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Title: COSMOLOGY FROM GRAVITATIONAL LENS TIME DELAYS AND PLANCK DATA

Abstract

Under the assumption of a flat ΛCDM cosmology, recent data from the Planck satellite point toward a Hubble constant that is in tension with that measured by gravitational lens time delays and by the local distance ladder. Prosaically, this difference could arise from unknown systematic uncertainties in some of the measurements. More interestingly—if systematics were ruled out—resolving the tension would require a departure from the flat ΛCDM cosmology, introducing, for example, a modest amount of spatial curvature, or a non-trivial dark energy equation of state. To begin to address these issues, we present an analysis of the gravitational lens RXJ1131–1231 that is improved in one particular regard: we examine the issue of systematic error introduced by an assumed lens model density profile. We use more flexible gravitational lens models with baryonic and dark matter components, and find that the exquisite Hubble Space Telescope image with thousands of intensity pixels in the Einstein ring and the stellar velocity dispersion of the lens contain sufficient information to constrain these more flexible models. The total uncertainty on the time-delay distance is 6.6% for a single system. We proceed to combine our improved time-delay distance measurement with the WMAP9 and Planck posteriors. In anmore » open ΛCDM model, the data for RXJ1131–1231 in combination with Planck favor a flat universe with Ω{sub k}=0.00{sub −0.02}{sup +0.01} (68% credible interval (CI)). In a flat wCDM model, the combination of RXJ1131–1231 and Planck yields w=−1.52{sub −0.20}{sup +0.19} (68% CI)« less

Authors:
 [1]; ;  [2]; ;  [3]; ;  [4]; ;  [5]; ; ;  [6];  [7];  [8]
  1. Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China)
  2. Department of Physics, University of California, Santa Barbara, CA 93106 (United States)
  3. Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, D-85748 Garching (Germany)
  4. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
  5. Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94035 (United States)
  6. Laboratoire d'Astrophysique, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290-CH Versoix (Switzerland)
  7. Department of Physics, University of California, Davis, CA 95616 (United States)
  8. Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700-AV Groningen (Netherlands)
Publication Date:
OSTI Identifier:
22365769
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 788; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BARYONS; COSMOLOGICAL CONSTANT; COSMOLOGY; DATA ANALYSIS; DISTANCE; EQUATIONS OF STATE; ERRORS; GALAXIES; GRAVITATIONAL LENSES; IMAGES; NONLUMINOUS MATTER; SATELLITES; SPACE; TELESCOPES; TIME DELAY; UNIVERSE

