arXiv subjects

Marek Biesiada

Publications and source records attributed to Marek Biesiada.

At least 91 records · Page 5Linked to original sources

arXiv2017

Ultra-compact structure in intermediate-luminosity radio quasars: building a sample of standard cosmological rulers and improving the dark energy constraints up to $z\sim 3$

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 $l_m= 11.03\pm0.25$ pc, which is the typical radius at which AGN jets become opaque at the observed frequency $ν\sim 2$ GHz. In the framework of flat $Λ$CDM model, we find a high value of the matter density parameter, $Ω_m=0.322^{+0.244}_{-0.141}$, and a low value of the Hubble constant, $H_0=67.6^{+7.8}_{-7.4}\; \rm{kms}^{-1}\rm{Mpc}^{-1}$, which is in excellent agreement with the CMB anisotropy measurements by \textit{Planck}. We obtain ${Ω_m}=0.309^{+0.215}_{-0.151}$, $w=-0.970^{+0.500}_{-1.730}$ at 68.3% CL for the constant $w$ of a dynamical dark-energy model, which demonstrates no significant deviation from the concordance $Λ$CDM model. Consistent fitting results are also obtained for other cosmological models explaining the cosmic acceleration, like Ricci dark energy (RDE) or Dvali-Gabadadze-Porrati (DGP) brane-world scenario. While no significant change in $w$ with redshift is detected, there is still considerable room for evolution in $w$ and the transition redshift at which $w$ departing from -1 is located at $z\sim 2.0$. Our results demonstrate that the method extensively investigated in our work on observational radio quasar data can be used to effectively derive cosmological information. Finally, we find the combination of high-redshift quasars and low-redshift clusters may provide an important source of angular diameter distances, considering the redshift coverage of these two astrophysical probes.

astro-ph.CO↗

arXiv2017

New observational constraints on $f(T)$ cosmology from radio quasars

Using a new recently compiled milliarcsecond compact radio data set of 120 intermediate-luminosity quasars in the redshift range $0.46< z <2.76$, whose statistical linear sizes show negligible dependence on redshifts and intrinsic luminosity and thus represent standard rulers in cosmology, we constrain three viable and most popular $f(T)$ gravity models, where $T$ is the torsion scalar in teleparallel gravity. Our analysis reveals that constraining power of the quasars data (N=120) is comparable to the Union2.1 SN Ia data (N=580) for all three $f(T)$ models. Together with other standard ruler probes such as Cosmic Microwave Background and Baryon Acoustic Oscillation distance measurements, the present value of the matter density parameter $Ω_m$ obtained by quasars is much lager than that derived from other observations. For two of the models considered ($f_1$CDM and $f_2$CDM) a small but noticeable deviation from $Λ$CDM cosmology is present, while in the framework of $f_3$CDM the effective equation of state may cross the phantom divide line at lower redshifts. These results indicate that intermediate-luminosity quasars could provide an effective observational probe comparable to SN Ia at much higher redsifts, and $f(T)$ gravity is a reasonable candidate for the modified gravity theory.

astro-ph.CO↗

arXiv2017

Speed of Gravitational Waves from Strongly Lensed Gravitational Waves and Electromagnetic Signals

We propose a new model-independent measurement strategy for the propagation speed of gravitational waves (GWs) based on strongly lensed GWs and their electromagnetic (EM) counterparts. This can be done in two ways: by comparing arrival times of GWs and their EM counterparts and by comparing the time delays between images seen in GWs and their EM counterparts. The lensed GW-EM event is perhaps the best way to identify an EM counterpart. Conceptually, this method does not rely on any specific theory of massive gravitons or modified gravity. Its differential setting (i.e., measuring the difference between time delays in GW and EM domains) makes it robust against lens modeling details (photons and GWs travel in the same lensing potential) and against internal time delays between GW and EM emission acts. It requires, however, that the theory of gravity is metric and predicts gravitational lensing similar to general relativity. We expect that such a test will become possible in the era of third-generation gravitational-wave detectors, when about 10 lensed GW events would be observed each year. The power of this method is mainly limited by the timing accuracy of the EM counterpart, which for kilonovae is around $10^4$ s.Thisuncertaintycanbesuppressedbya factor of $\sim 10^{10}$, if strongly lensed transients of much shorter duration associated with the GW event can be identified. Candidates for such short transients include short gamma-ray burst and fast radio bursts.

