利用電波與近紅外線觀測資料研究活躍星系核的性質

On The Radio And Near-Infrared Properties of AGN Unification Model

黃志斌(Chih-Pin Huang)

指導教授 ： 黃崇源

國立中央大學/理學院/天文研究所/碩士(2006年)

摘要

在這篇論文中，我們分別藉由一電波波段（VLA FIRST）與一近 紅外波段（2MASS）的觀測資料，來研究活躍星系核（AGN）統一模 型（Unification Scheme）的特性。經由我們的研究，我們發現不 同類型的活躍星系核在電波20 公分與近紅外線波段經常會有不同的 表徵。 一般相信類星體（Quasar）分為電波強（Radio-loud）與電波 弱（Radio-quiet）兩類；這樣的概念在近年卻開始被質疑其真實性。 我們計算了所有類星體樣本的電波光學強度比（Radio to optical ratio），考慮了電波觀測的偵測極限，並加上生存分析（Survival Analysis）的佐證，我們發現上述類星體兩種分類還是有其統計意 義存在。我們也對窄發射線賽佛星系第一型（Narrow line Seyfert 1）樣本計算了其電波光學強度比，在其中發現兩個新的電波強窄發 射線賽佛星系第一型。除此之外，我們從電波光學強度比的研究中 也發現，窄發射線賽佛星系第一型的可見光強度整體高於普通賽佛 星系第一型。 在近紅外線的研究中，我們發現賽佛星系第一型的近紅外線顏 色（Color）整體上比較於賽佛星系第二型是偏紅的。我們認為這是 因為賽佛星系第二型的近紅外線輻射主要是來自於宿主星系（Host galaxy）與中心熱灰塵（Hot dust）；而賽佛星系第一型的近紅外線 輻射則是直接來自於中心黑洞的吸積。我們也發現窄發射線賽佛星 系第一型的近紅外線顏色又更紅於普通佛星系第一型，而窄發射線 賽佛星系第一型的近紅外偵測率（Detection rate）更是接近百分 之百。 另外，我們發現了低頻比艾拉克（LBL）天體的近紅外顏色普遍 紅於高頻比艾拉克（HBL）天體。我們並無法從這些天體吸收普線的 資料來建立灰塵吸收與其近紅外顏色之間的關係。由於艾福爾第一 型電波星系（FR I Radio galaxy）一般認為是比艾拉克天體的對應 星系（Counterpart），我們便直接分析艾福爾第一型電波星系的灰 塵影像來研究兩者的對應關係。我們發現究艾福爾第一型電波星系 的近紅外線顏色與上述兩種型態的比艾拉克天體都有差別，而我們 亦無法找到艾福爾第一型電波星系中心灰塵質量與其近紅外線顏色 之間的關係。

關鍵字

活躍星系核

並列摘要

We study unification schemes of AGNs by analyzing radio and near infrared data
obtained by correlating the Veron-Cetty & Veron AGN catalog with the 2MASS and
FIRST data archive. We have found diverse characteristics among various types of
AGNs at the radio and near infrared wavelengths.
The bimodal distribution of radio loudness for quasars has been challenged in
recent years. We found that the radio-to-optical ratio for our quasar sample would
show a bimodality only after we have considered those censored data using survival
analysis; indicating the challenge of the bimodal distribution might mainly caused by
detecting limits. We also estimate radio-to-optical ratio for narrow-line Seyfert
1(NLS1) and discover two new radio-loud NLS1s. We find that NLS1s are generally
among smaller ratios than normal Seyfert 1, which could be due to intrinsic stronger
optical emission from NLS1s.
From the results of 2MASS data, we find that Seyfert 1s are generally redder
than Seyfert 2s at NIR wavebands; we suggest that NIR emission from Seyfert 2s is
dominated by host galaxies and nuclear dusty tori, while that from Seyfert 1s is more
related to the active nuclei of the galaxies. Besides, we find that the NIR colors of
NLS1 is even redder than normal Seyfert 1, and the NIR detection rate of NLS1 is
almost 100We also show NIR-color difference between two types of BL Lac objects,
HBL and LBL. It has been suggested that the difference of the HBL and LBL is
caused by different dust absorption. However, we checked CaII and MgII line
absorption data and find poor correlation with NIR colors between these two samples.
Since FR I radio galaxies is generally assumed to be the host galaxies of BL Lac
objects, we further investigate s30 optical dust images of FR I radio galaxies to check
their unification with BL Lac objects at near infrared. We find that the FR I radio
galaxies have very different NIR colors from both HBL and LBL and show no
correlation between their dust mass and NIR colors.

並列關鍵字

AGN

參考文獻

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