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arXiv 1409.7631astro-ph.IMastro-ph.CO
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欧洲极大望远镜多目标spectroscopy宇宙学深场中的宽场自适应光学性能

Wide-field adaptive optics performance in cosmological deep fields for multi-object spectroscopy with the European Extremely Large Telescope

Alastair Basden, Chris Evans, Tim Morris

摘要:

为了在良好的天空覆盖范围内运行,将需要在即将到来的欧洲极大望远镜上安装一台多物体摄谱仪。许多有趣的深宇宙学领域被故意选择为没有明亮的前景恒星,因此对自适应光学(AO)系统具有潜在的挑战性。在这里,我们调查多对象AO性能使用子字段内随机选择的大天文台起源深调查(GOODS)-S字段,这是最坏的情况下广泛用于高红移星系的研究五个深场。我们的AO系统模型是基于建议的MOSAIC仪器,但我们的研究结果同样适用于任何计划中的超大望远镜的多目标光谱计划。潜在的引导星在这些子领域内的识别和用于模拟AO校正。在75~mas范围内,我们获得了25- 35%的能量,这对于探测高红移星系的sub-kpc尺度是足够的。我们还研究了探测器读出噪声对AO系统性能的影响,并考虑了自然导星用于高阶和倾斜仅AO校正的情况。我们还考虑了性能如何与能量盒大小成比例。总之,预期的AO性能对于MOSAIC类仪器来说是足够的,即使在以缺乏明亮前景恒星为特征的深视场中也是如此。

英文摘要:

A multi-object spectrograph on the forthcoming European Extremely Large Telescope will be required to operate with good sky coverage. Many of the interesting deep cosmological fields were deliberately chosen to be free of bright foreground stars, and therefore are potentially challenging for adaptive optics (AO) systems. Here we investigate multi-object AO performance using sub-fields chosen at random from within the Great Observatories Origins Deep Survey (GOODS)-S field, which is the worst case scenario for five deep fields used extensively in studies of high-redshift galaxies. Our AO system model is based on that of the proposed MOSAIC instrument but our findings are equally applicable to plans for multi-object spectroscopy on any of the planned Extremely Large Telescopes. Potential guide stars within these sub-fields are identified and used for simulations of AO correction. We achieve ensquared energies within 75~mas of between 25-35\% depending on the sub-field, which is sufficient to probe sub-kpc scales in high-redshift galaxies. We also investigate the effect of detector readout noise on AO system performance, and consider cases where natural guide stars are used for both high-order and tip-tilt-only AO correction. We also consider how performance scales with ensquared energy box size. In summary, the expected AO performance is sufficient for a MOSAIC-like instrument, even within deep fields characterised by a lack of bright foreground stars.

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