Search

Motivated by the recent study about the extended uncertainty principle (EUP) black holes, we present in this study its extension called the generalized extended uncertainty principle (GEUP) black holes. In particular, we investigated the GEUP effects on astrophysical and quantum black holes. First, we derive the expression for the shadow radius to investigate its behavior as perceived by a static observer located near and far from the black hole. Constraints to the large fundamental length scale, L*, up to two standard deviations level were also found using the Event Horizont Telescope (EHT) data: for black hole Sgr. A*, L*=5.716×1010 m, while for M87* black hole, L*=3.264×1013 m. Under the GEUP effect, the value of the shadow radius behaves the same way as in the Schwarzschild case due to a static observer, and the effect only emerges if the mass, M, of the black hole is around the order of magnitude of L* (or the Planck length, lPl). In addition, the GEUP effect increases the shadow radius for astrophysical black holes, but the reverse happens for quantum black holes. We also explored GEUP effects to the weak and strong deflection angles as an alternative analysis. For both realms, a time-like particle gives a higher value for the weak deflection angle. Similar to the shadow, the deviation is seen when the values of L* and M are close. The strong deflection angle gives more sensitivity to GEUP deviation at smaller masses in the astrophysical scenario. However, the weak deflection angle is a better probe in the micro world.

We investigate the blue and optical rest-frame sizes (lambda~2300A-4000A) of three compact star-forming regions in a galaxy at z=4 strongly lensed (x30, x45, x100) by the Hubble Frontier Field galaxy cluster A2744 using GLASS-ERS JWST/NIRISS imaging at 1.15um, 1.50mu and 2.0mu with PSF < 0.1". In particular, the Balmer break is probed in detail for all multiply-imaged sources of the system. With ages of a few tens of Myr, stellar masses in the range (0.7-4.0) x 10^6 Msun and optical/ultraviolet effective radii spanning the interval 3 < R_eff < 20 pc, such objects are currently the highest redshift (spectroscopically-confirmed) gravitationally-bound young massive star clusters (YMCs), with stellar mass surface densities resembling those of local globular clusters. Optical (4000A, JWST-based) and ultraviolet (1600A, HST-based) sizes are fully compatible. The contribution to the ultraviolet underlying continuum emission (1600A) is ~30%, which decreases by a factor of two in the optical for two of the YMCs (~4000A rest-frame), reflecting the young ages (, 10 pages, 4 figures, 1 table. Submitted to ApJL

Full list of authors: Welch, Brian; Coe, Dan; Zackrisson, Erik; de Mink, S. E.; Ravindranath, Swara; Anderson, Jay; Brammer, Gabriel; Bradley, Larry; Yoon, Jinmi; Kelly, Patrick; Diego, Jose M.; Windhorst, Rogier; Zitrin, Adi; Dimauro, Paola; Jimenez-Teja, Yolanda; Abdurro'uf; Nonino, Mario; Acebron, Ana; Andrade-Santos, Felipe; Avila, Roberto J.; Bayliss, Matthew B.; Benitez, Alex; Broadhurst, Tom; Bhatawdekar, Rachana; Bradac, Marusa; Caminha, Gabriel B.; Chen, Wenlei; Eldridge, Jan; Farag, Ebraheem; Florian, Michael; Frye, Brenda; Fujimoto, Seiji; Gomez, Sebastian; Henry, Alaina; Hsiao, Tiger Y-Y; Hutchison, Taylor A.; James, Bethan L.; Joyce, Meridith; Jung, Intae; Khullar, Gourav; Larson, Rebecca L.; Mahler, Guillaume; Mandelker, Nir; McCandliss, Stephan; Morishita, Takahiro; Newshore, Rosa; Norman, Colin; O'Connor, Kyle; Oesch, Pascal A.; Oguri, Masamune; Ouchi, Masami; Postman, Marc; Rigby, Jane R.; Ryan, Russell E., Jr.; Sharma, Soniya; Sharon, Keren; Strait, Victoria; Strolger, Louis-Gregory; Timmes, F. X.; Toft, Sune; Trenti, Michele; Vanzella, Eros; Vikaeus, Anton.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., The gravitationally lensed star WHL 0137–LS, nicknamed Earendel, was identified with a photometric redshift zphot = 6.2 ± 0.1 based on images taken with the Hubble Space Telescope. Here we present James Webb Space Telescope (JWST) Near Infrared Camera images of Earendel in eight filters spanning 0.8–5.0 μm. In these higher-resolution images, Earendel remains a single unresolved point source on the lensing critical curve, increasing the lower limit on the lensing magnification to μ > 4000 and restricting the source plane radius further to r < 0.02 pc, or ∼4000 au. These new observations strengthen the conclusion that Earendel is best explained by an individual star or multiple star system and support the previous photometric redshift estimate. Fitting grids of stellar spectra to our photometry yields a stellar temperature of Teff ≃ 13,000–16,000 K, assuming the light is dominated by a single star. The delensed bolometric luminosity in this case ranges from $\mathrm{log}(L)=5.8$ to 6.6 L⊙, which is in the range where one expects luminous blue variable stars. Follow-up observations, including JWST NIRSpec scheduled for late 2022, are needed to further unravel the nature of this object, which presents a unique opportunity to study massive stars in the first billion years of the universe. © 2022. The Author(s). Published by the American Astronomical Society., E.Z. acknowledges support from the Swedish National Space Board. M.B. acknowledges support from the Slovenian national research agency ARRS through grant N1-0238. A.Z. acknowledges support by grant No. 2020750 from the United States–Israel Binational Science Foundation (BSF) and grant No. 2109066 from the United States National Science Foundation (NSF) and by the Ministry of Science & Technology, Israel. M.T. acknowledges support by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) through project No. CE170100013. The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant No. 140. J.M.D. acknowledges the support of projects PGC2018-101814-B-100 and MDM-2017-0765. Y.J.-T. acknowledges financial support from the European Union's Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant agreement No. 898633, the MSCA IF Extensions Program of the Spanish National Research Council (CSIC), and the State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). P.A.O. acknowledges support by the Swiss National Science Foundation through project grant 200020_207349.

This work is devoted to the analysis of photon surfaces and photon regions in the stationary Plebanski–Demianski space–time, including black holes, naked singularities, and wormholes, with rotation, the electric or magnetic charge, the NUT parameter, the acceleration parameter, and the cosmological constant taken into account. We construct a theory of partially umbilic hypersurfaces, which allows us to describe the photon structure of space–time without resorting to the analysis of geodesic equations. We completely classify photon surfaces for various values of the parameters, including critical ones at which a qualitative change in the photon structure occurs. The results are visualized in the form of diagrams, which allows compactly presenting the information needed to understand strong gravitational lensing and gravitational shadows.

