科研之友
微信
新浪微博
Facebook
分享链接
摘要
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 similar to 12 h we obtain a high-resolution (26 '' x 22 '') image of similar to 11.3 square degrees, fully covering the Bootes field region and beyond. The image has a central noise level of similar to 1.0 mJy beam(-1), which rises to 2.0-2.5 mJy beam(-1) at the field edge, placing it amongst the deepest similar to 150 MHz surveys to date. The catalog of 598 extracted sources is estimated to be similar to 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 less than or similar 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 K-S-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.
- 出版日期2011-11
