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FOMALHAUT Review and evidence for a planetary system

FOMALHAUT Review and evidence for a planetary system. Paul Kalas University of California at Berkeley with support from NSF Center for Adaptive Optics NASA Origins Program STScI/AURA GO-9475, GO-9861, GO-9862, GO-10228 kalas (at) astron.berkeley.edu http://astron.berkeley.edu/~kalas.

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FOMALHAUT Review and evidence for a planetary system

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  1. FOMALHAUTReview and evidence for a planetary system Paul Kalas University of California at Berkeley with support from NSF Center for Adaptive Optics NASA Origins Program STScI/AURA GO-9475, GO-9861, GO-9862, GO-10228 kalas (at) astron.berkeley.edu http://astron.berkeley.edu/~kalas

  2. Introduction: Vega Phenomenon An early observation of a debris disk "The light at its brightest was considerably fainter than the brighter portions of the milky way... The outline generally appeared of a parabolic or probably elliptical form, and it would seem excentric as regards the sun, and also inclined, though but slightly to the ecliptic." -- Captain Jacob 1859

  3. Introduction: Vega Phenomenon Thermal IR excess from Zodiacal dust cloud ~150 K Leinert & Gruen 1990

  4. Introduction: Vega Phenomenon The Vega PhenomenonThe discovery of excess emission from main sequence stars at IRAS wavelengths (Aumann et al. 1984). Backman & Paresce 1993 "The Big Three"

  5. Introduction: Vega Phenomenon Direct Image of b Pic Dust Diskas early as 1983 Smith & Terrile 1984 Beta Pic was the Rosetta Stone Debris Disk for 15 years >300 refereed papers

  6. And how about Fomalhaut? Optical ground-based coronagraphy No detection. Kalas & Jewitt 1996  Pic would remain the flagship debris disk for 14 years

  7. Introduction: Vega Phenomenon ReplenishmentAge of system >> lifetime of dust  Pic Artymowicz 1997 (Also applicable to Fomalhaut) Artymowicz 1997

  8. Introduction: Vega Phenomenon 0.5 m 2.2 m 10-20 m 850 m  Pic Vega Fomalhaut  Eri HR 4796A HD 141569 glow Resolved images of dust structure linked to unseen planets

  9. Structure: Effects of unseen planets Rings & Blobs (Zody & KB) Dermott et al. 1994 resonant trapping by Earth Holes (most common) Roques et al. 1994 resonant trapping and ejection Vertical Warps ( Pic) Mouillet et al. 1997 secular perturbation in beta Pic

  10. Links: Structure eps Eri Vega Disk Holes = Planet Formation?(Ozernoy et al. 2000) Planet+dust Simulation 2 MJ at 50-60 AU low eccentricity 2 MJ 0.2 MJ 850 m Data

  11. FOMALHAUT: IRAS (1984-1990) Extended at 60 microns 36" source diameter, ~30 micron grains, Tmax~75 K Backman & Paresce 1993

  12. FOMALHAUT: JCMT at 800 microns (1993) Zuckerman & Becklin (1993) Extended north-south, PA = 0˚ ± 30˚

  13. FOMALHAUT: Sub-mm (1998) Holland, Greaves, Zuckerman et al. 1998 Discovery of 2 peaks ~10” radius (77 AU) 60 AU radius cavity see also Dent et al. (2000) for modeling and analysis SED Fitting T = 40 K a = 100 mm dominant a = 10 mm < 10% of total Mdust = 1.4 - 1.5 lunar Image Fitting A belt, 100-140 AU radius Sharp outer cutoff tcollision=2x105 yr at 100 AU

  14. FOMALHAUT: Age Barrado y Navascues et al. 1997, 1998 Gliese (1969) suggested that Fomalhaut and Gl 879 (K5Ve) are a physical pair. Castor Moving Group

  15. AU Microscopii - Past Circumstellar Properties Search for debris disks around AU Mic Deltorn & Kalas, unpublished.

  16. FOMALHAUT: Age Age = age of Gl 879 = 200 ± 100 Myr Isochrones at 3, 10, 35, 70 Myr and ZAMS Barrado y Navascues et al. 1997, 1998

