Euclid: Precise inference of defocus wavefront error from image diffraction spike measurements
本文提出了一种快速、与模型无关的方法,通过测量非对称衍射星芒中的亚像素位移,来精确推断欧几里得望远镜的离焦情况,从而实现了监测和修正对弱引力透镜宇宙学至关重要的点扩散函数变化所需的高灵敏度。
原作者: D. Neumann (Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands), L. Miller (Department of Physics, Oxford University, Keble Road, Oxford OX1 3RH, UK), H. Hoekstra (Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands), K. Kuijken (Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands), I. H. Whittam (Department of Physics, Oxford University, Keble Road, Oxford OX1 3RH, UK, Department of Physics and Astronomy, University of the Western Cape, Bellville, Cape Town, 7535, South Africa), N. E. Chisari (Institute for Theoretical Physics, Utrecht University, Princetonplein 5, 3584 CE Utrecht, The Netherlands, Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands), R. Nakajima (Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany), B. Altieri (ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain), A. Amara (School of Mathematics and Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK), S. Andreon (INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy), N. Auricchio (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), C. Baccigalupi (IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy, INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy, SISSA, International School for Advanced Studies, Via Bonomea 265, 34136 Trieste TS, Italy), M. Baldi (Dipartimento di Fisica e Astronomia, Università di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), S. Bardelli (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), A. Basset (Centre National d'Etudes Spatiales -- Centre spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France), P. Battaglia (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), A. Biviano (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy), E. Branchini (Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146, Genova, Italy, INFN-Sezione di Genova, Via Dodecaneso 33, 16146, Genova, Italy, INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy), M. Brescia (Department of Physics "E. Pancini", University Federico II, Via Cinthia 6, 80126, Napoli, Italy, INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy), S. Camera (Dipartimento di Fisica, Università degli Studi di Torino, Via P. Giuria 1, 10125 Torino, Italy, INFN-Sezione di Torino, Via P. Giuria 1, 10125 Torino, Italy, INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese), G. Cañas-Herrera (Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands), V. Capobianco (INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese), C. Carbone (INAF-IASF Milano, Via Alfonso Corti 12, 20133 Milano, Italy), J. Carretero (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Port d'Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra), M. Castellano (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy), G. Castignani (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), S. Cavuoti (INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy, INFN section of Naples, Via Cinthia 6, 80126, Napoli, Italy), K. C. Chambers (Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA), A. Cimatti (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), C. Colodro-Conde (Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain), G. Congedo (Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK), C. J. Conselice (Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK), L. Conversi (European Space Agency/ESRIN, Largo Galileo Galilei 1, 00044 Frascati, Roma, Italy, ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain), Y. Copin (Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France), F. Courbin (Institut de Ciències del Cosmos, Institució Catalana de Recerca i Estudis Avançats, Institut de Ciencies de l'Espai), H. M. Courtois (UCB Lyon 1, CNRS/IN2P3, IUF, IP2I Lyon, 4 rue Enrico Fermi, 69622 Villeurbanne, France), M. Cropper (Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK), H. Degaudenzi (Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland), G. De Lucia (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), H. Dole (Université Paris-Saclay, CNRS, Institut d'astrophysique spatiale, 91405, Orsay, France), F. Dubath (Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland), X. Dupac (ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain), M. Farina (INAF-Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere, 100, 00100 Roma, Italy), R. Farinelli (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), S. Farrens (Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191, Gif-sur-Yvette, France), S. Ferriol (Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France), S. Fotopoulou (School of Physics, HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK), N. Fourmanoit (Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France), M. Frailis (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), E. Franceschi (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), M. Fumana (INAF-IASF Milano, Via Alfonso Corti 12, 20133 Milano, Italy), S. Galeotta (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), K. George (University Observatory, LMU Faculty of Physics, Scheinerstr.