We study the role of group infall in the assembly and dynamics of galaxy clusters in ΛCDM. We select 10 clusters with virial mass M200 ∼ 1014$\rm M_\odot$from the cosmological hydrodynamical simulation Illustris and follow their galaxies with stellar mass M⋆ ≥ 1.5 × 108$\rm M_\odot$. A median of $\sim 38\%$ of surviving galaxies at z = 0 are accreted as part of groups and did not infall directly from the field, albeit with significant cluster-to-cluster scatter. The evolution of these galaxy associations is quick, with observational signatures of their common origin eroding rapidly in 1-3 Gyr after infall. Substructure plays a dominant role in fostering the conditions for galaxy mergers to happen, even within the cluster environment. Integrated over time, we identify (per cluster) an average of 17 ± 9 mergers that occur in infalling galaxy associations, of which 7 ± 3 occur well within the virial radius of their cluster hosts. The number of mergers shows large dispersion from cluster to cluster, with our most massive system having 42 mergers above our mass cut-off. These mergers, which are typically gas rich for dwarfs and a combination of gas rich and gas poor for M⋆ ∼ 1011$\rm M_\odot$, may contribute significantly within ΛCDM to the formation of specific morphologies, such as lenticulars (S0) and blue compact dwarfs in groups and clusters.
Tidal features in the outskirts of galaxies yield unique information about their past interactions and are a key prediction of the hierarchical structure formation paradigm. The Vera C. Rubin Observatory is poised to deliver deep observations for potentially of millions of objects with visible tidal features, but the inference of galaxy interaction histories from such features is not straightforward. Utilising automated techniques and human visual classification in conjunction with realistic mock images produced using the NewHorizon cosmological simulation, we investigate the nature, frequency and visibility of tidal features and debris across a range of environments and stellar masses. In our simulated sample, around 80 per cent of the flux in the tidal features around Milky Way or greater mass galaxies is detected at the 10-year depth of the Legacy Survey of Space and Time (30 − 31 mag arcsec−2), falling to 60 per cent assuming a shallower final depth of 29.5 mag arcsec−2. The fraction of total flux found in tidal features increases towards higher masses, rising to 10 per cent for the most massive objects in our sample (M⋆ ∼ 1011.5 M⊙). When observed at sufficient depth, such objects frequently exhibit many distinct tidal features with complex shapes. The interpretation and characterisation of such features varies significantly with image depth and object orientation, introducing significant biases in their classification. Assuming the data reduction pipeline is properly optimised, we expect the Rubin Observatory to be capable of recovering much of the flux found in the outskirts of Milky Way mass galaxies, even at intermediate redshifts (z < 0.2).
We study the formation of ultra-diffuse galaxies (UDGs) using the cosmological hydrodynamical simulation TNG50 of the Illustris-TNG suite. We define UDGs as dwarf galaxies in the stellar mass range $\rm {7.5 \le log (M_{\star } / M_{\odot }) \le 9 }$ that are in the $5\%$ most extended tail of the simulated mass-size relation. This results in a sample of UDGs with half-mass radii $\rm {r_{h \star } \gtrsim 2 \ kpc}$ and surface brightness between $\rm {24.5}$ and $\rm {28 \ mag \ arcsec^{-2}}$, similar to definitions of UDGs in observations. The large cosmological volume in TNG50 allows for a comparison of UDGs properties in different environments, from the field to galaxy clusters with virial mass $\rm {M_{200} \sim 2 \times 10^{14} ~ M_{\odot }}$. All UDGs in our sample have dwarf-mass haloes ($\rm {M_{200}\sim 10^{11} ~ M_{\odot } }$) and show the same environmental trends as normal dwarfs: field UDGs are star-forming and blue while satellite UDGs are typically quiescent and red. The TNG50 simulation predicts UDGs that populate preferentially higher spin haloes and more massive haloes at fixed $\rm {M_{\star }}$ compared to non-UDG dwarfs. This applies also to most satellite UDGs, which are actually “born” UDGs in the field and infall into groups and clusters without significant changes to their size. We find, however, a small subset of satellite UDGs ($\lesssim 10 \%$) with present-day stellar size a factor ≥1.5 larger than at infall, confirming that tidal effects, particularly in the lower mass dwarfs, are also a viable formation mechanism for some of these dwarfs, although subdominant in this simulation.
Elliptical (E) and spiral (S) galaxies follow tight, but different, scaling laws that link their stellar masses, radii, and characteristic velocities. Mass and velocity, for example, scale tightly in spirals with little dependence on galaxy radius (the ‘Tully-Fisher relation’; TFR). On the other hand, ellipticals appear to trace a 2D surface in size-mass-velocity space (the ‘Fundamental Plane’; FP). Over the years, a number of studies have attempted to understand these empirical relations, usually in terms of variations of the virial theorem for E galaxies and in terms of the scaling relations of dark matter halos for spirals. We use Lambda cold dark matter (ΛCDM) cosmological hydrodynamical simulations to show that the scaling relations of both ellipticals and spirals arise as the result of (i) a tight galaxy mass–dark halo mass relation and (ii) the self-similar mass profile of cold dark matter halos. In this interpretation, E and S galaxies of a given stellar mass inhabit halos of similar masses, and their different scaling laws result from the varying amounts of dark matter enclosed within their luminous radii. This scenario suggests a new galaxy distance indicator applicable to galaxies of all morphologies and provides simple and intuitive explanations for long-standing puzzles, such as why the TFR is independent of surface brightness, or what causes the ‘tilt’ in the FP. Our results provide strong support for the predictions of ΛCDM in the strongly non-linear regime, as well as guidance for further improvements to cosmological simulations of galaxy formation.
