Gravitational Waves from Supermassive Black Hole Binaries in Ultraluminous Infrared Galaxies
Gravitational Waves from Supermassive Black Hole Binaries in Ultraluminous Infrared Galaxies
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DOI：
10.3847/2041-8213/aad8ad
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发表时间：
2018-05
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影响因子：
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通讯作者：
K. Inayoshi;K. Ichikawa;Z. Haiman
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文献类型：
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作者：
K. Inayoshi;K. Ichikawa;Z. Haiman
纳赫兹波段的引力波 (GW) 是了解星系核中超大质量黑洞 (SMBH) 宇宙学演化的重要工具。我们将高 z 超亮红外星系 (ULIRG) 中的SMBH 双星视为随机引力波背景 (GWB) 的来源。 ULIRG可能与含有SMBH的富含气体的星系合并有关，这些合并可能在星系的生命中最多发生一次，这与低红移下的多次干合并不同。采用完善的 ULIRG 样本，我们研究了由于这些星系中双星黑洞合并而产生的 GWB 特性。由于 ULIRG 群体在 z > 1.5 处达到峰值，因此即使 BH 合并延迟约 10 Gyr，GWB 的幅度也不会受到影响。尽管高 z ULIRG 很罕见，但我们从脉冲星计时阵列实验中发现了与上限的张力。这一结果表明，如果 ULIRG 的一小部分与 SMBH 双星相关，那么对于 ULIRG 的爱丁顿比 (λEdd) 及其寿命 (tlife) 的合理值，在哈勃时间内，ULIRG 中的二元 SMBH 不能合并。
Gravitational waves (GWs) in the nanohertz band are great tools for understanding the cosmological evolution of supermassive black holes (SMBHs) in galactic nuclei. We consider SMBH binaries in high-z ultraluminous infrared galaxies (ULIRGs) as sources of a stochastic GW background (GWB). ULIRGs are likely associated with gas-rich galaxy mergers containing SMBHs that possibly occur at most once in the life of galaxies, unlike multiple dry mergers at low redshift. Adopting a well-established sample of ULIRGs, we study the properties of the GWB due to coalescing binary SMBHs in these galaxies. Since the ULIRG population peaks at z > 1.5, the amplitude of the GWB is not affected even if BH mergers are delayed by as long as ∼10 Gyr. Despite the rarity of the high-z ULIRGs, we find a tension with the upper limits from pulsar timing array experiments. This result suggests that if a fraction of ULIRGs are associated with SMBH binaries, then no more than of the binary SMBHs in ULIRGs can merge within a Hubble time, for plausible values of the Eddington ratio of ULIRGs (λEdd) and their lifetime (tlife).