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  • 學位論文

Testing adiabatic expansion and the equipartition assumption in parsec scale AGN jets with the source OH-010

在活躍星系核OH-010的噴流中檢測絕熱膨脹與能量均分兩噴流模型

指導教授 : 江國興

摘要


在本論文中,我們研究類星體 (Quasar) OH-010 之物理特性。我們使用 MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) 團隊所維護的網路資料庫中利用超長基線陣列 (Very Long Baseline Array,簡稱 VLBA) 在頻率 15.4 GHz 觀測的資料與數個單天線電波望遠鏡 (Single Dish Radio Telescope),涵蓋頻率 4.8、8、14.5、22、37與 90 GHz 的長期量測資料(光變曲線)。本研究的首要目標為檢測兩個當今常用於活躍星系核噴流 (active galactic nuclei jets) 分析中之假設:其ㄧ、由 Marscher 與 Gear 於 1985 年提出的絕熱膨脹噴流模型 (adiabatic jet model);其二、由 Blandford 與 Konigl 於 1979 年提出的能量均分噴流模型 (equipartition jet model)。我們利用 VLBA 的數據發現兩個噴流component 在其光通量與其大小之間具有冪律關係,是為上述兩模型之特徵。進一步分析使我們得知 component 4 於噴流之初始位置滿足(粒子與磁場間)能量均分並在噴流行進過程中持續滿足此關係;而對於 component 3 我們並無法區分絕熱膨脹噴流模型與能量均分噴流模型何者較為適合,另外與 component 4 相異的是,component 3 不具有初始的能量均分關係。 結合 VLBA 與單天線望遠鏡之資料顯示 component 2 與 component 3 兩者皆與(單天線望遠鏡之)光變曲線中的兩個爆發 (flare) 有關。我們提議使用具有拋物線 (parabolic) 、圓錐 (conical) 雙重結構之噴流來解釋此現象,此結構下,當噴流行進於拋物線結構中會加速、而於圓錐結構中則為等速。整體而言,我們在此天體中之發現與 M87 中之噴流相當類似。

關鍵字

黑洞 噴流 電漿 絕熱膨脹 等溫膨脹

並列摘要


The quasar OH-010 is studied using data obtained by the Very Long Baseline Array (VLBA)at 15.4 GHz from the MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) archive and light curves from single dish observations at 4.8, 8, 14.5, 22, 37,and 90 GHz. One goal of this works is to examine the applicability of two commonly used assumptions for active galactic nuclei jets: an adiabatic jet (Marscher & Gear 1985) or a jet which holds equipartition between particle and field energies (Blandford & Konigl 1979) to the behavior of this source. We find a clear power law signature in two VLBI (Very Long Baseline Interferometry) components and found that for component 4, it is consistent with having initial equipartition and remains to be so along the jet. Component 3 in contrast can be explained by either case but it does not have initial equipartition between particle and magnetic field. Connecting VLBA data with light curve data revealed that both VLBI components 2 and 3 may be related to two flares in the light curve. We propose that such behavior can be explained by a jet which has an initial parabolic structure where components exhibit accelerated motion followed by a transition to a conical structure in which components travel at constant velocity. We find this transition to have properties similar to a recollimation shock and the overall finding is reminiscent of the jet in M87. The finding of a quasi-stationary component on VLBI maps ∼ 0.29 mas downstream of the radio core also supports this scenario.

並列關鍵字

Blac Jet Plasma Adiabatic Expansion Isothermal Expansion

參考文獻


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