Investigating the Nature of Dark Matter with Strong Gravitational Lensing

Dark matter makes up most of the mass in the Universe, and yet its particle nature remains unknown. Structure formation arguments provide a promising avenue to address this confounding mystery, as the mass and formation mechanism of the dark matter manifests in the abundance and density profiles of dark matter halos. Measurements of the halo mass function and the mass-concentration relation can therefore be cast as direct constraints on the particle nature of dark matter itself.Strong gravitational lensing by galaxies offers a unique probe of dark matter structure across cosmological distance, circumventing the use of luminous matter to trace the underlying dark matter. Observables from strong lens systems, particularly the image magnifications in quadruply-imaged quasars, probe the halo mass function directly on sub-galactic scales, below $10^8$ solar masses. In this low-mass regime, where halos become devoid of stars and gas, various dark matter models make unique predictions that lensing can constrain. In this dissertation, I present the development and implementation of a forward modeling framework that constrains any model based on dark matter theory, provided the model predicts the form of the halo mass function, and the density profile of individual halos. Using the framework I developed, my thesis presents an unprecedented constraint on the free-streaming length of dark matter that corresponds to a lower limit of $5.2 \rm{keV}$ on the mass of a thermal relic dark matter particle. In addition, I present the first constraint on the mass-concentration relation of Cold Dark Matter halos on sub-galactic scales across cosmological distance. The flexibility of the framework I developed broadens the scope of strong-lensing analyses to any structure formation model based on dark matter theory, underscoring the power of strong gravitational lensing as a probe of fundamental physics

Antitrust and the Future of Nursing: Federal Competition Policy and the Scope of Practice

TesisEn los últimos tiempos existe una tendencia mundial hacia un mayor consumo de frutas y hortalizas, motivado fundamentalmente por una creciente preocupación por una dieta más equilibrada, con menor proporción de carbohidratos, grasas y con una mayor cantidad de fibra dietética, vitaminas y minerales. Los vegetales han tenido generalmente una forma tradicional de consumo que se ha ido modificando con el surgimiento de nuevas tecnologías de procesamiento y de preservación, (Lay Ma, 1993). El yacón (Smallanthus sonchifolia) es una raíz que se domesticó en los Andes desde la época preincaica. Los centros de mayor diversidad se localizan en las zonas fronterizas de Perú con Bolivia y Ecuador. Sin embargo, su hábitat natural se extiende desde el sur de Colombia hasta el norte de Argentina (Ferro, 2006). En el caso de frutas el objetivo es entregar al mercado un producto de la mejor calidad, con el fin de ofrecer al consumidor mejor presentación, sabor, nutrientes, aceptación y que el consumidor pague por lo que se ofrece, con el fin de obtener los beneficios deseados. Los vegetales frescos deben conservarse adecuadamente hasta el momento del consumo. Las condiciones y duración del almacenamiento influyen mucho en el aspecto y valor nutritivo. Los productos vegetales al ser cosechados deben ser acondicionados a temperaturas bajas a fin de alargar su vida útil. Con el fin de evitar que durante el almacenamiento a bajas temperaturas se produzca una alteración de los alimentos se realiza una operación denominada escaldado cuyo fin principal es el de la inactivación de las enzimas responsables de la degradación. A este respecto se utiliza la peroxidasa como indicador ya que es la más termo resistente. La finalidad básica del escaldado es la inactivación enzimática, pero además se producen otros efectos deseables en el alimento: Limpieza, se quita el polvo, los gases superficiales y aparece una nueva tonalidad en el alimento; eliminación de la carga microbiana superficial; eliminación de los gases que se encuentran ocluidos en los tejidos; suavizado del material (Loannou, 2013). En el presente trabajo se estudió el efecto que tiene la temperatura de almacenamiento y el escaldado del yacón (Smallanthus sonchifolia) sobre la peroxidasa y la variación de vitamina C, con esto se realizó el estudio de estabilidad, a fin de demostrar que un producto, podría conservarse durante largos periodos de almacenamiento y así poder retener componentes nutritivos

Initial Evaluation of an Online-Based Collaborative Repository of Research to Enhance Interdisciplinary Collaboration

Sharing research data is not a new idea; the success of the Inter-University Consortium for Political and Social Science Research (ICPSR) data archive provides evidence of data sharing’s utility in the social sciences, while recent articles (Piwowar, Becich, Bilofsky & Crowley, 2008; Piwowar, Day, & Fridsma, 2007) in the biomedical literature have reiterated the importance of data sharing to the advancement of science and knowledge. The American Psychological Association’s Ethical Principles of Psychologists and Code of Conduct (APA, 2002)affirms the importance of making research data available – to the extent possible within legal and ethical boundaries – for the purposes of reanalysis by other professionals. The availability of data sets from researchers around the world in online repositories such as ICPSR and PsychData (www.zpid.de) encourages collaborative work across institutions and national boundaries. However, such large scale efforts to share data are not ideal for serving more local aims: the encouragement of intra-and interdisciplinary collaborative research withina single institution. To meet that need, this project focuses on the creation of a searchable database of existing faculty research data sets that can be accessed internally (within Pacific University) for the purposes of developing new uses of data for theses, dissertations and scholarly publications

Strong lensing constraints on primordial black holes as a dark matter candidate

Dark matter could comprise, at least in part, primordial black holes (PBH). To test this hypothesis, we present an approach to constrain the PBH mass ($M_{\rm{PBH}}$) and mass fraction ($f_{\rm{PBH}}$) from the flux ratios of quadruply imaged quasars. Our approach uses an approximate Bayesian computation (ABC) forward modeling technique to directly sample the posterior distribution of $M_{\rm{PBH}}$ and $f_{\rm{PBH}}$, while marginalizing over the subhalo mass function amplitude, spatial distribution, and the size of the lensed source. We apply our method to 11 quadruply-imaged quasars and derive a new constraint on the intermediate-mass area of PBH parameter space $10^4$M$_{\odot}<M_{\rm{PBH}}<10^6$M$_\odot$. We obtain an upper limit $f_{\mathrm{PBH}}<0.17$ (95\% C.L.). This constraint is independent of all other previously published limits.Comment: 8 pages, 7 figures, accepted to MNRA

A Dark Census: Statistically Detecting the Satellite Populations of Distant Galaxies

In the standard structure formation scenario based on the cold dark matter paradigm, galactic halos are predicted to contain a large population of dark matter subhalos. While the most massive members of the subhalo population can appear as luminous satellites and be detected in optical surveys, establishing the existence of the low mass and mostly dark subhalos has proven to be a daunting task. Galaxy-scale strong gravitational lenses have been successfully used to study mass substructures lying close to lensed images of bright background sources. However, in typical galaxy-scale lenses, the strong lensing region only covers a small projected area of the lens's dark matter halo, implying that the vast majority of subhalos cannot be directly detected in lensing observations. In this paper, we point out that this large population of dark satellites can collectively affect gravitational lensing observables, hence possibly allowing their statistical detection. Focusing on the region of the galactic halo outside the strong lensing area, we compute from first principles the statistical properties of perturbations to the gravitational time delay and position of lensed images in the presence of a mass substructure population. We find that in the standard cosmological scenario, the statistics of these lensing observables are well approximated by Gaussian distributions. The formalism developed as part of this calculation is very general and can be applied to any halo geometry and choice of subhalo mass function. Our results significantly reduce the computational cost of including a large substructure population in lens models and enable the use of Bayesian inference techniques to detect and characterize the distributed satellite population of distant lens galaxies.Comment: 21 pages + appendices, 7 figures. v2: Some derivations streamlined, extended appendices. Matches version published in PR