  17. FOMALHAUT: Age Between a  Pic and a Kuiper Belt Dust abundance vs. age Adapted from Zuckerman 2001 (ARAA)

  18. FOMALHAUT: Revisited at 450 & 850 microns Holland et al. 2003; also Wyatt & Dent 2002 A non-uniform ring

  19. FOMALHAUT: Inner arc or clump? 3 detection, 100 AU from star, 50 AU in length Model belt: 125-185 AU, peak at 135 AU Flux from arc is 5% of total, ~0.075 lunar mass Offset ring or pericenter glow cannot fit the asymmetry Instead, centered ring, but asymmetric density from 1:1 MMR Holland et al. 2003; also Wyatt & Dent 2002

  20. FOMALHAUT: Spitzer Stapelfeldt et al. 2004 spatially resolved at 24, 70 & 160 m

  21. FOMALHAUT: Spitzer Stapelfeldt et al. 2004 160 24 70 ring eccentricity in model = 0.07 planet orbit: a = 40 AU, e = 0.15

  22. FOMALHAUT: 350 mm + Spitzer Marsh et al. 2005 69 AU resolution at 350 micron Ring with no inner clump T = 42 K Model fit using Spitzer (24, 70, 160m) & 350m 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)

  23. HST/ACS Search for Planets"ACS detection of sub-stellar companions around Vega, Fomalhaut and Beta Pic via parallax & proper motion"Cycle 12 GO Program: Kalas, Graham & Clampin Co-moving companions are detectable within a few months using the ACS/HRC (25 mas/pixel, FWHM = 60 mas). The existence of planets is inferred from disk structure observed in the sub-mm With age ~200 Myr and distance ~7.7 pc, thermal flux from cooling Jupiters and brown dwarfs may be detected in the HRC F814W broadband filter (I-band). F814W = 26 mag for 1 Jupiter mass. F814W = 22 mag for 10 Jupiter mass Fomalhaut Field Source May 17 - Sep. 27, 2004 I = 23.5 mag

  24. Fomalhaut Optical Discovery

  25. HST ACS planet search HST Fomalhaut detection -- consistent with sub-mm maps Hubble Space Telescope JCMT SCUBA 450 micron map (Wyatt & Dent 2002)

  26. HST ACS planet search Fomalhaut • Semi-major axis: a =140.7± 1.8 AU • Semi-minor axis: b = 57.5 ± 0.7 AU • PA major axis: 156.0˚±0.3˚ • Inclination: i = 65.9˚± 0.4˚ • Projected Offset: 13.4 ± 1 AU • PA of offset: 156.0˚ ± 0.3˚ • Deprojected Offsetf = 15.3 AU • Eccentricity: e = f / a = 0.11 Kalas, Graham & Clampin 2005, Nature, Vol. 435, pp. 1067 F814W: 80 min., 17 May, 02 Aug, 27 Oct, 2004 F606W: 45 min., 27 Oct. 2004 25 mas / pix, FWHM = 60 mas = 0.5 AU No inner clumps orbital period at 140 AU = 1200 yr

  27. HST ACS planet search Model Disk Fitting • inner & outer radius • inclination to line of sight • scattering phase function Grain number density function of radius and height

  28. HST ACS planet search Asymmetric Scattering Phase Function |g| = 0.2 Zodiacal Light = +0.2; Forward Scattering Median size ~30 microns (blowout size for Fomalhaut is 7 microns). Model subtraction emphasizes inner dust component. 1-2 mag fainter than Q3. SE is 1.7 times brighter than NW. Inner dust component also detected in thermal infrared by Holland et al. 2003 and Stapelfeldt et al. 2004.

  29. HST ACS planet search Belt width as a function of azimuth caveat the missing information: 1) Fomalhaut's belt is narrowest near apastron 2) No clear evidence for azimuthal structure Circular annulus with inner radius 133 AU, outer annulus 158 AU

  30. HST ACS planet search Evidence for a planetary system:Knife-edge inner boundary Radial cut along 10˚ segment Q2 (apastron), in the illumination corrected image; cut traces the material surface density of the structure rather than its brightness. Cuts were actually made in 2˚ increments such that we show the mean value and the error bars are the standard deviation per measurement. Thus the error bars indicate the degree of azimuthal noise, whereas the overall modulation of points radially indicates the radial noise. Blue line is the model fit: Knife-edge inner edge = 133 AU n(r) = n(ro) r -9 Scale height = 3.5 AU at 133 AU

