Creación de catálogos de galaxias simuladas para grandes relevamientos extragalácticos

Los grandes relevamientos extragalácticos han sido una pieza fundamental en nuestra comprensión de la cosmología y la formación de galaxias en las últimas décadas. Actualmente, con el advenimiento de proyectos revolucionarios del conocimiento como Euclid y el Gran Telescopio para Rastreos Sinópticos (LSST), las simulaciones cosmológicas ocupan un rol fundamental tanto en el diseño de estos relevamientos como en la interpretación de los datos que serán recolectados. Estas simulaciones son requeridas para establecer las predicciones teóricas, para generar catálogos que permitan cuantificar efectos observacionales sistemáticos y de selección, para realizar análisis de datos y para optimizar las estrategias de observación. Entre los tipos de simulaciones utilizadas para comprender la evolución de las galaxias, los modelos semianalíticos de formación y evolución de galaxias adquieren una importancia estratégica dada su ventaja en tiempo de cálculo y predictibilidad teórica. En esta Tesis nos enfocamos en el código semianalítico SAG, el cual hemos modificado y adaptado para poder permitir generar catálogos de galaxias de amplia envergadura, así como también hemos estudiado y mejorado aspectos particulares del modelo físico que nos permiten obtener poblaciones de galaxias con propiedades más consistentes con las observadas. Específicamente, hemos introducido cambios técnicos globales en el código que incluyen: una adaptación a nuevos tipos de simulaciones con formato estándar, estrategias de optimización, rendimiento y paralelización para analizar grandes entradas de datos en supercomputadoras. Detallamos comparaciones entre las diferentes versiones del modelo, así como análisis del algoritmo del mismo y estadísticas de rendimiento. También nos hemos enfocado en algunos tratamientos evolutivos aplicados a las galaxias satélites. Analizamos el método de integración de órbitas de las galaxias satélites huérfanas mediante el ajuste de la tasa de fusiones de la población de galaxias, implementamos correcciones para considerar la periodicidad de las simulaciones en esta integración, y desarrollamos un ajuste empírico para modelar la pérdida de material de las galaxias satélites debido a la presión de barrido ejercida por el medio. Finalmente, utilizamos todos los cambios y mejoras anteriores para crear un catálogo de galaxias de gran envergadura aplicando el código SAG sobre la simulación pública MDPL2 del grupo MultiDark, en contexto de un proyecto de colaboración. Este catálogo será publicado mediante una base de datos abierta en línea. Detallamos todo el análisis necesario realizado para construir este catálogo, así como los resultados intermedios y las estadísticas generales de cálculo. Incluimos también análisis de los modelos utilizados en cada etapa de la construcción del catálogo final. El catálogo resultante consiste en una población de galaxias simuladas cuyas propiedades cumplen una serie de restricciones fundamentales basadas en observaciones de relevamientos extragalácticos y muestra predicciones consistentes. Esta muestra se compone de aproximadamente 194 millones de galaxias a z=0, y considera un total de 125 instantáneas en su historia evolutiva.Facultad de Ciencias Astronómicas y Geofísica

nIFTy cosmology: comparison of galaxy formation models

We present a comparison of 14 galaxy formation models: 12 different semi-analytical models and 2 halo occupation distribution models for galaxy formation based upon the same cosmological simulation and merger tree information derived from it. The participating codes have proven to be very successful in their own right but they have all been calibrated independently using various observational data sets, stellar models, and merger trees. In this paper, we apply them without recalibration and this leads to a wide variety of predictions for the stellar mass function, specific star formation rates, stellar-to-halo mass ratios, and the abundance of orphan galaxies. The scatter is much larger than seen in previous comparison studies primarily because the codes have been used outside of their native environment within which they are well tested and calibrated. The purpose of the 'nIFTy comparison of galaxy formation models' is to bring together as many different galaxy formation modellers as possible and to investigate a common approach to model calibration. This paper provides a unified description for all participating models and presents the initial, uncalibrated comparison as a baseline for our future studies where we will develop a common calibration framework and address the extent to which that reduces the scatter in the model predictions seen here.La lista completa de autores que integran el documento puede consultarse en el archivo.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

