Origin of the asymmetry of the wind driven halo observed in high-contrast images

The latest generation of high-contrast instruments dedicated to exoplanets and circumstellar disk imaging are equipped with extreme adaptive optics and coronagraphs to reach contrasts of up to 10−4 at a few tenths of arcseconds in the near-infrared. The resulting image shows faint features, only revealed with this combination, such as the wind driven halo. The wind driven halo is due to the lag between the adaptive optics correction and the turbulence speed over the telescope pupil. However, we observe an asymmetry of this wind driven halo that was not expected when the instrument was designed. In this letter, we describe and demonstrate the physical origin of this asymmetry and support our explanation by simulating the asymmetry with an end-to-end approach. From this work, we find that the observed asymmetry is explained by the interference between the AO-lag error and scintillation effects, mainly originating from the fast jet stream layer located at about 12 km in altitude. Now identified and interpreted, this effect can be taken into account for further design of high-contrast imaging simulators, next generation or upgrade of high-contrast instruments, predictive control algorithms for adaptive optics, or image post-processing techniques.

[1]  Tyson Hare,et al.  First closed-loop visible AO test results for the advanced adaptive secondary AO system for the Magellan Telescope: MagAO's performance and status , 2012, Other Conferences.

[2]  R. A. Silverman,et al.  Wave Propagation in a Turbulent Medium , 1961 .

[3]  G. Perrin,et al.  The Subaru Coronagraphic Extreme Adaptive Optics System: Enabling High-Contrast Imaging on Solar-System Scales , 2015, 1507.00017.

[4]  Olivier Guyon,et al.  Adaptive Optics Predictive Control with Empirical Orthogonal Functions (EOFs) , 2017, 1707.00570.

[5]  Kjetil Dohlen,et al.  SPHERE: a planet finder instrument for the VLT , 2006, Astronomical Telescopes + Instrumentation.

[6]  L. Jolissaint Synthetic Modeling of Astronomical Closed Loop Adaptive Optics , 2010, 1009.1581.

[7]  J. Vasquez,et al.  Statistics of turbulence profile at Cerro Tololo , 2003 .

[8]  T. Fusco,et al.  Fundamental limitations on Earth-like planet detection with extremely large telescopes , 2005 .

[9]  Carlos M. Correia Advanced control laws for the new generation of AO systems , 2018, Astronomical Telescopes + Instrumentation.

[10]  T. Fusco,et al.  Low wind effect on VLT/SPHERE: impact, mitigation strategy, and results , 2018, Astronomical Telescopes + Instrumentation.

[11]  T. Fusco,et al.  SPHERE eXtreme AO control scheme: final performance assessment and on sky validation of the first auto-tuned LQG based operational system , 2014, Astronomical Telescopes and Instrumentation.

[12]  J.-L. Beuzit,et al.  COMPASS: an efficient, scalable and versatile numerical platform for the development of ELT AO systems , 2014, Astronomical Telescopes and Instrumentation.

[13]  Bruce A. Macintosh,et al.  The Gemini Planet Imager: from science to design to construction , 2008, Astronomical Telescopes + Instrumentation.

[14]  C. Fabron,et al.  SPHERE: a planet finder instrument for the VLT , 2006, Astronomical Telescopes + Instrumentation.

[15]  L. Mugnier,et al.  The GJ 504 system revisited , 2018, Astronomy & Astrophysics.

[16]  Armando Riccardi,et al.  MAGELLAN ADAPTIVE OPTICS FIRST-LIGHT OBSERVATIONS OF THE EXOPLANET β PIC b. I. DIRECT IMAGING IN THE FAR-RED OPTICAL WITH MagAO+VisAO AND IN THE NEAR-IR WITH NICI, , 2014, 1403.0560.

[17]  J. Osborn,et al.  Atmospheric turbulence forecasting with a general circulation model for Cerro Paranal , 2018, Monthly Notices of the Royal Astronomical Society.

[18]  Jason J. Wang,et al.  CONSTRAINTS ON THE ARCHITECTURE OF THE HD 95086 PLANETARY SYSTEM WITH THE GEMINI PLANET IMAGER , 2016, 1604.05139.

[19]  A. Vigan,et al.  Spectral and atmospheric characterization of 51 Eridani b using VLT/SPHERE , 2017, 1704.02987.

[20]  Dimitri Mawet,et al.  Improving Signal to Noise in the Direct Imaging of Exoplanets and Circumstellar Disks , 2015 .