César A. Caretta

HIFLUGCS: galaxy cluster scaling relations between X-ray luminosity, gas mass, cluster radius, and velocity dispersion

We present relations between X-ray luminosity and velocity dispersion (L ― σ), X-ray luminosity and gas mass (L ― Mg as ), and cluster radius and velocity dispersion (r 500 ― σ) for 62 galaxy clusters in the HIFLUGCS, an X-ray flux-limited sample minimizing bias toward any cluster morphology. Our analysis in total is based on ∼ 1.3 Ms of clean X-ray XMM-Newton data and 13439 cluster member galaxies with redshifts. Cool cores are among the major contributors to the scatter in the L ― σ relation. When the cool-core-corrected X-ray luminosity is used the intrinsic scatter decreases to 0.27 dex. Even after the X-ray luminosity is corrected for the cool core, the scatter caused by the presence of cool cores dominates for the low-mass systems. The scatter caused by the non-cool-core clusters does not strongly depend on the mass range, and becomes dominant in the high-mass regime. The observed L ― σ relation agrees with the self-similar prediction, matches that of a simulated sample with AGN feedback disregarding six clusters with <45 cluster members with spectroscopic redshifts, and shows a common trend of increasing scatter toward the low-mass end, i.e., systems with σ < 500 km s ―1 . A comparison of observations with simulations indicates an AGN-feedback-driven impact in the low-mass regime. The best fits to the L - Mg as relations for the disturbed clusters and undisturbed clusters in the observational sample closely match those of the simulated samples with and without AGN feedback, respectively. This suggests that one main cause of the scatter is AGN activity providing feedback in different phases, e.g. during a feedback cycle. The slope and scatter in the observed r 500 ― σ relation is similar to that of the simulated sample with AGN feedback except for a small offset but still within the scatter.

Impact of hydrocarbons, PCBs and heavy metals on bacterial communities in Lerma River, Salamanca, Mexico: Investigation of hydrocarbon degradation potential.

Freshwater contamination usually comes from runoff water or direct wastewater discharges to the environment. This paper presents a case study which reveals the impact of these types of contamination on the sediment bacterial population. A small stretch of Lerma River Basin, heavily impacted by industrial activities and urban wastewater release, was studied. Due to industrial inputs, the sediments are characterized by strong hydrocarbon concentrations, ranging from 2 935 to 28 430μg·kg(-1) of total polyaromatic hydrocarbons (PAHs). These sediments are also impacted by heavy metals (e.g., 9.6μg·kg(-1) of Cd and 246μg·kg(-1) of Cu, about 8 times the maximum recommended values for environmental samples) and polychlorinated biphenyls (ranging from 54 to 123μg·kg(-1) of total PCBs). The bacterial diversity on 6 sediment samples, taken from upstream to downstream of the main industrial and urban contamination sources, was assessed through TRFLP. Even though the high PAH concentrations are hazardous to aquatic life, they are not the only factor driving bacterial community composition in this ecosystem. Urban discharges, leading to hypoxia and low pH, also strongly influenced bacterial community structure. The bacterial bioprospection of these samples, using PAH as unique carbon source, yielded 8 hydrocarbonoclastic strains. By sequencing the 16S rDNA gene, these were identified as similar to Mycobacterium goodii, Pseudomonas aeruginosa, Pseudomonas lundensis or Aeromonas veronii. These strains showed high capacity to degrade naphthalene (between 92 and 100% at 200mg·L(-1)), pyrene (up to 72% at 100mg·L(-1)) and/or fluoranthene (52% at 50mg·L(-1)) as their only carbon source on in vitro experiments. These hydrocarbonoclastic bacteria were detected even in the samples upstream of the city of Salamanca, suggesting chronical contamination, already in place longer before. Such microorganisms are clearly potential candidates for hydrocarbon degradation in the treatment of oil discharges.

