================================================================================ Euclid: High-precision imaging astrometry and photometry from Early Release Observations. I. Internal kinematics of NGC 6397 by combining Euclid and Gaia data M. Libralato, L. R. Bedin, M. Griggio, D. Massari, J. Anderson, J.-C. Cuillandre, A. M. N. Ferguson, A. Lançon, S. S. Larsen, M. Schirmer, F. Annibali, E. Balbinot, E. Dalessandro, D. Erkal, P. B. Kuzma, T. Saifollahi, G. Verdoes Kleijn, M. Kümmel, R. Nakajima, M. Correnti, G. Battaglia, B. Altieri, A. Amara, 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. Construes, 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, R. C. Nichol, 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-Crespí, 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,and R. L. Smart, =References ? ================================================================================ Keywords: astrometry – photometry – proper motions – stellar clusters – globular clusters: individual: NGC 6397 Abstract: 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 sq. deg. This exquisite image quality has the potential to produce high-precision astrometry for point sources once the undersampling of the 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 assessing their temporal stability, and their dependencies on the spectral energy distribution of the sources as seen through the wide-band filters of Euclid. Description: Astro-photometric catalogs and stacked images of NGC 6397. The astrometrized stacked images do not currently take into account for tangent-plane-projection effects. Also, fluxes are not properly resampled. Thus, these images are meant for visual reference only and not for scientific investigations. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . this file ngc6397.dat 358 474706 NGC 6397 astro-photometric catalog fits/* . 4 Individual fits images -------------------------------------------------------------------------------- Byte-by-byte Description of file: ngc6397.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 14 F14.10 --- ra Right Ascension (ICRS) at Ep=2023 16- 29 F14.10 --- dec Declination (ICRS) at Ep=2023 31- 36 I6 --- idvis ID number of the source 38- 47 F10.4 --- xvis VIS X master-frame position (100mas/pixel) 49- 58 F10.4 --- yvis VIS Y master-frame position (100mas/pixel) 60- 66 F7.4 --- mvis Calibrated VIS I_E magnitude (1) 68- 73 F6.4 --- sxvis VIS X position rms (5) 75- 80 F6.4 --- syvis VIS Y position rms (5) 82- 87 F6.4 --- smvis VIS I_E magnitude rms (5) 89- 94 F6.4 --- qvis VIS I_E quality-of-PSF-fit parameter (5) 96- 96 I1 --- nfvis Number of individual VIS I_E exposures in which an object was found (5) 98- 98 I1 --- nuvis Number of individual VIS I_E exposures used to measure an object (5) 100-109 F10.4 --- xnispy NISP Y_E X master-frame position (300mas/pixel) (6) 111-120 F10.4 --- ynispy NISP Y_E Y master-frame position (300mas/pixel) (6) 122-128 F7.4 --- mnispy Calibrated NISP Y_E magnitude (2) (6) 130-135 F6.4 --- sxnispy NISP Y_E X position rms (5) (6) 137-142 F6.4 --- synispy NISP Y_E Y position rms (5) (6) 144-149 F6.4 --- smnispy NISP Y_E magnitude rms (5) (6) 151-156 F6.4 --- qnispy NISP Y_E quality-of-PSF-fit parameter (5) (6) 158-158 I1 --- nfnispy Number of individual NISP Y_E exposures in which an object was found (5) (6) 160-160 I1 --- nunispy Number of individual NISP Y_E exposures used to measure an object (5) (6) 162-171 F10.4 --- xnispj NISP J_E X master-frame position (300mas/pixel) (6) 173-182 F10.4 --- ynispj NISP J_E X master-frame position (300mas/pixel) (6) 184-190 F7.4 --- mnispj Calibrated NISP J_E magnitude (3) (6) 192-197 F6.4 --- sxnispj NISP J_E X position rms (5) (6) 199-204 F6.4 --- synispj NISP J_E Y position rms (5) (6) 206-211 F6.4 --- smnispj NISP J_E magnitude rms (5) (6) 213-218 F6.4 --- qnispj NISP J_E quality-of-PSF-fit parameter (5) (6) 220-220 I1 --- nfnispj Number of individual NISP J_E exposures in which an object was found (5) (6) 222-222 I1 --- nunispj Number of individual NISP J_E exposures used to measure an object (5) (6) 224-233 F10.4 --- xnisph NISP H_E X master-frame position (300mas/pixel) (6) 235-244 F10.4 --- ynisph NISP H_E X master-frame position (300mas/pixel) (6) 246-252 F7.4 --- mnisph Calibrated NISP H_E magnitude (4) (6) 254-259 F6.4 --- sxnisph NISP H_E X position rms (5) (6) 261-266 F6.4 --- synisph NISP H_E Y position rms (5) (6) 268-273 F6.4 --- smnisph NISP H_E magnitude rms (5) (6) 275-280 F6.4 --- qnisph NISP H_E quality-of-PSF-fit parameter (5) (6) 282-282 I1 --- nfnisph Number of individual NISP H_E exposures in which an object was found (5) (6) 284-284 I1 --- nunisph Number of individual NISP H_E exposures used to measure an object (5) (6) 286-294 F9.5 --- pmra Proper motion along R.A. cos(Dec.) (mas/yr) (7) 296-304 F9.5 --- pmdec Proper motion along Dec. (mas/yr) (7) 306-313 F8.5 --- epmra Error on the proper motion along R.A. cos(Dec.) (mas/yr) (7) 315-321 F7.5 --- epmdec Error on the proper motion along Dec. (mas/yr) (7) 323-331 F9.5 --- pmrac Proper motion along R.A. cos(Dec.) corrected for the color-dependent systematic (mas/yr) (7) 333-341 F9.5 --- pmdecc Proper motion along Dec. corrected for the color-dependent systematic (mas/yr) (7) 343-350 F8.5 --- epmrac Error on the proper motion along R.A. cos(Dec.) corrected for the color-dependent systematic (mas/yr) (7) 352-358 F7.5 --- epmdecc Error on the proper motion along Dec. corrected for the color-dependent systematic (mas/yr) (7) -------------------------------------------------------------------------------- Note (1): Stars saturated in the VIS I_E catalog have a magnitude <= ~18.8. Note (2): Stars saturated in the NISP Y_E catalog have a magnitude <= ~16.2. Note (3): Stars saturated in the NISP J_E catalog have a magnitude <= ~16.5. Note (4): Stars saturated in the NISP H_E catalog have a magnitude <= ~16.5. Note (5): Saturated stars have positional rms, magnitude rms, quality-of-PSF-fit and/or proper motions that can be set to a value greater or equal to 0. We advise extreme caution when dealing with saturated stars. Note (6): Stars not measured in a NISP filter have all the corresponding parameters set to 0. Note (7): Stars without a proper-motion measurement have proper motions and corresponding errors set to 0. ------------------------------------------------------------------------------- Acknowledgements: Mattia Libralato, mattia.libralato(at)inaf.it ================================================================================