The VLA-COSMOS Survey: V. 324 MHz continuum observations
  We present 90 cm VLA imaging of the COSMOS field, comprising a circular area
of 3.14 square degrees at 8.0"x6.0" angular resolution with an average rms of
0.5 mJy/beam. The extracted catalog contains 182 sources (down to 5.5sigma), 30
of which are multi-component sources. Using Monte Carlo artificial source
simulations we derive the completeness of the catalog, and we show that our 90
cm source counts agree very well with those from previous studies. Using X-ray,
NUV-NIR and radio COSMOS data to investigate the population mix of our 90 cm
radio sample, we find that our sample is dominated by active galactic nuclei
(AGN). The average 90-20 cm spectral index (S_nu~nu**alpha, where S_nu is the
flux density at frequency nu, and alpha the spectral index) of our 90 cm
selected sources is -0.70, with an interquartile range of -0.90 to -0.53. Only
a few ultra-steep-spectrum sources are present in our sample, consistent with
results in the literature for similar fields. Our data do not show clear
steepening of the spectral index with redshift. Nevertheless, our sample
suggests that sources with spectral indices steeper than -1 all lie at z>1, in
agreement with the idea that ultra-steep-spectrum radio sources may trace
intermediate-redshift galaxies (z>1).
