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Mark Booth
(Pontificia Universidad Católica de Chile)
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What is a Debris Disc?
Other stars are surrounded by planetesimals similar to our asteroids, KBOs and comets.
What is a Debris Disc?
Other stars are surrounded by planetesimals similar to our asteroids, KBOs and comets.
Collisions between planetesimals, rotational break-up and sublimation of comets creates dust.
What is a Debris Disc?
Where does it come from?
Williams & Cieza 2011
The Nice Model of the Solar System Giant planets migrate due to interactions with
planetesimals. When Jupiter and Saturn cross their mutual 2:1 resonance,
the eccentricities of the giant planets are greatly increased and so is the impact rate on the Moon.
Gomes et al., 2005; Tsiganis et al., 2005; Morbidelli et al., 2005
The history of the Solar System’s debris disc (Booth et al. 2009)
Peak seen at 24µm for a brief period at time of scattering event.
Lack of decline in 70µm means LHB like events are rare, happening in <12% of systems.
Planet-Disc Interaction Stats
400 simulations with:
Terrestrial embryos + planetesimals
3 giant planets
Outer disc of planetesimals
Planetary dynamics followed for 200 Myr.
Raymond et al. 2011, 2012
Correlation between low mass planets and bright debris discs.
Inner Edge
Planets have a chaotic zone within which particles are unstable and will be removed dynamically on short timescales.
This is dependent on the position (Wisdom 1980) and eccentricity (Mustill & Wyatt 2011) of the particles.
Eccentric Ring Eccentric planets induce a forced
eccentricity in planetesimals.
Eccentric rings are seen around a number of stars including Fomalhaut, HR 4796, HD 202628, zeta2 Ret.
This led to the discovery of Fom b – although this is now none to not be the main perturber in the Fomalhaut system (Kalas et al. 2013, Beust et al. 2014, Pearce & Wyatt 2015).
Faramaz et al. 2014
Clumps?
• Discovered by IRAS. • Resolved at 24 µm with Spitzer. (Su et al. 2009) •
Discovered by IRAS. (Sadakane & Nishida 1986)
Resolved at 24 µm with Spitzer. (Su et al. 2009)
Warm component also detected.
Planets are expected to induce clumps in debris discs.
The clumps will be seen differently at different wavelengths.
(see e.g. Wyatt 2006)
Clumps?
• Discovered by IRAS. • Resolved at 24 µm with Spitzer. (Su et al. 2009) •
Discovered by IRAS. (Sadakane & Nishida 1986)
Resolved at 24 µm with Spitzer. (Su et al. 2009)
Warm component also detected.
CSO (350 µm) Patience et al. (2011)
SMA (880 µm) Hughes et al. (2011)
Resolved Discs – DEBRIS Survey ~36 resolved discs in the DEBRIS sample.
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Resolved Discs Around A Stars Correlation with
luminosity is seen
Lines show expected ratios for simulated discs
The difference between the observed and expected ratios suggests the real discs have size distributions and/or compositions different to what is expected
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Booth et al. 2013
Gamma Doradus
Both a two component model and wide disc model are consistent with the data.
Broekhoven-Fiene et al. 2013
l=70 microns l=100 microns l=160 microns
Star
background object
background object ?
background object 60 AU
Lestrade et al., 2012
Mass = 0.2 Msolar Distance = 6.23 pc [Fe/H] = -0.25 Age = 2-8 Gyr Planets: 4 (at least)
Inclination of 45 deg makes planet masses small enough for stability in the orbits (Mayor et al. 2009) Disc size increases with lambda, suggesting a wide belt. Cold component extends to 60 AU at least.
M-star GJ 581
Disputed
Cold outer belt Tentative warm
inner belt
26-60 AU
61 Virginis
• 30-350 AU disc • 3 planets between 0.05 AU and 0.5 AU (Vogt et al. 2009)
Obs
Model
70μm 160μm 100μm
Wyatt et al. 2012
Nearest 60 G stars
Consider unbiased sample of nearest 60 G stars (Phillips et al. 2010). 11 have detected planets: 5 high-mass planet systems (at least one planet has Mpl>Msaturn) None have debris, consistent with debris and planets being uncorrelated (2/12 of nearest 120 G stars with high-mass planets have disks) 6 low-mass planet systems (all planets have Mpl<Msaturn) 4 have debris, 1 of the undusty systems has M4 companion at 210AU. As ~15% normal stars have detectable debris, ≥4 out of 6 is 1% event
Small number stats, but this is first hint that systems with only low-mass planets (detectable in current RV surveys) are preferentially dusty
Wyatt et al. 2012
HR 8799
First multi-planet system discovered through direct imaging. (Marois et al. 2008, 2010).
HR 8799 Matthews et al., 2014
HR 8799 Booth et al. in prep
Image is a non-detection showing that the disc must be broader in the sub-mm than we previously thought.
Signal in the visibilities can give us constraints on the geometry.
SONS JCMT Legacy Survey
450µm 850µm
Booth et al. in prep
Wide Disks (>55 AU extent)
Narrow Belts (20-30 AU extent)
Possible disc “types”: (e.g. Kalas et al. 2006)
1. Do these trace fundamentally different distributions of underlying planetesimal population?
2. Are these different stages of debris disk evolution, or fundamentally different, long lived architectures?
Paul Kalas
2012-03-22
ALMA Debris Disc Observations
Fomalhaut Boley et al. 2010
AU Mic Macgregor et al. 2013
Beta Pic Dent et al. 2014
Systems with known planets and debris
HR 8799 (PI: Jordán) New data in band 6
on its way.
Predicted to look something like this.
Will give us much better constraint on inner edge.
Epsilon Eridani (PI: Jordán) Closest known
extrasolar debris disc.
RV planet known at 3 AU (Hatzes et al. 2000).
Right shows MAMBO image from Lestrade & Thilliez 2015.
We have one pointing at the north ansae of the disc.
HD 95086 (PIs: Booth & Su) Directly imaged
planet known at 62 AU (Rameau et al. 2013).
Right shows simulated ALMA image.
Disc has similar dimensions to HR 8799 (Moór et al. 2013)
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