Gravitational Lensing Research Papers - Academia.edu (original) (raw)

We have developed a new software tool, LENSVIEW, for modelling resolved gravitational lens images. Based on the LENSMEM algorithm, the software finds the best fitting lens mass model and source brightness distribution using a maximum entropy constraint. The method can be used with any point spread function or lens model. We review the algorithm and introduce some significant improvements. We also investigate and discuss issues associated with the statistical uncertainties of models and model parameters and the issues of source plane size and source pixel size.

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- Algorithms, Gravitational Lensing, Numerical Method, Entropy

We present a new wide field image of the distant cluster AC114 (z = 0.31) obtained with Wide Field and Planetary Camera II onboard the Hubble Space Telescope. This image considerably extends our knowledge of the lensing properties of the cluster beyond that derived by Smail et al. (1995a) from a single WF/PC-1 pointing. In conjunction with published ground-based spectroscopy, we utilise several newly-discovered multiple images to construct an improved mass model for the central regions of the cluster. Using this model, we apply the methodology introduced by Natarajan & Kneib (1997) to interpret local perturbations to the cluster shear field on small scales resulting from mass associated with individual cluster galaxies. We use the lensing signal to place new constraints on the average mass-to-light ratio and spatial extents of the dark matter halos associated with morphologically-classified early-type cluster members.

We present results of ultra-deep ISOCAM observations through a cluster-lens at 7µm and 15µm with the Infrared Space Observatory (ISO) satellite. These observations reveal a large number of luminous Mid-Infrared (MIR) sources. Cross-identification in the optical and Near-Infrared (NIR) wavebands shows that about half of the 7 µm sources are cluster galaxies. The other 7 µm and almost all 15 µm sources are identified as lensed distant galaxies. Thanks to the gravitational amplification they constitute the faintest MIR detected sources, allowing us to extend the number counts in both the 7 and 15 µm bands. In particular, we find that the 15 µm counts have a steep slope α 15µm = −1.5 ± 0.3 and are large, with N 15µm (> 30µJy) = 13 ± 5 arcmin −2 . These numbers rule out non-evolutionary models and favour very strong evolution. Down to our counts limit, we found that the resolved 7 µm and 15 µm background radiation intensity is respectively (2±0.5)×10 −9 and (5±1)×10 −9 W m −2 sr −1 .

- by Steve Maddox
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- Gravitational Lensing, Radio Galaxies

The general theory of relativity was developed by Einstein a century ago. Since then, it has become the standard theory of gravity, especially important to the fields of fundamental astronomy, astrophysics, cosmology, and experimental gravitational physics. Today, the application of general relativity is also essential for many practical purposes involving astrometry, navigation, geodesy, and time synchronization. Numerous experiments have successfully

An introduction to modern theories for the origin of structure in the Universe is given. After a brief review of the growth of cosmological perturbations in an expanding Universe and a summary of some important observational results, the lectures focus on the inflationary Universe scenario and on topological defect models of structure formation. A summary of the theory and current observational status of cosmic microwave background temperature fluctuations is given. The final chapter is devoted to some speculative ideas concerning the connection between cosmology and fundamental physics, in particular to ways in which the singularity problem of classical cosmology may be resolved.

In this paper, we study a regular Bardeen black hole as a gravitational lens. We find the strong deflection limit for the deflection angle, from which we obtain the positions and magnifications of the relativistic images. As an example,... more

- by Carlos Sendra
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- Gravitational Lensing, Black Hole Physics, Mathematical Sciences, Physical sciences

We use a series of ray-tracing experiments to determine the magnification distribution of high-redshift sources by gravitational lensing. We determine empirically the relation between magnification and redshift, for various cosmological models. We then use this relation to estimate the effect of lensing on the determination of the cosmological parameters from observations of high-z supernovae. We found that, for supernovae at redshifts z < 1.8, the effect of lensing is negligible compared to the intrinsic uncertainty in the measurements. Using mock data in the range 1.8 < z < 8, we show that the effect of lensing can become significant. Hence, if a population of very-high-z supernovae was ever discovered, it would be crucial to fully understand the effect of lensing, before these SNe could be used to constrain cosmological models. We show that the distance moduli m−M for an open CDM universe and a ΛCDM universe are comparable at z > 2. Therefore if supernovae up to these redshifts were ever discovered, it is still the ones in the range 0.3 < z < 1 that would distinguish these two models.

This book focuses on Albert Einstein and his interactions with, and responses to, various scientists, both famous and lesser-known. It takes as its starting point that the discussions between Einstein and other scientists all represented a contribution to the edifice of general relativity and relativistic cosmology. These scientists with whom Einstein implicitly or explicitly interacted form a complicated web of collaboration, which this study explores, focusing on their implicit and explicit responses to Einstein's work. This analysis uncovers latent undercurrents, indiscernible to other approaches to tracking the intellectual pathway of Einstein to his general theory of relativity. The interconnections and interactions presented here reveal the central figures who influenced Einstein during this intellectual period. Despite current approaches to history presupposing that the efforts of scientists such as Max Abraham and Gunnar Nordström, which differed from Einstein’s own views, be relegated to the background, this book shows that they all had an impact on the development of Einstein’s theories, stressing the limits of approaches focusing solely on Einstein. As such, General Relativity Conflict and Rivalries proves that the general theory of relativity was not developed as a single, coherent construction by an isolated, brooding individual, but, rather, that it came to fruition through Einstein's conflicts and interactions with other scientists, and was consolidated by his creative processes during these exchanges.

