宽线活动星系核的单历元黑洞质量估算：用新方法重新校准Hbeta
Single-Epoch Black Hole Mass Estimators For Broad-Line Active Galactic Nuclei: Recalibrating Hbeta with A New Approach
摘要：
基于更新的44个邻近活动星系核（AGN）的Hbeta混响映射（RM）样本，提出了一种利用Hbeta区周围单历元（SE）AGN光谱计算的两个滤波光度估算黑洞（BH）质量的新方法.我们发现，这两个最佳过滤光度提取维里信息（宽线区域的大小和维里速度，BLR）的光谱，证明他们的使用在这个经验BH质量估计。与传统的SE BH质量估算器相比，这种新方法的主要优点是：1）它具有0.28 dex的较小的固有散射，相对于RM质量进行校准; 2）它在实践中非常简单，无需分解光谱; 3）即使在低信噪比光谱下，它也能产生明确和高度可重复的结果。这两种光度的组合也可以在一定程度上抵消由距离或通量校准中的不确定性可能引入的系统光度误差。此外，我们重新校准了传统的SE质量估计使用宽的Hbeta半高全宽（FWHM）和单色连续发光度在5100 A（L_5100）。我们发现，使用FWHM和L_5100上的最佳拟合斜率（分别来自拟合BLR半径-光度关系以及均方根线色散与SE FWHM之间的相关性），而不是简单的假设（例如，0.5对于L_5100和2对于FWHM）导致更精确的SE质量估计，相对于RM质量，将固有散射从0.41 dex改善到0.36 dex。我们比较了不同的估计，并讨论了它们的应用斯隆数字巡天（SDSS）类星体样本。由于目前RM样品的局限性，任何SE配方校准RM质量遥远的类星体的应用应谨慎对待。
英文摘要：
Based on an updated Hbeta reverberation mapping (RM) sample of 44 nearby active galactic nuclei (AGN), we propose a novel approach for black hole (BH) mass estimation using two filtered luminosities computed from single-epoch (SE) AGN spectra around the Hbeta region. We found that the two optimal-filter luminosities extract virial information (size and virial velocity of the broad line region, BLR) from the spectra, justifying their usage in this empirical BH mass estimator. The major advantages of this new recipe over traditional SE BH mass estimators utilizing continuum luminosity and broad line width are: 1) it has a smaller intrinsic scatter of 0.28 dex calibrated against RM masses; 2) it is extremely simple to use in practice, without any need to decompose the spectrum; 3) it produces unambiguous and highly repeatable results even with low signal-to-noise spectra. The combination of the two luminosities can also cancel out, to some extent, systematic luminosity errors potentially introduced by uncertainties in distance or flux calibration. In addition, we recalibrated the traditional SE mass estimators using broad Hbeta full width at half maximum (FWHM) and monochromatic continuum luminosity at 5100A (L_5100). We found that using the best-fit slopes on FWHM and L_5100 (derived from fitting the BLR radius-luminosity relation and the correlation between rms line dispersion and SE FWHM, respectively) rather than simple assumptions (e.g., 0.5 for L_5100 and 2 for FWHM) leads to more precise SE mass estimates, improving the intrinsic scatter from 0.41 dex to 0.36 dex with respect to the RM masses. We compared different estimators and discussed their applications to the Sloan Digital Sky Survey (SDSS) quasar sample. Due to the limitations of the current RM sample, application of any SE recipe calibrated against RM masses to distant quasars should be treated with caution.
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