活動(dòng)星系核的X射線觀測(cè)研究
發(fā)布時(shí)間：2018-08-31 07:32
【摘要】：活動(dòng)星系核(AGN)被認(rèn)為是宇宙中最亮的并且能持續(xù)發(fā)光的天體。大部份AGN都表現(xiàn)出很強(qiáng)的X射線輻射,因?yàn)锳GN的X射線起源于AGN的最內(nèi)區(qū),AGN的X射線觀測(cè)研究對(duì)于了解AGN的物理性質(zhì)十分重要。本文分別從AGN的寬FeKa發(fā)射線和X射線連續(xù)譜沒(méi)有吸收特征的Ⅱ型AGN兩個(gè)方面開(kāi)展研究。 AGN中心黑洞吸積盤上的高溫冕區(qū)產(chǎn)生的硬X冪律連續(xù)譜照射到吸移盤表面,被冷吸積盤物質(zhì)反射產(chǎn)生Fe Kα熒光發(fā)射線,受到引力紅移、多普勒效應(yīng)等影響,在觀測(cè)光譜中表現(xiàn)為6.4keV處寬而不對(duì)稱的復(fù)雜發(fā)射線輪廊,稱為寬Fe Ka發(fā)射線。寬Fe Ka發(fā)射線在很多AGN中被觀測(cè)到,是研究黑洞周圍物理性質(zhì)和物質(zhì)的幾何分布的重要途徑。在少數(shù)AGN中,寬Fe Ka發(fā)射線輪廓太向紅端延伸,不適用史瓦西黑洞模型,必須考慮極端克爾黑洞模型,此時(shí)黑洞周圍吸積盤寬Fe Ka發(fā)射線輻射區(qū)域內(nèi)半徑(假設(shè)延伸至黑洞最內(nèi)穩(wěn)定軌道,由黑洞自旋決定)可以更加靠近黑洞,引力紅移很強(qiáng),發(fā)射線的輪廓往紅端延伸,因此寬Fe Ka發(fā)射線輪廓是測(cè)量超大質(zhì)量黑洞自旋的有效手段。 然而,關(guān)于AGN的寬Fe Ka發(fā)射線的性質(zhì)存在劇烈爭(zhēng)辯,有種替代模型認(rèn)為觀測(cè)光譜中的寬Fe Ka發(fā)射線輪廓其實(shí)是X射線連續(xù)譜受到復(fù)雜電離吸收或者活動(dòng)星系核的部分覆蓋吸收造成的。寬Fe Ka發(fā)射線模型和替代模型在觀測(cè)上并沒(méi)有統(tǒng)計(jì)性區(qū)別,人們采取了很多手段,比如擬合更寬波段的觀測(cè)數(shù)據(jù)以精確吸收,研究沒(méi)有或者熱吸收非常弱的bare Seyfert AGN,檢測(cè)反射譜相對(duì)連續(xù)譜的滯后等,仍然沒(méi)有得出明確結(jié)論。這時(shí),分析Ⅱ型AGN的寬Fe Kα發(fā)射線是一種新的思路,因?yàn)樵谔娲Ｐ椭?Ⅰ型AGN的電離吸收有關(guān)鍵作用,而Ⅱ型AGN的X射線吸收由j冷物質(zhì)主導(dǎo),但是Ⅱ型AGN中寬Fe Ka發(fā)射線很少被觀測(cè)到。 我們發(fā)現(xiàn)Ⅱ型AGN IRAS00521-7054(?)的XMM觀測(cè)光譜中存在極強(qiáng)極寬Fe Kα發(fā)射線(靜止坐標(biāo)系下EW=1.3keV),紅端延仲至3keV,最佳擬合模型是laor模型或者kerrconv*reflionx模型,自旋參數(shù)0.97,表明IRAS00521-7054的中心黑洞是高速自旋的極端克爾黑洞。這是首次測(cè)量到一個(gè)Ⅱ型AGN中心黑洞的自旋。 需要注意的是,理論計(jì)算表明,一個(gè)密度恒定的盤狀結(jié)構(gòu)被冪律連續(xù)譜照亮?xí)r,反射只能夠產(chǎn)生等值寬度小于800ev的寬Fe Ka發(fā)射線。IRAS00521-7054兩次XMM觀測(cè)的發(fā)射線等值寬度都很大,這在以前的AGN觀測(cè)中極其少見(jiàn),僅僅Ⅰ型AGN MCG-06-30.15和1110707-495中被觀測(cè)到。一個(gè)可能的物理解釋是光線彎曲模型,當(dāng)硬X冪律連續(xù)潛輻射區(qū)域足夠靠近黑洞,強(qiáng)大的相對(duì)論引力效應(yīng)使我們觀測(cè)到很暗的X射線連續(xù)譜成分和穩(wěn)定的反射成分。 同時(shí),我們嘗試用不包括寬發(fā)射線的替代模型來(lái)擬合光譜,單成分的部分覆蓋熱/冷吸收模型被擬合優(yōu)度的卡方檢驗(yàn)簡(jiǎn)單排除。用雙吸收模型(1個(gè)吸收成分覆蓋100%,一個(gè)吸收成分部分覆蓋)來(lái)擬合光譜,擬合優(yōu)度的卡方檢驗(yàn)仍差于寬Fe Ka發(fā)射線模型(△χ2=9),并且擬合得到的吸收的冪律譜非常陡(譜指數(shù)г=2.8±0.1,大于99.7%XMM觀測(cè)到的AGN的譜指數(shù))。我們的結(jié)論是,IRAS00521-7054的寬Fe Ka發(fā)射線不太可能是由X射線連續(xù)譜的復(fù)雜吸收造成的。當(dāng)然要完全排除寬Fe Ka發(fā)射線的替代模型,我們需要更高質(zhì)量和更寬波段的X射線觀測(cè)。 我們的第二項(xiàng)研究工作是X波段沒(méi)有吸收特征的Ⅱ型AGN,出發(fā)點(diǎn)是AGN統(tǒng)一模型。按照AGN統(tǒng)一模型,Ⅰ型AGN和Ⅱ型AGN內(nèi)稟結(jié)構(gòu)相同,Ⅱ型AGN的光學(xué)光譜觀測(cè)不到寬發(fā)射線是因?yàn)閷捑�區(qū)在視線方向上被光學(xué)厚的塵埃環(huán)遮蔽,很多Ⅱ型AGN的偏振觀測(cè)和近紅外光譜觀測(cè)觀測(cè)到隱藏的寬線區(qū),對(duì)AGN統(tǒng)一模型給予了有力證明�？谇�,Ⅱ型AGN中一種新的類型,X波段沒(méi)有吸收的Ⅱ型AGN被陸續(xù)發(fā)現(xiàn),這些AGN的X射線連續(xù)譜經(jīng)過(guò)擬合基本沒(méi)有吸收或者吸收太小,不足以解釋寬線區(qū)的缺失,預(yù)示著寬線區(qū)可能不存在,這對(duì)AGN統(tǒng)一模型是一種挑戰(zhàn)。