- by Galina Weinstein
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- Philosophy of Science, Cosmology (Physics), Gravitation, Relativity

We report the discovery of a cluster of galaxies in the field of UM425, a pair of quasars separated by 6.5 ′′ . Based on this finding, we revisit the long-standing question of whether this quasar pair is a binary quasar or a wide-separation lens. Previous work has shown that both quasars are at z = 1.465 and show broad absorption lines. No evidence for a lensing galaxy has been found between the quasars, but there were two hints of a foreground cluster: diffuse X-ray emission observed with Chandra, and an excess of faint galaxies observed with the Hubble Space Telescope. Here we show, via VLT spectroscopy, that there is a spike in the redshift histogram of galaxies at z = 0.77. We estimate the chance of finding a random velocity structure of such significance to be about 5%, and thereby interpret the diffuse X-ray emission as originating from z = 0.77, rather than the quasar redshift. The mass of the cluster, as estimated from either the velocity dispersion of the z = 0.77 galaxies or the X-ray luminosity of the diffuse emission, would be consistent with the theoretical mass required for gravitational lensing. The positional offset between the X-ray centroid and the expected location of the mass centroid is ∼40 kpc, which is not too different from offsets observed in lower redshift clusters. However, UM425 would be an unusual gravitational lens, by virtue of the absence of a bright primary lensing galaxy. Unless the mass-to-light ratio of the galaxy is at least 80 times larger than usual, the lensing hypothesis requires that the galaxy group or cluster plays a uniquely important role in producing the observed deflections.

- by Paul Green
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- Organic Chemistry, Astrophysical Plasma, Galaxy Clusters, Gravitational Lensing

We investigate a point-like massive source in non-linear f(R) theories in the case of arbitrary number of spatial dimensions D\geq 3. If D>3 then extra dimensions undergo toroidal compactification. We consider a weak-field approximation with Minkowski and de Sitter background solutions. In both these cases point-like massive sources demonstrate good agreement with experimental data only in the case of ordinary three-dimensional (D=3) space. We generalize this result to the case of perfect fluid with dust-like equations of state in the external and internal spaces. This perfect fluid is uniformly smeared over all extra dimensions and enclosed in a three-dimensional sphere. In ordinary three dimensional (D=3) space, our formulas are useful for experimental constraints on parameters of f(R) models.

- by Maxim Eingorn
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- Mathematical Physics, Field Theory, Geometry And Topology, Physics

In this research-paper, many of the general-relativity-tests such as bending of light near a star and gravitational red/blue shift are explained without general-relativity & even without Newtonian-approach. The authors first raise questions on the validity of both, the Newtonian and the relativistic approach; and then propose a novel alternative-explanation. The new alternative explanation is based on refraction-phenomenon of optics. Estimation of results with new approach are in agreement with known values. Though physics is different, but it is argued that general-relativity based gravitational-bending and refraction based bending have more in common than is generally realized. Also discussed are black-hole and gravitational-lensing in the new perspective of refraction. The new refraction-based theory makes a few new predictions and also suggests a few tests.

- by Anirudh Pradhan
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- General Relativity, Gravitational Lensing, Black Hole

We present near-infrared spectroscopy and Hubble Space Telescope (HST) imaging of ERO J003707+0909.5, the brightest of three gravitationally-lensed images of an Extremely Red Object (ERO) at z = 1.6, in the field of the massive cluster A 68 (z = 0.255). We exploit the superlative resolution of our HST data and the enhanced spatial resolution and sensitivity afforded by the lens amplification to reconstruct the source-plane properties of this ERO. Our morphological and photometric analysis reveals that ERO J003707 is an L ⋆ early-type disk-galaxy and we estimate that ∼ 10 per cent of EROs with (R − K) ≥ 5.3 and K ≤ 21 may have similar properties. The unique association of passive EROs with elliptical galaxies therefore appears to be too simplistic. We speculate on the evolution of ERO J003707: if gas continues to cool onto this galaxy in the manner predicted by hierarchical galaxy formation models, then by the present day, ERO J003707 could evolve into a very luminous spiral galaxy.

- by Harald Ebeling
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- Thermodynamics, Organic Chemistry, Astrophysical Plasma, Dark Matter

On the basis of the Lunar Laser Ranging Data released by NASA on the Silver Jubilee Celebration of Man Landing on Moon on 21st July 1969-1994, theoretical formulation of Earth-Moon tidal interaction was carried out and Planetary Satellite Dynamics was established. It was found that this mathematical analysis could as well be applied to Star and Planets system and since every star could potentially contain an extra-solar system, hence we have a large ensemble of exoplanets to test our new perspective on the birth and evolution of solar systems. Till date 403 exoplanets have been discovered in 390 extra-solar systems. I have taken 12 single planet systems, 4 Brown Dwarf - Star systems and 2 Brown Dwarf pairs. Following architectural design rules are corroborated through this study of exoplanets. All planets are born at inner Clarke Orbit what we refer to as inner geo-synchronous orbit in case of Earth-Moon System. By any perturbative force such as cosmic particles or radiation pressure, the planet gets tipped long of aG1 or short of aG1. Here aG1 is inner Clarke Orbit. The exoplanet can either be launched on death spiral as CLOSE HOT JUPITERS or can be launched on an expanding spiral path as the planets in our Solar System are. It was also found that if the exo-planet are significant fraction of the host star then those exo-planets rapidly migrate from aG1 to aG2 and have very short Time Constant of Evolution as Brown Dwarfs have. This vindicates our basic premise that planets are always born at inner Clarke Orbit. This study vindicates the design rules which had been postulated at 35th COSPAR Scientific Assembly in 2004 at Paris, France, under the title ,New Perspective on the Birth & Evolution of Solar Systems.

