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On the Relation Between Symmetry of Radio Galaxies and Their Physical Parameters

Research in Astronomy and Astrophysics 2024年第9期24卷 39-61页

作者： Mohsen Javaherian Halime Miraghaei Hooman Moradpour Research Institute for Astronomy and Astrophysics of Maragha (RIAAM) University of Maragheh

Gravity as a fundamental force plays a dominant role in the formation and evolution of cosmic objects and leaves its effect in the emergence of symmetric and asymmetric structures. Thus, analyzing the symmetry criteria allows us to uncover mechanisms behind the gravity interaction and understand the underlying physical processes that contribute to the formation of large-scale structures such as galaxies. We use a segmentation process using intensity thresholding and the k-means clustering algorithm to analyze radio galaxy images. We employ a symmetry criterion and explore the relation between morphological symmetry in radio maps and host galaxy properties. Optical properties(stellar mass, black hole mass, optical size(R50), concentration, stellar mass surface density(μ50), and stellar age) and radio properties（radio flux density, radio luminosity, and radio size） are considered. We found that there is a correlation between symmetry and radio size, indicating larger radio sources have smaller symmetry indices. Therefore, size of radio sources should be considered in any investigation of symmetry. Weak correlations are also observed with other properties, such as R50for FRI galaxies and stellar *** compare the symmetry differences between FRI and FRII radio galaxies. FRII galaxies show higher symmetry in 1.4 GHz and 150 MHz maps. Investigating the influence of radio source sizes, we discovered that this result is independent of the sizes of radio sources. These findings contribute to our understanding of the morphological properties and analyses of radio galaxies.

关键词： catalogs galaxies: distances and redshifts galaxies: nuclei methods: data analysis techniques: image processing

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Comparison of three filters in asteroid-based autonomous navigation

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Research in Astronomy and Astrophysics 2014年第3期14卷 329-344页

作者： Wen Cui Kai-Jian Zhu State Key Laboratory of Astronautic Dynamics Xi’an Satellite Control Center

At present, optical autonomous navigation has become a key technologyin deep space exploration programs. Recent studies focus on the problem of orbit de-termination using autonomous navigation, and the choice of filter is one of the mainissues. To prepare for a possible exploration mission to Mars, the primary emphasisof this paper is to evaluate the capability of three filters, the extended Kalman filter（EKF）, unscented Kalman filter （UKF） and weighted least-squares （WLS） algorithm,which have different initial states during the cruise phase. One initial state is assumedto have high accuracy with the support of ground tracking when autonomous navi-gation is operating; for the other state, errors are set to be large without this *** addition, the method of selecting asteroids that can be used for navigation fromknown lists of asteroids to form a sequence is also presented in this study. The simula-tion results show that WLS and UKF should be the first choice for optical autonomousnavigation during the cruise phase to Mars.

关键词： celestial mechanics asteroids equation of state methods: data analysis techniques: image processing

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