Observations of AGN with MIDI or „How to cope with faint targets with MIDI“ EuroSummer School Observation and data reduction with the VLTI Konrad R. W.

Observations of AGN with MIDIor

„How to cope with faint targets with MIDI“

EuroSummer School

Observation and data reduction with the VLTI

Konrad R. W. Tristram

MPIA Heidelberg

13.06.2006 Konrad R. Tristram Page 2

Contents

• Introduction:AGN, unified scheme, SED, key questions, why MIDI?

• Observations:acquisition, tracking and photometry for weak targets

• Data reduction:EWS

• Results for observed sources:NGC1068, Circinus, Centaurus A, weaker sources

• Prospects and advice

13.06.2006 Konrad R. Tristram Page 3

Contents

• Introduction:AGN, unified scheme, SED, key questions, why MIDI?

• Observations:acquisition, tracking and photometry for weak targets

• Data reduction:EWS

• Results for observed sources:NGC1068, Circinus, Centaurus A, weaker sources

• Prospects and advice

13.06.2006 Konrad R. Tristram Page 4

Introduction: What are AGN?

• AGN (Active Galactic Nucleus): supermassive black hole (M > 106 M ) at the centre of a galaxy actively accreting

• Large range of energetic phenomena:– X-ray emission– Ionisation cones– broad and narrow line regions– jets– ….

Urry and Padovani, 1995

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Introduction: The Unified scheme

• Unified AGN model:Geometrical effects lead to different manifestations (e.g. Seyfert 1 & 2)

Broad LineRegion

AccretionDisk

ObscuringTorus

Ionisation Cone

Black Hole

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Introduction: The SED of AGN

9 10 11 12 13 14 15 16 17 18 19

log(ν) in Hz

41

42

43

44

45

46

47

log(

νLν)

in e

rg/s

1.2 keV120 eV

10 nm100 nm

1 µm10 µm

100 µm1 mm

1 cm1 dm

blue bump

IR bump

Ly α line

soft excess

Elvis et al., 1994

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Introduction: Key questions

• Key questions:– What is history and evolution of AGN?– How is the accretion energy released?– What is the interplay between black hole and its host?– Is the picture of the unified scheme true?

• Search for direct evidence for dust torus– Observations in the MIR– Sufficient spatial resolution

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Introduction: Nearby AGN

Name Type Distance

[Mpc]

1 pc

[mas]

Flux

[Jy]

NGC 1068 Sy 2 17 12 18.0

Circinus Sy 2 4 52 9.7

NGC 4151 Sy 1.5 14 15 1.2

NGC 5128 Sy 2 4 52 1.2

NGC 5506 Sy 2 28 7 0.9

NGC 1365 Sy 1.8 25 8 0.6

MCG -05-23-016 Sy 2 38 5 0.6

Mrk 1239 Sy 1 92 2 0.6

NGC 3783 Sy 1 45 5 0.6

NGC 3281 Sy 2 50 4 0.6

IRS 0518-25 Sy 2 200 1 0.5

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Introduction: Why MIDI?

• Need MIR instruments with highest resolution!

Find this only at the VLTI: MIDI• Goal for MIDI:

– Resolve the putative dust torus directly for nearby active galaxies!

VLT with the Residencia

February 2005

13.06.2006 Konrad R. Tristram Page 10

Contents

• Introduction:AGN, unified scheme, SED, key questions, why MIDI?

• Observations:acquisition, tracking and photometry for weak targets

• Data reduction:EWS

• Results for observed sources:NGC1068, Circinus, Centaurus A, weaker sources

• Prospects and advice

13.06.2006 Konrad R. Tristram Page 11

Observations: Target list

List of all AGN observed to date:

Name Flux (10µm) Time In charge

NGC 1068 (M77) 13 Jy SDT / OT Raban

Circinus 5 Jy GTO Tristram

NGC 5128 (Centaurus A) 0.6 Jy GTO Meisenheimer

NGC 3783 0.5 Jy OT Beckert

Mrk 1239 0.4 Jy GTO Cotton

MCG -05-23-016 0.3 Jy GTO Cotton

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Observations: Acquisition

• Example for a bright calibrator:

