The SARAO MeerKAT Galactic Plane Survey compact source catalogue

TL;DR

The paper delivers the SMGPS compact-source catalogue from the MeerKAT 1.3 GHz Galactic Plane survey, yielding 510,599 detections above $S/N\geq 5\sigma$ with compactness defined as $<5$ synthesized beams and angular resolution of $8''$. It details a rigorous pipeline using BANE for background estimation and Aegean for source extraction, quantifying completeness ($\geq90\%$ at $\sim0.15$ mJy/beam) and false-positive rates ($\sim0.63\%$), and provides extensive characterisation of source morphology and flux boosting. The work demonstrates valuable science opportunities, including identification of radio-quiet WISE HII region candidates, comparison with CORNISH UC HII regions, and connections to MMB methanol masers, highlighting the catalogue’s depth, sensitivity, and synergy with multi-wavelength surveys. This catalogue enables new population studies of compact radio sources in the Galactic Plane and lays groundwork for forthcoming multi-wavelength analyses and cross-survey investigations.

Abstract

We present a catalogue of compact sources detected in the SARAO MeerKAT 1.3 GHz Galactic Plane Survey (SMGPS). We extract 510599 compact sources, with areas less than five 8" beams, from the survey maps covering the regions $252°< l < 358^°$ and $2°< l < 61°$ at $|b| \leq 1.5^°$, which have an angular resolution of 8" and a sensitivity of $\sim$ 10-30 $μ$Jy beam$^{-1}$. In this paper, we describe the source identification and characterisation methods, present the quality assurance of the catalogue, explore the nature of the catalogue sources, and present initial science highlights. We limit our catalogue to sources with a signal-to-noise ratio $\geq 5$, as the catalogue is $\sim$90 per cent complete, and has a false positive rate of less than 1 per cent at this threshold. The bulk of the catalogue sources are previously unknown to the literature, with the majority of unknown sources at sub-mJy levels. Initial science highlights from the catalogue include the detection of 213 radio quiet WISE HII region candidates, previously undetected in radio continuum studies. We show images that compare the SMGPS compact sources to CORNISH ultracompact HII regions, thus highlighting the sensitivity and unprecedented uv-coverage of the SMGPS, and the potential synergy of the SMGPS with other surveys.

Figures (22)

• Figure 1: An example image of two SMGPS 1.3 GHz moment 0 tiles, centred at $l=309.5\degr~\&~l=312.5\degr$, that have been stitched together.
• Figure 2: Demonstration of BANE's background and noise estimation on a square degree of the SMGPS G342.5 tile. The left panel shows the moment 0 image itself, the top-right panel shows the background, and the lower-right panel the rms. Detected sources are marked as cyan triangles on the moment 0 image and the synthesised beam is shown as a filled ellipse in the lower-left corner of the moment 0 image.
• Figure 3: Survey tiles selected to show the local and global variation in noise across the SMGPS. The G258.5 tile (left) is representative of the low-noise portion of the survey, the G306.5 tile (middle) is representative of parts of the survey with huge noise spikes, artefacts, and sidelobes, and the G333.5 tile (right) is representative of parts of the survey with high rms noise due extended defuse emission. The global rms is highest in the G333.5 tile, followed by the G306.5 tile and is lowest in the G258.5 tile: 83, 56 and 11 µ Jy beam$^{-1}$, respectively.
• Figure 4: Distribution of the rms noise across the survey, determined through the local rms flux density at the position of the individual SMGPS compact source detections. The local rms values range from 7 µ Jy beam$^{-1}$ to 29 mJy beam$^{-1}$.
• Figure 5: Integrated flux density distribution across the survey. There are 510 599 sources above 5$\sigma$ with flux densities between 32 µ Jy and 11 Jy.