~1, 81679 Munich, Germany), B. Gillis (Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK), C. Giocoli (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), P. Gómez-Alvarez (FRACTAL S.L.N.E., calle Tulipán 2, Portal 13 1A, 28231, Las Rozas de Madrid, Spain, ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain), J. Gracia-Carpio (Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany), A. Grazian (INAF-Osservatorio Astronomico di Padova, Via dell'Osservatorio 5, 35122 Padova, Italy), F. Grupp (Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany, Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr.~1, 81679 München, Germany), S. V. H. Haugan (Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, 0315 Oslo, Norway), W. Holmes (Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA), F. Hormuth (Felix Hormuth Engineering, Goethestr. 17, 69181 Leimen, Germany), A. Hornstrup (Technical University of Denmark, Elektrovej 327, 2800 Kgs. Lyngby, Denmark, Cosmic Dawn Center), K. Jahnke (Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany), M. Jhabvala (NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA), B. Joachimi (Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK), S. Kermiche (Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France), A. Kiessling (Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA), M. Kilbinger (Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191, Gif-sur-Yvette, France), R. Kohley (ESAC/ESA, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Cañada, Madrid, Spain), B. Kubik (Université Claude Bernard Lyon 1, CNRS/IN2P3, IP2I Lyon, UMR 5822, Villeurbanne, F-69100, France), M. Kunz (Université de Genève, Département de Physique Théorique and Centre for Astroparticle Physics, 24 quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland), H. Kurki-Suonio (Department of Physics, P.O. Box 64, University of Helsinki, 00014 Helsinki, Finland, Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland), R. Laureijs (Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands), A. M. C. Le Brun (Laboratoire d'etude de l'Univers et des phenomenes eXtremes, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS, 92190 Meudon, France), S. Ligori (INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese), P. B. Lilje (Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, 0315 Oslo, Norway), V. Lindholm (Department of Physics, P.O. Box 64, University of Helsinki, 00014 Helsinki, Finland, Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland), I. Lloro (SKAO, Jodrell Bank, Lower Withington, Macclesfield SK11 9FT, UK), G. Mainetti (Centre de Calcul de l'IN2P3/CNRS, 21 avenue Pierre de Coubertin 69627 Villeurbanne Cedex, France), O. Mansutti (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), O. Marggraf (Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany), M. Martinelli (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy, INFN-Sezione di Roma, Piazzale Aldo Moro, 2 - c/o Dipartimento di Fisica, Edificio G. Marconi, 00185 Roma, Italy), N. Martinet (Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France), F. Marulli (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), R. J. Massey (Department of Physics, Institute for Computational Cosmology, Durham University, South Road, Durham, DH1 3LE, UK), E. Medinaceli (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), S. Mei (Université Paris Cité, CNRS, Astroparticule et Cosmologie, 75013 Paris, France, CNRS-UCB International Research Laboratory, Centre Pierre Binétruy, IRL2007, CPB-IN2P3, Berkeley, USA), M. Meneghetti (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), E. Merlin (INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monteporzio Catone, Italy), G. Meylan (Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne), A. Mora (Telespazio UK S.L. for European Space Agency), M. Moresco (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), C. Moretti (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, IFPU, Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy, INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy), L. Moscardini (Dipartimento di Fisica e Astronomia "Augusto Righi" - Alma Mater Studiorum Università di Bologna, via Piero Gobetti 93/2, 40129 Bologna, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), C. Neissner (Institut de Física d'Altes Energies, Port d'Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra), R. C. Nichol (School of Mathematics and Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK), S. -M. Niemi (European Space Agency/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands), C. Padilla (Institut de Física d'Altes Energies), S. Paltani (Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland), F. Pasian (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), K. Pedersen (DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 155, 2200 Copenhagen, Denmark), W. J. Percival (Waterloo Centre for Astrophysics, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada, Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada, Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada), V. Pettorino (European Space Agency/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands), A. Pezzotta (INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy), S. Pires (Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191, Gif-sur-Yvette, France), G. Polenta (Space Science Data Center, Italian Space Agency, via del Politecnico snc, 00133 Roma, Italy), M. Poncet (Centre National d'Etudes Spatiales -- Centre spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France), L. A. Popa (Institute of Space Science, Str. Atomistilor, nr. 409 Măgurele, Ilfov, 077125, Romania), G. D. Racca (Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands, European Space Agency/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands), F. Raison (Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany), A. Renzi (Dipartimento di Fisica e Astronomia "G. Galilei", Università di Padova, Via Marzolo 8, 35131 Padova, Italy, INFN-Padova, Via Marzolo 8, 35131 Padova, Italy, INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), J. Rhodes (Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA), G. Riccio (INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy), E. Romelli (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), M. Roncarelli (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), R. Saglia (Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr.