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The Architecture of Planetary Systems Revealed by Debris Disk Imaging

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The Architecture of Planetary Systems Revealed by Debris Disk Imaging Cambridge Planet-Disk Connection Paul Kalas © 2006 The architecture of planetary systems revealed by debris disk imaging Paul Kalas University of California at Berkeley Collaborators: James Graham, Mark Clampin, Brenda Matthews, Mike Fitzgerald, Geoff Bower, Eugene Chiang, et al. Outline 1. Show the rapid progress of debris disk imaging. 2. Present new HST polarization results for AU Mic. 3. Discuss Fomalhaut’s Belt and evidence for a planetary system. 4. Review more disks and suggest some ideas regarding the origin of their architecture. Cambridge Planet-Disk Connection Paul Kalas © 2006 The Coronagraph: Imaging follow-up to IR excess stars Kalas et al. 2004 Cambridge Planet-Disk Connection Paul Kalas © 2006 First detection of the solar corona without a lunar eclipse (1932) Voyager 2 reaches Saturn (1981) Bernard Lyot (1897-1952) Brad Smith (head of Voyager imaging team) Cambridge Planet-Disk Connection Paul Kalas © 2006 Introduction: Vega Phenomenon Direct Image of the β Pic Dust Disk as early as 1983 Smith & Terrile 1984 Beta Pic was the Rosetta Stone Debris Disk for 15 years >300 refereed papers Cambridge Planet-Disk Connection Paul Kalas © 2006 Introduction: Vega Phenomenon 0.5 µm 2.2 µm 10-20 µm 850 µm β Pic Vega Fomalhaut 1998 see http://www.disksite.com ε Eri HR 4796A HD 141569 Resolved images of dust structure linked to unseen planets Cambridge Planet-Disk Connection Paul Kalas © 2006 2006 Cambridge Planet-Disk Connection Paul Kalas © 2006 2006 Cambridge Planet-Disk Connection Paul Kalas © 2006 AU Mic - Past AU Mic (GJ803): Early evidence for circumstellar dust: Tsikoudi 1988, "Flare stars detected by the Infrared Astronomical Satellite" Mathioudakis & Doyle 1991, "Active M-type stars from the ultraviolet to the infrared" One of the closest flare stars: Distance = 9.9 pc SpT = M1Ve Mass = 0.5 Msun Radius = 0.56 Rsun Teff = 3500 K Luminosity = 0.1 Lsun Mv = 8.8 mag Period = 4.865 d Avg. Mag. Field: B = 4000 G Ha Equivalent Width = 8.70 Quiescient X-ray flux: log10 (Lx) = 29.8 erg/s Age: Young Cambridge Planet-Disk Connection Paul Kalas © 2006 AU Mic: Stellar Properties beta Pic Moving Group Kalas & Deltorn (1999, unpublished) Barrado y Nav ascues 1999 Zuckerman, Song, et al. 2001 Cambridge Planet-Disk Connection Paul Kalas © 2006 AU Mic - Present AU Mic Discovery Image: Kalas, Liu, & Matthews 2004 R-band, UH 2.2 m telescope, 0.4"/pix, 900 s, seeing FWHM = 1.1" Cambridge Planet-Disk Connection Paul Kalas © 2006 Follow-up high resolution imaging Metchev et al. 2005 (Keck NIR), Krist et al. 2005 (HST, visible), Liu 2004 (Keck, NIR) • Radius: 7.5 - 150 AU • Width: 2.5 - 3.5 AU within 50 AU • Dust depletion beyond the ice sublimation boundary • Blue scattering throughout the disk Krist et al. 2005 Cambridge Planet-Disk Connection Paul Kalas © 2006 AU Mic Origin of the Disk: Grain lifetimes as a function of radius from Backman & Paresce 1993: Kalas et al. 2004 Poynting-Robertson Drag Timescale Collision Timescale Sublimation Timescale Most of the grains seen in the discovery image are fragments of larger objects, very little mass <67 AU: 0.1 mm grains have spiraled into the star in 8 Myr has been removed from the <20 AU: 1.0 mm grains have spiraled into the star in 8 Myr system. 100 AU: Collision timescale is 1.8 Myr >200 AU:Collisionally unevolved disk, pristine material Cambridge Planet-Dis k Connection Paul Kalas © 2006 AU Mic Origin of the Disk? Plavchan, Jura, & Lipscy 2005 Augereau et al. 2006 (in press) radiation pressure / gravity stellar wind / gravity Cambridge Planet-Disk Connection Paul Kalas © 2006 AU Mic’s Blue Color: “Birth Ring” Theory Strubbe & Chiang (2006) 100 x solar mass loss rate projected radius Cambridge Planet-Disk Connection Paul Kalas © 2006 AU Mic - Present How do disks evolve differently around an A star and an M star? radiation pressure blowout stellar wind blowout Kalas et al. 2004 Cambridge Planet-Disk Connection Paul Kalas © 2006 HST ACS: HRC Polarization J. R. Graham, P. Kalas, & Matthews 2006, submitted to The Astrophysical Journal F606W ACS/HRC Cambridge Planet-Disk Connection Paul Kalas © 2006 HST ACS: HRC Polarization Simultaneous fit to optical SB profile and polarization Need high p, and large g. inner radius ~40 AU, outer radius ~200 AU. Small grains give high p, but scatter too If astronomical isotropically. silicates, P = 94 ± 6% If ice, P = 91 ± 9% Cambridge Planet-Disk Connection Paul Kalas © 2006 Is this what we see around AU Mic? No, comet grains have porosity ~70% after sublimation of volatiles. Moreover, AU Mic grains originate far beyond the ice sublimation radius. More likely, particle