HD120404• First iteration

Flux: 10 Jy

Filter: N8.7

DIT = 0.0040

NDIT = 1000

Beam A Beam B

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Observations: Acquisition

• Example for a bright calibrator:

HD120404• Second iteration

Flux: ~10 Jy

Filter: N8.7

DIT = 0.0040

NDIT = 1000

Beam A Beam B

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Observations: Acquisition

• Example for a bright calibrator:

HD120404• Third iteration

Flux: ~10 Jy

Filter: N8.7

DIT = 0.0040

NDIT = 1000

Beam A Beam B

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Observations: Acquisition

• Example for a ‘bright’ AGN:

Circinus galaxy• First iteration

Flux: 5 Jy

Filter: SiC

DIT = 0.0017

NDIT = 1000

Beam A Beam B

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Observations: Acquisition

• Example for a ‘bright’ AGN:

Circinus galaxy• Second iteration

Flux: 5 Jy

Filter: SiC

DIT = 0.0017

NDIT = 2000

Beam A Beam B

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Observations: Acquisition

• Example for a ‘bright’ AGN:

Circinus galaxy• Third iteration

Flux: 5 Jy

Filter: SiC

DIT = 0.0017

NDIT = 2000

Beam A Beam B

13.06.2006 Konrad R. Tristram Page 18

Observations: Acquisition

• Example for a faint AGN:

Mrk1239• First iteration

Flux: 0.6 Jy

Filter: SiC

DIT = 0.0017

NDIT = 8000

Beam A Beam B

13.06.2006 Konrad R. Tristram Page 19

Observations: Acquisition

• Example for a faint AGN:

Mrk1239• Second iteration

Flux: 0.6 Jy

Filter: SiC

DIT = 0.0017

NDIT = 8000

Beam A Beam B

13.06.2006 Konrad R. Tristram Page 20

Observations: Acquisition

• Example for a faint AGN:

Mrk1239• Third iteration

Flux: 0.6 Jy

Filter: SiC

DIT = 0.0017

NDIT = 12000

Beam A Beam B

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Observations: Fringe search

Fringe-Search on Mrk 1239

Fringe search and tracking then seems easy!

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Observations: Fringe tracking

Circinus

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Observations: Fringe tracking

MCG -05-23-016

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Observations: Photometry

• HD 120404• Beam A• without additional

sky subtraction

prism

DIT = 0.012

NDIT = 1500

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Observations: Photometry

• HD 120404• Beam A• with additional

sky subtraction

prism

DIT = 0.012

NDIT = 1500

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Observations: Photometry

• Centaurus A• Beam A• without additional

sky subtraction

prism

DIT = 0.018

NDIT = 10000

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Observations: Photometry

• Centaurus A• Beam A• with additional

sky subtraction

prism

DIT = 0.018

NDIT = 10000

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Observations: Photometry

• Centaurus A• Beam B• without additional

sky subtraction

prism

DIT = 0.018

NDIT = 10000

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Observations: Photometry

• Centaurus A• Beam B• with special sky

subtraction

prism

DIT = 0.018

NDIT = 10000

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Contents

• Introduction:AGN, unified scheme, SED, key questions, why MIDI?

• Observations:acquisition, tracking and photometry for weak targets

• Data reduction:EWS

• Results for observed sources:NGC1068, Circinus, Centaurus A, weaker sources

• Prospects and advice

13.06.2006 Konrad R. Tristram Page 31

Data reduction

• What does EWS do?1. data compression

2. background removal

3. instrumental OPD demodulation

4. atmospheric delay removal

5. determination of the differential phase

6. coherent integration

visibility and differential phase

• How to run EWS?IDL> midipipe, tag, files

IDL> midicalibrate, scitag, caltag

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Data reduction

• Almost exclusively with EWS

• Usage of optional settings(smooth, gsmooth, /dave)

• Calibrations problems:– usage of geometric or arithmetic photometry– Non detections midisearch

13.06.2006 Konrad R. Tristram Page 33

Contents

• Introduction:AGN, unified scheme, SED, key questions, why MIDI?

