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We present a qualitative comparison between the host and black hole properties of radio galaxies in the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey with the radio galaxy population in the simba suite of cosmological hydrodynamical simulations. The MIGHTEE data include a |$\sim$| 1 deg |$^{2}$| pointing of the COSMOS field observed at 1.28 GHz with the MeerKAT radio telescope and cross-matched with multiwavelength counterparts to provide classifications of high- and low-excitation radio galaxies (HERGs and LERGs) along with their corresponding host properties. We compare the properties of the MIGHTEE HERGs and LERGs with that predicted by the simba simulations where HERGs and LERGs are defined as radio galaxies dominated by cold or hot mode accretion, respectively. We consider stellar masses |$\,\,{M}_{*}$|⁠ , star formation rates SFR, AGN bolometric luminosity |$L_{\rm bol}$|⁠ , and Eddington fraction |$f_{\rm Edd}$|⁠ , as a function of 1.4 GHz radio luminosity and redshift. In both MIGHTEE and simba , the properties of HERGs and LERGs are similar across all properties apart from SFRs due to differences in host cold gas content in simba. We predict a population of HERGs with low |$f_{\rm Edd}$| in simba that are confirmed in the MIGHTEE observations and tied to the faint population at low z. The predictions from simba with the MIGHTEE observations describe a regime where our understanding of the radio galaxy dichotomy breaks down, challenging our understanding of the role of AGN accretion and feedback in the faint population of radio galaxies. [ABSTRACT FROM AUTHOR]

S-shaped radio galaxy jets are prime sources for investigating the dynamic interplay between the central active galactic nucleus (AGN), the jets, and the ambient intergalactic medium. These sources are excellent candidates for studying jet precession, as their S-shaped inversion symmetry strongly indicates underlying precession. We present a multiwavelength analysis of the giant inversion-symmetric S-shaped radio galaxy PKS 2300 |$-$| 18, which spans 0.76 Mpc. The host is a quasar at a redshift of 0.128, displaying disturbed optical morphology due to an ongoing merger with a companion galaxy. We conducted a broad-band radio spectral study using multifrequency data ranging from 183 MHz to 6 GHz, incorporating dedicated observations with the upgraded Giant Metrewave Radio Telescope (uGMRT) and Karl G. Jansky Very Large Array (JVLA) alongside archival radio data. A particle injection model was fitted to the spectra of different regions of the source to perform ageing analysis, which was supplemented with a kinematic jet precession model. The ageing analysis revealed a maximum plasma age of |$\sim$| 40 Myr, while the jet precession model indicated a precession period of |$\sim$| 12 Myr. ROentgen SATellite (ROSAT) data revealed an X-ray halo of Mpc size, and from Chandra the AGN X-ray spectrum was modelled using thermal and power-law components. The optical spectrum displaying double-peaked broad emission lines was modelled, indicating complex broad-line region kinematics at the centre with the possibility of a binary SMBH. We present the results of our multiwavelength analysis of the source, spanning scales from a few light-days to a few Mpc, and discuss its potential evolutionary path. [ABSTRACT FROM AUTHOR]

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]

Diffuse radio sources known as radio relics are direct tracers of shocks in the outskirts of merging galaxy clusters. PSZ2 G200.95–28.16, a low-mass merging cluster (M 500 = (2.7 ± 0.2) × 1014 M ⊙), features a prominent radio relic, first identified by R. Kale et al. We name this relic as the Seahorse. The MeerKAT Galaxy Cluster Legacy Survey has confirmed two additional radio relics, R2 and R3, in this cluster. We present new observations of this cluster with the upgraded Giant Metrewave Radio Telescope (uGMRT) at 400 and 650 MHz, paired with Chandra X-ray data. The largest linear sizes for the three relics are 1.53 Mpc, 1.12 kpc, and 340 kpc. All three radio relics are polarized at 1283 MHz. Assuming the diffusive shock acceleration model, the spectral indices of the relics imply shock Mach Numbers of 3.1 ± 0.8 and 2.8 ± 0.9 for the Seahorse and R2, respectively. The Chandra X-ray surface brightness map shows two prominent subclusters, but the relics are not perpendicular to the likely merger axis, as typically observed; no shocks are detected at the locations of the relics. We discuss possible merger scenarios in light of the low mass of the cluster and the radio and X-ray properties of the relics. The relic R2 follows the correlation known in the radio relic power and cluster-mass plane, but the Seahorse and R3 relics are outliers. We have also discovered a radio ring in our 650 MHz uGMRT image that could be an Odd Radio Circle candidate. [ABSTRACT FROM AUTHOR]

We present multifrequency radio data for a sample of Narrow-Line type 1 Seyfert (NLS1) galaxies. We first focus on the sub-class of gamma-ray emitting NLS1 galaxies, studying the long-term radio variability of five sources and comparing it to their gamma-ray state. We then extend the observations of the southern NLS1 galaxy sample of Chen et al. by observing several candidate NLS1 sources for the first time, and re-observing several other gamma-ray-quiet sources to obtain a first indication of their radio variability. We find that the gamma-ray emitting NLS1 galaxies are highly variable radio emitters and that there are instances of contemporaneous flaring activity between the radio and gamma-ray bands (PKS 0440 |$-$| 00, PMN J0948+0022, and PKS 1244 |$-$| 255). However, there are also cases of significant radio outbursts without gamma-ray counterparts (PMN J0948+0022 and PKS 2004 |$-$| 447). The five gamma-ray NLS1s favour flat or inverted radio spectra, although the spectral indices vary significantly over time. For the gamma-ray-quiet sample, the difference between the previous observations at 5.5 GHz and new Australia Telescope Compact Array (ATCA) observations indicates that over half of the 14 sources exhibit apparent variability. In contrast to gamma-ray-loud sources, gamma-ray-quiet objects tend to have steep spectra, especially in the lower radio band (887.5–1367.5 MHz) of Australian Square Kilometre Array Pathfinder (ASKAP) data, with a number of the variable sources having flatter spectra at higher radio frequencies. [ABSTRACT FROM AUTHOR]

