Cosmic dynamics in the era of Extremely Large Telescopes

Jochen Liske (1) , A. Grazian (2) , Eros Vanzella (3) , Miroslava Dessauges-Zavadsky (4) , Matteo Viel (3) , Luca Pasquini (1) , Martin Haehnelt (5) , Stefano Cristiani (3) , Francesco Pepe (4) , Gerardo Avila (1) , Piercarlo Bonifacio (3, 6, 7, 8) , François Bouchy (9, 10) , Hans Dekker (1) , Bernard Delabre (1) , Sandro d'Odorico (1) , Valentina d'Odorico (3) , Sergei A. Levshakov (11) , Christophe Lovis (4) , Michel Mayor (4) , Paolo Molaro (3) , L. Moscardini (12) , M. T. Murphy (5) , Didier Queloz (4) , P. Shaver (1) , Stéphane Udry (4) , Tommy Wiklind (13, 14) , S. Zucker (15)

1 ESO - European Southern Observatory
2 INAF-OAR - INAF-Osservatorio Astronomico di Roma
3 INAF-OATs - INAF-Osservatorio Astronomico di Trieste
4 Observatoire Astronomique de l'Université de Genève
5 IoA - Institute of Astronomy, University of Cambridge
6 CIFIST - Cosmological Impact of the First Stars
7 GEPI - Galaxies, Etoiles, Physique, Instrumentation
8 Physique stellaire et galactique
9 LAM - Laboratoire d'Astrophysique de Marseille
10 OHP - Observatoire de Haute-Provence
11 A.F. Ioffe Physical-Technical Institute
12 UNIBO - Alma Mater Studiorum Università di Bologna = University of Bologna
13 STScI - Space Telescope Science Institute
14 ESA - Agence Spatiale Européenne = European Space Agency
15 TAU - Tel Aviv University

The redshifts of all cosmologically distant sources are expected to experience a small, systematic drift as a function of time due to the evolution of the Universe's expansion rate. A measurement of this effect would represent a direct and entirely model-independent determination of the expansion history of the Universe over a redshift range that is inaccessible to other methods. Here we investigate the impact of the next generation of Extremely Large Telescopes on the feasibility of detecting and characterizing the cosmological redshift drift. We consider the Lyalpha forest in the redshift range 2 < z < 5 and other absorption lines in the spectra of high-redshift QSOs as the most suitable targets for a redshift drift experiment. Assuming photon-noise-limited observations and using extensive Monte Carlo simulations we determine the accuracy to which the redshift drift can be measured from the Lyalpha forest as a function of signal-to-noise ratio and redshift. Based on this relation and using the brightness and redshift distributions of known QSOs we find that a 42-m telescope is capable of unambiguously detecting the redshift drift over a period of ~20 yr using 4000 h of observing time. Such an experiment would provide independent evidence for the existence of dark energy without assuming spatial flatness, using any other cosmological constraints or making any other astrophysical assumption.

Domaines: Astrophysique [astro-ph]

Jochen Liske, A. Grazian, Eros Vanzella, Miroslava Dessauges-Zavadsky, Matteo Viel, et al.. Cosmic dynamics in the era of Extremely Large Telescopes. Monthly Notices of the Royal Astronomical Society, 2008, 386, pp.1192-1218. ⟨10.1111/j.1365-2966.2008.13090.x⟩. ⟨hal-03786052⟩