~1, 81679 München, Germany, Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany), Z. Sakr (Instituto de Física Teórica UAM-CSIC, Campus de Cantoblanco, 28049 Madrid, Spain, Institut de Recherche en Astrophysique et Planétologie, Université St Joseph, Faculty of Sciences, Beirut, Lebanon), D. Sapone (Departamento de Física, FCFM, Universidad de Chile, Blanco Encalada 2008, Santiago, Chile), B. Sartoris (Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr.~1, 81679 München, Germany, INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy), M. Schirmer (Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany), P. Schneider (Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany), T. Schrabback (Universität Innsbruck, Institut für Astro- und Teilchenphysik, Technikerstr. 25/8, 6020 Innsbruck, Austria), A. Secroun (Aix-Marseille Université, CNRS/IN2P3, CPPM, Marseille, France), E. Sihvola (Department of Physics and Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland), P. Simon (Universität Bonn, Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany), C. Sirignano (Dipartimento di Fisica e Astronomia "G. Galilei", Università di Padova, Via Marzolo 8, 35131 Padova, Italy, INFN-Padova, Via Marzolo 8, 35131 Padova, Italy), G. Sirri (INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy), A. Spurio Mancini (Department of Physics, Royal Holloway, University of London, Surrey TW20 0EX, UK), L. Stanco (INFN-Padova, Via Marzolo 8, 35131 Padova, Italy), P. Tallada-Crespí (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Port d'Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra), A. N. Taylor (Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK), I. Tereno (Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Edifício C8, Campo Grande, PT1749-016 Lisboa, Portugal, Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências, Universidade de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal), N. Tessore (Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK), S. Toft (Cosmic Dawn Center, Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen, Denmark), R. Toledo-Moreo (Universidad Politécnica de Cartagena, Departamento de Electrónica y Tecnología de Computadoras, Plaza del Hospital 1, 30202 Cartagena, Spain, European University of Technology EUt+, European Union), F. Torradeflot (Port d'Informació Científica, Campus UAB, C. Albareda s/n, 08193 Bellaterra, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas), I. Tutusaus (Institute of Space Sciences, Institut d'Estudis Espacials de Catalunya, Institut de Recherche en Astrophysique et Planétologie), L. Valenziano (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Bologna, Via Irnerio 46, 40126 Bologna, Italy), J. Valiviita (Department of Physics, P.O. Box 64, University of Helsinki, 00014 Helsinki, Finland, Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00014 Helsinki, Finland), T. Vassallo (INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, University Observatory, LMU Faculty of Physics, Scheinerstr.~1, 81679 Munich, Germany), A. Veropalumbo (INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy, INFN-Sezione di Genova, Via Dodecaneso 33, 16146, Genova, Italy, Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146, Genova, Italy), Y. Wang (Caltech/IPAC, 1200 E. California Blvd., Pasadena, CA 91125, USA), J. Weller (Universitäts-Sternwarte München, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr.~1, 81679 München, Germany, Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany), G. Zamorani (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy), F. M. Zerbi (INAF-Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano, Italy), A. Gregorio (Dipartimento di Fisica - Sezione di Astronomia, Università di Trieste, Via Tiepolo 11, 34131 Trieste, Italy, INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy, INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste TS, Italy), A. Loureiro (Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, Stockholm, SE-106 91, Sweden, Astrophysics Group, Blackett Laboratory, Imperial College London, London SW7 2AZ, UK), M. Sereno (INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy, INFN-Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy)
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想象一下,欧几里得(Euclid)空间望远镜就像一台漂浮在深空中的巨型、超精密相机,任务是为15亿个星系拍摄一张“全家福”。其目标是测量这些星系由于宇宙中不可见的引力而产生的轻微挤压或拉伸程度。为了实现这一目标,相机的对焦必须完美无缺。如果镜头哪怕只有一点点失焦,星系看起来就会发生畸变,科学家可能会将这种畸变误认为是引力,从而毁掉整个实验。
本文介绍了一种巧妙、快速且无需模型的监测方法,用于检查欧几里得相机的对焦情况,它利用了一个通常会被视为干扰的特征:衍射星芒(diffraction spikes)。
问题所在:“蜘蛛”困扰镜头
大多数望远镜都有一个由细长支架(类似于蜘蛛腿)支撑的副镜,位于主透镜的前方。当明亮的恒星光线穿过这些支架时,会产生从恒星向外辐射出的四条长而细的光线,称为衍射星芒。通常,天文学家会试图消除这些星芒,因为它们看起来像是伪影。
然而,欧几里得望远镜的设计非常独特:它的“蜘蛛腿”并不是对称排列的。因此,这些星芒不会完美重叠。
解决方案:“三角形”妙招
作者意识到,当望远镜轻微失焦(defocus)时,这些星芒不仅仅是变得模糊,它们还会改变位置。
把三个主要的星芒想象成围绕恒星绘制的一个三角形的三个顶点。
- 在完美对焦时: 这个三角形的大小是固定的。
- 失焦时: 这个三角形会扩张或收缩,其顶点会向内或向外移动。
本文提出了一种方法,可以在短短几秒钟内测量这个“星芒三角形”的大小。通过测量这个三角形的大小,他们可以精确计算出望远镜的副镜沿光轴移动了多远。
精确度如何?