Some active galactic nuclei (AGN) host outflows which have the potential to alter the host galaxy's evolution (AGN feedback). These outflows have been linked to enhanced radio emission. Here, we investigate the connection between low-frequency radio emission using the international LOw Frequency ARray (LOFAR) telescope and [O  iii ] |$\lambda$| 5007 ionized gas outflows using the Sloan Digital Sky Survey. Using the LOFAR Two-metre Sky Survey (LoTSS) Deep Fields, we select 198 AGN with optical spectra, 115 of which are detected at 144 MHz, and investigate their low-frequency radio emission properties. The majority of our sample do not show a radio excess when considering radio luminosity – star formation rate relationship, and are therefore not driven by powerful jets. We extract the [O  iii ] |$\lambda$| 5007 kinematics and remove AGN luminosity dependencies by matching the radio detected and non-detected AGN in |$L_{\mathrm{6\, \mu m}}$| and redshift. Using both spectral fitting and |$W_{80}$| measurements, we find radio detected AGN have a higher outflow rate (67.2 |$\pm$| 3.4 per cent) than the radio non-detected AGN (44.6 |$\pm$| 2.7 per cent), indicating a connection between ionized outflows and the presence of radio emission. For spectra where there are two components of the [O  iii ] emission line present, we normalize all spectra by the narrow component and find that the average broad component in radio detected AGN is enhanced compared to the radio non-detected AGN. This could be a sign of higher gas content, which is suggestive of a spatial relationship between [O  iii ] outflows and radio emission in the form of either low-powered jets or shocks from AGN winds. [ABSTRACT FROM AUTHOR]

Both star formation (SF) and active galactic nuclei (AGNs) play an important role in galaxy evolution. Statistically quantifying their relative importance can be done using radio luminosity functions (RLFs). Until now these relied on galaxy classifications, where sources with a mixture of radio emission from SF and AGN are labelled as either a star-forming galaxy or an AGN. This can cause the misestimation of the relevance of AGN. Brightness temperature measurements at 144 MHz with the International LOw Frequency ARray telescope can separate radio emission from AGN and SF. We use the combination of sub-arcsec and arcsec resolution imaging of 7497 sources in the Lockman Hole and ELAIS-N1 fields to identify AGN components in the sub-arcsec resolution images and subtract them from the total flux density, leaving flux density from SF only. We construct, for the first time, RLFs by physical process, either SF or AGN activity, revealing a hidden AGN population at |$L_{\textrm {144 MHz}}$| |$\lt 10^{24}$| W Hz |$^{-1}$|⁠. This population is 1.56 |$\pm$| 0.06 more than expected for |$0.5\lt z\lt 2.0$| when comparing to RLFs by galaxy classification. The star-forming population has only 0.90 |$\pm$| 0.02 of the expected SF. These 'hidden' AGNs can have significant implications for the cosmic SF rate and kinetic luminosity densities. [ABSTRACT FROM AUTHOR]

We present and discuss two catalogues of ultraviolet (UV)-selected (near-UV (NUV) |$\lt 22.8$|  mag) galaxies that lie within a 200 deg |$^2$| area of sky covered by the ASKAP First Large Absorption Survey in H  i (FLASH) and have an impact parameter of less than 20 arcsec to a FLASH radio continuum source. These catalogues are designed to enable a future search for 21 cm H  i  absorption in and around star-forming galaxies at redshift |$0.4\lt z\lt 1$|⁠. We outline the production of this UV-bright data set, which has optical spectroscopy from the WiggleZ and Sloan Digital Sky Survey (SDSS) surveys and a median redshift of |${\sim} 0.6$|⁠. Analysis of the optical spectra, using multiple diagnostic diagrams, shows that galaxies with an impact parameter of less than 5 arcsec are likely to be physically associated with the radio source and are five times more likely to be an active galactic nucleus than objects without a radio match. Conversely, objects with impact factors between 5 and 20 arcsec are largely (> 80 per cent) star-forming and resemble the overall WiggleZ population. The (⁠|$g - i$|⁠) colour evolution with redshift is consistent with a history of active star formation, but the radio-associated objects are typically redder and have colours similar to high-excitation radio galaxies. The redshift distribution of the two catalogues matches the overall distribution for WiggleZ galaxies, despite their otherwise rare radio properties. These catalogues can be expanded in future as new radio data become available, and a forthcoming paper will present the H  i  absorption results. [ABSTRACT FROM AUTHOR]

We characterize the co-evolution of radio-loud active galactic nuclei (AGN) and their galaxies by mapping the dependence of radio-loud AGN activity on stellar mass and star formation rate (SFR) across cosmic time (out to |$z \sim 1.5$|⁠). Deep LOFAR radio observations are combined with large galaxy samples to study the incidence of radio-loud AGN across the galaxy population; the AGN are further split into low-excitation radio galaxies (LERGs) and high-excitation radio galaxies (HERGs). We find that LERG activity occurs over a wide range of SFRs, whereas HERGs are typically found in galaxies with ongoing star formation. The LERGs are then split based on their SFRs relative to the main sequence, across redshift. Within quiescent galaxies, LERG activity shows a steep stellar mass dependence with the same normalization across the past |$\sim$| 10 Gyr; this indicates that hot gas fuels LERGs in quiescent galaxies across cosmic time. In massive galaxies [ |$\log _{10}(M/\rm {{\rm M}_{\odot }}) \gtrsim 11$| ], the incidence of LERGs is roughly constant across the galaxy population, suggesting that LERGs in massive galaxies may be fuelled by hot gas regardless of the star formation activity. At lower masses, however, LERG activity is significantly more enhanced (by a factor of up to 10) in star-forming galaxies compared to quiescent galaxies; this suggests that an additional fuelling mechanism, likely associated with cold gas, may fuel the LERGs in galaxies with higher SFRs. We find that HERGs typically accrete above 1 per cent of the Eddington-scaled accretion rate, and the LERGs typically accrete below this level. [ABSTRACT FROM AUTHOR]

