MORPHOLOGICAL EFFECTS OF DUSTGRAINS ON MID-IR EXTINCTION
SPECTRA
October 15, 2009
CPS seminar
Akemi Tamanai (AIU Jena & TU Braunschweig)
Harald Mutschke (AIU Jena)
Jürgen Blum (TU Braunschweig)
Alexander Krivov (AIU Jena)
Chiyoe Koike (Osaka University)

Outline Dust grains
 Experiment Results Astronomical application
 Database SummaryPresence of dust grains appear especially in N and Q
bands via spectroscopy.
Normalized Flux [Jy]1.2g-Her

10.8
0.6
0.4
0.2089 10203040

Wavelength [µm]Vega-type star: HD69830
Herbig Ae/Be star:At
whatcondition
does
theAGB star: g-Her
Comet: Hale-BoppHD100546(Lisse et al. 2007)start actively?
(Posch etplanetal. 1999 & 2002)
formation(Malfait et al. 1998)(Crovisier et al. 1996)

What kinds of dust grains in these observed spectra?
The chemical path way of dust grains↓

Which substance will be the first condensed species out of the gas phase?
At which temperature?
At which abundance it occurs?

Sorts of Dust Grains Fe-rich olivine
Mg-rich olivine

Enstatite(MgSiO3)

Corundum(Ruby: Al2O3)

Decisive role for planet formation,
esp. Terrestrial planets

Corundum(Sapphire: Al2O3)

Amo-MgSiO3
Fayalite(Fe2SiO4)

Quartz(SiO2)

The rocky planets form in high metallicity environments,
where the dust grains are dominant (e.g. Shen et al. 2005)

Meteorite
Meteorites hold a key to understanda formation of dust grains.
 CAIs (calcium-aluminum inclusions)consist minerals which are predicted
via a condensation model.
 Minerals in CAIs are condensed fromprotoplanetary nebula.
 Minerals in CAIs are• Spinel (MgAl2O4)• Corundum (Al2O3)• Rutile (TiO2)• Hibonite (CaAl12O19)• Olivine• Pyroxene
more….

Carbonaceous chondrite
Allende (CV3.2)

NWA869 L4-6
Chondrite

Factors to influence on MIR band profiles
Crystallinity
Polymorph （多形）同一物質が複数の異なった結晶構造を取る
e.g. SiO2
α-quartz(trigonal: 三方晶系)
α-tridymite(orthorhombic:斜方晶系)

α-cristobalite(tetragonal: 正方晶系)

Chemicalcompositon

Morphology
 SizeMg, Fe, Al, Si, Ti,Ca, S, …
e.g. Olivine
San CarlosMg1.9Fe0.1SiO4

 Shape

Sri LanakaMg1.6Fe0.4SiO4

 Agglomeration(Koike et al. 2003)

ExperimentSamples
Al2O3

Silicate
 Forsterite (Mg2SiO4)
 Fayalite (Fe2SiO4)
 Olivine (e.g. Mg1.9Fe0.1SiO4)
 Enstatite (MgSiO3)
 Diopside (CaMgSi2O6)
 Hypersthene ((Mg,Fe)SiO3)
 Wollastonite (CaSiO3)
 Kaolinite (Al2Si2O7▪2H2O)
 Talc (Mg3.33Fe0.1Si4O10 (OH)2)

 Corundum (α-Al2O3)
 γ-Al2O3
 χ−δ−κ-Al2O3

MgAl2O4 (Spinel)
TiO2 (Rutile & Anatase)
CaTiO3 (Pervoskite)
Al2TiO5 (Tialite)
SiO2

www.elbe.astro.uni-jena.de<Medium effect>

εmN2  1.0
KBr  2.3
CsI  3.0
The influence of its
electromagnetic polarization.
Tamanai et al. 2009

