Application of a damped Locally Optimized Combination of Images method to the spectral characterization of faint companions using an Integral Field Spectrograph
Laurent Pueyo, Justin R. Crepp, Gautam Vasisht, Douglas Brenner, Ben R. Oppenheimer, Neil Zimmerman, Sasha Hinkley, Ian Parry, Charles Beichman, Lynne Hillenbra… 展开作者
Laurent Pueyo, Justin R. Crepp, Gautam Vasisht, Douglas Brenner, Ben R. Oppenheimer, Neil Zimmerman, Sasha Hinkley, Ian Parry, Charles Beichman, Lynne Hillenbrand, Lewis C. Roberts, Richard Dekany, Mike Shao, Rick Burruss, Antonin Bouchez, Jenny Roberts, Rémi Soummer
High-contrast imaging instruments are now being equipped with integral field spectrographs (IFS) to facilitate the detection and characterization of faint substellar companions. Algorithms currently envisioned to handle IFS data, such as the Locally Optimized Combination of Images (LOCI) algorithm, rely upon aggressive point-spread-function (PSF) subtraction, which is ideal for initially identifying companions but results in significantly biased photometry and spectroscopy due to unwanted mixing with residual starlight. This spectro-photometric issue is further complicated by the fact that algorithmic color response is a function of the companion's spectrum, making it difficult to calibrate the effects of the reduction without using iterations involving a series of injected synthetic companions. In this paper, we introduce a new PSF calibration method, which we call "damped LOCI", that seeks to alleviate these concerns. By modifying the cost function that determines the weighting coefficients used to construct PSF reference images, and also forcing those coefficients to be positive, it is possible to extract companion spectra with a precision that is set by calibration of the instrument response and transmission of the atmosphere, and not by post-processing. We demonstrate the utility of this approach using on-sky data obtained with the Project 1640 IFS at Palomar. Damped-LOCI does not require any iterations on the underlying spectral type of the companion, nor does it rely upon priors involving the chromatic and statistical properties of speckles. It is a general technique that can readily be applied to other current and planned instruments that employ IFS's.
我们选择了GYES这个名字，它是神话中的巨人之一，有一百条手臂，是盖亚和天王星的后代，我们的仪器研究是加拿大-法国-夏威夷望远镜的主要焦点。这种仪器可以为盖亚飞行任务提供极好的地面补充，并为关于AAT的HERMES项目提供北方补充。CFHT以提供稳定的主焦点环境而闻名，具有大视场，它承载了几种成像仪器，但从未承载过多光纤光谱仪。基于在GEPI获得的FLAMES-Giraffe和X-Shooter的经验，我们正在研究在直径为1度的视场内使用高复用摄谱仪（约500根光纤）的可行性。我们正在研究一种分辨率在15000到30000之间的仪器，它应该能提供精确的化学丰度，低至16等恒星和径向速度，精确到1公里/秒的微弱恒星。该研究由GEPI-Observatoire de Paris领导，牛津大学为定位器的研究做出了贡献。研究经费来自INSU CSAA和巴黎天文台。概念研究将于2010年10月1日前提交CFHT进行审查。
