DETAILED MODEL OF THE EXOZODIACAL DISK OF FOMALHAUT AND ITS ORIGIN

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EXOZODI project http://ipag.osug.fr/~augereau/site/ ANR_EXOZODI.

THE EXOZODIACAL DISK OF FOMALHAUT AND ITS ORIGIN J.-C. Augereau IPAG, Grenoble Based on a study by J. Lebreton, R. van Lieshout, J.

1 EXOZODI project ANR_EXOZODI.html IAU Symposium 299 EXPLORING THE FORMATION AND EVOLUTION OF PLANETARY SYSTEMS Victoria, Canada 2013, June 6 DETAILED MODEL OF THE EXOZODIACAL DISK OF FOMALHAUT AND ITS ORIGIN J.-C. Augereau IPAG, Grenoble Based on a study by J. Lebreton, R. van Lieshout, J.-C. Augereau, O. Absil, B. Menesson, M. Kama, C. Dominik, A. Bonsor, J. Vandeportal, H. Beust, D. Defrère, S. Ertel, V. Faramaz, P. Hinz, Q. Kral, A.-M. Lagrange, W. Liu, P. Thébault arxiv :

2 DUST IN THE FOMALHAUT PLANETARY SYSTEM Cold debris disk at 140 AU HST and ALMA (montage) Kalas et al. 2005, Boley et al Planet( it s real ) Talk by P. Kalas

3 DUST IN THE FOMALHAUT PLANETARY SYSTEM Cold debris disk at 140 AU HST and ALMA (montage) Kalas et al. 2005, Boley et al Exozodiacal disk Planet( it s real ) Talk by P. Kalas

4 THE UNRESOLVED INNER DEBRIS DISK OF FOMALHAUT! hot/warm)excess!seen!with!spitzer,)herschel,)and)possibly)alma! Unresolved,)r)<)20)AU Combined microns Spitzer/MIPS images Stapeldfeldt et al Herschel/PACS, Acke et al HST and ALMA (montage) Kalas et al. 2005, Boley et al. 2012

T dust )=)170K 10 3 flux contaminated from the cold ring Talk by K.

5 THE UNRESOLVED INNER DEBRIS DISK OF FOMALHAUT! hot/warm)excess!seen!with!spitzer,)herschel,)and)possibly)alma! Unresolved,)r)<)20)AU SED of the Fomalhaut Asteroid Belt! T dust )=)170K 10 3 flux contaminated from the cold ring Talk by K. Su flux density (mjy) blackbody of 170 K modified blackbody of 170 K Spizter/IRS and MIPS Su et al wavelength (µm)

6 THE INNER DEBRIS OF FOMALHAUT RESOLVED VINCI at VLTI K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12%

7 THE INNER DEBRIS OF FOMALHAUT RESOLVED VINCI at VLTI K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12% Keck Interferomer Nuller

8 THE INNER DEBRIS OF FOMALHAUT RESOLVED VINCI at VLTI K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12% Keck Interferomer Nuller See posters by S. Ertel (6.15) and D. Defrère (6.13) for details about interferometric data

9 THE INNER DEBRIS OF FOMALHAUT RESOLVED VINCI at VLTI K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12% Keck Interferomer Nuller K-band (2.18 um), FOV: 6 AU N-band (8 to 13 um), FOV: 4 AU Circumstellar excess: 0.88±0.12% Circumstellar null excess: 0.35±0.10% Absil et al Mennesson et al. 2013

10 THE INNER DEBRIS OF FOMALHAUT RESOLVED VINCI at VLTI K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12% Keck Interferomer Nuller K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12% Scaled model of the Solar System zodiacal disk (1 zodi) N-band (8 to 13 um), FOV: 4 AU Circumstellar null excess: 0.35±0.10% Absil et al Mennesson et al. 2013

11 THE INNER DEBRIS OF FOMALHAUT RESOLVED VINCI at VLTI K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12% Keck Interferomer Nuller K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12% 5000 zodis Scaled model of the Solar System zodiacal disk (1 zodi) N-band (8 to 13 um), FOV: 4 AU Circumstellar null excess: 0.35±0.10% Absil et al Mennesson et al. 2013

12 THE INNER DEBRIS OF FOMALHAUT RESOLVED VINCI at VLTI K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12% Keck Interferomer Nuller K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12% 5000 zodis Scaled model of the Solar System zodiacal disk (1 zodi) N-band (8 to 13 um), FOV: 4 AU Circumstellar null excess: 0.35±0.10% Absil et al Mennesson et al zodis