然而,精確的擬合AGN X-ray光譜是很困難的。一方面,AGN X-ray光譜吸收往往比一個(gè)簡(jiǎn)單的冪律譜復(fù)雜,在許多情況下,還需要考慮軟X-ray過(guò)剩,熱吸收,部分覆蓋吸收,散射成分,反射成分,寬鐵線等。另一方面,寄主星系在軟X-ray波段的污染也不可忽略,雖然更好質(zhì)量和/或更高的空間分辨率的觀測(cè)數(shù)據(jù),可以緩解這些困難,對(duì)大部分AGN的觀測(cè)來(lái)說(shuō),即使使用CHANDRA或者XMM,這些困難仍未根除。盡管某幾個(gè)X波段沒(méi)有吸收的Ⅱ型AGN是可信的,很多X波段沒(méi)有吸收特征的Ⅱ型AGN經(jīng)過(guò)高空間分辨率的觀測(cè),被證明其實(shí)是X波段被嚴(yán)重遮蔽。 區(qū)別于以前對(duì)個(gè)源的研究,在本文中我們系統(tǒng)的揭示了寄主星系軟x波段貢獻(xiàn)對(duì)Ⅱ型AGN X射線連續(xù)譜的影響。紅外波段的[OlV]25.89μm發(fā)射線光度已經(jīng)被證明可以表征AGN內(nèi)稟光度,[NeⅡ]/[OⅣ]的發(fā)射線光度比則被證明可以表征寄主星系活動(dòng)和核區(qū)活動(dòng)的相對(duì)強(qiáng)弱。我們比較了12個(gè)X射線連續(xù)譜沒(méi)有吸收特征的Ⅱ型AGN和29個(gè)X射線連續(xù)譜有吸收特征的Ⅱ型AGN,發(fā)現(xiàn)前者的[NeⅡ]/[OⅣ]發(fā)射線光度比明顯高于后者,表明X射線連續(xù)譜沒(méi)有吸收特征的Ⅱ型AGN,光譜中的寄主星系軟X波段貢獻(xiàn)比例更高,使連續(xù)譜的軟X波段抬高,譜型變陡,觀測(cè)最終得到?jīng)]有吸收特征的冪律連續(xù)譜。進(jìn)一步研究發(fā)現(xiàn),兩組AGN的[NeⅡ]發(fā)射線光度沒(méi)有明顯區(qū)別,前者的[OⅣ]發(fā)射線光度明顯低于后者。表明核區(qū)本征光度低的AGN更容易被寄主星系軟X波段貢獻(xiàn)干擾。另外我們由此引申出一個(gè)新的方法,通過(guò)比較恒星形成率經(jīng)驗(yàn)公式對(duì)應(yīng)的2-10kev流量和X波段2-10kev觀測(cè)流量,可以快速篩選出顯著被寄主星系污染的Ⅱ型AGN。
[Abstract]:Active Galactic Nucleus (AGN) is considered to be the brightest and persistently luminous object in the universe. Most AGNs exhibit strong X-ray radiation, because the X-rays of AGN originate in the innermost region of AGN. X-ray observations of AGN are very important for understanding the physical properties of AGN. Two aspects of absorption type II AGN are studied.
The hard X-ray power law continuous spectrum produced by the high temperature corona on the accretion disk of the central black hole of AGN irradiates the surface of the accretion disk and is reflected by the material of the cold accretion disk to produce the Fe Ka fluorescent emission line. Influenced by the gravitational red shift and Doppler effect, the complex emission line wheel gallery with a wide asymmetry at 6.4 keV is called the wide Fe Ka emission line. Ka emission lines are observed in many AGNs and are an important way to study the physical properties and the geometric distribution of matter around black holes. The radius (assuming that it extends to the innermost stable orbit of the black hole, determined by the spin of the black hole) can be closer to the black hole. The gravitational redshift is strong, and the profile of the emission line extends to the red end. Therefore, the profile of the wide Fe Ka emission line is an effective means to measure the spin of the supermassive black hole.
