The MeerKAT 1.3 GHz survey of the Large Magellanic Cloud: Point Source Catalogue

Abstract

We present a point source catalogue of the Large Magellanic Cloud (LMC) using observations from the MeerKAT radio telescope across a broad frequency band centred at 1295 MHz (L-band) with 12 sub-bands and an angular resolution of 8 arcsec x 8 arcsec. We investigate the source flux density distribution and spectral indices and compare these results with previous radio catalogues, such as surveys conducted with the Australian Square Kilometre Array Pathfinder (ASKAP) at 888 MHz. This new MeerKAT survey reaches a lower average noise level of 11 microJy beam^-1, compared with the previous ASKAP level of 58 microJy beam^-1. The higher sensitivity and resolution enable the detection of a significantly larger number of faint sources. The catalogue contains 339,128 point sources, representing a substantial increase compared with the 54,612 sources detected in the ASKAP survey. This catalogue provides improved insight into the source population distribution, spectral properties, positional accuracy, and the overall improvement in source recovery and survey depth in the LMC region.

Figures (7)

• Figure 1: Stitched image of the LMC created from six overlapping $5^\circ \times 5^\circ$ fields, created as described in text and CottonLMC. The image is linearly scaled.
• Figure 2: The plot of the relationship between local RMS noise levels and the peak flux density of sources from the initial catalogue (left) and the final catalogue (right). The distribution is generally smooth, with noticeable density excesses in regions where RMS exceeds 35 $\mu$Jy beam$^{-1}$ (marked by a vertical red line) and where RMS is below 5 $\mu$Jy beam$^{-1}$ (marked by a vertical magenta line). Detections below the applied signal-to-noise threshold (blue line) were removed from the final catalogue.
• Figure 3: Source distribution maps of the MeerKAT LMC field. The green regions in the left figure correspond to sources located at the edge of the field, and the yellow regions in the left represent regions with an average RMS exceeding 35 $\mu$Jy beam$^{-1}$. The entire point source density of sources detected using Aegean are shown in the right image. Scale bars are shown in the bottom left corners of each image, and the images are linearly scaled.
• Figure 4: Distribution of spectral indices across 12 different frequencies from MeerKAT. Top Left: Scatter plot showing the distribution of spectral indices per integrated flux density. The colours represent the number of channels used in the spectral index fit. Top Right: Stacked histogram showing the point source spectral index distribution. The colours represent the number of channels used in the spectral index fit. Bottom Left: The distribution of spectral indices per integrated flux densities for 14,065 sources. This group of sources were restricted to those with only 12 frequency-flux density measurements as well as the flux density $>$0.5 mJy, spectral index error $\Delta \alpha < 0.2$, and $\chi_\nu^2 < 1$. The colour bar represents the spectral index fit error. Bottom Right: The distribution of spectral indices for this sample of 14,065 sources. In all four figures, light colours represent small numbers, and dark colours represent high.
• Figure 5: Left: Positional difference between the LMC MeerKAT and ASKAP catalogue for 39,391 sources in common. The mean offsets are $\Delta$RA=$0.8$ arcsec (STDEV=1.09) and mean $\Delta$DEC=$0.1$ arcsec (STDEV=0.96). Right: The positional differences between MilliQuas and MeerKAT catalogues were analysed for 423 sources identified through cross-matching both catalogues with a maximum separation threshold of 4 arcsec, with mean $\Delta$RA=--0.03 arcsec (STDEV=0.5) and mean $\Delta$DEC=--0.04 arcsec (STDEV=0.4).