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首页> 外文期刊>The Astrophysical journal >COSMOLOGICAL GROWTH HISTORY OF SUPERMASSIVE BLACK HOLES AND DEMOGRAPHICS IN THE HIGH-z UNIVERSE: DO LYMAN BREAK GALAXIES HAVE SUPERMASSIVE BLACK HOLES?
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COSMOLOGICAL GROWTH HISTORY OF SUPERMASSIVE BLACK HOLES AND DEMOGRAPHICS IN THE HIGH-z UNIVERSE: DO LYMAN BREAK GALAXIES HAVE SUPERMASSIVE BLACK HOLES?

机译：高z宇宙的超大规模黑洞的宇宙学发展史和人口统计学：莱曼断裂星系是否有超大规模黑洞？

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We study the demographics of supermassive black holes (SMBHs) in the local and high-z universe. We use the continuity equation of the population of SMBHs as the leading principle. We consider three physical processes for the growth of SMBHs: mass accretion, mergers, and direct formation of SMBHs. The mass accretion history of SMBHs is estimated by the hard X-ray luminosity functions (HXLFs) of active galactic nuclei (AGNs). First, we compare the mass accretion history at z > 0 with optical luminosity functions (OLFs) of QSOs previously studied and that with HXLFs. We conclude that the constraints on parameters of mass accretion (energy conversion efficiency, ε, and Eddington ratio, f_(Edd)) based on the continuity equation appear to be adequate using HXLFs rather than OLFs. The sub-Eddington case (f_(Edd) < 1) is allowed only when we use HXLFs. Next, we extend the formulation and can obtain the upper limit of the cumulative mass density of SMBHs at any redshift. For an application, we examine if Lyman break galaxies (LBGs) at z ～ 3 already have SMBHs in their centers, which is suggested by recent observations. We tentatively assume the presence of SMBHs in LBGs and that their mass, M_(BH), is proportional to the stellar mass of LBGs, M_*, with the mass ratio ξ= M_(BH)/M_*. If most LBGs already have massive SMBHs at z ～ 3, the resultant mass density of SMBHs at z ～ 0 should exceed the observational estimate because such SMBHs should further grow by accretion. Therefore, we can set the upper limit of the probability that one LBG has SMBHs. Since the merger rates and direct formation rates of SMBHs are uncertain, we consider two limiting cases: (1) mergers and/or direct formations are not negligible compared with mass accretion, and (2) mass accretion is the dominant process to grow the SMBHs. The special conditions should be met in order that a large part of LBGs have SMBHs in both cases. In case 1, we may assume the constant parameters of mass accretion of AGNs for simplicity. Then, large energy conversion efficiency and frequent mergers and/or direct formations at z > 3 are needed so that a large part of LBGs have SMBHs with ξ = 0.002-0.005. In case 2, on the other hand, energy conversion efficiency should be mass dependent and the constraint is strict; the fraction of LBGs that have SMBHs must be less than 10%-40%. In both cases, the possibility that nearly all LBGs have SMBHs with large mass ratio, such as ξ ≥ 0.005, is reliably ruled out.
机译：我们研究了本地和高z宇宙中超大规模黑洞（SMBH）的人口统计资料。我们使用SMBHs种群的连续性方程作为主导原则。我们考虑了SMBHs成长的三个物理过程：大规模增长，合并和SMBHs的直接形成。 SMBHs的质量积聚历史是通过活动银河核（AGNs）的硬X射线光度函数（HXLFs）估算的。首先，我们将z> 0时的质量累积历史与先前研究的QSO和HXLF的光学发光度函数（OLF）进行比较。我们得出的结论是，使用HXLF而不是OLF，基于连续性方程对质量积聚参数（能量转换效率ε和爱丁顿比率f_（Edd））的约束似乎足够。仅当使用HXLF时，才允许使用子爱丁顿情况（f_（Edd）<1）。接下来，我们扩展公式，并可以在任何红移下获得SMBHs累积质量密度的上限。对于一个应用，我们检查z〜3处的莱曼破裂星系（LBG）是否已经在其中心具有SMBH，这是最近的观察结果所暗示的。我们暂时假设LBG中存在SMBH，并且它们的质量M_（BH）与LBG的恒星质量M_ *成比例，质量比ξ= M_（BH）/ M_ *。如果大多数LBG在z〜3时已经具有大量SMBH，则在z〜0时SMBH的合成质量密度应超过观测值，因为这样的SMBHs应通过吸积进一步增长。因此，我们可以设置一个LBG具有SMBH的概率的上限。由于SMBHs的合并率和直接形成率尚不确定，因此我们考虑两个局限性情况：（1）与大规模增加相比，合并和/或直接形成不可忽略，并且（2）大规模增加是SMBHs成长的主要过程。 。在两种情况下，都应满足特殊条件，以便大部分LBG具有SMBH。在情况1中，为简单起见，我们可以假定AGN的质量累积常数参数。然后，需要大的能量转换效率和z> 3时的频繁合并和/或直接形成，以使大部分LBG具有ξ= 0.002-0.005的SMBH。另一方面，在情况2中，能量转换效率应取决于质量，并且约束条件严格；具有SMBH的LBG的比例必须小于10％-40％。在这两种情况下，都可靠地排除了几乎所有LBG都有质量比较大的SMBH（例如ξ≥0.005）的可能性。

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  • 来源
    《The Astrophysical journal》 |2004年第1pt1期|p.139-150|共12页
  • 作者

    TAKASHI HOSOKAWA;

  • 作者单位

    Yukawa Institute for Theoretical Physics, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 天文学;
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