However, there is a fierce debate about the nature of the wide Fe Ka emission line of AGN. One alternative model suggests that the wide Fe Ka emission line profile in the observed spectrum is actually caused by the complex ionization absorption of the X-ray continuum or the partial coverage absorption of the active galactic nucleus. Many methods have been adopted, such as fitting broader band observations to accurately absorb, studying bare Seyfert AGN without or with very weak thermal absorption, and detecting the lag of the reflection spectrum relative to the continuum spectrum. At this time, it is a new idea to analyze the wide FeKa emission line of type II AGN, because it is a substitute. In the generation model, the ionization absorption of type I AGN is critical, while the X-ray absorption of type II AGN is dominated by J cold matter, but the Fe-Ka emission lines of type II AGN are rarely observed.
We find that there are very strong and extremely wide FeKa emission lines (EW = 1.3 keV in the stationary coordinate system) in the XMM spectra of type II AGN IRAS00521-7054 (?), and the red end is extended to 3 keV. The best fitting model is laor kerrconv * reflionx model. The spin parameter is 0.97, which indicates that the central black hole of IRAS00521-7054 is an extremely Kerr black hole with high speed spin. For the first time, the spin of a type II AGN center black hole is measured.
It should be noted that when a disc structure with constant density is illuminated by a power law continuous spectrum, the reflection can only produce a wide Fe Ka emission line with an equivalent width of less than 800ev. A possible physical explanation is the ray bending model. When the hard X-power-law continuous submarine radiation region is close enough to a black hole, strong relativistic gravitational effects allow us to observe very dark X-ray continuum components and stable reflection components.
At the same time, we try to fit the spectra by using an alternative model that does not include a wide emission line. The single-component partially covered thermal/cold absorption model is simply excluded by the chi-square test of goodness-of-fit. The emission line model (2 = 9) and the power law spectra of the absorption obtained by fitting are very steep (spectral exponent_ = 2.8 + 0.1, greater than the AGN spectral exponent observed by 99.7% XMM). Our conclusion is that the wide Fe-Ka emission line of IRAS 00521-7054 is unlikely to be caused by the complex absorption of the X-ray continuum spectrum. We need higher quality and wider band X ray observations.