Galaxy evolution in Abell 85: I. Cluster substructure and environmental effects on the blue galaxy population

In this series of papers we explore the evolution of late-type galaxies in the rich cluster Abell 85. In this first paper we revisit the complex dynamical state of A 85 by using independent methods. First, we analyze the galaxy redshift distribution towards A 85 in the whole range 0−40 000 km s −1 , and determine the mean redshifts of the background clusters A 87 and A 89, very close in projection to A 85. Then we search for substructures in A 85 by considering the 2D galaxy distribution of its members (13 000−20 000 km s −1 )a nd by applying the kinematical 3D Δ-test to both projected positions and radial velocities. This clearly reveals several substructures: one close to the cluster core and three more projected towards the southeast, along the region where an X-ray filament has been extensively studied. We also analyse the distribution of the brightest blue galaxies across a major fraction of the cluster volume, considering if they are gas-rich or poor. We report a very asymmetric distribution of the blue member galaxies, with most of them to the east and southeast, namely in the region joining the core of A 85 to its farthest substructure in this direction – dubbed the SE clump. By matching our sample of bright blue member galaxies with H i detections reported in the literature, we identify gas-rich and gas-poor ones. As expected, the H i-rich blue galaxies follow the same trend as the parent sample, with most of them projected on the eastern side of the cluster as well. Interestingly no blue objects have been detected in H i up to a projected radius of 2 Mpc in this zone. We finally estimate the ram pressure stripping exerted by the intra-cluster medium as a function of the projected distance from A 85, in order to quantify how important this mechanism might be in sweeping the gas out of the infalling spirals.

Hexavalent chromium reduction by bacterial consortia and pure strains from an alkaline industrial effluent

Aims:  To characterize the bacterial consortia and isolates selected for their role in hexavalent chromium removal by adsorption and reduction.

Effect of cuo nanoparticles over isolated bacterial strains from agricultural soil

The increased use of the nanoparticles (NPs) on several processes is notorious. In contrast the ecotoxicological effects of NPs have been scarcely studied. The main current researches are related to the oxide metallic NPs. In the present work, fifty-six bacterial strains were isolated from soil, comprising 17 different OTUs distributed into 3 classes: Bacilli (36 strains), Flavobacteria (2 strains), and Gammaproteobacteria (18 strains). Copper oxide nanoparticles (CuONPs) were synthesized using a process of chemical precipitation. The obtained CuONPs have a spherical shape and primary size less than 17 nm. Twenty-one strains were used to evaluate the cytotoxicity of CuONPs and 11 of these strains showed high sensibility. Among those 11 strains, 4 (Brevibacillus laterosporus strain CSS8, Chryseobacterium indoltheticum strain CSA28, and Pantoea ananatis strains CSA34 and CSA35) were selected to determine the kind of damage produced. The CuONPs toxic effect was observed at expositions over 25mgċL-1 and the damage to cell membrane above 160mgċL-1. The electron microscopy showed the formation of cavities, holes, membrane degradation, blebs, cellular collapse, and lysis. These toxic effects may probably be due to the ions interaction, the oxide-reduction reactions, and the generation of reactive species.

Evidence of turbulence-like universality in the formation of galaxy-sized dark matter haloes

Context. Although the theoretical understanding of the nonlinear gravitational clustering has greatly advanced in the last dec ades, in particular by the outstanding improvement on numerical N-body simulations, the physics behind this process is not fully elucidate d. Aims. The main goal of this work is the study of the possibility of a turbulent-like physical process in the formation of structu res, galaxies and clusters of galaxies, by the action of gravity alone. Methods. We use simulation data from the Virgo Consortium, in ten redshift snapshots (from 0 to 10). From this we identify galaxy-sized and cluster-sized dark matter haloes, by using a FoF algorithm and applying a boundedness criteria, and study the gravitational potential energy spectra. Results. We find that the galaxy-sized haloes energy spectrum follows closely a Kolmogorov’s power law, similar to the behaviour o f dynamically turbulent processes in fluids. Conclusions. This means that the gravitational clustering of dark matter may admit a turbulent-like representation.

