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arXiv 2007.11475astro-ph.GA
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利用宽MgII、H $α$和H $β$线的偏振估算活动星系核中的超大质量黑洞质量

Estimating supermassive black hole masses in AGNs using polarization of broad MgII, H$α$ and H$β$ lines

Đorđe Savić, Luka Č. Popović, Elena Shablovinskaya, Viktor L. Afanasiev

摘要:

对于以赤道散射为主要宽线偏振机制的第1型活动星系核(AGN),通过跟踪开普勒运动的偏振面位置角,可以测量超大质量黑洞的质量.到目前为止,这种方法已被用于30个对象,但仅用于H $α$发射线。我们探索了这种方法的可能性,用于确定SMBH质量使用偏振在宽发射线的Mg II $λ$ 2798 AA谱线的第一次。我们使用三维Monte Carlo辐射转移程序Stokes同时模拟了H $α$、H $β$和Mg II谱线的赤道散射。我们包括MgII宽线区域(BLR)的垂直流入和流出。我们发现H $α$和H $β$线的偏振态几乎相同,SMBH质量估计相差7%。对于Mg II线,我们发现,偏振角$φ$表现出一个额外的“平台”与一个常数$φ$,这偏离了纯开普勒运动的预期轮廓。使用Mg II线的SMBH质量估计值比从H $α$和H $β$线获得的SMBH质量估计值高35%。我们的模型表明,垂直流入和流出的BLR是更高或可比开普勒速度,这种方法可以应用作为一个第一近似获得SMBH质量。

英文摘要:

For type-1 active galactic nuclei (AGNs) for which the equatorial scattering is the dominant broad line polarization mechanism, it is possible to measure the supermassive black hole mass by tracing the Keplerian motion across the polarization plane positionangle. So far this method has been used for 30 objects but only for H$α$ emission line. We explore the possibilities this method for determining SMBH masses using polarization in broad emission lines by applying it for the first time to Mg II$λ$2798AA spectral line. We use 3D Monte Carlo radiative transfer code stokes for simultaneous modeling of equatorial scattering of H$α$, H$β$ and Mg II lines. We included vertical inflows and outflows in the MgII broad line region (BLR). We find that polarization states of H$α$ and H$β$ lines are almost identical and SMBH mass estimates differ by 7%. For Mg II line, we find that polarization angle $φ$ exhibits an additional "plateau" with a constant $φ$, which deviates than the profiles expected for pure Keplerian motion. SMBH mass estimates using Mg II line are higher by up to 35% than those obtained from H$α$ and H$β$ lines. Our model shows that for vertical inflows and outflows in the BLR that is higher or comparable to Keplerian velocity, this method can be applied as a first approximation for obtaining SMBH mass.

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