Ant Jones

1
The Physics of Dust

• Ant Jones Isabelle Ristorcelli
• IAS, Orsay, FRANCE CESR,
  Toulouse, France

Planck WG 7 meeting, Catania, 15th - 17th January
2007
2
OutlineI. The Physics of DustII. Planck WG
7.1 - a status report
3
Dust properties

• Chemical/mineralogical composition
• silicates, oxides, (hydro)carbons, carbides,
• Size distribution
• nm - µm, power-law, log normal,
• Shape
• spheroidal, ellipsoidal, needles,
• Structure
• amorphous, crystalline, solid, porous
• mantles of hydrocarbons and/or ices
• Charge state
• Z(a,T)
• Size and T-dependent properties
• ERE, Eg(a) , ?(T),

ERE Extended Red Emission Eg(a) band gap
dependence on particle size ?(T) dust
emissivity slope for a given ? range
4
Dust properties

• Chemical/mineralogical composition
• silicates, oxides, (hydro)carbons, carbides,
• Size distribution
• nm - µm, power-law, log normal,
• Shape
• spheroidal, ellipsoidal, needles,
• Structure
• amorphous, crystalline, solid, porous
• mantles of hydrocarbons and/or ices
• Charge state
• Z(a,T)
• Size and T-dependent properties
• ERE, Eg(a) , ?(T),

5
What determines the long ? and low T behaviour of
dust?

• dust microscopic structure
• amorphous, crystalline
• inclusions, defects and disorder
• density, fractal dimension
• very low energy structural transitions (e.g.,
  TLS)
• dust macroscopic structure
• presence of hydrocarbon and/or ice mantles
• porosity
• coagulation
• dust IR emission is determined by the chemical
  structure and the FIR/mm emission is controlled
  by the wings of these bands
• ? asymptotic behaviour with a T-independent
  spectral index ? 2, as per the Draine Lee
  astronomical silicate

6
Theory-laboratory-observation synergy
astrophysical observations IR/mm emission
spectrum
theoretical modelling of the dust physics
theoretical modelling of the dust
astrophysical proceses
laboratory measurements IR/mm emission spectrum
7
The effects of dust mantles
N.B. The silicate dust emissivity slope flattens
with the addition of a carbon mantle
8
The effects of dust mantles
N.B. The dust emissivity slope steepens with the
addition of a water ice mantle
9
Mennella et al. (1998)
forsterite c-Mg2SiO4
295 K 24 K
10
fayalite c-Fe2SiO4
295 K 24 K
Mennella et al. (1998)
11
amorphous fayalite a-Fe2SiO4
295 K 24 K
Mennella et al. (1998)
12
amorphous carbons
295 K 24 K
295 K 24 K
Mennella et al. (1998)
13
The current laboratory data
a- amorphous c- crystalline
amorphous carbons
Agladze et al. (1996) Mennella et al. (1998)
14
Recent laboratory measurement of dust analogues
emissivities
Extends the measurements of Mutshke et al.
(Jena)
A significant absorption dependency on T and ?
for all tested samples (amorphous silicates)
Need to extend the analysis to other analogues
(silicates, carbons ) chemically synthesize the
new analogues study the influence of the defects
(OH, Mg2, amorphization degree, )
Boudet et al. 2005, ApJ, 633, 272
15
Anomalous heat capacities in amorphous materials
Increase in the heat capacity at low
temperatures T lt 30 K Two-level tunnelling
States (TLS) W.A. Phillips (1987) Rep.
Prog. Phys. It is clear, therefore, that
the unexpected thermal properties arise from
additional excitations which both scatter
phonons and contribute to the heat capacity.
16
Two-level systems
Two-level tunnelling States e.g., W.A.
Phillips (1987) Rep. Prog. Phys.
tunnelling of the atom from one minimum
to another gives rise to the very small energy
splittings (less than 0.0001 eV) needed
0.0001 eV 1.2 K 1.2 cm 24 GHz the number
of atoms contributing at low temperature in only
a very small fraction of the total
17
Microwave emission excess
24 GHz
thermal emission from large
grains
data points taken from de Oliveira-Costa et al.
1999
18
Observed variations in the dust emissivity
spectral index
N.B. The dust emissivity slope steepens as the
temperature decreases
Serra et al. (2000)
19
Low temperature effects on the dust emission
20
Low temperature effects on the dust emission
21
Dust Evolution
22
The lifecycle of interstellar dust
Ant Jones, IAS, Orsay
23
Evolution of the interstellar dust size
distribution

