a dyson’s dream - dusty early-type galaxies nicky agius * a.e. sansom, c.c. popescu, g. natale +...

A Dyson’s Dream - Dusty Early-Type Galaxies

Nicky Agius*A.E. Sansom, C.C. Popescu, G. Natale

+ GAMA + H-ATLAS

*NKAgius@uclan.ac.ukhttp://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

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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

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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

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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.

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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