标题： 动态热星系的化学演化 显示英文标题

标题： The chemical evolution of dynamically hot galaxies

摘要： 我们研究了M32的化学性质，M31和银河系的核球，以及矮椭球星系NGC 205、NGC 185、半人马座和宝瓶座，使用了它们行星状星云的先前发表的氧丰度。我们的主要结果是，所有这些星系的平均恒星氧丰度与它们的平均速度弥散度非常吻合。这意味着II型超新星的能量输入与引力势能之间的平衡控制着在核球、椭圆星系和矮椭球星系中的化学演化进程。看来，一旦超新星注入了足够的能量以产生星系风，化学演化就会停止。所有星系遵循氧丰度与亮度之间的一个单一关系，但矮椭球星系的[O/Fe]比值系统性地高于其他星系。因此，动态热星系不需要共享相同的恒星形成历史，也不需要共享相同的化学演化过程，尽管当形成相似的恒星质量时，它们达到了类似的平均恒星氧丰度。氧丰度支持了先前的指示，即在较高亮度的椭圆星系和核球中的恒星是在较短的时间尺度上形成的，而它们在较暗系统中的对应恒星则不然。我们使用行星状星云的平均氧丰度和M32以及M31和银河系核球中恒星的最佳年龄估计值，校准了动态热星系的Mg$_2$指数作为观测年龄和氧丰度的函数。 显示英文摘要

摘要： We investigate the chemical properties of M32, the bulges of M31 and the Milky Way, and the dwarf spheroidal galaxies NGC 205, NGC 185, Sagittarius, and Fornax using previously published oxygen abundances for their planetary nebulae. Our principal result is that the mean stellar oxygen abundances for all of these galaxies correlate very well with their mean velocity dispersions. This implies that the balance between energy input from type II supernovae and the gravitational potential energy controls how far chemical evolution proceeds in bulges, ellipticals, and dwarf spheroidals. It appears that chemical evolution ceases once supernovae have injected sufficient energy that a galactic wind develops. All of the galaxies follow a single relation between oxygen abundance and luminosity, but the dwarf spheroidals have systematically higher [O/Fe] ratios than the other galaxies. Consequently, dynamically hot galaxies do not share a common star formation history nor need they share a common chemical evolution, despite attaining similar mean stellar oxygen abundances when forming similar stellar masses. The oxygen abundances support previous indications that the stars in higher luminosity ellipticals and bulges were formed on a shorter time scale than their counterparts in less luminous systems. We calibrate the Mg$_2$ index for dynamically hot galaxies as a function of observed age and oxygen abundance using the mean oxygen abundances from the planetary nebulae and the best age estimates available for the stars in M32 and the bulges of M31 and the Milky Way.