碰撞环星系的星盘I。新的多波段图像，径向强度和颜色剖面，以及与N体模拟的对抗
Stellar disks of Collisional Ring Galaxies I. New multiband images, Radial intensity and color profiles, and confrontation with N-body simulations
摘要：
我们提供了Appleton & Marston（1997）样品中15个候选环星系的光学（BVRI和Halpha）和近红外波段（JHK）的新的多波段成像数据。我们使用这些数据来获得彩色合成图像，环星系和它的同伴的全球星等和颜色，以及强度和颜色的径向轮廓。我们发现，只有9个观察到的星系有多带形态预期的经典碰撞场景的环形成，表明高度污染的环星系样本的星系没有一个明确的环形态。径向强度分布，通过掩蔽偏心核，峰值在环的位置，与轮廓中的连续带比在H α线宽。这些图像以及径向强度和颜色轮廓清楚地表明了恒星形成环外部的碰撞前恒星盘的存在，它通常比环内部的盘更蓝。恒星盘似乎保持了它的大小，与质量相当的正常螺旋星系相比，环外的盘具有较短的指数尺度长度。在我们的星系样本中，发现环优先位于恒星盘的一半左右。这种偏好最可能的原因是当环靠近中心时（它们会与共振环混淆）对检测环的偏见，并且在圆盘的边缘，气体表面密度可能低于恒星形成所需的临界密度。根据Gerber等人（1996年）的N体模拟，大多数观察到的特征都指向相对较近的碰撞（<8千万年前）。
英文摘要：
We present new multi-band imaging data in the optical (BVRI and Halpha) and near infrared bands (JHK) of 15 candidate ring galaxies from the sample of Appleton & Marston (1997). We use these data to obtain color composite images, global magnitudes and colors of both the ring galaxy and its companion(s), and radial profiles of intensity and colors. We find that only nine of the observed galaxies have multi-band morphologies expected for the classical collisional scenario of ring formation, indicating the high degree of contamination of the ring galaxy sample by galaxies without a clear ring morphology. The radial intensity profiles, obtained by masking the off-centered nucleus, peak at the position of the ring, with the profiles in the continuum bands broader than that in the Halpha line. The images as well as the radial intensity and color profiles clearly demonstrate the existence of the pre-collisional stellar disk outside the star-forming ring, which is in general bluer than the disk internal to the ring. The stellar disk seems to have retained its size, with the disk outside the ring having a shorter exponential scale length as compared to the values expected in normal spiral galaxies of comparable masses. The rings in our sample of galaxies are found to be located preferentially at around half-way through the stellar disk. The most likely reason for this preference is bias against detecting rings when they are close to the center (they would be confused with the resonant rings), and at the edge of the disk the gas surface density may be below the critical density required for star formation. Most of the observed characteristics point to relatively recent collisions (<80 Myr ago) according to the N-body simulations of Gerber et al. (1996).
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