Spatially-resolved stellar population properties of the M51–NGC 5195 system from multi-wavelength photometric data

Abstract

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 AV 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.