KBr :(Potassium Bromide)
Mixing ratio 1:500(sample:KBr)
d=13mm ; mass=0.2g

CsI :(Cesium Iodine)
Mixing ratio 1:500(sample:CsI)
d=13mm ; mass=0.22g

<Morphological effects>
Irregular shapew/ roundishedges

Irregular shapewith notroundish edges

Long and thin

TiO2 (Rutile)
Roundish(TEM & SEM images: at Pathology w/ Dr. Nietzsche)1TiO2 (Rutile)

AldrichAJ

0.8

Normalized
Q ext
Normalized
Extinction

Tayca 150W
Chitan No.101
0.6

0.4

0.2010152025

30354045

Wavelength [µm]Peaks (microns)
Aldrich 13.53
19.56
AJ
15.33
Tayca150 16.47 19.25
CI101
13.85 19.27

24.70
23.51
23.39
25.15

30.30
27.95
28.27
35.87

35.80

50

<Aerosol vs. Pellet Measurements>
Caused by:

1.2(a) TiO2 (anatase)

Aerosol
CsI

1

 Using different
dispersion methods.

Normalized Extinction

0.8
0.6
0.4
0.20101520253035404550

 Particles may
transform during thegrinding procedure.

1.2(b) TiO2 (anatase)

Aerosol
CsI

10.8
0.6
0.4
0.2
0101520253035404550

 Powdered sample
structure deformation
caused by the highpressurization
required for the CsI
pellet technique.

Wavelength [µm]

 Particle orientation

Dust Grains in Debris Disks
Dust sources  Replenished by larger objects (Weissman 1984)
 Comets strew over
 Planetesimals collide with each other
Vega-type stars are surrounded by circumstellar debris disks.
Discoveries:
 Some planets Planetary companions
 Planet candidates(e.g. Mayor et al. 1995, Marcy & Butler 1998, Kürster et al. 2000, Lagrange et al. 2008)

Dust in Debris Disks
Large-sized dust grains  0.1 – 10 μm (Krivov et al. 2000)
Question?
As the grain size increases above 1μm, the spectral features ofRadiation pressure takes smaller
the infrared dust emission are broadened, and grow fainter.
grains away in gas-poor conditions
The Vega-type stars have shown strong emission features ine.g. The disk surface area of β-Pic
the mid-IR range.
Size  1 to 20 µm
Dominant grain size  4 µm

Why?

(Artymowicz 1996)

Objective
 Extinction measurements of large-sized particles(2 – 50 μm)
 Mixture measurements --- How small-sized particles
exert an influence on the extinction spectra when
they are present in a same environment with larger
ones (0.5 µm & 5 µm particles) Fe-rich olivine measurements

Cry-Mg2SiO4 (< 1µm)

Cry-Mg2SiO4 (~ 16 µm)

Amorphous SiO2 (d=0.5 & ~5 µm)

Sample & Setup
Exp. 1 Large-sized particles
 Amorphous SiO2 (monosphere) Crystalline Mg2SiO4

Exp. 2Mixture d=0.5 & d~5 µm amo-SiO2 (complete monosphere shape) d=0.5 & d~5 µm amo-SiO2 (5 µm particle are destroyed)

Exp. 3 Fe-rich Olivine
 Mg1.6Fe0.4SiO4 (Sri Lanka) vs. Mg1.9Fe0.1SiO4 (Peridot)

Aerosol generator
FTIR Spectrometer

Exp. 1 Large Particles (SiO2 monosphere)
1.2
Amo-SiO2 (Aerosol)

Normalized Extinction

19.49 µm

8.93 µmd~5.0 µmd=0.5 µm

0.80.60.4
0.207Peaks8910Log Wavelength [µm]208.93 µm 9.49 µm ∆λ=0.56 µm
20.82 µm 21.21 µm ∆λ=0.39 µm

Crystalline forsterite (Mg2SiO4)
1.2

3500

CsI 1:500
19.24
19.03

0.8 2500
10.15
9.87

κ (cm /g)

Normalized Extinction
2

1 3000

0.6

0.4

27.24
27.27

16.30
16.15

2000

Small particles
Large particles
Small particles
Large particles

23.22
23.25

11.15
11.08

33.65
33.19

1500

0.2

1000
08500910203040Log wavelength [µm]010203040• Size89Larger
 Longer wavelength
Log ofwavelength• The extinction strength
the 23 [µm]µm peak is enhanced.