Citation Formats

Suyu, S. H., Treu, T., Sonnenfeld, A., Hilbert, S., Spiniello, C., Auger, M. W., Collett, T., Blandford, R. D., Marshall, P. J., Courbin, F., Meylan, G., Tewes, M., Fassnacht, C. D., and Koopmans, L. V. E., E-mail: suyu@asiaa.sinica.edu.tw. COSMOLOGY FROM GRAVITATIONAL LENS TIME DELAYS AND PLANCK DATA. United States: N. p., 2014. Web. doi:10.1088/2041-8205/788/2/L35.
Suyu, S. H., Treu, T., Sonnenfeld, A., Hilbert, S., Spiniello, C., Auger, M. W., Collett, T., Blandford, R. D., Marshall, P. J., Courbin, F., Meylan, G., Tewes, M., Fassnacht, C. D., & Koopmans, L. V. E., E-mail: suyu@asiaa.sinica.edu.tw. COSMOLOGY FROM GRAVITATIONAL LENS TIME DELAYS AND PLANCK DATA. United States. doi:10.1088/2041-8205/788/2/L35.
Suyu, S. H., Treu, T., Sonnenfeld, A., Hilbert, S., Spiniello, C., Auger, M. W., Collett, T., Blandford, R. D., Marshall, P. J., Courbin, F., Meylan, G., Tewes, M., Fassnacht, C. D., and Koopmans, L. V. E., E-mail: suyu@asiaa.sinica.edu.tw. Fri . "COSMOLOGY FROM GRAVITATIONAL LENS TIME DELAYS AND PLANCK DATA". United States. doi:10.1088/2041-8205/788/2/L35.
@article{osti_22365769,
title = {COSMOLOGY FROM GRAVITATIONAL LENS TIME DELAYS AND PLANCK DATA},
author = {Suyu, S. H. and Treu, T. and Sonnenfeld, A. and Hilbert, S. and Spiniello, C. and Auger, M. W. and Collett, T. and Blandford, R. D. and Marshall, P. J. and Courbin, F. and Meylan, G. and Tewes, M. and Fassnacht, C. D. and Koopmans, L. V. E., E-mail: suyu@asiaa.sinica.edu.tw},
abstractNote = {Under the assumption of a flat ΛCDM cosmology, recent data from the Planck satellite point toward a Hubble constant that is in tension with that measured by gravitational lens time delays and by the local distance ladder. Prosaically, this difference could arise from unknown systematic uncertainties in some of the measurements. More interestingly—if systematics were ruled out—resolving the tension would require a departure from the flat ΛCDM cosmology, introducing, for example, a modest amount of spatial curvature, or a non-trivial dark energy equation of state. To begin to address these issues, we present an analysis of the gravitational lens RXJ1131–1231 that is improved in one particular regard: we examine the issue of systematic error introduced by an assumed lens model density profile. We use more flexible gravitational lens models with baryonic and dark matter components, and find that the exquisite Hubble Space Telescope image with thousands of intensity pixels in the Einstein ring and the stellar velocity dispersion of the lens contain sufficient information to constrain these more flexible models. The total uncertainty on the time-delay distance is 6.6% for a single system. We proceed to combine our improved time-delay distance measurement with the WMAP9 and Planck posteriors. In an open ΛCDM model, the data for RXJ1131–1231 in combination with Planck favor a flat universe with Ω{sub k}=0.00{sub −0.02}{sup +0.01} (68% credible interval (CI)). In a flat wCDM model, the combination of RXJ1131–1231 and Planck yields w=−1.52{sub −0.20}{sup +0.19} (68% CI)},
doi = {10.1088/2041-8205/788/2/L35},
journal = {Astrophysical Journal Letters},
number = 2,
volume = 788,
place = {United States},
year = {Fri Jun 20 00:00:00 EDT 2014},
month = {Fri Jun 20 00:00:00 EDT 2014}
}
  • We analyze the effects of large-scale inhomogeneities upon the observables of a gravitational lens system, focusing on the issue of whether large-scale structure imperils the program to determine the Hubble parameter through measurements of time delays between multiple images in lens systems. We find that the lens equation in a spatially flat Robertson-Walker cosmology with scalar metric fluctuations is equivalent, to the leading order of approximation, to that for the same lensing system in the absence of fluctuations but with a different angular position of the source relative to the lens axis. Since the absolute position of the source ismore » not observable, gravitational lens measurements cannot directly reveal the presence of large-scale structure. Large-scale perturbations do not modify the functional relationship between observable lens parameters and the Hubble parameter and therefore do not seriously affect the determination of {ital H}{sub 0} from lens time delays. {copyright} {ital 1996 The American Astronomical Society.}« less
  • Future large ensembles of time delay (TD) lenses have the potential to provide interesting cosmological constraints complementary to those of other methods. In a flat universe with constant w including a Planck prior, The Large Synoptic Survey Telescope TD measurements for approx4000 lenses should constrain the local Hubble constant h to approx0.007 (approx1%), OMEGA{sub de} to approx0.005, and w to approx0.026 (all 1sigma precisions). Similar constraints could be obtained by a dedicated gravitational lens observatory (OMEGA) which would obtain precise TD and mass model measurements for approx100 well-studied lenses. We compare these constraints (as well as those for a moremore » general cosmology) to the 'optimistic Stage IV' constraints expected from weak lensing, supernovae, baryon acoustic oscillations, and cluster counts, as calculated by the Dark Energy Task Force. TDs yield a modest constraint on a time-varying w(z), with the best constraint on w(z) at the 'pivot redshift' of z approx 0.31. Our Fisher matrix calculation is provided to allow TD constraints to be easily compared to and combined with constraints from other experiments. We also show how cosmological constraining power varies as a function of numbers of lenses, lens model uncertainty, TD precision, redshift precision, and the ratio of four-image to two-image lenses.« less
  • Time delays between lensed multiple images have been known to provide an interesting probe of the Hubble constant, but such application is often limited by degeneracies with the shape of lens potentials. We propose a new statistical approach to examine the dependence of time delays on the complexity of lens potentials, such as higher-order perturbations, non-isothermality, and substructures. Specifically, we introduce a reduced time delay of the dimensionless form, and explore its behavior analytically and numerically as a function of the image configuration that is characterized by the asymmetry and opening angle of the image pair. In particular we derivemore » a realistic conditional probability distribution for a given image configuration from Monte-Carlo simulations. We find that the probability distribution is sensitive to the image configuration such that more symmetric and/or smaller opening angle image pairs are more easily affected by perturbations on the primary lens potential. On average time delays of double lenses are less scattered than those of quadruple lenses. Furthermore, the realistic conditional distribution allows a new statistical method to constrain the Hubble constant from observed time delays. We find that 15 published time delay quasars constrain the Hubble constant to be H{sub 0} = 70 {+-} 3km s{sup -1} Mpc{sup -1}. While systematic errors coming from the heterogeneous nature of the quasar sample and the uncertainty of the input distribution of lens potentials should be considered, reasonable agreement with other estimates indicates the usefulness of our new approach as a cosmological and astrophysical probe, particularly in the era of large-scale synoptic surveys.« less
  • Using Fermat's principle, we analyze the effects of very long wavelength gravitational waves upon the images of a gravitationally lensed quasar. We show that the lens equation in the presence of gravity waves is equivalent to that of a lens with a different alignment between source, deflector, and observer in the absence of gravity waves. Contrary to a recent claim, we conclude that measurements of time delays in gravitational lenses cannot serve as a method to detect or constrain a stochastic background of gravitational waves of cosmological wavelengths, because the wave-induced time delay is observationally indistinguishable from an intrinsic timemore » delay due to the lens geometry.« less
  • We show that dark matter substructure in galaxy-scale halos perturbs the time delays between images in strong gravitational lens systems. The variance of the effect depends on the subhalo mass function, scaling as the product of the substructure mass fraction, and a characteristic mass of subhalos (namely (m {sup 2})/(m)). Time delay perturbations therefore complement gravitational lens flux ratio anomalies and astrometric perturbations by measuring a different moment of the subhalo mass function. Unlike flux ratio anomalies, 'time delay millilensing' is unaffected by dust extinction or stellar microlensing in the lens galaxy. Furthermore, we show that time delay ratios aremore » immune to the radial profile degeneracy that usually plagues lens modeling. We lay out a mathematical theory of time delay perturbations and find it to be tractable and attractive. We predict that in 'cusp' lenses with close triplets of images, substructure may change the arrival-time order of the images (compared with smooth models). We discuss the possibility that this effect has already been observed in RX J1131-1231.« less