该方法具有惊人的灵敏度。
- 它能检测到小至 0.022 微米(即 22 纳米)的镜面移动。
- 为了让你有个直观的概念,这大约是人类头发宽度的 1/40,或者大约是一条 DNA 链的厚度。
- 这种精度足以追踪由空间温度变化引起的望远镜极其微小的“呼吸”运动。
他们发现了什么?
利用这个“星芒三角形”标尺,团队分析了欧几里得的数据,并发现了一些了不起的现象:
- 望远镜非常稳固: 自 2024 年 7 月以来,欧几里得望远镜表现得异常稳定。它的焦点不会像哈勃空间望远镜那样剧烈漂移(哈勃会因为地球阴影的影响,每隔几小时在约 2 微米范围内“呼吸”进出)。欧几里得的焦点只会有极微小的波动,主要源于正常的的热变化。
- “除霜”效应: 望远镜曾两次进行加热处理(分别在 2024 年 3 月和 6 月),以融化积聚在镜面上的冰。作者发现,这些加热事件永久性地改变了“星芒三角形”在整个视场中的表现方式。这就像如果你加热了一个金属尺,它不仅是暂时膨胀,而且其刻度标记也发生了永久性的偏移。这意味着望远镜的光学状态在这些事件发生后发生了永久性的改变。
- 颜色也有影响(但很小): 该方法基本是“色盲”的,但他们注意到恒星的颜色会对测量结果产生轻微影响。这可能是因为望远镜中有一个将光线分解成不同颜色的特殊反射镜。不过,这种影响非常微小,不足以在大多数恒星的测量中破坏结果。
为什么这很重要?
这种方法是一种“快速且直接”(在好的意义上)的现实检验。
- 无需猜测: 它不需要一个复杂的计算机模型来模拟望远镜“应该”是什么样子。它只需观察星芒并进行测量。
- 实时监测: 它能在几秒钟内告诉科学家望远镜是否发生了焦点漂移。
- 更好的宇宙学研究: 通过了解精确的对焦情况,科学家可以修正所研究星系的形状。这确保了在计算宇宙膨胀时,他们不会被一个略微模糊的相机所误导。
简而言之,作者将一个麻烦(衍射星芒)变成了一个高精度的标尺,证明了欧几里得望远镜足够稳定,能够进行有史以来最精确的宇宙测量。
技术摘要:Euclid:基于图像衍射尖峰测量实现精确的离焦波前误差推断
问题陈述
Euclid 任务在弱引力透镜宇宙学方面的成功,依赖于对星系形状的精确测量,这要求对点扩散函数(PSF)有前所未有的理解。PSF 模型中的系统误差,特别是源于离焦波前误差(WFE)的误差,会直接导致推断的星系形状产生偏差。离焦被认为是 Euclid 有效载荷中最易变化的 WFE 组件,主要由热波动驱动。虽然 Euclid 财团采用了光学 PSF 的前向建模,但对离焦进行持续、独立的监测对于约束这些模型并监控航天器的光学状态具有重要价值。现有方法通常依赖于先验 PSF 模型或专门的波前传感器;目前需要一种能够直接从巡天曝光中推导出的快速、与模型无关的估计器。
方法论
作者提出了一种通过测量由亮星产生的衍射尖峰的亚像素位移,来估计 Euclid VIS 仪器离焦的方法。该方法利用了望远镜次级镜(M2)支架在镜面非对称性的布置特点。与对称支架配置中尖峰重叠并遮蔽位移的情况不同,Euclid 的非对称支架产生了清晰且互不重叠的衍射尖峰。
核心方法论包括:
- 尖峰检测: 对于亮星(Gaia G 星等 11.5–15.5),算法迭代寻找每个衍射尖峰的中心,使得一阶亮度矩为零。
