The Sloan Digital Sky Survey Reverberation Mapping Project: Estimating Masses of Black Holes in Quasars with Single-epoch Spectroscopy
The Sloan Digital Sky Survey Reverberation Mapping Project: Estimating Masses of Black Holes in Quasars with Single-epoch Spectroscopy
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DOI：
10.3847/1538-4357/abbc1c
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发表时间：
2020-11-01
影响因子：
4.9
通讯作者：
Vestergaard, Marianne
中科院分区：
文献类型：
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作者：
Bonta, Elena Dalla;Peterson, Bradley M.;Vestergaard, Marianne
众所周知，活动星系核(AGN)的混响图谱揭示了AGN光度与宽线区域大小之间的关系，利用这一关系，结合宽发射线的多普勒宽度，能够基于单一光谱估计活动核中心的黑洞质量。一个悬而未决的关键问题是用来表征线宽的参数的选择，要么是半高宽，要么是线散差西格玛(LINE)(线条轮廓的二阶矩的平方根)。我们在这里认为，半高宽的使用引入了一种偏差，拉长了质量尺度，使得高质量被高估，低质量被低估。在这里，我们研究了基于单个或“单历元”观测的活动星系核中黑洞质量的估计，特别是比较了基于谱线色散和半高宽的质量估计。我们证实了最近的发现，除了光度和线宽之外，还需要第三个参数来获得准确的质量，该参数似乎是爱丁顿比。我们给出了从Hβ波长4861和C IV波长1549的发射线估算黑洞质量的简化经验公式。虽然活动星系核在5100埃的连续光度通常被用来预测Hβ混响滞后，但我们表明，可以在不损失任何精度的情况下使用Hβ宽分量的光度，从而消除了准确解释宿主星系对观测光度的贡献的困难。
It is well known that reverberation mapping of active galactic nuclei (AGNs) reveals a relationship between AGN luminosity and the size of the broad-line region, and that use of this relationship, combined with the Doppler width of the broad emission line, enables an estimate of the mass of the black hole at the center of the active nucleus based on a single spectrum. An unresolved key issue is the choice of parameter used to characterize the line width, either FWHM or line dispersion sigma(line) (the square root of the second moment of the line profile). We argue here that use of FWHM introduces a bias, stretching the mass scale such that high masses are overestimated and low masses are underestimated. Here we investigate estimation of black hole masses in AGNs based on individual or "single-epoch" observations, with a particular emphasis in comparing mass estimates based on line dispersion and FWHM. We confirm the recent findings that, in addition to luminosity and line width, a third parameter is required to obtain accurate masses, and that parameter seems to be Eddington ratio. We present simplified empirical formulae for estimating black hole masses from the H beta lambda 4861 and C iv lambda 1549 emission lines. While the AGN continuum luminosity at 5100 angstrom is usually used to predict the H beta reverberation lag, we show that the luminosity of the H beta broad component can be used instead without any loss of precision, thus eliminating the difficulty of accurately accounting for the host-galaxy contribution to the observed luminosity.