The coevolution of supermassive black holes and their host galaxies represents a fundamental question in astrophysics. One approach to investigating this question involves comparing the star formation rates (SFRs) of active galactic nuclei (AGNs) with those of typical star-forming galaxies. At relatively low redshifts (z ≲ 1), radio AGNs manifest diminished SFRs, indicating suppressed star formation, but their behavior at higher redshifts is unclear. To examine this, we leveraged galaxy and radio-AGN data from the well-characterized W-CDF-S, ELAIS-S1, and XMM-LSS fields. We established two mass-complete reference star-forming galaxy samples and two radio-AGN samples, consisting of 1763 and 6766 radio AGNs, the former being higher in purity and the latter more complete. We subsequently computed star-forming fractions (f SF; the fraction of star-forming galaxies to all galaxies) for galaxies and radio-AGN host galaxies and conducted a robust comparison between them up to z ≈ 3. We found that the tendency for radio AGNs to reside in massive galaxies primarily accounts for their low f SF, which also shows a strong negative dependence upon M ⋆ and a strong positive evolution with z. To investigate further the star formation characteristics of those star-forming radio AGNs, we constructed the star-forming main sequence (MS) and investigated the behavior of the position of AGNs relative to the MS at z ≈ 0–3. Our results reveal that radio AGNs display lower SFRs than star-forming galaxies in the low- z and high- M ⋆ regime and, conversely, exhibit comparable or higher SFRs than MS star-forming galaxies at higher redshifts or lower M ⋆. [ABSTRACT FROM AUTHOR]

We conducted the MeerKAT Vela Supercluster survey, named Vela |$-$| |$\textrm {H}\, \scriptstyle \mathrm{I}$|⁠ , to bridge the gap between the Vela SARAO (South African Radio Astronomy Observatory) MeerKAT Galactic Plane Survey (Vela |$-$| SMGPS, |$-2^{\circ } \le b \le 1^{\circ }$|⁠), and optical and near-infrared spectroscopic observations of the Vela Supercluster (hereafter Vela |$-$| OPT/NIR) at |$|b| \gtrsim 7^{\circ }$|⁠. Covering coordinates from |$263^{\circ } \le \ell \le 284^{\circ }$| and |$1^{\circ } \le b \le 6.2^{\circ }$| above, and |$-6.7^{\circ } \le b \le -2^{\circ }$| below the Galactic Plane (GP), we sampled 667 fields spread across an area of |${\sim } \rm 242 ~deg^2$|⁠. With a beam size of |${\sim } 38 \ \mathrm{ arcsec} \times 31 \ \mathrm{ arcsec}$|⁠ , Vela |$-$| |$\textrm {H}\, \scriptstyle \mathrm{I}$| achieved a sensitivity of |$\langle \rm rms \rangle = 0.74$| |$\rm mJy\, beam^{-1}$| at 44.3 |$\rm km\, s^{-1}$| velocity resolution over |${\sim }$| 67 h of observations. We catalogued 719 galaxies, with only 211 (29 per cent) previously documented in the literature, primarily through the H  i Parkes Zone of Avoidance survey (HIZOA), Two Micron All-sky Survey Extended Source Catalog (2MASX), and Wide-field Infrared Survey Explorer (WISE) data bases. Among these known galaxies, only 66 had optical spectroscopic redshift information. We found marginal differences of less than one channel resolution for all galaxies in common between HIZOA and Vela |$-$| SMGPS, and a mean difference of |$70 \pm 15$| |$\rm km\, s^{-1}$| between optical and |$\textrm {H}\, \scriptstyle \mathrm{I}$| velocities. Combining data from Vela |$-$| SMGPS, Vela |$-$| |$\textrm {H}\, \scriptstyle \mathrm{I}$|⁠ , and Vela |$-$| OPT/NIR confirmed the connection of the Hydra/Antlia filament across the GP and revealed a previously unknown diagonal wall at a heliocentric velocity range of |$6500\!\!-\!\!8000$| |$\rm km\, s^{-1}$|⁠. Vela |$-$| |$\textrm {H}\, \scriptstyle \mathrm{I}$| reinforces the connection between the first wall at |$18\,500\!\!-\!\!20\,000$| |$\rm km\, s^{-1}$| and the inner Zone of Avoidance. The second wall seems to traverse the GP at |$270^{\circ } \le \ell \le 279^{\circ }$|⁠ , where it appears that both walls intersect, jointly covering the velocity range |$18\,500\!\!-\!\!21\,500$| |$\rm km\, s^{-1}$|⁠. [ABSTRACT FROM AUTHOR]

The flat spectrum radio quasar PKS 1510-089 is one of the most active blazars in γ -rays, exhibiting phases of very high activity. This study investigates its variability over a decade across a wide range of wavelengths, from radio to γ -rays. Utilizing the nonthermal dominance parameter, we analyze the H β, H γ, and λ 5100 Å continuum light curves to discern the primary source of continuum emission, either from the accretion disk or the jet, during different activity phases. Our findings underscore the dominance of jet emission in the continuum during flare-like events. We observed an approximately 80 day delay between the H β and continuum emissions, which we attribute to the spatial separation between the optical emission zone and the broad-line region. Near-zero delays between optical and near-infrared emissions suggest that the emitting regions within the jet are cospatial. Synchrotron self-Compton was identified as the primary mechanism for γ -ray emission during flares, supported by the minimal delay observed between optical/near-infrared emissions and γ -rays. Additionally, we found a delay of about 60 days between the leading optical/near-infrared emissions and X-rays, indicating that inverse Compton scattering within the jet predominantly drives X-ray emission. However, distinguishing between synchrotron self-Compton and external inverse Compton mechanism was not feasible. Shifts in the spectral index across the 15–230 GHz range corresponded with ejections from the radio core, suggesting changes in the physical conditions of the jet. [ABSTRACT FROM AUTHOR]

