MaGICC baryon cycle: the enrichment history of simulated disc galaxies
MaGICC baryon cycle: the enrichment history of simulated disc galaxies
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DOI：
10.1093/mnras/stu1406
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发表时间：
2013-06
影响因子：
4.8
通讯作者：
C. Brook;G. Stinson;Bradley K Gibson;Bradley K Gibson;S. Shen;A. Macciò;A. Obreja;J. Wadsley;Thomas P. Quinn
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文献类型：
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作者：
C. Brook;G. Stinson;Bradley K Gibson;Bradley K Gibson;S. Shen;A. Macciò;A. Obreja;J. Wadsley;Thomas P. Quinn
利用MaGICC（在宇宙学背景下制造星系）项目的宇宙学星系形成模拟，跨越恒星质量从~ 107到3 × 1010 M⊙，我们追踪了从病毒半径到最终参与恒星形成过程的落入气体的重子周期。重点放在化学富集在其通过日冕和环星系介质的时间历史上。我们推导出气体穿过维里半径和被吸积到恒星形成区域之间的时间分布（这允许在日冕内混合），以及气体被吸积到恒星形成区域然后最终形成恒星之间的时间分布（这允许在圆盘内混合）。大量的恒星是由气体形成的，这些气体在第一次吸积到恒星形成区域后，通过热晕循环回来。进入高质量星系的气体在进入中央祖星系的维里半径之前，在低质量原星系中被预先富集，即使在高红移（z ~ 5）时，也只有少量的原始气体被吸积。进入维里半径后，在气体吸积到恒星形成区域之前，会发生显著的进一步富集，进入恒星形成区域的气体在Z = 0之前超过0.1 Z⊙。因此，与光环气体的混合对于确定气体被吸积到盘上的金属丰度至关重要。相比之下，质量最低的模拟星系（Mvir ~ 2 × 1010 M⊙，其中M - ~ 107 M⊙）在其整个历史中通过维里半径吸积原始气体并吸积到盘上。就像对所谓的“g矮星问题”的经典解析解的情况一样，低金属丰度恒星的过量产生通过吸积到盘上的时间和随后参与恒星形成之间的相互作用得到改善，即由于恒星形成的效率低下。最后，给出了恒星形成区域的气体流出率/金属去除率与星系质量的函数关系。
Using cosmological galaxy formation simulations from the MaGICC (Making Galaxies in a Cosmological Context) project, spanning stellar mass from ∼107 to 3 × 1010 M⊙, we trace the baryonic cycle of infalling gas from the virial radius through to its eventual participation in the star formation process. An emphasis is placed upon the temporal history of chemical enrichment during its passage through the corona and circumgalactic medium. We derive the distributions of time between gas crossing the virial radius and being accreted to the star-forming region (which allows for mixing within the corona), as well as the time between gas being accreted to the star-forming region and then ultimately forming stars (which allows for mixing within the disc). Significant numbers of stars are formed from gas that cycles back through the hot halo after first accreting to the star-forming region. Gas entering high-mass galaxies is pre-enriched in low-mass proto-galaxies prior to entering the virial radius of the central progenitor, with only small amounts of primordial gas accreted, even at high redshift (z ∼ 5). After entering the virial radius, significant further enrichment occurs prior to the accretion of the gas to the star-forming region, with gas that is feeding the star-forming region surpassing 0.1 Z⊙ by z = 0. Mixing with halo gas, itself enriched via galactic fountains, is thus crucial in determining the metallicity at which gas is accreted to the disc. The lowest mass simulated galaxy (Mvir ∼ 2 × 1010 M⊙, with M⋆ ∼ 107 M⊙), by contrast, accretes primordial gas through the virial radius and on to the disc, throughout its history. Much like the case for classical analytical solutions to the so-called ‘G-dwarf problem’, overproduction of low-metallicity stars is ameliorated by the interplay between the time of accretion on to the disc and the subsequent involvement in star formation – i.e. due to the inefficiency of star formation. Finally, gas outflow/metal removal rates from star-forming regions as a function of galactic mass are presented.