Dust production
by evolved stars in
the Magellanic Clouds
and other galaxies
Ciska Kemper
Academia Sinica, Institute of Astronomy and Astrophysics
The life cycle of dust
The life cycle of dust
SAGE-LMC: The Large Magellanic
Cloud in the infrared
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Z ~ 0.5 Z⊙
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D = 50 kpc
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Meixner et al. 2006
Global view of nearby
galaxy
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8.5 million IR point
sources
IRAC-[3.6]; [4.5];
[5.8]; [8.0]
MIPS-[24]; [70]; [160]
SAGE-SMC: The Small Magellanic
Cloud in the infrared
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Z ~ 0.2 Z⊙
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D = 60 kpc
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Gordon et al. 2011
~2 million
infrared point
sources
Defining stellar populations
in the NIR
Blum et al. 2006
Tracing dust in the mid-infrared
Blum et al. 2006
AGB stars: Main dust producers
Srinivasan et al. 2009
Boyer et al. 2011
Extreme AGB stars: J-[3.6] > 3.1
Blum et al. 2006
Srinivasan et al. 2009
Boyer et al. 2011
SAGE-Spectroscopy
Kemper et al. 2010
~200 Spitzer-IRS 5-40 um point sources
~800 archival Spitzer-IRS staring mode
targets
23 Spitzer IRS data cubes of ISM regions
MIPS SED data of selected regions
Carbon stars: GRAMS
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Representative fit: 12
wt.% SiC (10-16%)
Model grid: 10% SiC,
90% amorphous carbon
Srinivasan et al. 2010; 2011
Oxygen-rich dust in the LMC
Sargent et al. 2010, 2011
Amorphous silicates → GRAMS
Total dust production
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LMC – Riebel result
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SMC – Srinivasan
result
Riebel et al. 2012
For SMC, total dust production a
factor of ~2 lower.
Srinivasan et al. in prep.
However,
things may not be what they seem
Point sources in the SMC targeted
with IRS staring mode
Ruffle, Kemper et al., submitted
Woods et al. 2011
Ruffle et al., submitted
Woods et al. in prep.
Classification quality control
Ruffle, Kemper et al., submitted
Classification quality control
Ruffle, Kemper et al., submitted
One size (composition) may not fit all
Carbon stars: SiC/C = 10%?
SiC (11.3 um)
MgS (~30 um)
Category includes extreme AGB stars
Continuum:
Graphite
Amorphous carbon
Leisenring, Kemper & Sloan, 2008
SiC and MgS feature strengths
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SiC decreasing with
dM/dt
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Leisenring, Kemper & Sloan 2008
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SiC (11.3 um) ↓ and
MgS (30 um) ↑ as
dM/dt ↑
MgS: ~6 wt.%, but
only in fraction of
stars (Groenewegen et al. 2009)
But: SiC seen in
absorption at highest
dM/dt (Gruendl et al. 2008)
SiC constant?
SiC optical depth effects
Gruendl et al. 2008
Speck et al. in prep
The 30 micron feature: MgS or
carbon?
Otsuka, Kemper et al. 2014
Crystalline silicates in the LMC
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O-AGBs and RSG in the LMC, SMC and MW
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dM/dt determined with GRAMS
Jones, Kemper et al. 2012
Crystallinity of silicates
The glass temperature Tglass ~1000 K for silicates
( Tevap ~1500 K )
Tcond > Tglass: atoms in mineral are mobile, crystallization
may occur
Tcond < Tglass: immediate freeze out → amorphous silicate
Crystalline silicates
Sogawa & Kozasa 1999
Depending on dust density: annealing
Depending on gas density: direct condensation
Jones, Kemper et al. 2012
Crystalline silicates
Sogawa & Kozasa 1999
Annealing
Depending on gas density: direct condensation
Jones, Kemper et al. 2012
Crystalline silicates
Crystalline fraction
< 5%
Kemper et al. 2001
Jones, Kemper et al. 2012
Extending the O-rich GRAMS grid
with alumina
Jones, Kemper et al. 2014
Total injection budget in the LMC
Object Type
Mineralogy
Dust production rate
O-rich AGB
95% am. sil.; 5% cryst. sil.
0.14 ~ >0.4 x 10-5
C-rich AGB
88% am. carbon; 12% SiC;
var.% MgS
0.24 x 10-5
Extreme AGB
88% am. carbon; 12% SiC;
var.% MgS
2.36 ~ ≤4.3 x 10-5
Red Supergiants
95% am. sil.; 5% cryst. sil.
0.2 x 10-5
total
77% am. carbon; 11% SiC; (4 +/- 1) x 10-5
12% am. sil.; <1% cryst.
sil.; ?% MgS; ?% oxides; ...
Kemper 2013
ISM dust
comparison
Cox & Spaans 2006
SiC
Crystalline silicates,
MgS?, oxides
Amorphous
silicates
Amorphous carbon
LMC injection
Kemper 2013
MW ISM composition
Tielens et al. 2005
Comparison with ISM dust and
SFR in the LMC
● Dust MLR: (2-4) x 10-5 M⊙/yr
● ISM dust mass: (7.3 ± 1.7) x 105
M⊙
● SFR: 0.38 M⊙/yr (gas)
● replenishment time scale: 1010 yr
(comparable to age of LMC)
● astration time scale: 108 yr
Skibba et al. 2012, Gordon et al. 2014
Riebel et al. 2012
Modelling the dust production
history
Harris & Zaritsky 2009
● theoretical dust yields of AGB stars
● over the entire SFH of the LMC
● no interstellar dust destruction
Schneider et al. 2014
Do we see all the dusty stars?
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lll
Riebel et al. 2012
Boyer et al. 2010
Dust production in other galaxies:
M32
Derived DPR: 1.5 x 10-4 M☉/yr
5 most extreme sources: 30% of DPR
Jones et al. 2015;
Davidge 2014
Dust production in other galaxies:
M33
-5
DPR: ~5 x 10 M☉/yr
problem: 8 μm excess
Javadi et al. 2013
Future prospects
A search for extreme AGB stars
● A handful of these dominate the dust
production
● Obtain mid- far-infrared part of SED of
nearby and more distant candidates
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e.g. F24 > F8 (Boyer et al. 2011)
Milky Way
Magellanic Clouds
M32, M33, etc.: extreme AGB stars are among the
brightest sources beyond 20 microns
● Study mineralogy for nearby counterparts to
constrain dust composition
Mineralogy in the mid-infrared
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(Crystalline) silicates
Water ice (crystalline and amorphous)
Carbonates
Hydrated silicates (clays)
21 micron feature
30 micron feature (MgS or graphite)
Redshifted
What do we know about SN dust?
Dominated by ‘proto-silicates’
Rho et al. 2008
Most prominent feature in Cas A:
21 micron
Some starburst galaxies have
silicate crystallinities of 6-13%
Spoon et al. 2006
Kemper et al. 2011
Quasar foreground absorber
(Damped Lyα system) with a
crystallinity of 95%
Aller et al. 2012
SKIRT radiative transfer of starburst
galaxies with crystalline silicates
Kemper, Baes et al. in prep.
Conclusions: stellar dust production
in galaxies
● LMC/SMC: SAGE results constrain dust budget:
○ integrated dust production matches interstellar reservoir
○ composition deviates significantly
○ interstellar dust destruction / grain growth not taken into
account
○ dust production dominated by extreme AGB stars
○ contribution by supernovae unknown
● Similar studies underway for Local Group
galaxies →JWST follow-up
● Dust production by massive stars in starburst
galaxies to be measured in the IR (SPICA?)