Using multi-band photometric images of M51 and its companion NGC 5195 from ultraviolet to optical and infrared, we investigate spatially resolved stellar population properties of this interacting system with stellar population synthesis models. The observed infrared excess (IRX) is used to constrain dust extinction. Stellar mass is also inferred from the model fitting. By fitting observed spectral energy distributions (SEDs) with synthetical ones, we derive two-dimensional distributions of stellar age, metallicity, dust extinction and stellar mass. In M51, two grand-designed spiral arms extending from the bulge show young age, rich metallicity and abundant dust. The inter-arm regions are filled with older, metal-poorer and less dusty stellar populations. Except for the spiral arm extending from M51 into NGC 5195, the stellar population properties of NGC 5195 are quite featureless. NGC 5195 is much older than M51, and its core is very dusty with A_V up to 1.67 mag and dense in stellar mass surface density. The close encounters might drive the dust in the spiral arm of M51 into the center of NGC 5195.

我们使用 M51 及其伴星 NGC 5195 从紫外到光学和红外的多波段光度图像，利用星群合成模型研究了这个相互作用系统的空间分辨星群特性。观察到的红外过量 (IRX) 用于限制尘埃消光。恒星质量也可以从模型拟合中推断出来。通过将观测到的光谱能量分布 (SED) 与合成光谱能量分布 (SED) 拟合，我们得出了恒星年龄、金属丰度、尘埃消光和恒星质量的二维分布。在 M51 中，两个从隆起处延伸出来的宏伟设计的旋臂显示出年轻、丰富的金属丰度和丰富的尘埃。臂间区域充满了较老、金属较少且尘埃较少的恒星群。除了从 M51 延伸到 NGC 5195 的旋臂外，NGC 5195 的星族属性相当无特色。NGC 5195 比 M51 年代久远，其核心尘土飞扬A _V 高达 1.67 等，恒星质量表面密度致密。近距离接触可能会将 M51 旋臂中的尘埃推向 NGC 5195 的中心。