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The MeerKAT International GHz Tiered Extragalactic Exploration Survey (MIGHTEE) is one of the large survey projects using the MeerKAT telescope, covering four fields that have a wealth of ancillary data available. We present Data Release 1 of the MIGHTEE continuum survey, releasing total intensity images and catalogues over |$\sim$| 20 deg |$^2$|⁠ , across three fields at |$\sim$| 1.2–1.3 GHz. This includes 4.2 deg |$^2$| over the Cosmic Evolution Survey (COSMOS) field, 14.4 deg |$^2$| over the XMM Large-Scale Structure (XMM-LSS) field and deeper imaging over 1.5 deg |$^2$| of the Extended Chandra Deep Field South (CDFS). We release images at both a lower resolution (7–9 arcsec) and higher resolution (⁠|$\sim 5$|  arcsec). These images have central rms sensitivities of |$\sim 1.3-$| 2.7 |$\mu$| Jy beam |$^{-1}$| (⁠|$\sim 1.2-$| 3.6 |$\mu$| Jy beam |$^{-1}$|⁠) in the lower (higher) resolution images, respectively. We also release catalogues comprised of |$\sim$| 144 000 (⁠|$\sim$| 114 000) sources using the lower (higher) resolution images. We compare the astrometry and flux-density calibration with the Early Science data in the COSMOS and XMM-LSS fields and previous radio observations in the CDFS field, finding broad agreement. Furthermore, we extend the source counts at the |$\sim$| 10 |$\mu$| Jy level to these larger areas (⁠|$\sim 20$| deg |$^2$|⁠) and, using the areal coverage of MIGHTEE we measure the sample variance for differing areas of sky. We find a typical sample variance of 10 –20 per cent for 0.3 and 0.5 deg2 subregions at |$S_{1.4} \le 200$| |$\mu$| Jy, which increases at brighter flux densities, given the lower source density and expected higher galaxy bias for these sources. [ABSTRACT FROM AUTHOR]

Radio frequency interference (RFI) is emitted from various sources, terrestrial or orbital, and creates a nuisance for ground-based 21-cm experiments. In particular, single-dish observations will be highly susceptible to RFI due to their wide primary beam and sensitivity. This work aimed to simulate the contamination effects from the Radio Navigational Satellite System (RNSS) within the 1100–1350 (MHz) frequency band. The simulation can be divided into two parts: (i) satellite positioning, emission power, and the beam response on the telescope, and (ii) calibration of the satellite signals to data to improve the original model. We utilize previously observed single-dish L -band data from the Meer-Karoo Array Telescope (MeerKAT), which requires special calibration to account for regions contaminated by satellite-based RFI. We find that we can recreate the satellite contamination with high accuracy around its peak frequencies provided the satellite is not too close to the telescope's pointing direction. The simulation can predict satellite movements and signals for past and future observations, aiding in RFI avoidance and testing novel cleaning methods. The predicted signal sits below the noise in the target cosmology window in the L band (970–1015 MHz) making it difficult to confirm any out-of-band emission from satellites. However, in our simulations, this contamination still overwhelmed the 21-cm auto-power spectrum. Nevertheless, it is possible to detect the signal in cross-correlations after mild foreground cleaning. Whether such out of band contamination does exist will require further characterization of the satellite signals far away from their peak frequencies. [ABSTRACT FROM AUTHOR]

Graph algorithms are challenging to implement due to their varying topology and irregular access patterns. Real-world graphs are dynamic in nature and routinely undergo edge and vertex additions, as well as, deletions. Typical examples of dynamic graphs are social networks, collaboration networks, and road networks. Applying static algorithms repeatedly on dynamic graphs is inefficient. Further, due to the rapid growth of unstructured and semi-structured data, graph algorithms demand efficient parallel processing. Unfortunately, we know only a little about how to efficiently process dynamic graphs on massively parallel architectures such as GPUs. Existing approaches to represent and process dynamic graphs are either not general or are inefficient. In this work, we propose a graph library for dynamic graph algorithms over a GPU-tailored graph representation and exploits the warp-cooperative work-sharing execution model. The library, named Meerkat, builds upon a recently proposed dynamic graph representation on GPUs. This representation exploits a hashtable-based mechanism to store a vertex's neighborhood. Meerkat also enables fast iteration through a group of vertices, a pattern common and crucial for achieving performance in graph applications. Our framework supports dynamic edge additions and edge deletions, along with their batched versions. Based on the efficient iterative patterns encoded in Meerkat, we implement dynamic versions of popular graph algorithms such as breadth-first search, single-source shortest paths, triangle counting, PageRank, and weakly connected components. We evaluated our implementations over the ones in other publicly available dynamic graph data structures and frameworks: GPMA, Hornet, and faimGraph. Using a variety of real-world graphs, we observe that Meerkat significantly improves the efficiency of the underlying dynamic graph algorithm, outperforming these frameworks. [ABSTRACT FROM AUTHOR]

High-redshift protoclusters consisting of dusty starbursts are thought to play an important role in galaxy evolution. Their dusty nature makes them bright in the far-infrared (FIR)/submm but difficult to find in optical/near-infrared (NIR) surveys. Radio observations are an excellent way to study these dusty starbursts, as dust is transparent in the radio and there is a tight correlation between the FIR and radio emission of a galaxy. Here, we present MeerKAT 1.28 GHz radio imaging of three Herschel candidate protoclusters, with a synthesized beam size of |$\sim 7.5\, \mathrm{ arcsec}\times 6.6$|  arcsec and a central thermal noise down to |$4.35~\mu$| Jy beam−1. Our source counts are consistent with other radio counts with no evidence of overdensities. Around 95 per cent of the Herschel sources have 1.28 GHz IDs. Using the Herschel |$250~\mu$| m primary beam size as the searching radius, we find 54.2 per cent Herschel sources have multiple 1.28 GHz IDs. Our average FIR-radio correlation coefficient |$q_{250\mu \text{m}}$| is |$2.33\pm 0.26$|⁠. Adding |$q_{250\mu \text{m}}$| as a new constraint, the probability of finding chance-aligned sources is reduced by a factor of |$\sim 6$|⁠ , but with the risk of discarding true identifications of radio-loud/quiet sources. With accurate MeerKAT positions, we cross-match our Herschel sources to optical/NIR data followed by photometric redshift estimations. By removing |$z< 1$| sources, the density contrasts of two of the candidate protoclusters increase, suggestive of them being real protoclusters at |$z> 1$|⁠. There is also potentially a |$0.9< z< 1.2$| overdensity associated with one candidate protocluster. In summary, photometric redshifts from radio-optical cross-identifications have provided some tentative evidence of overdensities aligning with two of the candidate protoclusters. [ABSTRACT FROM AUTHOR]

We present deep, wideband multifrequency radio observations (144 MHz−8 GHz) of the remarkable galaxy group NGC 741, which yield crucial insights into the interaction between the infalling head-tail radio galaxy (NGC 742) and the main group. Our new data provide an unprecedentedly detailed view of the NGC 741-742 system, including the shock cone, disrupted jets from NGC 742, the long (∼255 kpc) braided southern radio tail, and the eastern lobe-like structure (∼100 kpc), and reveal, for the first time, complex radio filaments throughout the tail and lobe, and a likely vortex ring behind the shock cone. The cone traces the bow shock caused by the supersonic ( M ∼ 2 ) interaction between the head-tail radio galaxy NGC 742 and the intragroup medium (IGrM), while the ring may have been formed by the interaction between the NGC 742 shock and a previously existing lobe associated with NGC 741. This interaction plausibly compressed and reaccelerated the radio plasma. We estimate that shock-heating by NGC 742 has likely injected ∼2–5 × 1057 erg of thermal energy into the central 10 kpc cooling region of the IGrM, potentially affecting the cooling and feedback cycle of NGC 741. A comparison with Chandra X-ray images shows that some of the previously detected thermal filaments align with radio edges, suggesting compression of the IGrM as the relativistic plasma of the NGC 742 tail interacts with the surrounding medium. Our results highlight that multifrequency observations are key to disentangling the complex, intertwined origins of the variety of radio features seen in the galaxy group NGC 741, and the need for simulations to reproduce all the detected features. [ABSTRACT FROM AUTHOR]

