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arXiv 1203.0601astro-ph.CO
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发光类星体单历元维里黑洞质量估计的比较

Comparing Single-Epoch Virial Black Hole Mass Estimators for Luminous Quasars

Yue Shen, Xin Liu

摘要:

单历元维里黑洞(BH)的质量估计,利用广泛的发射线已被例行应用于高红移类星体,以估计其BH质量。根据红移,不同的线估计(Halpha,Hbeta,MgII,CIV)通常用于光学/近红外光谱。在这里,我们使用一个均匀的样本的60个中等红移(z~1.5-2.2)SDSS类星体的光学和近红外光谱覆盖CIV通过H α调查不同的线估计之间的一致性。对于我们的样本探测的高光度区域(L_5100>10^45.4 erg/s),我们严格比较了restframe UV谱线估计值(CIV、CIII]和MgII)与光学估计值(Hbeta和Halpha)在谱线宽度之间以及连续谱/谱线光度之间的相关性。L_1350和L_3000的连续光度以及L_5100的宽线光度都有很好的相关性。我们发现,MgII的FWHM与巴耳末线的FWHM相关良好,并且MgII线估计量可以被校准以产生一致的维里质量估计与那些基于Hbeta/Halpha估计量的维里质量估计,从而扩展了较早的结果在较不明亮的物体上。CIV FWHM与巴耳末线FWHM的相关性较差,CIV和Hbeta FWHM之间的散射由不可约部分(~0.12 dex)和与CIV质心相对于Hbeta的蓝移相关的部分组成。发现CIII FWHM与CIV FWHM相关,因此也与Hbeta FWHM相关性差。虽然CIV和CIII]线可以被校准以产生一致的维里质量估计值作为平均值,但是分散度显著大于MgII,并且在质量估计值中使用CIV/CIII] FWHM并没有改善与Hbeta估计值的一致性。(节录)

英文摘要:

Single-epoch virial black hole (BH) mass estimators utilizing broad emission lines have been routinely applied to high-redshift quasars to estimate their BH masses. Depending on the redshift, different line estimators (Halpha, Hbeta, MgII, CIV) are often used with optical/near-infrared spectroscopy. Here we use a homogeneous sample of 60 intermediate-redshift (z~1.5-2.2) SDSS quasars with optical and near-infrared spectra covering CIV through Halpha to investigate the consistency between different line estimators. We critically compare restframe UV line estimators (CIV, CIII], and MgII) with optical estimators (Hbeta and Halpha) in terms of correlations between line widths and between continuum/line luminosities, for the high-luminosity regime (L_5100>10^45.4 erg/s) probed by our sample. The continuum luminosities of L_1350 and L_3000, and the broad line luminosities are well correlated with L_5100. We found that the MgII FWHM correlates well with the FWHMs of the Balmer lines, and that the MgII line estimator can be calibrated to yield consistent virial mass estimates with those based on the Hbeta/Halpha estimators, thus extending earlier results on less luminous objects. The CIV FWHM is poorly correlated with the Balmer line FWHMs, and the scatter between the CIV and Hbeta FWHMs consists of an irreducible part (~0.12 dex), and a part that correlates with the blueshift of the CIV centroid relative to that of Hbeta. The CIII] FWHM is found to correlate with the CIV FWHM, and hence is also poorly correlated with the Hbeta FWHM. While the CIV and CIII] lines can be calibrated to yield consistent virial mass estimates as Hbeta on average, the scatter is substantially larger than MgII, and the usage of CIV/CIII] FWHM in the mass estimators does not improve the agreement with the Hbeta estimator. (Abridged)

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