Fossil groups in the Millennium simulation. From the brightest to the faintest galaxies during the past 8 Gyr

We investigate the evolution of bright and faint galaxies in fossil and non-fossil groups. We used mock galaxies constructed based on the Millennium run simulation II. We identified fossil groups at redshift zero according to two different selection criteria, and then built reliable control samples of non-fossil groups that reproduce the fossil virial mass and assembly time distributions. The faint galaxies were defined as having r-band absolute magnitudes in the range [-16,-11]. We analysed the properties of the bright and faint galaxies in fossil and non-fossil groups during the past 8 Gyr. We observed that the brightest galaxy in fossil groups is typically brighter and more massive than their counterparts in control groups. Fossil groups developed their large magnitude gap between the brightest galaxies around 3.5 Gyr ago. The brightest galaxy stellar masses of all groups show a notorious increment at that time. By analysing the behaviour of the magnitude gap between the first and the second, third, and fourth ranked galaxies, we found that at earlier times, fossil groups comprised two large brightest galaxies with similar magnitudes surrounded by much fainter galaxies, while in control groups these magnitude gaps were never as large as in fossils. At early times, fossil groups in the faint population were denser than non-fossil groups, then this trend reversed, and finally they became similar at the present day. The mean number of faint galaxies in non-fossil systems increases in an almost constant rate towards later times, while this number in fossil groups reaches a plateau at $z\sim0.6$ that lasts $\sim 2$ Gyr, and then starts growing again more rapidly. The formation of fossil groups is defined at the very beginning of the groups according to their galaxy luminosity sampling, which could be determined by their merging rate at early times.Comment: 10 pages, 6 figures, 1 table. Accepted for publication in Astronomy & Astrophysic

On the properties of compact groups identified in different photometric bands

Historically, compact group catalogues vary not only in their identification algorithms and selection functions, but also in their photometric bands. Differences between compact group catalogues have been reported. However, it is difficult to assess the impact of the photometric band in these differences given the variety of identification algorithms. We used the mock lightcone built by Henriques et al. (2012) to identify and compare compact groups in three different photometric bands: $K$, $r$, and $u$. We applied the same selection functions in the three bands, and found that compact groups in the u-band look the smallest in projection, the difference between the two brightest galaxies is the largest in the K-band, while compact groups in the r-band present the lowest compactness. We also investigated the differences between samples when galaxies are selected only in one particular band (pure compact groups) and those that exist regardless the band in which galaxies were observed (common compact groups). We found that the differences between the total samples are magnified, but also some others arise: pure-r compact groups are the largest in projection; pure-u compact groups have the brightest first ranked galaxies, and the most similar two first ranked galaxies; pure-K compact groups have the highest compactness and the most different two first ranked galaxies; and common compact groups show the largest percentage of physically dense groups. Therefore, without a careful selection and identification of the samples, the characteristic features of group properties in a particular photometric band could be overshadowed.Comment: 9 pages, 3 figures, 5 tables. Accepted for publication in MNRA

Derecho al cielo

Derecho al Cielo es un proyecto de enseñanza y aprendizaje de astronomía que llevamos a cabo un grupo interdisciplinario de profesionales vinculados a la Universidad Nacional de Córdoba (UNC), junto con jóvenes en contexto de encierro punitivo. Realizamos talleres con el objetivo de promover el vínculo con el cielo y fomentar su observación como una forma de interacción con elementos fuera de la institución; generando un espacio de aprendizaje diferente, que valora los saberes cotidianos de las y los jóvenes en relación con la astronomía. Desarrollamos experiencias en el Complejo Esperanza (CE) y en el Centro Socioeducativo para Adolescentes Mujeres (CeSAM) de la ciudad de Córdoba. En este trabajo pretendemos compartir nuestra experiencia y algunos interrogantes y reflexiones que surgieron en su desarrollo, con el objetivo de contribuir en futuras actividades en contextos de encierro.“Derecho al cielo” is a teaching and learning project about astronomy, carried out by an interdisciplinary group made up of professionals related to the Universidad Nacional de Córdoba (UNC), together with young people in confinement context. We organize workshops which aim at promoting the connection with the sky and at encouraging its observation as a form of interaction with elements outside the institution. Thus, we attempt to create a different learning environment, in which the youth’s daily knowledge about astronomy could be appreciated. Currently, we develop activities in Complejo Esperanza (CE) and Centro Socioeducativo para Adolescentes Mujeres (CeSAM), both in Córdoba, Argentina. In this article, we would like to share our experience and outcomes, some questions and ideas emerging from the development of this project, with the goal of fostering future activities in confinement context.Fil: Charalambous, Carolina. 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; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Chiavassa Ferreyra, Antonio. Universidad Nacional de Cordoba. Facultad de Ciencias de la Comunicación.; ArgentinaFil: León, Malena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Humanidades. Universidad Nacional de Córdoba. Instituto de Humanidades; Argentina. Universidad Nacional de Córdoba. Facultad de Filosofía y Humanidades; ArgentinaFil: Lopez, Pablo. 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: Pereyra, Luis Alberto. 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: Fdeil, V.. Universidad Nacional de Córdoba. Facultad de Psicología; ArgentinaFil: Kanagusuku, Maria Jose. 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: Luparello, Heliana Estefanía. 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: Mari, B.. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Mudrik, Armando. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Mur, A.. Universidad Nacional de Córdoba. Facultad de Psicología; ArgentinaFil: Oio, Gabriel Andrés. 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: Rodriguez, Facundo. 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: Santucho, María Victoria. 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: Vena Valdarenas, Román Rodrigo. 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: Vives Rodriguez, Oscar Ignacio. Universidad Nacional de Córdoba. Facultad de Filosofía y Humanidades; Argentin