THE SPECIFIC STAR FORMATION RATE AND STELLAR MASS FRACTION OF LOW-MASS CENTRAL GALAXIES IN COSMOLOGICAL SIMULATIONS
THE SPECIFIC STAR FORMATION RATE AND STELLAR MASS FRACTION OF LOW-MASS CENTRAL GALAXIES IN COSMOLOGICAL SIMULATIONS
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DOI：
10.1088/0004-637x/736/2/134
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发表时间：
2011-03
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影响因子：
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通讯作者：
V. Avila-Reese;P. Colín;A. Gonz'alez-Samaniego;O. Valenzuela;C. Firmani;H. Vel'azquez;D. Ceverino
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作者：
V. Avila-Reese;P. Colín;A. Gonz'alez-Samaniego;O. Valenzuela;C. Firmani;H. Vel'azquez;D. Ceverino
通过对星系在Λ冷暗物质（ΛCDM）场景下的宇宙学n -体+流体动力学模拟，我们探索了不同红移（0≤z≤1.5）下亚m *场星系的特定恒星形成速率（SSFR = SFR/Ms， Ms为恒星质量）和恒星质量分数（Fs≡Ms/Mh， Mh为晕质量）。不同的低质量晕（在z = 0处的2.5 > Mh/1010 M☉> 50）被选择用于高分辨率的重新模拟。采用流体力学自适应细化树（ART）代码，探讨了子网格参数的一些变化。大多数模拟星系，特别是那些具有最高分辨率的星系，都有显著的盘状成分，它们的结构和动力学性质与亚m *场星系的观测结果基本一致。然而，ssfr比在z < 0.3（在低质量时，大多数观测到的星系实际上是蓝色/恒星形成）的几个观测结果的平均值小5-10倍。即使在z ~ 1-1.5，这种不一致性似乎仍然存在，尽管它不那么剧烈。半经验推断表明，模拟星系的f随Mh的增加而增加。然而，在z≈0处的Fs值在模拟中比在推论中大~ 5-10倍；这些差异在z ~ 1-1.5时可能增加到更大的因子。这里报告的不一致意味着模拟的低质量星系（在z = 0处0.2≤Ms/109 M☉≤30）聚集恒星质量的时间比观测显示的要早得多。我们的研究结果证实了ΛCDM-based模型对孤立低质量星系的盘状星系形成和演化的预测，并强调了我们对天体物理学的理解和实现在模拟和模型中仍然缺乏重要的成分。
By means of cosmological N-body + hydrodynamics simulations of galaxies in the context of the Λ cold dark matter (ΛCDM) scenario we explore the specific star formation rates (SSFR = SFR/Ms, Ms is the stellar mass) and stellar mass fractions (Fs ≡ Ms/Mh, Mh is the halo mass) for sub-M* field galaxies at different redshifts (0 ≲ z ≲ 1.5). Distinct low-mass halos (2.5 ≲ Mh/1010 M☉ ≲ 50 at z = 0) were selected for the high-resolution re-simulations. The Hydrodynamics Adaptive Refinement Tree (ART) code was used and some variations of the sub-grid parameters were explored. Most simulated galaxies, specially those with the highest resolutions, have significant disk components and their structural and dynamical properties are in reasonable agreement with observations of sub-M* field galaxies. However, the SSFRs are 5–10 times smaller than the averages of several (compiled and homogenized here) observational determinations for field blue/star-forming galaxies at z < 0.3 (at low masses, most observed field galaxies are actually blue/star forming). This inconsistency seems to remain even at z ∼ 1–1.5, although it is less drastic. The Fs of simulated galaxies increases with Mh as semi-empirical inferences show. However, the values of Fs at z ≈ 0 are ∼5–10 times larger in the simulations than in the inferences; these differences increases probably to larger factors at z ∼ 1–1.5. The inconsistencies reported here imply that simulated low-mass galaxies (0.2 ≲ Ms/109 M☉ ≲ 30 at z = 0) assembled their stellar masses much earlier than observations suggest. Our results confirm the predictions found by means of ΛCDM-based models of disk galaxy formation and evolution for isolated low-mass galaxies, and highlight that our understanding and implementation of astrophysics into simulations and models are still lacking vital ingredients.