Cosmological hydrodynamical simulations with calibrated non-universal initial mass functions

该项目旨在分析在现代大型流体动力学模拟中实施校准的可变恒星初始质量函数(IMF)如何影响更广泛的银河系性质。一种通用的IMF固定了恒星群内的质量分布，而不受恒星形成的条件的影响。这在星系形成模型中是一个被广泛接受的近似值，但最近对高质量早期类型星系(ETG)的观测表明，与银河系相比，它们的质光比过高。通过调整IMF以允许过多的低质量矮星(使IMF质量自下而上)和/或恒星残留物(使IMF质量自上而下)，从而在不改变恒星光度的情况下增加ETGs中恒星的质量，可以纠正质量-光过剩(MLE)。在星系形成模型中实施解释观测到的MLE的可变IMF将随后影响恒星反馈和恒星形成速率以及其他星系过程，这意味着必须改变模拟并自我运行，以便准确分析可变IMF可能如何影响星系的演化。为此，该项目将根据观测到的MLE关系校准一个可变的IMF，并分析将该IMF纳入最先进的流体动力学模拟如何影响星系的性质。

This project aims to analyse how implementing a calibrated variable stellar initial mass function (IMF) into a modern large-scale hydrodynamical simulation affects wider galactic properties. A universal IMF fixes the distribution of mass within a stellar population independent of the conditions under which the stars formed. This is a widely accepted approximation in galaxy formation models, but recent observations of high-mass early-type galaxies (ETGs) indicate excesses in their mass-to-light ratios in comparison to the Milky Way. The mass-to-light excess (MLE) can be corrected by adapting the IMF to allow an overabundance of low-mass dwarf stars (making the IMF bottom-heavy in mass) and/ or stellar remnants (making the IMF top-heavy) such that the mass in stars in ETGs is increased without altering the luminosity of the stars. Implementing a variable IMF that explains the observed MLE into a galaxy formation model will subsequently affect stellar feedback and stellar formation rates among other galactic processes, meaning that simulations must be altered and run self-consistently in order to accurately analyse how a variable IMF may affect the evolution of galaxies. To this end, this project will calibrate a variable IMF based on observed MLE relations and analyse how incorporating this IMF into a state-of-the-art hydrodynamical simulation affects galaxy properties.