The invariance of the speed of light in the distant universe has profound significance for fundamental physics. In this paper, we propose a new model-independent method to test the invariance of the speed of light $c$ at different redshifts by combining the strong gravitational lensing (SGL) systems and the observations of type-Ia supernovae (SNe Ia). All the quantities used to test the deviation of $c$ come from the direct observations, and the absolute magnitudes of SNe Ia need not to be calibrated. Our results show that the speed of light in the distant universe is no obvious deviation from the constant value $c_0$ within the uncertainty based on current observations. Moreover, we conclude that the currently compiled SGL and SNe Ia Pantheon samples may achieve much higher precision $\Delta c/c\sim10^{-2}$ for the deviation of $c$ than all previously considered approaches. The forthcoming data from the Legacy Survey of Space and Time and Wide-Field InfraRed Space Telescope will achieve more stringent testing for deviation of the SOL (at the level of $\Delta c/c \sim10^{-3}$) by using our model-independent method. Finally, we discuss the potential ways in which our technique might be improved, focusing on the treatment of possible sources of systematic uncertainties., Comment: 9 pages, 5 figures, accepted for publication in MNRAS

We present our lens mass model of SMACS J0723, the first strong gravitational lens observed by the James Webb Space Telescope (JWST). We use data from the Hubble Space Telescope and Multi Unit Spectroscopic Explorer (MUSE) to build our 'pre-JWST' lens model, and refine it with newly available JWST near-infrared imaging in our JWST model. To reproduce the positions of all multiple lensed images with good accuracy, the adopted mass parameterization consists of one cluster-scale component, accounting mainly for the dark matter distribution, the galaxy cluster members and an external shear component. The pre-JWST model has, as constraints, 19 multiple images from six background sources, of which four have secure spectroscopic redshift measurements from this work. The JWST model has more than twice the number of constraints, 30 additional multiple images from another eleven lensed sources. Both models can reproduce very well the multiple image positions with a $\delta_{rms}$ of $0.39''$ and $0.51''$, for the pre-JWST and JWST models, respectively. The total mass estimates within a radius of 128~kpc (~ the Einstein radius) are $7.9_{-0.2}^{+0.3}\times 10^{13}\rm M_{\odot}$ and $8.7_{-0.2}^{+0.2}\times 10^{13}\rm M_{\odot}$, for the pre-JWST and JWST models, respectively. We predict with our mass models the redshifts of the newly detected JWST sources, which are crucial information for systems without spectroscopic measurements for further studies and follow-up observations. Interestingly, one family detected with JWST is found to be at a very high redshift, $z>7.5$ (68% confidence level) and with one image having lensing magnification of $|\mu|=9.5_{-0.8}^{+0.9}$, making it an interesting case for future studies. The lens models, including magnification maps and redshifts estimated from the model are made publicly available, along with the full spectroscopic redshift catalogue from MUSE., Comment: 5 pages, 2 figures, 1 table, plus appendix. Published in A&A Letters. Lens model and redshift catalogue available at: http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/666/L9

Due to the finite amount of observational data, the best-fit parameters corresponding to the reconstructed cluster mass have uncertainties. In turn, these uncertainties affect the inferences made from these mass models. Following our earlier work, we have studied the effect of such uncertainties on the singularity maps in simulated and actual galaxy clusters. The mass models for both simulated and real clusters have been constructed using grale. The final best-fit mass models created using grale give the simplest singularity maps and a lower limit on the number of point singularities that a lens has to offer. The simple nature of these singularity maps also puts a lower limit on the number of three image (tangential and radial) arcs that a cluster lens has. Hence, we estimate the number of galaxy sources giving rise to the three image arcs, which can be observed with the James Webb Space Telescope (JWST). We find that we expect to observe at least 20-30 tangential and 5-10 radial three-image arcs in the Hubble Frontier Fields cluster lenses with the JWST., Comment: 15 pages, 7 figures. Accepted in MNRAS

A new method based on large-scale structure observations is proposed to probe a possible time variation of the fine-structure constant ($\alpha$). Our analyses are based on time-delay of Strong Gravitational Lensing and Type Ia Supernovae observations. By considering a class of runaway dilaton models, where the cosmological evolution of the fine-structure constant is given by $\frac{\Delta \alpha}{\alpha} \approx -\gamma \ln{(1+z)}$, we obtain limits on the physical properties parameter of the model ($\gamma$) at the level $10^{-2}$ ($1\sigma$). Although our limits are less restrictive than those obtained by quasar spectroscopy, the approach presented here provides new bounds on the possibility of $\frac{\Delta \alpha}{\alpha} \neq 0$ at a different range of redshifts., Comment: 9 pages, 4 figures and 1 table - Accepted in The European Physical Journal C

Here we consider accelerating and rotating charged Plebanski-Demianski (PD) class of black hole metric as a particle accelerator. We obtain the geodesic motions (timelike, null and spacelike) of particles in a non-equatorial plane around the PD black hole. We find the effective potential, energy, angular momentum, impact parameters, and discuss the circular orbit. We study the center of mass energy of two neutral particles falling from infinity to near the non-extremal horizons (event and Cauchy horizons), extremal horizon, accelerating horizons, and near the center of the PD black hole. Also, we study the collision of a particle and a massless photon. Then we find the center of mass energy due to the collision of two massless photons in the PD black hole background. We compute the redshift and blueshift of the emitted photons by massive particles while light signal travels along null geodesics towards the observer located far away from the source. We study the Penrose process, which occurs within the ergosphere, and examines the particle’s motion with its implications. Here, we analyze the PD black hole shadow’s apparent shape, which forms far away from the black hole. We study the possible visibility of the PD black hole through photon’s shadow and energy emission rate. We also investigate the effect on the shadow of the PD black hole in plasma for a distant observer. We study the strong gravitational lensing by PD black hole. Finally, we analyze the deflection angle, lens equation, position, magnification, Einstein ring and observables by taking the supermassive PD black hole in the Galaxy’s center.

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM, Gravitationally lensed supernovae (LSNe) are important probes of cosmic expansion, but they remain rare and difficult to find. Current cosmic surveys likely contain 5-10 LSNe in total while next-generation experiments are expected to contain several hundred to a few thousand of these systems. We search for these systems in observed Dark Energy Survey (DES) five year SN fields—10 3 sq. deg. regions of sky imaged in the griz bands approximately every six nights over five years. To perform the search, we utilize the DeepZipper approach: a multi-branch deep learning architecture trained on image-level simulations of LSNe that simultaneously learns spatial and temporal relationships from time series of images. We find that our method obtains an LSN recall of 61.13% and a false-positive rate of 0.02% on the DES SN field data. DeepZipper selected 2245 candidates from a magnitude-limited (m i < 22.5) catalog of 3,459,186 systems. We employ human visual inspection to review systems selected by the network and find three candidate LSNe in the DES SN fields, The DES participants from Spanish institutions are partially supported by MICINN under grants ESP2017-89838, PGC2018-094773, PGC2018-102021, SEV-2016-0588, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union.

The cosmic distance duality relation (CDDR), eta(z)=(1+z)^2 d_A(z)/d_L(z)=1, is one of the most fundamental and crucial formulae in cosmology. This relation couples the luminosity and angular diameter distances, two of the most often used measures of structure in the Universe. We here propose a new model-independent method to test this relation, using strong gravitational lensing (SGL) and the high-redshift quasar Hubble diagram reconstructed with a Bezier parametric fit. We carry out this test without pre-assuming a zero spatial curvature, adopting instead the value Omega_K=0.001 +/- 0.002 optimized by Planck in order to improve the reliability of our result. We parametrize the CDDR using eta(z)=1 + eta_0 z, 1 + eta_1 z + eta_2 z^2 and 1 + eta_3 z/(1+z), and consider both the SIS and non-SIS lens models for the strong lensing. Our best fit results are: eta_0=-0.021^{+0.068}_{-0.048}, eta_1=-0.404^{+0.123}_{-0.090}, eta_2=0.106^{+0.028}_{-0.034}, and eta_3=-0.507^{+0.193}_{-0.133} for the SIS model, and eta_0=-0.109^{+0.044}_{-0.031} for the non-SIS model. The measured eta(z), based on the Planck parameter Omega_K, is essentially consistent with the value (=1) expected if the CDDR were fully respected. For the sake of comparison, we also carry out the test for other values of Omega_K, but find that deviations of spatial flatness beyond the Planck optimization are in even greater tension with the CDDR. Future measurements of SGL may improve the statistics and alter this result but, as of now, we conclude that the CDDR favours a flat Universe., Comment: 10 pages, 9 figures, 1 table; accepted for publication in Monthly Notices of the Royal Astronomical Society

We research the strong gravitational lensing for the quantum-modified Schwarzschild black hole which is derived from quantum Raychaudhuri equation. With the increase of quantum Raychaudhuri equation parameter η, we find that the distance between the black hole and the light passing by it becomes smaller; the deflection angle gets larger; the magnification of relativistic images is more similar; all of the relativistic images move towards the black hole while the images are farther to each other. These results, as we expect, will degenerate to the case of Schwarzschild black hole when $\eta \rightarrow 0$ .

