The Magnetic Field of the Irregular Galaxy NGC 4214
  We examine the magnetic field in NGC 4214, a nearby irregular galaxy, using
multi-wavelength radio continuum polarization data from the Very Large Array.
We find that the global radio continuum spectrum shows signs that free-free
absorption and/or synchrotron losses may be important. The 3cm radio continuum
morphology is similar to that of the Halpha, while the 20cm emission is more
diffuse. We estimate that 50% of the radio continuum emission in the center of
the galaxy is thermal. Our estimate of the magnetic field strength is $30\pm
9.5$ \uG\ in the center and $10\pm3$ \uG\ at the edges. We find that the hot
gas, magnetic, and the gravitational pressures are all the same order of
magnitude. Inside the central star forming regions, we find that the thermal
and turbulent pressures of the HII regions dominate the pressure balance. We do
not detect any significant polarization on size scales greater than 200 pc. We
place an upper limit of 8 \uG\ on the uniform field strength in this galaxy. We
suggest that the diffuse synchrotron region, seen to the north of the main body
of emission at 20cm, is elongated due to a uniform magnetic field with a
maximum field strength of 7.6 \uG. We find that, while the shear in NGC 4214 is
comparable to that of the Milky Way, the supernova rate is half that of the
Milky Way and suggest that the star formation episode in NGC 4214 needs
additional time to build up enough turbulence to drive an $\alpha-\omega$
dynamo.
