First Light for GRAVITY Wide: Large Separation Fringe Tracking for the Very Large Telescope Interferometer

R. Abuter (1) , F. Allouche (2) , A. Amorim (3, 4) , C. Bailet (2) , M. Bauböck (5) , J.-P. Berger (6) , P. Berio (2) , A. Bigioli (7) , O. Boebion (2) , M. L. Bolzer (5, 8) , H. Bonnet (1) , G. Bourdarot (6) , P. Bourget (1) , W. Brandner (9) , Y. Clénet (10) , B. Courtney-Barrer (1, 11) , Y. Dallilar (5) , R. Davies (5) , D. Defrère (12) , A. Delboulbé (6) , F. Delplancke (1) , R. Dembet (10) , P. T. de Zeeuw (13, 5) , A. Drescher (5) , A. Eckart (14, 15) , C. Édouard (10) , F. Eisenhauer , M. Fabricius , H. Feuchtgruber , G. Finger , N. M. Förster Schreiber , E. Garcia , P. Garcia , F. Gao , E. Gendron (10) , R. Genzel , J. P. Gil , S. Gillessen , T. Gomes , F. Gonté , C. Gouvret , P. Guajardo , S. Guieu , M. Hartl , X. Haubois , F. Haußmann , G. Heißel , Th. Henning , S. Hippler , S. Hönig , M. Horrobin , N. Hubin , E. Jacqmart , L. Jochum , L. Jocou , A. Kaufer , P. Kervella (10) , H. Korhonen , L. Kreidberg , S. Lacour (10) , S. Lagarde , O. Lai , V. Lapeyrère , R. Laugier , J.-B. Le Bouquin , J. Leftley , P. Léna (10) , D. Lutz , F. Mang , A. Marcotto , D. Maurel , A. Mérand , F. Millour , N. More , H. Nowacki , M. Nowak , S. Oberti , T. Ott , L. Pallanca , T. Paumard (10) , K. Perraut , G. Perrin (10) , R. Petrov , O. Pfuhl , N. Pourré , S. Rabien , C. Rau , S. Robbe-Dubois , S. Rochat , M. Salman , M. Schöller , J. Schubert , N. Schuhler , J. Shangguan , T. Shimizu , S. Scheithauer , A. Sevin , F. Soulez , A. Spang , E. Stadler , J. Stadler , C. Straubmeier , E. Sturm , L. J. Tacconi , K. R. W. Tristram , F. Vincent (10) , S. von Fellenberg , S. Uysal , F. Widmann , E. Wieprecht , E. Wiezorrek , J. Woillez , S. Yazici , A. Young , G. Zins

1 ESO - European Southern Observatory
2 LAGRANGE - Joseph Louis LAGRANGE
3 Universidade de Lisboa
4 CENTRA - Centro de Astrofísica e Gravitação
5 MPE - Max Planck Institute for Extraterrestrial Physics
6 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
7 Institute of Astronomy [Leuven]
8 TUM - Technische Universität Munchen - Technical University Munich - Université Technique de Munich
9 MPIA - Max-Planck-Institut für Astronomie
10 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics
11 RSAA - Research School of Astronomy and Astrophysics [Canberra]
12 KU Leuven - Catholic University of Leuven = Katholieke Universiteit Leuven
13 Sterrewacht Leiden
14 I. Physikalisches Institut [Köln]
15 MPIFR - Max-Planck-Institut für Radioastronomie

GRAVITY+ is the upgrade of GRAVITY and the Very Large Telescope Interferometer (VLTI) with wide-separation fringe tracking, new adaptive optics, and laser guide stars on all four 8~m Unit Telescopes (UTs), for ever fainter, all-sky, high contrast, milliarcsecond interferometry. Here we present the design and first results of the first phase of GRAVITY+, called GRAVITY Wide. GRAVITY Wide combines the dual-beam capabilities of the VLTI and the GRAVITY instrument to increase the maximum separation between the science target and the reference star from 2 arcseconds with the 8 m UTs up to several 10 arcseconds, limited only by the Earth's turbulent atmosphere. This increases the sky-coverage of GRAVITY by two orders of magnitude, opening up milliarcsecond resolution observations of faint objects, and in particular the extragalactic sky. The first observations in 2019 - 2022 include first infrared interferometry of two redshift $z\sim2$ quasars, interferometric imaging on the binary system HD 105913A, and repeated observations of multiple star systems in the Orion Trapezium Cluster. We find the coherence loss between the science object and fringe-tracking reference star well described by the turbulence of the Earth's atmosphere. We confirm that the larger apertures of the UTs result in higher visibilities for a given separation due to larger overlap of the projected pupils on sky and give predictions for visibility loss as a function of separation to be used for future planning.

Mots clés: Astrophysics - Instrumentation and Methods for Astrophysics

Domaines: Astrophysique [astro-ph]

R. Abuter, F. Allouche, A. Amorim, C. Bailet, M. Bauböck, et al.. First Light for GRAVITY Wide: Large Separation Fringe Tracking for the Very Large Telescope Interferometer. Astronomy and Astrophysics - A&A, 2022, ⟨10.1051/0004-6361/202243941⟩. ⟨hal-03856361⟩