high resolution imaging of dust disks structures around herbig ae stars with visir
DESCRIPTION
20-23 March 2006 - VIRA - Paris. High Resolution Imaging of dust disks structures around Herbig Ae stars with VISIR. C.Doucet , P-O Lagage, E. Pantin (CEA Saclay SAp) E. Habart (IAS, Orsay) C. Pinte, G. Duchêne, F. Ménard (LAOG, Grenoble). - PowerPoint PPT PresentationTRANSCRIPT
High Resolution Imaging of dust disks structures around Herbig
Ae stars with VISIR
• C.Doucet, P-O Lagage, E. Pantin (CEA Saclay SAp)• E. Habart (IAS, Orsay)• C. Pinte, G. Duchêne, F. Ménard (LAOG, Grenoble)
20-23 March 2006 - VIRA - Paris
VISIRVLT Imager and Spectrometer
for the InfraRed
• Located at the Cassegrain focus of UT3 of the VLT.
• 2 bands IR of obervations:– N Band : 8 - 13 μm – Q Band : 17 - 24 μm
• Spatial resolution: 15 times the ones of ISOCAM or Spitzer (0.075 ’’/pixel)
• Spectral resolution:– 350 - 25000 at 10 μm – 1200 - 12500 at 20 μm.
0.8’’ seeing
New imaging mode: BURST mode
• Seeing not as good as expected → lost spatial resolution
51
seeing
Seeing of 0.8’’ in the visible →Seeing of 0.4’’ in mid-IR→movement of 5 pixels.
→ Limit the effect of TURBULENCE by freezing the atmosphere with very
short exposure time :BURST MODE
Speckle in mid-IR0r
D
wavelength SEEING 0.5’’ SEEING 1’’
(µm) R0 (m) T0(ms) R0 (m) T0(ms)
2 1.05 52-210 0.52 28-100
10 7.28 360-1450 3.64 200-700
20 16.7 835-3340 8.36 400-1600
Wind speed between 5 and 20 m/s
250702
0
speckleNRD In Near-IR
42
0
speckleNRD In Mid-IR
→ Stable atmosphere
→ One principal speckle
Texposition ~ 16-50 (ms) ≤ T0(mid-IR)
D~R0
BURST: turbulence effect
Sensibility ↔ 7 mJy/10σ/1hSensibility ↔ 14 mJy/10σ/1h
Reference star HD85503 at 11.3 µm (January 2005)
Shift and add by centroid
Shift and add by autocorrelation
Shift and add by maximum
FWHMx (mas) 424 302 386
FWHMy (mas) 547 288 523
ellipticity 1.29 0.95 1.36
Strehl ratio 0.328 0.760 0.368
Image quality/shift and add in mid-IR
HD85503 at 11.3 µm (January 2005, seeing of 0.75’’ in the visible)HD62902 at 11.3 µm, Seeing of 1.2’’ in the visible Shift and add by centroid
Shift and add by autocorrelation
Shift and add by maximum
FWHMx (mas) 358 300 437
FWHMy (mas) 552 300 542
ellipticity 1.54 1. 1.24
Strehl ratio 0.27 0.80 0.67
Limit of the method
• For bright sources (5 Jy in N band)
• Method shift and add valid for a seeing ≤ 1.3’’ in the visible
Otherwise
→ speckle interferometry
Effect of a bad seeing (1.5 ’’) on the source
A star noticeable: HD97048a Herbig A star at 180 pc in the Chameleon cloud
Doucet et al. 2006,submitted A&A
PAH stochastically heated by UV radiation from the star Could allow to see the disk much further from the star: new TRACERS of the disk geometry
Conclusions/Perspectives
HD169142 in mode normal (PAH1, 8.6 µm)0.65 ’’ seeing, exposure time: 316 sHD169142 in BURST mode (PAH1, 8.6 µm)0.55’’ seeing, exposure time: 118 s
• TRUST in BURST mode
• planned to be a technical mode
• Work with ESO to open thismode to community
PSF substracted
Sometimes, elongated source
Modelisation of a flared disk
Model of disk heated by irradiation from the central star, in hydrostatic equilibrium in the vertical direction, with dust and gaz well mixed, with transiently heated small grains and PAHs addition to large grains in thermal equilibrium (1-D radiation transfert code, Habart et al. 2004).