Abstract
We present the first wide area (19 deg$^2$), deep ($\approx120-150$ {\mu}Jy beam$^{-1}$), high resolution ($5.6 \times 7.4$ arcsec) LOFAR High Band Antenna image of the Bo\"otes field made at 130-169 MHz. This image is at least an order of magnitude deeper and 3-5 times higher in angular resolution than previously achieved for this field at low frequencies. The observations and data reduction, which includes full direction-dependent calibration, are described here. We present a radio source catalogue containing 6276 sources detected over an area of $19$\,deg$^2$, with a peak flux density threshold of $5\sigma$. As the first thorough test of the facet calibration strategy, introduced by van Weeren et al., we investigate the flux and positional accuracy of the catalogue. We present differential source counts that reach an order of magnitude deeper in flux density than previously achieved at these low frequencies, and show flattening at 150 MHz flux densities below 10 mJy associated with the rise of the low flux density star-forming galaxies and radio-quiet AGN.
Highlights
The Low Frequency Array (LOFAR) is a new generation radio telescope operating at 10–240 MHz
We present the first wide area (19 deg2), deep (≈120–150 μJy beam−1), high-resolution (5.6 × 7.4 arcsec) LOFAR High Band Antenna image of the Bootes field made at 130–169 MHz
All calibration steps are performed with the BLACKBOARD SELFCAL (BBS) software system (Pandey et al 2009), and other data handling steps were undertaken with the LOFAR Default Pre-Processing Pipeline (DPPP)
Summary
The Low Frequency Array (LOFAR) is a new generation radio telescope operating at 10–240 MHz (van Haarlem et al 2013). To achieve the diverse goals of the LOFAR surveys, which will be carried out over the five years, a tiered approach is being used: Tier-1 covers the largest area at the lowest sensitivity and will include low-band (LBA; 15–65 MHz) and high-band (HBA; 110–180 MHz) observations across the whole 2π steradians of the northern sky with a targeted rms noise of ≈0.1 mJy beam−1 and a resolution of ≈5 arcsec. Provided redshifts for 23 745 galaxies and AGN across 7.7 deg of the Bootes field (Kochanek et al 2012) This rich multiwavelength data set, combined with the new low-frequency radio data presented here, will be important for determining the evolution of black hole accretion over cosmic time. We assume a spectral index of −0.8 unless otherwise stated
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