris disk
Final product of star formation
Kuiper-belt like
Reservoir of planetesimals
Cold dust (50 K)
100s of known objects
Optically thin
Typical ages > 10-20 Myr

Warm debris disk
Final product of star formation
Inner belt
Kuiper-belt like
Reservoir of planetesimals
Cold dust (50 K)
100s of known objects
Warm dust (500 K)
Rare objects
Optically thin
Typical ages > 10-20 Myr

Warm debris disk around HD 113766 A
‣ High IR luminosity associated with the disk
‣ Not a steady-state evolution of the disk: transient dust
‣ Detection of emission features in IRS spectrum
‣ Warm, small silicate dust grains
‣ Origin of the dust:
‣ Massive collision
‣ Outer dust belt “feeding” the inner regions
‣ (e.g., comets, Beichman et al. 2005, Bonsor et al. in prep)

Methodology
‣ Herschel/PACS observations: cold dust
‣ VLTI/MIDI observations: warm dust
‣ DEBRA code (Olofsson et al. 2012):
‣ SED modeling, spectral decomposition & raytraced images

One or two dust belts
‣ One dust belt: extended disk (0.4-50 AU)
‣ Severely under-predict the MIDI observations

One or two dust belts
‣ Two dust belts: 0.6-1 AU & 9-13 AU
‣ Good match to all the observations
‣ Limitations of SED modeling !

Origin of the dust
‣ Massive collision
‣ Outer dust belt “feeding” the inner regions (e.g., comets)

Origin of the dust
‣ Comet “outgasing” radius
‣ r ~ 3.3 AU for a 4.4 L ⦿ star (Bonsor et al. in prep)
‣ MIDI data: r < 1 AU
‣ Dust composition: crystalline olivine grains
‣ Enrichment in Fe compared to Mg (unusual petrology)
‣ Possible explanation: differentiated planetesimals
‣ (e.g., Nakamura et al. 2011; de Vries et al. 2012)
‣ Catastrophic collision between such planetesimals

Origin of the dust
‣ HD 113766 A: 10-16 Myr old
‣ Timeframe for telluric planetary formation (Kenyon & Bromley 2006)
‣ Stirring by large planetesimals: highly unstable period of time
0.7-1.3 AU
0.4-2 AU

Giant & telluric planetary formation
‣ The case of TCha
‣ One (or more) planet(s) to be unambiguously detected in the gap
‣ Perfect laboratory to test planet formation theories
‣ Need for high resolution direct imaging
‣ The case of HD 113766 A
‣ Aftermath of a collision between differentiated planetesimals
‣ Need to spatially resolve the outer belt

Take away messages
‣ SED modeling is awesome, until you obtain spatially resolved data
‣ ➔ Study the dust
‣ ➔ Study the disk
‣ ➔ Planet-disk interactions
‣ ➔ Study planets
‣ Dust mineralogy never fails to provide valuable constraints
‣ (e.g., Olofsson et al. 2009; 2010, 2012, 2013b)
(shameless advertising, on the last slide)