Exp. 2 Mixture(monosphere vs. monosphere)

1Peaks (d=0.5µm (8.93µm) & d=5.0µm (9.49µm))
1:30 8.94µm 9.47µm
1:50 8.95µm 9.45µm
1:80 8.96µm 9.42µm
1:120 8.97µm 9.47µm

Qext(λ) / Qext(Peak)
Normalized
Extinction

0.8

1:30
1:50
1:80
1:120(c)

0.6

0.4

0.2

0
7.5

88.5

99.5

10

10.5

11

1:120 Mag. 1K

Wavelength [µm]

(a)

(b)

1:80 Mag. 2K(d)1:80 Mag. 10K

1:120 Mag. 7K

Exp. 2 Mixture
1Qext(λ) / Qext(Peak)
Normalized
Extinction

0.8( monosphere vs. irregular shape)

Peaks (d=0.5µm (8.93µm) & d=5.0µm (9.49µm))

1:30 (Sphere)

Sphere Irregular ∆λ1:30 8.94µm 8.95µm 0.01µm
9.47µm 9.17µm 0.30µm
1:50 8.95µm 8.96µm 0.01µm
9.45µm 9.20µm 0.25µm

1:50 (Sphere)
1:30 (Irregular)
1:50 (Irregular)

0.5 µm monosphere :crashed 5 µm particles

0.6 Survived 0.5 µm
particles show a clear
peak at 8.94 µm.

0.40.207.588.5

99.5

Wavelength [µm](a)(b)1010.511

 The peak at 9.5 µm of
the 5 µm particles isstrongly influenced by
the morphologicalchanges (size &shape).

Exp. 3 Metal Content
Olivine MgxFeySiO4
Mg1.9Fe0.1SiO4 (Peridot)
Mg1.6Fe0.4SiO4 (Sri Lanka)

Peridot

Sri Lanka(Aerosol measurements)
1.2

Peridot
Peridot
(Mg

11.07
11.11

SriLanka
Lanka
Sri(MgNormalized Extinction

10.8

1.95

9.89
9.94
19.04
19.04

0.6

Fe

1.56

0.16

FeSi

0.91

0.40SiO)
40.91O)
423.4623.91

spectra shift tolonger WL

16.24
16.38

0.4

33.50
33.97

0.2

(Koike et al. 2003)

0891020
Wavelength [µm]More Fe3040

Astronomical Application
NameSpec.
type

Distance(pc)Age(Myr)planets

IRS
spectrum

Remarks

Reference

β Pic

A5 V

1912++-Chen `07

η Tel

A0 V

4812-+

Wide binary

Chen `06

Warm dust thermal emission: Infrared excess
HD 113766F3/5 V130

10-16-+

Wide binary

Lisse `08

HD 191089

F5 V54?

-+-Chen `08

BD+20307

G0 V92>300-+

Close binary

Zuckerman `0869830
K0 V main sequence
132000 stars?
3 (<0.7AU)+ have warm-dustLisse `07
 HDAbout
30known toς Lep
A2 V
22300+
Chen `06
emission(i.e. at 10-50µm)
HD 12039
G3/5 V
42100 ?
?
HD 86087

A0 V

98

50-+-Chen `06

η Crv

F2 V

18600 ?

-+-Chen `06

 HDa181327
few objects
havestrongemission
at λ+ ~10 µmF5/6 V
51?
HD72905
G1.5T
V > 200K)
14400+(requires

Chen `06
Beichman `06

HD 172555

A5 IV/V

2912-+

Wide binary

Lisse `09

HD 145263

F0 V116?

