The extinction and dust-to-gas structure of the planetary nebula NGC 7009 observed with MUSE J. R. Walsh, A. Monreal-Ibero, M. J. Barlow, T. Ueta, R. Wesson and A. A. Zijlstra A&A, 588 (2016) A106 Published online: 25 March 2016 DOI: 10.1051/0004-6361/201527988