SED fitting with MCMC: methodology and application to large galaxy surveys

We present GalMC (Acquaviva et al 2011), our publicly available Markov Chain Monte Carlo algorithm for SED fitting, show the results obtained for a stacked sample of Lyman Alpha Emitting galaxies at z ~ 3, and discuss the dependence of the inferred SED parameters on the assumptions made in modeling the stellar populations. We also introduce SpeedyMC, a version of GalMC based on interpolation of pre-computed template libraries. While the flexibility and number of SED fitting parameters is reduced with respect to GalMC, the average running time decreases by a factor of 20,000, enabling SED fitting of each galaxy in about one second on a 2.2GHz MacBook Pro laptop, and making SpeedyMC the ideal instrument to analyze data from large photometric galaxy surveys.Comment: Proceedings of the IAU Symposium 284, "The Spectral Energy Distribution of galaxies"; typos fixed; refs adde

The Curious Case of Lyman Alpha Emitters: Growing Younger from z ~ 3 to z ~ 2?

Lyman Alpha Emitting (LAE) galaxies are thought to be progenitors of present-day L* galaxies. Clustering analyses have suggested that LAEs at z ~ 3 might evolve into LAEs at z ~ 2, but it is unclear whether the physical nature of these galaxies is compatible with this hypothesis. Several groups have investigated the properties of LAEs using spectral energy distribution (SED) fitting, but direct comparison of their results is complicated by inconsistencies in the treatment of the data and in the assumptions made in modeling the stellar populations, which are degenerate with the effects of galaxy evolution. By using the same data analysis pipeline and SED fitting software on two stacked samples of LAEs at z = 3.1 and z = 2.1, and by eliminating several systematic uncertainties that might cause a discrepancy, we determine that the physical properties of these two samples of galaxies are dramatically different. LAEs at z = 3.1 are found to be old (age ~ 1 Gyr) and metal-poor (Z < 0.2 Z_Sun), while LAEs at z = 2.1 appear to be young (age ~ 50 Myr) and metal-rich (Z > Z_Sun). The difference in the observed stellar ages makes it very unlikely that z = 3.1 LAEs evolve directly into z = 2.1 LAEs. Larger samples of galaxies, studies of individual objects and spectroscopic measurements of metallicity at these redshifts are needed to confirm this picture, which is difficult to reconcile with the effects of 1 Gyr of cosmological evolution.Comment: Minor revision, accepted for publication in ApJ

On the locality of qubit encodings of local fermionic modes

Known mappings that encode fermionic modes into a bosonic qubit system are non-local transformations. In this paper we establish that this must necessarily be the case, if the locality graph is complex enough (for example for regular 2$d$ lattices). In particular we show that, in case of exact encodings, a fully local mapping is possible if and only if the locality graph is a tree. If instead we allow ourselves to also consider operators that only act fermionically on a subspace of the qubit Hilbert space, then we show that this subspace must be composed of long range entangled states, if the locality graph contains at least two overlapping cycles. This implies, for instance, that on 2$d$ lattices there exist states that are simple from the fermionic point of view, while in any encoding require a circuit of depth at least proportional to the system size to be prepared

System Dynamics Simulation to Test Operational Policies in the Milk-Cheese Supply Chain Case study: Piar Municipality, Bolivar State, Venezuela.

With the purpose of detecting the impact that variations of demand cause in the milk-cheese supply chain, and determining how the operational policies of capacity, inventories or labor force can mitigate this impact, a system dynamics simulation model has been designed based on a survey conducted on a sample of cheese manufacturers and their links with milk farms, transportation companies and cheese distributors. This supply chain will be consolidated when a milk center that will collect the raw milk is completed. From this center, and after adequate treatment, milk will be distributed to the different cheese manufacturers in the supply chain. Managing adequately the milk-cheese supply chain represents an important challenge due to the short life of these products. Although this study was done in a region in Latin America, its results can be applicable to food supply chains by introducing some modifications. The milk-cheese supply chain in this case study contemplates three milk producers, one milk center, five cheese producers and several distributing agents. These companies operate individually under normal conditions, but they have understood that their integration in a supply chain improves the competitiveness of all its members. That is to say, the sum is greater than the parts. For its initial design a simulation software model is used in which the resources of the supply chain are optimized. Later the product of this optimization facilitates some initial values to be used in the system dynamics model in which causeeffect or influence relationships have been previously established considering the most representative variables. Finally, changes in operational policies that can reduce the level of pending orders in the supply chain are tested using other simulation software. The main contribution of this research is that it can serve as support or contribute to reduce the uncertainty in the decision making process of the supply chain management due to the speed with which individual or combined policies can be analyzed. In response to a variation of demand the most adequate policy may be selected and that can be done before the policy is implemented