DES Collaboration: O’Donnell et al., We report the combined results of eight searches for strong gravitational lens systems in the full 5000 square degrees of Dark Energy Survey (DES) observations. The observations accumulated by the end of the third observing season fully covered the DES footprint in five filters (grizY), with an i-band limiting magnitude (at 10σ) of 23.44. In four searches, a list of potential candidates was identified using a color and magnitude selection from the object catalogs created from the first three observing seasons. Three other searches were conducted at the locations of previously identified galaxy clusters. Cutout images of potential candidates were then visually scanned using an object viewer. An additional set of candidates came from a data-quality check of a subset of the color–coadd tiles created from the full DES six-season data set. A short list of the most promising strong-lens candidates was then numerically ranked according to whether or not we judged them to be bona fide strong gravitational lens systems. These searches discovered a diverse set of 247 strong-lens candidate systems, of which 81 are identified for the first time. We provide the coordinates, magnitudes, and photometric properties of the lens and source objects, and an estimate of the Einstein radius for 81 new systems and 166 previously reported systems. This catalog will be of use for selecting interesting systems for detailed follow up, studies of galaxy cluster and group mass profiles, as well as a training/validation set for automated strong-lens searches., Funding for the DES projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at The Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência, Tecnologia e Inovação, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenössische Technische Hochschule (ETH) Zürich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ciències de l'Espai (IEEC/CSIC), the Institut de Física d'Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universität München and the associated Excellence Cluster Universe, the University of Michigan, NSF's NOIRLab, the University of Nottingham, The Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, Texas A&M University, and the OzDES Membership Consortium. Based in part on observations at Cerro Tololo Inter-American Observatory at NSF's NOIRLab (NOIRLab Prop. ID 2012B-0001; PI: J. Frieman), which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. The DES data management system is supported by the National Science Foundation under grant nos. AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MICINN under grants ESP2017-89838, PGC2018-094773, PGC2018-102021, SEV-2016-0588, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Program (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478. We acknowledge support from the Brazilian Instituto Nacional de Ciência e Tecnologia (INCT) do e-Universo (CNPq grant 465376/2014-2).

We investigate the strong-lensing cluster Abell 370 (A370) using a wide Integral Field Unit (IFU) spectroscopic mosaic from the Multi-Unit Spectroscopic Explorer (MUSE). IFU spectroscopy provides significant insight into the structure and mass content of galaxy clusters, yet IFU-based cluster studies focus almost exclusively on the central Einstein-radius region. Covering over 14 arcmin$^2$, the new MUSE mosaic extends significantly beyond the A370 Einstein radius, providing, for the first time, a detailed look at the cluster outskirts. Combining these data with wide-field, multi-band Hubble Space Telescope (HST) imaging from the BUFFALO project, we analyse the distribution of objects within the cluster and along the line of sight. Identifying 416 cluster galaxies, we use kinematics to trace the radial mass profile of the halo, providing a mass estimate independent from the lens model. We also measure radially-averaged properties of the cluster members, tracking their evolution as a function of infall. Thanks to the high spatial resolution of our data, we identify six cluster members acting as galaxy-galaxy lenses, which constrain localized mass distributions beyond the Einstein radius. Finally, taking advantage of MUSE's 3D capabilities, we detect and analyse multiple spatially extended overdensities outside of the cluster that influence lensing-derived halo mass estimates. We stress that much of this work is only possible thanks to the robust, extended IFU coverage, highlighting its importance even in less optically dense cluster regions. Overall, this work showcases the power of combining HST+MUSE, and serves as the initial step towards a larger and wider program targeting several clusters., 20 pages, 12 figures, 3 tables (including 1 in an appendix). Accepted in MNRAS. Data Release products available at https://astro.dur.ac.uk/~hbpn39/pilot-wings.html

Quantum gravity (QG) remains elusive despite almost century-long efforts to combine general relativity and quantum mechanics. All the approaches triggered and powered by purely theoretical considerations eventually failed with a prevailing feeling of a complete lack of guidance from the experimental side. Currently, however, this circumstance is beginning to change considerably. We have entered the era of multi-messenger astronomy. The electromagnetic window to the universe—so far the only one—has been tremendously enlarged in the energy range beyond gamma rays up to ultra-high-energy photons and has been complemented by other messengers: high-energy cosmic rays, cosmic neutrinos, and gravitational waves (GWs). This has created a unique environment in which to observationally constrain various phenomenological QG effects. In this paper, we focus on the LIV phenomenology manifested as energy-dependent time-of-flight delays and strong lensing time delays. We review results regarding time-of-flight delays obtained with GRBs. We also recall the idea of energy-dependent lensing time delays, which allow one to constrain LIV models independently of the intrinsic time delay. Lastly, we show how strongly a gravitationally lensed GW signal would place interesting constraints on the LIV.

We assemble a large comprehensive sample of 2534 z~2, 3, 4, 5, 6, 7, 8, and 9 galaxies lensed by the six clusters from the Hubble Frontier Fields (HFF) program. Making use of the availability of multiple independent magnification models for each of the HFF clusters and alternatively treating one of the models as the "truth," we show that the median magnification factors from the v4 parametric models are typically reliable to values of 30 to 50, and in one case to 100. Using the median magnification factor from the latest v4 models, we estimate the UV luminosities of the 2534 lensed z~2-9 galaxies, finding sources as faint as -12.4 mag at z~3 and -12.9 mag at z~7. We explicitly demonstrate the power of the surface density-magnification relations Sigma(z) vs. mu in the HFF clusters to constrain both distant galaxy properties and cluster lensing properties. Based on the Sigma(z) vs. mu relations, we show that the median magnification estimates from existing public models must be reliable predictors of the true magnification mu to mu, 22 pages, 13 figures, 6 tables, accepted for publication in the Astrophysical Journal, updated to be consistent with the proofs

We present new determinations of the rest-UV luminosity functions (LFs) at z = 2–9 to extremely low luminosities (>−14 mag) from a sample of >2500 lensed galaxies found behind the Hubble Frontier Fields (HFF) clusters. For the first time, we present faint-end slope results from lensed samples that are fully consistent with blank-field results over the redshift range z = 2–9, while reaching to much lower luminosities than possible from the blank-field studies. Combining the deep lensed sample with the large blank-field samples allows us to set tight constraints on the faint-end slope α of the z = 2–9 UV LFs and its evolution. We find a smooth flattening in α from −2.28 ± 0.10 (z = 9) to −1.53 ± 0.03 (z = 2) with cosmic time (dα/dz = −0.11 ± 0.01), fully consistent with dark matter halo buildup. We utilize these new results to present new measurements of the evolution in the UV luminosity density ρUV brighter than −13 mag from z ∼ 9 to z ∼ 2. Accounting for the star formation rate (SFR) densities to faint luminosities implied by our LF results, we find that unobscured star formation dominates the SFR density at z ≳ 4, with obscured star formation dominant thereafter. Having shown we can quantify the faint-end slope α of the LF accurately with our lensed HFF samples, we also quantify the apparent curvature in the shape of the UV LF through a curvature parameter δ. The constraints on the curvature δ strongly rule out the presence of a turn-over brighter than −13.1 mag at z ∼ 3, −14.3 mag at z ∼ 6, and −15.5 mag at all other redshifts between z ∼ 9 and z ∼ 2., This lens modeling was partially funded by the HST Frontier Fields program conducted by STScI. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. The lens models were obtained from the Mikulski Archive for Space Telescopes (MAST). The authors acknowledge the support of NASA grants HST-AR-13252, HST-GO-13872, HST-GO-13792, HST-AR-15027, HST-GO-16037, and NWO grants 600.065.140.11N211 (vrij competitie) and TOP grant TOP1.16.057. R.S.E. acknowledges financial support from European Research Council Advanced grant FP7/669253.