  31. Evidence for planets: sharp inner edges Kuiper Belt dust models by Moro-Martin & Malhotra 2002 radial cuts planets Dust produced by KBOs a=35-50 AU, i = 0˚-17˚ 1-40 mm, r = 2.7 g cm-3 & 3-120 mm, r=1 g cm-3 7 planet, or no planets Solar gravity, RP, P-R drag, solar wind drag. b = RP / gravity  L* / r s no planets

  32. HST ACS planet search Evidence for a planetary system:Center of symmetry offset Wyatt et al. 1999 G. Schneider, STIS How Observations of circumstellar disk asymmetries can reveal 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 proper (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. 1998). • External eccentric perturber can produce the same center of symmetry offset, but not the sharp inner disk boundary. S = stellar position D = center of particle orbit C = center of precession circle P = pericenter of a particle orbit DP = a, semi-major axis of a particle orbit wf = direction of forced pericenter SD = a eSC = a eforced CD = a eproper Torus inner radius = a (1 - eproper) = 133 AU Torus outer radius = a (1+ eproper)

  33. HST ACS planet search Fomalhaut Simulation Adam Deller & Sarah Maddison (Swinburne University of Technology) Planet Mass = 2 M_jupiter eccentricity = 0.3 semi-major axis = 70 AU

  34. Architectures Planetary System Architectures: Solar System vs. Fomalhaut Kuiper Belt: 30 - 50 AU Sedna: Perihelion = 76 AU, Aphelion = 990 AU

  35. Fomalhaut & the Kuiper Belt: A fairy tale Truncation of disk by OB stellar radiation or dynamical perturbations in early star forming environment (make the outer edge first). Disk heating and mass loss lead to an unstable system. Unstable systems lead to giant planet migration with larger eccentricities than found in dynamically cold (e=0.001) and massive disks. Outward planet migration stops when disk material runs out, but will continue in more massive disks (makes the large inner edge). Larwood & Kalas 2001 Tsiganis et al. 2005

  36. Architectures: Physical extent >>800 AU beta Pic AU Mic 200 AU HD 107146 170 AU Fomalhaut 160 AU HR 4796A 70 AU Sun 50 AU

  37. Introduction: Vega Phenomenon Disks placed at the same distance:

  38. HST ACS planet search Fomalhaut's Belt: Significance to Astronomy Fomalhaut's belt is the closest that has been resolved in scattered light. Inclination 66˚ means that it can be studied around its entire circumference Belt characteristics that are consistent with planet-mass objects orbiting Fomalhaut: 1) The belt center is offset from the stellar center by 15 AU ± 1 AU, demanding apsidal alignment by a planet, 2) Disk edges are sharper on the inner boundary compared to the outer boundary and consistent with our scattered light model that simulates aknife-edge inner boundary and dynamical models of planet-disk interactions. Age200-300 Myr, this is one of the oldest debris disk seen in scattered light. It is probably leaving the clean-up phase and progressing to a configuration similar to that of our solar system. Replace Beta Pictoris as the debris disk Rosetta Stone? Astrophysical Mirror to our Kuiper Belt?

  39. Summary Questions: Outer extent of the disk? Color? Main belt vs. inner dust? Width as a function of azimuth? Azimuthal asymmetries? Plausible companion properties? Planet at large radii? Exterior companion? Co-moving blobs? Contact Info: Kalas (at) astron.berkeley.edu More information: http://www.disksite.com/ Reference: Kalas et al. 2005, Nature, Vol. 435, pp. 1067

  40. HST ACS planet search Future HST/ACS Observations: Multi-color imaging of the entire belt in Cycle 14 (July - August 2006) • Search for azimuthal asymmetries; e.g. Trojans • Measure ring width as a function of azimuth • Search for color gradients azimuthally and radially • Characterize properties of Zodiacal dust analog; dust interior to the belt. • Understand grain properties, source regions More Future Work: • Are there planets? Detect the planet(s) directly. Keck II AO run in July, October. • Are there external perturbers confining the outer belt boundary? Wide field multi-epoch search. • What is the origin of the belt? Planet formation theory; migration; resonance vs. ejection. What are the orbital elements of a planet? • Is Fomalhaut's belt a mirror of our young Kuiper Belt? What accounts for the factor of three difference in semi-major axis scale?

  41. HST ACS planet search Future Work Elliot et al. 1981 Uranus ring occultation

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