耀變體之光譜性質及無線電波輻射時變性;Spectral Properties and Radio Variability of Blazars

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/91982

Title:	耀變體之光譜性質及無線電波輻射時變性;Spectral Properties and Radio Variability of Blazars
Authors:	許博智;Hsu, Po-Chih
Contributors:	天文研究所
Keywords:	活躍星系核;耀變體;光譜特性;無線電光譜時變性;星系黑洞物理;星系噴流;類星體;星系無線電連續光譜;active galactic nuclei;blazar;spectral properties;radio variability;physcis of black holes;jets of galaxies;quasars;radio continuum of galaxies
Date:	2023-07-24
Issue Date:	2024-09-19 14:44:54 (UTC+8)
Publisher:	國立中央大學
Abstract:	為了有全方位的了解耀變體的光譜特性。在研究中，我們使用第五版Roma-BZCAT多波段耀變體目錄（the 5-th edition Roma-BZCAT Multi-frequency Catalog of Blazars）、ALMA校準目錄（ALMA Calibrator Catalog）以及各頻率的觀測資料進行耀變體的光譜特性分析。在1366個耀變體樣本中，我們計算無線電-毫米波頻譜指數和無線電頻譜指數，並擬合其全頻率頻譜能量分佈。分析表明，在蝎虎座天體（BL Lacertae object）與平譜電波類星體（flat spectrum radio quasar）中，相較於無線電-毫米波頻譜指數，無線電頻譜指數顯示出更廣泛的分佈。此外，我們將平譜電波類星體根據紅移，分為高紅移和低紅移的子分類。研究表明，高紅移平譜電波類星體表現出相較低紅移平譜電波類星體和蝎虎做天體有更平緩的無線電頻譜指數。此外，我們發現蝎虎座天體及平譜電波類星體的無線電-毫米波頻譜指數與無線電頻譜指數和同步輻射頻率峰值與光度之間沒有顯著相關性。此外，我們還研究耀變體本質上的差異，藉由探索耀變體的無線電時變性。我們研究所使用的的耀變體取自於15 GHz歐文斯谷無線電天文台的耀變體監測計劃（15 GHz Owens Valley Radio Observatory Blazar Monitoring Program），此計畫自2008年開始使用15 GHz觀測耀變體至今。在計畫監測的1157個耀變體中，我們研究耀變體時變震幅和特徵時變尺度（基於擬合結構函數（structure function）的計算結果），與特長基線干涉儀測量的毫弧秒尺度的核心尺寸之間的依賴性。我們發現，較緊湊的角核心尺寸表現出更大的時變震幅和更短的特徵時變尺度，而真實的核心尺寸與時變震幅以及特徵時變尺度也具有顯著相關。此外，在消除因星際散射造成角核心尺寸放大效應後，時變震幅與1 GHz的固有角核心尺寸具有顯著相關性。 ;To obtain a comprehensive understanding of the spectral properties of blazars, extensive analysis was conducted using the multi-frequency data from the 5-th edition Roma-BZCAT and ALMA Calibrator Catalog, along with other archival data. This involved calculating the radio-mm/radio spectral index and fitting broadband spectral energy distribution for 1366 sources. Analysis revealed that the radio spectral index displayed a broader distribution compared to the radio-mm spectral index of both BL Lacertae objects (BLOs) and flat-spectrum radio quasars (FSRQs).In addition, these FSRQs were categorized based on their redshifts into high-z and low-z FSRQs. The high-z FSRQs exhibit significantly flatter radio spectral index than the low-z FSRQs and BLOs. Additionally, we found no significant correlation between the radio-mm/radio spectral indices and the synchrotron peak frequencies and luminosities of both BLOs and FSRQs. In addition, we also study the radio variability of blazars to investigate their intrinsically variable nature. We focus on the radio variability of 1157 blazars observed at 15~GHz through the Owens Valley Radio Observatory (OVRO) Blazar Monitoring Program. We investigate the dependence of the variability amplitudes and timescales, which were characterized based on model fitting to the structure functions, on the milliarcsecond core sizes measured by Very Long Baseline Interferometry. We find that the more compact sources at milliarcsecond scales demonstrate larger variability amplitudes and shorter variability timescales compared to the more extended sources. Moreover, linear physical core sizes versus variability amplitudes, and intrinsic timescales are also significantly correlated. Besides, the variability amplitudes have significant correlation with the 1~GHz intrinsic core sizes, which are derived by deconvoluting the broadening effects of the interstellar scattering.
Appears in Collections:	[Graduate Institute of Astronomy] Electronic Thesis & Dissertation

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