Deep Low-Frequency Radio Observations of the NOAO Bootes Field: I. Data
  Reduction and Catalog Construction
  In this article we present deep, high-resolution radio interferometric
observations at 153 MHz to complement the extensively studied NOAO Bootes
field. We provide a description of the observations, data reduction and source
catalog construction. From our single pointing GMRT observation of ~12 hours we
obtain a high-resolution (26" x 22") image of ~11.3 square degrees, fully
covering the Bootes field region and beyond. The image has a central noise
level of ~1.0 mJy/beam, which rises to 2.0-2.5 mJy/beam at the field edge,
placing it amongst the deepest ~150 MHz surveys to date. The catalog of 598
extracted sources is estimated to be ~92 percent complete for >10 mJy sources,
while the estimated contamination with false detections is <1 percent. The low
RMS position uncertainty of 1.24" facilitates accurate matching against
catalogs at optical, infrared and other wavelengths. Differential source counts
are determined down to <~10 mJy. There is no evidence for flattening of the
counts towards lower flux densities as observed in deep radio surveys at higher
frequencies, suggesting that our catalog is dominated by the classical
radio-loud AGN population that explains the counts at higher flux densities.
Combination with available deep 1.4 GHz observations yields an accurate
determination of spectral indices for 417 sources down to the lowest 153 MHz
flux densities, of which 16 have ultra-steep spectra with spectral indices
below -1.3. We confirm that flattening of the median spectral index towards low
flux densities also occurs at this frequency. The detection fraction of the
radio sources in NIR Ks-band is found to drop with radio spectral index, which
is in agreement with the known correlation between spectral index and redshift
for brighter radio sources.
