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The treatment of radiative transfer with multiple radiation sources is a critical challenge in simulations of star formation and the interstellar medium. In this paper we present the novel TreeRay method for solving general radiative…

Instrumentation and Methods for Astrophysics · Physics 2021-06-30 Richard Wünsch , Stefanie Walch , František Dinnbier , Daniel Seifried , Sebastian Haid , Andre Klepitko , Anthony P. Whitworth , Jan Palouš

In this paper we present two efficient implementations of the diffusion approximation to be employed in Monte Carlo computations of radiative transfer in dusty media of massive circumstellar disks. The aim is to improve the accuracy of the…

Instrumentation and Methods for Astrophysics · Physics 2009-11-13 M. Min , C. P. Dullemond , C. Dominik , A. de Koter , J. W. Hovenier

We develop a method to calculate the column density distribution of the Lyman-alpha forest for column densities in the range $10^{12.5} - 10^{14.5} cm^{-2}$. The Zel'dovich approximation, with appropriate smoothing, is used to compute the…

Astrophysics · Physics 2009-10-28 Lam Hui , Nickolay Y. Gnedin , Yu Zhang

We present TREVR2 (Tree-based REVerse Ray Tracing 2), a fast, general algorithm for computing the radiation field, suitable for both particle and mesh codes. It is designed to self-consistently evolve chemistry for zoomed-in astrophysical…

Instrumentation and Methods for Astrophysics · Physics 2024-01-18 James W. Wadsley , Bernhard Baumschlager , Sijing Shen

Filaments represent a key structure during the early stages of the star formation process. Simulations show filamentary structure commonly formed before and during the formation of cores. Aims. The Serpens Core represents an ideal…

Astrophysics of Galaxies · Physics 2015-12-16 V. Roccatagliata , J. E. Dale , T. Ratzka , L. Testi , A. Burkert , C. Koepferl , A. Sicilia-Aguilar , C. Eiroa , B. Gaczkowski

In this work we demonstrate the ability of the Minimal Spanning Tree to duplicate the information contained within a percolation analysis for a point dataset. We show how to construct the percolation properties from the Minimal Spanning…

Astrophysics · Physics 2015-06-24 S. P. Bhavsar , R. J. Splinter

We present a geometry-independent method for determining the shapes of radial volume density profiles of astronomical objects whose geometries are unknown, based on a single column density map. Such profiles are often critical to understand…

Astrophysics of Galaxies · Physics 2016-05-04 Marko Krčo , Paul F. Goldsmith

We propose a simple analytical method for estimating the central volume density of prestellar molecular cloud cores from their column density profiles. Prestellar cores feature a flat central part of the column density and volume density…

Astrophysics of Galaxies · Physics 2015-05-28 Konstantinos Tassis , Harold W. Yorke

Many kernel methods suffer from high time and space complexities and are thus prohibitive in big-data applications. To tackle the computational challenge, the Nystr\"om method has been extensively used to reduce time and space complexities…

Machine Learning · Computer Science 2014-04-02 Shusen Wang , Zhihua Zhang

The Galactic Cold Cores (GCC) project has made Herschel observations of interstellar clouds where Planck detected compact sources of cold dust emission. Our aim is to characterise the structure of the clumps and their parent clouds. We also…

Astrophysics of Galaxies · Physics 2018-06-20 M. Juvela , J. Malinen , J. Montillaud , V. -M. Pelkonen , I. Ristorcelli , L. V. Toth

We introduce a cluster evaluation technique called Tree Index. Our Tree Index algorithm aims at describing the structural information of the clustering rather than the quantitative format of cluster-quality indexes (where the representation…

Machine Learning · Computer Science 2020-03-25 A. H. Beg , Md Zahidul Islam , Vladimir Estivill-Castro

Dealing with land cover classification of the new image sources has also turned to be a complex problem requiring large amount of memory and processing time. In order to cope with these problems, statistical learning has greatly helped in…

Herschel has revolutionized our ability to measure column densities (N$_{\rm H}$) and temperatures (T) of molecular clouds thanks to its far infrared multiwavelength coverage. However, the lack of a well defined background intensity level…

Instrumentation and Methods for Astrophysics · Physics 2017-08-09 J. Abreu-Vicente , A. Stutz , Th. Henning , E. Keto , J. Ballesteros-Paredes , T. Robitaille

The simulation of electrical discharges has been attracting a great deal of attention. In such simulations, the electric field computation dominates the computational time. In this paper, we propose a fast tree algorithm that helps to…

Computational Engineering, Finance, and Science · Computer Science 2018-07-04 Chijie Zhuang , Yong Zhang , Xin Zhou , Rong Zeng , Jinliang He , Lei Liu

This paper presents new methodology for computationally efficient kernel density estimation. It is shown that a large class of kernels allows for exact evaluation of the density estimates using simple recursions. The same methodology can be…

Computation · Statistics 2019-11-12 David P. Hofmeyr

I apply the well controlled Hydro-PM approximation of Gnedin & Hui to model the column density distribution of the Lyman-alpha forest for 25 different flat cosmological scenarios, including variants of the standard CDM, tilted CDM, CDM with…

Astrophysics · Physics 2009-10-30 Nickolay Y. Gnedin

We present a simple, yet powerful column density diagnostic for plasmas enabled by X-ray microcalorimeter observations. With the recent developments of the spectral simulation code Cloudy, inspired by the high spectral resolution of the…

High Energy Astrophysical Phenomena · Physics 2025-02-19 Chamani M. Gunasekera , Peter A. M. van Hoof , Masahiro Tsujimoto , Gary J. Ferland

We describe a simple method for estimating the vertical column density in Smoothed Particle Hydrodynamics (SPH) simulations of discs. As in the method of Stamatellos et al. (2007), the column density is estimated using pre-computed local…

Instrumentation and Methods for Astrophysics · Physics 2015-06-05 Matthew D. Young , Erik Bertram , Nick Moeckel , Cathie J. Clarke

[Abridged] We present a novel technique, dubbed FiEstAS, to estimate the underlying density field from a discrete set of sample points in an arbitrary multidimensional space. FiEstAS assigns a volume to each point by means of a binary tree.…

Astrophysics · Physics 2009-11-10 Y. Ascasibar , J. Binney

We present a ray-tracing technique for radiative transfer modeling of complex three-dimensional (3D) structures which include dense regions of high optical depth like in dense molecular clouds, circumstellar disks, envelopes of evolved…

Astrophysics · Physics 2009-11-11 J. Steinacker , A. Bacmann , Th. Henning