We present James Webb Space Telescope MIRI data of the inner ∼3 × 2 kpc2 of the galaxy IC 5063, in which the jets of a supermassive black hole interact with the gaseous disk they are crossing. Jet-driven outflows were known to be initiated along or near the jet path and to modify the stability of molecular clouds, possibly altering their star formation properties. The MIRI data, of unprecedented resolution and sensitivity in the infrared, now reveal that there are more than 10 discrete regions with outflows, nearly doubling the number of such known regions. Outflows exist near the radio lobes, at the nucleus, in a biconical structure perpendicular to the jet, and in a bubble moving against the disk. In some of them, velocities above escape velocity are observed. Stratification is also observed, with higher ionization or excitation gas attaining higher velocities. More outflows and bow shocks, found further away from the nucleus than the radio lobes, in regions without significant radio emission, reveal the existence of past or weak radio jets that interacted with the interstellar medium. The coincidence of the bow shocks with the optical extended emission line region (EELR) suggests that the jets also contributed to the gas ionization. Maps of the H2 gas excitation temperature, T ex, indicate that the molecular gas is most excited in regions with radio emission. There, T ex is >100 K higher than in the EELR interior. We argue that a combination of jet-related shocks and cosmic rays is likely responsible for this excess molecular gas excitation. [ABSTRACT FROM AUTHOR]

We present a study of the multiwavelength (MW) variability of the blazar AO 0235 |$+$| 164 based on the radio-to- |$\gamma$| -ray data covering a long time period from 1997 to 2023. The radio data are represented by the 1–22 GHz measurements from the SAO RAS RATAN-600 radio telescope, the 5 and 8 GHz data from the IAA RAS RT-32 telescopes, and the 37 GHz data from the RT-22 telescope of CrAO RAS. The optical measurements in the R -band were collected with the SAO RAS 1-m Zeiss-1000 and 0.5-m AS-500/2 telescopes. Additionally, we used the archive data at 230 GHz from the Submillimetre Array and the |$\gamma$| -ray data in the 0.1–100 GeV band from the Fermi-LAT point source 4FGL-DR2 catalogue. The variability properties during four epochs containing major flares and one epoch of relatively low activity were analysed using the fractional variability indices, discrete correlation functions, Lomb–Scargle periodograms, and structure functions. A significant correlation (⁠|$\ge \!2\sigma$|⁠) between the radio, optical, and |$\gamma$| -ray bands is found for all these periods with time delays from 0 to 1.7 yr. The relation between time delay and frequency is described by a linear law with a negative slope of |$-10$| d GHz |$^{-1}$|⁠. The discovered properties of MW variability for the low-activity period and for flaring states suggest that the mechanisms dominating the radio– |$\gamma$| -ray variations are not substantially different. The detected quasi-periodic oscillations of about 6 and 2 yr are tentative, as the time span of the observations includes fewer than four full cycles for the radio and optical data and only about three cycles for the Fermi-LAT data. These results should be interpreted with caution, given the limited number of observed cycles and the influence of red noise. We used cluster analysis to reliably separate the high and low-activity states and determined statistical differences in the main properties of AO 0235 |$+$| 164 non-thermal emission. The physical parameters of the radio jet were obtained using the Hedgehog model applied to the average radio spectrum of AO 0235 |$+$| 164 in the range 0.1–300 GHz. The effectiveness of replacing electrons with protons in the synchrotron radio emission of relativistic jets is shown for describing the nature of blazars and the generation of high-energy neutrinos. [ABSTRACT FROM AUTHOR]

We study the stellar, neutral gas content within haloes over a halo mass range |$10^{10} \text{ to } 10^{15.5} \text{M}_\odot$| and hot X-ray gas content over a halo mass range |$10^{12.8} \text{ to } 10^{15.5} \text{M}_\odot$| in the local universe. We combine various empirical data sets of stellar, H  i , and X-ray observations of galaxies, groups, and clusters to establish fundamental baryonic mass versus halo mass scaling relations. These scaling relations are combined with halo mass function to obtain the baryon densities of stars, neutral gas, and hot gas (⁠|$T\gt 10^6 \text{K}$|⁠), as a function of halo mass. We calculate the contributions of the individual baryonic components to the cosmic baryon fraction. Cosmic stellar mass density (⁠|$\Omega _\text{star}=2.09^{+0.21}_{-0.18} \times 10^{-3}$|⁠), cosmic H  i mass density (⁠|$\Omega _\rm{H\,{\small I}}=0.49^{+0.25}_{-0.12} \times 10^{-3}$|⁠), and cosmic neutral gas mass density (⁠|$\Omega _\text{neutral gas}=0.71^{+0.39}_{-0.18} \times 10^{-3}$|⁠) estimates are consistent with previous more direct method measurements of these values, thereby establishing the veracity of our method. We also give an estimate of the cosmic hot plasma density (⁠|$\Omega _\text{hot gas}=2.58^{+2.1}_{-0.66} \times 10^{-3}$|⁠). [ABSTRACT FROM AUTHOR]

Radio galaxies are a subclass of active galactic nuclei that drive relativistic jets from their center and are observed in radio to very-high-energy gamma rays. The emission mechanisms and regions are still unknown. High-energy gamma rays can be explained by the emission from the magnetically arrested disks (MADs) around the central supermassive black hole (BH), for which the magnetic flux threading the BH is in a saturation level, although the emission from the MADs does not explain the optical and X-ray data. We construct a two-zone multiwavelength emission model in which optical and X-rays come from jets, while millimeter/submillimeter and gamma rays come from MADs. Our model takes into account the particle injection by the magnetic reconnection at the jet base close to the BH and particle entrainment from the ambient gas at the jet emission zone. We apply our model to M87 and find that our model can explain the simultaneous multiwavelength data, except for the radio data, which could be explained if we extend our one-zone emission model to a one-dimensional one. We also find that the strong plasma entrainment is necessary to explain the multiwavelength data. Our model will be tested by variability analysis among the multiwavelength data. [ABSTRACT FROM AUTHOR]

