In this paper, we assemble a catalog of 118 strong gravitational lensing systems from SLACS, BELLS, LSD and SL2S surveys and use them to constrain the cosmic equation of state. In particular we consider two cases of dark energy phenomenology: XCDM model where dark energy is modeled by a fluid with constant w equation of state parameter and in Chevalier -Polarski -Linder (CPL) parametrization where w is allowed to evolve with redshift: w(z) = w 0 + w 1 z 1+z . We assume spherically symmetric mass distribution in lensing galaxies, but relax the rigid assumption of SIS model in favor to more general power-law index γ, also allowing it to evolve with redshifts γ(z). Our results for the XCDM cosmology show the agreement with values (concerning both w and γ parameters) obtained by other authors. We go further and constrain the CPL parameters jointly with γ(z). The resulting confidence regions for the parameters are much better than those obtained with a similar method in the past. They are also showing -2 -a trend of being complementary to the supernova Ia data. Our analysis demonstrates that strong gravitational lensing systems can be used to probe cosmological parameters like the cosmic equation of state for dark energy. Moreover, they have a potential to judge whether the cosmic equation of state evolved with time or not.

In this paper, we present a new compiled milliarcsecond compact radio data set of 120 intermediate-luminosity quasars in the redshift range 0.46 < z < 2.76. These quasars show negligible dependence on redshifts and intrinsic luminosity, and thus represents, in the standard model of cosmology, a fixed comoving-length of standard ruler. We implement a new cosmology-independent technique to calibrate the linear size of of this standard ruler as l m = 11.03 ± 0.25 pc, which is the typical radius at which AGN

Future observations of cosmic microwave background (CMB) polarisation have the potential to answer some of the most fundamental questions of modern physics and cosmology, including: What physical process gave birth to the Universe we see today? What are the dark matter and dark energy that seem to constitute 95% of the energy density of the Universe? Do we need extensions to the standard model of particle physics and fundamental interactions? Is the ΛCDM cosmological scenario correct, or are we missing an essential piece of the puzzle? In this paper, we list the requirements for a future CMB polarisation survey addressing these scientific objectives, and discuss the design drivers of the CORE space mission proposed to ESA in answer to the "M5" call for a medium-sized mission. The rationale and options, and the methodologies used to assess the mission's performance, are of interest to other future CMB mission design studies. CORE has 19 frequency channels, distributed over a broad frequency range, spanning the 60-600 GHz interval, to control astrophysical foreground emission. The angular resolution ranges from 2 to 18 , and the aggregate CMB sensitivity is about 2 µK.arcmin. The observations are made with a single integrated focal-plane instrument, consisting of an array of 2100 cryogenically-cooled, linearly-polarised detectors at the focus of a 1.2-m aperture cross-Dragone telescope. The mission is designed to minimise all sources of systematic effects, which must be controlled so that no more than 10 −4 of the intensity leaks into polarisation maps, and no more than about 1% of E-type polarisation leaks into B-type modes. CORE observes the sky from a large Lissajous orbit around the Sun-Earth L2 point on an orbit that offers stable observing conditions and avoids contamination from sidelobe pick-up of stray radiation originating from the Sun, Earth, and Moon. The entire sky is observed repeatedly during four years of continuous scanning, with a combination of three rotations of the spacecraft over different timescales. With about 50% of the sky covered every few days, this scan strategy provides the mitigation of systematic effects and the internal redundancy that are needed to convincingly extract the primordial B-mode signal on large angular scales, and check with adequate sensitivity the consistency of the observations in several independent data subsets. CORE is designed as a "near-ultimate" CMB polarisation mission which, for optimal complementarity with ground-based observations, will perform the observations that are known to be essential to CMB polarisation science and cannot be obtained by any other means than a dedicated space mission. It will provide well-characterised, highly-redundant multi-frequency observations of polarisation at all the scales where foreground emission and cosmic variance dominate the final uncertainty for obtaining precision CMB science, as well as 2 angular resolution maps of high-frequency foreground emission in the 300-600 GHz frequency range, essential for complementarity w...

The standard siren approach of gravitational wave cosmology appeals to the direct luminosity distance estimation through the waveform signals from inspiralling double compact binaries, especially those with electromagnetic counterparts providing redshifts. It is limited by the calibration uncertainties in strain amplitude and relies on the fine details of the waveform. The Einstein telescope is expected to produce 104–105 gravitational wave detections per year, 50–100 of which will be lensed. Here, we report a waveform-independent strategy to achieve precise cosmography by combining the accurately measured time delays from strongly lensed gravitational wave signals with the images and redshifts observed in the electromagnetic domain. We demonstrate that just 10 such systems can provide a Hubble constant uncertainty of 0.68% for a flat lambda cold dark matter universe in the era of third-generation ground-based detectors.

