Protoquasars: Physical States and Observable Properties
Protoquasars: Physical States and Observable Properties
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DOI：
10.1086/345085
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发表时间：
2002-09
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影响因子：
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通讯作者：
N. Kawakatu;M. Umemura;M. Mori
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作者：
N. Kawakatu;M. Umemura;M. Mori
基于黑洞（BH）生长的辐射流体动力学模型，结合类星体（QSO）早期宿主星系的化学演化，建立了类星体BH与宿主星系的协同演化模型.结果发现，在一个星系风历元之后，光度在几个108年的时间尺度内从主星系核主导阶段转移到活动星系核主导阶段（QSO阶段）。前一阶段对应于黑洞成长的早期阶段，可被视为“类星体原型”阶段。它具有以下可观测的特征：（1）宽发射线比普通类星体窄，通常小于1500 km s-1。(2)BH与凸起的质量比MBH/M凸起在10-5.3至10-3.9的范围内。(3)宿主星系比类星体的宿主星系蓝，在静止波段的B-V色和观测波段的V-K色中大约蓝0.5等，假设星系形成红移为zf = 3-5。(4)星系核中气体的金属丰度为~8 Z嫌，恒星的金属丰度按主光度加权为~3 Z嫌。(5)中心的大质量BH（质量约107 M）被一个大质量尘埃盘（质量大于108 M）包围，这可能会在侧面视图中掩盖核心，使其成为2型核心。通过将这些预测与最近的观测结果进行比较，射电星系可能是原类星体的候选者。此外，预计原类星体阶段之前是一个光学厚的阶段，这可能对应于超亮红外星系（ULIRGs）。在这一阶段，MBH/Mbulge预计将远小于10-3，并随着金属丰度的增加而增加。此外，光学薄的恒星形成星系的ULIRGs的前体被预测。这些星系可能处于莱曼破裂星系（LBG）或Lyα发射体的组装阶段。
Based on the radiation hydrodynamic model for black hole (BH) growth and incorporating the chemical evolution of the early-type host galaxy, we construct the coevolution model of the quasar (QSO) BH and host galaxy. As a result, it is found that after a galactic wind epoch, the luminosity is shifted from the host-dominant phase to the active galactic nucleus-dominant phase (QSO phase) in the timescale of a few 108 yr. The former phase corresponds to the early stage of a growing BH and can be regarded as a "proto-QSO" phase. It has observable characteristic properties as follows: (1) The broad emission lines are narrower than those of ordinary QSOs and are typically less than 1500 km s-1. (2) The BH-to-bulge mass ratio, MBH/Mbulge, is in the range of 10-5.3 to 10-3.9. (3) Host galaxies are bluer than QSO hosts, by about 0.5 mag in the colors B-V at the rest bands and V-K at the observed bands, with assumed galaxy formation redshifts of zf = 3-5. (4) The metallicity of gas in the galactic nuclei is ~8 Z☉ and that of stars weighted by the host luminosity is ~3 Z☉. (5) The central massive BH (≃107 M☉) is surrounded by a massive dusty disk (>108 M☉), which may obscure the nucleus in the edge-on view and make a type 2 nucleus. By comparing these predictions with recent observations, radio galaxies are a possible candidate for proto-QSOs. Also, it is anticipated that the proto-QSO phase is preceded by an optically thick phase, which may correspond to ultraluminous infrared galaxies (ULIRGs). In this phase, MBH/Mbulge is predicted to be much less than 10-3 and to grow with metallicity. Moreover, as precursors of ULIRGs, optically thin star-forming galaxies are predicted. These may be in the assembly phase of Lyman break galaxies (LBGs) or Lyα emitters.