SPHERE / ZIMPOL high resolution polarimetric imager. I. System overview, PSF parameters, coronagraphy, and polarimetry
Abstract
We describe the Zurich Imaging Polarimeter (ZIMPOL), the visual focal plane subsystem of the SPHERE "VLT planet finder", which pushes the limits of current AO systems to shorter wavelengths, higher spatial resolution, and much improved polarimetric performance. We provide new benchmarks for the performance of high contrast instruments, in particular for polarimetric differential imaging. We have analyzed SPHERE/ZIMPOL point spread functions and measure the peak surface brightness, the encircled energy, and the full width half maximum (FWHM) for different wavelengths, atmospheric conditions, star brightness, and instrument modes. Coronagraphic images are described and analized and the performance for different coronagraphs is compared with tests for the binary alpha Hyi with a separation of 92 mas and a contrast of 6 mag. For the polarimetric mode we made the instrument calibrations using zero polarization and high polarization standard stars and here we give a recipe for the absolute calibration of polarimetric data. The data show a small <1 mas but disturbing differential polarimetric beam shifts, which can be explained as Goos-H\"ahnchen shifts from the inclined mirrors, and we discuss how to correct this effect. The polarimetric sensitivity is investigated with non-coronagraphic and deep, coronagraphic observations of the dust scattering around the symbiotic Mira variable R Aqr. SPHERE/ZIMPOL achieves imaging performances in the visual range with unprecedented characteristics, in particular very high spatial resolution and very high polarimetric contrast. This instrument opens up many new research opportunities for the detailed investigation of circumstellar dust, in scattered and therefore polarized light, for the investigation of faint companions, and for the mapping of circumstellar Halpha emission.
Keywords
Cite
@article{arxiv.1808.05008,
title = {SPHERE / ZIMPOL high resolution polarimetric imager. I. System overview, PSF parameters, coronagraphy, and polarimetry},
author = {H. M. Schmid and A. Bazzon and R. Roelfsema and D. Mouillet and J. Milli and F. Menard and D. Gisler and S. Hunziker and J. Pragt and C. Dominik and A. Boccaletti and C. Ginski and L. Abe and S. Antoniucci and H. Avenhaus and A. Baruffolo and P. Baudoz and J. L. Beuzit and M. Carbillet and G. Chauvin and R. Claudi and A. Costille and J. B. Daban and M. de Haan and S. Desidera and K. Dohlen and M. Downing and E. Elswijk and N. Engler and M. Feldt and T. Fusco and J. H. Girard and R. Gratton and H. Hanenburg and Th. Henning and N. Hubin and F. Joos and M. Kasper and C. U. Keller and M. Langlois and E. Lagadec and P. Martinez and E. Mulder and A. Pavlov and L. Podio and P. Puget and S. Quanz and F. Rigal and B. Salasnich and J. F. Sauvage and M. Schuil and R. Siebenmorgen and E. Sissa and F. Snik and M. Suarez and Ch. Thalmann and M. Turatto and S. Udry and A. van Duin and R. van Holstein and A. Vigan and F. Wildi},
journal= {arXiv preprint arXiv:1808.05008},
year = {2018}
}
Comments
38 pages with 33 figurs, accepted for publication in Astron. Astrophys