| Item type |
学位論文 / Thesis or Dissertation(1) |
| 公開日 |
2010-02-22 |
| タイトル |
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タイトル |
Kinematic-and Synchrotron-Aging Studies for Young Extragalactic Radio Sources |
| タイトル |
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タイトル |
Kinematic-and Synchrotron-Aging Studies for Young Extragalactic Radio Sources |
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言語 |
en |
| 言語 |
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|
言語 |
eng |
| 資源タイプ |
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資源タイプ識別子 |
http://purl.org/coar/resource_type/c_46ec |
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資源タイプ |
thesis |
| 著者名 |
永井, 洋
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| フリガナ |
ナガイ, ヒロシ
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| 著者 |
NAGAI, Hiroshi
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| 学位授与機関 |
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学位授与機関名 |
総合研究大学院大学 |
| 学位名 |
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学位名 |
博士（理学） |
| 学位記番号 |
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内容記述タイプ |
Other |
|
内容記述 |
総研大甲第1034号 |
| 研究科 |
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|
値 |
物理科学研究科 |
| 専攻 |
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値 |
09 天文科学専攻 |
| 学位授与年月日 |
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学位授与年月日 |
2007-03-23 |
| 学位授与年度 |
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値 |
2006 |
| 要旨 |
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内容記述タイプ |
Other |
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内容記述 |
Compact Symmetric Objects（CSOs）are proved to be young radio sources from both the kinematic- and synchrotron－aging studies．<br /> With Very Long Baseline Array（VLBA）observations for CTD 93 over 8.5 yr，we detected an increase of separation between the hot spot and the counter hot spot. The separation rate along the source axis is 0.34±0.11<i> c</i>, which results in a kinematic age of 2200±700 yr. Assuming that two hot spots are moving apart from the core at equal speeds，we derive an advance velocity of 0.17±0.06<i>c.</i>On the other hand, our multi-frequency observations revealed that radio－lobe spectra show a high- frequency steepening due to synchrotron aging. The spectral break decreases with distance from the hot spot. This tendency is expected from the basic scenario of radio lobe evolution involving particle acceleration at the hotspots，With the radio lobe populated by high－energy electrons that have leaked our from the hot spots. From the spectral fit in the radio lobe of CTD 93 under the minimum－energy assumption, we derive the advance velocity of 0.232±0.005<i>c</i> and synchrotron age of 1720±40 yr. The kinematic age and synchrotron age show an agreement within a factor of two．<br /> Following the detection of hot－spot motion and spectral break in CTD 93，we examined both kinematic and synchrotron ages of the innermost radio source of 3 C 84 using VLBA．Since 3C 84 is One of the nearest powerful CSOs，detailed kinematics and spatial distribution of break frequency are revealed. Measurements of hot spot motion with respect to the core over 4.5 yr resulted in the advance velocity of 0.43±0.06<i>c</i>. The resultant kinematic age is 33±5 yr in 2000. The radio－lobe spectra also show a high-frequency steepening due to synchrotron aging．The break frequency decreases with the distance from the hot spot. The lowest break frequency of 2.3±1.4 GHz is occurred near the core． Assuming the minimum－energy field，we derive the synchrotron age of 24±<sup>14</sup><sub>5</sub> yr in 1995．The kinematic and synchrotron ages are thus in very good agreement. Also these ages indicate that innermost radio lobe is associated with the 1959 outburst of activity.<br /> We proved that CTD 93 and 3C 84 are young radio sources from both kinematic－and synchrotron- aging studies. This is strong evidence for the hypothesis that CSOs are young radio sources. As well， the agreements between kinematic and synchrotron ages imply a validity of synchrotron－aging analysis under the minimum－energy assumption in CSOs. Assuming that minimum－energy assumption is also applicable to FRⅡsources，we found that an averaged expansion velocity of FRⅡ sources is ～0.05<i>c</i>. This is comparable to an averaged CSOs’ expansion velocity of ～0.1<i>c</i>. This implies that expansion velocity of radio lobe does not strongly depend on the linear size of radio source, if we allow that CSOs evolve into FRⅡsources.<br /> Finally，we examined the physical property of hot spots for a large number of radio galaxies to reveal the relation among CSOs，MSOs，and FRⅡ sources. The hot spot luminosity of CSOs and MSOs are almost equivalent to that of FRⅡ sources, indicating that the jet power of CSOs and MSOs is favorably comparable to that of FRⅡsources. The hot spot pressure and radius show simple power- law changes as expected from the dynamical evolution model of the hotspot. This is a supporting evidence for evolutional sequence from CSOs to MSOs to FRⅡ sources．<br /> Overall results strongly argue that CSOs are young extragalactic radio sources that are potentially able to evolve into FRⅡ sources through MSOs. |
| 所蔵 |
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値 |
有 |
要旨・審査要旨 (305.6 kB)