- by Bijay_Kumar Sharma
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- Geology, Astrophysics, Gravitational Lensing, Astronomy

In the present work we study numerically quasi-equatorial lensing by the charged, stationary, axially-symmetric Kerr-Sen dilaton-axion black hole in the strong deflection limit. In this approximation we compute the magnification and the positions of the relativistic images. The most outstanding effect is that the Kerr-Sen black hole caustics drift away from the optical axis and shift in clockwise direction with respect to the Kerr caustics. The intersections of the critical curves on the equatorial plane as a function of the black hole angular momentum are found, and it is shown that they decrease with the increase of the parameter Q 2 /M . All of the lensing quantities are compared to particular cases as Schwarzschild, Kerr and Gibbons-Maeda black holes. 2 GL are the monographs by Schneider, Ehlers, Falco [4] and Zakharov [5] and the reviews by Blandford and Narayan [6], Refsdal and Surdej [7], Narayan and Bartelmann [8] and Wambsganss [9].

- by Stoytcho Yazadjiev
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- Quantum Physics, Gravitational Lensing, Relativity and Gravitation, Black Hole

Blackledge, Jonathan Electromagnetic Scattering Solutions for Digital Signal Processing Jyväskylä: University of Jyväskylä, 2009, 297 p. (nid.), 2010 (PDF) (Jyväskylä Studies in Computing ISSN 1456-5390; 108) ISBN 978-951-39-3944-1 (PDF), 978-951-39-3741-6 (nid.) Electromagnetic scattering theory is fundamental to understanding the interaction between electromagnetic waves and inhomogeneous dielectric materials. The theory unpins the engineering of electromagnetic imaging systems over a broad range of frequencies, from optics to radio and microwave imaging, for example. Developing accurate scattering models is particularly important in the field of image understanding and the interpretation of electromagnetic signals generated by scattering events. To this end there are a number of approaches that can be taken. For relatively simple geometric configurations, approximation methods are used to develop a transformation from the object plane (where scattering events take place) to the i...

- by Jonathan Blackledge
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- Physics, Digital Signal Processing, Gravitational Lensing, Low Frequency

We report the discovery of an almost complete Einstein ring of diameter 10" in Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Spectroscopic data from the 6m telescope of the Special Astrophysical Observatory reveals that the deflecting galaxy has a line-of-sight velocity dispersion in excess of 400 km/s and a redshift of 0.444, whilst the source is a star-forming galaxy with a redshift of 2.379. From its color and luminosity, we conclude that the lens is an exceptionally massive Luminous Red Galaxy (LRG) with a mass within the Einstein radius of 5 x 10^12 solar masses. This remarkable system provides a laboratory for probing the dark matter distribution in LRGs at distances out to 3 effective radii, and studying the properties of high redshift star-forming galaxies.

Aims. We analyze OGLE-2007-BLG-050, a high magnification microlensing event (A ∼ 432) whose peak occurred on 2 May, 2007, with pronounced finite-source and parallax effects. We compute planet detection efficiencies for this event in order... more

We numerically construct a symmetric wormhole solution in pure Einstein gravity supported by a massive 3-form field with a potential that contains a quartic self-interaction term. The wormhole spacetimes have only a single throat and they are everywhere regular and asymptotically flat. Furthermore, their mass and throat circumference increase almost linearly as the coefficient of the quartic self-interaction term Λ increases. The amount of violation of the null energy condition (NEC) is proportional to the magnitude of 3-form, thus the NEC is less violated as Λ increases, since the magnitude of 3-form decreases with Λ. In addition, we investigate the geodesics of particles moving around the wormhole. The unstable photon orbit is located at the throat. We also find that the wormhole can cast a shadow whose apparent size is smaller than that cast by the Schwarzschild black hole, but reduces to it when \LambdaΛ acquires a large value. The behavior of the innermost stable circular orbit around this wormhole is also discussed. The results of this paper hint toward the possibility that the 3-form wormholes could be potential black hole mimickers, as long as Λ is sufficiently large, precisely when NEC is weakly violated.

- by Che-Yu Chen
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- General Relativity, Gravitational Lensing, General Theory of Relativity, Wormholes

ii Acknowledgements I would like to acknowledge here all my friends, those who remain friends in spite of large separations in space and time, and those here and now and who, most probably, will remain friends in possible future large separations in space and time. I would like to thank friends who became my collaborators, and collaborators who became friends. To begin with the very beginning, my deep thanks go to my M.Sc. supervisor and my friend, Prof. Michael Vasil'evitch Sazhin. It was he who introduced me to this beautiful field of science-Gravitational Lensing. He taught me many things and methods I am using now, and he will forever remain my teacher and my friend. I would like to acknowledge here the hospitality of IUCAA and many people who were helping me there to feel at home. I would like to thank members of Department of Astrophysics, Delhi University, most of all, Dr. Amitabha Mukherjee, and students of the Department, who were always very nice and helpful to me. Beginning with my first friend in DU, Harvinder, and continuing with Varsha, Abha, Deepak, Abhinav and Namit. iii I am also very grateful to the families of my friends; especially to Abha's family, Amber and Gaurav, who were always so friendly and attentive to me and my daughter that we felt like being a part of it. My special thanks go to my co-supervisor, Dr. Shobhit Mahajan, without whom my thesis would have been unreadable. I am infinitely grateful to Prof. A. Prasanna and to my collaborators, Drs. Diego Torres, Gustavo Romero and Zafar Turakulov. Their ideas and work exposed me to many new areas of science and helped me to shape my thesis. I can't thank enough my husband, who was always there for any of my questions and problems, whose ideas were sometimes better than mine, and who helped me enourmously with my work. But this thesis would have been impossible without my guide, the person who took me under his wing and nurtured me, who was patient (and sometimes not so patient) with me, who was forgiving my bad moods and stood by me, who encouraged my independence and didn't mind when I was venturing into new territories. And thus, rephrasing the words of Ken Kesey in his "One Flew Over the Cuckoo's Nest", I dedicate this thesis iv To my supervisor, who told me that there are no dragons and then took me to their lairs. v