In oviparous vertebrates, maternal androgens can alter offspring immune function, particularly early in development, but the potential for negative health effects of maternal androgens in mammals remains unclear. We investigated the relation between maternal androgens, particularly in late gestation, and offspring health in the meerkat (Suricata suricatta) by comparing offspring from (a) normative dominant and subordinate matrilines, whose dams naturally express high versus lower circulating androgen concentrations, respectively, and (b) normative dominant and antiandrogen‐treated dominant matrilines, whose dams' androgen function was intact versus blocked owing to experimental antagonism of the latter's androgen receptors (using Flutamide). Foetal offspring thus experienced three different endocrine environments ('high', 'lower' and 'blocked' androgens) late in prenatal development. We assessed parasitism, immune function, sex steroid concentrations and survivorship in these three offspring groups, both during juvenility and early adulthood. The juvenile offspring of subordinate control and dominant treated dams generally had lower intensities of parasite infections and greater immune function than did their peers from dominant control dams—patterns not found in adult offspring, or in relation to the offspring's concurrent hormone concentrations. Survivorship to adulthood was greatest in the progeny of treated dams. Descendants of dominant female meerkats—those in the 'high' prenatal androgen category—suffered increased parasitism and decreased immunocompetence as juveniles, as well as reduced survivorship relative to antiandrogen‐exposed peers, providing evidence in mammals that maternal androgens can negatively impact offspring health and survival. These intergenerational, androgen‐mediated, health effects represent early costs imposed by female intrasexual competition and its associated selection pressures. [ABSTRACT FROM AUTHOR]

Dominance is a primary determinant of social dynamics and resource access in social animals. Recent studies show that dominance is also reflected in the gene regulatory profiles of peripheral immune cells. However, the strength and direction of this relationship differs across the species and sex combinations investigated, potentially due to variation in the predictors and energetic consequences of dominance status. Here, we investigated the association between social status and gene expression in the blood of wild meerkats (Suricata suricatta; n = 113 individuals), including in response to lipopolysaccharide, Gardiquimod (an agonist of TLR7, which detects single‐stranded RNA in vivo) and glucocorticoid stimulation. Meerkats are cooperatively breeding social carnivores in which breeding females physically outcompete other females to suppress reproduction, resulting in high reproductive skew. They therefore present an opportunity to disentangle the effects of social dominance from those of sex per se. We identify a sex‐specific signature of dominance, including 1045 differentially expressed genes in females but none in males. Dominant females exhibit elevated activity in innate immune pathways and a larger fold‐change response to LPS challenge. Based on these results and a preliminary comparison to other mammals, we speculate that the gene regulatory signature of social status in the immune system depends on the determinants and energetic costs of social dominance, such that it is most pronounced in hierarchies where physical competition is important and reproductive skew is large. Such a pattern has the potential to mediate life history trade‐offs between investment in reproduction versus somatic maintenance. [ABSTRACT FROM AUTHOR]

Neutral hydrogen (H  i) serves as a competitive tracer of the large scale structures, especially with the advent of more intensity mapping H  i surveys. In this work, we present a simulation-based framework to forecast the H  i power spectrum on non-linear scales (⁠|$k\gtrsim 1\ {\rm Mpc^{-1}}$|⁠), as measured by interferometer arrays like MeerKAT in the low-redshift (⁠|$z\le 1.0$|⁠) Universe. Building on a galaxy-based H  i mock catalogue, we meticulously consider various factors, including the emission line profiles of H  i discs and some observational settings, and explore their impacts on the H  i power spectrum. We find that the H  i power spectrum is relatively insensitive to the profile shape of H  i emission line at these scales, while showing a strong correlation with the profile width. We propose an empirical model to simulate the emission line profile width for each H  i source. The resulting H  i power spectrum is consistent with the results from the IllustrisTNG hydrodynamical simulation and follows the trend of the measurements obtained by MeerKAT at |$z\approx 0.44$|⁠ , though with a significantly lower amplitude. We demonstrate how the H  i abundance |$\Omega _{\rm HI}$| and the amplitude parameter in our width model can be constrained with the MeerKAT measurements, though a strong degeneracy is uncovered. Our work shows the potential to constrain statistical properties of H  i emission line profiles with future H  i intensity mapping experiments. [ABSTRACT FROM AUTHOR]

Introduction: Mammalian reproductive and somatic development is regulated by steroid hormones, growth hormone (GH), and insulin-like growth factor-1 (IGF-1). Based largely on information from humans, model organisms, and domesticated animals, testosterone (T) and the GH/IGF-1 system activate sexually differentiated development, promoting male-biased growth, often at a cost to health and survivorship. To test if augmented prenatal androgen exposure in females produces similar developmental patterns and trade-offs, we examine maternal effects in wild meerkats (Suricata suricatta), a non-model species in which adult females naturally, albeit differentially by status, express exceptionally high androgen concentrations, particularly during pregnancy. In this cooperative breeder, the early growth of daughters predicts future breeding status and reproductive success. Methods: We examine effects of normative and experimentally induced variation in maternal androgens on the ontogenetic patterns in offspring reproductive hormones (androstenedione, A4; T; estradiol, E2), IGF-1, growth from pup emergence at 1 month to puberty at 1 year, and survivorship. Specifically, we compare the male and female offspring of dominant control (DC or high-T), subordinate control (SC or lower-T), and dominant treated (DT or blocked-T) dams, the latter having experienced antiandrogen treatment in late gestation. Results: Meerkat offspring showed sex differences in absolute T and IGF-1 concentrations, developmental rates of A4 and E2 expression, and survivorship -- effects that were sometimes socially or environmentally modulated. Atypical for mammals were the early male bias in T that disappeared by puberty, the absence of sex differences in A4 and E2, and the female bias in IGF-1. Food availability was linked to steroid concentrations in females and to IGF-1, potentially growth, and survival in both sexes. Maternal treatment significantly affected rates of T, E2, and IGF-1 expression, and weight, with marginal effects on survivorship; offspring of DT dams showed peak IGF-1 concentrations and the best survivorship. Discussion: Maternal effects thus impact offspring development in meerkats, with associated trade-offs: Whereas prenatal androgens modify postnatal reproductive and somatic physiology, benefits associated with enhanced competitiveness in DC lineages may have initial costs of reduced IGF-1, delay in weight gain, and decreased survivorship. These novel data further confirm the different evolutionary and mechanistic pathways to cooperative breeding and call for greater consideration of natural endocrine variation in both sexes. [ABSTRACT FROM AUTHOR]

Japanese encephalitis virus (JEV) is the leading cause of human encephalitis in Asia. JEV is a vector-borne disease, mainly transmitted by Culex mosquitoes, with Ardeidae birds as maintenance hosts and pigs as amplifying hosts. Other vertebrate animal hosts have been suggested to play a role in the epidemiology of JEV. This scoping review followed PRISMA guidelines to identify species in which evidence of naturally occurring JEV infection was detected in vertebrates other than ardeid birds, pigs and people. Following systematic searches, 4372 records were screened, and data were extracted from 62 eligible studies. Direct evidence (virus, viral antigen or viral RNA) of JEV infection was identified in a variety of mammals and birds (not always identified to the species level), including bats, passerine birds (family Turdidae), livestock (cattle [Bos taurus] and a goat [Capra hircus]), carnivores (two meerkats [Suricata suricatta]), and one horse (Equus caballus). Bat families included Pteropodidae, Vespertilionidae, Rhinolophidae, Miniopteridae, Hipposideridae. Indirect evidence (antibodies) was identified in several mammalian and avian orders, as well as reported in two reptile species. However, a major limitation of the evidence of JEV infection identified in this review was diagnostic test accuracy, particularly for serological testing. Studies generally did not report diagnostic sensitivity or specificity which is critical given the potential for cross-reactivity in orthoflavivirus detection. We hypothesise that bats and passerine birds could play an underappreciated role in JEV epidemiology; however, development of diagnostic tests to differentiate JEV from other orthoflaviviruses will be essential for effective surveillance in these, as well as the companion and livestock species that could be used to evaluate JEV control measures in currently endemic regions. Author summary: Japanese encephalitis virus (JEV) is the leading cause of encephalitis in Asia and the Western Pacific, with estimated 100,000 cases in people (mainly children) annually. Up to one third of cases result in death, and of those who survive, half can suffer ongoing neurological problems. Japanese encephalitis virus circulation is complex. It is transmitted via mosquitoes between hosts. Although well-known key hosts include pigs and water birds, our review showed that there are others that should be considered in surveillance programs such as bats and perching birds. We also found that detection is challenging because diagnostic tests cross-react with other viruses. Both improved understanding of hosts and better diagnostic tests are needed to develop surveillance systems to reduce JEV incidence in people. [ABSTRACT FROM AUTHOR]