Our second research work is Type II AGN with no absorption characteristics in X-band. The starting point is the AGN unified model. According to the AGN unified model, the intrinsic structure of Type I AGN and Type II AGN are the same. The optical spectrum of Type II AGN can not observe the wide emission line because the wide line area is covered by the optical thick dust ring in the line of sight, and many Type II AGN are biased. Before the mouth, a new type of AGN in type II AGN, type II AGN without absorption in X-band, was discovered successively. The X-ray continuum spectra of these AGNs were basically not absorbed or absorbed too small to explain the absence of the wide-line region after fitting. However, it is difficult to fit AGN X-ray spectra accurately. On the one hand, AGN X-ray spectra are often more complex than a simple power-law spectra. In many cases, soft X-ray excess, thermal absorption, partially covered absorption, scattering component, and reflection component should also be considered. On the other hand, the contamination of host galaxies in soft X-ray bands can not be neglected, although better quality and/or higher spatial resolution observations can alleviate these difficulties. For most AGN observations, even with CHANDRA or XMM, these difficulties have not been eradicated. GN is credible, and many type II AGNs without absorption characteristics in X-band have been proved to be severely masked in X-band after high spatial resolution observations.
In this paper, we systematically reveal the influence of host galaxy soft X-band contribution on the type II AGN X-ray continuum spectrum, which is different from previous studies on individual sources. The infrared band [OlV] 25.89 micron emission line luminosity has been proved to be able to characterize the intrinsic luminosity of AGN, and the ratio of [Ne II]/[O IV] luminosity has been proved to be able to characterize the host galaxy activity. We compared 12 type II AGNs with 29 type II AGNs with absorption characteristics in X-ray continuum spectra, and found that the luminosity ratio of the emission line of the former was significantly higher than that of the latter, indicating that type II AGNs with no absorption characteristics in X-ray continuum spectra and the host galaxy soft X-ray spectra in the spectrum were soft. It is found that there is no significant difference between the two groups of AGN emission line luminosities, and the former is obviously lower than the latter. It shows that the AGN with low intrinsic luminosity in the nuclear region is easier to be sent. The soft X-band contribution interference of the host galaxy is also discussed. A new method is proposed to quickly screen out type II AGN which is significantly polluted by the host galaxy by comparing the 2-10 keV flow corresponding to the empirical formula of star formation rate with the 2-10 keV observed flow in the X-band.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2012
【分類號(hào)】：P152
本文編號(hào)：2214312
[Abstract]:Active Galactic Nucleus (AGN) is considered to be the brightest and persistently luminous object in the universe. Most AGNs exhibit strong X-ray radiation, because the X-rays of AGN originate in the innermost region of AGN. X-ray observations of AGN are very important for understanding the physical properties of AGN. Two aspects of absorption type II AGN are studied.
The hard X-ray power law continuous spectrum produced by the high temperature corona on the accretion disk of the central black hole of AGN irradiates the surface of the accretion disk and is reflected by the material of the cold accretion disk to produce the Fe Ka fluorescent emission line. Influenced by the gravitational red shift and Doppler effect, the complex emission line wheel gallery with a wide asymmetry at 6.4 keV is called the wide Fe Ka emission line. Ka emission lines are observed in many AGNs and are an important way to study the physical properties and the geometric distribution of matter around black holes. The radius (assuming that it extends to the innermost stable orbit of the black hole, determined by the spin of the black hole) can be closer to the black hole. The gravitational redshift is strong, and the profile of the emission line extends to the red end. Therefore, the profile of the wide Fe Ka emission line is an effective means to measure the spin of the supermassive black hole.
However, there is a fierce debate about the nature of the wide Fe Ka emission line of AGN. One alternative model suggests that the wide Fe Ka emission line profile in the observed spectrum is actually caused by the complex ionization absorption of the X-ray continuum or the partial coverage absorption of the active galactic nucleus. Many methods have been adopted, such as fitting broader band observations to accurately absorb, studying bare Seyfert AGN without or with very weak thermal absorption, and detecting the lag of the reflection spectrum relative to the continuum spectrum. At this time, it is a new idea to analyze the wide FeKa emission line of type II AGN, because it is a substitute. In the generation model, the ionization absorption of type I AGN is critical, while the X-ray absorption of type II AGN is dominated by J cold matter, but the Fe-Ka emission lines of type II AGN are rarely observed.
