JWST时代用于增强早期结构形成的瞬态早期类暗能量动力学机制
Transient Early Dark Energy-Like Dynamics as a Mechanism for Enhanced Early Structure Formation in the JWST Era
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中文总结 AI 辅助
针对JWST发现的高红移大质量星系，研究提出亚主导暗物质组分的瞬态类早期暗能量动力学机制，可增强早期暗物质晕形成，降低恒星形成效率以匹配观测结果。
中文摘要 AI 辅助
詹姆斯·韦布空间望远镜（JWST）在红移z≳10处发现大质量星系，重新引发了人们对能增强早期结构形成同时保留标准ΛCDM模型成功大尺度预测的宇宙学机制的兴趣。我们研究一种唯象场景：一种奇异暗物质物种在辐射主导时期（10⁻⁷≲a≲10⁻⁵）可经历瞬态类早期暗能量阶段，之后回归无压冷暗物质状态。我们利用广义暗物质框架对该物种建模，根据CMB、BAO和Ia型超新星数据，该物种被限制在总暗物质组分的亚百分比份额内。其背景和扰动动力学由随时间变化的状态方程w(a)，以及随时间和尺度变化的声速平方c_s²(a,k)表征。这种临时负状态方程，结合我们的唯象压强响应方案，会引发有限区间的负有效声速平方，进而在有限共动尺度范围内触发由不稳定性驱动的密度扰动增长，从而增强早期暗物质晕的形成。我们发现，与标准ΛCDM情景相比，增强的暗物质晕丰度可大幅降低重现JWST观测星系丰度所需的恒星形成效率，尤其在更高红移处。我们的结果表明，亚主导暗物质组分中的瞬态类早期暗能量动力学为增强早期结构形成提供了可行机制，并为解释JWST及未来巡天观测到的高红移星系丰度提供了新框架。
英文摘要
The discovery of massive galaxies at redshifts $z\gtrsim10$ by the James Webb Space Telescope (JWST) has renewed interest in cosmological mechanisms capable of enhancing early structure formation while preserving the successful large-scale predictions of the standard $Λ$CDM model. We investigate a phenomenological scenario in which an exotic dark matter species can undergo a transient early dark energy-like phase during the radiation-dominated era ($10^{-7}\lesssim a\lesssim10^{-5}$) before reverting to pressureless cold dark matter. We utilize the generalized dark matter framework to model this species, which is restricted to a sub-percent fraction of the total dark matter component by CMB, BAO and Type Ia supernova data. Its background and perturbation dynamics are characterized by a time-dependent equation of state, $w(a)$, and a time- as well as scale-dependent sound speed, $c_s^2(a,k)$. The temporary negative equation of state, combined with our phenomenological pressure-response prescription, induces a finite interval of negative effective sound speed squared. This triggers an instability-driven growth of density perturbations over a limited range of comoving scales, thereby enhancing the formation of early dark matter halos. We find that the enhanced halo abundance can substantially reduce the star-formation efficiencies required to reproduce the observed abundance of JWST galaxies relative to the standard $Λ$CDM scenario, especially at higher redshifts. Our results demonstrate that transient early dark energy-like dynamics in a subdominant dark matter component provide a viable mechanism for enhancing early structure formation and offer a new framework for interpreting the abundance of high-redshift galaxies observed by JWST and future surveys.