We report observations of the highly active FRB 20240114A with MeerKAT using the ultra-high frequency (UHF; |$544\!-\!1088$|  MHz) and L band (⁠|$856\!-\!1712$|  MHz) receivers. A total of 62 bursts were detected in coherent tied-array beams using the MeerTRAP real-time transient detection pipeline. We measure a structure-optimizing dispersion measure of |$527.65\pm 0.01\, \text{pc}\, \text{cm}^{-3}$| using the brightest burst in the sample. We find the bursts of FRB 20240114A are generally detected in part of the broad-band of MeerKAT, |$\sim 40~{{\ \rm per\ cent}}$| in the UHF and |$\sim 30~{{\ \rm per\ cent}}$| in the L band, indicating the band limited nature. We analyse the fluence distribution of the 44 bursts detected at UHF, constraining the fluence completeness limit to |$\sim 1$|  Jy ms, above which the cumulative burst rate follows a power law |$R (\gt F)\propto (F/1\, \text{Jy}\, \text{ms})^\gamma$| with |$\gamma =-1.8\pm 0.2$|⁠. Using channelized telescope data captured in our transient buffer we localize FRB 20240114A in the image domain to RA = 21h27m39.86s, Dec. = +04d19m45.01s with an uncertainty of 1.4 arcsec. This localization allows us to confidently identify the host galaxy of FRB 20240114A. Also using the transient buffer data, we perform a polarimetric study and demonstrate that most of the bursts have |$\sim 100~{{\ \rm per\ cent}}$| linear polarization fractions and up to |$\sim 20~{{\ \rm per\ cent}}$| circular polarization fractions. Finally, we predict the flux density of a potential persistent radio source (PRS) associated with FRB 20240114A is |$\backsimeq [0.6\!-\!60]\, \mu \text{Jy}$| based on the simple relation between the luminosity of the PRS and the rotation measure arising from the FRB local environment. [ABSTRACT FROM AUTHOR]

Context. Tailed radio galaxies are shaped by ram pressure that is due to the high-velocity motion of their host through the intracluster medium (ICM). Recent works have reported on the increasing complexity of the phenomenology of tailed galaxies, with departures from theoretical ageing models and novel evidence of re-energising mechanisms that are nonetheless unclear. Aims. The nearby (z = 0.0894) galaxy cluster Abell 2142 hosts two tailed galaxies, namely T1 and T2, which exhibit peculiar morphological features. We aim to investigate the properties of T1 and T2 and constrain their spectral evolution, dynamics, and interactions with the ICM. Methods. We combined data from LOw Frequency Array (LOFAR), upgraded Giant Metrewave Radio Telescope (uGMRT), Very Large Array (VLA), and MeerKAT (from 30 MHz to 6.5 GHz) to carry out a detailed spectral analysis of T1 and T2. We analysed the surface brightness profiles, measured integrated and spatially resolved spectral indices. We performed a comparison with single injection ageing models. The Chandra X-ray data were used to search for discontinuities in the ICM properties in the direction of the targets. Results. The spectral properties of T1 at low frequencies can be predicted by ageing models and provide constraints on the 3D dynamics of the host by assuming a constant velocity. However, a more complex scenario is suggested by the sharp transitions along sub-regions of the tail, local surface brightness enhancements, and a spectral shape at high frequencies that is not predicted by any of the models. This scenario may plausibly involve hydrodynamical instabilities and particle mixing. T2 exhibits unusual morphological and surface brightness features, and its spectral behaviour is not predicted by standard models. The effects of two active galactic nucleus (AGN) outburst events during the infall of T2 towards the cluster centre could potentially explain its characteristic properties. [ABSTRACT FROM AUTHOR]

We present the serendipitous discovery of a new radio-continuum ring-like object nicknamed Kýklos (J1802–3353), with MeerKAT UHF and L-band observations. The radio ring, which resembles the recently discovered odd radio circles (ORCs), has a diameter of ∼80″ and is located just ∼6° from the Galactic plane. However, Kýklos exhibits an atypical thermal radio-continuum spectrum (α = −0.1 ± 0.3), which led us to explore different possible formation scenarios. We concluded that a circumstellar shell around an evolved massive star, possibly a Wolf-Rayet, is the most convincing explanation with the present data. [ABSTRACT FROM AUTHOR]

We present MeerKAT Fornax Survey H I observations of NGC 1427A, a blue irregular galaxy with a stellar mass of ∼2 × 109 M⊙ located near the centre of the Fornax galaxy cluster. Thanks to the excellent resolution (1–6 kpc spatially, 1.4 km s−1 in velocity) and H I column density sensitivity (∼4 × 1019 to ∼1018 cm−2 depending on resolution), our data deliver new insights on the long-debated interaction of this galaxy with the cluster environment. We confirm the presence of a broad, one-sided, starless H I tail stretching from the outer regions of the stellar body and pointing away from the cluster centre. We find the tail to have 50% more H I (4 × 108 M⊙) and to be 3 times longer (70 kpc) than in previous observations. In fact, we detect scattered H I clouds out to 300 kpc from the galaxy in the direction of the tail – possibly the most ancient remnant of the passage of NGC 1427A through the intracluster medium of Fornax. Both the velocity gradient along the H I tail and the peculiar kinematics of H I in the outer region of the stellar body are consistent with the effect of ram pressure given the line-of-sight motion of the galaxy within the cluster. However, several properties cannot be explained solely by ram pressure and suggest an ongoing tidal interaction. This includes: the close match between dense H I and stars within the disturbed stellar body; the abundant kinematically anomalous H I; and the inversion of the H I velocity gradient near the base of the H I tail. We rule out an interaction with the cluster tidal field, and conclude that NGC 1427A is the result of a high-speed galaxy encounter or of a merger started at least 300 Myr ago, where ram pressure shapes the distribution and kinematics of the H I in the perturbed outer stellar body and in the tidal tails. [ABSTRACT FROM AUTHOR]

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Localization of fast radio bursts (FRBs) to arcsecond and subarcsecond precision maximizes their potential as cosmological probes. To that end, FRB detection instruments are deploying triggered complex-voltage capture systems to localize FRBs, identify their host galaxy, and measure a redshift. Here, we report the discovery and localization of two FRBs (20220717A and 20220905A) that were captured by the transient buffer system deployed by the MeerTRAP instrument at the MeerKAT telescope in South Africa. We were able to localize the FRBs to precision of |$\sim$| 1 arcsecond that allowed us to unambiguously identify the host galaxy for FRB 20220717A (posterior probability |$\sim$| 0.97). FRB 20220905A lies in a crowded region of the sky with a tentative identification of a host galaxy but the faintness and the difficulty in obtaining an optical spectrum preclude a conclusive association. The bursts show low linear polarization fractions (10–17 per cent) that conform to the large diversity in the polarization fraction observed in apparently non-repeating FRBs akin to single pulses from neutron stars. We also show that the host galaxy of FRB 20220717A contributes roughly 15 per cent of the total dispersion measure (DM), indicating that it is located in a plasma-rich part of the host galaxy which can explain the large rotation measure. The scattering in FRB 20220717A can be mostly attributed to the host galaxy and the intervening medium and is consistent with what is seen in the wider FRB population. [ABSTRACT FROM AUTHOR]

We use data from the MeerTime project on the MeerKAT telescope to ask whether the radio emission properties of millisecond pulsars (MSPs) and slowly rotating, younger pulsars (SPs) are similar or different. We show that the flux density spectra of both populations are similarly steep, and the widths of MSP profiles obey the same dependence on the rotational period as slow pulsars. We also show that the polarization of MSPs has similar properties to slow pulsars. The commonly used pseudo-luminosity of pulsars, defined as the product of the flux density and the distance squared, is not appropriate for drawing conclusions about the relative intrinsic radio luminosity of SPs and MSPs. We show that it is possible to scale the pseudo-luminosity to account for the pulse duty cycle and the solid angle of the radio beam, in such a way that MSPs and SPs do not show clear differences in intrinsic luminosity. The data therefore support common emission physics between the two populations in spite of orders of magnitude difference in their period derivatives and inferred, surface, dipole magnetic field strengths. [ABSTRACT FROM AUTHOR]

