博碩士論文 88229009 詳細資訊




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姓名 蔡明燕( Ming-Yann Tsay)  查詢紙本館藏   畢業系所 天文研究所
論文名稱 后髮座星系團內相對論性電子能譜的數值計算
(Numerical Calculations Of The Energy Spectrum Of Relativistic Electrons In The Coma Galaxy Cluster)
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摘要(中) 由EUVE及BeppoSAX衛星對后髮座星系團的觀測發現,在65-245 eV波段(EUV波段)及20-80 keV波段(hard X-ray波段),有餘值輻射(excess emission)的出現。一般認為,於后髮座星系團內所偵測到的X-ray輻射,是由溫度約8 keV的氣體熱輻射而來。所謂的餘值輻射,以疊加在熱X-ray輻射上多餘輻射的形式出現。在EUV波段的餘值輻射,通常被認為是由能量幾百MeV的電子,經逆康普頓散射微波背景輻射光子後的結果,而在hard X-ray波段的餘值輻射來源目前仍有爭議。如果在EUV波段的餘值輻射是由逆康普頓散射而成,則我們可以藉此給定電子在能譜上能量γ約等於400附近的數量分布。同樣的,無線電輻射可以給定電子在能譜上能量γ約從700到4×104附近的數量分布。磁場強度將決定由無線電輻射資料導出的電子能量範圍。
我們提出連續注入電子模型,並計算在此模型下相對論性電子的可能能譜。我們進一步依照有無初始的強電子注入事件,將此模型分成二種亞型。在做模擬計算時,我們分別計算磁場為5μG及0.2μG下的相對論性電子能譜。由我們的模擬結果發現,餘值輻射在連續注入電子模型且有初始強電子注入事件的狀態下,無論在磁場為5μG或0.2μG,都能獲得很好的擬和。相對的,在連續注入電子模型且無初始強電子注入事件的狀況下,只有在磁場為0.2μG的狀況下,能獲得餘值輻射良好的擬和。
摘要(英) Observations carried out by Extreme Ultraviolet Explorer (EUVE) and the BeppoSAX on the Coma cluster detect excess emission, which is an extra emission superposed on what expected of a thermal X-ray emission and lies at both ends of this thermal X-ray emission. At the low-energy end between 65-245 eV (the
EUV excess), the excess is usually explained as inverse Compton emission by a few-hundred-MeV electrons up scattering the cosmic microwave background photons while the origin of the excess at the high-energy end between 20-80 keV is still in debate. The assumption of an inverse Compton scattering origin for the EUV excess can give a constraint on the electron spectrum at ? 400 while synchrotron radio emission will give a constraint on electron spectra in the energy range of ? 700 to ? 40000 depending on the strength of the magnetic field.
We propose models of continuous electron injections either with or without a major first event and carry out the modeling electron spectra by adopting two different magnetic fields, 5 and 0.2 G, which are as suggested by Faraday rotation measurements and as required for the inverse Compton interpretation of the observed hard X-ray excess emission. We nd that the observed excess emission can be perfectly explained by models of continuous electron injections with a major first event in both magnetic fields and models of continuous electron
injections without a major first event in low magnetic field.
關鍵字(中) ★ 后髮座星系團
★ 相對論性電子
關鍵字(英) ★ Coma galaxy cluster
★ Relativistic electrons
論文目次 1.INTRODUCTION . . . . . .. . . . . . . . . . . . .. . . . . . 1
2. PROPERTY AND EVOLUTION OF RELATIVISTIC ELECTRONS . .. . ...5
2.1 Energy Loss Mechanisms . .. . . . . . . . . . . . ... . . . ............ ..5
2.1.1 Inverse Compton Scattering (ICS) . . . .. . . . . . ....5
2.1.2 Synchrotron Radiation . . . . . . .. . .. . . . . . . . .6
2.1.3 Coulomb Ionization . . . . . . . .. . . . . . . .........6
2.1.4 Bremsstrahlung Radiation . . . . . . . . . . .. . . . . .7
2.2 Diusion Timescale For Relativistic Electrons. . . . . . 7
2.3 Evolution Function .. . ......... . . . . ... . . . . . . .8
3. OBSERVATIONAL ELECTRON SPECTRUM . . . .. . . . . . . . . . 9
3.1 Theory ... . . .. . . .. . ........ . . . . . ... . . . . .9
3.2 Distribution of the Electrons Producing Synchrotron Radio Emission . .. . . . . . . ....................................10
3.3 Location of the Electrons Responsible for the EUV Excess .11
4. NUMERICAL TECHNIQUE . .. . .. . . ...... . . . . . . . . ..13
5. COMPUTATIONAL RESULTS AND DISCUSSION . . . ..... . . . . . 15
5.1 Primary Origin Model . . ...... . . . . . . . . . . .. . .15
5.2 Continuous Injection Model . . . .. . . . . .. . . . . . .15
5.2.1 One Major Injection Followed by Continuous Small Events.16
5.2.2 Just Small Events without a Major Injection . . . . . ..19
6. SUMMARY . . . .. . . . . . . . ...... . . . . . . . ... . .22
REFERENCE . ...... . . . .. . . . . . . . . . . . .. . . . . .24
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指導教授 黃崇源(Chorng-Yuan Hwang) 審核日期 2001-6-22
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