We find that there are very strong and extremely wide FeKa emission lines (EW = 1.3 keV in the stationary coordinate system) in the XMM spectra of type II AGN IRAS00521-7054 (?), and the red end is extended to 3 keV. The best fitting model is laor kerrconv * reflionx model. The spin parameter is 0.97, which indicates that the central black hole of IRAS00521-7054 is an extremely Kerr black hole with high speed spin. For the first time, the spin of a type II AGN center black hole is measured.
It should be noted that when a disc structure with constant density is illuminated by a power law continuous spectrum, the reflection can only produce a wide Fe Ka emission line with an equivalent width of less than 800ev. A possible physical explanation is the ray bending model. When the hard X-power-law continuous submarine radiation region is close enough to a black hole, strong relativistic gravitational effects allow us to observe very dark X-ray continuum components and stable reflection components.
At the same time, we try to fit the spectra by using an alternative model that does not include a wide emission line. The single-component partially covered thermal/cold absorption model is simply excluded by the chi-square test of goodness-of-fit. The emission line model (2 = 9) and the power law spectra of the absorption obtained by fitting are very steep (spectral exponent_ = 2.8 + 0.1, greater than the AGN spectral exponent observed by 99.7% XMM). Our conclusion is that the wide Fe-Ka emission line of IRAS 00521-7054 is unlikely to be caused by the complex absorption of the X-ray continuum spectrum. We need higher quality and wider band X ray observations.
Our second research work is Type II AGN with no absorption characteristics in X-band. The starting point is the AGN unified model. According to the AGN unified model, the intrinsic structure of Type I AGN and Type II AGN are the same. The optical spectrum of Type II AGN can not observe the wide emission line because the wide line area is covered by the optical thick dust ring in the line of sight, and many Type II AGN are biased. Before the mouth, a new type of AGN in type II AGN, type II AGN without absorption in X-band, was discovered successively. The X-ray continuum spectra of these AGNs were basically not absorbed or absorbed too small to explain the absence of the wide-line region after fitting. However, it is difficult to fit AGN X-ray spectra accurately. On the one hand, AGN X-ray spectra are often more complex than a simple power-law spectra. In many cases, soft X-ray excess, thermal absorption, partially covered absorption, scattering component, and reflection component should also be considered. On the other hand, the contamination of host galaxies in soft X-ray bands can not be neglected, although better quality and/or higher spatial resolution observations can alleviate these difficulties. For most AGN observations, even with CHANDRA or XMM, these difficulties have not been eradicated. GN is credible, and many type II AGNs without absorption characteristics in X-band have been proved to be severely masked in X-band after high spatial resolution observations.
In this paper, we systematically reveal the influence of host galaxy soft X-band contribution on the type II AGN X-ray continuum spectrum, which is different from previous studies on individual sources. The infrared band [OlV] 25.89 micron emission line luminosity has been proved to be able to characterize the intrinsic luminosity of AGN, and the ratio of [Ne II]/[O IV] luminosity has been proved to be able to characterize the host galaxy activity. We compared 12 type II AGNs with 29 type II AGNs with absorption characteristics in X-ray continuum spectra, and found that the luminosity ratio of the emission line of the former was significantly higher than that of the latter, indicating that type II AGNs with no absorption characteristics in X-ray continuum spectra and the host galaxy soft X-ray spectra in the spectrum were soft. It is found that there is no significant difference between the two groups of AGN emission line luminosities, and the former is obviously lower than the latter. It shows that the AGN with low intrinsic luminosity in the nuclear region is easier to be sent. The soft X-band contribution interference of the host galaxy is also discussed. A new method is proposed to quickly screen out type II AGN which is significantly polluted by the host galaxy by comparing the 2-10 keV flow corresponding to the empirical formula of star formation rate with the 2-10 keV observed flow in the X-band.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2012
【分類號(hào)】：P152
【引證文獻(xiàn)】
相關(guān)博士學(xué)位論文 前1條
1 劉秀平;基于信噪特征的X射線脈沖星信號(hào)去噪方法研究[D];西安電子科技大學(xué);2014年
相關(guān)碩士學(xué)位論文 前2條
1 趙仲毅;硬X射線低能探測(cè)器FPGA仿真測(cè)試與數(shù)據(jù)傳輸系統(tǒng)的研制[D];云南大學(xué);2015年
2 付艷紅;EMCCD用于X射線低能段信號(hào)采集系統(tǒng)的研制[D];云南大學(xué);2015年
，本文編號(hào)：2214312
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