nIFTy cosmology: comparison of galaxy formation models

We present a comparison of 14 galaxy formation models: 12 different semi-analytical models and 2 halo occupation distribution models for galaxy formation based upon the same cosmological simulation and merger tree information derived from it. The participating codes have proven to be very successful in their own right but they have all been calibrated independently using various observational data sets, stellar models, and merger trees. In this paper, we apply them without recalibration and this leads to a wide variety of predictions for the stellar mass function, specific star formation rates, stellar-to-halo mass ratios, and the abundance of orphan galaxies. The scatter is much larger than seen in previous comparison studies primarily because the codes have been used outside of their native environment within which they are well tested and calibrated. The purpose of the 'nIFTy comparison of galaxy formation models' is to bring together as many different galaxy formation modellers as possible and to investigate a common approach to model calibration. This paper provides a unified description for all participating models and presents the initial, uncalibrated comparison as a baseline for our future studies where we will develop a common calibration framework and address the extent to which that reduces the scatter in the model predictions seen here.La lista completa de autores que integran el documento puede consultarse en el archivo.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Siblings, friends and acquaintances: testing galaxy association methods

In order to constraint the limitations of association methods applied to galaxy surveys, we analysed the catalogue of halos at z=0 of a cosmological simulation, trying to reproduce the limitations that an observational survey deal with. We focused in the percolation method, usually called Friends of Friends method, commonly used in literature. The analysis was carried on the dark matter cosmological simulation MDPL2, from the Multidark project. Results point to a large fraction of contaminants for massive halos in high density environments. Thresholds in the association parameters and the subsequent analysis of observational properties can mitigate the occurrence of fake positives. The use of tests for substructures can also be efficient in particular cases.Facultad de Ciencias Astronómicas y Geofísica

Semi-analytic galaxies - II. Revealing the role of environmental and mass quenching in galaxy formation

We use the semi-analytic model of galaxy formation sag to study the relevance of mass and environmental quenching on satellite galaxies. We find that environmental processes dominate the star formation (SF) quenching of low-mass satellites (M? . 1010.5 M ), whereas high-mass galaxies typically quench as centrals. High-mass galaxies that remain actively forming stars while being accreted are found to be mainly affected by mass quenching after their first infall. For a given stellar mass, our model predicts SF quenching to be less efficient in low-mass haloes both before and after infall, in contradiction with common interpretations of observational data. Our model supports a two-stage scenario to explain the SF quenching. Initially, the SF of satellites resembles that of centrals until the gas cooling rate is reduced to approximately half its value at infall. Then, the SF fades through secular processes that exhaust the cold gas reservoir. This reservoir is not replenished efficiently due to the action of either ram-pressure stripping (RPS) of the hot gas in low-mass satellites, or feedback from the active galactic nucleus (AGN) in high-mass satellites. The delay times for the onset of SF quenching are found to range from ≈ 3 Gyr to ≈ 1 Gyr for low-mass (M? ≈ 1010 M ) and high-mass (M? ≈ 1011 M ) satellites, respectively. SF fades in ≈ 1.5 Gyr, largely independent of stellar mass. We find that the SF quenching of lowmass satellites supports the so-called delay-then-rapid quenching scenario. However, the SF history of z = 0 passive satellites of any stellar mass is better described by a delay-then-fade quenching scenario.Fil: Cora, Sofia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Observatorio Astronómico de La Plata - Sede Central; ArgentinaFil: Hough, Tomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Observatorio Astronómico de La Plata - Sede Central; ArgentinaFil: Vega Martínez, Cristian Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Orsi, Álvaro A.. Centro de Estudios de Física del Cosmos de Aragón; Españ

A new analytic ram pressure profile for satellite galaxies

We present a new analytic fitting profile to model the ram pressure exerted over satellite galaxies on different environments and epochs. The profile is built using the information of the gas particle distribution in hydrodynamical simulations of groups and clusters of galaxies to measure the ram pressure directly. We show that predictions obtained by a previously introduced β-profile model can not consistently reproduce the dependence of the ram pressure on halocentric distance and redshift for a given halo mass. It features a systematic underestimation of the predicted ram pressure at high redshifts (z > 1.5), which increases towards the central regions of the haloes and it is independent of halo mass, reaching differences larger than two decades for satellites at r 1.5).Fil: Vega Martínez, Cristian Antonio. Universidad de La Serena; ChileFil: Gómez, Facundo Ariel. Universidad de La Serena; ChileFil: Cora, Sofia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Hough, Tomas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentin

DESCQA: An Automated Validation Framework for Synthetic Sky Catalogs

The use of high-quality simulated sky catalogs is essential for the success of cosmological surveys. The catalogs have diverse applications, such as investigating signatures of fundamental physics in cosmological observables, understanding the effect of systematic uncertainties on measured signals and testing mitigation strategies for reducing these uncertainties, aiding analysis pipeline development and testing, and survey strategy optimization. The list of applications is growing with improvements in the quality of the catalogs and the details that they can provide. Given the importance of simulated catalogs, it is critical to provide rigorous validation protocols that enable both catalog providers and users to assess the quality of the catalogs in a straightforward and comprehensive way. For this purpose, we have developed the DESCQA framework for the Large Synoptic Survey Telescope Dark Energy Science Collaboration as well as for the broader community. The goal of DESCQA is to enable the inspection, validation, and comparison of an inhomogeneous set of synthetic catalogs via the provision of a common interface within an automated framework. In this paper, we present the design concept and first implementation of DESCQA. In order to establish and demonstrate its full functionality we use a set of interim catalogs and validation tests. We highlight several important aspects, both technical and scientific, that require thoughtful consideration when designing a validation framework, including validation metrics and how these metrics impose requirements on the synthetic sky catalogs.La lista completa de autores se encuentra en el documento.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Semi-analytic galaxies : III. The impact of supernova feedback on the mass-metallicity relation

We use the semi-analytic model (SAM) of galaxy formation and evolution SAG coupled with the MULTIDARK simulation MDPL2 to study the evolution of the stellar - gas metallicity relation of galaxies (MZR). We test several implementations of the dependence of the mass loading due to supernovae (SNe).We find that no evolution in the normalization of the MZR is obtained unless we introduce an explicit scaling of the reheated and ejected mass with redshift as (1 + z)β. The latter is in agreement with results from the FIRE simulations, and it should encompass small-scale properties of the interstellar medium varying over time, which are not captured in SAMs, as well as other energy sources in addition to SNe. Increasing β leads to stronger evolution of the MZR normalization; β = 1.9 reproduces the observed MZR in the range 0 < z < 3.5. A stronger redshift dependence of outflows reduces the levels of star formation at earlier epochs with the consequent decrease of metal production. This leads to a slower increase of the gas metallicity compared to the stellar mass build-up. The cold gas can be contaminated either by receiving a direct injection of the material recycled by stellar winds and SNe or by gas cooling. The relative role of each process for a given stellar mass depends on the criterion adopted to regulate the fate of the recycled material. However, modifying the metal loading of the outflows has mild impact on the zero-point evolution and does not affect our conclusions.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

nIFTy cosmology: comparison of galaxy formation models

We present a comparison of 14 galaxy formation models: 12 different semi-analytical models and 2 halo occupation distribution models for galaxy formation based upon the same cosmological simulation and merger tree information derived from it. The participating codes have proven to be very successful in their own right but they have all been calibrated independently using various observational data sets, stellar models, and merger trees. In this paper, we apply them without recalibration and this leads to a wide variety of predictions for the stellar mass function, specific star formation rates, stellar-to-halo mass ratios, and the abundance of orphan galaxies. The scatter is much larger than seen in previous comparison studies primarily because the codes have been used outside of their native environment within which they are well tested and calibrated. The purpose of the 'nIFTy comparison of galaxy formation models' is to bring together as many different galaxy formation modellers as possible and to investigate a common approach to model calibration. This paper provides a unified description for all participating models and presents the initial, uncalibrated comparison as a baseline for our future studies where we will develop a common calibration framework and address the extent to which that reduces the scatter in the model predictions seen here.La lista completa de autores que integran el documento puede consultarse en el archivo.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

ROGER: Reconstructing orbits of galaxies in extreme regions using machine learning techniques

We present the ROGER (Reconstructing Orbits of Galaxies in Extreme Regions) code, which uses three different machine learning techniques to classify galaxies in, and around, clusters, according to their projected phase-space position. We use a sample of 34 massive, M200 > 1015h-1M⊙, galaxy clusters in the MultiDark Planck 2 (MDLP2) simulation at redshift zero. We select all galaxies with stellar mass M∗ ≥ 108.5h-1M⊙, as computed by the semi-analytic model of galaxy formation SAG, that are located in, and in the vicinity of, these clusters and classify them according to their orbits. We train ROGER to retrieve the original classification of the galaxies from their projected phase-space positions. For each galaxy, ROGER gives as output the probability of being a cluster galaxy, a galaxy that has recently fallen into a cluster, a backsplash galaxy, an infalling galaxy, or an interloper. We discuss the performance of the machine learning methods and potential uses of our code. Among the different methods explored, we find the K-Nearest Neighbours algorithm achieves the best performance.Fil: de Los Rios, Martín Emilio. South American Institute For Fundamental Research.; BrasilFil: Martínez, Héctor J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Coenda, Valeria. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Muriel, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Ruiz, Andrés Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Vega Martínez, Cristian Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Cora, Sofia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentin