A Dyson’s Dream - Dusty Early-Type Galaxies
Nicky Agius*A.E. Sansom, C.C. Popescu, G. Natale
+ GAMA + H-ATLAS
*[email protected]://www.star.uclan.ac.uk/~nka/index.html
Nicky Agius Jeremiah Horrocks Institute, UCLan
Breakdown
1. Intro: Early-Type Galaxies (ETGs)2. Intro: Early-Types with dust3. GAMA and Herschel-ATLAS4. Properties of ETG samples5. Modified BB and SED fitting6. Case Studies
Nicky Agius Jeremiah Horrocks Institute, UCLan
Old vs. New Tuning Forks
Capp
ella
ri et
al (
2011
)
Credit: http://www.sdss.org
How can we differentiate between galaxy types?
Elliptical Lenticular SpiralRed bulge Red bulge Red bulgeSmooth Profile Blue/Red extended disk Bluish arms/extended diskHigh surface brightness Moderate surface
brightnessModerate surface brightness
Circular/elongated Elongated Spiral armsLittle or no dust lane Dusty? DustyAbsorption lines only Emission + abs. lines? Emission + absorption lines
No rotation Rotating disk Rotating diskFound in clusters Found in all environments Found in all environments
Classification and Morphology of External G
alaxies – G. de Vaucouleurs
Early-Type Galaxies Late-Type Galaxies
CenA – Marina Rejkuba (ESO-Garching)
M87 – David Malin (AAO)
M86 –NOAO/SCIENCE PHOTO LIBRARY
M74 - NASA - Hubble
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Peng, 2010:Sérsic Profiles
Conselice, 2006:Red Sequence + Blue Cloud
Dressler, 1980:Morphology-Density Relation
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APOD – dust lane
Knapp (1999) – connects cold gas and dust
Ellipticals: originally no observed cold gas – hot (106 - 107K) ionised gas – dust destroyed in situ (sputtering)(EINSTEIN, ROSAT, ASCA observations)
Adding some stardust
Nicky Agius Jeremiah Horrocks Institute, UCLan
Planck Function:
ISM Emission
Radio = cold neutral gas
FIR/sub-mm = cold dust
MIR = warm dust
Optical/UV = stellar light =
HII emission
X-ray = hot ionised gas
Hartigan, Palmer & Cleeves (2012)
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Hierarchical Formation?
Georgakakis et al (2001) – dust masses don’t come from old stars
Scenario: Elliptical with no interactions within sputtering timescale ≈ 107 – 108 years
= no dust!!
Questions: E’s with significant dust masses not yet achieved massive end-stage Elliptical status?Can dust be used as a smoking gun?
Shabala et al (2012) – dusty ETGs have higher SFRs
Galaxy and Mass Assembly
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Driver et al (2009)
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Herschel-ATLASCredit: esa.org
Largest Open-Time Key Project with Herschel
PACS – 100μm & 160μm
SPIRE – 250μm, 350μm & 500μm
Full survey: 550 deg2, ~200,000 detections, zmed~1
Source extraction described in Rigby et al, 2011
~66,500 Phase 1 detections:
=10,000 GAMA matches over 160 deg2
Parallel Mode
Eales et al (2010), Poglitsch et al (2010), Griffin et al (2010)
PACS 100μm PACS 160μm SPIRE 250μm SPIRE 350μm SPIRE 500μm
FWHM 8” 12” 18” 25” 36”
5σ Noise 132mJy 126mJy 32mJy 36mJy 45mJy
Our Sample Aims
High fidelity sample of dusty ETGS PACS + SPIRE data (H-ATLAS) UV/Optical/NIR data (GAMA) MIR data (WISE)
Control sample of non-dusty ETGs Undetected in FIR/sub-mm UV/Optical/NIR data (GAMA)
Kelvin et al (in prep) Parent Sample for optical classifications
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Parent Sample
GAMA CAT
0.013<z<0.06
rpet ≤ 19.8 mag
Mr ≤ -17.4 mag
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Kelvin et al (in prep)
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Active Galactic NucleiBPT Diagram – Baldwin et al (1981); Kauffmann et al (2003a)
Foster et al, in prep
- Use GANDALF software to measure emission lines to get
ratios shown here.