We evaluate recent and upcoming low-redshift neutral hydrogen (H  i) surveys as a cosmological probe of small scale structure with a goal of determining the survey criteria necessary to test ultralight axion (ULA) dark matter models. Standard cold dark matter (CDM) models predict a large population of low-mass galactic haloes, whereas ULA models demonstrate significant suppression in this small-scale regime, with halo mass cutoffs of |$10^{12}\, \mathrm{M}_{\odot }$| to |$10^{7}\, \mathrm{M}_{\odot }$| corresponding to ULA masses of |$10^{-24}\,$| to |$10^{-20}\,$|  eV, respectively, if ULAs compose all of the dark matter. We generate random, homogeneously populated mock universes with cosmological parameters adjusted to match CDM and ULA models. We simulate observations of these mock universes with hypothetical analogues of the mass-limited ALFALFA and WALLABY H  i surveys and reconstruct the corresponding H  i mass function (HIMF). We find that the ALFALFA HIMF can test for the presence of ULA DM with |$m_{a}\lesssim 10^{-21.5}~{\rm eV}$|⁠ , while WALLABY could reach the larger window |$m_{a}\lesssim 10^{-20.9}~{\rm eV}$|⁠. These constraints are complementary to other probes of ULA dark matter, demonstrating the utility of local Universe H  i surveys in testing dark matter models. [ABSTRACT FROM AUTHOR]

This paper presents a 610 MHz radio survey covering 1.94 deg |$^2$| around the North Ecliptic Pole (NEP), which includes parts of the |${\it AKARI}$| (ADF-N) and Euclid, Deep Fields North. The median 5 |$\sigma$| sensitivity is 28  |$\mu$| Jy beam |$^{-1}$|⁠ , reaching as low as 19  |$\mu$| Jy beam |$^{-1}$|⁠ , with a synthesized beam of 3.6 arcsec |$\times$| 4.1  arcsec. The catalogue contains 1675 radio components, with 339 grouped into multicomponent sources and 284 'isolated' components likely part of double radio sources. Imaging, cataloguing, and source identification are presented, along with preliminary scientific results. From a non-statistical sub-set of 169 objects with multiwavelength AKARI and other detections, luminous infrared galaxies (LIRGs) represent 66 |${{\ \rm per\ cent}}$| of the sample, ultra-luminous infrared galaxies (ULIRGs) 4 |${{\ \rm per\ cent}}$|⁠ , and sources with L |$_{IR}$| <  10 |$^{11}$|   |$\mathrm{ L}_{\odot }\,$| 30 |${{\ \rm per\ cent}}$|⁠. In total, 56 |${{\ \rm per\ cent}}$| of sources show some AGN presence, though only seven are AGN-dominated. ULIRGs require three times higher AGN contribution to produce high-quality SED fits compared to lower luminosity galaxies, and AGN presence increases with AGN fraction. The PAH mass fraction is not significant, although ULIRGs have about half the PAH strength of lower IR-luminosity galaxies. Higher luminosity galaxies show gas and stellar masses an order of magnitude larger, suggesting higher star formation rates. For LIRGs, AGN presence increases with redshift, indicating that part of the total luminosity could be contributed by AGN activity rather than star formation. Simple cross-matching revealed 13 ROSAT QSOs, 45 X-ray sources, and 61 sub-mm galaxies coincident with GMRT radio sources. [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 the first multifrequency analysis of the candidate ultrasteep spectrum radio halo in the galaxy cluster PLCKESZ G171.94−40.65, using the upgraded Giant Metrewave Radio telescope (400 MHz), and Karl G. Jansky Very Large Array (1–2 GHz) observations. Our radio data have been complemented with archival Chandra X-ray observations to provide a crucial insight into the complex intracluster medium physics, happening at large scales. We detect the radio halo emission to the extent of ∼1.5 Mpc at 400 MHz, significantly larger than previously reported, along with five tailed galaxies in the central region. We also report the discovery of an unknown diffuse source "U," at the cluster periphery, with an extent of 300 kpc. Using the available observations, we have found that the radio spectrum of the halo is well-fitted with a single power law, having a spectral index of −1.36 ± 0.05, indicating that it is not an ultrasteep spectrum radio halo. Our low-resolution (25″) resolved spectral map shows an overall uniform spectral index, with some patches of fluctuations. The X-ray and radio surface brightness are morphologically cospatial, with a slight extension along the northwest–southeast direction, seen in both maps. The radio and X-ray surface brightness indicates strong positive correlations, with sublinear correlation slopes (∼0.71). Multiple tailed galaxies and the radio halo indicate a high dynamical activity at the cluster central region. [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]

The Small and Large Magellanic Clouds are the only galaxies outside our own in which radio pulsars have been discovered to date. The sensitivity of the MeerKAT radio interferometer offers an opportunity to search for a population of more distant extragalactic pulsars. The TRAPUM (TRansients And PUlsars with MeerKAT) collaboration has performed a radio-domain search for pulsars and transients in the dwarf star-forming galaxies Sextans A and B, situated at the edge of the Local Group 1.4 Mpc away. We conducted three 2-h multibeam observations at L band (856–1712 MHz) with the full array of MeerKAT. No pulsars were found down to a radio pseudo-luminosity upper limit of 7.9 |$\pm$| 0.4 Jy kpc |$^{2}$| at 1400 MHz, which is 28 times more sensitive than the previous limit from the Murriyang telescope. This luminosity is 30 per cent greater than that of the brightest known radio pulsar and sets a cut-off on the luminosity distributions of the entire Sextans A and B galaxies for unobscured radio pulsars beamed in our direction. A fast radio burst was detected in one of the Sextans A observations at a dispersion measure (DM) of 737 pc cm |$^{-3}$|⁠. We believe this is a background event not associated with the dwarf galaxy due to its large DM and its signal-to-noise ratio being strongest in the wide-field incoherent beam of MeerKAT. [ABSTRACT FROM AUTHOR]

