J,H, and K ^ { \prime } images obtained with the Canada-France-Hawaii Telescope adaptive optics system are used to investigate the star-forming histories of the central regions of the Sc galaxies NGC 247 and NGC 2403 .
The brightest resolved red stars within 15 arcsec of the nucleus of each galaxy are red supergiants ( RSGs ) , indicating that the central few hundred parsecs of these galaxies experienced star formation within the last \sim 0.1 Gyr .
While there are indications of galaxy-to-galaxy differences in the recent ( t \leq 0.1 Gyr ) star-forming histories , a comparison of the K luminosity functions of stars near the centers of NGC 2403 and M33 indicate that , when averaged over Gyr time scales , the star-forming histories of the inner disks of these galaxies have been remarkably similar .
This is consistent with suggestions that the long-term evolution of disks is defined by local characteristics such as mass density .
It is demonstrated that NGC 247 and NGC 2403 , like M33 , harbour nuclear star clusters with stellar contents that differ from the surrounding central light concentrations , which in turn have near-infrared spectral energy distributions that are similar to old stellar systems .
The nucleus of NGC 2403 is significantly bluer than that of the other two galaxies .
If the nuclei of NGC 247 , NGC 2403 , and M33 are subject to similar amounts of extinction then this indicates that NGC 2403 harbours the youngest nuclear star cluster in the sample .
The K - band surface brightnesses near the centers of NGC 247 and NGC 2403 are 1 – 2 mag arcsec ^ { -2 } lower than in M33 .
Finally , it is noted that young or intermediate-age nuclear star clusters are a common occurence in nearby spirals , indicating that nuclear star formation in these objects is either continuous or episodic on time scales of 0.1 - 1 Gyr .
This is consistent with models that have been proposed to explain the properties of the Galactic Center .