DEBRIS DISKS WITH HERSCHEL:

AN OVERVIEW OF THE DUNES MODELING ACTIVITIES

Jean-Charles Augereau, Steve Ertel, Alexander Krivov, Jérémy Lebreton, Torsten Löhne, Sebastian Müller, Philippe Thébault,

Sebastian Wolf

& the DUNES team:

O. Absil, D. Ardila, M. Arévalo, A. Bayo, D. Barrado, C. Beichmann, G. Bryden, W. Danchi,C. del Burgo, C. Eiroa, D. Fedele, M. Fridlund, M. Fukagawa, B.M. González-Garcıa, E. Grün, R. Gutiérrez, A. M. Heras, I. Kamp, R. Launhardt, R. Liseau, R. Lorente, J. Maldonado, J. Marshall, R. Martínez-Arnaíz, G. Meeus, D. Montes, B. Montesinos, A. Mora, A. Morbidelli, H. Mutschke, T. Nakagawa, G. Olofsson, G. L. Pilbratt, I.

Ribas, A. Roberge, J. Rodmann, J. Sanz-Forcada, E. Solano, K. Stapelfeldt, H. Walker, G. J. White

Debris disks

KALAS et al. 2008

Another expression for planetary systems

Towards getting a complete picture of planetary systems

DUNES project

Our own solar system is a debris disk (M. Wyatt’s talk).Kuiper Belt (A. Krivov’s talk)

Low luminosity extra-solar Kuiper Belt remained elusiveto previous space missions (A. Moro-Martin’s talk)

Two Herschel Open Time Key projects : DEBRIS (B. Matthews’s talk) DUNES (C. Eiroa’s talk)

+ GTO programs (B. Vandenbussche’s talk)

This talk : No statistics Imaging capabilities of Herschel and how

it breaks degeneracy between models Overview of the modeling approaches in the DUNES team

The q1 Eri planetary systempre-Herschel understanding

A JUPITER-MASS PLANET

M sin i: 0.93 MJupiter

Semi-major axis: 2.03 AU Eccentricity : 0.1MAYOR et al. 2003, BUTLER et al. 2006

A KUIPER-LIKE BELT

IRAS, ISO and Spitzer: cold dust, with a luminosity a few 100 times that of the Kuiper Belt(Ldisk/Lstar ~4x10-4)

Sub-mm APEX/LABOCA images: disk extent is up to several tens of arcsec (LISEAU et al. 2008)

THE STAR Spectral type: F8 Distance : 17.4 pc Age : ~ 2 Gyr

Pre-Herschel photometryof q1 Eri

Post-Herschel photometryof q1 Eri

SED fitting : known degeneracy between dust properties and disk structure

SED fitting: degeneracy between dust properties and

disk structure

Simplest debris disk model : Ring – like geometry

(Kuiper Belt, Fomalhaut, HR4796, and many others):1 main parameter = the peak density position (rpeak)

Donhanyi grain size distribution :1 main parameter = minimum grain size (smin)

Silicate grains

SED fitting: degeneracy between dust properties and

disk structure

HST images suggest a peak at 83AU (4.8”, STAPELFELDT et al., in prep.)

PACS observations of q1 Eri

Disk spatially resolved at all PACS wavelengths Disk marginally resolved along the minor axis: inclination > 55 deg

See A&A Letter by LISEAU et al. 2010

PACS image fitting

Breaking the degeneracy

Detailed simultaneous modeling of the SED and PACS images required to unveil the disk structure, dust properties and dynamical history

The basic DUNES modeling suite

Classical: Radiative transfer, assuming analytic functions for the

surface density and size distribution Two radiative transfer codes, with different fitting

strategies: GRATER (GRENOBLE) : bayesian statistical analysis SAND (KIEL) : simulated annealing minimization scheme

Collisional: Radiative transfer, fed by results from collisional code

ACE that generates and evolves the disk “from the sources”

ACE, SEDUCE and SUBITO codes (JENA)

Two modeling approaches, Three fitting strategies, Five codes

Advantages & limitations of the codes GRATER [Grenoble, J.-C. AUGEREAU & J. LEBRETON]

