86,785 research outputs found
A survey of the thermal and non-thermal properties of cosmic filaments
No full textIn this paper, we exploit a large suite of ENZO cosmological magneto-hydrodynamical simula- tions adopting uniform mesh resolution, to investigate the properties of cosmic filaments under different baryonic physics and magnetogenesis scenarios. We exploit a isovolume based algo- rithm to identify filaments and determine their attributes from the continuous distribution of gas mass density in the simulated volumes. The global (e.g. mass, size, mean temperature and magnetic field strength, enclosed baryon fraction) and internal (e.g. density, temperature, ve- locity and magnetic field profiles) properties of filaments in our volume are calculated across almost four orders of magnitude in mass. The inclusion of variations in non-gravitational physical processes (radiative cooling, star formation, feedback from star forming regions and active galactic nuclei) as well as in the seeding scenarios for magnetic fields (early magnetisa- tion by primordial process vs later seeding by galaxies) allows us to study both the large-scale thermodynamics and the magnetic properties of the Warm-Hot Intergalactic Medium (WHIM) with an unprecedented detail. We show how the impact of non-gravitational physics on the global thermodynamical properties of filaments is modest, with the exception of the densest gas environment surrounding galaxies in filaments. Conversely, the magnetic properties of the WHIM in filament are found to dramatically vary as different seeding scenarios are con- sidered. We study the correlation between the properties of galaxy-sized halos and their host filaments, as well as between the halos and the local WHIM in which they lie. Significant general statistical trends are reported
Multiwavelength cross-correlation analysis of the simulated cosmic web
No full textWe used magnetohydrodynamical cosmological simulations to investigate the cross-correlation between different observables (i.e. X-ray emission, Sunyaev-Zeldovich (SZ) signal at 21 cm, HI temperature decrement, diffuse synchrotron emission, and Faraday Rotation) as a probe of the diffuse matter distribution in the cosmic web. We adopt a uniform and simplistic approach to produce synthetic observations at various wavelengths, and we compare the detection chances of different combinations of observables correlated with each other and with the underlying galaxy distribution in the volume. With presently available surveys of galaxies and existing instruments, the best chances to detect the diffuse gas in the cosmic web outside of haloes is by cross-correlating the distribution of galaxies with SZ observations. We also find that the cross-correlation between the galaxy network and the radio emission or the Faraday Rotation can already be used to limit the amplitude of extragalactic magnetic fields, well outside of the cluster volume usually explored by existing radio observations, and to probe the origin of cosmic magnetism with the future generation of radio surveys
Convolutional deep denoising autoencoders for radio astronomical images
No full textWe apply a Machine Learning technique known as Convolutional Denoising Autoencoder to denoise synthetic images of state-of-the-art radio telescopes, with the goal of detecting the faint, diffused radio sources predicted to characterize the radio cosmic web. In our application, denoising is intended to address both the reduction of random instrumental noise and the minimization of additional spurious artefacts like the sidelobes, resulting from the aperture synthesis technique. The effectiveness and the accuracy of the method are analysed for different kinds of corrupted input images, together with its computational perfoance. Specific attention has been devoted to create realistic mock observations for the training, exploiting the outcomes of cosmological numerical silations, to generate images corresponding to LOFAR HBA 8 h observations at 150 MHz. Our autoencoder can effectively denoise complex images identifying and extracting faint objects at the limits of the instrumental sensitivity. The method can efficiently scale on large data sets, exploiting high-perfoance computing solutions, in a fully automated way (i.e. no human supervision is required after training). It can accurately perfo image segmentation, identifying low brightness outskirts of diffused sources, proving to be a viable solution for detecting challenging extended objects hidden in noisy radio observations
Risposta all'articolo: The Origin Myth of Magnesia-on-the-Maeander (I. Magnesia 17) and the Shaping of Civic History
No full textOn the taxonomy of Apistobranchus species (Polychaeta: Apistobranchidae) from the Antarctic
No full textVarella Petti, Mồnica A., Nonato, Edmundo F., Bromberg, Sandra, Gheller, Paula F., Paiva, Paulo Cesar, Corbisier, N. (2007): On the taxonomy of Apistobranchus species (Polychaeta: Apistobranchidae) from the Antarctic. Zootaxa 1440 (1): 51-59, DOI: 10.11646/zootaxa.1440.1.