13 THE INNER DEBRIS OF FOMALHAUT RESOLVED VINCI at VLTI K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12% Keck Interferomer Nuller K-band (2.18 um), FOV: 6 AU Circumstellar excess: 0.88±0.12% 5000 zodis N-band (8 to 13 um), FOV: 4 AU Circumstellar null excess: 0.35±0.10% Absil et al Mennesson et al Scaled model of the Solar System zodiacal disk (1 zodi) The standard zodiacal disk model fails to explain the observations simultaneously 250 zodis

14 SINGLE DUST POPULATION Menesson et al. 2013

15 SINGLE DUST POPULATION Menesson et al Similar modeling approach as for our previous detections of exozodiacal disks, e.g. Vega (Absil et al. 2006, Defrère et al 2011), Tau Ceti (Di Folco et al. 2007)

16 SINGLE DUST POPULATION Menesson et al Similar modeling approach as for our previous detections of exozodiacal disks, e.g. Vega (Absil et al. 2006, Defrère et al 2011), Tau Ceti (Di Folco et al. 2007) Radiative transfer model for debris disks (GRaTeR) parametric model useful features : mixtures of silicates and carbonaceous material size-dependent sublimation distance statistical (bayesian) analysis

17 SINGLE DUST POPULATION Menesson et al Similar modeling approach as for our previous detections of exozodiacal disks, e.g. Vega (Absil et al. 2006, Defrère et al 2011), Tau Ceti (Di Folco et al. 2007) Flux [Jy] VLTI/VINCI ALL SHORT LONG Radiative transfer model for debris disks (GRaTeR) parametric model useful features : mixtures of silicates and carbonaceous material size-dependent sublimation distance statistical (bayesian) analysis KIN Nulls angle = o azimuth = o b proj = m 1 10 λ [µm] Keck Nuller λ [µm]

18 SINGLE DUST POPULATION Menesson et al Similar modeling approach as for our previous detections of exozodiacal disks, e.g. Vega (Absil et al. 2006, Defrère et al 2011), Tau Ceti (Di Folco et al. 2007) Flux [Jy] VLTI/VINCI ALL SHORT LONG Radiative transfer model for debris disks (GRaTeR) parametric model useful features : mixtures of silicates and carbonaceous material size-dependent sublimation distance statistical (bayesian) analysis A single dust population model fails to explain the observations simultaneously KIN Nulls angle = o azimuth = o b proj = m 1 10 λ [µm] Keck Nuller λ [µm]

19 SINGLE DUST POPULATION Menesson et al Similar modeling approach as for our previous detections of exozodiacal disks, e.g. Vega (Absil et al. 2006, Defrère et al 2011), Tau Ceti (Di Folco et al. 2007) Flux [Jy] VLTI/VINCI ALL SHORT LONG Radiative transfer model for debris disks (GRaTeR) parametric model useful features : mixtures of silicates and carbonaceous material size-dependent sublimation distance statistical (bayesian) analysis A single dust population model fails to explain the observations simultaneously KIN Nulls angle = o azimuth = o b proj = m 1 10 λ [µm] Keck Nuller There exists a population of hot grains that accumulates next to the sublimation radius λ [µm]

20 IMPROVED DUST SUBLIMATION MODEL The time for a grain to sublimate, tsub, depends on its size, a, and on the sublimation temperature Tsub (and on thermodynamical quantities, see Kama et al. 2009)

21 IMPROVED DUST SUBLIMATION MODEL The time for a grain to sublimate, tsub, depends on its size, a, and on the sublimation temperature Tsub (and on thermodynamical quantities, see Kama et al. 2009) SUBLIMATION TEMPERATURES 2500 Astrosilicates Carbonaceous material 0.01 yr 1.00 yr 100. yr 2000 T sub [K] Grain size [μm]

22 IMPROVED DUST SUBLIMATION MODEL The time for a grain to sublimate, tsub, depends on its size, a, and on the sublimation temperature Tsub (and on thermodynamical quantities, see Kama et al. 2009) Competing processes affect the grains: collisions, PR drag, radiation pressure. These have their own timescales SUBLIMATION TEMPERATURES 2500 Astrosilicates Carbonaceous material 0.01 yr 1.00 yr 100. yr 2000 T sub [K] Grain size [μm]