Trident: A three-pronged galaxy survey. I. Lyman alpha emitting galaxies at z~2 in GOODS North

Context. Lyman alpha emitting galaxies (LAEs) are used to probe the distant universe and are therefore important for galaxy evolution studies and for providing clues to the nature of the epoch of reionization, but the exact circumstances under which Lyman alpha escapes a galaxy are still not fully understood. Aims. The Trident project is designed to simultaneously examine Lyman alpha, H-alpha and Lyman Continuum emission from galaxies at redshift z~2, thus linking together these three aspects of ionising radiation in galaxies. In this paper, we outline the strategy of this project and examine the properties of LAEs in the GOODS North field. Methods. We performed a narrowband LAE survey in GOODS North using existing and two custom made filters at the Nordic Optical Telescope with MOSCA. We use complementary broad band archival data in the field to make a careful candidate selection and perform optical to near-IR SED fitting. We also estimate far-infrared luminosities by matching our candidates to detections in Spitzer/MIPS 24{\mu}m and Herschel/PACS catalogs. Results. We find a total of 25 LAE candidates, probing mainly the bright end of the LAE luminosity function with L_Ly {\alpha} ~ 1-15e42 erg/s. They display a range of masses of ~0.5-50e9 M_solar, and average ages from a few tens of Myr to 1 Gyr when assuming a constant star formation history. The majority of our candidates also show signs of recent elevated star formation. Three candidates have counterparts in the GOODS-Herschel far-IR catalogue, with luminosities consistent with ultra-luminous infrared galaxies (ULIRGs). Conclusions. The wide range of parameters derived from our SED fitting, as well as part of our sample being detected as ULIRGs, seems to indicate that at these Lyman alpha luminosities, LAEs do not necessarily have to be young dwarfs, and that a lack of dust is not required for Lyman alpha to escape.Comment: 16 pages, 12 figures. Accepted version for publication in A&

Reflexión sobre un estudio de Senegal para el diseño de campañas de prevención de la migración de forma irregular

La iniciativa europea Proyecto Infomigra tuvo como objetivo diseñar unas campañas de información para desarrollar en Marruecos y Senegal con la intención de concienciar sobre los peligros de la migración de forma irregular. El trabajo de campo desarrollado en Senegal fue elaborado por Cruz Roja Española y contó con la colaboración de Socioestudia S.L. para el análisis e informe final. De dicho estudio, además del análisis de la información y motivaciones de las personas que mostraban su decisión de emigrar, puede extraerse una apología de la concienciación social en las investigaciones y el fomento en el campo del análisis social para un trabajo conjunto entre sociólogos/as y trabajadores/as sociales.The European initiatives of Infomigra Project had as an objective to design the information campaigns to develop in Morocco and Senegal with the intention of making awareness about the dangers of irregular migration. The field work developed in Senegal was elaborated by the Spanish Red Cross and it counted with the collaboration of Socioestudia S.L. for the analysis and final report. From this study, apart from the information analysis and the motivations that people showed about their migrating decision, it could also be extracted an apology of social awareness in the researches and the encouragement of the field for a social analysis for a collaboration between sociologists and social workers