• Processes that affect the dust size distribution
• Erosion in gas-grain collisions
• Fragmentation in grain-grain collisions
• Coagulation in grain-grain collisions
• Mantle accretion in gas-grain collisions

24
Processes that effect the grain size distribution

Grain mass dn(m)/da
initial MRN size distribution
5 nm
250 nm
25
Processes that effect the grain size distribution

Grain mass dn(m)/da
initial MRN size distribution
5 nm
250 nm
26
Processes that effect the grain size distribution

Grain mass dn(m)/da
initial MRN size distribution
5 nm
250 nm
27
Processes that effect the grain size distribution

Grain mass dn(m)/da
initial MRN size distribution
5 nm
250 nm
28
Processes that effect the grain size distribution

Grain mass dn(m)/da
initial MRN size distribution
5 nm
250 nm
29
Diffuse cloud extinction
fragmentation
coagulation
Cardelli et al. (1989)
30
Coagulated/porous grains
but how to calculate the temperature?
but how can we calculate the temperature
of such particles?
Wolff et al. (1994)
31
Coagulated/porous grains
but how to calculate the temperature?
but how can we calculate the temperature
of such particles?
Dominik Tielens (1997)
32
Grain coagulation
10-30
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T1 T2 T1 gt T2
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l.Il/NH W/H atom
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10-31
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10-32
1
10
100
1000
l µm
small grains / large grains
10-2
Qabs
N.B. The effect of coagulation is to flatten the
slope of the dust emissivity, i.e.
opposite to that of the ?(T) effect for
decreasing temperature, and for ice mantles.
10-4
1000
0.1
10
Stepnik et al. (2001)
l µm
33
The dust SED
34
(No Transcript)
35
SPITZER
HERSCHEL
PLANCK
JWST
?
36
Dust SED Variations
37
Dust SED Variations
38
Dust SED Variations
39
Dust SED Variations
40
Dust SED Variations
41
The reality here

• is that we, ideally, need to unravel the
  degeneracies inherent in the various processes
  that determine the form of the dust emissivity at
  FIR-mm wavelenghs.
• Clear need for ancillary observational data at
  MIR-FIR wavelengths and for laboratory data at
  MIR to mm wavelengths in order to break the
  degeneracies.

42
The various effects and the slope of the dust
emissivity

• The spectral slope ? gets steeper (gt 2 ? ) or
  less steep ( lt 2 ? )
• dust microscopic structure
• amorphous ( ? ), crystalline ( ? )
• very low energy structural transitions (e.g.,
  TLS) ( ? )
• dust macroscopic structure
• presence of hydrocarbon ( ? ) and/or ice mantles
  ( ? )
• porosity ( ? )
• coagulation ( ? )

43
Conclusions

• Consolidate what we now know ? models/data
  interpretation
• Study of low Tdust long ? (FIR-cm) effects on
  dust properties
• size (stocastically-heated grains contributions?)
• shape (spheroids, ellipsoids, needles, )
• state (crystalline, amorphous, porous, )
• low T physical effects (TLS, )
• inhomogeneities / refractory ice mantles
• porosity / coagulation
• Dynamics, dynamics, dynamics, dynamics, dynamics,
  ...
• the dynamical evolution of the dust size
  distribution
• coagulation, accretion, disaggregation,
  fragmentation, erosion
• microphysics of coagulation and the physical
  state of the ISM
• ? Lab data, lab data, lab data, lab data, lab
  data, ...

44
Planck WG 7.1 - The Physics of DustA status
report
45
Planck WG 7.1 - The Physics of dust

• What have we done to get funding (i.e. post-docs
  equipment)?
• European FP6 proposal PI Steve Eales (UK)
• SSSOLEX proposal PI Ant Jones (France)
• IAS/CESR 2006 ANR proposal PI Ant Jones (France)
• (2006 proposal on silicate evolution, UK PI)
• None of the above were funded!
• Where are we now and what do we have?
• publications on dust physics al long ? low T
• Stepnik et al. (AA, 2001) - the effects of
  coagulation on the long ? dust emission
• Boudet et al. (ApJ, 2005) - long ? low T dust
  lab. measurements
• Meny et al. (AA, 2007) - theory/modelling of
  dust physics at long ? low T
• Meny et al. (Les Houches, 2007) -
  theory/modelling of dust physics at long ? low
  T
• Les Houches, May 2006 meeting proceedings
  motivated by the needs of Planck and Herschel
  (contributions by Alexander, Draine, Dwek,
  Gail, Guillet, Henning, Joblin, Jones, Leroux,
  Mennella, Tielens, ..)
• we have The Planck Dust Document that outlines
  a plan of action for the needed studies
• long ? low T lab. capabilities ?m to mm (IAS,
  CESR, Cardiff, Jena, Naples, )
• collaboration (IAS, CESR, Cardiff, Jena, )
  following the 2006 Les Houches meeting
• kick-off meeting(s) in the planning stage (1.
  microphysics of dust/lab. Expts. 2. dust
  modelling)

