M Libralato, D Erkal, A Amara, L. R Bedin, M Griggio, R. C Nichol, D Massari, J Anderson, J. -C Cuillandre, A. M. N Ferguson, A Lançon, S. S Larsen, M Schirmer, F Annibali, E Balbinot, E Dalessandro, P. B Kuzma, T Saifollahi, R Nakajima, G. Verdoes Kleijn, G Battaglia, M Kümmel, M Correnti, B Altieri, S Andreon, C Baccigalupi, M Baldi, A Balestra, S Bardelli, A Basset, P Battaglia, D Bonino, E Branchini, M Brescia, J Brinchmann, A Caillat, S Camera, V Capobianco, C Carbone, J Carretero, S Casas, M Castellano, G Castignani, S Cavuoti, A Cimatti, C Colodro-Conde, G Congedo, C. J Conselice, L Conversi, Y Copin, F Courbin, H. M Courtois, M Cropper, A Da Silva, H Degaudenzi, G De Lucia, J Dinis, F Dubath, X Dupac, S Dusini, M Fabricius, M Farina, S Farrens, F Faustini, S Ferriol, P Fosalba, M Frailis, E Franceschi, M Fumana, S Galeotta, B Garilli, K George, W Gillard, B Gillis, C Giocoli, P Gómez-Alvarez, A Grazian, F Grupp, L Guzzo, S. V. H Haugan, J Hoar, H Hoekstra, W Holmes, F Hormuth, A Hornstrup, P Hudelot, K Jahnke, M Jhabvala, E Keihänen, S Kermiche, A Kiessling, M Kilbinger, B Kubik, M Kunz, H Kurki-Suonio, R Laureijs, D. Le Mignant, S Ligori, P. B Lilje, V Lindholm, I Lloro, E Maiorano, O Mansutti, O Marggraf, K Markovic, M Martinelli, N Martinet, F Marulli, R Massey, E Medinaceli, S Mei, M Melchior, Y Mellier, M Meneghetti, E Merlin, G Meylan, M Moresco, L Moscardini, C Neissner, S. -M Niemi, J. W Nightingale, C Padilla, S Paltani, F Pasian, K Pedersen, W. J Percival, V Pettorino, S Pires, G Polenta, M Poncet, L. A Popa, L Pozzetti, F Raison, R Rebolo, A Refregier, A Renzi, J Rhodes, G Riccio, E Romelli, M Roncarelli, E Rossetti, R Saglia, Z Sakr, A. G Sánchez, D Sapone, B Sartoris, M Sauvage, P Schneider, T Schrabback, A Secroun, E Sefusatti, G Seidel, M Seiffert, S Serrano, C Sirignano, G Sirri, J Skottfelt, L Stanco, J Steinwagner, P Tallada-CrespÃ, A. N Taylor, H. I Teplitz, I Tereno, R Toledo-Moreo, F Torradeflot, A Tsyganov, I Tutusaus, L Valenziano, T Vassallo, A Veropalumbo, Y Wang, J Weller, G Zamorani, E Zucca, C Burigana, V Scottez, D Scott, R. L Smart , In: Astronomy and astrophysics
The instruments at the focus of the Euclid space observatory offer superb,
diffraction-limited imaging over an unprecedented (from space) wide field of
view of 0.57 deg$^2$. This exquisite image quality has the potential to produce
high-precision astrometry for point sources once the undersampling of Euclid's
cameras is taken into account by means of accurate, effective point spread
function (ePSF) modelling. We present a complex, detailed workflow to
simultaneously solve for the geometric distortion (GD) and model the
undersampled ePSFs of the Euclid detectors. Our procedure was successfully
developed and tested with data from the Early Release Observations (ERO)
programme focused on the nearby globular cluster NGC 6397. Our final
one-dimensional astrometric precision for a well-measured star just below
saturation is 0.7 mas (0.007 pixel) for the Visible Instrument (VIS) and 3 mas
(0.01 pixel) for the Near-Infrared Spectrometer and Photometer (NISP). Finally,
we present a specific scientific application of this high-precision astrometry:
the combination of Euclid and Gaia data to compute proper motions and study the
internal kinematics of NGC 6397. Future work, when more data become available,
will allow for a better characterisation of the ePSFs and GD corrections that
are derived here, along with assessment of their temporal stability, and their
dependencies on the spectral energy distribution of the sources as seen through
the wide-band filters of Euclid.