Extreme event dynamics in the formation of galaxy-sized dark matter structures

The search for turbulent-like patterns in nonlinear gravitational clustering has recently advanced due to N-body simulations based on the cold dark matter scenario. In this work we present a computational statistical analysis of the formation of galaxy halos by gravitational collapse in N-body simulation from the Virgo Consortium Data. We find that rescaled data points of gravitational energy for different redshifts collapse into similar patterns, well approximated by a Generalized Extreme Value (GEV) distribution. Once similar statistical behavior was found for chaotic advection, this result is discussed in the context of non-dissipative turbulent-like behavior. From our analysis the unstable gravity field itself behaves as a chaotic advecting flow where the particles (galaxies) can be interpreted as turbulent tracers.

Impact of the Nanomaterials on Soil Bacterial Biodiversity

In this chapter we first review some characteristics of the nanoparticles and nanomaterial. We will explain their definition, main properties, applications, availability, and toxicity to the prokaryotes. Then, we define the soil as a very complex ecosystem and consider some of its physicochemical-biological properties, in order to discuss the action of the nanoparticles and nanomaterials present. We discuss the use of these substances in agriculture and their ecotoxicological effect. We also examine methodologies and techniques currently used for measuring their interaction with microorganisms and microorganism communities and argue that they are indeed potential contaminants. Since their use, especially in agrochemicals, has largely grown in the last years, and there is still not enough data to support the necessary decisions in local and international regulations concerning human health and the environment, it is urgent to develop and extend this kind of studies.

The XXL Survey. XXVI. Double irony in XXL-North. A tale of two radio galaxies in a supercluster at z = 0.14

Aims. We show how the XXL multiwavelength survey can be used to shed light on radio galaxies and their environment. Methods. Two prominent radio galaxies were identified in a visual examination of the mosaic of XXL-North obtained with the Giant Metrewave Radio Telescope at 610 MHz. Counterparts were searched for in other bands. Spectroscopic redshifts from the GAMA database were used to identify clusters and/or groups of galaxies, estimate their masses with the caustic method, and quantify anisotropies in the surrounding galaxy distribution via a Fourier analysis. Results. Both radio galaxies are of FR I type and are hosted by early-type galaxies at a redshift of 0.138. The first radio source, named the Exemplar, has a physical extent of ∼400 kpc; it is located in the cluster XLSSC 112, which has a temperature of ∼2 keV, a total mass of ∼1014 Mo, and resides in an XXL supercluster with eight known members. The second source, named the Double Irony, is a giant radio galaxy with a total length of about 1.1 Mpc. Its core coincides with a cataloged point-like X-ray source, but no extended X-ray emission from a surrounding galaxy cluster was detected. However, from the optical data we determined that the host is the brightest galaxy in a group that is younger, less virialized, and less massive than the Exemplars cluster. A friends-of-friends analysis showed that the Double Ironys group is a member of the same supercluster as the Exemplar. There are indications that the jets and plumes of the Double Irony have been deflected by gas associated with the surrounding galaxy distribution. Another overdensity of galaxies (the tenth) containing a radio galaxy was found to be associated with the supercluster. Conclusions. Radio Galaxies can be used to find galaxy clusters/groups that are below the current sensitivity of X-ray surveys.

The Venus Transit, the Mayan Calendar and Astronomy Education in Guanajuato, Mexico

In this work we present two aspects of the Astronomy education activities carried out in 2012 by a multidisciplinary group at Universidad de Guanajuato, including specialists in Astronomy, Social Sciences and Environmental Engineering. The first program linked the Venus Transit, occurred in June 2012, with a national campaign of vulgarization of both modern and ancient (Mayan) Astronomy. Professional astronomers all around the country took advantage of the recent myth linked to the end of a large Mayan calendar cycle (13 baktuns , or some 5125 years) happening, after certain authors, in December 2012. In Guanajuato, the Astronomy Department organized live observations of the Venus Transit at two different locations, and complemented with conferences about astronomical events and the fake predictions of disasters linked to the “end“ of the Mayan calendar. This program was very successful not only in Guanajuato but throughout the country, with several thousands of people attending live observations, conferences, expositions, etc.