Spatially-resolved Stellar Population Properties of the M 51-NGC 5195
  System from Multi-wavelength Photometric Data
  Using multi-band photometric images of M 51 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 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 M 51, 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 M 51 into NGC 5195, the stellar population
properties of NGC 5195 are quite featureless. NGC 5195 is much older than M 51,
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.
