A New High Contrast Imaging Program at Palomar Observatory

作者：Hinkley Sasha^*; Oppenheimer Ben R; Zimmerman Neil; Brenner Douglas; Parry Ian R; Crepp Justin R; Vasisht Gautam; Ligon Edgar; King David; Soummer Remi; Sivaramakrishnan Anand; Beichman Charles; Shao Michael; Roberts Lewis C Jr; Bouchez Antonin; Dekany Richard; Pueyo Laurent; Roberts Jennifer E; Lockhart Thomas; Zhai Chengxing; Shelton Chris; Burruss Rick

来源：Publications of the Astronomical Society of the Pacific, 2011, 123(899): 74-86.

DOI：10.1086/658163

We describe a new instrument that forms the core of a long-term high contrast imaging program at the 200 inch (5 m) Hale Telescope at Palomar Observatory. The primary scientific thrust is to obtain images and low-resolution spectroscopy of brown dwarfs and young exoplanets of several Jupiter masses in the vicinity of stars within 50 pc of the Sun. The instrument is a microlens-based integral field spectrograph integrated with a diffraction-limited, apodized-pupil Lyot coronagraph. The entire combination is mounted behind the Palomar adaptive optics (AO) system. The spectrograph obtains imaging in 23 channels across the J and H bands (1.06-1.78 mu m). The image plane of our spectrograph is subdivided by a 200 x 200 element microlens array with a plate scale of 19.2 mas per microlens, critically sampling the diffraction-limited point-spread function at 1.06 mu m. In addition to obtaining spectra, this wavelength resolution allows suppression of the chromatically dependent speckle noise, which we describe. In addition, we have recently installed a novel internal wave front calibration system that will provide continuous updates to the AO system every 0.5-1.0 minutes by sensing the wave front within the coronagraph. The Palomar AO system is undergoing an upgrade to a much higher order AO system (PALM-3000): a 3388-actuator tweeter deformable mirror working together with the existing 241-actuator mirror. This system, the highest-resolution AO corrector of its kind, will allow correction with subapertures as small as 8.1 cm at the telescope pupil using natural guide stars. The coronagraph alone has achieved an initial dynamic range in the H band of 2 x 10(-4) at 1 '', without speckle noise suppression. We demonstrate that spectral speckle suppression provides a factor of 10-20 improvement over this, bringing our current contrast at 1 '' to similar to 2 x 10(-5). This system is the first of a new generation of apodized-pupil coronagraphs combined with high-order adaptive optics and integral field spectrographs (e. g., GPI, SPHERE, HiCIAO), and we anticipate that this instrument will make a lasting contribution to high-contrast imaging in the Northern Hemisphere for years.

• 出版日期2011-1