Structure in Debris Disks
Jane Greaves SUPA, St Andrews resolved disk examples
around 10 Myr beta Pic, HR 4796 A, HD 141569, AU Mic
a few 100 Myr Vega, Fomalhaut, HD 139664, HD 107146
~1 Gyr onwards epsilon Eri, eta Crv, HD 53143, tau Ceti a rogues gallery
SCUBA images, 1998-2004 types of star
first discoveries mainly A-stars luminous, short-lived emphasis now on F/G/K… potential Solar analogues past/future compared to Solar System at 4.5 Gyr M stars, brown dwarfs? kinds of structure
extent cavity halo offset warp spiral clump epochs
10 Myr: end of 'proto-planetary disk' large, massive disks… still some gas… shaped by newly-formed giant planets? 100's Myr: completing terrestrial planets debris frequent… planet migration? … cataclysms? Gyr's: main epoch for Solar analogues steady grinding … impacts on planets relevance to planets
zones where planetesimals grew
late-growing Plutos?
perturbations: Neptunes and up
very distant planets typical or atypical?
NB, the resolved examples are at the large, bright end of the population 10" at 10 pc ↔ 100 AU many times Kuiper Belt dust MANY more unresolved examples… and NO debris seen for most stars hence, potentially odd view of ease of forming distant planets, etc. HD 30495 with SCUBA G3 V star at 13 pc ~10 Myr epoch
well known A-stars beta Pic HD 141569 HR 4796 A
AU Mic M0 star in beta Pic association beta Pictoris huge disk: >1000 AU warped: multiple planes outer rings: stellar flyby? multiple belts… - herded by planets? mid-IR asymmetry… - resonance / break-up? distant submm feature 'falling evaporating bodies' gas (atomic, ionic… C-rich)
Golomowski et al. 2006; Telesco et al. 2005; Okamoto et al. 2004; Kalas et al. 2000; Holland et al. 1998;Smith & Terrile 1984 AU Mic vs. beta Pic: smaller disk (r ~ 200 AU) several clumps similar gas-to-dust ratio? up to ~ 5:1 surprisingly similar to beta Pic dynamical times should
differ (2 vs. 0.5 Msun) Kalas Liu & Matthews 2004; Liu 2004; Metchev et al. 2005; Roberge et al. 2005 HR 4796 A
another luminous star in the TW Hya group, ~10 Myr old, A0 V but TW Hya (K8 V) is counted as a T Tauri star forced asymmetries suggest perturbing planets
Wyatt et al. 1999; Scheider et al. 1999; Koerner et al. 1998; Jayawardhana et al. 1998 HD 141569
another arguably pre-ms system B9.5 V, ~5 Myr
rdisk > 1000 AU disk spirals due to: external companion star…or internal but very distant planet? (~200 AU)
Wyatt 2005; Clampin et al. 2003; Weinberger et al. 1999 summary: young systems
complex dynamics going on remnant gas involved? epoch of building giant-planets over? disk central regions cleared but systems probably still evolving no smooth disks: planetary perturbers very distant planets surprising? know v. little about Solar analogues! Dent, Greaves & Coulson 2005: gradual shrinking of gas disks up to ~ 20 Myr? summary: young systems
complex dynamics going on remnant gas involved? epoch of building giant-planets over? disk central regions cleared but systems probably still evolving no smooth disks: planetary perturbers very distant planets surprising? know v. little about Solar analogues! 100's Myr epoch
A-stars: Vega (A0, 350 Myr) Fomalhaut (A3, 300 Myr) Sun-like stars: HD 139664 (F5, ~300 Myr) HD 107146 (G2, ~150 Myr) NB in clusters: ~20% debris rate? major epoch of planetesimal collisions? Gorlova et al. 2004, Stauffer et al. 2005: B5-K1 debris disks at 100 Myr in M47& the Pleiades…
… F2-G1 disks in the Ursa Major group, ~300-500 Myr Spangler et al. 2001 Vega archetype - but not typical structure? halo of blown-out grains (mid-IR)… to distinct clumps (mm) effects of planetary migration, stirring of planetesimals, and trapped vs escaping particles
Holland et al. 1998; Su et al. 2005; Wyatt 2003, 2006 choice of wavelength strongly affects what is seen (and interpreted)
850 microns
Marsh et al. 2006; Wilner et al. 2002; Koerner et al. 2001; Holland et al. 2003, 1998 Fomalhaut
unlike Vega no halo narrow ring system ~25 AU at 140 AU single distant clump suggests a planet at ~ 100 AU?
