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

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题名:	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
作者:	黃志斌;Chih-Pin Huang
贡献者:	天文研究所
关键词:	活躍星系核;AGN
日期:	2006-06-21
上传时间:	2009-09-22 10:12:59 (UTC+8)
出版者:	國立中央大學圖書館
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。 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.
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