Search results for "Hydrodynamics"
showing 10 items of 390 documents
A CUDA-based implementation of an improved SPH method on GPU
2021
We present a CUDA-based parallel implementation on GPU architecture of a modified version of the Smoothed Particle Hydrodynamics (SPH) method. This modified formulation exploits a strategy based on the Taylor series expansion, which simultaneously improves the approximation of a function and its derivatives with respect to the standard formulation. The improvement in accuracy comes at the cost of an additional computational effort. The computational demand becomes increasingly crucial as problem size increases but can be addressed by employing fast summations in a parallel computational scheme. The experimental analysis showed that our parallel implementation significantly reduces the runti…
High-energy monitoring of NGC 4593 II. Broad-band spectral analysis: testing the two-corona model
2019
It is widely believed that the primary X-ray emission of AGN is due to the Comptonisation of optical-UV photons from a hot electron corona, while the origin of the 'soft-excess' is still uncertain and matter of debate. A second Comptonisation component, called warm corona, was therefore proposed to account for the soft-excess, and found in agreement with the optical-UV to X-ray emission of a sample of Seyfert galaxies. In this context, we exploit the broadband XMM-Newton and NuSTAR simultaneous observations of the Seyfert galaxy NGC 4593 to further test the so called "two corona model". The NGC 4593 spectra are well reproduced by the model, from the optical/UV to the hard X-rays. Moreover, …
Cosmological hydrodynamical simulations of galaxy clusters: X-ray scaling relations and their evolution
2018
We analyse cosmological hydrodynamical simulations of galaxy clusters to study the X-ray scaling relations between total masses and observable quantities such as X-ray luminosity, gas mass, X-ray temperature, and $Y_{X}$. Three sets of simulations are performed with an improved version of the smoothed particle hydrodynamics GADGET-3 code. These consider the following: non-radiative gas, star formation and stellar feedback, and the addition of feedback by active galactic nuclei (AGN). We select clusters with $M_{500} > 10^{14} M_{\odot} E(z)^{-1}$, mimicking the typical selection of Sunyaev-Zeldovich samples. This permits to have a mass range large enough to enable robust fitting of the r…
X-ray and optical emission in protostellar jets: model predictions and comparison with observations
2007
Modeling the X-ray emission from the nearest jets: HH 154 and DG Tau
2010
X-ray Emission in protostellar jets
2005
Prompted by the recent detection of X-ray emission from Herbig-Haro objects, we studied the interaction between a supersonic jet originating from a young stellar object and the ambient medium; our aim is to investigate the mechanisms causing the X-ray emission. Our model takes into account the radiative losses from optically in plasmas and Spitzer's thermal conduction including saturation effects. We explored the parameter space defined by the density contrast between the ambient medium and the jet and by the Mach number, to infer the configurations which can give rise to X-ray emission. From the models, we derived the X-ray emission as it would be observed with Chandra/ACIS-I and XMM-Newto…
X-ray emission in protostellar jets: comparison between model predictions and observations
2007
Herbig-Haro objects: model prediction and comparison with X-ray and optical observations
2007
X-ray emission from fast moving shocks in the protostellar jet HH 154: a binding diagnostic of the emission mechanism
2004
We propose to determine the proper motion of the X-ray source associated with HH 154, the only known protostellar jet in which the X-ray emission mechanism can be studied in detail. Our numerical simulations indicate that the X-rays are produced in a fast-moving (500 km/s) post-shock region, and our HST observations show high proper motion shocked material moving at similar speed. Detection (or lack of) of proper motion of the X-ray source will strongly confirm (or falsify) our model, and constitute the basis for a general theory of X-ray emission in protostellar jets. Understanding and modeling the emission mechanism is key to assess the lifetime of the X-ray emission and thus the influenc…