23 IMPROVED DUST SUBLIMATION MODEL The time for a grain to sublimate, tsub, depends on its size, a, and on the sublimation temperature Tsub (and on thermodynamical quantities, see Kama et al. 2009) Competing processes affect the grains: collisions, PR drag, radiation pressure. These have their own timescales SUBLIMATION TEMPERATURES GRAIN REMOVAL TIMESCALES T sub [K] Astrosilicates Carbonaceous material 0.01 yr 1.00 yr 100. yr Timescales [years] t blow t col t PR t survival Astrosilicates Carbonaceous material Grain size [μm] Grain size [μm]

24 DUST SUBLIMATION MODEL Where can a grain survive knowing its size? Net result: the sublimation temperature depends on the grain size The size-dependent sublimation distance is affected Dashed line: constant T sub ; Solid line: size-dependent T sub SUBLIMATION DISTANCES OF CARBONACEOUS MATERIAL d sub [AU] Porous carbon leftovers P = 0.00 P = 0.75 P = Grain size [um]

25 2-COMPONENT DISK MODELS OF FOMALHAUT METHODOLOGY: Bayesian analysis 1.2 million models BEST FIT TO THE DATA KIN excess null depths Flux [Jy] Spectral Energy Distribution VLTI/VINCI, MIPS 24, Herschel 70 μm, (ALMA 870 μm) Excess+star r hot = 0.09 AU r warm = 1.59 AU; (r 1.0 ) KIN Nulls angle = 71.2 azimuth = 47.6 b proj = 75.8 m r hot = 0.09 AU r warm = 1.59 AU; (r 1.0 ) λ [μm] Flux [Jy] Excess λ [μm] Green: hot ring - red: warm belt - Blue: total

26 2-COMPONENT DISK MODELS OF FOMALHAUT METHODOLOGY: Bayesian analysis 1.2 million models BEST FIT TO THE DATA KIN excess null depths Flux [Jy] Flux [Jy] Spectral Energy Distribution VLTI/VINCI, MIPS 24, Herschel 70 μm, (ALMA 870 μm) Excess+star r hot = 0.09 AU r warm = 1.59 AU; (r 1.0 ) KIN Nulls angle = 71.2 azimuth = 47.6 b proj = 75.8 m HOT RING WARM BELT Material C C+Si Size (μm) >)0.02 > 3 Distance (AU) r hot = 0.09 AU r warm = 1.59 AU; (r 1.0 ) λ [μm] [1.5, 2.5] Excess λ [μm] Green: hot ring - red: warm belt - Blue: total Mass (MEarth) 2.5x10 A10 2x10 A6 χ 2 r = 1.6 (dof=30)

27 GRAIN SIZES AND LOCATION MAP OF THE FLUX AS A FUNCTION OF DISTANCE AND Warm bound dust grains at ~ 2 AU GRAIN SIZE AROUND FOMALHAUT (HERE AT 12 MICRONS) grain size [µm] λ=12 μm log(flux) [Jy] distance [AU] The warm component is consistent with an asteroid belt inward of the ice line 10.0

28 GRAIN SIZES AND LOCATION Warm bound dust grains at ~ 2 AU Hot unbound carbon grains at ~ AU MAP OF THE FLUX AS A FUNCTION OF DISTANCE AND GRAIN SIZE AROUND FOMALHAUT (HERE AT 12 MICRONS) grain size [µm] λ=12 μm distance [AU] The warm component is consistent with an asteroid belt inward of the ice line 10.0 The hot exozodi is composed of < 1 μm at the carbon sublimation distance log(flux) [Jy]

29 ORIGIN OF THE EXOZODIACAL DUST? Steady collisional evolution of a local planetesimal belt : excluded. Predicted Ldust/Lstar following Wyatt (2007a): 4 to 6 orders of magnitude too low Replenishment of the warm belt in barely bound grains at ~2AU? dm/dt [Mearth/yr] Model ~10-9? 140 AU Source: Cold belt at 140AU Mechanism: PR drag Source: Cold belt at 140AU Mechanism: planetesimal scattering by a chain of planets (comets) < van Lieshout et al., in prep < Bonsor, Augereau & Thébault, 2012

30 ORIGIN OF THE EXOZODIACAL DUST? Replenishment of the hot, carbon-rich belt in unbound grains at < 0.2AU? dm/dt [Mearth/yr] 140 AU 2 AU Source: Warm belt at 2AU Mechanism: PR drag Model ~10-7 < van Lieshout et al., in prep 0.2 AU Source: rocky planet (KIC b) Mechanism: evaporation ~10-9 Rappaport et al. 2012?