We present the first detailed radio study of the galaxy cluster XMMXCS J2215.9−1738 at z  = 1.46 using MeerKAT L -band (1.3 GHz) observations. We combine our radio observation with archival optical and infrared data to investigate the star formation and active galactic nucleus (AGN) population within |$R_{200}$| (⁠|$R =$| 0.8 Mpc) of the cluster centre. Using three selection criteria; the radio luminosity, the far-infrared radio ratio (⁠|$q_{\rm {IR}}$|⁠), and the mid-infrared colour, we distinguish galaxies with radio emission predominantly powered by star formation from that powered by AGNs. We selected 24 cluster members within |$R_{\rm {200}}$| in the MeerKAT image based on either their photometric or spectroscopic redshift. We classified 12/24 (50 per cent) as galaxies whose radio emission is dominated by star-formation activity, 6/24 (25 per cent) as intermediate star-forming galaxies, and 6/24 (25 per cent) as AGN-dominated galaxies. Using the radio continuum luminosities of the star-forming cluster galaxies, we estimated an integrated star formation rate (SFR) value of 1700 |$\pm$| 330 M |$_{\odot }$|  yr |$^{-1}$| within |$R_{200}$|⁠. We derived a mass-normalized integrated SFR value of |$(570 \pm 110) \times 10^{-14}$|  yr |$^{-1}$|⁠. This supports previous observational and theoretical studies that indicated a rapid increase in star formation activity within the core of high-redshift clusters. We also show that the high-AGN fraction within the cluster core is consistent with previous cluster observations at |$z \gt $| 1.5. [ABSTRACT FROM AUTHOR]

It was argued in a series of experimental studies that Japanese tits (Parus minor) have an ABC call that has an alert function, a D call that has a recruitment function, and an ABC‐D call that is compositionally derived from ABC and D, and has a mobbing function. A key conclusion was that ABC‐D differs from the combination of separate utterances of ABC and of D (e.g. as played by distinct but close loudspeakers). While the logic of the argument is arguably sound, no explicit rule has been proposed to derive the meaning of ABC‐D from that of its parts. We compare two analyses. One posits a limited instance of semantic compositionality ('Minimal Compositionality'); the other does without compositionality, but uses instead a more sophisticated pragmatics ('Bird Implicatures'). Minimal Compositionality takes the composition of ABC and D to deviate only minimally from what would be found with two independent utterances: ABC means that 'there is something that licenses an alert', D means that 'there is something that licenses recruitment', and ABC‐D means that 'there is something that licenses both an alert and recruitment'. By contrast, ABC and D as independent utterances yield something weaker, namely: 'there is something that licenses an alert, and there is something that licenses recruitment', without any 'binding' across the two utterances. The second theory, Bird Implicatures, only requires that ABC‐D should be more informative than ABC, and/or than D. It builds on the idea, proposed for several monkey species, that a less‐informative call competes with a more informative one (the 'Informativity Principle'): when produced alone, ABC and D trigger an inference that ABC‐D is false. We explain how both Minimal Compositionality and Bird Implicatures could have evolved, and we compare the predictions of the two theories. Finally, we extend the discussion to some chimpanzee and meerkat sequences that might raise related theoretical problems. [ABSTRACT FROM AUTHOR]

Animal vocal communication research traditionally focuses on acoustic and contextual features of calls, yet substantial information is also contained in response selectivity and timing during vocalization events. By examining the spatiotemporal structure of vocal interactions, we can distinguish between 'broadcast' and 'exchange' signalling modes, with the former potentially serving to transmit signallers' general state and the latter reflecting more interactive signalling behaviour. Here, we tracked the movements and vocalizations of wild meerkat (Suricata suricatta) groups simultaneously using collars to explore this distinction. We found evidence that close calls (used for maintaining group cohesion) are given as signal exchanges. They are typically given in temporally structured call–response sequences and are also strongly affected by the social environment, with individuals calling more when they have more neighbours and juveniles responding more to adults than the reverse. In contrast, short note calls appear mainly in sequences produced by single individuals and show little dependence on social surroundings, suggesting a broadcast signalling mode. Despite these differences, both call categories show similar clustering in space and time at a group level. Our results highlight how the fine-scale structure of vocal interactions can give important insights into the usage and function of signals in social groups. This article is part of the theme issue 'The power of sound: unravelling how acoustic communication shapes group dynamics.' [ABSTRACT FROM AUTHOR]

We conducted a search for |$\textrm {H}\, \scriptstyle \mathrm{I}$| emission of the gas-rich galaxies in the Vela region (260° ≤ ℓ ≤ 290°, −2° ≤ b ≤ 1°) to explore the Vela Supercluster (VSCL) at V hel ∼ 18 000  |$\rm km\, s^{-1}$|⁠ , largely obscured by Galactic dust. Within the mostly Radio Frequency Interference-free band (250 < V hel < 25 000  |$\rm km\, s^{-1}$|⁠) of MeerKAT, the analysis focuses on 157 hexagonally distributed pointings extracted from the South African Radio Astronomy Observatory MeerKAT Galactic Plane Survey located in the Vela region (Vela−SMGPS). These were combined into 10 contiguous mosaics, covering an ∼90 square degrees area. Among the 843 |$\textrm {H}\, \scriptstyle \mathrm{I}$| detected sources, 39 were previously discovered in the H  i Parkes Zone of Avoidance survey (V hel < 12 000  |$\rm km\, s^{-1}$|⁠ ; rms ∼ 6  |$\rm mJy\, beam^{-1}$|⁠). With the improved rms level of the Vela−SMGPS, i.e. 0.29–0.56  |$\rm mJy\, beam^{-1}$|⁠ , our study unveils nearly 12 times more detections (471 candidates) in that same velocity range. We furthermore could identify 187 galaxy candidates with an |$\textrm {H}\, \scriptstyle \mathrm{I}$| mass limit reaching |$\log (M_{\rm HI}/\rm {\rm M}_{\odot }) = 9.44$| in the VSCL velocity range V hel ∼ 19 500 ± 3500  |$\rm km\, s^{-1}$|⁠. We find indications of two wall-like overdensities that confirm the original suspicion that these walls intersect at low latitudes around longitudes of ℓ ∼ 272°–278°. We also find a strong signature most likely associated with the Hydra/Antlia extension and evidence of a previously unknown narrow filament at V hel ∼ 12 000 |$\rm km\, s^{-1}$|⁠. This paper demonstrates the efficiency of systematic |$\textrm {H}\, \scriptstyle \mathrm{I}$| surveys with the Square Kilometre Array (SKA) precursor MeerKAT, even in the most obscured part of the Zone of Avoidance. [ABSTRACT FROM AUTHOR]

We present the serendipitous discovery of (1) a large double radio relic associated with the galaxy cluster PSZ2 G277.93 + 12.34 and (2) a new odd radio circle, ORC J1027–4422, both found in the same deep MeerKAT 1.3 GHz wide-band radio continuum image. The angular separation of the two arc-shaped cluster relics is ∼16 arcmin or ∼2.6 Mpc for a cluster redshift of z ≈ 0.158. The thin southern relic, which shows several ridges/shocks including one possibly moving inwards, has a linear extent of ∼1.64 Mpc. In contrast, the northern relic is about twice as wide, twice as bright, but only has a largest linear size of ∼0.66 Mpc. Complementary SRG/eROSITA X-ray images reveal extended emission from hot intracluster gas between the two relics and around the narrow-angle tail (NAT) radio galaxy PMN J1033–4335 (z ≈ 0.153) located just east of the northern relic. The radio morphologies of the NAT galaxy and the northern relic, which are also detected with the Australian Square Kilometer Array Pathfinder (ASKAP) at 888 MHz, suggest both are moving in the same outward direction. The discovery of ORC J1027–4422 in a different part of the same MeerKAT image makes it the fourth known single ORC. It has a diameter of ∼90 arcsec corresponding to 400 kpc at a tentative redshift of z ≈ 0.3 and remains undetected in X-ray emission. Supported by simulations, we discuss similarities between outward moving galaxy and cluster merger shocks as the formation mechanisms for ORCs and radio relics, respectively. [ABSTRACT FROM AUTHOR]

