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整体负反馈中的局部正反馈:FIRE宇宙学模拟中类星风对恒星形成的影响

Local positive feedback in the overall negative: the impact of quasar winds on star formation in the FIRE cosmological simulations

Jonathan Mercedes-Feliz, Daniel Anglés-Alcázar, Christopher C. Hayward, Rachel K. Cochrane, Bryan A. Terrazas, Sarah Wellons, Alexander J. Richings, Claude-Andr… 展开作者

Jonathan Mercedes-Feliz, Daniel Anglés-Alcázar, Christopher C. Hayward, Rachel K. Cochrane, Bryan A. Terrazas, Sarah Wellons, Alexander J. Richings, Claude-André Faucher-Giguère, Jorge Moreno, Kung Yi Su, Philip F. Hopkins, Eliot Quataert, Dušan Kereš

AI总结:

本研究利用FIRE项目的宇宙学模拟,发现类星风虽整体抑制大质量星系恒星形成(预防型反馈主导),但也存在局部正反馈特征,且后者对星系全局增长作用有限。

摘要:

吸积超大质量黑洞产生的负反馈被认为是抑制大质量星系恒星形成并使其熄灭的关键因素。然而,若干模型与观测结果表明,黑洞反馈可能存在正面效应,即通过将星际介质气体压缩至更高密度来触发恒星形成。本研究利用“真实环境反馈”(Feedback In Realistic Environments, FIRE)项目的宇宙学流体动力学模拟,探究黑洞反馈的双重作用,模拟中采用了一种全新的超精细吸积盘风实现方案。我们聚焦于红移$z \sim 2$处的一个大质量恒星形成星系(暗物质晕质量$M_{\rm halo} \sim 10^{12.5} \\\\, {\rm M}_{\odot}$),研究发现动能功率约为$10^{46}$ erg/s的强类星风持续作用超过20 Myr后,会推动中心气体空腔的形成,并能大幅降低整个星系盘的恒星形成率面密度。恒星形成的抑制主要源于可形成恒星的气体总量减少,而非直接排空已有的恒星形成气体储库(即预防型反馈主导了喷发型反馈)。尽管类星风存在全局负向影响,我们仍识别出若干局部正反馈的合理特征,包括:(1)风主导区域与恒星形成团块呈空间反相关;(2)空腔边缘附近被压缩气体的局部恒星形成效率更高;(3)外流物质对局部恒星形成的贡献有所提升。在类星风存在的环境中形成的恒星,往往诞生于更大的径向距离处。我们的结果表明,活动星系核(AGN)的正、负反馈可以在星系中共存,但局部恒星形成的正触发效应对星系整体增长的作用较小。

英文摘要:

Negative feedback from accreting supermassive black holes is regarded as a key ingredient in suppressing star formation and quenching massive galaxies. However, several models and observations suggest that black hole feedback may have a positive effect, triggering star formation by compressing interstellar medium gas to higher densities. We investigate the dual role of black hole feedback using cosmological hydrodynamic simulations from the Feedback In Realistic Environments (FIRE) project, including a novel implementation of hyper-refined accretion-disc winds. Focusing on a massive, star-forming galaxy at $z \sim 2$ ($M_{\rm halo} \sim 10^{12.5} \, {\rm M}_{\odot}$), we show that strong quasar winds with kinetic power $\sim$10$^{46}$ erg/s acting for $>$20$\,$Myr drive the formation of a central gas cavity and can dramatically reduce the star formation rate surface density across the galaxy disc. The suppression of star formation is primarily driven by reducing the amount of gas that can become star-forming, compared to directly evacuating the pre-existing star-forming gas reservoir (preventive feedback dominates over ejective feedback). Despite the global negative impact of quasar winds, we identify several plausible signatures of local positive feedback, including: (1) spatial anti-correlation of wind-dominated regions and star-forming clumps, (2) higher local star formation efficiency in compressed gas near the edge of the cavity, and (3) increased local contribution of outflowing material to star formation. Stars forming under the presence of quasar winds tend to do so at larger radial distances. Our results suggest that positive and negative AGN feedback can coexist in galaxies, but local positive triggering of star formation plays a minor role in global galaxy growth.

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