In Kaluza-Klein models, we investigate soliton solutions of Einstein equation. We obtain the formulas for perihelion shift, deflection of light, time delay of radar echoes and PPN parameters. We find that the solitonic parameter k should be very big: |k|\geq 2.3\times10^4. We define a soliton solution which corresponds to a point-like mass source. In this case the soliton parameter k=2, which is clearly contrary to this restriction. Similar problem with the observations takes place for static spherically symmetric perfect fluid with the dust-like equation of state in all dimensions. The common for both of these models is the same equations of state in our three dimensions and in the extra dimensions. All dimensions are treated at equal footing. To be in agreement with observations, it is necessary to break the symmetry between the external/our and internal spaces. It takes place for black strings which are particular examples of solitons with k\to \infty. For such k, black strings are in concordance with the observations. Moreover, we show that they are the only solitons which are at the same level of agreement with the observations as in general relativity. Black strings can be treated as perfect fluid with dust-like equation of state p_0=0 in the external/our space and very specific equation of state p_1=-(1/2)\epsilon in the internal space. The latter equation is due to negative tension in the extra dimension. We also demonstrate that dimension 3 for the external space is a special one. Only in this case we get the latter equation of state. We show that the black string equations of state satisfy the necessary condition of the internal space stabilization. Therefore, black strings are good candidates for a viable model of astrophysical objects (e.g., Sun) if we can provide a satisfactory explanation of negative tension for particles constituting these objects.

- by Maxim Eingorn and +1
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- Field Theory, Geometry And Topology, Elementary Particle Physics, Space Sciences

The changing view of planets orbiting low mass stars, M stars, as potentially hospitable worlds for life and its remote detection was motivated by several factors, including the demonstration of viable atmospheres and oceans on tidally locked planets, normal incidence of dust disks, including debris disks, detection of planets with masses in the 5-20 M ᮍ range, and predictions of unusually strong spectral biosignatures. We present a critical discussion of M star properties that are relevant for the long-and short-term thermal, dynamical, geological, and environmental stability of conventional liquid water habitable zone (HZ) M star planets, and the advantages and disadvantages of M stars as targets in searches for terrestrial HZ planets using various detection techniques. Biological viability seems supported by unmatched very long-term stability conferred by tidal locking, small HZ size, an apparent shortfall of gas giant planet perturbers, immunity to large astrosphere compressions, and several other factors, assuming incidence and evolutionary rate of life benefit from lack of variability. Tectonic regulation of climate and dynamo generation of a protective magnetic field, especially for a planet in synchronous rotation, are important unresolved questions that must await improved geodynamic models, though they both probably impose constraints on the planet mass. M star HZ terrestrial planets must survive a number of early trials in order to enjoy their many Gyr of stability. Their formation may be jeopardized by an insufficient initial disk supply of solids, resulting in the formation of objects too small and/or dry for hab-85 itability. The small empirical gas giant fraction for M stars reduces the risk of formation suppression or orbit disruption from either migrating or nonmigrating giant planets, but effects of perturbations from lower mass planets in these systems are uncertain. During the first ϳ1 Gyr, atmospheric retention is at peril because of intense and frequent stellar flares and sporadic energetic particle events, and impact erosion, both enhanced, the former dramatically, for M star HZ semimajor axes. Loss of atmosphere by interactions with energetic particles is likely unless the planetary magnetic moment is sufficiently large. For the smallest stellar masses a period of high planetary surface temperature, while the parent star approaches the main sequence, must be endured. The formation and retention of a thick atmosphere and a strong magnetic field as buffers for a sufficiently massive planet emerge as prerequisites for an M star planet to enter a long period of stability with its habitability intact. However, the star will then be subjected to short-term fluctuations with consequences including frequent unpredictable variation in atmospheric chemistry and surficial radiation field. After a review of evidence concerning disks and planets associated with M stars, we evaluate M stars as targets for future HZ planet search programs. Strong advantages of M stars for most approaches to HZ detection are offset by their faintness, leading to severe constraints due to accessible sample size, stellar crowding (transits), or angular size of the HZ (direct imaging). Gravitational lensing is unlikely to detect HZ M star planets because the HZ size decreases with mass faster than the Einstein ring size to which the method is sensitive. M star Earth-twin planets are predicted to exhibit surprisingly strong bands of nitrous oxide, methyl chloride, and methane, and work on signatures for other climate categories is summarized. The rest of the paper is devoted to an examination of evidence and implications of the unusual radiation and particle environments for atmospheric chemistry and surface radiation doses, and is summarized in the Synopsis. We conclude that attempts at remote sensing of biosignatures and nonbiological markers from M star planets are important, not as tests of any quantitative theories or rational arguments, but instead because they offer an inspection of the residues from a Gyr-long biochemistry experiment in the presence of extreme environmental fluctuations. A detection or repeated nondetections could provide a unique opportunity to partially answer a fundamental and recurrent question about the relation between stability and complexity, one that is not addressed by remote detection from a planet orbiting a solar-like star, and can only be studied on Earth using restricted microbial systems in serial evolution experiments or in artificial life simulations. This proposal requires a planet that has retained its atmosphere and a water supply. The discussion given here suggests that observations of M star exoplanets can decide this latter question with only slight modifications to plans already in place for direct imaging terrestrial exoplanet missions. Key Words: M star planets-Habitable planets-Life and stellar activity-Spectral biosignatures-Terrestrial planet formation-Exoplanet properties. Astrobiology 7(1), 85-166. SCALO ET AL. 86 1.8. HZs for M star planets 97 A. Specificity of water 97 B. Biomolecular recognition and water habitability 98 C. Varieties of habitability 99 i. Liquid water thermal HZ 99 ii. Cosmic ray environment 101 iii. Geologically sustainable habitability 103 iv. Dynamical habitability 104 a. Known exoplanet systems 104 b. Formation and stability: nonmigrating giants 105 c. Terrestrial planet formation in the presence of migrating giants 107 and large eccentricity 1.9. Catalogues of M star target properties 111 2. M star habitable planet and planet search programs 113 2.1. Trends of protostellar disk mass with stellar mass 114 2.2. Implications of existing exoplanet results for M star planets 118 i. Frequency of giant planets in M star systems 120 2.3. The new face of M star planets: five low mass planets 121 2.4. Future detection of HZ terrestrial planets 122 i. Radial velocity detection of M star HZ planets 123 ii. Astrometric detection of M star HZ planets 123 iii. Transit detection of M star terrestrial exoplanets 124 iv. Direct imaging of M star terrestrial HZ planets 126 a. Spectroscopic signatures from direct imaging 127 b. Photometric biomarkings from direct imaging 129 v. Additional possibilities 129 3. Flares, CMEs, X-rays, and EUV and UV activity of M stars 130 3.1. Flares 130 3.2. Age-activity relation and X-ray luminosity 133 3.3. Expected CMEs 137 3.4. Star spot-type phenomena 137 3.5. UV spectra 138 4. Activity effects on atmospheres of Earth-like exoplanets within M star HZs 139 4.1. UV influence on photochemistry and surface biota of Earth-like exoplanets 139 within M star HZs 4.2. Effect of energetic particles on M star planet biomarkers 141 4.3. Thermospheric heating of M star HZ planets due to X-ray and EUV fluxes 143 4.4. Life in a fluctuating environment 145 5. Conclusion 148 6. Synopsis 149 7. Acknowledgments 152 8. Abbreviations 153 9. References 153 M STAR RELEVANCE IN TERRESTRIAL PLANET SEARCH 87

- by Antigona Segura
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- Geology, Geochemistry, Remote Sensing, Atmospheric Chemistry
- by mohammad nouri
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- General Relativity, Quantum Mechanics, Gravitational Lensing, Physical sciences

The cold, dry and stable air above the summits of the Antarctic plateau provides the best ground-based observing conditions from optical to sub-mm wavelengths to be found on the Earth. PILOT is a proposed 2 m telescope, to be built at Dome C in Antarctica, able to exploit these conditions for conducting astronomy at optical and infrared wavelengths. While PILOT is intended as a pathfinder towards the construction of future grand-design facilities, it will also be able to undertake a range of fundamental science investigations in its own right. This paper provides the performance specifications for PI-LOT, including its instrumentation. It then describes the kinds of science projects that it could best conduct. These range from planetary science to the search for other solar systems, from star formation within the Galaxy to the star formation history of the Universe, and from gravitational lensing caused by exo-planets to that produced by the cosmic web of dark matter. PILOT would be particularly powerful for wide-field imaging at infrared wavelengths, achieving near-diffraction limited performance with simple tip-tilt wavefront correction. PILOT would also be capable of near-diffraction limited performance in the optical wavebands, as well be able to open new wavebands for regular ground based observation; in the mid-IR from 17 to 40 µm and in the sub-mm at 200 µm.

- by Vincent Minier
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- Gravitation, Star Formation, Dark Matter, Theory

The Cluster Lensing And Supernova survey with Hubble (CLASH) is a 524-orbit Multi-Cycle Treasury Program to use the gravitational lensing properties of 25 galaxy clusters to accurately constrain their mass distributions. The survey, described in detail in this paper, will definitively establish the degree of concentration of dark matter in the cluster cores, a key prediction of structure formation models. The CLASH cluster sample is larger and less biased than current samples of space-based imaging studies of clusters to similar depth, as we have minimized lensing-based selection that favors systems with overly dense cores. Specifically, 20 CLASH clusters are solely X-ray selected. The X-ray-selected clusters are massive (kT > 5 keV) and, in most cases, dynamically relaxed. Five additional clusters are included for their lensing strength (θ Ein > 35 at z s = 2) to optimize the likelihood of finding highly magnified high-z (z > 7) galaxies. A total of 16 broadband filters, spanning the near-UV to near-IR, are employed for each 20-orbit campaign on each cluster. These data are used to measure precise (σ z ∼ 0.02(1 + z)) photometric redshifts for newly discovered arcs. Observations of each cluster are spread over eight epochs to enable a search for Type Ia supernovae at z > 1 to improve constraints on the time dependence of the dark energy equation of state and the evolution of supernovae. We present newly re-derived X-ray luminosities, temperatures, and Fe abundances for the CLASH clusters as well as a representative source list for MACS1149.6 + 2223 (z = 0.544).

- by Ruth Lazkoz
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- Organic Chemistry, Astrophysical Plasma, Dark Matter, Galaxy Clusters

Gravitational lensing measures projected mass densities. Strong lensing probes the matter distribution in the central regions of dark matter haloes. Recent analyses of galaxy cluster surveys have focused on dark matter density profiles, confirming in part the predictions of N-body simulations. Numerical simulations with collisionless cold dark matter particles find that halo profiles are well fitted by the NFW profile. Such haloes are characterized by a mass-concentration relation, with their concentration decreasing with mass, and by the a large amount of substructures. We present a new algorithm for simulating the gravitational lensing signal from cluster-sized haloes: MOKA. This algorithm implements the most recent results from numerical simulations to create realistic lenses with properties independent of numerical resolution. We perform systematic studies of the strong lensing cross section in dependence of halo structure. We find that the cross sections depend most strongly on the concentration and on the inner slope of the density profile of a halo. However, fixing these properties, further important contributions are due to halo triaxiality and the presence of a bright central galaxy.

- by Michele Boldrin
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- Dark Matter, Galaxy Clusters, Gravitational Lensing, Numerical Simulation

The null geodesic equations that describe motion of photons in Kerr spacetime are solved exactly in the presence of the cosmological constant Λ. The exact solution for the deflection angle for generic light orbits (i.e. non-polar, non-equatorial) is calculated in terms of the generalized hypergeometric functions of Appell and Lauricella. We then consider the more involved issue in which the black hole acts as a 'gravitational lens'. The constructed Kerr black hole gravitational lens geometry consists of an observer and a source located far away and placed at arbitrary inclination with respect to black hole's equatorial plane. The resulting lens equations are solved elegantly in terms of Appell-Lauricella hypergeometric functions and the Weierstraß elliptic function. We then, systematically, apply our closed form solutions for calculating the image and source positions of generic photon orbits that solve the lens equations and reach an observer located at various values of the polar angle for various values of the Kerr parameter and the first integrals of motion. In this framework, the magnification factors for generic orbits are calculated in closed analytic form for the first time. The exercise is repeated with the appropriate modifications for the case of non-zero cosmological constant.

- by Georgios Kraniotis
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- Physics, Gravitational Lensing, Mathematical Sciences, Physical sciences

Context. Massive galaxy clusters at intermediate redshift can magnify the flux of distant background sources by several magnitudes. Aims. We exploit this effect to search for lensed distant supernovae that may otherwise be too faint to be detected. Methods. A supernova search was conducted at near infrared wavelengths using the ISAAC instrument at the VLT. The massive galaxy clusters Abell 1689, Abell 1835, and AC114 were observed for a total of 20 h to search for supernovae in gravitationally magnified background galaxies. The observations were split into individual epochs of 2 h of exposure time, separated by approximately one month. Image-subtraction techniques were used to search for transient objects with light curve properties consistent with supernovae, both in our new and archival ISAAC/VLT data. The limiting magnitude of the individual epochs was estimated by adding artificial stars to the subtracted images. Most of the epochs reach 90% detection efficiency at S Z(J) 23.8-24.0 mag (Vega). Results. Two transient objects, both in archival images of Abell 1689 and AC114, were detected. The transient in AC114 coincideswithin the position uncertainty-with an X-ray source and is likely to be a variable AGN at the cluster redshift. The transient in Abell 1689 was found at S Z = 23.24 mag, ∼0.5 away from a galaxy with photometric redshift z gal = 0.6 ± 0.15. The light curves and the colors of the transient are consistent with a reddened type IIP supernova at redshift z = 0.59 ± 0.05. The lensing model of Abell 1689 predicts ∼1.4 mag of magnification at the position of the transient, making it the most magnified supernova ever found and only the second supernova found behind a galaxy cluster. Conclusions. Our pilot survey has demonstrated the feasibility to find distant gravitationally magnified supernovae behind massive galaxy clusters. One likely supernova was found behind Abell 1689, in accordance with the expectations for this survey, as shown in an accompanying analysis paper.

- by A. Goobar
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- Galaxy Clusters, Dust (Astronomy & Astrophysics), Near Infrared, Gravitational Lensing
- by Tiberiu Harko
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- Dark Matter, Gravitational Lensing, Dwarf Galaxies, Bose-Einstein Condensate

We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by . We present non-parametric inversions of the 2D shear profiles to the mean 3D cluster density and mass profiles in bins of both optical richness and cluster i-band luminosity. Since the mean cluster density profile is proportional to the cluster-mass correlation function, the mean profile is spherically symmetric by the assumptions of large-scale homogeneity and isotropy. We correct the inferred 3D profiles for systematic effects, including non-linear shear and the fact that cluster halos are not all precisely centered on their brightest galaxies. We also model the measured cluster shear profile as a sum of contributions from the brightest central galaxy, the cluster dark matter halo, and neighboring halos. We infer the relations between mean cluster virial mass and optical richness and luminosity over two orders of magnitude in cluster mass; the virial mass at fixed richness or luminosity is determined with a precision of ∼ 13% including both statistical and systematic errors. We also constrain the halo concentration parameter and halo bias as a function of cluster mass; both are in good agreement with predictions from N-body simulations of LCDM models. The methods employed here will be applicable to deeper, wide-area optical surveys that aim to constrain the nature of the dark energy, such as the Dark Energy Survey, the Large Synoptic Survey Telescope and space-based surveys.

- by Timothy McKay
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- Organic Chemistry, Astrophysical Plasma, Dark Matter, Galaxy Clusters

The redshift distribution of flat-spectrum radio sources with 5 GHz flux densities S 5 ∼ > 5 mJy is a key component in using current radio lens surveys to probe the cosmological model. We have constructed the first flat-spectrum radio sample in the flux density range 3-20 mJy. Our new sample has 33 sources; we have determined the redshifts of 14 of these (42% complete). The low mean redshift, z ≃ 0.75, of our faintest sample needs to be confirmed by further observations to improve the sample completeness. We also increased the redshift completeness of several surveys of brighter flat-spectrum sources. While the mean redshift, z ≃ 1.1 of flat-spectrum samples fainter than 1 Jy is nearly constant, the fraction of the sources identifiable as quasars steadily drops from ∼ 80% to ∼ 10% as the flux density of the sources decreases.