The sensitivity of the MeerKAT radio interferometer is an opportunity to probe deeper into the population of rare and faint extragalactic pulsars. The TRAPUM (TRAnsients and PUlsars with MeerKAT) collaboration has conducted a radio-domain search for accelerated pulsars and transients in the Small Magellanic Cloud (SMC). This partially targeted survey, performed at L band (856–1712 MHz) with the core array of the MeerKAT telescope in 2-h integrations, is twice as sensitive as the latest SMC radio pulsar survey. We report the discovery of seven new SMC pulsars, doubling this galaxy's radio pulsar population and increasing the total extragalactic population by nearly a quarter. We also carried out a search for accelerated millisecond pulsars in the SMC globular cluster NGC 121 using the full array of MeerKAT. This improved the previous upper limit on pulsed radio emission from this cluster by a factor of 6. Our discoveries reveal the first radio pulsar-PWN systems in the SMC, with only one such system previously known outside our Galaxy (the 'Crab pulsar twin' in the Large Magellanic Cloud, PSR J0540−6919). We associate the 59 ms pulsar discovery PSR J0040−7337, now the fastest spinning radio pulsar in the SMC, with the bow-shock Pulsar Wind Nebula (PWN) of supernova remnant DEM S5. We also present a new young pulsar with a 79 ms period, PSR J0048−7317, in a PWN recently discovered in a MeerKAT radio continuum image. Using the multibeam capability of MeerKAT, we localized our pulsar discoveries, and two previous Murriyang discoveries, to a positional uncertainty of a few arcseconds. [ABSTRACT FROM AUTHOR]

We present the SARAO MeerKAT Galactic Plane Survey (SMGPS), a 1.3 GHz continuum survey of almost half of the Galactic Plane (251° ≤ l ≤ 358° and 2° ≤ l ≤ 61° at | b | ≤ |$1{_{.}^{\circ}}5$|⁠). SMGPS is the largest, most sensitive, and highest angular resolution 1 GHz survey of the plane yet carried out, with an angular resolution of 8 arcsec and a broad-band root-mean-square sensitivity of ∼10–20 μJy beam−1. Here, we describe the first publicly available data release from SMGPS which comprises data cubes of frequency-resolved images over 908–1656 MHz, power-law fits to the images, and broad-band zeroth moment integrated intensity images. A thorough assessment of the data quality and guidance for future usage of the data products are given. Finally, we discuss the tremendous potential of SMGPS by showcasing highlights of the Galactic and extragalactic science that it permits. These highlights include the discovery of a new population of non-thermal radio filaments; identification of new candidate supernova remnants, pulsar wind nebulae and planetary nebulae; improved radio/mid-infrared classification of rare luminous blue variables and discovery of associated extended radio nebulae; new radio stars identified by Bayesian cross-matching techniques; the realization that many of the largest radio-quiet Wide-field Infrared Survey Explorer (WISE) H  ii region candidates are not true H  ii regions; and a large sample of previously undiscovered background H  i galaxies in the Zone of Avoidance. [ABSTRACT FROM AUTHOR]

The Square Kilometer Array Reconfigurable Application Board (SKARAB) is a Xilinx Virtex-7 FPGA-based platform designed for the MeerKAT array, to be used for both F- and X/B-engines. The MeerKAT F-engine receives digitized data, thus no samplers are required on the SKARAB-based platform. Among the alternative options available, a high-performing ADC mezzanine board can be used in conjunction with the SKARAB, which allows four 1.4-GHz-wide input channels to be digitized and processed. In this paper, we outline how the SKARAB has been successfully used for single-dish applications including imaging, spectroscopy, and spectro-polarimetry. [ABSTRACT FROM AUTHOR]

Redbacks are millisecond pulsar binaries with low-mass, irradiated companions. These systems have a rich phenomenology that can be used to probe binary evolution models, pulsar wind physics, and the neutron star mass distribution. A number of high-confidence redback candidates have been identified through searches for variable optical and X-ray sources within the localization regions of unidentified but pulsar-like Fermi -LAT gamma-ray sources. However, these candidates remain unconfirmed until pulsations are detected. As part of the TRAPUM project, we searched for radio pulsations from six of these redback candidates with MeerKAT. We discovered three new radio millisecond pulsars, PSRs J0838−2827, J0955−3947, and J2333−5526, confirming their redback nature. PSR J0838−2827 remained undetected for 2 yr after our discovery despite repeated observations, likely due to evaporated material absorbing the radio emission for long periods of time. While, to our knowledge, this system has not undergone a transition to an accreting state, the disappearance, likely caused by extreme eclipses, illustrates the transient nature of spider pulsars and the heavy selection bias in uncovering their radio population. Radio timing enabled the detection of gamma-ray pulsations from all three pulsars, from which we obtained 15-yr timing solutions. All of these sources exhibit complex orbital period variations consistent with gravitational quadrupole moment variations in the companion stars. These timing solutions also constrain the binary mass ratios, allowing us to narrow down the pulsar masses. We find that PSR J2333−5526 may have a neutron star mass in excess of 2 M⊙. [ABSTRACT FROM AUTHOR]

The S-shaped swing of the linear polarization position angle (PPA) observed in many pulsars can be interpreted by the rotating vector model (RVM). However, efforts to fit the RVM for a large sample of pulsars observed with the MeerKAT telescope as a part of the Thousand-Pulsar-Array (TPA) programme, only succeeded for about half the cases. High time-resolution studies suggest that the failed cases arise due to the presence of orthogonal polarization modes, or highly disordered distribution of PPA points. One such example is PSR J1645−0317. Recently it has been shown that the RVM can be recovered in this pulsar by using only time samples which are greater than 80 per cent linearly polarized. In this work, we test this novel approach on the brightest 249 pulsars from the TPA sample, of which 177 yield sufficient highly polarized samples to be amenable to our method. Remarkably, only nine of these pulsars (5 per cent) now fail to fit the RVM as opposed to 59 per cent from the original analysis. This result favours the paradigm that the underlying mechanism is coherent curvature radiation. [ABSTRACT FROM AUTHOR]

In many animal species, including humans, producer arousal state is considered a key modifier of vocal production and structure. Encoding of affective arousal state in vocalizations provides a rapid means of information transfer about an individual's internal state, potentially reflecting its response to external stimuli. Meerkats, Suricata suricatta , are a highly vocal species. They use close calls to maintain group cohesion while foraging. Due to their patchily distributed prey, motivation for neighbour proximity varies; being too close results in competition (increased arousal–aggression), while too far results in risks of losing the group and predation threats (increased arousal–fear). We investigated how neighbour proximity and behavioural, social and environmental context influence the acoustic structure of wild meerkats' close calls. We found little effect of neighbour distance on the majority of the acoustic parameters measured, although close calls were longer and had a higher fundamental frequency when in very close proximity. However, there was a consistent effect of the behavioural context in which the call was given across several acoustic parameters. Overall, meerkat close calls potentially convey information on current behaviour, highlighting a potential mechanism in the diversification of acoustic signals. • Vocalizations play an important role in managing group cohesion. • We investigated how meerkats' close call acoustic structure varies with context. • Close call acoustic structure varied slightly with neighbour proximity. • Behavioural context had the main influence on close call acoustic structure. • Close call acoustic structure potentially conveys current behavioural state. [ABSTRACT FROM AUTHOR]

