活动星系核的X射线观测研究
发布时间：2018-08-31 07:32
【摘要】：活动星系核(AGN)被认为是宇宙中最亮的并且能持续发光的天体。大部份AGN都表现出很强的X射线辐射,因为AGN的X射线起源于AGN的最内区,AGN的X射线观测研究对于了解AGN的物理性质十分重要。本文分别从AGN的宽FeKa发射线和X射线连续谱没有吸收特征的Ⅱ型AGN两个方面开展研究。 AGN中心黑洞吸积盘上的高温冕区产生的硬X幂律连续谱照射到吸移盘表面,被冷吸积盘物质反射产生Fe Kα荧光发射线,受到引力红移、多普勒效应等影响,在观测光谱中表现为6.4keV处宽而不对称的复杂发射线轮廊,称为宽Fe Ka发射线。宽Fe Ka发射线在很多AGN中被观测到,是研究黑洞周围物理性质和物质的几何分布的重要途径。在少数AGN中,宽Fe Ka发射线轮廓太向红端延伸,不适用史瓦西黑洞模型,必须考虑极端克尔黑洞模型,此时黑洞周围吸积盘宽Fe Ka发射线辐射区域内半径(假设延伸至黑洞最内稳定轨道,由黑洞自旋决定)可以更加靠近黑洞,引力红移很强,发射线的轮廓往红端延伸,因此宽Fe Ka发射线轮廓是测量超大质量黑洞自旋的有效手段。 然而,关于AGN的宽Fe Ka发射线的性质存在剧烈争辩,有种替代模型认为观测光谱中的宽Fe Ka发射线轮廓其实是X射线连续谱受到复杂电离吸收或者活动星系核的部分覆盖吸收造成的。宽Fe Ka发射线模型和替代模型在观测上并没有统计性区别,人们采取了很多手段,比如拟合更宽波段的观测数据以精确吸收,研究没有或者热吸收非常弱的bare Seyfert AGN,检测反射谱相对连续谱的滞后等,仍然没有得出明确结论。这时,分析Ⅱ型AGN的宽Fe Kα发射线是一种新的思路,因为在替代模型中,Ⅰ型AGN的电离吸收有关键作用,而Ⅱ型AGN的X射线吸收由j冷物质主导,但是Ⅱ型AGN中宽Fe Ka发射线很少被观测到。 我们发现Ⅱ型AGN IRAS00521-7054(?)的XMM观测光谱中存在极强极宽Fe Kα发射线(静止坐标系下EW=1.3keV),红端延仲至3keV,最佳拟合模型是laor模型或者kerrconv*reflionx模型,自旋参数0.97,表明IRAS00521-7054的中心黑洞是高速自旋的极端克尔黑洞。这是首次测量到一个Ⅱ型AGN中心黑洞的自旋。 需要注意的是,理论计算表明,一个密度恒定的盘状结构被幂律连续谱照亮时,反射只能够产生等值宽度小于800ev的宽Fe Ka发射线。IRAS00521-7054两次XMM观测的发射线等值宽度都很大,这在以前的AGN观测中极其少见,仅仅Ⅰ型AGN MCG-06-30.15和1110707-495中被观测到。一个可能的物理解释是光线弯曲模型,当硬X幂律连续潜辐射区域足够靠近黑洞,强大的相对论引力效应使我们观测到很暗的X射线连续谱成分和稳定的反射成分。 同时,我们尝试用不包括宽发射线的替代模型来拟合光谱,单成分的部分覆盖热/冷吸收模型被拟合优度的卡方检验简单排除。用双吸收模型(1个吸收成分覆盖100%,一个吸收成分部分覆盖)来拟合光谱,拟合优度的卡方检验仍差于宽Fe Ka发射线模型(△χ2=9),并且拟合得到的吸收的幂律谱非常陡(谱指数г=2.8±0.1,大于99.7%XMM观测到的AGN的谱指数)。我们的结论是,IRAS00521-7054的宽Fe Ka发射线不太可能是由X射线连续谱的复杂吸收造成的。当然要完全排除宽Fe Ka发射线的替代模型,我们需要更高质量和更宽波段的X射线观测。 我们的第二项研究工作是X波段没有吸收特征的Ⅱ型AGN,出发点是AGN统一模型。按照AGN统一模型,Ⅰ型AGN和Ⅱ型AGN内禀结构相同,Ⅱ型AGN的光学光谱观测不到宽发射线是因为宽线区在视线方向上被光学厚的尘埃环遮蔽,很多Ⅱ型AGN的偏振观测和近红外光谱观测观测到隐藏的宽线区,对AGN统一模型给予了有力证明。口前,Ⅱ型AGN中一种新的类型,X波段没有吸收的Ⅱ型AGN被陆续发现,这些AGN的X射线连续谱经过拟合基本没有吸收或者吸收太小,不足以解释宽线区的缺失,预示着宽线区可能不存在,这对AGN统一模型是一种挑战。然而,精确的拟合AGN X-ray光谱是很困难的。一方面,AGN X-ray光谱吸收往往比一个简单的幂律谱复杂,在许多情况下,还需要考虑软X-ray过剩,热吸收,部分覆盖吸收,散射成分,反射成分,宽铁线等。另一方面,寄主星系在软X-ray波段的污染也不可忽略,虽然更好质量和/或更高的空间分辨率的观测数据,可以缓解这些困难,对大部分AGN的观测来说,即使使用CHANDRA或者XMM,这些困难仍未根除。尽管某几个X波段没有吸收的Ⅱ型AGN是可信的,很多X波段没有吸收特征的Ⅱ型AGN经过高空间分辨率的观测,被证明其实是X波段被严重遮蔽。 区别于以前对个源的研究,在本文中我们系统的揭示了寄主星系软x波段贡献对Ⅱ型AGN X射线连续谱的影响。红外波段的[OlV]25.89μm发射线光度已经被证明可以表征AGN内禀光度,[NeⅡ]/[OⅣ]的发射线光度比则被证明可以表征寄主星系活动和核区活动的相对强弱。我们比较了12个X射线连续谱没有吸收特征的Ⅱ型AGN和29个X射线连续谱有吸收特征的Ⅱ型AGN,发现前者的[NeⅡ]/[OⅣ]发射线光度比明显高于后者,表明X射线连续谱没有吸收特征的Ⅱ型AGN,光谱中的寄主星系软X波段贡献比例更高,使连续谱的软X波段抬高,谱型变陡,观测最终得到没有吸收特征的幂律连续谱。进一步研究发现,两组AGN的[NeⅡ]发射线光度没有明显区别,前者的[OⅣ]发射线光度明显低于后者。表明核区本征光度低的AGN更容易被寄主星系软X波段贡献干扰。另外我们由此引申出一个新的方法,通过比较恒星形成率经验公式对应的2-10kev流量和X波段2-10kev观测流量,可以快速筛选出显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.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2012
【分类号】：P152
本文编号：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.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2012
【分类号】：P152
【引证文献】
相关博士学位论文 前1条
1 刘秀平;基于信噪特征的X射线脉冲星信号去噪方法研究[D];西安电子科技大学;2014年
相关硕士学位论文 前2条
1 赵仲毅;硬X射线低能探测器FPGA仿真测试与数据传输系统的研制[D];云南大学;2015年
2 付艳红;EMCCD用于X射线低能段信号采集系统的研制[D];云南大学;2015年
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