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Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds Hony and Spitzer/SAGE-SPEC team Galliano, Seok, Neelamkodan, Kemper, Madden, Indebetouw, Gordon, Sandstrom 11 Aug 2017 S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 1 / 20
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Page 1: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Polycyclic Aromatic Hydrocarbon from the MagellanicClouds

Hony and Spitzer/SAGE-SPEC teamGalliano, Seok, Neelamkodan, Kemper, Madden, Indebetouw, Gordon,

Sandstrom

11 Aug 2017

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 1 / 20

Page 2: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Overview

1 Introduction: Polycyclic Aromatic HydrocarbonsAstronomical PAH bandsMain interest (tracers, photo-electric heating)

2 This studyMain objectivesPresentation of regions

3 Results and discussionFeature mapsTrendsDifferences between SMC and LMCResolution matters

4 Conclusions

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 2 / 20

Page 3: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands

What are PAHs?

NGC 7027

3 4 5 6 8 10 12Wavelength [µm]

Family of strong, broad emission bands in the mid-IR

Main fingers at 3.3, 6.2, 7.7, 7.9, 8.6, 11.2 and 12.7 µm

Found in many types of ISM and CSM, including harsh conditions

Stable

From abundant elements

Identified with resonances inaromatic macro-molecules

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 3 / 20

Page 4: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands

What are PAHs?

NGC 7027

3 4 5 6 8 10 12Wavelength [µm]

Family of strong, broad emission bands in the mid-IR

Main fingers at 3.3, 6.2, 7.7, 7.9, 8.6, 11.2 and 12.7 µm

Found in many types of ISM and CSM, including harsh conditions

Stable

From abundant elements

Identified with resonances inaromatic macro-molecules

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 3 / 20

Page 5: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands

What are PAHs?

Family of strong, broad emission bands in the mid-IR

Main fingers at 3.3, 6.2, 7.7, 7.9, 8.6, 11.2 and 12.7 µm

Found in many types of ISM and CSM, including harsh conditions

In the context of star formation:PAH emission from the edges ofilluminated clouds

Puga+09

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 4 / 20

Page 6: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Introduction: Polycyclic Aromatic Hydrocarbons Main interest (tracers, photo-electric heating)

Why are they interesting?

Astronomical:

Strength used as SFR indicator

Equivalent Width is used as AGN diagnostic

Black: low-metallicity starburstsRed: 12+(O/H) > 8.35Green: 8 < 12+(O/H) < 8.35Blue: 12+(O/H) < 8

Calzetti 2010

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 5 / 20

Page 7: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Introduction: Polycyclic Aromatic Hydrocarbons Main interest (tracers, photo-electric heating)

Why are they interesting?

Astronomical:

Strength used as SFR indicator

Equivalent Width is used as AGN diagnostic

Black: low-metallicity starburstsRed: 12+(O/H) > 8.35Green: 8 < 12+(O/H) < 8.35Blue: 12+(O/H) < 8

Calzetti 2010

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 5 / 20

Page 8: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Introduction: Polycyclic Aromatic Hydrocarbons Main interest (tracers, photo-electric heating)

Why are they interesting?

Astronomical:

Strength used as SFR indicator

Equivalent Width is used as AGN diagnostic

Physical influence:

Source of free electrons in the neutral gas: dominatethe gas heating via photo-electric effect (PE)

PE-efficiency depends on charge state(Bakes&Tielens 1994)

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 6 / 20

Page 9: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Introduction: Polycyclic Aromatic Hydrocarbons Main interest (tracers, photo-electric heating)

Why are they interesting?

Astronomical:

Strength used as SFR indicator

Equivalent Width is used as AGN diagnostic

Physical influence:

Source of free electrons in the neutral gas: dominatethe gas heating via photo-electric effect (PE)

PE-efficiency depends on charge state(Bakes&Tielens 1994)

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 6 / 20

Page 10: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Introduction: Polycyclic Aromatic Hydrocarbons Main interest (tracers, photo-electric heating)

Band ratio variations: varying charge state

Strong observed variations

CC (6-9 µm) vsCH (3.3 and 11.2 µm)

CC modes activated by chargemeasured by Spitzer/IRAC4

Charge-balance follows G0/ne

Possible spatial trendswith respect to the exciting stars

Understand ISM heating

Does IRAC4 measure wellfull PAH emission?