This study presents a detailed analysis of the GAL045.804 − 0.356 massive star-forming clump. A high-angular resolution and sensitivity observations were conducted using MeerKAT at 1.28 GHz and ALMA interferometer at 1.3 mm. Two distinct centimetre radio continuum emissions (source A and source B) were identified within the clump. A comprehensive investigation was carried out on source A, the G45.804 − 0.355 star-forming region (SFR) due to its association with Extended Green Object (EGO), 6.7 GHz methanol maser and the spatial coincidence with the peak of the dust continuum emission at 870 µm. The ALMA observations revealed seven dense dust condensations (MM1–MM7) in source A. The brightest (S ν ∼ 87 mJy) and massive main dense core, MM1, was co-located with the 6.7 GHz methanol maser. Explorations into the kinematics revealed gas motions characterized by a velocity gradient across the MM1 core. Furthermore, molecular line emission showed the presence of an extended arm-like structure, with a physical size of 0.25 pc × 0.18 pc (∼ 50 000 au × 30 000 au) at a distance of 7.3 kpc. Amongst these arms, two arms were prominently identified in both the dust continuum and some of the molecular lines. A blue-shifted absorption P-Cygni profile was seen in the H2CO line spectrum. The findings of this study are both intriguing and new, utilizing data from MeerKAT and ALMA to investigate the characteristics of the AGAL45 clump. The evidence of spiral arms, the compact nature of the EGO and < 2 km s−1 velocity gradient are all indicative of G45.804 − 0.355 being oriented face-on. [ABSTRACT FROM AUTHOR]

We report here on the timing of 597 pulsars over the last four years with the MeerKAT telescope. We provide times of arrival, pulsar ephemeris files, and per-epoch measurements of the flux density, dispersion measure (DM), and rotation measure (RM) for each pulsar. In addition, we use a Gaussian process to model the timing residuals to measure the spin frequency derivative at each epoch. We also report the detection of 11 glitches in nine individual pulsars. We find significant DM and RM variations in 87 and 76 pulsars, respectively. We find that the DM variations scale approximately linearly with DM, which is broadly in agreement with models of the ionized interstellar medium. The observed RM variations seem largely independent of DM, which may suggest that the RM variations are dominated by variations in the interstellar magnetic field on the line of sight, rather than varying electron density. We also find that normal pulsars have around 5 times greater amplitude of DM variability compared to millisecond pulsars, and surmise that this is due to the known difference in their velocity distributions. [ABSTRACT FROM AUTHOR]

Using MeerKAT , we have discovered three new millisecond pulsars (MSPs) in the bulge globular cluster M62: M62H, M62I, and M62J. All three are in binary systems, which means all ten known pulsars in the cluster are in binaries. M62H has a planetary-mass companion with a median mass M c, med ∼ 3 MJ and a mean density of ρ ∼ 11 g cm−3. M62I has an orbital period of 0.51 d and a M c, med ∼ 0.15 M⊙. Neither of these low-mass systems exhibit eclipses. M62J has only been detected in the two Ultra High Frequency band (816 MHz) observations with a flux density S 816 = 0.08 mJy. The non-detection in the L-band (1284 MHz) indicates it has a relatively steep spectrum (β < −3.1). We also present 23-yr-long timing solutions obtained using data from the Parkes 'Murriyang', Effelsberg , and MeerKAT telescopes for the six previously known pulsars. For all these pulsars, we measured the second spin-period derivatives and the rate of change of orbital period caused by the gravitational field of the cluster, and their proper motions. From these measurements, we conclude that the pulsars' maximum accelerations are consistent with the maximum cluster acceleration assuming a core-collapsed mass distribution. Studies of the eclipses of the redback M62B and the black widow M62E at four and two different frequency bands, respectively, reveal a frequency dependence with longer and asymmetric eclipses at lower frequencies. The presence of only binary MSPs in this cluster challenges models which suggest that the MSP population of core-collapsed clusters should be dominated by isolated MSPs. [ABSTRACT FROM AUTHOR]

We have determined positions, proper motions, and parallaxes of 77 millisecond pulsars (MSPs) from ∼3 yr of MeerKAT radio telescope observations. Our timing and noise analyses enable us to measure 35 significant parallaxes (12 of them for the first time) and 69 significant proper motions. Eight pulsars near the ecliptic have an accurate proper motion in ecliptic longitude only. PSR J0955−6150 has a good upper limit on its very small proper motion (<0.4 mas yr−1). We used pulsars with accurate parallaxes to study the MSP velocities. This yields 39 MSP transverse velocities, and combined with MSPs in the literature (excluding those in Globular Clusters) we analyse 66 MSPs in total. We find that MSPs have, on average, much lower velocities than normal pulsars, with a mean transverse velocity of only 78(8) km s−1 (MSPs) compared with 246(21) km s−1 (normal pulsars). We found no statistical differences between the velocity distributions of isolated and binary MSPs. From Galactocentric cylindrical velocities of the MSPs, we derive 3D velocity dispersions of σρ, σϕ, σ z  = 63(11), 48(8), 19(3) km s−1. We measure a mean asymmetric drift with amplitude 38(11) km s−1, consistent with expectation for MSPs, given their velocity dispersions and ages. The MSP velocity distribution is consistent with binary evolution models that predict very few MSPs with velocities >300 km s−1 and a mild anticorrelation of transverse velocity with orbital period. [ABSTRACT FROM AUTHOR]

We report on the serendipitous discovery of 49 H  i -rich galaxies in a 2.3 h Open Time observation with MeerKAT. We present their properties including their H  i masses, intensity and velocity maps, and spectra. We determine that at least three H  i -rich galaxy groups have been detected, potentially as part of a supergroup. Some members of these galaxy groups show clear interaction with each other in their H  i emission. We cross-match the detections with PanSTARRS, Wide-field Infrared Survey Explorer , and Galaxy Evolution Explorer , and obtain stellar masses and star formation rates. One source is found to be a potential OH megamaser, but further follow-up is required to confidently determine this. For six sources with sufficient spatial resolution in H  i , we produce rotation curves with BBarolo, generate mass models, and derive a dark matter halo mass. While the number of galaxies detected in this relatively short pointing appears to be at the high end of expectations compared to other MeerKAT observations and group H  i mass function studies, this finding highlights the capability of MeerKAT for other serendipitous discoveries, and the potential for many more H  i -rich galaxies to be revealed within both existing and upcoming Open Time data sets. [ABSTRACT FROM AUTHOR]

We present new radio continuum images and a source catalogue from the MeerKAT survey in the direction of the Small Magellanic Cloud. The observations, at a central frequency of 1.3 GHz across a bandwidth of 0.8 GHz, encompass a field of view ∼7° × 7° and result in images with resolution of 8 arcsec. The median broad-band Stokes I image Root Mean Squared noise value is ∼11  μ Jy beam−1. The catalogue produced from these images contains 108 330 point sources and 517 compact extended sources. We also describe a UHF (544–1088 MHz) single pointing observation. We report the detection of a new confirmed Supernova Remnant (SNR; MCSNR J0100–7211) with an X-ray magnetar at its centre and 10 new SNR candidates. This is in addition to the detection of 21 previously confirmed SNRs and two previously noted SNR candidates. Our new SNR candidates have typical surface brightness an order of magnitude below those previously known, and on the whole they are larger. The high sensitivity of the MeerKAT survey also enabled us to detect the bright end of the SMC Planetary Nebulae (PNe) sample – point-like radio emission is associated with 38 of 102 optically known PNe, of which 19 are new detections. Lastly, we present the detection of three foreground radio stars amidst 11 circularly polarized sources, and a few examples of morphologically interesting background radio galaxies from which the radio ring galaxy ESO 029–G034 may represent a new type of radio object. [ABSTRACT FROM AUTHOR]

We present the results of a polarimetric study from our new high-sensitivity L -band (0.8–1.7 GHz) observation of Pictor A using the MeerKAT radio telescope. We confirm the presence of the radio jet extending from the nucleus to the western hotspot of this source. Additionally, we show the radio emission expected to coincide with previously observed X-ray emission in the radio lobes, confirming that the emission mechanism is of inverse Compton origin, as suggested by a previous study. Our spectropolarimetric analysis using the rotation measure synthesis technique reveals a relatively uniform mean rotation measure distribution across the lobes of Pictor A, with most lines of sight exhibiting single-peaked Faraday spectra. However, a number of the lines of sight exhibit single peaked spectra with a wide base or multiple peaks, suggesting the presence of multiple Faraday components or a Faraday thick structure along Pictor A's lines of sight. We also confirm the asymmetry in rotation measure variability and depolarization between the two lobes of this source, as reported in a previous study. [ABSTRACT FROM AUTHOR]

