LOFAR 150-MHz observations of the Bo\"otes field: Catalogue and Source Counts

TL;DR

This paper presents a deep, high-resolution LOFAR radio survey of the Bo"otes field, cataloging over 6,200 sources and analyzing source counts down to very low flux densities, demonstrating the effectiveness of advanced calibration techniques.

Contribution

First wide-area, deep LOFAR 150-MHz survey of the Bo"otes field with high resolution and full direction-dependent calibration, producing a comprehensive source catalogue and detailed source counts.

Findings

Cataloged 6276 sources over 19 deg$^2$ area.

Achieved flux density sensitivity down to 120-150 μJy beam$^{-1}$.

Observed flattening in source counts below 10 mJy, indicating galaxy population changes.

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.