Extragalactic filament detection with a layer smoothing method

Abstract

Filaments are clearly visible in galaxy distributions, but they are hardly detected by computer algorithms. Most methods of filament detection can be used only with numerical simulations of a large-scale structure. New simple and effective methods for the real filament detection should be developed. The method of a smoothed galaxy density field was applied in this work to SDSS data of galaxy positions. Five concentric radial layers of 100 Mpc are appropriate for filaments detection. Two methods were tested for the first layer and one more method is proposed.

X-ray galaxies in nearby filaments

“…Figure 2: Sky distribution of SDSS galaxies with radial velocities between 4000 and 11000 km/s. Larger dots are faint X-ray galaxies, squares -bright X-ray galaxies with F X > 3.7 · 10 −13 erg/cm 2 , rectangles -filaments from [1], double squares -galaxies in filaments which were considered in [4]. Figure 3: Example of new X-ray spectrum of Seyfert galaxy in SDSS filament: 2MASX J15585579+0248338.…”

“…In [2] it was shown that extragalactic X-ray sources are AGNs and clusters. It was also shown in [4] that the main type of X-ray galaxies is Seyfert 1. X-ray spectra of 42 Seyfert 1 galaxies from SDSS region were analysed in [5].…”

Simulation of large-scale structure of Universe with Gaussian random fields

“…Завдання чисельного N -вимiрного i гiдродинамiчного космологiчного моделювання є досить складними. Важко порiвнювати результати моделювання зi спостережними даними через великi систематичнi похибки [5]. Метою даної роботи було змоделювати поточний великомасштабний розподiл галактик випадковими гаусiвськими полями.…”

Extracting Filaments Based on Morphology Components Analysis from Radio Astronomical Images

“…Hennebelle et al [12] showed a method based on adaptive mesh refinement magneto hydrodynamic simulations, which treat self-consistently cooling and selfgravity. Tugay [13] proposed a layer smoothing method, 2 Advances in Astronomy which described cellular large-scale structure of the universe (LSS) as a grid of clusters with density larger than a limited value, to detect extragalactic filaments. Men'shchikov [14] proposed a multi-scale filaments extraction method named getfilaments, which decomposed a simulated astronomical image containing filaments into spatial images at different scales to prevent interaction influence of different spatial scale structures.…”