A number of pulsars are known to have profile evolution on time-scales of months, often correlated with spin-down rate changes. Here, we present the first result from 3 yr of monitoring observations from MeerKAT as part of the Thousand Pulsar Array programme. This programme obtains high-fidelity pulse profiles for ∼ 500 pulsars, which enabled the detection of subtle changes in seven sources not previously known to exhibit long-term profile evolution. A 2D Gaussian convolution is used to highlight correlated emission variability in both the pulse phase and observing epoch direction. Simulations show that for one additional source the observed profile variability is likely to originate from stochastic single-pulse shape variability (jitter). We find that it is common for long-term profile variability to be associated with changes in polarization fractions, but not with polarization position angle (PA) changes. PA changes are expected if emission height changes or precession is responsible for the profile variability. PSR J1741−3927 is the only pulsar in our sample that shows correlated PA variability, and this is associated with orthogonal polarization mode activity. For the six other pulsars limits on possible emission height changes and impact angle changes are derived. These limits are consistent with the small changes in the total intensity profile shape. None of the sources show detectable spin-down variability correlated with the emission changes, which are thought to be driven by magnetospheric current fluctuations. Therefore, the absence of correlated spin-down rate variability allows upper limits to be placed on changes in the magnetospheric charge density. [ABSTRACT FROM AUTHOR]

Transient surveys are a vital tool in exploring the dynamic Universe, with radio transients acting as beacons for explosive and highly energetic astrophysical phenomena. However, performing commensal transient surveys using radio imaging can require a significant amount of computing power, data storage, and time. With the instrumentation available to us, and with new and exciting radio interferometers in development, it is essential that we develop efficient methods to probe the radio transient sky. In this paper, we present results from a commensal short-duration transient survey, on time-scales of 8 s, 128 s, and 1 h, using data from the MeerKAT radio telescope. The data set used was obtained as part of a galaxy observing campaign, and we focus on the field of NGC 5068. We present a quick, wide-field imaging strategy to enable fast imaging of large data sets, and develop methods to efficiently filter detected transient candidates. No transient candidates were identified on the time-scales of 8 s, 128 s, and 1 h, leading to competitive limits on the transient surface densities of |$6.7\, {\times }\, 10^{-5}$|⁠ , |$1.1\, {\times }\, 10^{-3}$|⁠ , and |$3.2\, {\times }\, 10^{-2}$| deg−1 at sensitivities of 56.4, 19.2, and 3.9 mJy following primary beam correction for the respective time-scales. We find one possible candidate that could be associated with a stellar flare, which was rejected due to strict image quality control. Further short time-scale radio observations of this candidate could give definite results about its origin. [ABSTRACT FROM AUTHOR]

We report on a radiopolarimetric observation of the Saturn–Jupiter Great Conjunction of 2020 using the MeerKAT L -band system, initially carried out for science verification purposes, which yielded a serendipitous discovery of a pulsar. The radiation belts of Jupiter are very bright and time variable: coupled with the sensitivity of MeerKAT, this necessitated development of dynamic imaging techniques, reported on in this work. We present a deep radio 'movie' revealing Jupiter's rotating magnetosphere, a radio detection of Callisto, and numerous background radio galaxies. We also detect a bright radio transient in close vicinity to Saturn, lasting approximately 45 min. Follow-up deep imaging observations confirmed this as a faint compact variable radio source, and yielded detections of pulsed emission by the commensal MeerTRAP search engine, establishing the object's nature as a radio emitting neutron star, designated PSR J2009−2026. A further observation combining deep imaging with the PTUSE pulsar backend measured detailed dynamic spectra for the object. While qualitatively consistent with scintillation, the magnitude of the magnification events and the characteristic time–scales are odd. We are tentatively designating this object a pulsar with anomalous refraction recurring on odd time-scales (PARROT). As part of this investigation, we present a pipeline for detection of variable sources in imaging data, with dynamic spectra and light curves as the products, and compare dynamic spectra obtained from visibility data with those yielded by PTUSE. We discuss MeerKAT's capabilities and prospects for detecting more of such transients and variables. [ABSTRACT FROM AUTHOR]

This paper presents the first H  i results extracted from the South African Radio Astronomy Observatory (SARAO) MeerKAT Galactic Plane Survey (SMGPS) – a narrow strip (Δ b ∼ 3°) along the southern Milky Way. The primary goal consisted in tracing the great attractor (GA) wall across the innermost zone of avoidance. We reduced a segment spanning the longitude range 302° ≤ ℓ ≤ 332° for the redshift range z ≤ 0.08. The superb SMGPS sensitivity (rms = 0.3–0.5 mJy beam−1 per 44 km s−1 channel) and angular resolution (∼31″ × 26″) lead to a detection limit of log(M H  i /M⊙) ≥ 8.5 at the GA distance (⁠|$\mbox{$V_{\rm {hel}}$}\, \sim 3500{\!-\!}6500$|  km s−1). A total of 477 galaxy candidates were identified over the full redshift range. A comparison of the few H  i detections with counterparts in the literature (mostly HIZOA) found the H  i fluxes and other H  i parameters to be highly consistent. The continuation of the GA wall is confirmed through a prominent overdensity of N  = 214 detections in the GA distance range. At higher latitudes, the wall moves to higher redshifts, supportive of a possible link with the Ophiuchus cluster located behind the Galactic Bulge. This deep interferometric H  i survey demonstrates the power of the SMGPS in improving our insight of large-scale structures at these extremely low latitudes, despite the high obscuration and continuum background. [ABSTRACT FROM AUTHOR]

There has been a recent resurgence in hydroxyl (OH) megamaser research driven by Square Kilometre Array (SKA) precursor/pathfinder telescopes. This will continue in the lead-up to the SKA mid-frequency array, which will greatly expand our view of OH megamasers and their cosmic evolution over ≳80 per cent of the age of the Universe. This is expected to yield large scientific returns as OH megamasers trace galaxy mergers, extreme star formation, high molecular gas densities, and potentially binary/dual supermassive black hole systems. In this paper, we predict the distortion to the OH luminosity function that a magnification bias will inflict, and in turn, predict the distortion on the OH megamaser number counts as a function of redshift. We identify spectral flux density thresholds that will enable efficient lensed OH megamaser selection in large spectral line surveys with MeerKAT and SKA. The surface density of lensed galaxies that could be discovered in this way is a strong function of the redshift evolution of the OH megamaser luminosity function, with predictions as high as ∼1 lensed OH source per square degree at high redshifts (z ≳ 1) for anticipated SKA spectral line survey designs. This could enable efficient selection of some of the most highly obscured galaxies in the Universe. This high-redshift selection efficiency, in combination with the large survey speed of the SKA at ≲1 GHz frequencies and the high magnifications possible with compact OH emission regions (μOH ≫ 10), will enable a transformational view of OH in the Universe. [ABSTRACT FROM AUTHOR]

The Local Void is one of the nearest large voids, located at a distance of 23 Mpc. It lies largely behind the Galactic Bulge and is therefore extremely difficult to observe. We use H  i 21 cm emission observations from the SARAO MeerKAT Galactic Plane Survey (SMGPS) to study the Local Void and its surroundings over the Galactic longitude range 329° < ℓ < 55°, Galactic latitude | b | < 1.5°, and redshift cz < 7500 |$\rm km \, s^{-1}$|⁠. We have detected 291 galaxies to median rms sensitivity of 0.44 mJy per beam per 44 |$\rm km \, s^{-1}$| channel. We find 17 galaxies deep inside the Void, 96 at the border of the Void, while the remaining 178 galaxies are in average density environments. The extent of the Void is ∼58 Mpc. It is severely underdense for the longitude range 350° < ℓ < 35° up to redshift z < 4500 |$\rm km \, s^{-1}$|⁠. The galaxies in the Void tend to have H  i masses that are lower (by approximately 0.25 dex) than their average density counterparts. We find several potential candidates for small groups of galaxies, of which two groups (with 3 members and 5 members) in the Void show signs of filamentary substructure within the Void. [ABSTRACT FROM AUTHOR]

AbstractBackground Meerkats (Suricata suricatta) are endemic carnivores of southern Africa and, although currently listed as ‘least concern’ by the International Union for Conservation of Nature (IUCN) red list, there is evidence of a significant decrease in wild populations mainly attributed to effects of climate change. Little is known about diseases associated with mortality in captive meerkats.Aim To characterise macroscopic and microscopic lesions that accounted for the death or euthanasia in a series of captive meerkats.Material and methods Eight captive meerkats submitted for post-mortem examination between 2018 and 2022.Results Three animals died unexpectedly without clinical signs, 2 exhibited neurological signs, 2 collapsed after con-specific fighting and 1 showed gastrointestinal signs. Common pathological findings of this study that may be related to the death of captive meerkats included foreign bodies (trichobezoars or plastic materials) within the alimentary tract, traumatic penetrating injuries or starvation associated with abnormal social behaviours (bullying and con-specific attacks), verminous pneumonia and systemic atherosclerosis. Common incidental findings included pulmonary edema and congestion, cholesterol granulomas, pulmonary adenomas and vertebral spondylosis.Conclusions Non-infectious diseases outreach infectious diseases as causes of mortality in captive meerkats including, foreign bodies within the alimentary tract, con-specific attacks and systemic atherosclerosis, which is described for the first time. These data should raise concern about appropriate husbandry (e.g. environmental enrichment, cleaning of facilities and diet formulation) by zookeepers and emphasise the need for further study of meerkat mortality in both captive and wild populations.