Analyzing gravitationally lensed objects enables a wide range of physical and cosmological applications, such as probing the dark matter content in galaxies and clusters or measuring the Universe's expansion rate. The precision of these applications can be improved drastically with a larger number of lenses. For this reason, finding new strong gravitational lensing systems is crucial. Traditionally, gravitational lenses were found with meticulous visual inspections of imaging datasets. However, the next generation of large-scale imaging surveys will produce such a large amount of data that visual inspection will be unpractical, thus motivating the development of efficient automated detection methods to handle large datasets and improve the accuracy of the different applications. The main topic of this thesis is to develop and improve our lens finding algorithms and to study new strong gravitational lenses in large-scale imaging surveys. The first part of this thesis has been to develop a new tool that allows the production of lens simulations. Deep learning algorithms, particularly convolutional neural networks (CNNs), have recently proven their efficiency in detecting lensing systems. In particular, CNNs can be adapted to find a large variety of lenses at once, making them especially suited to be part of automated detection pipelines. However, convolutional neural networks usually require large sets of images to be trained. Unfortunately, the number of known lenses is at this time too low to constitute a sufficient training set. For this reason, robust and flexible tools to simulate realistic lenses have to be developed to generate training sets. Lens simulations must, however, be as realistic as possible to avoid biases. In this thesis, we propose a simulation tool that enables the production of large sets of realistic lens simulations. This tool has been designed to be flexible and, thus, enables the production of lens simulations with different types of deflectors for any imaging survey. The second part consists in separating the light of a lensed source from the foreground object. Indeed, in some cases, the lens features are hidden by the light of the foreground object and deblending might help to identify the lenses help identify lenses with small image separation and enables photometric redshift measurements or the initialization of lens models. This thesis presents a new data-driven method for deblending strong gravitational lenses based on neural networks. Finally, due to the low occurrence rate of strong lensing, the false positive rate of detection algorithms is still a significant challenge. Therefore, we present different tools that enable the inspection of large sets of candidate images. In addition, evaluating the quality of lens candidates is somewhat subjective since the features that define a lens may differ for different experts. Therefore, we propose a set of grading guidelines that can be used for the subsequent ground-based imaging lens searches in this thesis. The CNN-based classifier, the deblending algorithm, and the simulation and visualization tools are part of an automated lens-finding pipeline. This flexible pipeline can be adapted to future large-scale surveys. We discuss in this thesis its first applications to the Canada-France Imaging Survey and the Dark Energy Survey, which led to the discovery of 133 and 403 high-quality lens candidates, respectively.

Probing statistical distribution of the neutral hydrogen (\HI) using the redshifted 21-cm hyperfine-transition spectral line holds the key to understand the formation and evolution of the matter density in the universe. The two-point statistics of the \HI distribution can be estimated by measuring the power spectrum of the redshifted 21-cm signal using visibility correlation. A major challenge in this regard is that the expected signal is weak compared to the foreground contribution from the Galactic synchrotron emission and extragalactic point sources in the observing frequencies. In this work, we investigate the possibility of detecting the power spectrum of the redshifted 21-cm signal by using strong gravitational lensing of the galaxy clusters. This method has the advantage that it only enhances the \HI signal and not the diffuse galactic foreground. Based on four simple models of the cluster potentials we show that the strong lenses at relatively lower redshifts with more than one dark matter halo significantly enhances the 21-cm signal from the post reionization era. We discuss the merits and demerits of the method and the future studies required for further investigations., 9 pages, 6 figures

Many distant objects can only be detected, or become more scientifically valuable, if they have been highly magnified by strong gravitational lensing. We use EAGLE and BAHAMAS, two recent cosmological hydrodynamical simulations, to predict the probability distribution for both the lens mass and lens redshift when point sources are highly magnified by gravitational lensing. For sources at a redshift of two, we find the distribution of lens redshifts to be broad, peaking at z=0.6. The contribution of different lens masses is also fairly broad, with most high-magnification lensing due to lenses with halo masses between 10^12 and 10^14 solar masses. Lower mass haloes are inefficient lenses, while more massive haloes are rare. We find that a simple model in which all haloes have singular isothermal sphere density profiles can approximately reproduce the simulation predictions, although such a model over-predicts the importance of haloes with mass, 15 pages, 5 figures, updated to match MNRAS version

With the spatial resolution of the Atacama Large Millimetre Array (ALMA), dusty galaxies in the distant Universe typically appear as single, compact blobs of dust emission, with a median half-light radius, $\approx$ 1 kpc. Occasionally, strong gravitational lensing by foreground galaxies or galaxy clusters has probed spatial scales 1-2 orders of magnitude smaller, often revealing late-stage mergers, sometimes with tantalising hints of sub-structure. One lensed galaxy in particular, the Cosmic Eyelash at $z=$ 2.3, has been cited extensively as an example of where the interstellar medium exhibits obvious, pronounced clumps, on a spatial scale of $\approx$ 100 pc. Seven orders of magnitude more luminous than giant molecular clouds in the local Universe, these features are presented as circumstantial evidence that the blue clumps observed in many $z\sim$ 2-3 galaxies are important sites of ongoing star formation, with significant masses of gas and stars. Here, we present data from ALMA which reveal that the dust continuum of the Cosmic Eyelash is in fact smooth and can be reproduced using two S\'ersic profiles with effective radii, 1.2 and 4.4 kpc, with no evidence of significant star-forming clumps down to a spatial scale of $\approx$ 80 pc and a star-formation rate of $, Comment: 5 pages; 3 figures; in press as a Letter to MNRAS

Recent observational evidence reveals the existence of black holes in the galaxy. Using strong field lensing effect, we find out the expressions of the radius of the photon sphere, the deflection angle, the separation between the first and the other images, the ratio between the flux of the first image as well as the flux coming from all the other images for dilaton–axion black holes and compare the results with Reissner–Nordstrom black holes. We also investigate the variations of primary and secondary image positions as well as their magnifications with respect to the source position for this kind of black holes.

We study the time delay between two relativistic images due to strong gravitational lensing of the light rays caused by the Kerr and Kerr-Newman black holes. The trajectories of the light rays are restricted on the equatorial plane. Using the known form of the deflection angle in the strong deflection limit (SDL) allows us to analytically develop the formalism for the travel time of the light from the distant source winding around the black hole several times and reaching the observer. We find that the black hole with higher mass or with spin of the extreme black hole potentially have higher time delay. The effect of the charge of the black hole enhances the time delay between the images lying on the opposite side of the optical axis resulting from the light rays when one light ray is in the direct orbit and the other is in the retrograde orbit. In contrary, when both light rays travel along either direct or retrograde orbits giving the images on the same side of the optical axis, the charge effect reduces the time delay between them. We then examine the time delay observations due to the galactic and supermassive black holes respectively, 33 pages, 5 figures. Revised version to appear in Physical Review D. arXiv admin note: text overlap with arXiv:2101.09008

We investigate the strong gravitational lensing on equatorial plane as well as quasi-equatorial plane by the Kerr–Newman-NUT-Quintessence (KNNQ) black hole (BH) with the equation of state (EoS) parameter of the quintessence [Formula: see text] and the quintessence density [Formula: see text]. Our results show that the strong gravitational lensing in the KNNQ black hole space–time has some distinct behaviors from those in the backgrounds of the four dimension Kerr black hole. Also, we investigate the strong gravitational lensing on equatorial plane as well as quasi-equatorial plane by the KNNQ BH with the effects of Nut charge, spin parameter and quintessence parameter. First, we calculate the null geodesic equations using the Hamilton–Jacobi separation method. Then we investigate the equatorial lensing by KNNQ black hole. We obtain the deflection angle and deflection coefficients in the equatorial plane, which is affected by EoS parameter of the quintessence [Formula: see text], quintessence density [Formula: see text], Nut parameter [Formula: see text], spin parameter [Formula: see text] and quintessence parameter [Formula: see text] [Formula: see text]. Next, we discuss the lens equation and the observables in the equatorial plane. Finally, we investigate gravitational lensing by the KNNQ black hole in the quasi-equatorial plane. In this work, the quintessence density [Formula: see text], the EoS parameter of the quintessence [Formula: see text], Nut parameter [Formula: see text], spin parameter [Formula: see text] and quintessence parameter [Formula: see text] [Formula: see text] have significant effects on the strong gravitational lensing both in equatorial plane as well as quasi-equatorial plane.

