标题： 晚型螺旋星系中恒星演化证据 显示英文标题

标题： Evidence for Secular Evolution in Late-Type Spirals

摘要： 我们将两个近期星系样本中的326个旋涡星系的深度光学和红外测光数据结合起来，并报告晚型旋涡星系的面亮度剖面最好由两个指数拟合。此外，核球和盘尺度长度的比例取值范围受限，并且与哈勃类型无关。这表明晚型旋涡星系具有无标度的哈勃序列。仔细的数值模拟确保我们的结果不受seeing或分辨率效应的影响。这些星系中有许多显示出旋臂结构延伸到星系中心区域，并有一个之前未被检测到的小棒，以及内盘和核球之间颜色缓慢变化。我们提出了恒态动力学演化，并在此背景下解释盘中心区域的性质，即通过角动量转移和粘性传输导致的气体流入。在这个场景中，晚型旋涡星系的形态并非在诞生时就被确定，而是演化的结果。 显示英文摘要

摘要： We combine deep optical and IR photometry for 326 spiral galaxies from two recent galaxy samples and report that the surface brightness profiles of late-type spirals are best fit by two exponentials. Moreover, the ratio of bulge and disk scale lengths takes on a restricted range of values and is uncorrelated with Hubble type. This suggests a scale-free Hubble sequence for late-type spirals. Careful numerical simulations ensure that our results are not affected by seeing or resolution effects. Many of these galaxies show spiral structure continuing into the central regions with a previously undetected small bar and slowly changing colors between the inner disk and the bulge. We invoke secular dynamical evolution and interpret the nature of disk central regions in the context of gas inflow via angular-momentum transfer and viscous transport. In this scenario, galaxy morphologies in late-type spirals are not imprinted at birth but are the result of evolution.