- 三角形面积度量: 三个尖峰的位置构成一个三角形。该三角形所围成的面积平方根(ADS)被用作离焦的度量指标。三角形的方向决定了离焦的正负(前焦或后焦)。
- 定标: 利用 2024 年初的相位多样性定标(PDC)数据(当时次级镜被有意移动到已知位置 ±18μm 和 0μm),作者建立了 ADS 与次级镜位移(Δz)之间的线性关系。
- 迭代估计: 为了解释与视场(FoV)相关的基线 WFE 变化,作者从稳定的参考时期构建了一个高分辨率的“基线”模板 ADS。从单个曝光中减去该基线,以隔离相对离焦变化(Δzobs)。
主要贡献
- 与模型无关的估计器: 该方法不需要先验 PSF 模型,并能在数秒内从单个巡天曝光中推断出离焦。
- 高精度: 该估计器实现了单次曝光精度 σ(Δz)=0.022μm,对应于 0.75 nm 的峰谷值光程差。
- 物理阐释: 离焦被直接表示为沿光轴的次级镜位移,从而能够直接与热和机械层面的航天器行为相关联。
- 通用性: 该技术适用于任何在入射瞳孔中具有薄、直且非镜面对称遮挡物的望远镜,例如罗曼空间望远镜(Roman Space Telescope)。
结果
- 时间稳定性: 自 2024 年 7 月经历两次除冰行动以来,Euclid 望远镜表现出了极高的稳定性。离焦变化通常在 0.1–0.3 μm 量级,与热变化高度相关,且比哈勃空间望远镜观察到的“呼吸”变化小两个数量级。
- 除冰的影响: 论文表明,2024 年 3 月和 6 月的除冰行动引起了底层视场相关 WFE 结构的显著且不可逆的变化。基线离焦分布发生了偏移,使得重新评估 PSF 模型的波前误差假设成为必要。
- 视场依赖性: 虽然对于大多数巡天过程,离焦在视场内是均匀变化的,但作者识别出了一种“基线”视场依赖性。减去该基线可将离焦估计的不确定性降低 3.22 倍。
- 色度与星等依赖性: 检测到了推断的离焦与恒星颜色(Gaia GBP−GRP)之间的轻微相关性,这归因于分色镜产生的色差 WFE。然而,对于典型的恒星族群,该效应在统计学上小于该方法的统计不确定性。此外还观察到了星等依赖性,这可能是由于非常亮(溢出)或暗的恒星在尖峰检测算法中存在系统效应所致。
- PSF 尺寸要求: 作者将离焦估计与 Euclid 对 PSF 尺寸偏差的要求(∣ΔRPSF2/RPSF2∣<10−3)进行了关联。他们确定,当场平均次级镜位移超过 ⟨Δzthr⟩=(0.0683±0.0024)μm 时,将违反该要求。观测到的望远镜稳定性(变化远低于此阈值)表明,长时间的标称巡天数据可以作为 PSF 建模的稳定定标场。
意义
该论文声称,此方法为 Euclid 航天器提供了一个稳健的实时监测工具,并为计算密集型的 PSF 模型拟合提供了严格的先验。通过证明除冰后 Euclid 望远镜前所未有的稳定性,这项工作验证了该任务在相干星系形状测量方面的设计目标。能够追踪热诱导位移和时间演化,而无需额外的硬件或复杂的建模,增强了弱引力透镜宇宙学推断的可靠性。此外,该方法提供了一个快速、便捷的途径,用于监测航天器光学状态的演化,其应用范围不仅限于 Euclid,也适用于其他具有类似光学配置的望远镜。
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