---

Honda `04+-

Chen `06

110058 forA0mineralogical
V10016
 HDBestanalysis
β Leo

A3 V

1150-

-

binaryChen `06

HD 23514

F6 V120100--?

-Rhee `08

HD 169666

F551

2200

-+-

Abraham `08

HD 202406

F2 IV/V-----

Smith `08

HD 106797

A0 V

96>10---

Fujiwara `09

Some main sequence stars known to have warm dustSpitzer IRS Spectra – what can be infered from them?
 Crystalline olivine bands vs. 9.8 µm amorphous silicate band Short-wavelength wing (9.3µm) indicates presence of pyroxenes or SiO2
 Grain sizes: large grains (> 1 µm) should broaden 10 µm band to longer
wavelengths lack of small grains should flatten the band strongly
Arrows: am.
band, cryst. Olivine
bands,spectrum
pyroxenes/SiO2
ExampleofSilicate
a large-grainemission

 Small grains dominating(surprising because ofblowout limits, butbiased by selection)

Large grains

Moor et al. 2009

Detailed mineralogical analyses (Lisse et al.)Spitzer HD 113766 Disk Spectral Model

Lisse et al. 2009 (accepted)

HD 172555 (A5 star)

HD 113766 (F3/5 binary)

40 % silica and tektite,
35% olivines and pyroxenes,SiO gas, hypervelocity collision !
29 % olivines, 14 % pyroxenes,
12 % amorphous silicate
21 % FeS, 12 % ice
Warm asteroidal dust (T=450K) at
1.8 AUIcy dust at 4-9 and 30-80 AU

Some concerns:
 Some of the identified minerals do not have distinct

bands, they just contribute to continuum emission
and they can hardly be distinguished.
 Most of the comparative spectra have been obtained bythe embedded dust samples, which make a different
band profile.
 The grain shape influences the band profiles.

Are such detailed fits possible at all?

Our approach: Dominating minerals first, consider grain
shape effects (also composition and sizeeffects) on sharp bands
 Use spectra of well-defined particulates(known shape and size) dispersed in N2gas – aerosol spectraFirst steps: Some own fitting tests for HD 69830– IDL programme IRSA by Lutz BornscheinSome own fitting tests for HD 69830
100 % Mg
+ Largeforsterite60%Mg• Beichman et al. (2005): Spitzer IRS• T(dust) ~ 400K
• M(dust) ~ 1000 zodi

K0 V
13 pc
2000 Myr ?
3 planets

Intention: simplification, search for real
„hard facts“ (constraints on dustmixture)
Used dust spectra:- olivines and pyroxenes from aerosol
measurements- Koike et al. (2003) olivines- amorphous silicates- „carbon“ for grey emission (may alsomimic colder dust component)

Three-component model:• Fo60+ olivine (synthetic, Koike)• Astronom. Silicate (amorphous, D&L93)• „carbon“ cold dustBest fit for HD69830[µm]

DatabasePeak Search: to search for yourdesired spectra via inputting a peakposition.

Basic information: Chemicalformula, density, particle size,
product info., etc…

Plot: Aerosol and CsI pellet
measurements. Numerical data setsare downloadable.

Images: obtained by scanning andtransmission electron microscopes(SEM & TEM)
Created by David Schmitz

http://elbe.astro.uni-jena.deSummary<Large-sized particles vs. Small-sized particles (Forsterite)> Peak positions are not strongly influenced by the particle size, butthe bandwidth beyond the 11 µm peak is significantly broadened.

<Mixture of Small- and Large-sized particles (SiO2)>

 Even mass of the 0.5 µm monosphere particles is 120x less thanthat of the 5 µm ones, the peak of the 0.5 µm particles clearly
appears on the extinction spectrum.

<Metal Content in Olivine> Peaks of Fe-rich olivine take place at slightly longer WL in aerosol
measurements as well.

<HD69830>
 Emission spectrum of HD69830 fits well with Fe-rich olivine
spectrum obtained by aerosol measurement.