标题： 1.65微米（H波段）星系表面光度测量。 VI：正常晚型星系的恒星形成历史 显示英文标题

标题： 1.65mic (H-band) surface photometry of galaxies. VI: The history of star formation in normal late-type galaxies

摘要： 我们收集了大量晚型星系的近红外（H波段）、紫外（2000 Å）和Hα测量数据。 这些数据与光谱演化综合模型一起使用，以研究质量范围m > 2M☉内的初始质量函数（IMF）。 对于螺旋星系（Sa-Sd）、麦哲伦不规则星系（Im）和蓝紧凑矮星系（BCD），我们的测定结果与Salpeter IMF一致，其上限质量截断值M_up = 80M☉。 星系的恒星形成历史以及单位质量的总气体量主要取决于它们的总质量（由H波段亮度追踪），而次级依赖于形态类型。 大质量螺旋星系目前的恒星形成活动比其一生中的平均值小多达100倍，而在低质量星系中则相当于或高于早期时期的水平。 矮星系目前单位质量的气体储量比大质量螺旋星系更大。 将气体转化为恒星的效率以及气体耗尽的时间尺度（10 Gyr）与星系的亮度和/或形态类型无关。 这些证据与星系是同时系统且作为封闭盒子演化的观点一致，即它们遵循一个简单的、普遍的恒星形成定律来形成恒星，其特征时间尺度在大质量螺旋星系中较小（1 Gyr），而在低质量星系中较大（10 Gyr）。 Gavazzi和Scodeggio（1996）得出了类似的结论，用以解释晚型星系的颜色-亮度关系。 讨论了这一解释对宇宙随回溯时间的恒星形成率和单位共动体积气体密度演化的影响。 显示英文摘要

摘要： We have collected a large body of NIR (H band), UV (2000 A) and Halpha measurements of late-type galaxies. These are used, jointly with spectral evolutionary synthesis models, to study the initial mass function (IMF) in the mass range m > 2 Mo. For spirals (Sa-Sd), Magellanic irregulars (Im) and blue compact dwarfs (BCD), our determination is consistent with a Salpeter IMF with an upper mass cutoff M_up = 80 Mo. The history of star formation and the amount of total gas (per unit mass) of galaxies are found to depend primarily on their total masses (as traced by the H band luminosities) and only secondarily on morphological type. The present star formation activity of massive spirals is up to 100 times smaller than that average over their lifetime, while in low mass galaxies it is comparable to or higher than that at earlier epochs. Dwarf galaxies have presently larger gas reservoirs per unit mass than massive spirals. The efficiency in transforming gas into stars and the time scale for gas depletion (10 Gyrs) are independent of the luminosity and/or of the morphological type. These evidences are consistent with the idea that galaxies are coeval systems,that they evolved as closed-boxes forming stars following a simple, universal star formation law whose characteristic time scale is small (1 Gyr) in massive spirals and large (10 Gyr) in low mass galaxies. A similar conclusion was drawn by Gavazzi and Scodeggio (1996) to explain the colour-magnitude relation of late-type galaxies. The consequences of this interpretation on the evolution of the star formation rate and of the gas density per comoving volume of the Universe with look-back time are discussed.