Fast exploration of large parameter spaces Stored grid for subsequent statistical analysis (24 million models for q1 Eri) Post-processing easy (e.g. re-computation of c2 with different weights) Simplistic description of the disk properties & no direct link to parent bodies

SAND [Kiel, S. ERTEL & S. WOLF] Fast: finds fit among ~1011 models in ~70 hours Large number of free parameters possible Limited initial constraints on disk physics Simplistic description of the disk properties & no direct link to parent bodies

ACE + SEDUCE + SUBITO [Jena, A. KRIVOV, T. LÖHNE, S. MÜLLER] Deep physical modeling of the disk from the sources Realistic description of disk properties Mass and dynamical excitation of unseen parent bodies CPU-demanding : 20 models in 3 months

Classical approach: statistical (bayesian) analysis

40-50% of ice

Surface density goes

as r-2

Size distribution: -

3.5 power index

Minimum grain size: ~ 1 to 2

µm

Belt position~ 75 AU

Inclination ~ 71o

Classical Approach (GRaTer & SAnD

codes)

Best fit (cr2 = 1.5, dof=100):

DUST DISK : Mass : 0.04 MEarth

Surface density: r -2

Belt peak position: 75-80AU

Fit to the SED

Fit to the PACS Radial Profiles

GRAIN PROPERTIES: Close to 50-50 silicate-ice mixture Minimum grain size ~ 1.5 mm Size distribution: -3.5 power law

index

Best fit:

DUST DISK & GRAIN PROPERTIES: Mass : 0.02 Mearth

50-50 silicate-ice mixture

Coupled radial-size distribution

Collisional Approach (ACE+SUBITO+SEDUCE codes)

PARENT BELT: Location: 75-125 AU Eccentricities: 0.0…0.1 Mass : ~1000 Mearth (if 2 Gyr),

but ~ 100 Mearth (if 0.5Gyr)

Delayed stirring ?

See poster by S. Müller

Summary of model results

Consistent results between the three codes: Dust mass Grain size distribution Dust composition (ice likely) Parent belt position at ~ 75AU Dust surface density consistent

with a collisionally active debris disk

Open questions: Lacking inner (<5”) 70mm emission

Our unconvolved view of

the q1 Eri Kuiper Beltat PACS wavelengths

Deconvolved images

• Deconvolution with the MCS algorithm (Magain, Courbin & Sohy 1998, ApJ 494, 472)• Two blobs, suggestive of an inclined ring• Possible asymmetry between the two sides

70 µm

100 µm

The HD 207129 planetary system

pre-Herschel understandingA KUIPER-LIKE BELT

IRAS, ISO, Spitzer APEX/LABOCA: cold dust, with a fractional IR luminosity Ldisk/Lstar of ~1.4x10-4 (JOURDAIN ET AL. 1999, NILSSON ET AL. 2010, KRIST ET AL. 2010)

THE STAR Spectral type: G2 Distance : 15.6 pc Age : ~ 5 Gyr

PACS images

Disk resolved at all PACS wavelengths

Inclined, ring-like disk

Poster by LÖHNE ET AL.

Deconvolved PACS images

Brightness peak at around 130-140 AU

One of the most extended debris ring

Faint brightness asymmetry between the two ansae

Collisional Approach:

preliminary results Steady-state dust

production from a 85 Mearth

planetesimal belt at 120 – 160 AU, and dust massof 6 x 10-3 Mearth

Lack of emission in the inner regions

Conclusions OBSERVATIONS

Images of extra-solar Kuiper belts with unprecedented resolutionand sensitivity

Inner gaps seen in thermal emission at <100mm for the first time

The belts show some degree of asymmetry

MODELS: Degeneracy between dust properties and disk structure

broken thanks to the PACS images Probing dust composition Probing collisional history: support to delayed stirring in the

case of q1 Eri (self-stirring by Plutos, or stirring by q1Eri c, or even by q1Eri b)

DUNES modeling “toolbox” works fine, we are ready for more data

More about q1 Eri: poster by MÜLLER More about HD 207129 : poster by

LÖHNE More about OTKP DUNES: talk by

EIROA More about Cold Debris Disks : talk by

A. KRIVOV

Additional slides

Coll approach: dust distributions