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arXiv 1605.04023astro-ph.CO
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LIGO引力波探测、原始黑洞和近红外宇宙红外背景各向异性

LIGO gravitational wave detection, primordial black holes and the near-IR cosmic infrared background anisotropies

A. Kashlinsky

摘要:

LIGO发现了来自两个质量相似的合并黑洞(BH)的引力波,这再次引发了原始黑洞(PBH)构成暗物质(DM)的建议。如果是这样的话,PBH将增加一个泊松等曲率密度波动分量的通货膨胀产生的绝热密度波动。对于LIGO的BH参数,这个额外的分量将主导导致早期DM晕在z>10时崩溃的小尺度功率,其中第一个光源形成。我们量化的结果增加高Z丰度的崩溃晕,适合生产的第一代恒星和光源。早期晕丰度的显著增加自然可以解释观测到的源扣除近红外宇宙红外背景(CIB)波动,这不能用已知的星系群来解释。对于LIGO的BH参数,这种增加是这样的,观察到的CIB波动水平在2至5微米可以产生,如果只有一小部分的重子在崩溃的DM晕形成发光源。在坍缩晕中,气体吸积到这些PBH上,第一颗恒星也应该形成,这将直接解释CIB和软X射线中未解决的宇宙X射线背景之间观察到的高相干性。我们讨论的修改可能需要在第一个恒星形成的过程中,如果LIGO型黑洞确实弥补了大部分或所有的DM。只有当PBH构成DM的全部或至少大部分时,这些论点才有效,但同时,如果DM是由PBH构成的,则该机制似乎是不可避免的。

英文摘要:

LIGO's discovery of a gravitational wave from two merging black holes (BHs) of similar masses rekindled suggestions that primordial BHs (PBHs) make up the dark matter (DM). If so, PBHs would add a Poissonian isocurvature density fluctuation component to the inflation-produced adiabatic density fluctuations. For LIGO's BH parameters, this extra component would dominate the small-scale power responsible for collapse of early DM halos at z>10, where first luminous sources formed. We quantify the resultant increase in high-z abundances of collapsed halos that are suitable for producing the first generation of stars and luminous sources. The significantly increased abundance of the early halos would naturally explain the observed source-subtracted near-IR cosmic infrared background (CIB) fluctuations, which cannot be accounted for by known galaxy populations. For LIGO's BH parameters this increase is such that the observed CIB fluctuation levels at 2 to 5 micron can be produced if only a tiny fraction of baryons in the collapsed DM halos forms luminous sources. Gas accretion onto these PBHs in collapsed halos, where first stars should also form, would straightforwardly account for the observed high coherence between the CIB and unresolved cosmic X-ray background in soft X-rays. We discuss modifications possibly required in the processes of first star formation if LIGO-type BHs indeed make up the bulk or all of DM. The arguments are valid only if the PBHs make up all, or at least most, of DM, but at the same time the mechanism appears inevitable if DM is made of PBHs.

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