We present a multi-wavelength study of embedded massive clusters in the nearby ( 3.9 Mpc ) starburst galaxy NGC 4449 in an effort to uncover the earliest phases of massive cluster evolution .
By combining high resolution imaging from the radio to the ultraviolet , we reveal these clusters in the process of emerging from their gaseous and dusty birth cocoons .
We use Very Large Array ( VLA ) observations at centimeter wavelengths to identify young clusters surrounded by ultra-dense H II regions , detectable via their production of thermal free-free radio continuum .
Ultraviolet , optical and infrared observations are obtained from the Hubble and Spitzer Space Telescope archives for comparison .
We detect 39 compact radio sources towards NGC 4449 at 3.6 cm using the highest resolution ( 1 \farcs 3 ) and sensitivity ( RMS \sim 12 \mu Jy ) VLA image of the galaxy to date .
We reliably identify 13 thermal radio sources and their physical properties are derived using both nebular emission from the H II regions and SED fitting to the stellar continuum .
These radio detected clusters have ages \lesssim 5 Myr and stellar masses of order 10 ^ { 4 } M _ { \odot } .
The measured extinctions are quite low : 12 of the 13 thermal radio sources have A _ { V } \lesssim 1.5 , while the most obscured source has A _ { V } \approx 4.3 .
By combining results from the nebular and stellar emission , we find an I -band excess that is anti-correlated with cluster age and an apparent mass-age correlation .
Additionally , we find evidence that local processes such as supernovae and stellar winds are likely playing an important role in triggering the current bursts of star formation within NGC 4449 .