SEBASTIAN MÜLLERCollaborators

ALEXANDER V. KRIVOV, THORSTEN LÖHNE, HARALD
MUTSCHKE & MARTIN REIDEMEISTER
Astrophysical Institute and University Observatory
Friedrich Schiller University Jena
Germany

Kobe, September 10, 20091

… let me introduce myself.

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Jena
 First mentionedin 1236
 ≈ 100 000 citizens(≈ 25 000 students)
 Wine cultivation
 University foundedin 1558
 Center for philosophy and literature in Germany /Europe in 19th century (Goethe, Schiller, …)
 Center for optics from mid of 19th century until today(Ernst Abbe, Carl Zeiss, Otto Schott) “Science City” 2008
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The Astrophysical InstituteKobe, September 10, 20094

The Astrophysical Institute
The observer group: Search forexoplantes
 Neutron stars

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Prof. R. Neuhäuser

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The Astrophysical InstituteThe laboratory group: Spectroscopy on
dust from UV tomid-IR

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Dr. H Mutschke

6The Astrophysical Institute
The theory group: Prof. A. V. Krivov
 Protoplanetary
disk modeling Giant planet
formation
 Debris disk
modeling

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Outline
Definition of debris disksModeling of debris disks− Classical Approach− New Approach

OutlookSummary
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An introduction

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Definition

Asteroid belt

Edgeworth Kuiper belt

Hillenbrandt et al., 2008

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Information Sources
 Scattered stellar light:

visual to near-IRFindings:→ Photometry• ~ 15 % of MS stars host debris disks→ Imaging→ Similar frequencies for AFGK stars(earlier types my be slightly favored) Thermalemissionof2007,dust:
mid-IRettoal.,radio(e.g.
Trilling et al.,2008; Hillenbrand2008)→
Photometry of excess decreases with age• Strength(Zuckerman & Song, 2004; Moór et al., 2006)→ Spectroscopy• No
correlation with metalicity→Imaging(Greaves et al. ,2006; Beichman et al., 2006)

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It‘s all about dust!

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Classical Approach
Advantage:
Hillenbrand et•al.,
2008
Quickand easy to use
Disadvantage:• Assumed dust distribution not necessarily
justified• Only dust portion is modeled
N ~ r-ξ s-η

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Classical Approach - Application
Investigation of thesystem HR 8799
 A5 V star at 40 pc
 IR-excess long known Special:
3 planets discovered!

Marois et al., 2008
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Reidemeister, Krivov, Schmidt, Fiedler, Müller, Löhne, Neuhäuser, A&A, 2009

Results:• Favor a rather younger age ( ≤ 50Myr)• Nearly pole-on (20 – 30°)
• Evolutionary models suggest masses ≤ 7 - 10 MJup
• Planets stable for 5 - 13 MJup depending on systems
orientation
Coherent
analysis:→ higher masses require 2 : 1 resonance Central star
• Planetesimal belts stable− Age• SED
consistent with modeled planetesimal location− Inclination→
dust masses of 1·10-5 and 4·10-2 MEarth Dust location

Classical Approach - Application

 Planets− Masses− Stability
 Stability of Planetesimals
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Krivov et al. 2006

New Approach
Collisionalmodel:
Typical ACE
result: ACE (Analysis of Collisional Evolution)
 Solving Boltzmann-Smoluchowski equation
 Assumptions:- steady-state evolution- azimuthal symmetry
 Acting mechanisms:- gravity
Arakawa et al. ???)

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- collisions* fragmentation (e.g. Takagi et al. 1983,* cratering (e.g. )- direct radiation forces- Poynting-Robertson drag- wind dragKrivov et al., 200616

New Approach
Fitting
Thermal Emission Model

Modeled debris disk

Collisional Model

Choose initialplanetesimal belt

Information

Compare toobservational data

Attention:
Fitting only possible if notransport mechansism areincluded!
(Löhne, Krivov & Rodmann, A&A, 2008;
Krivov, Müller, Löhne &, Mutschke, ApJ, 2008)

Scaling

Analysis of Collisional Evolution
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SED Utility for Circumstellar Evolution
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10EKBDst@New Approach – 1 Application
200AU

10EKBD@
100AU

Grid of reference disks for Sun-like stars
10EKBD@
30AU
10EKBD@
10AU

G2V

10EKBD@
3AU

Kobe, September 10, 2009

Krivov, Müller, Löhne & Mutschke, ApJ, 200818

stNew Approach – 1 Approach
5 well observed disk
systems around G2 Vstars:

Results:
Cold dust / outer components for all systems→ large (100-200 AU) and massive (0.2-50 MEarth) Kuiper belt
analogs

Warm dust / inner components→ asteroid belt analogs?

Kobe, September Krivov
10, 2009, Müller, Löhne & Mutschke, ApJ, 200819

stNew Approach – 1 Approach
Ardila et al., 2005
Crosschecking the results:

This approach is capable of easily
constraining both dust and planetesimal
properties!
~ 130 AU

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New Approach – 2nd Application
Auman et al., 1984

Modeling of the Vega debris disk
 A0 V star at 7.76 pc
Is the Vega debris disk in Age of ~ 350 Myr
steady-state evolution?
 Archetypalasystem
 Many curiosities:

Su et al., 2005

 Fast rotator
 Very massive dust disk
 Disk structure in longer

wavelengths’ images First discovered ‘exozodi’Kobe, September 10, 2009

Aufdenberg et al., 2006; Peterson et al., 2006

350 µmMarsh et al., 2006

Absil et al., 2006
Wilner et al., 2002
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New Approach – 2nd Application
 Re-reduced Spitzer data Result: General
Assuming a Agreement“first-guess” modelwith observations
 Vary model parameters:→
Vegaagedisk observations not− System− Disk
location /contradictious
to steady-state
extension
dust
production− Diskexcitation− Stellar
luminosity→
modelconstraints:− Chemical− disk older than several 10 Myr
composition− Intermediate luminosity required− Collisional− cratering collisions essentialdescription
 Combine to best fit
Müller,Löhne
Krivov, ApJ, subm.
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September
10, &200922

If you want to make God laugh, tell him your future plans.
(Woody Allen)

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Waiting for Herschel Largest IR telescope to dateApply
newmodelingapproach: Launched on May 14• Covers interesting wavelength region
 3 year mission in Lagrange point L2• Several systems expected to be resolved
 First tests successful

 Open Time Key Project DUNES

Improve new modeling approach:→use
PACSandSPIRE• Unknown sensitivity→informationneedin far-IRandsub-mm→ valuable
other mechanisms
to beincluded

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Coming to disk chemistry High resolution spectra in mid-IR provide insight incomposition of disks (e.g. silicate features)
 Combine different expertise to develop a new analysis
approach:− Mineralogy:
Jena (laboratory)− Observations: LAOG, France− Dynamics:
Jena (theory)

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Lisse et al.,252007

Summary Debris disks comprise dust and planetesimals but are
observable only by the dust’s (thermal) emission
 The classical way of modeling debris disks assumes
simple analytical expressions for the dust distribution− Applied to the planetary system HR 8799 we could showthat the SED supports our results from dynamical
investigations
 We proposed a new way of modeling based on ourcollisional code ACE− A grid of thus modeled reference disks can be used toconstrain both dust and planetesimal properties by“fitting” observed SEDs
− Applied to the Vega system we could show that a steadystate collisional dust production is in agreement withthe observations

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ご清聴ありがとうございました。

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Formation

Figures from : S. Wolf, Protoplanetary Disks, Wilhelm und Else Heraeus – Physics Schlool,
Bad Honnef, Germany, 2005
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