gr-qc↗

arXiv2017

Revisiting dark energy models using differential ages of galaxies

In this work, we use a test based on the differential ages of galaxies for distinguishing the dark energy models. As proposed by Jimenez and Loeb, relative ages of galaxies can be used to put constraints on various cosmological parameters. In the same vein, we reconstruct $H_0dt/dz$ and its derivative ($H_0d^2t/dz^2$) using a model independent technique called non-parametric smoothing. Basically, $dt/dz$ is the change in the age of the object as a function of redshift which is directly link with the Hubble parameter. Hence for reconstruction of this quantity, we use the most recent $H(z)$ data. Further, we calculate $H_0dt/dz$ and its derivative for several models like Phantom, Einstein de Sitter (EdS), $Λ$CDM, Chevallier-Polarski-Linder (CPL) parametrization, Jassal-Bagla-Padmanabhan (JBP) parametrization and Feng-Shen-Li-Li (FSLL) parametrization. We check the consistency of these models with the results of reconstruction obtained in model independent way from the data. It is observed that $H_0dt/dz$ as a tool is not able to distinguish between the $Λ$CDM, CPL, JBP and FSLL parametrizations but as expected EdS and Phantom models show noticeable deviation from the reconstructed results. Further, the derivative of $H_0dt/dz$ for various dark energy models is more sensitive at low redshift. It is observed that the FSLL model is not consistent with the reconstructed results at redshifts less than $0.5$, however, the $Λ$CDM model is in concordance with the 3$σ$ region of the reconstruction.

astro-ph.CO↗

arXiv2017

Measuring the speed of light with ultra-compact radio quasars

In this paper, based on a 2.29 GHz VLBI all-sky survey of 613 milliarcsecond ultra-compact 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 $l_m=l L^β(1+z)^n$, only intermediate-luminosity quasars ($10^{27}$ W/Hz$<L<$ $10^{28}$ W/Hz) show negligible dependence ($|n|\simeq 10^{-3}$, $|β|\simeq 10^{-4}$), 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 $Ω_m=0.323^{+0.245}_{-0.145}$ and the Hubble constant $H_0=66.30^{+7.00}_{-8.50}$ km sec$^{-1}$ Mpc$^{-1}$. Finally, with the angular diameter distances $D_A$ measured for quasars extending to high redshifts ($z\sim 3.0$), we reconstruct the $D_A(z)$ function using the technique of Gaussian processes. This allows us to identify the redshift corresponding to the maximum of the $D_A(z)$ function: $z_m=1.70$ and the corresponding angular diameter distance $D_A(z_m)=1719.01\pm43.46$ Mpc. Similar reconstruction of the expansion rate function $H(z)$ based on the data from cosmic chronometers and BAO gives us $H(z_m)=176.77\pm6.11$ km sec$^{-1}$ Mpc$^{-1}$. These measurements are used to estimate the speed of light: $c=3.039(\pm0.180)\times 10^5$ km/s. This is the first measurement of the speed of light in a cosmological setting referring to the distant past.

astro-ph.CO↗

arXiv2017

Test of parametrized post-Newtonian gravity with galaxy-scale strong lensing systems

Based on a mass-selected sample of galaxy-scale strong gravitational lenses from the SLACS, BELLS, LSD and SL2S surveys and using a well-motivated fiducial set of lens-galaxy parameters we tested the weak-field metric on kiloparsec scales and found a constraint on the post-Newtonian parameter $γ= 0.995^{+0.037}_{-0.047}$ under the assumption of a flat $Λ$CDM universe with parameters taken from \textit{Planck} observations. General relativity (GR) predicts exactly $γ=1$. Uncertainties concerning the total mass density profile, anisotropy of the velocity dispersion and the shape of the light-profile combine to systematic uncertainties of $\sim 25\%$. By applying a cosmological model independent method to the simulated future LSST data, we found a significant degeneracy between the PPN $γ$ parameter and spatial curvature of the Universe. Setting a prior on the cosmic curvature parameter $-0.007< Ω_k <0.006$, we obtained the following constraint on the PPN parameter: $γ=1.000^{+0.0023}_{-0.0025}$. We conclude that strong-lensing systems with measured stellar velocity dispersions may serve as another important probe to investigate validity of the GR, if the mass-dynamical structure of the lensing galaxies is accurately constrained in the future lens surveys.

