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Title: Exploring the dark energy redshift desert with the Sandage-Loeb test

Abstract

We study the prospects for constraining dark energy at very high redshift with the Sandage-Loeb test--a measurement of the evolution of cosmic redshift obtained by taking quasar spectra at sufficiently separated epochs. This test is unique in its coverage of the 'redshift desert,' corresponding roughly to redshifts between 2 and 5, where other dark energy probes are unable to provide useful information about the cosmic expansion history. Extremely large telescopes planned for construction in the near future, with ultrahigh resolution spectrographs (such as the proposed CODEX), will indeed be able to measure cosmic redshift variations of quasar Lyman-{alpha} absorption lines over a period as short as ten years. We find that these measurements can constrain nonstandard and dynamical dark energy models with high significance and in a redshift range not accessible with future dark energy surveys. As the cosmic signal increases linearly with time, measurements made over several decades by a generation of patient cosmologists may provide definitive constraints on the expansion history in the era that follows the dark ages but precedes the time when standard candles and rulers come into existence.

Authors:
 [1];  [2];  [3]
  1. LUTH, CNRS UMR 8102, Observatoire de Paris-Meudon, 5 Place Jules Janssen, 92195 Meudon Cedex (France)
  2. Kavli Institute for Cosmological Physics and Astronomy and Astrophysics Department, University of Chicago, Chicago, Illinois 60637 (United States)
  3. Dipartimento di Fisica e Sezione INFN, Universita degli Studi di Roma 'La Sapienza', Ple Aldo Moro 5, 00185, Rome (Italy)
Publication Date:
OSTI Identifier:
21020118
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevD.75.062001; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; ACCELERATION; COSMOLOGY; ENERGY SPECTRA; EVOLUTION; INFLATIONARY UNIVERSE; NONLUMINOUS MATTER; QUASARS; RED SHIFT; TIME MEASUREMENT; VARIATIONS

Citation Formats

Corasaniti, Pier-Stefano, Huterer, Dragan, and Melchiorri, Alessandro. Exploring the dark energy redshift desert with the Sandage-Loeb test. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.062001.
Corasaniti, Pier-Stefano, Huterer, Dragan, & Melchiorri, Alessandro. Exploring the dark energy redshift desert with the Sandage-Loeb test. United States. doi:10.1103/PHYSREVD.75.062001.
Corasaniti, Pier-Stefano, Huterer, Dragan, and Melchiorri, Alessandro. Thu . "Exploring the dark energy redshift desert with the Sandage-Loeb test". United States. doi:10.1103/PHYSREVD.75.062001.
@article{osti_21020118,
title = {Exploring the dark energy redshift desert with the Sandage-Loeb test},
author = {Corasaniti, Pier-Stefano and Huterer, Dragan and Melchiorri, Alessandro},
abstractNote = {We study the prospects for constraining dark energy at very high redshift with the Sandage-Loeb test--a measurement of the evolution of cosmic redshift obtained by taking quasar spectra at sufficiently separated epochs. This test is unique in its coverage of the 'redshift desert,' corresponding roughly to redshifts between 2 and 5, where other dark energy probes are unable to provide useful information about the cosmic expansion history. Extremely large telescopes planned for construction in the near future, with ultrahigh resolution spectrographs (such as the proposed CODEX), will indeed be able to measure cosmic redshift variations of quasar Lyman-{alpha} absorption lines over a period as short as ten years. We find that these measurements can constrain nonstandard and dynamical dark energy models with high significance and in a redshift range not accessible with future dark energy surveys. As the cosmic signal increases linearly with time, measurements made over several decades by a generation of patient cosmologists may provide definitive constraints on the expansion history in the era that follows the dark ages but precedes the time when standard candles and rulers come into existence.},
doi = {10.1103/PHYSREVD.75.062001},
journal = {Physical Review. D, Particles Fields},
number = 6,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Taking into account that the Sandage-Loeb test is unique in its coverage of the redshift desert and available in the near future, we explore the cosmic time evolution behavior of the source redshift for the holographic dark energy model, an important competing cosmological model. As a result, we find that the Sandage-Loeb test can provide an extremely strong bound on {omega}{sub m}{sup 0}, while its constraint on another dimensionless parameter {lambda} is weak. In addition, it is proposed here for the first time that we can also constrain various cosmological models by measuring the value of z{sub max} at whichmore » the peak of redshift velocity occurs. Combining this new proposed method with the traditional Sandage-Loeb test, we should be able to provide a better constraint on {lambda}, at least from the theoretical perspective.« less
  • The Sandage-Loeb (SL) test is a unique method to probe dark energy in the ''redshift desert'' of 2∼
  • The Sandage-Loeb (SL) test directly measures the expansion rate of the universe in the redshift range of 2 ∼< z ∼< 5 by detecting redshift drift in the spectra of Lyman-α forest of distant quasars. We discuss the impact of the future SL test data on parameter estimation for the ΛCDM, the wCDM, and the w{sub 0}w{sub a}CDM models. To avoid the potential inconsistency with other observational data, we take the best-fitting dark energy model constrained by the current observations as the fiducial model to produce 30 mock SL test data. The SL test data provide an important supplement to the other dark energymore » probes, since they are extremely helpful in breaking the existing parameter degeneracies. We show that the strong degeneracy between Ω{sub m} and H{sub 0} in all the three dark energy models is well broken by the SL test. Compared to the current combined data of type Ia supernovae, baryon acoustic oscillation, cosmic microwave background, and Hubble constant, the 30-yr observation of SL test could improve the constraints on Ω{sub m} and H{sub 0} by more than 60% for all the three models. But the SL test can only moderately improve the constraint on the equation of state of dark energy. We show that a 30-yr observation of SL test could help improve the constraint on constant w by about 25%, and improve the constraints on w{sub 0} and w{sub a} by about 20% and 15%, respectively. We also quantify the constraining power of the SL test in the future high-precision joint geometric constraints on dark energy. The mock future supernova and baryon acoustic oscillation data are simulated based on the space-based project JDEM. We find that the 30-yr observation of SL test would help improve the measurement precision of Ω{sub m}, H{sub 0}, and w{sub a} by more than 70%, 20%, and 60%, respectively, for the w{sub 0}w{sub a}CDM model.« less
  • We use the effective field theory of dark energy to explore the space of modified gravity models which are capable of driving the present cosmic acceleration. We identify five universal functions of cosmic time that are enough to describe a wide range of theories containing a single scalar degree of freedom in addition to the metric. The first function (the effective equation of state) uniquely controls the expansion history of the universe. The remaining four functions appear in the linear cosmological perturbation equations, but only three of them regulate the growth history of large scale structures. We propose a specificmore » parameterization of such functions in terms of characteristic coefficients that serve as coordinates in the space of modified gravity theories and can be effectively constrained by the next generation of cosmological experiments. We address in full generality the problem of the soundness of the theory against ghost-like and gradient instabilities and show how the space of non-pathological models shrinks when a more negative equation of state parameter is considered. This analysis allows us to locate a large class of stable theories that violate the null energy condition (i.e. super-acceleration models) and to recover, as particular subsets, various models considered so far. Finally, under the assumption that the true underlying cosmological model is the Λ Cold Dark Matter (ΛCDM) scenario, and relying on the figure of merit of EUCLID-like observations, we demonstrate that the theoretical requirement of stability significantly narrows the empirical likelihood, increasing the discriminatory power of data. We also find that the vast majority of these non-pathological theories generating the same expansion history as the ΛCDM model predict a different, lower, growth rate of cosmic structures.« less