Testing the limits of AO: near diffraction limited astronomy in the red optical


M. Tecza


University of Oxford


In this presentation I explore selected science cases that benefit from the increased spatial resolution and sensitivity delivered by advanced, e.g. tomographic and multi conjugate, adaptive optics assisted observations at ELTs. In particular I will show that near diffraction-limited spatial resolution can be achieved at red optical wavelengths, even in the low Strehl ( 5%) regime. A typical AO-PSF has a diffraction limited core sumperimposed on the seeing halo. At 8m telescopes, the AO PSF for a 5% Strehl ratio would have a very low intensity diffraction limited core on top of the seeing halo, however, at an ELT because of the 4-5 times higher angular resolution, the diffraction limited core stands more prominently atop the shallow seeing halo as the halo flux per resolution element is smaller by a factor of 16-25. I focus on prominent example science cases that use the Calcium triplet and thus exploit this gain in spatial resolution in the red-optical: stellar populations in dense environments or crowded fields; and the case of intermediate mass black holes in nuclear and globular stellar clusters as well as (super-) massive black holes in galaxies. Additionally, kinematic studies of intermediate to high-redshift galaxies benefit from the increased spatial resolution in the red-optical. I will show that well measured AO-PSFs are a necessary ingredient for the successful analysis and interpretation of diffraction limited data

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