Different Approaches for Improving the Stability of Hybrid Perovskites

Tesis por compendio[ES] Las perovskitas orgánico-inorgánicas de halogenuros son una familia de materiales estudiados en profundidad por su potencial para construir células solares de alta eficiencia y de bajo coste. Han experimentado un crecimiento exponencial de la eficiencia, pasando del 3% del PCE en 2009 a más del 25% en 2021. Pero todavía quedan retos por superar, como la estabilidad. El objetivo del trabajo es estudiar diferentes tipos de HOIP para aplicaciones fotovoltaicas, incluyendo la optimización del proceso de fabricación y la caracterización completa mediante el análisis de difracción de rayos X, microscopía electrónica de escaneo de emisión de campo, microscopio de fuerza atómica, fotoluminiscencia, UV-absorción visible, cálculo de band-gap, microscopía electrónica de transmitancia, simulación teórica y estudio de degradación de las películas. El objetivo del análisis es obtener la cristalinidad, morfología, topografía, propiedades ópticas, PCE y estabilidad de las capas. Se utilizaron varias estrategias para cumplir el objetivo del trabajo, incluyendo el dopaje con distintos compuestos, la ingeniería de extinción antisolvente y el cambio del catión "B" en la fórmula de las perovskitas; ABX3. La presente disertación se centra en el yoduro de plomo de metilamonio III (CH3NH3I3), que es conocido por presentar una absorción directa de bandgap desde la parte superior de la banda de valencia hasta la parte inferior de la banda de conducción. El bandgap puede modificarse fácilmente variante A, B y X y modularse mediante la selección adecuada de cationes mixtos. Entre las combinaciones posibles, el catión MA y el metal Pb2+ han mostrado excelentes propiedades optoelectrónicas, capas procesables en disolución a baja temperatura y potencial para una estabilidad adecuada, debido a la movilidad del portador de carga muy alta, la gran longitud de difusión de electrones y agujeros, grandes coeficientes de absorción, y bajas tasas de recombinación no radiativa. Concretamente, este doctorado se compone de cuatro artículos: - Stability Improvement of Methylammonium Lead Iodide Perovskite Thin Films by Bismuth Doping - Tetrabutylammonium (TBA)-Doped Methylammonium Lead Iodide: High Quality and Stable Perovskite Thin Films - Manufacture of High-Efficiency and Stable Lead-Free Solar Cells through Antisolvent Quenching Engineering - Investigation on the Stability and Efficiency of MAPbI3 and MASnI3 Thin Films for Solar Cells En resumen, el dopaje de bismuto mejoró la estructura cristalina de la capa absorbente de MAPbI3, mejorando las propiedades optoelectrónicas, la morfología de la superficie de las capas y la estabilidad de los dispositivos. Se estudió el dopaje con bismuto introduciendo cantidades variables de bismuto entre el 1 y el 8% en la solución inicial. Los mejores resultados se obtuvieron con un 2% de bismuto. También se analizó el dopaje con TBA introduciendo diferentes proporciones en la mezcla inicial para la síntesis de capas de MAPbI3. Observamos que un 5% de TBA reduce la densidad de agujeros en las capas y mejora la cristalinidad, mejorando la estabilidad de las capas MAPbI3. Con la proporción óptima de TBA, aumenta el tamaño del grano y la intensidad de la fotoluminiscencia, debido a la disminución de los centros de recombinación. Dado que el plomo es un elemento contaminante, sustituimos a Pb por Sn para obtener capas de MASnI3, lo que provocó un aumento del tamaño del grano y una mejora del coeficiente de absorción de la luz. Sin embargo, el MASnI3 es más inestable que el MAPbI3. Por eso, se utilizaron diferentes antisolventes en la síntesis de MASnI3. Conocida como ingeniería antisolvente, esta técnica estudia varios antisolventes. En este trabajo, el tolueno ha logrado mejorar la estabilidad de las capas de MASnI3. Utilizando un enfoque numérico mediante SCAPS-1D, se calculó que la eficiencia de los dispositivos fotovoltaicos de MASnI3 aumenta un 9,5% en comparación con los dispositivos de MAPbI3.