Context. The appearance of the jets and lobes of some radio galaxies makes it difficult to assign them to a known class of objects. This is often due to the activity of the central engine and/or interactions with the environment, as well as projection effects. Aims. We analyse the radio data for an apparently asymmetric radio source 4C 70.19, which is associated with the giant elliptical galaxy NGC 6048. The source shows distorted radio jets and lobes, one of which bends by 180°. The aim of our study is to explain the nature of the observed distortions. Methods. We used LOFAR, Effelsberg, and VLA radio data in a wide range of frequencies. At high frequencies, we also used radio polarimetry to study the properties of the magnetic fields. Additionally, we made use of optical, infra-red, and X-ray data. Results. Polarisation data suggest shearing of the magnetic fields at points where the jets bend. The low-frequency LOFAR map at 145 MHz, as well as the sensitive single-dish Effelsberg map at 8.35 GHz, reveal previously undetected diffuse emission around the source. The rotation measure (RM) derived from the polarimetric data allowed us to estimate the density of the medium surrounding the source, which agrees with typical densities of the intergalactic medium or the outer parts of insterstellar halos. Conclusions. We propose that the southern jet is bent in the same manner as the northern one, but that it is inclined to the sky plane. Both these bends are likely caused by the orbital motion within the galaxy group, as well as interactions with the intergalactic medium. Our analyses suggest that, despite its complex morphology, 4C 70.19 seems to be intrinsically symmetric with a physical extent of up to 600 kpc, and that the diffuse emission detected in our high-sensitivity maps is related to radio plumes that are expanding behind the source. [ABSTRACT FROM AUTHOR]

Context. Relativistic jets in active galactic nuclei are known for their exceptional energy output, and imaging the synthetic synchrotron emission of numerical jet simulations is essential for a comparison with observed jet polarization emission. Aims. Through the use of 3D hybrid fluid-particle jet simulations (with the PLUTO code), we overcome some of the commonly made assumptions in relativistic magnetohydrodynamic (RMHD) simulations by using non-thermal particle attributes to account for the resulting synchrotron radiation. Polarized radiative transfer and ray-tracing (via the RADMC-3D code) highlight the differences in total intensity maps when (i) the jet is simulated purely with the RMHD approach, (ii) a jet tracer is considered in the RMHD approach, and (iii) a hybrid fluid-particle approach is used. The resulting emission maps were compared to the example of the radio galaxy Centaurus A. Methods. We applied the Lagrangian particle module implemented in the latest version of the PLUTO code. This new module contains a state-of-the-art algorithm for modeling diffusive shock acceleration and for accounting for radiative losses in RMHD jet simulations. The module implements the physical postulates missing in RMHD jet simulations by accounting for a cooled ambient medium and strengthening the central jet emission. Results. We find a distinction between the innermost structure of the jet and the back-flowing material by mimicking the radio emission of the Seyfert II radio galaxy Centaurus A when considering an edge-brightened jet with an underlying purely toroidal magnetic field. We demonstrate the necessity of synchrotron cooling as well as the improvements gained when directly accounting for non-thermal synchrotron radiation via non-thermal particles. [ABSTRACT FROM AUTHOR]

Context. Double-double radio galaxies are characterized by intermittent jet-formation activity. The exact reasons for this behavior are not yet fully understood. Studying these objects and their environment allows us to find common characteristics and compare them with the general population of radio galaxies. 3C 219 is a well-known and thoroughly studied radio galaxy. Among the many explanations for its unusual "partial jet" structure, intermittent activity seems to be the leading one. However, this hypothesis has never been tested using aging analysis. Aims. The aim of this paper is to put constraints on the active galactic nucleus duty cycle and dynamics of radio lobe expansion in 3C 219, in both the inner and outer double. This will provide us with information on the behavior of the central engine and the interaction of the radio lobes with the ambient medium, allowing us to verify whether the structure of 3C 219 is the result of intermittent activity and to search for its possible causes. Methods. We performed a spectral aging analysis of the 3C 219 double-double radio galaxy using archival Karl G. Jansky Very Large Array and Low Frequency Array data. We present detailed spectral age maps and constructed a spectral age profile. We compared ratios of linear sizes and luminosities in individual phases of activity with lobe expansion velocities in the plane of the sky derived from the age profile to infer hot-spot advance velocities through the surrounding medium and the orientation of the jet axes. Results. The galaxy shows a general asymmetry in the distribution of plasma with respect to the inferred jet axis in the original phase of activity, suggesting an influence of the intracluster medium on the formation of the radio structure. The advance speed of hot spots in the outer double is typical of classical FRII sources expanding into an ambient thermal medium, while for the inner double, the lower limit is estimated to be ∼0.28 c. The radio galaxy has experienced a very short quiescent period of no more than 2 Myr, which is ≲7% of its total lifetime. Conclusions. The most plausible explanation for the double-double radio structure in 3C 219 is a rapid jet reorientation along the line of sight, which may be the result of a minor merger. Further study of the 3C 219 inner double is needed. High-resolution maps are required to probe its structure in sufficient detail, while high-frequency observations are necessary to better constrain the durations of the quiescent and restarted phases. [ABSTRACT FROM AUTHOR]

The Square Kilometre Array mid-frequency array will enable high-redshift detections of neutral hydrogen (H i) emission in galaxies, providing important constraints on the evolution of cold gas in galaxies over cosmic time. Strong gravitational lensing will push back the H i emission frontier towards cosmic noon (⁠|$z\sim 2$|⁠), as has been done for all prominent spectral lines in the interstellar medium of galaxies. Chakraborty & Roy report a |$z=1.3$| H i emission detection towards the well-modelled, galaxy-scale gravitational lens, SDSS J0826+5630. We carry out H i source modelling of the system and find that their claimed H i magnification, |$\mu _{\rm H\, {\small I}} = 29 \pm 6$|⁠ , requires an H i disc radius of |$\lesssim\!\! 1.5$| kpc, which implies an implausible mean H i surface mass density in excess of |$\Sigma _{\rm H\, {\small I}} > 2000 \ \rm{ M}_\odot \, \rm{pc}^{-2}$|⁠. This is several orders of magnitude above the highest measured peak values (⁠|$\Sigma _{\rm H\, {\small I}} \sim 10~{\rm M}_\odot \, {\rm pc}^{-2}$|⁠), above which H i is converted into molecular hydrogen. Our re-analysis requires this to be the highest H i mass galaxy known (⁠|$M_{\rm H\, {\small I}} \sim 10^{11} \ \mathrm{ M}_\odot$|⁠), as well as strongly lensed, the latter having a typical probability of the order of 1 in 103–104. We conclude that the claimed detection is spurious. [ABSTRACT FROM AUTHOR]