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 7 / 20

Page 11: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Introduction: Polycyclic Aromatic Hydrocarbons Main interest (tracers, photo-electric heating)

Band ratio variations: resolved in MW clouds

Berne+12S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 8 / 20

Page 12: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

This study Main objectives

Objectives: PAH spectral diagnositics

Metalicities different from the MW

Smallest attainable beams

Largest coverage (environments; distance to stars, ...)

Spitzer/IRS spectral maps (LMC+SMC)

1/2 -1/5 solar metallicity

5−14µm (SL1,2,3)

∼4′′ resolution (∼1pc)

50-100 pc

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 9 / 20

Page 13: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

This study Main objectives

Objectives: PAH spectral diagnositics

Metalicities different from the MW

Smallest attainable beams

Largest coverage (environments; distance to stars, ...)

Spitzer/IRS spectral maps (LMC+SMC)

1/2 -1/5 solar metallicity

5−14µm (SL1,2,3)

∼4′′ resolution (∼1pc)

50-100 pc

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 9 / 20

Page 14: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

This study Main objectives

Objectives: PAH spectral diagnositics

Metalicities different from the MW

Smallest attainable beams

Largest coverage (environments; distance to stars, ...)

Spitzer/IRS spectral maps (LMC+SMC)

1/2 -1/5 solar metallicity

5−14µm (SL1,2,3)

∼4′′ resolution (∼1pc)

50-100 pc

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 9 / 20

Page 15: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

This study Presentation of regions

Large is still small

Inside yellow boxes full IFU from CUBISM (Smith+2007)

beam matched using Pereira-Santaella+2010

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 10 / 20

Page 16: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

This study Presentation of regions

Sometimes more favourable geometry

∼10 000 independent spectra

Fitted to obtain continuum, emission lines and feature strengths

Monte Carlo error analysis

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 11 / 20

Page 17: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Results and discussion Feature maps

Feature maps: SMC N66

PAH/mid-IR continuum

Strongly correlate with ionised gas(here S IV in orange contours)

• PAHs destroyed in the ionised gas

• mid-IR boosted due to hot dust

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 12 / 20

Page 18: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Results and discussion Feature maps

Feature maps: LMC N4

PAH strength ionisation

Some spatial dependence of ionisation state

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 13 / 20

Page 19: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Results and discussion Feature maps

Feature maps: LMC N11B

No discernible spatialtrends

Clumpy ISM al-lows radiation topenetrate the clouds

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 14 / 20

Page 20: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Results and discussion Trends

CC modes go together (ionisation dominates)

SMCLMC

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 15 / 20

Page 21: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Results and discussion Trends

Ionisation “follows” the mid-IR continuum colour

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 16 / 20

Page 22: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Results and discussion Differences between SMC and LMC

SMC is fainter

Probably related to metallicity

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 17 / 20

Page 23: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Results and discussion Differences between SMC and LMC

SMC is fainter and less ionised

See also Sandstrom+09S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 18 / 20

Page 24: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Results and discussion Resolution matters

Ionisation is correlated with PAH brightness

Low ionisation:

Generally faint

Near brighter,ionised l.o.s.

Removed by spatialaveraging

Median Σ7.7/11.2

3.3 → 5.31 → 8 pc linearresolution

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 19 / 20

Page 25: Polycyclic Aromatic Hydrocarbon from the Magellanic Clouds...Overview 1 Introduction: Polycyclic Aromatic Hydrocarbons Astronomical PAH bands Main interest (tracers, photo-electric

Conclusions

Take away points

Ionisation dominates/explains band-ratio variations

Both galaxies span entire range (×5) of ratios (ionisation degree)

SMC fainter in PAHs and exhibits more low ionisation

Little spatial patterns (clumpiness)

Radiation heating acts far (>50 pc) into the cold gas at thesemetalicities

Physical state of the cloud interfaces driven by clumpy ISM

Probably related to more translucent ISM at low-Z

S. Hony (Heidelberg University) LMC and SMC PAH diagnostics 11 Aug 2017 20 / 20


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