[CAT] Les perovskites orgàniques-inorgàniques d'halogenurs són una família de materials estudiats en profunditat pel seu potencial per construir cèl·lules solars d'alta eficiència i de baix cost. Han experimentat un creixement exponencial de l'eficiència, passant del 3% del PCE el 2009 a més del 25% el 2021. Però encara queden reptes per superar, com l'estabilitat. L'objectiu d'aquest treball és estudiar diferents tipus de HOIP per a aplicacions de cèl·lules solars, incloent l'optimització del procés de fabricació i la caracterització completa mitjançant l'anàlisi de difracció de raigs X, microscòpia electrònica d'escaneig d'emissió de camp, microscopi de força atòmica, fotoluminescència, UV- absorció visible, càlcul de band-gap, microscòpia electrònica de transmitància, simulació teòrica amb SCAPS-1D i estudi de degradació de les pel·lícules. L'objectiu de l'anàlisi és obtenir la cristalinitat, morfologia, topografia, propietats òptiques, PCE i estabilitat de les capes. Es van utilitzar diferents estratègies per complir l'objectiu del treball, incloent el dopatge amb diferents compostos, l'enginyeria d'extinció antisolvent i el canvi del catió "B" en la fórmula general de les perovskites; ABX3. La present dissertació se centra en el iodur de plom de metilamoni III (CH3NH3I3), que és conegut per presentar una absorció directa de bandgap des de la part superior de la banda de valència fins a la part inferior de la banda de conducció. El bandgap es pot modificar fàcilment variant A, B i X i modular-se mitjançant la selecció adequada de cations mixts. Entre les combinacions possibles, el catió MA i el metall Pb2+ han mostrat excel·lents propietats optoelectròniques, capes processables en dissolució a baixa temperatura i potencial per a una estabilitat adequada, a causa de la mobilitat del portador de càrrega molt alta, la gran longitud de difusió d'electrons i forats, grans coeficients d'absorció, i baixes taxes de recombinació no radiativa. Concretament, aquest doctorat es compon de quatre articles: -Stability Improvement of Methylammonium Lead Iodide Perovskite Thin Films by Bismuth Doping -Tetrabutylammonium (TBA)-Doped Methylammonium Lead Iodide: High Quality and Stable Perovskite Thin Films -Manufacture of High-Efficiency and Stable Lead-Free Solar Cells through Antisolvent Quenching Engineering -Investigation on the Stability and Efficiency of MAPbI3 and MASnI3 Thin Films for Solar Cells En resum, el dopatge de bismut ha millorat l'estructura cristal·lina de la capa absorbent de MAPbI3, millorant les propietats optoelectròniques, la morfologia de la superfície de les capes i l'estabilitat dels dispositius. Es va estudiar el dopatge amb bismut introduint quantitats variables de bismut entre l'1 i el 8% en la solució inicial. Els millors resultats es van obtenir amb un 2% de bismut. També es va analitzar el dopatge amb tetrabutilamoni introduint diferents proporcions de TBA a la mescla inicial per a la síntesi de capes de MAPbI3. Observem que afegir un 5% de TBA a la mescla inicial redueix la densitat de forats a les capes i millora la cristal·linitat, millorant en l'estabilitat de les capes MAPbI3. Amb la proporció òptima de TBA, augmenta la mida del gra i la intensitat de la fotoluminescència, a causa de la disminució dels centres de recombinació. Com que el plom és un element contaminant, vam substituir Pb per Sn per obtenir capes de MASnI3, cosa que va provocar un augment de la mida del gra i una millora del coeficient d'absorció de la llum. Tanmateix, el MASnI3 és més inestable que el MAPbI3. Per això, es van utilitzar diferents antisolvents en la síntesi de MASnI3. Coneguda com a enginyeria antisolvent, aquesta tècnica estudia diversos antisolvents. En este treball, el toluè ha aconseguit millorar l'estabilitat de les capes de MASnI3. Utilitzant un enfocament numèric mitjançant SCAPS-1D, hem calculat que l'eficiència dels dispositius fotovoltaics basats en MASnI3 augmenta un 9,5% en comparació amb els dispositius de MAPbI3.