We present an analysis of the R ≲ 1.5 kpc core regions of seven simulated Milky Way-mass galaxies, from the FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulation suite, for a finely sampled period (Δt = 2.2 Myr) of 22 Myr at z ≈ 0, and compare them with star formation rate (SFR) and gas surface density observations of the Milky Way’s Central Molecular Zone (CMZ). Despite not being tuned to reproduce the detailed structure of the CMZ, we find that four of these galaxies are consistent with CMZ observations at some point during this 22 Myr period. The galaxies presented here are not homogeneous in their central structures, roughly dividing into two morphological classes; (a) several of the galaxies have very asymmetric gas and SFR distributions, with intense (compact) starbursts occurring over a period of roughly 10 Myr, and structures on highly eccentric orbits through the CMZ, whereas (b) others have smoother gas and SFR distributions, with only slowly varying SFRs over the period analyzed. In class (a) centers, the orbital motion of gas and star-forming complexes across small apertures (R ≲ 150 pc, analogously ∣l∣ < 1 in the CMZ observations) contributes as much to tracers of star formation/dense gas appearing in those apertures, as the internal evolution of those structures does. These asymmetric/bursty galactic centers can simultaneously match CMZ gas and SFR observations, demonstrating that time-varying star formation can explain the CMZ’s low star formation efficiency.

我们提出的分析- [R七个模拟银河质量星系1.5 KPC纤芯区域≲，从FIRE-2（在现实环境反馈）宇宙放大模拟套件，对于精细地取样周期（Δ吨= 2.2秘耳），共22个Myr，位于z≈0，并将它们与银河系中央分子带（CMZ）的恒星形成率（SFR）和气体表面密度观测值进行比较。尽管未进行调整以重现CMZ的详细结构，但我们发现在这22个Myr期间的某个时刻，这些星系中有四个与CMZ观测值一致。这里介绍的星系在中心结构上不均一，大致分为两个形态学类别。（a）几个星系具有非常不对称的气体和SFR分布，在大约10 Myr的周期内发生强烈的（紧凑的）星爆，并且在通过CMZ的高度偏心轨道上形成结构，而（b）其他星系的气体和SFR则更平滑分布，在分析期间内SFR仅缓慢变化。在（a）类中心，ř ≲150 PC，类似于|升| <1中的CMZ观测）有助于尽可能多的恒星形成/出现在那些孔稠密气体示踪剂，如那些结构的内部进化一样。这些不对称/爆裂的银河中心可以同时匹配CMZ气体和SFR观测结果，表明恒星形成随时间的变化可以解释CMZ的低恒星形成效率。