observations of agn with midi or „how to cope with faint targets with midi“ eurosummer school...
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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
13.06.2006 Konrad R. Tristram Page 5
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
13.06.2006 Konrad R. Tristram Page 6
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
13.06.2006 Konrad R. Tristram Page 12
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
13.06.2006 Konrad R. Tristram Page 14
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
13.06.2006 Konrad R. Tristram Page 15
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
13.06.2006 Konrad R. Tristram Page 16
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
13.06.2006 Konrad R. Tristram Page 17
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
13.06.2006 Konrad R. Tristram Page 21
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
13.06.2006 Konrad R. Tristram Page 25
Observations: Photometry
• HD 120404• Beam A• with additional
sky subtraction
prism
DIT = 0.012
NDIT = 1500
13.06.2006 Konrad R. Tristram Page 26
Observations: Photometry
• Centaurus A• Beam A• without additional
sky subtraction
prism
DIT = 0.018
NDIT = 10000
13.06.2006 Konrad R. Tristram Page 27
Observations: Photometry
• Centaurus A• Beam A• with additional
sky subtraction
prism
DIT = 0.018
NDIT = 10000
13.06.2006 Konrad R. Tristram Page 28
Observations: Photometry
• Centaurus A• Beam B• without additional
sky subtraction
prism
DIT = 0.018
NDIT = 10000
13.06.2006 Konrad R. Tristram Page 29
Observations: Photometry
• Centaurus A• Beam B• with special sky
subtraction
prism
DIT = 0.018
NDIT = 10000
13.06.2006 Konrad R. Tristram Page 30
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!
13.06.2006 Konrad R. Tristram Page 36
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
13.06.2006 Konrad R. Tristram Page 37
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”
13.06.2006 Konrad R. Tristram Page 39
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
13.06.2006 Konrad R. Tristram Page 40
Circinus: Results
Known geometry
1’’~ 20 pc
O[III]
Tristram et al. 2006
Expected torus configuration
13.06.2006 Konrad R. Tristram Page 41
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
13.06.2006 Konrad R. Tristram Page 42
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!
13.06.2006 Konrad R. Tristram Page 43
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
13.06.2006 Konrad R. Tristram Page 44
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
13.06.2006 Konrad R. Tristram Page 45
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?
13.06.2006 Konrad R. Tristram Page 46
Faint AGN
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Faint AGN
13.06.2006 Konrad R. Tristram Page 49
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)
13.06.2006 Konrad R. Tristram Page 52
Conclusions
• Only limited sample of observable AGN
• “Inconclusive” results
• To study more objects an increase of sensitivity needed