coagulation via ballistic cluster- cluster aggregation. To avoid restructuring and compactification, the upper size limit of the parent bodies is ~10 cm. Wurm & Blum 1998 Cambridge Planet-Disk Connection Paul Kalas © 2006 Beta Pic Polarization How does AU Mic compare to Beta Pic? Artymowicz 1997 Cambridge Planet-Disk Connection Paul Kalas © 2006 Keck Observatory with Adaptive Optics (Fitzgerald et al. 2006) J, H, K Cambridge Planet-Disk Connection Paul Kalas © 2006 AU Mic: Fitting the SED & Color simultaneously Two component model disk (Mie scattering, Monte Carlo radiative transfer code; Duchene et al). Polarization Compact silicates (Drain & Li 2001) do not work. V-band (HST) Mathis & Whiffen (1989) model works well. Highly porous aggregates of silicates, carbonaceous and icy elements. H-band (Keck) Polarization too high in this simple model. Non- spherical grains? Minimum grain size varies Fitzgerald et al. 2006 with radius? Cambridge Planet-Disk Connection Paul Kalas © 2006 Fomalhaut Stapelfeldt et al. 2004 ring eccentricity in model = 0.07 planet orbit: a = 40 AU, e = 0.15 Marsh et al. 2005 Model fit using Spitzer (24, 70, 160 µm) & 350 µm image suggests 8 AU center of symmetry offset. Planet a = 86 AU, e = 0.07, M > 1 Earth if the inner ring boundary is the location of a 2:3 MMR (Neptune :CKB) Cambridge Planet-Disk Connection Paul Kalas © 2006 HST ACS planet search Fomalhaut • Semi-major axis: a =140.7± 1.8 AU • Semi-minor axis: b = 57.5 ± 0.7 AU Kalas, Graham & Clampin • PA major axis: 156.0˚±0.3˚ 2005, Nature, Vol. 435, pp. 1067 • Inclination: i = 65.9˚± 0.4˚ • Projected Offset: 13.4 ± 1 AU F814W: 80 min., 17 May, 02 Aug, 27 Oct, 2004 • PA of offset: 156.0˚ ± 0.3˚ F606W: 45 min., 27 Oct. 2004 • Deprojected Offset f = 15.3 AU 25 mas / pix, FWHM = 60 mas = 0.5 AU • Eccentricity: e = f / a = 0.11 orbital period at 140 AU = 1200 yr Cambridge Planet-Disk Connection Paul Kalas © 2006 HST ACS planet search Asymmetric Scattering Phase Function Kalas, Graham & Clampin 2006 |g| = 0.2 Zodiacal Light = +0.2; Forward Scattering Median size ~30 microns (blowout size for Fomalhaut is 7 microns). Integrated light from model gives a total grain scattering cross section of 8.7 x 1025 cm2. Assume 30 mm sized particles and density 2.5 g cm-2, albedo = 0.1, then belt mass is 0.09 Lunar mass --> 17 times smaller than inferred from sub- mm data. Albedo may be much lower --> a dark belt similar to the rings of Uranus. Model subtraction emphasizes inner dust component, 20% of the peak flux in the main belt. Cambridge Planet-Disk Connection Paul Kalas © 2006 HST ACS planet search Evidence for a planetary system: Center of symmetry offset Kalas, Graham & Clampin 2006 Wyatt et al. 1999 G. Schneider, STIS How Observ ations of circumstellar disk asymmetries can rev eal hidden planets:Pericenter glow and its application to the HR 4796A disk Wyatt, M.C. et al. 1999, ApJ, 527, 918 • Particle eccentricity composed of a p rop er (or free) eccentricity, inherent to the particle, and a forced eccentricity due to a perturber. The pericenter also has a free and a forced component. • The orbital distribution of particles with common forced elements will be a torus with center, C, offset from the stellar position, S. • The forcing is due to an eccentric companion that could be either inside or outside the belt. • Infer offset 2 AU for HR 4796A • Similarly offset = 0.01 AU for Zodiacal dust disk (e.g. Kelsall et al. S = stellar position 1998). D = center of particle orbit • External eccentric perturber can produce the same center of C = center of precession circle symmetry offset, but not the sharp inner disk boundary. P = pericenter of a particle orbit DP = a, semi-major axis of a particle orbit wf = direction of forced pericenter SD = a e SC = a eforced CD = a eproper Torus inner radius = a (1 - eproper) = 133 AU Torus outer radius = a (1+ eproper) Cambridge Planet-Disk Connection Paul Kalas © 2006 Kalas, Graham & Clampin 2006 Radial cut along 10˚ segement Q2 (apastron), in the illumination corrected image; cut traces the material surface density of the structure rather than its brightness. Model has a hard edge inner edge, but the integration in the line of sight and the 7 AU vertical scale height means that the edge will not appear sharp in the sky projection. Quillen (2006) argues that the steepness of the edge is consistent with a Neptune to Saturn-mass object at 119 AU semi-major axis. Cambridge Planet-Disk Connection Paul Kalas © 2006 HST ACS planet search Evidence for planets: sharp inner edge Kuiper Belt dust models by Moro-Martin & Malhotra 2002 radial cuts planets 1) Dust produced by KBOs no planets a=35-50 AU, i = 0˚-17˚ 2) 1-40 mm, r = 2.7 g cm-3 & 3-120 mm, r =1 g cm-3 3) 7 planet, or no planets 4) Solar gravity, RP, P-R drag, solar wind drag.
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