Submm detections: 8 AGN of 17
Non-detections: 93 AGN of 175
Nicky Agius Jeremiah Horrocks Institute, UCLan
SubS OptS
E + S0a+
Ellipticity (1-(b/a) ≤ 0.7)+
Redshift (0.013≤z ≤ 0.06)+
Remove AGN+
Remove spiral arms+
Sub-mm detections=
220 ETGs (5.4% of eyeballed sample)
E + S0a+
Ellipticity (1-(b/a) ≤ 0.7)+
Redshift (0.013≤z ≤ 0.06)+
Remove AGN+
Remove spiral arms+
Sub-mm undetected=
551 ETGs (13.4% of eyeballed sample)
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Sample Properties
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Agius et al (submitted)
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Basic FIR/Sub-mm Properties
Dust in Galaxies
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Single component – isothermal fittingo Modified BB equation
with β=2.0 (Draine & Li, 2007)
o Fit galaxies with SPIRE emission ≥ 3σ o Dust mass and temperature
– K = k-correction– DL = luminosity distance
– κ250 = absorption coefficient = 0.89m2kg-1 (Dunne et al, 2011)
Dust Mass:
Modified Blackbody Fits
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Isothermal Fitting Results
3σ sample
Td,mean 22.1K
Td,range 9-30K
Md,mean 1.8×107M
Md,range (0.08-35) ×107M
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Problems with isothermal fitting
1 componentTry two/multi-component fitting
Only outputs dust mass & temperatureFit other wavebands
What if collisional heating contributes?Use dust templates
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SED Template Fits
Multiple components – Radiative Heating Diffuse radiation field template PDR/HII radiation template
Additional component – Collisional Heating
Fischera et al (2011), Natale et al (2010)
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SED Template Fits
Multiple components – Radiative Heating Diffuse radiation field template
Dust heated by the diffuse ISRF in galaxy Dust comp: graphite, silicates & PAHs Fits vary intensity & colour of radiation field Quantifies emission heated by old/young stellar populations Dust emission calculated taking into account the stochastic
fluctuations of dust grains
Fischera et al (2011), Natale et al (2010)
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SED Template FitsPAH line emission FIR cold dust emission
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SED Template Fits
Multiple components – Radiative Heating Diffuse radiation field template PDR/HII radiation template
Quantifies obscured ongoing SF Popescu et al (2011) for more details Template: MW SF region fit + Groves et al (2008) model
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SED Template Fits
Photodissociation (PDR/HII) Region
Contribution
Diffuse Contribution
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Testing the Dust Distribution
Fit MIR/FIR/sub-mm data – diffuse + PDR fit WISE: 12μm & 24μm H-ATLAS: 100μm, 160μm, 250μm, 350μm & 500μm
Use output fit parameters: χcol and χUV
compute energy density (Urad,gal ) of dust disk Assume dust in ETGs is localised in a central disk Use RT spheroidal models to find radius of disk
Match Urad,gal with Urad,mod(R)
Nicky AgiusLunchtime Talk – St-AndrewsJeremiah Horrocks Institute
zrscale = 5670 pczscale = 90 pc
Varying parameters:τB = 0.1, 0.3, 0.5, 1.0, 2.0, 4.0, 8.0n = 1.0, 2.0, 4.0, 8.0Dust model: Weingartner & Drain (2001)
rQ=r/R
Model:
R
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Test Galaxies
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Preliminary Results
In Conclusion
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Two groups of ETGs:– 1. High Md/M, low n, blue NUV-r
– 2. Low Md/M, high n, red NUV-r Suggests younger population of ETGs
which will continue to evolve – but no M* diff. The geometrical distribution of dust in these
ETGs could help identify how they are evolving.
Nicky Agius Jeremiah Horrocks Institute, UCLan
Bulge-Disk Decomposition
Ideal for separating Es from S0s Lackner & Gunn (2012) performed B+D for SDSS
galaxies up to z=0.05 SDSS image quality not high enough for B+D up to
z=0.4 - Waiting for VST/VISTA
Lackner & G
unn (2012)
Centrally concentrated
Elliptical Galaxy Artist’s Impression(sort of)
CenA – Marina Rejkuba (ESO-Garching)M87 – David Malin (AAO) M86 –NOAO/SCIENCE PHOTO LIBRARYNicky Agius Jeremiah Horrocks Institute, UCLan
Dark Matter Halo
Many globular clusters
Mostly Red