The double pulsar system, PSR J0737−3039A/B, consists of two neutron stars bound together in a highly relativistic orbit that is viewed nearly edge-on from the Earth. This alignment results in brief radio eclipses of the fast-rotating pulsar A when it passes behind the toroidal magnetosphere of the slow-rotating pulsar B. The morphology of these eclipses is strongly dependent on the geometric orientation and rotation phase of pulsar B, and their time evolution can be used to constrain the geodetic precession rate of the pulsar. We demonstrate a Bayesian inference framework for modelling high-sensitivity eclipse light curves obtained with MeerKAT between 2019 and 2023. Using a hierarchical inference approach, we obtained a precession rate of ΩSOB = 5.16°−0.34°+0.32° yr−1 (68% confidence intervals) for pulsar B, consistent with predictions from general relativity to a relative uncertainty of 6.5%. This updated measurement provides a 6.1% test of relativistic spin-orbit coupling in the strong-field regime. We show that a simultaneous fit to all of our observed eclipses can in principle return a ∼1.5% test of spin-orbit coupling. However, systematic effects introduced by the current geometric orientation of pulsar B along with inconsistencies between the observed and predicted eclipse light curves result in difficult to quantify uncertainties when using this approach. Assuming the validity of general relativity, we definitively show that the spin axis of pulsar B is misaligned from the total angular momentum vector by 40.6° ±0.1° and that the orbit of the system is inclined by approximately 90.5° from the direction of our line of sight. Our measured geometry for pulsar B suggests the largely empty emission cone contains an elongated horseshoe-shaped beam centred on the magnetic axis, and that it may not be re-detected as a radio pulsar until early 2035. [ABSTRACT FROM AUTHOR]

We present the first sub-arcsecond localized Fast Radio Burst (FRB) detected using MeerKAT. FRB 20210405I was detected in the incoherent beam using the MeerTRAP pipeline on 2021 April 05 with a signal to noise ratio of 140.8 and a dispersion measure of 565.17 pc cm−3. It was detected while MeerTRAP was observing commensally with the ThunderKAT large survey project, and was sufficiently bright that we could use the ThunderKAT 8 s images to localize the FRB. Two different models of the dispersion measure in the Milky Way and halo suggest that the source is either right at the edge of the Galaxy, or outside. This highlights the uncertainty in the Milky Way dispersion measure models, particularly in the Galactic Plane, and the uncertainty of Milky Way halo models. Further investigation and modelling of these uncertainties will be facilitated by future detections and localizations of nearby FRBs. We use the combined localization, dispersion measure, scattering, specific luminosity, and chance coincidence probability information to find that the origin is most likely extra-galactic and identify the likely host galaxy of the FRB: 2MASS J1701249−4932475. Using SALT spectroscopy and archival observations of the field, we find that the host is a disc/spiral galaxy at a redshift of z = 0.066. [ABSTRACT FROM AUTHOR]

The point-spread function (PSF) is a fundamental property of any astronomical instrument. In interferometers, differing array configurations combined with their uv coverage, and various weighting schemes can produce an irregular but deterministic PSF. As a result, the PSF is often deconvolved using CLEAN-style algorithms to improve image fidelity. In this paper, we revisit a significant effect that causes the flux densities measured with any interferometer to be systematically offset from the true values. Using a suite of carefully controlled simulations, we show that the systematic offset originates from a mismatch in the units of the image produced by these CLEAN-style algorithms. We illustrate that this systematic error can be significant, ranging from a few to tens of per cent. Accounting for this effect is important for current and future interferometric arrays, such as MeerKAT, LOFAR, and the SKA, whose core-dominated configuration naturally causes an irregular PSF. We show that this offset is independent of other systematics, and can worsen due to some factors such as the goodness of the fit to the PSF, the deconvolution depth, and the signal-to-noise ratio of the source. Finally, we present several methods that can reduce this effect to just a few per cent. [ABSTRACT FROM AUTHOR]

We present a flux density study of 89 millisecond pulsars (MSPs) regularly monitored as part of the MeerKAT Pulsar Timing Array (MPTA) using the L -Band receiver with an approximately two week cadence between 2019 and 2022. For each pulsar, we have determined the mean flux densities at each epoch in eight ∼97 MHz sub-bands ranging from 944 to 1625 MHz. From these we have derived their modulation indices, their average and peak-to-median flux densities in each sub-band, as well as their mean spectral indices across the entire frequency range. We find that the vast majority of the MSPs have spectra that are well described by a simple power law, with a mean spectral index of –1.86(6). Using the temporal variation of the flux densities, we measured the structure functions and determined the refractive scintillation time-scale for seven. The structure functions provide strong evidence that the intrinsic radio luminosities of MSPs are stable. As a population, the average modulation index at 20 cm wavelengths peaks near unity at dispersion measures (DMs) of ∼20 pc cm−3 and by a DM of 100 pc cm−3 are closer to 0.2, due to refractive scintillation. We find that timing arrays can improve their observing efficiency by reacting to scintillation maxima, and that 20 cm FRB surveys should prioritize highly scintillating mid-latitude regions of the Galactic sky where they will find ∼30 per cent more events and bursts at greater distances. [ABSTRACT FROM AUTHOR]

As more Fast Radio Bursts (FRBs) are being localized, we are learning that some fraction have persistent radio sources (PRSs). Such a discovery motivates an improvement in our understanding of the nature of those counterparts, the relation to the bursts themselves and why only some FRBs have PRSs. We report on observations made of FRB 20121102A with the MeerKAT radio telescope. Across five epochs, we detect the PRS associated with FRB 20121102A. Our observations are split into a cluster of four epochs (MJD 58732–58764) and a separate single epoch about 1000 d later. The measured flux density is constant across the first four observations but then decays by more than one-third in the final observation. Our observations on MJD 58736 coincided with the detections of 11 bursts from FRB 20121102A by the MeerTRAP backend, seven of which we detected in the image plane. We discuss the importance of image plane detections when considering the commensal transient searches being performed with MeerKAT and other radio facilities. We find that MeerKAT is so sensitive that within a 2-s image, we can detect any FRB with a flux density above 2.4 mJy at 1.3 GHz and so could localize every FRB that has been detected by CHIME to date. [ABSTRACT FROM AUTHOR]

In many social species, both the acquisition of dominance and the duration that individuals maintain their status are important determinants of breeding tenure and lifetime reproductive success. However, few studies have yet examined the extent and causes of variation in dominance tenure and the duration of breeding lifespans. Here, we investigate the processes that terminate dominance tenures and examine how they differ between the sexes in wild Kalahari meerkats (Suricata suricatta), a cooperative breeder where a dominant breeding pair produces most of the young recruited into each group. Mortality and displacement by resident subordinate competitors were important forms of dominance loss for both sexes. However, dominant males (but rarely females) were also at risk of takeovers by extra-group invading males. Dominant males also differed from dominant females in that they abandoned their group after the death of their breeding partner, when no other breeding opportunities were present, whereas dominant females that lost their partner remained and continued to breed in the same group. We show that a larger number of processes can terminate dominance tenure in males with the result that the average male tenure of breeding positions was shorter than that of females, which contributes to the reduced variance in the lifetime reproductive success in males compared to females. Our analysis suggests that sex differences in emigration and immigration may often have downstream consequences for sex differences in reproductive variance and for the selection pressures operating on females and males. [ABSTRACT FROM AUTHOR]