Resumen. Las representaciones esquemáticas del abrigo de Laja Alta (Jimena de la Frontera, España) son el testimonio más claro de la existencia en la antigüedad de embarcaciones a vela en el Mediterráneo occidental. Mayoritariamente se han venido adscribiendo al I o finales del II milenio a.C. Este artículo ofrece nuevos calcos y datos para una mejor comprensión del conjunto de motivos del abrigo. Entre los resultados obtenidos planteamos cuestionar la anterior cronología. Las dataciones absolutas confirman su frecuentación entre el IV-III milenio a.C., durante el Neolítico Reciente y Calcolítico del sur de Iberia. Una época de importantes transformaciones en la región. Además, el resto de resultados obtenidos son leídos en términos de datación relativa (tipos de motivos, su contexto cultural, análisis de pigmentos mediante reflectancia óptica y superposición de figuras), no apartándose de las dataciones obtenidas. La distribución espacial de las figuras indica que los barcos ocupan el centro de la cavidad, son el tema principal de Laja Alta, el resto está determinado por la escena naval. Esta conclusión tiene implicaciones históricas para la transferencia de tecnologías, bienes e ideas que dieron forma a las sociedades del Neolítico Reciente y la Edad del Cobre de Europa occidental y norte de África.Abstract. The Laja Alta rock shelter paintings (Jimena de la Frontera, Spain) are the clearest existing testimony of sailing vessels from ancient times in the western Mediterranean. The majority opinion of the research has dated the naval scene in the first or the end of the second mill. BC. This article offers new reproductions and data for a better understanding of the figures represented. Based on the results obtained, we propose a different hypothesis. The absolute dates confirm that the rock shelter was used in the IV-III mill. cal. BC., the Late Neolithic and Copper Age. It was a time of important community transformations. Besides, others datas (types of figures, cultural context, pigment analysis by optical reflectance and superposition of figures) do not deviate from the results dates. The topographical distribution indicates that the boats occupy a central position in the rock shelter. Thus, the boats are the main theme of the paintings of Laja Alta and the rest of the motifs are determined by the naval scene. This conclusion has important historical implications for the transfer of technologies, goods and ideas that shaped the societies of the Late Neolithic and Copper Age of the Western Europe and North Africa.
Introducción: en la investigación se analiza las diferencias en los resultados de los Exámenes de Calidad de Educación Superior Saber Pro de los estudiantes de la Licenciatura en Educación Básica con énfasis en Matemáticas, Humanidades y Lengua Castellana. Metodología: fueron descargadas bases de datos de los resultados de las pruebas del programa, desde el sistema FTP-ICFES y se operó con los puntajes numéricos, el nombre de la carrera, la modalidad de educación a distancia con apoyo virtual de los estudiantes de la Licenciatura en Educación Básica, dando paso a una investigación de tipo descriptivo. Resultados: en la investigación se presenta que no existen brechas significativas en los resultados de los módulos de Componentes Genéricos, puesto que en la mayoría de ellos se está por encima del promedio del grupo de referencia en Educación, y por debajo del promedio nacional. Conclusiones: se puede constatar las diferencias entre los resultados de los estudiantes del programa según los módulos establecidos, y se hace necesario reformular, a través de estrategias pedagógicas, metodológicas y didácticas, la formación de los Licenciados en Educación Básica, con miras a fortalecer las competencias relacionadas con el enseñar, evaluar y formar, propias de los licenciados.
ResumenLa investigación se centra en el análisis de los resultados de las pruebas estandarizadas de Colombia Saber Pro, que presentan los estudiantes de la Licenciatura en Educación Básica como requisito de grado. Se descargaron bases de datos de los resultados de las pruebas, desde la página web www.icfesinteractivo. gov.co y se operó con los puntajes numéricos de los estudiantes del programa de Licenciatura en Educación Básica, que se ofrece en modalidad a distancia. Se evidencia que los estudiantes que presentaron las pruebas Saber Pro en el año 2013 fueron objeto de evaluación homogénea y estándar en lo siguiente: Competencias 1 Universidad Pedagógica y Tecnológica de Colombia. Artículo original de investigación Ciudadanas, Comunicación Escrita, Inglés, Lectura Crítica, Razonamiento Cuantitativo, demostrando que en algunas competencias y componentes se encuentran por debajo del grupo nacional. Las pruebas Saber Pro no son objeto de compromiso serio por parte de los estudiantes, al ser consideradas como un requisito de grado y no como una posibilidad de mejoramiento en la calidad de la educación superior. Se considera que el examen va por un lado y por otro diferente van los estudiantes y la educación sin la remota posibilidad de llegar un punto de convergencia. Palabras clave: Colombia; Competencias; Licenciatura en Educación Básica; Políticas en Educación; Pruebas Estandarizadas; Saber Pro. AbstractThis paper analyses the results obtained by students of a bachelor's degree in primary education in Saber Pro standardized tests in Colombia, which were taken as a graduation requirement. The data bases containing the results of the tests were downloaded from the website www.icfesinteractivo.gov.co and scores obtained by students of the bachelor's degree in primary education (distance mode) were used. The students who took the Saber Pro tests in 2013 were homogeneously and standardly assessed in the following: citizen competences, written communication, English, critical
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