- by JOSE GARCIA
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- Organic Chemistry, Astrophysical Plasma, Gravitational Lensing, Spectrum

Aims. We combine measurements of weak gravitational lensing from the CFHTLS-Wide survey, supernovae Ia from CFHT SNLS and CMB anisotropies from WMAP5 to obtain joint constraints on cosmological parameters, in particular, the dark-energy equation-ofstate parameter w. We assess the influence of systematics in the data on the results and look for possible correlations with cosmological parameters. Methods. We implemented an MCMC algorithm to sample the parameter space of a flat CDM model with a dark-energy component of constant w. Systematics in the data are parametrised and included in the analysis. We determine the influence of photometric calibration of SNIa data on cosmological results by calculating the response of the distance modulus to photometric zero-point variations. The weak lensing data set is tested for anomalous field-to-field variations and a systematic shape measurement bias for high-redshift galaxies. Results. Ignoring photometric uncertainties for SNLS biases cosmological parameters by at most 20% of the statistical errors, using supernovae alone; the parameter uncertainties are underestimated by 10%. The weak-lensing field-to-field variance between 1 deg 2 -MegaCam pointings is 5%-15% higher than predicted from N-body simulations. We find no bias in the lensing signal at high redshift, within the framework of a simple model, and marginalising over cosmological parameters. Assuming a systematic underestimation of the lensing signal, the normalisation σ 8 increases by up to 8%. Combining all three probes we obtain −0.10 < 1 + w < 0.06 at 68% confidence (−0.18 < 1 + w < 0.12 at 95%), including systematic errors. Our results are therefore consistent with the cosmological constant Λ. Systematics in the data increase the error bars by up to 35%; the best-fit values change by less than 0.15σ. cosmic shear data (Fu et al. 2008, hereafter F08) and supernova (SN) Ia data from the Supernova Legacy Survey (SNLS, Astier et al. 2006, hereafter A06). We complement these with CMB measurements from the Wilkinson Microwave Anisotropy Probe (WMAP5, Hinshaw et al. 2009, hereafter H09).

The null geodesic equations that describe motion of photons in Kerr spacetime are solved exactly in the presence of the cosmological constant Λ. The exact solution for the deflection angle for generic light orbits (i.e. non-polar, non-equatorial) is calculated in terms of the generalized hypergeometric functions of Appell and Lauricella. We then consider the more involved issue in which the black hole acts as a `gravitational lens'. The constructed Kerr black hole gravitational lens geometry consists of an observer and a source located far away and placed at arbitrary inclination with respect to the black hole's equatorial plane. The resulting lens equations are solved elegantly in terms of Appell-Lauricella hypergeometric functions and the Weierstrass elliptic function. We then, systematically, apply our closed form solutions for calculating the image and source positions of generic photon orbits that solve the lens equations and reach an observer located at various values ...

- by Georgios Kraniotis
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- Physics, Gravitational Lensing, Mathematical Sciences, Physical sciences

Main Scientific Objectives Understand the nature of Dark Energy and Dark Matter by:  Reach a dark energy FoM > 400 using only weak lensing and galaxy clustering; this roughly corresponds to 1 sigma errors on w p and w a of 0.02 and 0.1, respectively.  Measure γ, the exponent of the growth factor, with a 1 sigma precision of < 0.02, sufficient to distinguish General Relativity and a wide range of modified-gravity theories  Test the Cold Dark Matter paradigm for hierarchical structure formation, and measure the sum of the neutrino masses with a 1 sigma precision better than 0.03eV.  Constrain n s , the spectral index of primordial power spectrum, to percent accuracy when combined with Planck, and to probe inflation models by measuring the non-Gaussianity of initial conditions parameterised by f NL to a 1 sigma precision of ~2. SURVEYS Area (deg2) Description Wide Survey 15,000 (required) 20,000 (goal) Step and stare with 4 dither pointings per step.

- by carmelita carbone
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- Dark Matter, Dark Energy, Near Infrared, Gravitational Lensing
- by Hiroshi Karoji
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- Multidisciplinary, Gravitational Lensing, Nature, Radio Galaxies

Many of the general-relativity-tests such as bending of light near a star and gravitational red/blue shift are explained without general-relativity & without Newtonian-approach. The authors first cast doubts on both, the Newtonian and the relativistic approach; and proposes a novel alternative-explanation. The new alternative explanation is based on refraction-phenomenon of optics. Estimation of results, with new approach, are in agreement with known values. Though physics is different, but it is argued that general-relativity based gravitational-bending and refraction-based bending have more in common than is generally realized. Also discussed are black-hole and gravitational-lensing in the new perspective of refraction. The new refraction-based theory makes a few new predictions and also suggests a few tests..

- by Sushant Gupta
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- General Relativity, Gravitational Lensing, Black Hole

The construction of adaptive nonparametric procedures by means of wavelet thresholding techniques is now a classical topic in modern mathematical statistics. In this paper, we extend this framework to the analysis of nonparametric regression on sections of spin fiber bundles defined on the sphere. This can be viewed as a regression problem where the function to be estimated takes as its values algebraic curves (for instance, ellipses) rather than scalars, as usual. The problem is motivated by many important astrophysical applications, concerning for instance the analysis of the weak gravitational lensing effect, i.e. the distortion effect of gravity on the images of distant galaxies. We propose a thresholding procedure based upon the (mixed) spin needlets construction recently advocated by Marinucci (2008,2010) and , and we investigate their rates of convergence and their adaptive properties over spin Besov balls.