The high angular resolution and sensitivity of Very Long Baseline Interferometry (VLBI) offer a unique tool to identify and study active galactic nuclei and star-formation activity over cosmic time. However, despite recent technical advances, such as multiple phase centre correlation, VLBI surveys have thus far been limited to either a few well-studied deep-fields or wide-areas to a relatively shallow depth. To enter the era of extensive statistical studies at high angular resolution, a significantly larger area of the sky must be observed to much better sensitivity with VLBI. The Synoptic Wide-field EVN– e -MERLIN Public Survey (SWEEPS) is a proposed commensal observing mode for the EVN and e -MERLIN, where single-target principle investigator-led observations are re-correlated at the position of known radio sources within 12 arcmin of the pointing centre. Here, we demonstrate a proof-of-concept of this methodology by detecting a 5.6 mJy core-jet object at 1.7 GHz that would have otherwise been lost from the parent data set. This is the first object to be recovered as part of the SWEEPS pilot programme, which highlights the potential for increasing sample sizes of VLBI-detected radio sources with commensal observing modes in the near future. [ABSTRACT FROM AUTHOR]

We present the discovery of a new Odd Radio Circle (ORC J0219−0505) in 1.2 GHz radio continuum data from the MIGHTEE survey taken with the MeerKAT telescope. The radio-bright host is a massive elliptical galaxy, which shows extended stellar structure, possibly tidal tails or shells, suggesting recent interactions or mergers. The radio ring has a diameter of 35 arcsec, corresponding to 114 kpc at the host galaxy redshift of |$z_{\rm spec} = 0.196$|⁠. This MIGHTEE ORC is a factor 3–5 smaller than previous ORCs with central elliptical galaxies. The discovery of this MIGHTEE ORC in a deep but relatively small-area radio survey implies that more ORCs will be found in deeper surveys. While the small numbers currently available are insufficient to estimate the flux density distribution, this is consistent with the simplest hypothesis that ORCs have a flux density distribution similar to that of the general population of extragalactic radio sources. [ABSTRACT FROM AUTHOR]

We explore the influence of radio-mode feedback on the properties of the cool circumgalactic medium (CGM). To this end, we assemble a statistical sample of approximately 30,000 radio galaxies with background quasars by combining optical spectroscopic measurements of luminous red galaxies and quasars from the year 1 data set of the Dark Energy Spectroscopic Instrument and radio sources from the LOw-Frequency ARray Two-metre Sky Survey (LoTSS) DR2 catalog and the Very Large Array Sky Survey (VLASS) quick-look catalog. Galaxies with similar optical properties but with no radio counterparts in LoTSS and VLASS are selected as the control group. We measure the cool CGM properties of radio galaxies and their control samples traced by Mg ii absorption lines, including covering fraction, rest equivalent width, and gas kinematics. Our results show no significant difference in the properties of gas around radio galaxies and their control sample, indicating that the operating radio-mode feedback of massive galaxies does not produce detectable effects on the properties of the cool CGM. Finally, we show that the CGM of radio galaxies contains a nonnegligible amount of cool gas with approximately 1010 M ⊙. This abundance can place a stringent constraint on the radio-mode feedback models. [ABSTRACT FROM AUTHOR]

The 3C 220.3 system is a rare case of a foreground narrow-line radio galaxy ("galaxy A," z A = 0.6850) lensing a background submillimeter galaxy (z SMG = 2.221). New spectra from MMT/Binospec confirm that the companion galaxy ("galaxy B") is part of the lensing system with z B = 0.6835. New three-color Hubble Space Telescope (HST) data reveal a full Einstein ring and allow a more precise lens model. The new HST images also reveal extended emission around galaxy A, and the spectra show extended [O ii ] emission with irregular morphology and complex velocity structure. All indications are that the two lensing galaxies are a gravitationally interacting pair. Strong [O ii ] emission from both galaxies A and B suggests current star formation, which could be a consequence of the interaction. This would indicate a younger stellar population than previously assumed and imply smaller stellar masses for the same luminosity. The improved lens model and expanded spectral energy distributions have enabled better stellar mass estimates for the foreground galaxies. The resulting dark matter fractions are ∼0.8, which are higher than previously calculated. Deeper Chandra imaging shows extended X-ray emission but no evidence for an X-ray point source associated with either galaxy. The detection of X-rays from the radio lobes of 3C 220.3 allows an estimate of ∼3 nT for the magnetic fields in the lobes, a factor of ∼3 below the equipartition fields, as is typical for radio galaxies. [ABSTRACT FROM AUTHOR]

We report on the discovery of a dual supermassive black hole system in the radio galaxy J1543−0757, with a projected separation between the two black holes of ∼46 mas. The result is based on recent multifrequency observations using the Very Long Baseline Array and European VLBI Network, which reveal two compact, variable, flat-spectrum, active nuclei within the elliptical host galaxy of J1543−0757. Multiepoch observations from the Very Long Baseline Array also provide constraints on the spectral index and proper motions of all components. The flat spectra of both N and S at both frequencies strongly support the hypothesis that these radio components are associated with two separate, accreting supermassive black holes. The two nuclei appear stationary, while the jets emanating from the weaker of the two nuclei appear to move out and terminate in bright hotspots. The discovery of this system has implications for the number of close dual black holes that might be sources of gravitational radiation. [ABSTRACT FROM AUTHOR]