In order to probe a possible time variation of the fine-structure constant ($\alpha$), we propose a new method based on Strong Gravitational Lensing and Type Ia Supernovae observations. By considering a class of dilaton runaway models, where $\frac{\Delta \alpha}{\alpha}= - \gamma \ln{(1+z)}$, we obtain constraints on $\frac{\Delta \alpha}{\alpha}$ at the level $\gamma \approx 10^{-2}$ ($\gamma$ captures the physical properties of the model). Since the data set covers the redshift range $0.075 \leq z \leq 2.2649$, the constraints derived here provide independent bounds on a possible time variation of $\alpha$ at low, intermediate and high redshifts., Comment: 9 pages, 3 figures, 1 table - Accepted in The European Physical Journal C

Gravitational lensing is an important prediction of general relativity, providing both its test and a tool to detect faint but amplified sources and to measure masses of lenses. For some applications (e.g. testing the theory), a point source lensed by a point-like lens would be more advantageous. However, until now only one gravitationally lensed star has been resolved. The future telescopes will resolve very small lensing signatures for stars orbiting the supermassive black hole (SMBH) in the center of the Milky Way. The lensing signatures should however be easier to detect for background stars. We predict that ELT, TMT, and GMT will resolve the lensed images of around 100 (60) stars in the disk and 30 (20) stars in the bulge in the background of the SMBH, down to 28 (27) mag (Vega) limits at K-band, requiring 5 (1) hr of integration. In order to detect several such stars one needs the limit of at least 24 mag. With a decade-long monitoring one can also detect the rotation of the lensed images. The detection of elongated images will not be possible, because this would require a nearly perfect source-lens alignment. JWST will likely be limited by the confusion caused by stars near the Galactic center. The detection of such lensed images will provide a very clean test of general relativity, when combined with the SMBH mass measurement from orbital motions of stars, and accurate measurements of the SMBH properties, because both the source and the lens can be considered point-like., ApJ Letters, accepted; 9 pages, 4 figures, 1 table

We present GIGA-Lens: a gradient-informed, GPU-accelerated Bayesian framework for modeling strong gravitational lensing systems, implemented in TensorFlow and JAX. The three components, optimization using multi-start gradient descent, posterior covariance estimation with variational inference, and sampling via Hamiltonian Monte Carlo, all take advantage of gradient information through automatic differentiation and massive parallelization on graphics processing units (GPUs). We test our pipeline on a large set of simulated systems and demonstrate in detail its high level of performance. The average time to model a single system on four Nvidia A100 GPUs is 105 seconds. The robustness, speed, and scalability offered by this framework make it possible to model the large number of strong lenses found in current surveys and present a very promising prospect for the modeling of $\mathcal{O}(10^5)$ lensing systems expected to be discovered in the era of the Vera C. Rubin Observatory, Euclid, and the Nancy Grace Roman Space Telescope., Comment: 23 pages, 13 figures, 2 tables. Submitted to ApJ

lenstronomy is an Astropy-affiliated Python package for gravitational lensing simulations and analyses. lenstronomy was introduced by Birrer and Amara (2018) and is based on the linear basis set approach by Birrer et a. (2015). The user and developer base of lenstronomy has substantially grown since then, and the software has become an integral part of a wide range of recent analyses, such as measuring the Hubble constant with time-delay strong lensing or constraining the nature of dark matter from resolved and unresolved small scale lensing distortion statistics. The modular design has allowed the community to incorporate innovative new methods, as well as to develop enhanced software and wrappers with more specific aims on top of the lenstronomy API. Through community engagement and involvement, lenstronomy has become a foundation of an ecosystem of affiliated packages extending the original scope of the software and proving its robustness and applicability at the forefront of the strong gravitational lensing community in an open source and reproducible manner., Comment: published by JOSS. Software available at https://github.com/sibirrer/lenstronomy. Comments, issues and pull requests welcome!

Dark matter is an important part of cosmological matter, and gravitational lensing is a fundamental way to study the distribution of dark matter. Therefore, the gravitational lensing system is of great significance to the study of astrophysics. However, since strong gravitational lensing is extremely rare, the number of strong lensing candidate galaxies within the galaxy is also very large. To find these rare objects, we need to find them from at least tens of millions of images. The features based on the shallow structure are difficult to perfectly process these broad sense image data. In order to improve the efficiency and accuracy of recognition, a deep learning-based astronomical method for astronomical strong gravitational lensing systems is proposed, which first requests the classification of image data using label files. Next, data preprocessing is used for augmentation of targets in images, which provides more samples and more features can be learnt. After classification and preprocessing, the neural network is trained with the data, so as to facilitate the detection of strong lenses. By actual testing, the experiments show that the results of our method is 4.88% higher than Kapteyn Resnet and 7.5% higher than Manchester-SVM in model evaluation index AUC.

As we enter the era of large-scale imaging surveys with the upcoming telescopes such as the Large Synoptic Survey Telescope (LSST) and the Square Kilometre Array (SKA), it is envisaged that the number of known strong gravitational lensing systems will increase dramatically. However, these events are still very rare and require the efficient processing of millions of images. In order to tackle this image processing problem, we present machine learning techniques and apply them to the gravitational lens finding challenge. The convolutional neural networks (CNNs) presented here have been reimplemented within a new, modular, and extendable framework, Lens EXtrActor CaTania University of Malta (LEXACTUM). We report an area under the curve (AUC) of 0.9343 and 0.9870, and an execution time of 0.0061 and 0.0594 s per image, for the Space and Ground data sets, respectively, showing that the results obtained by CNNs are very competitive with conventional methods (such as visual inspection and arc finders) for detecting gravitational lenses., peer-reviewed

Strong gravitational lensing is a gravitational wave (GW) propagation effect that influences the inferred GW source parameters and the cosmological environment. Identifying strongly-lensed GW images is challenging as waveform amplitude magnification is degenerate with a shift in the source intrinsic mass and redshift. However, even in the geometric-optics limit, type II strongly-lensed images cannot be fully matched by type I (or unlensed) waveform templates, especially with large binary mass ratios and orbital inclination angles. We propose to use this mismatch to distinguish individual type II images. Using planned noise spectra of Cosmic Explorer, Einstein Telescope and LIGO Voyager, we show that a significant fraction of type II images can be distinguished from unlensed sources, given sufficient SNR ($\sim 30$). Incorporating models on GW source population and lens population, we predict that the yearly detection rate of lensed GW sources with detectable type II images is 172.2, 118.2 and 27.4 for CE, ET and LIGO Voyager, respectively. Among these detectable events, 33.1%, 7.3% and 0.22% will be distinguishable via their type II images with a log Bayes factor larger than 10. We conclude that such distinguishable events are likely to appear in the third-generation detector catalog; our strategy will significantly supplement existing strong lensing search strategies., Comment: 20 pages, 16 figures. Figures and some texts were modified without changes to the conclusion. Published In PRD

