Constraining the mass density of free-floating black holes using razor-thin lensing arcs

Strong lensing of active galactic nuclei in the radio can result in razor-thin arcs, with a thickness of less than a milli-arcsecond, if observed at the resolution achievable with very long baseline interferometry (VLBI). Such razor-thin arcs provide a unique window on the coarseness of the matter distribution between source and observer. In this paper, we investigate to what extent such razor-thin arcs can constrain the number density and mass function of `free-floating' black holes, defined as black holes that do not, or no longer, reside at the centre of a galaxy. These can be either primordial in origin or arise as by-products of the evolution of super-massive black holes in galactic nuclei. When sufficiently close to the line of sight, free-floating black holes cause kink-like distortions in the arcs, which are detectable by eye in the VLBI images as long as the black hole mass exceeds $\sim 1000$ Solar masses. Using a crude estimate for the detectability of such distortions, we analytically compute constraints on the matter density of free-floating black holes resulting from null-detections of distortions along a realistic, fiducial arc, and find them to be comparable to those from quasar milli-lensing. We also use predictions from a large hydrodynamical simulation for the demographics of free-floating black holes that are not primordial in origin, and show that their predicted mass density is roughly four orders of magnitude below the constraints achievable with a single razor-thin arc.Comment: 17 pages, 13 figures, 1 table, comments welcom

Detection of the Gravitational Lens Magnifying a Type Ia Supernova

Objects of known brightness, like Type Ia supernovae (SNIa), can be used to measure distances. If a massive object warps spacetime to form multiple images of a background SNIa, a direct test of cosmic expansion is also possible. However, these lensing events must first be distinguished from other rare phenomena. Recently, a supernova was found to shine much brighter than normal for its distance, which resulted in a debate: was it a new type of superluminous supernova or a normal SNIa magnified by a hidden gravitational lens? Here we report that a spectrum obtained after the supernova faded away shows the presence of a foreground galaxy--the first found to strongly magnify a SNIa. We discuss how more lensed SNIa may be found than previously predicted.Comment: 32 pages, 10 figures. Accepted for publication in Scienc

Texas’s New Habeas Corpus Procedure For Death-Row Inmates: Kafkaesque-And Probably Unconstitutional

Texas courts should embrace their duty to protect the constitution and forbid the legislature from pursuing a politically popular agenda at the expense of the fundamental rights of certain citizens. Article 11.071 of the Texas Code of Criminal Procedure runs afoul of the language, intent, and purpose of Texas constitutional guarantees, and eliminates procedural protections designed to guard against the execution of innocent persons. The Texas Legislature should not be allowed to shorten the time period for seeking habeas relief. Article 11.071 violates the due course of law provisions of the Texas Constitution and violates the Texas equal rights provision. The principal purpose of the writ of habeas corpus is to provide prisoners with the means to challenge the legality of his or her confinement outside of the ordinary appellate process. By limiting access to the Great Writ, the Texas Legislature has engaged in the very governmental abuses that the framers and ratifiers of the Texas Bill of Rights sought to prevent

Risk factors influencing the bone health in perimenopausal and postmenopausal women

Background: Bone loss is being increasingly identified in premenopausal and early postmenopausal women. The significance of low bone mineral density (BMD) in females needs to be addressed. Female reproductive system plays a major role in regulating the bone loss from menarche to senescence. The purpose of our study is to identify the menstrual and reproductive factors that may lead to decreased bone mass during the premenopausal period so that early intervention could lead to improved bone health.Methods: The study was conducted on 100 women aged 40 - 60 years attending the outpatient department in Pandit Bhagwat Dayal Sharma PGIMS, Rohtak, Haryana, India. Their age, parity, body mass index, age at menarche, age at first pregnancy, duration of breast feeding, use of combined oral contraceptive, interpregnancy interval and BMD values were recorded. BMD was measured by dual- energy x-ray absorptiometry. Pearson test was used for correlation analysis. Comparison between the groups was conducted using analysis of variance (ANOVA) and Tukey’s test.Results: A significant negative correlation was established between parity, age at menarche, duration of breast feeding and BMD values. On the other hand, BMI and duration of oral contraceptive use showed a significant positive correlation with BMD values.Conclusions: Identification of risk factors for low BMD will provide the opportunity for early intervention to preventosteoporosis and will reduce the burden of unnecessary BMD testing in elderly age group for screening of osteoporosis

A spectral function tour of electron-phonon coupling outside the Migdal limit

We simulate spectral functions for electron-phonon coupling in a filled band system - far from the asymptotic limit often assumed where the phonon energy is very small compared to the Fermi energy in a parabolic band and the Migdal theorem predicting 1+lambda quasiparticle renormalizations is valid. These spectral functions are examined over a wide range of parameter space through techniques often used in angle-resolved photoemission spectroscopy (ARPES). Analyzing over 1200 simulations we consider variations of the microscopic coupling strength, phonon energy and dimensionality for two models: a momentum-independent Holstein model, and momentum-dependent coupling to a breathing mode phonon. In this limit we find that any `effective coupling', lambda_eff, inferred from the quasiparticle renormalizations differs from the microscopic dimensionless coupling characterizing these Hamiltonians, lambda, and could drastically either over- or under-estimate it depending on the particular parameters and model. In contrast, we show that perturbation theory retains good predictive power for low coupling and small momenta, and that the momentum-dependence of the self-energy can be revealed via the relationship between velocity renormalization and quasiparticle strength. Additionally we find that (although not strictly valid) it is often possible to infer the self-energy and bare electronic structure through a self-consistent Kramers-Kronig bare-band fitting; and also that through lineshape alone, when Lorentzian, it is possible to reliably extract the shape of the imaginary part of a momentum-dependent self-energy without reference to the bare-band.Comment: 15 pages, 11 figures. High resolution available here: http://www.physics.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Articles/sf_tour.pd

Satellite Kinematics I: A New Method to Constrain the Halo Mass-Luminosity Relation of Central Galaxies

Satellite kinematics can be used to probe the masses of dark matter haloes of central galaxies. In order to measure the kinematics with sufficient signal-to-noise, one uses the satellite galaxies of a large number of central galaxies stacked according to similar properties (e.g., luminosity). However, in general the relation between the luminosity of a central galaxy and the mass of its host halo will have non-zero scatter. Consequently, this stacking results in combining the kinematics of satellite galaxies in haloes of different masses, which complicates the interpretation of the data. In this paper we present an analytical framework to model satellite kinematics, properly accounting for this scatter and for various selection effects. We show that in the presence of scatter in the halo mass-luminosity relation, the commonly used velocity dispersion of satellite galaxies can not be used to infer a unique halo mass-luminosity relation. In particular, we demonstrate that there is a degeneracy between the mean and the scatter of the halo mass-luminosity relation. We present a new technique that can break this degeneracy, and which involves measuring the velocity dispersions using two different weighting schemes: host-weighting (each central galaxy gets the same weight) and satellite-weighting (each central galaxy gets a weight proportional to its number of satellites). The ratio between the velocity dispersions obtained using these two weighting schemes is a strong function of the scatter in the halo mass-luminosity relation, and can thus be used to infer a unique relation between light and mass from the kinematics of satellite galaxies.Comment: 8 pages, 3 figures, MNRAS submitte