- by Domenico Marinucci
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- Statistics, Gravitational Lensing, Multivariate Analysis, Thresholding

We present an updated analysis of the M31 pixel lensing candidate event OAB-N2 previously reported in Calchi . Here we take advantage of new data both astrometric and photometric. Astrometry: using archival 4m-KPNO and HST/WFPC2 data we perform a detailed analysis on the event source whose result, although not fully conclusive on the source magnitude determination, is confirmed by the following light curve photometry analysis. Photometry: first, unpublished WeCAPP data allows us to confirm OAB-N2, previously reported only as a viable candidate, as a well constrained pixel lensing event. Second, this photometry enables a detailed analysis in the event parameter space including the effects due to finite source size. The combined results of these analyses allow us to put a strong lower limit on the lens proper motion. This outcome favors the MACHO lensing hypothesis over self lensing for this individual event and points the way toward distinguishing between the MACHO and self-lensing hypotheses from larger data sets. Subject headings: dark matter -gravitational lensing -galaxies: halos -galaxies: individual (M31, NGC 224) -Galaxy: halo * Royal Society University Research Fellow † http://plan.physics.unisa.it/index.htm 1 Hereafter we will refer to "self lensing", broadly speaking, for any microlensing event with a stellar lens, not necessarily belonging to the same stellar population of the source.

used the Galaxy Evolution Explorer (GALEX) UV imaging survey to show that there exists a rare population of nearby compact UV-luminous galaxies (UVLGs) that closely resembles high redshift Lyman break galaxies (LBGs). We present HST images in the UV, optical, and Hα, and resimulate them at the depth and resolution of the GOODS/UDF fields to show that the morphologies of UVLGs are also similar to those of LBGs. Our sample of 8 LBG analogs thus provides detailed insight into the connection between star formation and LBG morphology. Faint tidal features or companions can be seen in all of the rest-frame optical images, suggesting that the starbursts are the result of a merger or interaction. The UV/optical light is dominated by unresolved (∼100-300 pc) super starburst regions (SSBs). A detailed comparison with the galaxies Haro 11 and VV 114 at z = 0.02 indicates that the SSBs themselves consist of diffuse stars and (super) star clusters. The structural features revealed by the new HST images occur on very small physical scales and are thus not detectable in images of high redshift LBGs, except in a few cases where they are magnified by gravitational lensing. We propose, therefore, that LBGs are mergers of gas-rich, relatively low-mass (M * ∼ 10 10 M ⊙ ) systems, and that the mergers trigger the formation of SSBs. If galaxies at high redshifts are dominated by SSBs, then the faint end slope of the luminosity function is predicted to have slope α ∼ 2. Our results are the most direct confirmation to date of models that predict that the main mode of star formation in the early universe was highly collisional.

- by Antara Basu-Zych
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- Organic Chemistry, Astrophysical Plasma, Star Formation, Early Universe

We present the discovery of a Neptune-mass planet OGLE-2007-BLG-368Lb with a planet-star mass ratio of q = [9.5 ± 2.1] × 10 −5 via gravitational microlensing. The planetary deviation was detected in real-time thanks to the high cadence of the MOA survey, real-time light curve monitoring and intensive followup observations. A Bayesian analysis returns the stellar mass and distance at M l = 0.64 +0.21 −0.26 M ⊙ and D l = 5.9 +0.9 −1.4 kpc, respectively, so the mass and separation of the planet are M p = 20 +7 −8 M ⊕ and a = 3.3 +1.4 −0.8 AU, respectively. This discovery adds another cold Neptune-mass planet to the planetary sample discovered by microlensing, which now comprise four cold Neptune/Super-Earths, five gas giant planets, and another sub-Saturn mass planet whose nature is unclear. The discovery of these ten cold exoplanets by the microlensing method implies that the mass ratio function of cold exoplanets scales as dN pl /d log q ∝ q −0.7±0.2 with a 95% confidence level upper limit of n < −0.35 (where dN pl /d log q ∝ q n ). As microlensing is most sensitive to planets beyond the snow-line, this implies that Neptune-mass planets are at least three times more common than Jupiters in this region at the 95% confidence level.

- by Pascal Fouqué
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- Organic Chemistry, Astrophysical Plasma, Gravitational Lensing, Bayesian Analysis

Aims. The Large Binocular Cameras (LBC) are two twin wide field cameras (FOV ∼ 23 ′ × 25 ′ ) mounted at the prime foci of the 8.4m Large Binocular Telescope (LBT). We performed a weak lensing analysis of the z = 0.288 cluster Abell 611 on g-band data obtained by the blue-optimized Large Binocular Camera in order to estimate the cluster mass. Methods. Due to the complexity of the PSF of LBC, we decided to use two different approaches, KSB and Shapelets, to measure the shape of background galaxies and to derive the shear signal produced by the cluster. Then we estimated the cluster mass with both aperture densitometry and parametric model fits.

- by F. Pedichini and +3
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- Galaxy Clusters, Dust (Astronomy & Astrophysics), Gravitational Lensing, Field of View
- by Remi Cabanac
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- Physics, Dark Matter, Dust (Astronomy & Astrophysics), Gravitational Lensing

In this work we study gravitational lensing of neutrinos by Schwarzschild black holes. In particular, we analyze the case of a neutrino transient source associated with a gamma-ray burst lensed by a supermassive black hole located at the center of an interposed galaxy. We show that the primary and secondary images have an angular separation beyond the resolution of forthcoming km-scale detectors, but the signals from each image have time delays between them that in most cases are longer than the typical duration of the intrinsic events. In this way, the signal from different images can be detected as separate events coming from the very same location in the sky. This would render an event that otherwise might have had a low signal-to-noise ratio a clear detection, since the probability of a repetition of a signal from the same direction is negligible. The relativistic images are so faint and proximate that are beyond the sensitivity and resolution of the next-generation instruments.

- by Gustavo E Romero
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- Physics, Black Holes, Gravitational Lensing, Probability