31 ORIGIN OF THE EXOZODIACAL DUST? Replenishment of the hot, carbon-rich belt in unbound grains at < 0.2AU? dm/dt [Mearth/yr] 140 AU 2 AU Source: Warm belt at 2AU Mechanism: PR drag Model ~10-7 < van Lieshout et al., in prep 0.2 AU Source: rocky planet (KIC b) Mechanism: evaporation ~10-9 Rappaport et al. 2012? Gas is expected (dust sublimation). This may slow down unbound particles on their way out. Replenishment timescale = removal timescale for a gas mass of ~5x10-3 Mearth Assuming dm/dt ~ Mearth/yr (PR drag from 2AU) => t ~ 400Myr ~ age of Fomalhaut

32 ORIGIN OF THE EXOZODIACAL DUST? Other mechanisms possibly at play in the sublimation zone: Lorentz force non thermal emission (PAHs) 140 AU 0.2 AU 2 AU?

emission (PAHs) Non steady-state scenarios: LHB-like events are unlikely (Bonsor, Raymond &

33 ORIGIN OF THE EXOZODIACAL DUST? Other mechanisms possibly at play in the sublimation zone: Lorentz force non thermal emission (PAHs) Non steady-state scenarios: LHB-like events are unlikely (Bonsor, Raymond & Augereau 2013) But : planet Fomalhaut b has e=0.8, or even higher, with a possible pericenter distance in between 7 and 10AU credits: H. Beust 140 AU? 0.2 AU 2 AU

34 DO OTHER STARS HAVE EXOZODIACAL DUST? Absil et al., 2013,in press FLUOR at CHARA Sample of 42 stars 29% of nearby stars have K-band excess (CHARA/FLUOR, Absil et al. 2013) 4-13% of stars with N-band excess emission (KIN, Millan-Gabet et al. 2011)

DO OTHER STARS HAVE EXOZODIACAL DUST? Absil et al., 2013, in press Stars with outer dust reservoirs have similar exozodiacal dust occurrence rates, independent of their spectral type.

35 DO OTHER STARS HAVE EXOZODIACAL DUST? Absil et al., 2013, in press Stars with outer dust reservoirs have similar exozodiacal dust occurrence rates, independent of their spectral type. Stars w/o outer dust reservoir have very different behavior depending on their spectral type. Warning: only 5 A-type stars in this subsample. K-band excess frequency 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% A stars F stars GK stars 29% 43% 25% 80% 0% 10% Outer reservoir No outer reservoir See poster by Ertel for VLTI/PIONIER results

36 DO OTHER STARS HAVE EXOZODIACAL DUST? Absil et al., 2013, in press Absence of time dependence (Absil et al. 2013).

2 AU 2 AU Hot dust: may originate from the warm belt provided there is sufficient gas Warm dust: steady-state collisional evolution is

37 CONCLUSIONS We resolve the exozodiacal disk of Fomalhaut using near- and mid-ir interferometry Two distinct populations hot dust: carbonaceous, unbound grains in the sublimation zone (<0.2AU) warm dust: bound grains at ~ 2AU 140 AU 0.2 AU 2 AU Hot dust: may originate from the warm belt provided there is sufficient gas Warm dust: steady-state collisional evolution is excluded. Replenishment from the belt at 140 AU is not sufficient We speculate on a possible connexion with planet Fomalhaut b? Absil et al Mennesson et al Lebreton et al. 2013, in astro-ph

Observations of exozodiacal disks. Jean-Charles Augereau LAOG, Grenoble, France. ISSI team: Exozodiacal dust diks and Darwin. Cambridge, August 2009

Observations of exozodiacal disks. Jean-Charles Augereau LAOG, Grenoble, France. ISSI team: Exozodiacal dust diks and Darwin. Cambridge, August 2009 + Olivier Absil Emmanuel Di Folco Hervé Beust Rémy Reche Alexander Krivov Philippe Thébault Torsten Loehne Vincent Coudé du Foresto Bertrand Menesson Pierre Kervella ISSI team: Exozodiacal dust diks and