Kalas et al. 2005; Marsh et al. 2005; Stapelfeldt et al. 2004; Wyatt & Dent 2002; Holland et al. 2003, 1998 HD 139664 and HD 107146
F5 star with narrow belt: ~25 AU wide at 100 AU
Kalas et al. 2006
G2 star with wider belt Williams et al. 2004; > 55 AU wide at 150 AU Ardila et al. 2004 summary: 'terrestrial' epoch
gas-less disks… smaller and simpler narrow rings, big cavities, clumps many systems have debris ~ 50% for A stars… less for F/G/K? large dust masses: … cataclysms? completion of exo-Earths? identifiable resonances supporting presence of distant planets planet detection
outwards planet migration increases planetesimal collisions plus traps dust hence, plot position of planets… sensitive at tens of AU example: a Neptune- mass planet at 65 AU around Vega Marsh et al. 2006, from model of Wyatt (2003) Gyr epoch
A stars: ~ 1 Gyr on main sequence but a random nearby star typically a fraction of ~10 Gyr age of Galactic Disk resolved images only at 1 & 10 Gyr! none for Sun-like age but many exist…
Bryden et al. 2006 eta Crv
F2 V, ~ 1 Gyr old inclined ring, or ring with 2 clumps? plus hot dust near star
850, 450, 450 (high res.) - Wyatt et al. 2005 HD 53143
K1 V, 1 ± 0.2 Gyr wide ring similar to archetype epsilon Eri
Kalas et al. 2006 100 AU epsilon Eri
K2 V, 0.85 Gyr central cavity to ~30 AU multiple clumps only system with time- resolved motion
(a) 850 microns (b) 450 microns (+850 contours); Greaves et al. 1998, 2005 2-sigma rotation detection… nominally ~2.5 deg/year clumps dragged by planet at edge of cavity?
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Sim A Sim B 3.5 Sim C Sim D Sim E Observed 3
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0 -4 -2 0 2 4 Rotation rate (Degrees per year)
Poulton, Greaves & Cameron 2006 tau Ceti
G8 V, 10 Gyr 850μm most like Solar System in size but 20x dust flux of Kuiper Belt many more comets, at twice age of Sun no analogue to Size of Pluto’s orbit Jupiter… many
infalling comets? Greaves et al. 2004 summary: mature epoch
disks mostly larger than Solar System r ~ 100-150 AU (but biased) mostly comet (not asteroid) belts smoother than younger disks? also much dustier systems -4 Mdust > 10 MEarth (Mcomets > 1 MEarth) diverse sculpting by planets? not generally Doppler-planet systems Gyr dust levels
extrapolation of excesses: most Sun-like stars could be 2-5x duster than the Solar System
0.03 0.1 0.3 1 3 10 30 100% excess (bins x3)
10%
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excess (bins x2) 0.07 0.15 0.3 0.6 1.2 2.5 5 10 20 40
Solar trends
to first order every system ≠ every other system! little pattern emerges if grouped by age spectral type rotation companions / planets hence, no 'predictor' of outcome?? common features
rings, not filled disks also from SED's of unresolved systems not necessarily cleared by planets but many perturbed disks indicate planets at tens of AU… outwards migration? disks larger than Solar System typical descendants of T Tauri disks? metallicity
only known for ~Gyr Solar-analogues but clear influence on 'success' explain no-giant / many-comet systems, etc.
debris debris + planet hot Jupiter cool Jupiter no debris or planet 1.00
0.90
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cumulative function cumulative 0.30
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0.00 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 [Fe/H] future aims
more resolved examples & better S/N make sense of zoo basics of why dust is where identify resonances correctly time resolved imaging exploit rotation as planet detection tool bigger parameter space in models not just single matches to single systems ALMA JCMT
Survey speed × 5000 Resolution ×10
Herschel
Sensitivity × 10 – 1000 True image fidelity z=4 Quasar SOFIA
1mJy SCUBA z=2 Galaxy Vega disk SCUBA-2 Herschel VLA ALMA z=10 Galaxy LSTLSD Flux density 1μJy
HST NGST
1m 1mm 1μm Wavelength summary
huge advances via imaging prospects of understanding the planet connection! effects of debris on exo-Earths and life?
1984… 1998… 2010?