astro-ph.CO↗

arXiv2016

Constraints on non-flat cosmologies with massive neutrinos after Planck 2015

We investigate two dark energy cosmological models (i.e., the $Λ$CDM and $ϕ$CDM models) with massive neutrinos assuming two different neutrino mass hierarchies in both the spatially flat and non-flat scenarios, where in the $ϕ$CDM model the scalar field possesses an inverse power-law potential, $V(ϕ)\propto ϕ^{-α}$ ($α>0$). Cosmic microwave background data from Planck 2015, baryon acoustic oscillations data from 6dFGS, SDSS-MGS, BOSS-LOWZ and BOSS CMASS-DR11, the JLA compilation of Type Ia supernova apparent magnitude observations, and the Hubble Space Telescope $H_0$ prior, are jointly employed to constrain the model parameters. We first determine constraints assuming three species of degenerate massive neutrinos. In the spatially flat (non-flat) $Λ$CDM model, the sum of neutrino masses is bounded as $Σm_ν < 0.165 (0.299)$ eV at 95% confidence level (CL). Correspondingly, in the flat (non-flat) $ϕ$CDM model, we find $Σm_ν < 0.164 (0.301)$ eV at 95% CL. The inclusion of spatial curvature as a free parameter results in a significant broadening of confidence regions for $Σm_ν$ and other parameters. In the scenario where the total neutrino mass is dominated by the heaviest neutrino mass eigenstate, we can obtain the similar conclusions as those obtained in the degenerate neutrino mass scenario. In addition, the results show that the bounds on $Σm_ν$ based on two different neutrino mass hierarchies have insignificant differences in the spatially flat case for both the $Λ$CDM and $ϕ$CDM models, however, the corresponding differences are larger in the non-flat case.

astro-ph.CO↗

arXiv2016

The Distance Duality Relation from Strong Gravitational Lensing

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) $D^L=D^A(1+z)^2$. 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.

astro-ph.CO↗

arXiv2016

What are $Omh^2(z_1,z_2)$ and $Om(z_1,z_2)$ diagnostics telling us in light of $H(z)$ data?

Two-point diagnostics $Om(z_i,z_j)$ and $Omh^2(z_i,z_j)$ have been introduced as an interesting tool for testing the validity of the $Λ$CDM model. Quite recently, Sahni, Shafieloo $\&$ Starobinsky (2014) combined two independent measurements of $H(z)$ from BAO data with the value of the Hubble constant $H_0$, and used the second of these diagnostics to test the $Λ$CDM model. Their result indicated a considerable tension between observations and predictions of the $Λ$CDM model. Since reliable data concerning expansion rates of the Universe at different redshifts $H(z)$ are crucial for the successful application of this method, we investigate both two-point diagnostics on the most comprehensive set of $N=36$ measurements of $H(z)$ coming from the BAO and differential ages (DA) of passively evolving galaxies. We discuss the uncertainties of two-point diagnostics and find that they are strongly non-Gaussian and follow the patterns deeply rooted in their very construction. Therefore we propose that non-parametric median statistics is the most appropriate way of treating this problem. Our results support the claims that $Λ$CDM is in tension with $H(z)$ data according to the two-point diagnostics developed by Shafieloo, Sahni and Starobinsky. However, other alternatives to the $Λ$CDM, such as wCDM or CPL models perform even worse. We also notice that there are serious systematic differences between BAO and DA methods which ought to be better understood before $H(z)$ measurements can become competitive to the other probes.

astro-ph.CO↗

arXiv2016

Limits on the power-law mass and luminosity density profiles of elliptical galaxies from gravitational lensing systems

