标题： 利用多波段方法研究早期类型星系的演化。 II. 使用Swift-UVOT的11个星系的紫外结构 显示英文标题

标题： Investigating early-type galaxy evolution with a multiwavelength approach. II. The UV structure of 11 galaxies with Swift-UVOT

摘要： 广域红外巡天探测器（GALEX）探测到大量表现出远紫外亮结构的早期星系。 这些特征表明近期恒星形成事件的发生。 我们旨在理解它们的演化路径及导致其紫外亮结构的机制。 我们采用多波段方法研究了11个早期星系样本，这些星系因其核区接近被动演化的阶段而被选中。 本文是系列文章中的第二篇，重点比较了由Swift-UVOT探测到的紫外特征（追踪近期恒星形成）与星系光学结构映射的老年恒星群体。 我们进行了它们的紫外表面光度测量，并使用了来自其他来源的BVRI测光数据。 我们的积分亮度已与文献中的对应值进行了分析和比较。 我们用单一的塞尔西斯定律表征了总体星系结构，该结构最适合拟合紫外和光学亮度轮廓。 NGC 1366、NGC 1426、NGC 3818、NGC 3962 和 NGC 7192 显示出无特征的亮度轮廓。 排除具有明显边缘盘的 NGC 1366（n~1-2）和 NGC 3818 后，其余三个星系在光学中具有 n~3-4 的塞尔西斯指数，在紫外中具有较低的指数。 UV 图像和亮度轮廓显示 NGC 1415、NGC 1533、NGC 1543、NGC 2685、NGC 2974 和 IC 2006 中存在明亮的环状/臂状结构。 这些环状/臂状结构在不同星系间有所不同。 这些星系的 UV 轮廓塞尔西斯指数在 S0 型和 E 型星系中范围为 n=1.5-3。 在我们的样本中，光学塞尔西斯指数通常大于紫外指数。 (M2-V) 色彩轮廓在环状/臂状结构中相对于星系主体更蓝。 与光学相比，UV 波段中更低的塞尔西斯指数表明存在盘状结构，这表明在这些早期星系的近期演化阶段中，耗散作用不能被忽略。 显示英文摘要

摘要： GALEX detected a significant fraction of early-type galaxies showing Far-UV bright structures. These features suggest the occurrence of recent star formation episodes. We aim at understanding their evolutionary path[s] and the mechanisms at the origin of their UV-bright structures. We investigate with a multi-lambda approach 11 early-types selected because of their nearly passive stage of evolution in the nuclear region. The paper, second of a series, focuses on the comparison between UV features detected by Swift-UVOT, tracing recent star formation, and the galaxy optical structure mapping older stellar populations. We performed their UV surface photometry and used BVRI photometry from other sources. Our integrated magnitudes have been analyzed and compared with corresponding values in the literature. We characterize the overall galaxy structure best fitting the UV and optical luminosity profiles using a single Sersic law. NGC 1366, NGC 1426, NGC 3818, NGC 3962 and NGC 7192 show featureless luminosity profiles. Excluding NGC 1366 which has a clear edge-on disk , n~1-2, and NGC 3818, the remaining three have Sersic's indices n~3-4 in optical and a lower index in the UV. Bright ring/arm-like structures are revealed by UV images and luminosity profiles of NGC 1415, NGC 1533, NGC 1543, NGC 2685, NGC 2974 and IC 2006. The ring/arm-like structures are different from galaxy to galaxy. Sersic indices of UV profiles for those galaxies are in the range n=1.5-3 both in S0s and in Es. In our sample optical Sersic indices are usually larger than the UV ones. (M2-V) color profiles are bluer in ring/arm-like structures with respect to the galaxy body. The lower values of Sersic's indices in the UV bands with respect to optical ones, suggesting the presence of a disk, point out that the role of the dissipation cannot be neglected in recent evolutionary phases of these early-type galaxies.