Abstract. Gravitational wave (GW) experiments are entering their advanced stage whichshould soon open a new observational window on the Universe. Looking into this future, the Einstein Telescope (ET) was designed to have a fantastic sensitivity improving significantly over the advanced GW detectors. One of the most important astrophysical GW sources supposed to be detected by the ET in large numbers are double compact objects (DCO) and some of such events should be gravitationally lensed by intervening galaxies.We explore the prospects of observing gravitationally lensed inspiral DCO events in the ET. This analysis is a significant extension of our previous paper Piórkowska et al. [6]. We are using the intrinsic merger rates of the whole class of DCO (NS-NS,BH-NS,BH-BH)located at different redshifts as calculated by Dominik et al. [5] by using StarTrack population synthesis evolutionary code. We discuss in details predictions from each evolutionary scenario. Our general conclusion is that ET would register about 50 − 100 strongly lensed inspiral events per year. Only the scenario in which nascent BHs receive strong kick gives the predictions of a few events per year. Such lensed events would be dominated by the BH-BH merging binary systems. Our results suggest that during a few years of successful operation ET will provide a considerable catalog of strongly lensed events.

Strong lensing has developed into an important astrophysical tool for probing both cosmology and galaxies (their structure, formation, and evolution). Using the gravitational lensing theory and cluster mass distribution model, we try to collect a relatively complete observational data concerning the Hubble constant independent ratio between two angular diameter distances D ds /D s from various large systematic gravitational lens surveys and lensing by galaxy clusters combined with X-ray observations, and check the possibility to use it in the future as complementary to other cosmological probes. On one hand, strongly gravitationally lensed quasar-galaxy systems create such a new opportunity by combining stellar kinematics (central velocity dispersion measurements) with lensing geometry (Einstein radius determination from position of images). We apply such a method to a combined gravitational lens data set including 70 data points from Sloan Lens ACS (SLACS) and Lens Structure and Dynamics survey (LSD). On the other hand, a new sample of 10 lensing galaxy clusters with redshifts ranging from 0.1 to 0.6 carefully selected from strong gravitational lensing systems with both X-ray satellite observations and optical giant luminous arcs, is also used to constrain three dark energy models (ΛCDM, constant w and CPL) under a flat universe assumption. For the full sample (n = 80) and the restricted sample (n = 46) including 36 two-image lenses and 10 strong lensing arcs, we obtain relatively good fitting values of basic cosmological parameters, which generally agree with the results already known in the literature. This results encourages further development of this method and its use on larger samples obtained in the future.

Under very general assumptions of metric theory of spacetime, photons traveling along null geodesics and photon number conservation, two observable concepts of cosmic distance, i.e. the angular diameter and the luminosity distances are related to each other by the so-called distance duality relation (DDR)Observational validation of this relation is quite important because any evidence of its violation could be a signal of new physics. In this paper we introduce a new method to test DDR based on strong gravitational lensing systems and type Ia supernovae under a flat universe. The method itself is worth attention, because unlike previously proposed techniques, it does not depend on all other prior assumptions concerning the details of cosmological model. We tested it using a new compilation of strong lensing systems and JLA compilation of type Ia supernovae and found no evidence of DDR violation. For completeness, we also combined it with previous cluster data and showed its power on constraining DDR. It could become a promising new probe in the future in light of forthcoming massive strong lensing surveys and because of expected advances in galaxy cluster modlelling.

In this paper, based on a 2.29 GHz VLBI all-sky survey of 613 milliarcsecond ultracompact radio sources with 0.0035 < z < 3.787, we describe a method of identifying the sub-sample which can serve as individual standard rulers in cosmology. If the linear size of the compact structure is assumed to depend on source luminosity and redshift as l m = lL β (1 + z) n , only intermediate-luminosity quasars (10 27 W/Hz< L < 10 28 W/Hz) show negligible dependence (|n| ≃ 10 −3 , |β| ≃ 10 −4 ), and thus represent a population of such rulers with fixed characteristic length l = 11.42 pc. With a sample of 120 such sources covering the redshift range 0.46 < z < 2.80, we confirm the existence of dark energy in the Universe with high significance under the assumption of a flat universe, and obtain stringent constraints on both the matter density Ω m = 0.323 Mpc. Similar reconstruction of the expansion rate function H(z) based on the data from cosmic chronometers and BAO gives us H(z m ) = 176.77 ± 6.11 km sec −1 Mpc −1 . These measurements are used to estimate the speed of light: c = 3.039(±0.180) × 10 5 km/s. This is the first measurement of the speed of light in a cosmological setting referring to the distant past.