1,721,023 research outputs found
GrGadget: an N-body TreePM relativistic code for cosmological simulations
Full text linkWe present the merging of the Particle-Mesh (PM) relativistic Gevolution code
with the TreePM Gadget-4 code, with the aim of studying general relativity
effects in cosmology. Our code, called GrGadget, is able to track the evolution
of metric perturbations in the weak field limit by using Gevolution's
implementation of a relativistic PM in the Poisson gauge. To achieve this,
starting from Gevolution we have written a C++ library called libgevolution,
that allows a code to access and use the same abstractions and resources that
Gevolution uses for its PM-only N-body simulations. The code works under the
assumption that particle interactions at short distances can be approximated as
Newtonian, so that we can combine the forces computed with a Newtonian Tree
with those computed with a relativistic PM. The result is a TreePM simulation
code that represents metric perturbations at the scales where they are
relevant, while resolving non-linear structures. We validate our code by
closely matching Gadget-4 forces, computed with the Tree switched off, with
those computed with libgevolution in the Newtonian limit. With GrGadget we
obtain a matter power spectrum that is compatible with Newtonian Gadget at
small scales and contains GR features at large scales that are consistent with
results obtained with Gevolution. We demonstrate that, due to the better
resolution of the highly non-linear regime, the representation of the
relativistic fields sampled on the mesh improves with respect to the PM-only
simulations.Comment: 15 pages, 14 figure
Metal and molecule cooling in simulations of structure formation
No full textCooling is the main process leading to the condensation of gas in the dark matter potential wells and consequently to star and structure formation. In a metal-free environment, the main available coolants are H, He, H2 and HD; once the gas is enriched with metals, these also become important in defining the cooling properties of the gas. We discuss the implementation in GADGET-2 of molecular and metal cooling at temperatures lower than 104 K, following the time-dependent properties of the gas and pollution from stellar evolution. We have checked the validity of our scheme by comparing the results of some test runs with previous calculations of cosmic abundance evolution and structure formation, finding excellent agreement. We have also investigated the relevance of molecule and metal cooling in some specific cases, finding that inclusion of HD cooling results in a higher clumping factor of the gas at high redshifts, while metal cooling at low temperatures can have a significant impact on the formation and evolution of cold objects
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
On the dynamical origin of the ICM metallicity evolution
Full text linkWe present a study on the origin of the metallicity evolution of the intra-cluster medium (ICM) by applying a semi-analytic model of galaxy formation to N-body/smoothed particle hydrodynamic (SPH) non-radiative numerical simulations of clusters of galaxies. The semi-analytic model includes gas cooling, star formation, supernovae feedback and metal enrichment, and is linked to the diffuse gas of the underlying simulations so that the chemical properties of gas particles are dynamically and consistently generated from stars in the galaxies. This hybrid model lets us have information on the spatial distribution of metals in the ICM. The results obtained for a set of clusters with virial masses of ∼1.5 × 1015 h−1 M contribute to the theoretical interpretation of recent observational X-ray data, which indicate a decrease of the average iron content of the intra-cluster gas with increasing redshift. We find that this evolution arises mainly as a result of a progressive increase of the iron abundance within ∼0.15 Rvir. The clusters have been considerably enriched by z ∼ 1 with very low contribution from recent star formation. Low entropy gas that has been enriched at high redshift sinks to the cluster centre contributing to the evolution of the metallicity profiles.Fil: Cora, Sofia Alejandra. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. 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: Tornatore, Luca. Istituto Nazionale Di Astrofisica; ItaliaFil: Tozzi, Paolo. Istituto Nazionale Di Astrofisica; ItaliaFil: Dolag, Klaus. Max-Planck-Institut fur Astrophysik; Alemani
Dynamical friction and evolution of black holes in cosmological simulations: a new implementation in OpenGadget3
Full text linkFil: Damiano, Alice. Dipartimento di Fisica dell’Università di Trieste. Sez. di Astronomia; Italy.Fil: Damiano, Alice. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Damiano, Alice. Istituto Nazionale di Astrofisica. Instituto Nazionale di Fisica Nucleare; Italy.Fil: Damiano, Alice. Italian Research Center on High Performance Computing. Big Data and Quantum Computing; Italy.Fil: Valentini, Milena. Dipartimento di Fisica dell’Università di Trieste. Sez. di Astronomia; Italy.Fil: Valentini, Milena. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Valentini, Milena. Istituto Nazionale di Astrofisica. Instituto Nazionale di Fisica Nucleare; Italy.Fil: Valentini, Milena. Italian Research Center on High Performance Computing. Big Data and Quantum Computing; Italy.Fil: Borgani, Stefano. Dipartimento di Fisica dell’Università di Trieste. Sez. di Astronomia; Italy.Fil: Borgani, Stefano. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Borgani, Stefano. Institute for Fundamental Physics of the Universe; Italy.Fil: Borgani, Stefano. Istituto Nazionale di Astrofisica. Instituto Nazionale di Fisica Nucleare; Italy.Fil: Borgani, Stefano. Italian Research Center on High Performance Computing. Big Data and Quantum Computing; Italy.Fil: Tornatore, Luca. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Tornatore, Luca. Italian Research Center on High Performance Computing. Big Data and Quantum Computing; Italy.Fil: Murante, Giuseppe. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Murante, Giuseppe. Institute for Fundamental Physics of the Universe; Italy.Fil: Murante, Giuseppe. Italian Research Center on High Performance Computing. Big Data and Quantum Computing; Italy.Fil: Ragagnin, Antonio. Institute for Fundamental Physics of the Universe; Italy.Fil: Ragagnin, Antonio. Osservatorio di Astrofisica e Scienza dello Spazio di Bologna; Italy.Fil: Ragagnin, Antonio. Alma Mater Studiorum Università di Bologna. Dipartimento di Fisica e Astronomia "Augusto Righi"; Italy.Fil: Ragone-Figueroa, Cinthia. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Ragone-Figueroa, Cinthia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Astronomía Teórica y Experimental; Argentina.Fil: Ragone-Figueroa, Cinthia. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Dolag, Klaus. Universitäts-Sternwarte München; Germany.Fil: Dolag, Klaus. Max-Plank-Institut für Astrophysik; Germany.We implement a sub-resolution prescription for the unresolved dynamical friction onto black holes (BHs) in the OpenGadget3 code. We carry out cosmological simulations of a volume of 16 cMpc3 and zoom-ins of a galaxy group and of a galaxy cluster. The advantages of our new technique are assessed in comparison to commonly adopted methods to hamper spurious BH displacements, i.e. repositioning onto a local minimum of the gravitational potential and ad-hoc boosting of the BH particle dynamical mass. The newly-introduced dynamical friction correction provides centering of BHs on host halos which is at least comparable with the other techniques. It predicts half as many merger events with respect to the repositioning prescription, with the advantage of being less prone to leave sub-structures without any central BH. Simulations featuring our dynamical friction prescription produce a smaller (by up to 50% with respect to repositioning) population of wandering BHs and final BH masses in good agreement with observations. As for individual BH-BH interactions, our dynamical friction model captures the gradual inspiraling of orbits before the merger occurs. By contrast, the repositioning scheme, in its most classical renditions considered, describes extremely fast mergers, while the dynamical mass misrepresents the BHs' dynamics, introducing numerical scattering between the orbiting BHs. Given its performances in describing the centering of BHs within host galaxies and the orbiting of BH pair before their merging, our dynamical friction correction opens interesting applications for an accurate description of the evolution of BH demography within cosmological simulations of galaxy formation at different cosmic epochs and within different environments.info:eu-repo/semantics/acceptedVersionFil: Damiano, Alice. Dipartimento di Fisica dell’Università di Trieste. Sez. di Astronomia; Italy.Fil: Damiano, Alice. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Damiano, Alice. Istituto Nazionale di Astrofisica. Instituto Nazionale di Fisica Nucleare; Italy.Fil: Damiano, Alice. Italian Research Center on High Performance Computing. Big Data and Quantum Computing; Italy.Fil: Valentini, Milena. Dipartimento di Fisica dell’Università di Trieste. Sez. di Astronomia; Italy.Fil: Valentini, Milena. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Valentini, Milena. Istituto Nazionale di Astrofisica. Instituto Nazionale di Fisica Nucleare; Italy.Fil: Valentini, Milena. Italian Research Center on High Performance Computing. Big Data and Quantum Computing; Italy.Fil: Borgani, Stefano. Dipartimento di Fisica dell’Università di Trieste. Sez. di Astronomia; Italy.Fil: Borgani, Stefano. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Borgani, Stefano. Institute for Fundamental Physics of the Universe; Italy.Fil: Borgani, Stefano. Istituto Nazionale di Astrofisica. Instituto Nazionale di Fisica Nucleare; Italy.Fil: Borgani, Stefano. Italian Research Center on High Performance Computing. Big Data and Quantum Computing; Italy.Fil: Tornatore, Luca. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Tornatore, Luca. Italian Research Center on High Performance Computing. Big Data and Quantum Computing; Italy.Fil: Murante, Giuseppe. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Murante, Giuseppe. Institute for Fundamental Physics of the Universe; Italy.Fil: Murante, Giuseppe. Italian Research Center on High Performance Computing. Big Data and Quantum Computing; Italy.Fil: Ragagnin, Antonio. Institute for Fundamental Physics of the Universe; Italy.Fil: Ragagnin, Antonio. Osservatorio di Astrofisica e Scienza dello Spazio di Bologna; Italy.Fil: Ragagnin, Antonio. Alma Mater Studiorum Università di Bologna. Dipartimento di Fisica e Astronomia "Augusto Righi"; Italy.Fil: Ragone-Figueroa, Cinthia. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina.Fil: Ragone-Figueroa, Cinthia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Astronomía Teórica y Experimental; Argentina.Fil: Ragone-Figueroa, Cinthia. Istituto Nazionale di Astrofisica. Osservatorio Astronomico di Trieste; Italy.Fil: Dolag, Klaus. Universitäts-Sternwarte München; Germany.Fil: Dolag, Klaus. Max-Plank-Institut für Astrophysik; Germany
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