Fundamental physics with Espresso: Towards an accurate wavelength calibration for a precision test of the fine-structure constant
Creators: name: Schmidt, Tobias M.
name: Molaro, Paolo
name: Murphy, Michael T.
name: Lovis, Christophe
name: Cupani, Guido
name: Cristiani, Stefano
name: Pepe, Francesco A.
name: Rebolo, Rafael
name: Santos, Nuno C.
name: Abreu, Manuel
name: Adibekyan, Vardan
name: Alibert, Yann
name: Aliverti, Matteo
name: Allart, Romain
name: Prieto, Carlos Allende
name: Alves, David
name: Baldini, Veronica
name: Broeg, Christopher
name: Cabral, Alexandre
name: Calderone, Giorgio
name: Cirami, Roberto
name: Coelho, João
name: Coretti, Igor
name: D'Odorico, Valentina
name: Di Marcantonio, Paolo
name: Ehrenreich, David
name: Figueira, Pedro
name: Genoni, Matteo
name: Santos, Ricardo Génova
name: Hernández, Jonay I. González
name: Kerber, Florian
name: Landoni, Marco
name: Leite, Ana C. O.
name: Lizon, Jean-Louis
name: Curto, Gaspare Lo
name: Manescau, Antonio
name: Martins, Carlos J. A. P.
name: Megévand, Denis
name: Mehner, Andrea
name: Micela, Giuseppina
name: Modigliani, Andrea
name: Monteiro, Manuel
name: Monteiro, Mario J. P. F. G.
name: Mueller, Eric
name: Nunes, Nelson J.
name: Oggioni, Luca
name: Oliveira, António
name: Pariani, Giorgio
name: Pasquini, Luca
name: Redaelli, Edoardo
name: Riva, Marco
name: Santos, Pedro
name: Sosnowska, Danuta
name: Sousa, Sérgio G.
name: Sozzetti, Alessandro
name: Mascareño, Alejandro Suárez
name: Udry, Stéphane
name: Osorio, Maria-Rosa Zapatero
name: Zerbi, Filippo
Publisher: name: arXiv
Year: 2020
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Observations of metal absorption systems in the spectra of distant quasars allow to constrain a possible variation of the fine-structure constant throughout the history of the Universe. Such a test poses utmost demands on the wavelength accuracy and previous studies were limited by systematics in the spectrograph wavelength calibration. A substantial advance in the field is therefore expected from the new ultra-stable high-resolution spectrograph Espresso, recently installed at the VLT. In preparation of the fundamental physics related part of the Espresso GTO program, we present a thorough assessment of the Espresso wavelength accuracy and identify possible systematics at each of the different steps involved in the wavelength calibration process. Most importantly, we compare the default wavelength solution, based on the combination of Thorium-Argon arc lamp spectra and a Fabry-Pérot interferometer, to the fully independent calibration obtained from a laser frequency comb. We find wavelength-dependent discrepancies of up to 24m/s. This substantially exceeds the photon noise and highlights the presence of different sources of systematics, which we characterize in detail as part of this study. Nevertheless, our study demonstrates the outstanding accuracy of Espresso with respect to previously used spectrographs and we show that constraints of a relative change of the fine-structure constant at the $10^{-6}$ level can be obtained with Espresso without being limited by wavelength calibration systematics.
description: 27 pages, accepted for publication in A&amp;A