We use 118 strong gravitational lenses observed by the SLACS, BELLS, LSD and SL2S surveys to constrain the total mass profile and the profile of luminosity density of stars (light-tracers) in elliptical galaxies up to redshift $z \sim 1$. Assuming power-law density profiles for the total mass density, $ρ=ρ_0(r/r_0)^{-α}$, and luminosity density, $ν=ν_0(r/r_0)^{-δ}$, we investigate the power law index and its first derivative with respect to the redshift. Using Monte Carlo simulations of the posterior likelihood taking the Planck's best-fitted cosmology as a prior, we find $γ= 2.132\pm0.055$ with a mild trend $\partial γ/\partial z_l= -0.067\pm0.119$ when $α=δ=γ$, suggesting that the total density profile of massive galaxies could have become slightly steeper over cosmic time. Furthermore, similar analyses performed on sub-samples defined by different lens redshifts and velocity dispersions, indicate the need of treating low, intermediate and high-mass galaxies separately. Allowing $δ$ to be a free parameter, we obtain $α=2.070\pm0.031$, $\partial α/\partial z_l= -0.121\pm0.078$, and $δ= 2.710\pm0.143$. The model in which mass traces light is rejected at $>95\%$ confidence and our analysis robustly indicates the presence of dark matter in the form of a mass component that is differently spatially extended than the light. In this case, intermediate-mass elliptical galaxies ($200$ km/s $ < σ_{ap} \leq 300$ km/s) show the best consistency with the singular isothermal sphere as an effective model of galactic lenses.

astro-ph.CO↗

arXiv2016

Testing the gas mass density profile of galaxy clusters with distance duality relation

In this paper, assuming the validity of distance duality relation, $η=D_L(z)(1+z)^{-2}/D_A(z)=1$, where $D_A(z)$ and $D_L(z)$ are the angular and the luminosity distance respectively, we explore two kinds of gas mass density profiles of clusters: the isothermal $β$ model and the non-isothermal double-$β$ model. In our analysis, performed on 38 massive galaxy clusters observed by \textit{Chandra} (within the redshift range of $0.14<z<0.89$), we use two types of cluster gas mass fraction data corresponding to different mass density profiles fitted to the X-ray data. Using two general parameterizations of $η(z)$ (phenomenologically allowing for distance duality violation), we find that the non-isothermal double-$β$ model agrees better with the distance duality relation, while the isothermal $β$ model tends to be marginally incompatible with the Etherington theorem at 68.3% CL. However, current accuracy of the data does not allow to distinguish between the two models for the gas-density distribution at a significant level.

astro-ph.CO↗

arXiv2015

Comparison of cosmological models using standard rulers and candles

In this paper, we used standard rulers and standard candles (separately and jointly) to explore five popular dark energy models under assumption of spatial flatness of the Universe. As standard rulers, we used a data set comprising 118 galactic-scale strong lensing systems (individual standard rulers if properly calibrated for the mass density profile) combined with BAO diagnostics (statistical standard ruler). Supernovae Ia served asstandard candles. Unlike in the most of previous statistical studies involving strong lensing systems, we relaxed the assumption of singular isothermal sphere (SIS) in favor of its generalization: the power-law mass density profile. Therefore, along with cosmological model parameters we fitted the power law index and its first derivative with respect to the redshift (thus allowing for mass density profile evolution). It turned out that the best fitted $γ$ parameters are in agreement with each other irrespective of the cosmological model considered. This demonstrates that galactic strong lensing systems may provide a complementary probe to test the properties of dark energy. Fits for cosmological model parameters which we obtained are in agreement with alternative studies performed by the others. Because standard rulers and standard candles have different parameter degeneracies, combination of standard rulers and standard candles gives much more restrictive results for cosmological parameters. At last, we attempted at model selection based on information theoretic criteria (AIC and BIC). Our results support the claim, that cosmological constant model is still the best one and there is no (at least statistical) reason to prefer any other more complex model.

astro-ph.CO↗

arXiv2015

Strongly lensed gravitational waves from intrinsically faint double compact binaries - prediction for the Einstein Telescope