Various properties of the Na+, K(+)-ATPase and the Mg (2+)-ATPase in erythrocytes from normotensive and hypertensive subjects
No full textSimulations of cosmic rays in large-scale structures: Numerical and physical effects
No full textNon-thermal (relativistic) particles are injected into the cosmos by structure formation shock waves, active galactic nuclei and stellar explosions. We present a suite of unigrid cosmological simulations (up to 20483) using a two-fluid model in the grid code ENZO. The simulations include the dynamical effects of cosmic ray (CR) protons and cover a range of theoretically motivated acceleration efficiencies. For the bulk of the cosmic volume the modelling of CR processes is rather stable with respect to resolution, provided that a minimum (cell) resolution ofÌ100 kpc h-1 is employed. However, the results for the innermost cluster regions depend on the assumptions for the baryonic physics. Inside clusters, non-radiative runs at high resolution tend to produce an energy density of CRs that are below available upper limits from the Fermi satellite, while the radiative runs are found to produce a higher budget of CRs. We show that weak (M ⤠3-5) shocks and shock-re-acceleration are crucial to set the level of CRs in the innermost region of clusters, while in the outer regions the level of CR energy is mainly set via direct injection by stronger shocks, and is less sensitive to cooling and feedback from active galactic nuclei and supernovae. © 2014 The Author Published by Oxford University Press on behalf of the Royal Astronomical Society
On the alignment of haloes, filaments and magnetic fields in the simulated cosmic web
No full textThe continuous flow of gas and dark matter across scales in the cosmic web can generate correlated dynamical properties of haloes and filaments (and the magnetic fields they contain). With this work, we study the halo spin properties and orientation with respect to filaments, and the morphology of the magnetic field around these objects, for haloes with masses in the range ∼108-1014 M⊙ and filaments up to ∼8 Mpc long. Furthermore, we study how these properties vary in presence, or lack thereof, of different (astro)physical processes and with different magnetic initial conditions. We perform cosmological magnetohydrodynamical simulations with the Eulerian code ENZO and we develop a simple and robust algorithm to study the filamentary connectivity of haloes in three dimensions. We investigate the morphological and magnetic properties and focus on the alignment of the magnetic field along filaments: our analysis suggests that the degree of this alignment is partially dependent on the physical processes involved, as well as on magnetic initial conditions. We discuss the contribution of this effect on a potential attempt to detect the magnetic field surrounding these objects: we find that it introduces a bias in the estimation of the magnetic field from Faraday rotation measure techniques. Specifically, given the strong tendency we find for extragalactic magnetic fields to align with the filaments axis, the value of the magnetic field can be underestimated by a factor ∼3, because this effect contributes to making the line-of-sight magnetic field (for filaments in the plane of the sky) much smaller than the total one
Deep learning based detection of cosmological diffuse radio sources
No full textIn this paper we introduce a reliable, fully automated and fast algorithm to detect extended extragalactic radio sources (cluster of galaxies, filaments) in existing and forthcoming surveys (like LOFAR and SKA). The proposed solution is based on the adoption of a Deep Learning approach, more specifically a Convolutional Neural Network, that proved to perform out- standingly in the processing, recognition and classification of images. The challenge, in the case of radio interferometric data, is the presence of noise and the lack of a sufficiently large number of labeled images for the training. We have specifically addressed these problems and the resulting software, COSMODEEP proved to be an accurate, efficient and effective solution for detecting very faint sources in the simulated radio images. We present the comparison with standard source finding techniques, and discuss advantages and limitations of our new approach
The mixing and transport properties of the intra cluster medium: A numerical study using tracers particles
No full textWe present a study of the mixing properties of the simulated intra cluster medium, using tracers particles that are advected by the gas flow during the evolution of cosmic structures. Using a sample of seven galaxy clusters (with masses in the range of M ~ 2-3 à 1014 M/h) simulated with a peak resolution of 25 kpc/h up to the distance of two virial radii from their centers, we investigate the application of tracers to some important problems concerning the mixing of the ICM. The transport properties of the evolving ICM are studied through the analysis of pair dispersion statistics and mixing distributions. As an application, we focus on the transport of metals in the ICM. We adopt simple scenarios for the injection of metal tracers in the ICM, and find remarkable differences of metallicity profiles in relaxed and merger systems also through the analysis of simulated emission from Doppler-shifted Fe XXIII lines. © ESO, 2010
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