46
2006 IAS/CESR ANR Proposal

• AIMS
• Consolidate research at the IAS (Interstellar
  Matter and Cosmology) and the CESR (Cold
  Universe)
• To combine expertise in observation programming,
  data processing, theory, modelling and laboratory
  experiments
• MOTIVATION
• Dust studies should now be integrated within the
  context of the physical and chemical evolution of
  matter in interstellar space.
• Progress in our understanding of interstellar
  dust has always come from the comparison of new
  observations with laboratory experiments.
• Before the launch of Herschel and Planck a
  similar investment, as for ISO, is necessary to
  further the study of FIR/mm dust emission.

47
2006 IAS/CESR ANR Proposal

• The key questions relating to the nature of dust
  driving the project were
• What physical processes control the composition,
  optical properties, structural state, abundance
  and size distribution of dust in the ISM?
• What local physical conditions determine the
  evolution of these properties?
• How can astronomers best interpret the FIR/mm
  dust emission?
• Our goal was to develop the observational
  background, modelling tools, theoretical
  framework and experimental set-up necessary to
  interpret FIR/sub-mm dust observations.
• Our project was to bring together the necessary
  key elements that, without the ANR, would
  probably remain fragmented and incomplete.

48
THE END
49
Interstellar shocks and dust processing
50
Dust destruction and disruption processes

• Atomic/ionic collisions
• Grain-grain collisions

inertial sputtering
Vrel
Vthr 35 km/s
thermal sputtering
Tthr few x 105 K
vaporisation
Vthr 20 km/s
Vrel
shattering
Vthr 1-2 km/s
51
Post-shock grain size distribution

Jones (2004)
52
Post-shock grain size distribution

Grain volume / H nucleus
initial MRN size distribution
Jones (2004)
5 nm
250 nm
53
Grain coagulation
Mizuno et al. (1988)
54
The evolution of dust in the ISM
55
The evolutionary cycle of interstellar silicates
evolved stars amorphous crystalline
silicates (olivine pyroxene)
56
The evolutionary cycle of interstellar carbons
strong radiation fields will process
a-CH rendering it a more aromatic,
low-density material which can fragment into
its constituent molecular components
evolved stars amorphous hydrocarbons (a-CH), PAH
s
57
Observed dust properties in molecular clouds

• Decrease in the small grain abundance
• Prusti et al. 1991, Abergel et al, 1994 IRAS
• Laureijs et al. 1996 ISOPHOT
• Stepnik et al. 2001 IRAS PRONAOS
• Decrease in the big grain temperature
• Lagache et al. 1998 COBE
• Bernard et al. 1999 PRONAOS
• Hotzel et al. 2001 ISOPHOT
• Stepnik et al. 2001 IRAS PRONAOS
• Increase in the sub-mm emissivity
• Cambrésy et al. 2001 DIRBE
• Stepnik et al. 2001 IRAS PRONAOS

58
IRAS 60 µm/100 µm ratio
Prusti et al (1991)
59
Variation in the dust sub-mm emissivity

• Filament in Taurus cloud
• Nearby molecular cloud (140 pc)
• AV 2, nH103-104 cm-3
• No embedded stars
• Shows IRAS colour variations
• TDIRBE 13-14 K

60
IRAS/PRONAOS observations
Stepnik et al. (2001)
61
Variation in the dust sub-mm emissivity
EVOLUTION
- decrease in the small grain abundance by 90 -
increase in the sub-mm emissivity by a factor of
3-4 - decrease in the big grain temperature to 12
K
Stepnik et al. (2001)
62
Diffuse cloud extinction
RV 3.1
silicate
graphite/10
RV 5.3
silicate
graphite/10
Kim et al. (1994)