• Observations:acquisition, tracking and photometry for weak targets

• Data reduction:EWS

• Results for observed sources:NGC1068, Circinus, Centaurus A, weaker sources

• Prospects and advice

13.06.2006 Konrad R. Tristram Page 34

NGC 1068: first results

Jaffe et al. 2004

• Two baseline orientations

• Modelled by two elliptical Gaussians:– Hot and cold component– Different silicate absorption

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NGC 1068: first results

Jaffe et al. 2004

Confirmation of the unified scheme!

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NGC 1068: new observations

• Grism observations

• Open time• 2005• 13 independent

visibility points -150 -100 -50 50 100 150

-150

-100

-50

50

100

150

Period 76, 2005

u in m

v in m

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Circinus: properties

• Spiral galaxy SA(s)b, i = 65°

• Seyfert type 2

• 4 × 106 M nucleus

• Distance ~4 Mpc

→ 50 mas ~ 1 pc

2MASS J, H, Ks colour mosaic

13.06.2006 Konrad R. Tristram Page 38

Circinus: UV plane

u in m

-80 -60 -40 -20 20 40 60 80

-80

-60

-40

-20

20

40

60

80v in m

Period 72, 04-02 (U3-U2)Period 73, 04-06 (U3-U2)Period 74, 05-02 (U3-U4)Period 75, 05-05 (U2-U3)Period 77, 06-05 (U2-U3)

U2-U4• GTO observations from P72 to P77

• 15 independent visibility points (several ‘double’)

• some of these rather “dodgy”

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Circinus: Correlated flux

8 9 10 11 12 13Wavelength λ in µm

0.0

0.5

1.0

1.5

Flu

x in

Jy

Calibrated Correlated Flux

ozon

e

Circinus, observed: 2005-02-28

PA= 44°, BL=49.4mPA= 54°, BL=51.1mPA= 57°, BL=51.7mPA= 88°, BL=58.2mPA=120°, BL=62.0mPA=131°, BL=62.4m

N

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Circinus: Results

Known geometry

1’’~ 20 pc

O[III]

Tristram et al. 2006

Expected torus configuration

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Circinus: Results

Measured geometry at 8.5 µm

Tristram et al. 2006

-50-2550

RA in mas

-50

-25

25

50 DEC in mas

0.46

pc

0.70 pc

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Circinus: Results

Measured geometry at 13 µm

Tristram et al. 2006

-50-252550

RA in mas

-50

-25

50 DEC in mas

0.70

pc

1.1 pc

Confirmation of the unified scheme!

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Centaurus A: properties

• Elliptical galaxy

• dust lane edge-on

• Seyfert type 2

• FR 1 radio galaxy

• 6 × 107 M nucl.

• Distance ~4 Mpc

→ 50 mas ~ 1 pc

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Centaurus A: UV plane

-80 -60 -40 -20 20 40 60 80

-80

-60

-40

-20

20

40

60

80 Period 74, 05-02 (U3-U4)Period 75, 05-05 (U2-U3)

u in m

v in m• GTO observations in P74 and P75

• 4 independent visibility points

• problems with photometry

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Centaurus A: visibilities

8 9 10 11 12 13

Wavelength in µm

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Vis

ibili

ty

PA= 96°, BL=58.0mPA=119°, BL=62.0m

Calibrated VisibilityCentaurus A, observed: 2005-02-28

ozon

eNo dust torus? Synchrotron emission?

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Faint AGN

13.06.2006 Konrad R. Tristram Page 47

Faint AGN

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Faint AGN

• Observation time for faint targets:MCG -5-23-016 ― 57 min

Mrk 1239 ― 53 min

Mrk 1239 ― 50 min

1 hour for faint target + ½ for calibrator.

• No problem tracking 200 mJy correlated flux.

• High visibility on sources

13.06.2006 Konrad R. Tristram Page 50

Contents

• Introduction:AGN, unified scheme, SED, key questions, why MIDI?

• Observations:acquisition, tracking and photometry for weak targets

• Data reduction:EWS

• Results for observed sources:NGC1068, Circinus, Centaurus A, weaker sources

• Prospects and advice

13.06.2006 Konrad R. Tristram Page 51

Prospects

• Long baselines for unresolved targets

• Shorter baselines for highly resolved targets

try ATs (?)

• Extension of sample (need FINITO)

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Conclusions

• Only limited sample of observable AGN

• “Inconclusive” results

• To study more objects an increase of sensitivity needed