We consider a time-like geodesics in the background of rotating Einstein-Born-Infeld (EBI) black hole to examine the horizon and ergosphere structure. The effective potential that governs the particle's motion in the spacetime and the innermost stable circular orbits (ISCO) is also studied. A qualitative analysis is conducted to find the redshifted ultrahigh centre-of-mass (CM) energy as a result of a two-particle collision specifically near the horizon. The recent Event Horizon Telescope (EHT) triggered a surge of interest in strong gravitational lensing by black holes, which provide a new tool comparing the black hole lensing in general relativity and alternate gravity theories. Motivated by this, we also discussed both strong and weak-field gravitational lensing in the space-time discretely for a uniform plasma and a singular isothermal sphere. We calculated the light deflection coefficients $\bar{a}$ and $\bar{b}$ in the strong field limits, and their variance with the rotational parameter $a$ for different plasma frequency as well as in vacuum. For EBI black holes, we found that plasma's presence increases the photon sphere radius, the deflection angle, the deflection coefficients $\bar{a}$, $\bar{b}$, the angular positions and the angular separation between the relativistic images. It is also shown that with increasing spin the impact of plasma on a strong gravitational lensing becomes smaller as the spin parameter grows in the prograde orbit ($a>0$). For extreme black holes, the strong gravitational effects in the homogenous plasma are similar to those of in a vacuum. We investigate strong gravitational lensing effects by supermassive black holes Sgr A* and M87*..., 22 pages, 14 figures

The core mass of galaxy clusters is both an important anchor of the radial mass distribution profile and probe of structure formation. With thousands of strong lensing galaxy clusters being discovered by current and upcoming surveys, timely, efficient, and accurate core mass estimates are needed. We assess the results of two efficient methods to estimate the core mass of strong lensing clusters: the mass enclosed by the Einstein radius ($M_{corr}(

We investigate strong field gravitational lensing by rotating Simpson-Visser black hole, which has an additional parameter ($0\leq l/2M \leq1$), apart from mass ($M$) and rotation parameter ($a$). A rotating Simpson-Visser metric correspond to (i) a Schwarzschild metric for $l/2M=a/2M=0$ and $ M \neq 0 $, (ii) a Kerr metric for $l/2M=0$, $|a/2M|< 0.5$ and $ M \neq 0 $ (iii) a rotating regular black hole metric for $|a/2M|< 0.5$, $ M \neq 0 $ and $l/2M$ in the range $00.5$ and $l/2M\neq 0$. We find a decrease in the deflection angle $\alpha_D$ and also in the ratio of the flux of the first image and all other images $ r_{mag}$. On the other hand, angular position $\theta_{1}$ increases more slowly and photon sphere radius $x_{m}$ decreases more quickly, but angular separation $s$ increases more rapidly, and their behaviour is similar to that of the Kerr black hole. The formalism is applied to discuss the astrophysical consequences in the supermassive black holes and find that the rotating Simpson-Visser black holes can be distinguished from the Kerr black hole via gravitational lensing. The deviation of the lensing observables $\Delta\theta_1$ and $\Delta s$ of rotating Simpson Visser black holes from Kerr black hole for $0, Comment: 18 Pages, 11 Figures, 4 Tables, new section about non-equatorial lensing added, accepted for publication in JCAP

By comparing the dynamical and lensing masses of early-type lens galaxies, one can constrain both the cosmological parameters and the density profiles of galaxies. We explore the constraining power on cosmological parameters and the effect of the lens mass model in this method with 161 galaxy-scale strong lensing systems, which is currently the largest sample with both high resolution imaging and stellar dynamical data. We assume a power-law mass model for the lenses, and consider three different parameterizations for $\gamma$ (i.e., the slope of the total mass density profile) to include the effect of the dependence of $\gamma$ on redshift and surface mass density. When treating $\delta$ (i.e., the slope of the luminosity density profile) as a universal parameter for all lens galaxies, we find the limits on the cosmological parameter $\Omega_m$ are quite weak and biased, and also heavily dependent on the lens mass model in the scenarios of parameterizing $\gamma$ with three different forms. When treating $\delta$ as an observable for each lens, the unbiased estimate of $\Omega_m$ can be obtained only in the scenario of including the dependence of $\gamma$ on both the redshift and the surface mass density, that is $\Omega_m = 0.381^{+0.185}_{-0.154}$ at 68\% confidence level in the framework of a flat $\Lambda$CDM model. We conclude that the significant dependencies of $\gamma$ on both the redshift and the surface mass density, as well as the intrinsic scatter of $\delta$ among the lenses, need to be properly taken into account in this method., Comment: Accepted for publication in MNRAS; 17 pages, 5 figures, 2 tables

Recently, Rastall gravity is undergoing a significant surge in popularity. We obtain a power-law total mass-density profile for the inner region (within several effective radius) of early-type galaxies (ETGs) from the space-time structures which are described by the static spherically-symmetric solutions of Rastall gravity under the assumption of perfect fluid matter. We find that in the inner region of ETGs, the Rastall dimensionless parameter $\beta=\kappa\lambda$ determines the mass distribution. We then use 118 galaxy-galaxy strong gravitational lensing systems to constrain the Rastall dimensionless parameter $\beta$. We find that the mean value of $\beta$ for total 118 ETGs is $\beta=0.163\pm0.001$(68\% CL) with a minor intrinsic scatter of $\delta=0.020\pm 0.001$. Our work observationally illustrates the physical meaning of the Rastall dimensionless parameter in galaxy scale. From the Newtonian approximation of Rastall gravity, we also find that an absolute isothermal mass distribution for ETGs is not allowed in the framework of Rastall gravity., Comment: 6 pages, 1 figure. Accepted by MNRAS

Remarkable development of cosmology is benefited from the increasingly improved measurements of cosmic distances including absolute distances and relative distances. In recent years, however, the emerged cosmological tensions motivate us to explore the independent and precise late-universe probes. The two observational effects of strong gravitational lensing (SGL), the velocity dispersions of lens galaxies and the time delays between multiple images, can provide measurements of relative and absolute distances respectively, and their combination is possible to break the degeneracies between cosmological parameters and enable tight constraints on cosmological parameters. In this paper, we combine the observed 130 SGL systems with velocity-dispersion measurements and 7 SGL systems with time-delay measurements to constrain dark-energy cosmological models. It is found that the combination of the two effects does not significantly break the degeneracies between cosmological parameters as expected. However, with the simulations of 8000 SGL systems with well-measured velocity dispersions and 55 SGL systems with well-measured time delays based on the forthcoming LSST survey, we find that the combination of two effects can significantly break the parameter degeneracies, and make the constraint precision of cosmological parameters meet the standard of precision cosmology. We conclude that the observations of SGL will become a useful late-universe probe for precisely measuring cosmological parameters., 18 pages, 6 figures; to appear in Universe

We introduce an ALMA band 3 spectroscopic survey, targeting the brightest submillimeter galaxies (SMGs) in the COSMOS field. Here we present the first results based on the 18 primary SMGs that have 870 $\mu$m flux densities of $S_{870}=12.4-19.3$ mJy and are drawn from a parent sample of 260 ALMA-detected SMGs from the AS2COSMOS survey. We detect emission lines in 17 and determine their redshifts to be in the range of $z=2-5$ with a median of ${3.3\pm0.3}$. We confirm that SMGs with brighter $S_{870}$ are located at higher redshifts. The data additionally cover five fainter companion SMGs, and we obtain line detection in one. Together with previous studies, our results indicate that for SMGs that satisfy our selection, their brightest companion SMGs are physically associated with their corresponding primary SMGs in $\ge40$% of the time, suggesting that mergers play a role in the triggering of star formation. By modeling the foreground gravitational fields, $2$. We determine that about 90\% of the primary SMGs have lines that are better described by double Gaussian profiles, and the median separation of the two Gaussian peaks is 430$\pm$40 km s$^{-1}$. This allows estimates of an average baryon mass, which together with the line dispersion measurements puts our primary SMGs on the similar mass-$\sigma$ correlation found on local early-type galaxies. Finally, the number density of our $z>4$ primary SMGs is found to be $1^{+0.9}_{-0.6}\times10^6$ cMpc$^{-3}$, suggesting that they can be the progenitors of $z\sim3-4$ massive quiescent galaxies., Comment: 30 pages, 16 figures, ApJ in press