[EN] Halide Organic-Inorganic Perovskites are a family of materials that have been studied in depth due to their potential for building high-efficiency and low-cost solar cells. In recent years, they have experienced exponential growth in efficiency, going from 3% of PCE in 2009 to over 25% in 2021. But still, there are numerous challenges to overcome, such as stability. The purpose of this work is to study different kinds of HOIPs for solar cell applications, including the optimization of the manufacturing process and the complete characterization by the analysis of Xray-diffraction, Field Emission Scanning Electron Microscopy, Atomic Force Microscope, photoluminescence, UV-visible absorption, band-gap calculation, Transmittance electron microscopy, theoretical simulation with SCAPS-1D, and degradation study of the films. The objective of the analysis is to obtain crystallinity, morphology, topography, optical properties, PCE, and stability of the layers. Different strategies were used to fulfil the goal of the work, including doping with different compounds, antisolvent quenching engineering, and changing the cation "B" in the general formula of perovskites; ABX3. The present dissertation is focused in methylammonium lead iodide III (CH3NH3I3), which is known for exhibiting direct bandgap absorption from the top of the valence band to the bottom of the conduction band. The bandgap can be easily modified by varying A, B, and X and modulated by the suitable selection of mixed cations. Among the possible combinations, MA cation and metal Pb2+ have exhibited excellent optoelectronic properties, low-temperature solution-processable films, and potential for appropriate stability, due to very high charge-carrier mobility, large electron and hole diffusion length, large absorption coefficients, and low nonradiative recombination rates. Specifically, this PhD is composed of four papers: - Stability Improvement of Methylammonium Lead Iodide Perovskite Thin Films by Bismuth Doping - Tetrabutylammonium (TBA)-Doped Methylammonium Lead Iodide: High Quality and Stable Perovskite Thin Films - Manufacture of High-Efficiency and Stable Lead-Free Solar Cells through Antisolvent Quenching Engineering - Investigation on the Stability and Efficiency of MAPbI3 and MASnI3 Thin Films for Solar Cells To sum up, bismuth doping has improved the crystalline structure of the absorbent layer of MAPbI3, which leads to a significant improvement in the optoelectronic properties, the morphology of the surface of the layers, and even improves the stability of the devices. Bismuth doping was studied introducing variable amounts of bismuth between 1 and 8% in the initial solution. Best results were obtained with 2% bismuth. Doping with tetrabutylammonium (TBA) was also analysed by introducing different proportions of TBA in the initial mixture for the synthesis of MAPbI3 layers. We observed that adding 5% TBA to the initial solution reduces the density of pinholes in the layers and improves crystallinity, which leads to a considerable improvement in the stability of the MAPbI3 layers. With the optimal proportion of TBA, it is possible to increase the grain size and the intensity of the photoluminescence, due to the decrease in recombination centres. Since lead is a polluting element, we substituted Pb for Sn to obtain MASnI3 layers, which led to increasing grain size and enhancing light absorption coefficient. However, MASnI3 shells are more unstable than MAPbI3 shells. To overcome this, different anti-solvents were used in the synthesis of MASnI3 shells. Known as antisolvent engineering, this technique studies several antisolvents. In our work, toluene has managed to improve the stability of the MASnI3 layers. Using a numerical approach using SCAPS-1D, we have calculated that the efficiency of photovoltaic devices (PCE) based on MASnI3 increases by 9.5% when compared to devices based on MAPbI3.Marí Guaita, J. (2022). Different Approaches for Improving the Stability of Hybrid Perovskites [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191430Compendi

Imaging polarimetry for bio applications

Polarimetric imaging is especially interesting for the fields of biology and medicine due to the capability of this technique to emphasize certain abnormalities in tissue such as cancerous growths that can interact differently with polarized light. In the present work, the construction and performance of a Mueller Matrix imaging polarimeter working in visible and near infrared spectral ranges is described enabling its reproduction. The measurement of real samples is reported, showing the virtues of this technique while presenting different calculations to extract further data from the raw measurements