15131514 KANN ET AL.Vol. 720 ABSTRACT We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) afterglows including GRBs up to 2009 September, for a total of 76 GRBs, and present an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A, and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host-galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z = 1 system and compared their luminosities with a sample of pre-Swift afterglows. The results of a former study, which showed that GRB afterglows clustered and exhibited a bimodal distribution in luminosity space, are weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) is very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at 1 day after the GRB in the z = 1 system. A comparative study of the optical luminosities of GRB afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without, reveals no indication that the former are statistically significantly more luminous. Furthermore, we propose the existence of an upper ceiling on afterglow luminosities and study the luminosity distribution at early times, which was not accessible before the advent of the Swift satellite. Most GRBs feature afterglows that are dominated by the forward shock from early times on. Finally, we present the first indications of a class of long GRBs, which form a bridge between the typical highluminosity, high-redshift events and nearby low-luminosity events (which are also associated with spectroscopic supernovae) in terms of energetics and observed redshift distribution, indicating a continuous distribution overall.

We show that a cosmic standard ruler can be constructed from the joint measurement of the time delay, Δτ, between gravitationally lensed quasar images and the velocity dispersion, σ, of the lensing galaxy. This is specifically shown, for a singular isothermal sphere lens, D OL ∝ Δτ/σ 2 , where D OL is the angular diameter distance to the lens. Using MCMC simulations we illustrate the constraints set in the Ω m − Ω Λ plane from future observations.

We present a survey of the extinction properties of 10 lensing galaxies, in the redshift range z ¼ 0:04Y1:01, using multiply lensed quasars imaged with the ESO VLT in the optical and near-infrared. The multiple images act as ''standard light sources'' shining through different parts of the lensing galaxy, allowing for extinction studies by comparison of pairs of images. We explore the effects of systematics in the extinction curve analysis, including extinction along both lines of sight and microlensing, using theoretical analysis and simulations. In the sample, we see variation in both the amount and type of extinction. Of the 10 systems, seven are consistent with extinction along at least one line of sight. The mean differential extinction for the most extinguished image pair for each lens isĀ(V ) ¼ 0:56 AE 0:04, using Galactic extinction law parameterization. The corresponding meanR V ¼ 2:8 AE 0:4 is consistent with that of the Milky Way at R V ¼ 3:1, where R V ¼ A(V )/E(B À V ). We do not see any strong evidence for evolution of extinction properties with redshift. Of the 10 systems, B1152+199 shows the strongest extinction signal of A(V ) ¼ 2:43 AE 0:09 and is consistent with a Galactic extinction law with R V ¼ 2:1 AE 0:1. Given the similar redshift distribution of SN Ia hosts and lensing galaxies, a large space-based study of multiply imaged quasars would be a useful complement to future dark energy SN Ia surveys, providing independent constraints on the statistical extinction properties of galaxies up to z $ 1. Subject headingg s: dust, extinction -galaxies: ISM -gravitational lensing 1 Based on observations made with ESO Telescopes at the La Silla or Paranal Observatories under program IDs 065.O-0666 and 066.A-0264.

We present a simultaneous analysis of 18 galaxy lenses with time delay measurements. For each lens we derive mass maps using pixelated simultaneous modeling with shared Hubble constant. We estimate the Hubble constant to be 66 +6 −4 km s −1 Mpc −1 (for a flat Universe with Ω m = 0.3, Ω Λ = 0.7). We have also selected a subsample of five relatively isolated early type galaxies and by simultaneous modeling with an additional constraint on isothermality of their mass profiles we get H 0 = 76 +3 −3 km s −1 Mpc −1 .Subject headings: gravitational lensing, cosmological parameters DOLDOS DLS, where D OL , D OS , D LS are the angular diameter distances between observer and lens, observer and source, and lens and source, respec-