Assessing the probability that two or more gravitational waves (GWs) are lensed images of the same source requires an understanding of the image properties, including their relative phase shifts in strong lensing (SL). For non-precessing, circular binaries dominated by quadrupole radiation these phase shifts are degenerate with either a shift in the coalescence phase or a detector and inclination dependent shift in the orientation angle. This degeneracy is broken by the presence of higher harmonic modes with $|m|\ne 2$ in the former and $|m| \ne l$ in the latter. Precession or eccentricity will also break this degeneracy. This implies that lensed GWs will not necessarily be consistent with (unlensed) predictions from general relativity (GR). Therefore, unlike EM lensing, GW SL can lead to images with an observable modified phase evolution. However, for a wide parameter space, the lensed waveform is similar enough to an unlensed waveform that detection pipelines will still find it. For present detectors, templates with a shifted detector-dependent orientation angle have SNR differences of less than $1\%$ for mass ratios up to 0.1, and less than $5\%$ for precession parameters up to 0.5 and eccentricities up to 0.4 at 20Hz. The mismatch is lower than $10\%$ with the alternative detector-independent coalescence phase shift. Nonetheless, for a loud enough source, even with one image it may be possible to directly identify it as a SL image from its non-GR waveform. In more extreme cases, lensing may lead to considerable distortions, and the lensed GWs may be undetected with current searches. Nevertheless, an exact template with a phase shift in Fourier space can always be constructed to fit any lensed GW. We conclude that an optimal search strategy would incorporate phase information in all stages, with an exact treatment in the final assessment of the probability of multiple lensed events., Comment: Matches PRD version. Full abstract in PDF version

We present CIV BLR modeling results for the multiply imaged $z=2.805$ quasar SDSS J2222+2745. Using data covering a 5.3 year baseline after accounting for gravitational time delays, we find models that can reproduce the observed emission-line spectra and integrated CIV fluctuations. The models suggest a thick disk BLR that is inclined by $\sim$40 degrees to the observer's line of sight and with a emissivity weighted median radius of $r_{\rm median} = 33.0^{+2.4}_{-2.1}$ light days. The kinematics are dominated by near-circular Keplerian motion with the remainder inflowing. The rest-frame lag one would measure from the models is $\tau_{\rm median} = 36.4^{+1.8}_{-1.8}$ days, which is consistent with measurements based on cross-correlation. We show a possible geometry and transfer function based on the model fits and find that the model-produced velocity-resolved lags are consistent with those from cross-correlation. We measure a black hole mass of $\log_{10}(M_{\rm BH}/M_\odot) = 8.31^{+0.07}_{-0.06}$, which requires a scale factor of $\log_{10}(f_{{\rm mean},\sigma}) = 0.20^{+0.09}_{-0.07}$., Comment: 8 pages, 5 figures, submitted to ApJL

Strong gravitational lensing along with the distance sum rule method can constrain both cosmological parameters as well as density profiles of galaxies without assuming any fiducial cosmological model. To constrain galaxy parameters and cosmic curvature $(\Omega_{k0})$, we use the distance ratio data from a recently compiled database of $161$ galactic scale strong lensing systems. We use databases of supernovae type-Ia (Pantheon) and Gamma Ray Bursts (GRBs) for calculating the luminosity distance. To study the model of the lens galaxy, we consider a general lens model namely, the Extended Power-Law model. Further, we take into account two different parametrisations of the mass density power-law index $(\gamma)$ to study the dependence of $\gamma$ on redshift. The best value of $\Omega_{k0}$ suggests a closed universe, though a flat universe is accommodated at $68\%$ confidence level. We find that parametrisations of $\gamma$ have a negligible impact on the best fit value of the cosmic curvature parameter. Furthermore, measurement of time delay can be a promising cosmographic probe via "time delay distance" that includes the ratio of distances between the observer, the lens and the source. We again use the distance sum rule method with time-delay distance dataset of H0LiCOW to put constraints on the Cosmic Distance Duality Relation (CDDR) and the cosmic curvature parameter $(\Omega_{k0})$. For this we consider two different redshift-dependent parametrisations of the distance duality parameter $(\eta)$. The best fit value of $\Omega_{k0}$ clearly indicates an open universe. However, a flat universe can be accommodated at $95\%$ confidence level. Further, at $95\%$ confidence level, no violation of CDDR is observed. We believe that a larger sample of strong gravitational lensing systems is needed in order to improve the constraints on the cosmic curvature and distance duality parameter., Comment: 15 Pages, 6 Figures and 11 Tables. Accepted for publication in Phys. Rev. D

Direct detection of gravitational waves was for a long time a holy grail of observational astronomy. The situation changed several years ago with the first ever laboratory detection of gravitational wave signal on the Earth (GW150914), showing once again that Einstein was right. Now, successful operating runs of LIGO/Virgo gravitational wave detectors, resulting with numerous detections of gravitational wave signals from coalescing double compact objects (mainly binary black hole mergers) with the first evidence of coalescing binary neutron star system, elevated multimessenger astronomy to the unprecedented stage. Double compact objects (binary black hole systems, mixed black hole-neutron star systems and double neutron star systems) are the main targets of future ground based and space-borne gravitational wave detectors opening the possibility for multifrequency gravitational wave studies and yielding very rich statistics of such sources. This, in turn, makes possible that certain, non-negligible amount of double compact objects will have a chance of being strongly lensed. In this presentation I will discuss new perspectives for future detections of gravitational wave signals in the case of strong gravitational lensing. First, the expected rates of lensed gravitational wave signals will be presented. Multifrequency detections of lensed gravitational wave events, will demand different treatment at different frequencies, i.e. wave approach vs. geometric optics approach. I will discuss new possibilities emerging from such multifrequency detections.

Recent times witnessed a surge of interest in strong gravitational lensing by black holes due to the Event Horizon Telescope (EHT) results, which suggest comparing the black hole lensing in general relativity and modified gravity theories. This may help us to assess the phenomenological differences between these models. A Kerr black hole is also a solution to some alternative theories of gravity, while recently obtained modified Kerr black holes (hairy Kerr black holes), which evade the no-hair theorem, are due to additional sources from surrounding fluid, like dark matter, having conserved energy momentum tensor (EMT). These hairy Kerr black holes may also be solutions to an alternative theory of gravity. We generalize previous work on gravitational lensing by a Kerr black hole in the strong deflection limits to the hairy Kerr black holes, with a deviation parameter $\alpha$ and a primary hair $\ell_0$. Interestingly, the deflection coefficient $\bar{a}$ increases and decreases with increasing $\ell_0$ and $\alpha$ respectively. $\bar{b}$ shows opposite behaviour with $\ell_0$ and $\alpha$. We also find that the deflection angle $\alpha_D$, angular position $\theta_{\infty}$ and $u_{m}$ decrease, but angular separation $s$ increases with $\alpha$. We compare our results with those for Kerr black holes, and also apply the formalism to discuss the astrophysical consequences in the context of the supermassive black holes Sgr A* and M87*. We observe that the deviations of the angular positions from that of the Kerr black hole are not more than $2.6~\mu$as for Sgr A* and $1.96~\mu$as for M87*, which are unlikely to be resolved by the current EHT observations., Comment: 17 pages, 7 figures, 8 tables, minor typos corrected, accepted in Phys. Rev. D

