We obtained Hubble Space Telescope /Wide Field Camera 3 imaging of a sample of ten of the nearest and brightest nuclear clusters residing in late-type spiral galaxies , in seven bands that span the near-ultraviolet to the near-infrared .
Structural properties of the clusters were measured by fitting two-dimensional surface brightness profiles to the images using GALFIT .
The clusters exhibit a wide range of structural properties , with F814W absolute magnitudes that range from -11.2 mag to -15.1 mag and F814W effective radii that range from 1.4 to 8.3 pc .
For six of the ten clusters in our sample , we find changes in the effective radius with wavelength , suggesting radially varying stellar populations .
In four of the objects , the effective radius increases with wavelength , indicating the presence of a younger population which is more concentrated than the bulk of the stars in the cluster .
However , we find a general decrease in effective radius with wavelength in two of the objects in our sample , which may indicate extended , circumnuclear star formation .
We also find a general trend of increasing roundness of the clusters at longer wavelengths , as well as a correlation between the axis ratios of the NCs and their host galaxies .
These observations indicate that blue disks aligned with the host galaxy plane are a common feature of nuclear clusters in late-type galaxies , but are difficult to detect in galaxies that are close to face-on .
In color-color diagrams spanning the near-UV through the near-IR , most of the clusters lie far from single-burst evolutionary tracks , showing evidence for multi-age populations .
Most of the clusters have integrated colors consistent with a mix of an old population ( > 1 Gyr ) and a young population ( \sim 100 – 300 Myr ) .
The wide wavelength coverage of our data provides a sensitivity to populations with a mix of ages that would not be possible to achieve with imaging in optical bands only .
The surface brightness profiles presented in this work will be used for future stellar population modeling and dynamical studies of the clusters .