1. Milli-arcsecond Imaging of the Inner Regions of Protoplanetary Disks Stéphanie Renard In collaboration with F. Malbet, E. Thiébaut, J.-P. Berger & M. Benisty « Planet Formation and Evolution: The Solar System and Extrasolar Planets » Tübingen, 2 March 2009

2. Stéphanie Renard Tübingen Conference 2 March 2009 2 Outline  Astrophysical context: Protoplanetary disks around young stellar objects (YSOs)  Optical/IR interferometry: Technique & Observables Image reconstruction  Application on real data of YSOs: HD 45677 MWC 275  Conclusions & Perspectives

3. Stéphanie Renard Tübingen Conference 2 March 2009 3 Astrophysical context: physical conditions in the close environment of young stellar objects  Characteristics & Phenomena Stars from 4000 to 10000K Accretion disk (Keplerian or not): gas + dust Strong outflowing winds Companions Magnetospheric accretion Protoplanets  Physical conditions of the dust inner disk: Radius from 0.1 to 10 AU Temperature from 150 to 4000K Velocity from 10 to a few 100 km/s  Instrument requirements: 1 µm ≤ ≤ 10 µm Spatial resolution from 0.5 to 70 mas (at 150 pc ; Taurus system)  Optical/IR Interferometry Dust Wind Accretion disk Magnetosphere Gas Planet

4. Stéphanie Renard Tübingen Conference 2 March 2009 4 Optical/IR interferometry: observables  Concept: Coherent recombination of the beams from several telescopes  High angular resolution  Observables: fringe pattern Squared visibilities V (size of the object) Loss of phase φ because of the atmospheric turbulence  Closure phases (asymmetry of the object)  Analysis of the data: Model fitting Image reconstruction  Model independent VLTI, ESO Paranal, Chile I V φ ddm k i j φ ij φ jk φ ki CP ijk = φ ij + φ jk + φ ki

5. Stéphanie Renard Tübingen Conference 2 March 2009 5 Optical/IR interferometry: image reconstruction  Image formation  Goal of image reconstruction: retrieve I true  Ill-conditioned problem (infinity of solutions which fit the data in the error bars)  additional constraints  Method: Maximum a posteriori  Use of MIRA algorithm of Eric Thiébaut (Thiébaut et al. 2008, Proc. SPIE 7013, 70131I) Likelihood term: compatibility of the solution with the data Prior penalty: Additional constraints Gaussian statistic: ² Weight factor  Fourier transform  Positivity of the solution  Normalization  Smoothness regularization

6. Stéphanie Renard Tübingen Conference 2 March 2009 6 1 st YSO: HD 45677 – 1. Description  Herbig Be type (?)  Monnier et al. 2006 “First closure phase survey of Herbig Ae/Be stars”  parametric imaging  highly skewed dust ring (i.e. the brightest part of a disk in the NIR infrared)  Data used for the image reconstruction: Monnier et al. 2006 IOTA interferometer H Band Monnier et al. 2006

7. Stéphanie Renard Tübingen Conference 2 March 2009 7 1 st YSO: HD 45677 – 2. MIRA results  Reconstructed image (reduced ²~2): central star + clumpy features on an ellipse (?!)  Prior: smoothness (independent of the chosen prior)

8. Stéphanie Renard Tübingen Conference 2 March 2009 8 1 st YSO: HD 45677 – 3. Analysis  Method: Choose a model (e.g. star + Gaussian ring) Compute the Fourier Transform of the model and determine the squared visibilities & closure phases Take the observables exactly at the same u,v points than the real data Keep the same error bars than the real data Reconstruct a new image  Try to find a model which gives a reconstructed image as close as possible to the one from the real data  1st model: star + Gaussian ring Problem: symmetric model  closure phases = 0 !

9. Stéphanie Renard Tübingen Conference 2 March 2009 9 1 st YSO: HD 45677 – 3. Analysis  2 nd model: star + skewed Gaussian ring Problem: features only on a side of the star  3rd model: star + off-centered Gaussian ring

10. Stéphanie Renard Tübingen Conference 2 March 2009 10 1 st YSO: HD 45677 – 4. Conclusions  Best model according to the image reconstruction: Star + off-centered Gaussian ring Physical interpretation: flared disk Radius9 ± 0.14 mas Inclination35 ± 2 ° Position angle78 ± 3.5 ° Shift x0.5 ± 0.2 mas Shift y-2 ± 0.1 mas  Need data at longer baselines in order to distinguish between different models  Image reconstruction: The features seem to be an intern problem: why and how avoid them ? (work in progress) New approach: determination of new models by the image reconstruction results Monnier et al. 2006

11. Stéphanie Renard Tübingen Conference 2 March 2009 11 2 nd YSO: MWC 275 – 1. Description  Herbig Ae star  Data used for the image reconstruction: Benisty et al., in prep VLTI/AMBER interferometer spectral dispersion over H and K band  Devine and Grady et al. 2000 “A Ly bright jet from a Herbig Ae Star”:  Collimated bipolar outflow (HH409) perpendicular to the disk

12. Stéphanie Renard Tübingen Conference 2 March 2009 12 2 nd YSO: MWC 275 – 2. MIRA results Consistent with previous work and jet direction K Band H Band

13. Stéphanie Renard Tübingen Conference 2 March 2009 13 Conclusions & Perspectives  First images on real interferometric data of complex YSOs  New approach: determination of new models by the image reconstruction results  Work on one of the issues of YSOs: the disk shape  Image reconstruction in optical interferometry: a new technique in progress Difficulties (in contrast to image reconstruction in radio):  Sparse (u,v) coverage  Lack of phase information  systematic tests on the MIRA algorithm Reconstructed images independent of the added constraints  robust results  First steps towards the 1mas-imaging with the new imager instruments at VLTI

14. Stéphanie Renard Tübingen Conference 2 March 2009 14 Thank you for your attention  Another astrophysical object: The Mira Star T Lep Le Bouquin et al. 2009, A&A Letter “Pre-maximum spectro-imaging of the Mira star T Lep with AMBER/VLTI”