活动星系核中等宽度发射线研究

发布时间：2018-04-08 10:30

  本文选题：活动星系核　切入点：黑洞　出处：《中国科学技术大学》2016年博士论文

【摘要】：尘埃环是活动星系核统一模型的关键结构成分。然而,人们对尘埃环的研究主要局限在尘埃的红外热辐射上,而对尘埃环中的气体辐射了解很少。在统一模型的框架下,尘埃环处的气体在电离连续谱的照射下,通过光致电离过程可以产生丰富的紫外、光学发射线。发射线的宽度(FWHM～2000 km s-1)介于宽发射线(broad emission lines,缩写BELs)和窄发射线(narrow emission lines,缩写NELs)之间。我们称之为中等宽度发射线(intermediate-width emission lines,缩写IELs).本文在前人对IEL研究的基础之上，展开以下系列工作。IEL研究的最大困难在于谱线轮廓分解的不确定性。我们借鉴日冕仪原理,在一个部分遮蔽类星体OI 287中,利用尘埃环作为天然“日冕仪”将紫外波段BEL严重消光,从而探测到显著的IEL。在维里化假设下,我们发现中等宽度发射线区(intermediate-width emission line region,缩写IELR)到中心黑洞的距离(～1.3 pc)与尘埃环内半径基本吻合。光致电离模型计算表明,IELR气体的密度(～108.8-109.4 cm-3),与通常尘埃环内表面处的密度基本一致。这些结果表明IEL很可能是产生于尘埃环内表面被中心电离源照射的气体。类似OI 287的天体可以在半遮蔽类星体中大量发现。这说明IEL是可以广泛存在的,并为IEL的深入研究奠定了观测基础。IEL提供了诊断尘埃环处气体物理性质新的途径。在类星体SDSS J2324-0946的光谱中,一个线宽FWHM≈2000km s-1的IEL成分同时出现允许线Lyαγ1216、CⅣλ1549、半禁线CⅢ]λ1909、以及禁线[OⅢ]λλ4959,5007中。借助光致电离模型计算,我们估计这个类星体尘埃环处发射气体的物理性质,如氢的密度nH～106.2-6.3 cm-3、距离中心电离源的距离35～35-50pc、覆盖因子CF～6%、以及～4%倍小麦云的尘气比。IEL拓宽了人们了解尘埃环的手段,与传统红外SED拟合方法相比,可以获取更多关于尘埃环的物理特性。利用HST和SDSS等光谱数据,我们在低红移构建了同时有静止系紫外和光学光谱的Ⅰ型活动星系核样本。对该样本的分析结果显示,在维里化假设下IELR到中心黑洞的距离与尘埃环内半径在统计意义上基本一致。这表明尘埃环的内表面是产生IEL的主要位置。根据这个结果,我们进而得到利用IEL测量黑洞质量的公式。由于IEL可以在Lya和C IV等紫外发射线中得到,这种方法对于在高红移宇宙测量黑洞质量尤为重要。此外,IEL影响使用BEL线宽对黑洞质量的测量。将IEL从发射线中扣除可以显著改善利用BEL线宽测量黑洞质量的精度。
[Abstract]:Dust ring is a key structural component of the unified model of active galactic nuclei (AGNs).However, the study of dust ring is mainly confined to the infrared thermal radiation of dust, but little is known about the gas radiation in dust ring.In the framework of the unified model, the gas in the dust ring can produce abundant ultraviolet and optical emission lines by photoionization under the irradiation of continuous ionization spectrum.The width of the emission line is between broad emission lines (abbreviated as BELs) and narrow emission lines (abbreviated as NELs).We call it intermediate-width emission lines.On the basis of previous studies on IEL, the main difficulty of the following series of work, I. e., is the uncertainty of spectral contour decomposition.Based on the principle of coronal apparatus, in a partially obscured quasar OI287, we use the dust ring as a natural coronal instrument to seriously extinction the ultraviolet band BEL and detect the remarkable BEL.On the assumption of virization, we find that the distance from intermediate width emission line region (IELR) to the central black hole is 1.3 pc.) and the inner radius of the dust ring is basically consistent.The calculation of photoionization model shows that the density of IELR gas is 108.8-109.4 cm ~ (-3), which is basically consistent with the density at the inner surface of the dust ring.These results suggest that IEL probably originated from the inner surface of the dust ring irradiated by a central ionization source.Objects like OI 287 can be found in a large number of semi-shadowed quasars.This indicates that IEL can exist widely and provides a new way to diagnose the physical properties of gas in the dust ring for the further study of IEL.In the spectra of quasar SDSS J2324-0946, an IEL component with a linewidth of FWHM 鈮，

本文编号：1721215