With a fantastic sensitivity improving significantly over the advanced GW detectors, Einstein Telescope (ET) will be able to observe hundreds of thousand inspiralling double compact objects per year. By virtue of gravitational lensing effect, intrinsically unobservable faint sources can be observed by ET due to the magnification by intervening galaxies. We explore the possibility of observing such faint sources amplified by strong gravitational lensing. Following our previous work, we use the merger rates of DCO (NS-NS,BH-NS,BH-BH systems) as calculated by Dominik et al.(2013). It turns out that tens to hundreds of such (lensed) extra events will be registered by ET. This will strongly broaden the ET's distance reach for signals from such coalescences to the redshift range z=2 - 8. However, with respect to the full inspiral event catalog this magnification bias is at the level of 0.001 and should not affect much cosmological inferences.

astro-ph.HE↗

arXiv2015

Cosmology with Strong Lensing Systems

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: $w(z) = w_0 + w_1 \frac{z}{1+z}$. 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 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.

astro-ph.CO↗

arXiv2015

Is there evidence for dark energy evolution?

Recently, Sahni, Shafielo o & Starobinsky (2014) combined two independent measurements of $H(z)$ from BAO data with the value of the Hubble constant $H_0 = H(z=0)$, in order to test the cosmological constant hypothesis by means of an improved version of the $Om$ diagnostic. Their result indicated a considerable tension between observations and predictions of the $Λ$CDM model. However, such strong conclusion was based only on three measurements of $H(z)$. This motivated us to repeat similar work on a larger sample. By using a comprehensive data set of 29 $H(z)$, we find that discrepancy indeed exists. Even though the value of $Ω_{m,0} h^2$ inferred from $Omh^2$ diagnostic depends on the way one chooses to make a summary statistics (weighted mean or the median), the persisting discrepancy supports the claims of Sahni, Shafielo o & Starobinsky (2014) that $Λ$CDM model may not be the best description of our Universe.

astro-ph.CO↗

arXiv2015

Exploring the properties of milliarcsecond radio sources

Cosmological applications of the "redshift - angular size" test require knowledge of the linear size of the "standard rod" used. In this paper, we study the properties of a large sample of 140 milliarcsecond compact radio sources with flux densities measured at 6 cm and 20 cm, compiled by Gurvits et al.(1999). Using the best-fitted cosmological parameters given by Planck/WMAP9 observations, we investigate the characteristic length $l_m$ as well as its dependence on the source luminosity $L$ and redshift $l_m=l L^β(1+z)^n$. For the full sample, measurements of the angular size $θ$ provide a tight constraint on the linear size parameters. We find that cosmological evolution of the linear size is small ($|n|\simeq 10^{-2}$) and consistent with previous analysis. However, a substantial evolution of linear sizes with luminosity is still required ($β\simeq 0.17$). Furthermore, similar analysis done on sub-samples defined by different source optical counterparts and different redshift ranges, seems to support the scheme of treating radio galaxies and quasars with distinct strategies. Finally, a cosmological-model-independent method is discussed to probe the properties of angular size of milliarcsecond radio quasars. Using the corrected redshift - angular size relation for quasar sample, we obtained a value of the matter density parameter, $Ω_m=0.292^{+0.065}_{-0.090}$, in the spatially flat $Λ$CDM cosmology.

astro-ph.CO↗

arXiv2014

Strong gravitational lensing of gravitational waves from double compact binaries - perspectives for the Einstein Telescope

Gravitational wave (GW) experiments are entering their advanced stage which should 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. 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. by using {\tt 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.

astro-ph.HE↗

arXiv2013

Strong gravitational lensing of gravitational waves in Einstein Telescope

Gravitational wave experiments have entered a new stage which gets us closer to the opening a new observational window on the Universe. In particular, the Einstein Telescope (ET) is designed to have a fantastic sensitivity that will provide with tens or hundreds of thousand NS-NS inspiral events per year up to the redshift z = 2. Some of such events should be gravitationally lensed by intervening galaxies. We explore the prospects of observing gravitationally lensed inspiral NS-NS events in the Einstein telescope. Being conservative we consider the lens population of elliptical galaxies. It turns out that depending on the local insipral rate ET should detect from one per decade detection in the pessimistic case to a tens of detections per year for the most optimistic case. The detection of gravitationally lensed source in gravitational wave detectors would be an invaluable source of information con- cerning cosmography, complementary to standard ones (like supernovae or BAO) independent of the local cosmic distance ladder calibrations.

astro-ph.CO↗