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

Abstract

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Monte Carlo modelling of multi-object adaptive optics performance on the European Extremely Large Telescope

“…However, a study of performance trends is possible, and we find that several of the performance trends that we present here (e.g. performance as a function of asterism diameter, with scaling of NGS flux, number of LGS, and LGS pixel scale) are similar to those in previous studies using Monte-Carlo end-to-end AO simulation (Basden 2015b;Le Louarn et al 2012;Tallon et al 2011;Foppiani et al 2010;Basden, Evans & Morris 2014;Basden et al 2013). We note that Monte-Carlo models are pessimistic when compared to analytical model results (Neichel, Fusco & Conan 2008).…”

“…Fig. 9 shows these results for one NGS asterism (asterism 0), and these can be compared with Basden, Evans & Morris (2014). This figure also demonstrates how AO performance can be improved by reducing the WFS frame rate used with low-flux NGSs.…”

“…In a previous study (Basden, Evans & Morris 2014), we explored many different NGS asterisms available within a cosmological field (which by definition are relatively free of suitable bright guide stars), and the effect that these have on AO performance. Here, we base this study on the same set of NGSs, as shown in Fig.…”

“…Unless otherwise stated, we use asterism 0 as the default case, as this provides a close-to-median performance. Conversion from guide star magnitude to detected WFS flux level is given by Basden, Evans & Morris (2014) The key AO performance metric that we present here is ensquared energy within a 150 mas box diameter at Hband (1650 nm wavelength). The reason for this is that for a wide-field MOAO system with limited guide star numbers (both NGS and LGS), Strehl ratio is typically low, and ensquared energy is therefore more sensitive to changes in AO performance as parameter space is explored.…”

“…We have previously explored MOAO performance with a number of different NGS asterisms (Basden, Evans & Morris 2014). Here, for each of these asterisms, we investigate performance as a function of number of LGSs used, as shown in Fig.…”