PKS 1413+135 is one of the most peculiar blazars known. Its strange properties led to the hypothesis almost four decades ago that it is gravitationally lensed by a mass concentration associated with an intervening galaxy. It exhibits symmetric achromatic variability, a rare form of variability that has been attributed to gravitational milli-lensing. It has been classified as a BL Lac object, and is one of the rare objects in this class with a visible counterjet. BL Lac objects have jet axes aligned close to the line of sight. It has also been classified as a compact symmetric object, which have jet axes not aligned close to the line of sight. Intensive efforts to understand this blazar have hitherto failed to resolve even the questions of the orientation of the relativistic jet, and the host galaxy. Answering these two questions is important as they challenge our understanding of jets in active galactic nuclei and the classification schemes we use to describe them. We show that the jet axis is aligned close to the line of sight and PKS 1413+135 is almost certainly not located in the apparent host galaxy, but is a background object in the redshift range $0.247 < z < 0.5$. The intervening spiral galaxy at $z = 0.247$ provides a natural host for the putative lens responsible for symmetric achromatic variability and is shown to be a Seyfert 2 galaxy. We also show that, as for the radio emission, a "multizone" model is needed to account for the high-energy emission., Accepted for publication in The Astrophysical Journal. 28 pages, 15 figures

We study the strong gravitational lensing due to the Kerr black holes with angular momentum $a$ and the Kerr-Newman black holes with additional charge $Q$. We first derive the analytical expressions of the deflection angles of light rays that particularly diverge as they travel near the photon sphere. In this strong deflection limit, the light rays can circle around the black hole multiple times before reaching the observer, giving relativistic images. The obtained analytical expressions are then applied to compute the angular positions and the magnifications of relativistic images due to the supermassive galactic black holes. In this work, we focus on the outermost image with reference to the optical axis. We find that its angular separation from the one closest to the optical axis and the magnification increase in angular momentum $a$ of the black holes for light rays with direct orbits. Additionally, the effects of the charge $Q$ of black holes also increase the angular separation of the outermost image from the others and the magnification for both direct and retrograde orbits. The potentially increasing observability of the relativistic images from the effects of angular momentum and charge of the black holes will be discussed., 27 pages, 6 figures

Gravitational-wave (GW) observations by a network of ground-based laser interferometric detectors allow us to probe the nature of GW polarizations. This would be an interesting test of general relativity (GR), since GR predicts only two polarization modes while there are theories of gravity that predict up to six polarization modes. The ability of GW observations to probe the nature of polarizations is limited by the available number of linearly independent detectors in the network. (To extract all polarization modes, there should be at least as many detectors as the polarization modes.) Strong gravitational lensing of GWs offers a possibility to significantly increase the effective number of detectors in the network. Due to strong lensing (e.g., by galaxies), multiple copies of the same signal can be observed with time delays of several minutes to weeks. Owing to the rotation of the earth, observation of the multiple copies of the same GW signal would allow the network to measure different combinations of the same polarizations. This effectively multiplies the number of detectors in the network. Focusing on strongly lensed signals from binary black hole mergers that produce two observable "images", using Bayesian model selection and assuming simple polarization models, we show that our ability to distinguish between polarization models is significantly improved., 9 pages, 6 figs

Joint analyses of small-scale cosmological structure probes are relatively unexplored and promise to advance measurements of microphysical dark matter properties using heterogeneous data. Here, we present a multidimensional analysis of dark matter substructure using strong gravitational lenses and the Milky Way (MW) satellite galaxy population, accounting for degeneracies in model predictions and using covariances in the constraining power of these individual probes for the first time. We simultaneously infer the projected subhalo number density and the half-mode mass describing the suppression of the subhalo mass function in thermal relic warm dark matter (WDM), $M_{\mathrm{hm}}$, using the semianalytic model $\mathrm{\texttt{Galacticus}}$ to connect the subhalo population inferred from MW satellite observations to the strong lensing host halo mass and redshift regime. Combining MW satellite and strong lensing posteriors in this parameter space yields $M_{\mathrm{hm}}9.7\ \mathrm{keV}$) at $95\%$ confidence and disfavors $M_{\mathrm{hm}}=10^{7.4}\ M_{\mathrm{\odot}}$ ($m_{\mathrm{WDM}}=7.4\ \mathrm{keV}$) with a 20:1 marginal likelihood ratio, improving limits on $m_{\mathrm{WDM}}$ set by the two methods independently by $\sim 30\%$. These results are marginalized over the line-of-sight contribution to the strong lensing signal, the mass of the MW host halo, and the efficiency of subhalo disruption due to baryons and are robust to differences in the disruption efficiency between the MW and strong lensing regimes at the $\sim 10\%$ level. This work paves the way for unified analyses of next-generation small-scale structure measurements covering a wide range of scales and redshifts., 23 pages, 9 figures, 1 table. Updated to published version

Strong gravitational lensing observations can test structure formation models by constraining the masses and concentrations of subhaloes in massive galaxy clusters. Recent work has concluded that cluster subhaloes are more abundant and/or concentrated than predicted by $\Lambda$CDM simulations; this finding has been interpreted as arising from unidentified issues with simulations or an incorrect understanding of the nature of dark matter. We test these hypotheses by comparing observed subhalo masses and maximum circular velocities $v_\mathrm{max}$ to predictions from the high resolution Hydrangea galaxy cluster simulation suite, which is based on the successful EAGLE galaxy formation model. The simulated subhalo mass distribution and mass-$v_\mathrm{max}$ relation agrees well with observations, due to the presence of baryons during tidal stripping. Similar agreement is found for the lower-resolution Illustris-TNG300 simulation. In combination, our results suggest that the abundance and concentration of cluster substructures are not in tension with $\Lambda$CDM, but may provide useful constraints for the refinement of baryon physics models in simulations., Comment: 6 pages, 4 figures; minor changes following first referee report (conclusions unchanged)

We report the detection of a massive neutral gas outflow in the z=2.09 gravitationally lensed Dusty Star-Forming Galaxy HATLASJ085358.9+015537 (G09v1.40), seen in absorption with the OH+(1_1-1_0) transition using spatially resolved (0.5"x0.4") Atacama Large Millimeter/submillimeter Array (ALMA) observations. The blueshifted OH+ line is observed simultaneously with the CO(9-8) emission line and underlying dust continuum. These data are complemented by high angular resolution (0.17"x0.13") ALMA observations of CH+(1-0) and underlying dust continuum, and Keck 2.2 micron imaging tracing the stellar emission. The neutral outflow, dust, dense molecular gas and stars all show spatial offsets from each other. The total atomic gas mass of the observed outflow is 6.7x10^9 M_sun, >25% as massive as the gas mass of the galaxy. We find that a conical outflow geometry best describes the OH+ kinematics and morphology and derive deprojected outflow properties as functions of possible inclination (0.38 deg-64 deg). The neutral gas mass outflow rate is between 83-25400 M_sun/yr, exceeding the star formation rate (788+/-300 M_sun/yr) if the inclination is >3.6 deg (mass-loading factor = 0.3-4.7). Kinetic energy and momentum fluxes span 4.4-290x10^9 L_sun and 0.1-3.7x10^37 dyne, respectively (energy-loading factor = 0.013-16), indicating that the feedback mechanisms required to drive the outflow depend on the inclination assumed. We derive a gas depletion time between 29 and 1 Myr, but find that the neutral outflow is likely to remain bound to the galaxy, unless the inclination is small, and may be re-accreted if additional feedback processes do not occur., 33 pages, 20 figures