arXiv 0810.49632008-10astro-ph

反馈对盘星系标度关系的影响

The Impact of Feedback on Disk Galaxy Scaling Relations

Aaron A. Dutton, Frank C. van den Bosch

备注：: 27 pages, 16 figures, accepted to MNRAS, two new figures
发表信息：: MNRAS 396 (2009) 141-164
DOI：: 10.1111/j.1365-2966.2009.14742.x

摘要：

我们使用一个盘状星系演化模型来研究质量外流（也称为星系演化）的影响。反馈）的盘星系的标度关系。我们的模型遵循的吸积，冷却，恒星形成和喷射的重子质量内增长的暗物质晕，宇宙学动机的特定角动量分布。没有反馈的模型产生的圆盘太小，旋转太快。反馈减少了星系的重子质量，导致更大的圆盘具有更低的旋转速度。有反馈的模型可以再现旋转速度、恒星质量和盘大小之间标度关系的零点，但仅在没有绝热收缩的情况下。我们的反馈机制在排出质量方面是最有效的，但我们成功的模型需要25%的SN能量或100%的SN动量来驱动外流。这种高效率是否现实，还有待观察。我们的能量和动量驱动的风模型导致不同的斜率的各种标度关系，如大小恒星质量，恒星质量晕质量，和金属丰度恒星质量。在恒星质量低于10^{10.5} Msun时，观测结果支持能量驱动风，但在高质量时，动量驱动风模型。在我们的模型中，重子的比角动量与晕的比角动量之比（j_gal/m_gal）并不一致。然而，这是盘状星系形成模型的标准假设。反馈优先蒸发低角动量物质，因为恒星形成在较小的星系半径更有效。这导致（j_gal/m_gal）随着晕质量的减小而增大。这种效应有助于解决矮星系观测到的高自旋参数与LCDM预测的低自旋参数之间的差异。[删节]

英文摘要：

We use a disk galaxy evolution model to investigate the impact of mass outflows (a.k.a. feedback) on disk galaxy scaling relations. Our model follows the accretion, cooling, star formation and ejection of baryonic mass inside growing dark matter haloes, with cosmologically motivated specific angular momentum distributions. Models without feedback produce disks that are too small and rotate too fast. Feedback reduces the baryonic masses of galaxies, resulting in larger disks with lower rotation velocities. Models with feedback can reproduce the zero points of the scaling relations between rotation velocity, stellar mass and disk size, but only in the absence of adiabatic contraction. Our feedback mechanism is maximally efficient in expelling mass, but our successful models require 25% of the SN energy, or 100% of the SN momentum, to drive the outflows. It remains to be seen whether such high efficiencies are realistic or not. Our energy and momentum driven wind models result in different slopes of various scaling relations, such as size - stellar mass, stellar mass - halo mass, and metallicity - stellar mass. Observations favor the energy driven wind at stellar masses below Mstar = 10^{10.5} Msun, but the momentum driven wind model at high masses. The ratio between the specific angular momentum of the baryons to that of the halo, (j_gal/m_gal), is not unity in our models. Yet this is the standard assumption in models of disk galaxy formation. Feedback preferentially ejects low angular momentum material because star formation is more efficient at smaller galactic radii. This results in (j_gal/m_gal) increasing with decreasing halo mass. This effect helps to resolve the discrepancy between the high spin parameters observed for dwarf galaxies with the low spin parameters predicted from LCDM. [Abridged]

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