The MIGHTEE survey utilizes the South African MeerKAT radio telescope to observe four extragalactic deep fields, with the aim of advancing our understanding of the formation and evolution of galaxies across cosmic time. MIGHTEE's frequency coverage encompasses the |$\textrm {H}\scriptstyle \mathrm{I}$|  line to a redshift of z |$\simeq$|  0.58, and OH megamasers to z |$\simeq$|  0.9. We present the MIGHTEE- |$\textrm {H}\scriptstyle \mathrm{I}$|  imaging products for the COSMOS field, using a total of 94.2 h on-target and a close-packed mosaic of 15 individual pointings. The spectral imaging covers two broad, relatively interference-free regions (960–1150 and 1290–1520 MHz) within MeerKAT's L -band, with up to 26 kHz spectral resolution (5.5 km s |$^{-1}$| at z  = 0). The median noise in the highest spectral resolution data is 74 μ Jy beam |$^{-1}$|⁠ , corresponding to a 5 |$\sigma$| |$\textrm {H}\scriptstyle \mathrm{I}$|  mass limit of 10 |$^{8.5}$|  M |$_{\odot }$| for a 300 km s |$^{-1}$| line at z  = 0.07. The mosaics cover |$\gt $| 4 deg |$^{2}$|⁠ , provided at multiple angular resolution / sensitivity pairings, with an angular resolution for |$\textrm {H}\scriptstyle \mathrm{I}$|  at z  = 0 of 12 arcsec. We describe the spectral line processing workflow that will be the basis for future MIGHTEE- |$\textrm {H}\scriptstyle \mathrm{I}$|  products, and validation of, and some early results from, the spectral imaging of the COSMOS field. We find no evidence for line emission at the position of the z  = 0.376 |$\textrm {H}\scriptstyle \mathrm{I}$|  line reported from the CHILES survey at a |$\gt $| 94 per cent confidence level, placing a 3 |$\sigma$| upper limit of 8.1 |$\times$|  10 |$^{9}$|  M |$_{\odot }$| on |$M_{\mathrm{HI}}$| for this galaxy. A public data release accompanies this article. [ABSTRACT FROM AUTHOR]

We present a deep H  i survey at L band conducted with the Five-hundred-metre Aperture Spherical radio Telescope (FAST) over the COSMOS field. This survey is strategically designed to overlap with the MIGHTEE COSMOS field, aiming to combine the sensitivity of the FAST and high-resolution of the MeerKAT. We observed the field with FAST for approximately 11 hours covering |${\sim} 2$| square degrees, and reduced the raw data to H  i spectral cubes over the frequency range 1310–1420 MHz. The FAST-H  i data reach a median 3 |$\sigma$| column density of |$N_{\rm {H\,{{\small I}}}} \sim 2\times 10^{17}$|  cm |$^{-2}$| over a |${\sim} 5\, {\rm km}\, {\rm s}^{-1}$| channel width, allowing for studies of the distribution of H  i gas in various environments, such as in galaxies, the Circum-Galactic Medium (CGM) and Intergalactic Medium (IGM). We visually searched the spectral cubes for H  i sources, and found a total of 80 H  i detections, of which 56 have been cross-matched with the MIGHTEE-H  i catalogue. With the cross-matched sources, we compare their H  i masses and find that the total H  i mass fraction in the IGM and CGM surrounding the galaxy pairs is statistically higher than the H  i fraction surrounding the isolated galaxies by a difference of |${\sim} 13\pm 4$| per cent, indicating that the CGM and IGM associated with interacting systems are richer in neutral hydrogen compared to those around isolated galaxies in the local Universe. We also describe several FAST-MeerKAT synergy projects, highlighting the full potential of exploiting both single-dish and interferometric observations to study the distribution and evolution of the diffuse H  i gas. [ABSTRACT FROM AUTHOR]

The origin of X-ray emission from the resolved kiloparsec-scale jets and hotspots of many active galactic nuclei remains uncertain, particularly where the X-ray emission is separate from the radio-optical synchrotron component. Possible explanations include synchrotron emission from a second electron population and external Compton or synchrotron self-Compton processes—alternatives which imply very different physical conditions within the jet. Until recently, X-ray studies of resolved jets and hotspots have been restricted to below ∼10 keV, often showing a hard spectral index indicating a spectral peak beyond this energy range. Here we present NuSTAR observations of the nearby powerful radio galaxy Pictor A, in which we clearly detect the western hotspot at approximately 4′ from the host galaxy, the most significant detection of hotspot emission above 10 keV to date. The NuSTAR spectrum is best fit by a single power law of index Γ = 2.03 ± 0.04; an exponential cutoff gives a 1 σ lower limit on the cutoff energy of 40.7 keV. We confirm previous findings of variations in the soft X-ray flux detected by Chandra over the 2000 to 2015 period, at a significance of 6.5 σ. This rises to >8 σ in the common 3–8 keV band using the combined 22 yr span of Chandra and NuSTAR observations. The variability of the western Pictor A hotspot strongly confirms the previously argued synchrotron nature of the X-ray emission for the hotspot, while the lower bound to the spectral cutoff energy implies electron energies in the hotspot reach up to at least a few TeV. [ABSTRACT FROM AUTHOR]

The unified model of jetted active galactic nuclei (AGNs) based on intrinsic properties presumes that the blazar subtypes of BL Lacertae objects (BLs) and flat-spectrum radio quasars (FSRQs) are aligned equivalents of Fanaroff–Riley type I (FR I) and Fanaroff–Riley type II (FR II) radio galaxies (RGs) from where their parent sources are obtained. Using compiled radio, X-ray and γ -ray data of 397 Fermi Large Area Telescope (Fermi-LAT) blazars and 153 non-Fermi detected RGs, we computed the γ -ray core-dominance parameter (Rγ) and γ -ray emission components (beamed and unbeamed) to study the consequences of relativistic beaming and orientation effects on γ -ray properties of radio RGs, BLs and FSRQs. Data analysis shows that the distributions of RX and Rγ, on average, are consistent with the prediction of the unified scheme in which FSRQs and BLs are strongly beamed and inclined at smaller angles than RGs. Through statistical tests with chance probability, p < 0.05 , we find that the distributions of RX and Rγ for radio galaxies and the blazar subtypes are not significantly different. There is a regular positive trend (r > + 0.60 ) in the variation of radio core-dominance parameter – X-ray luminosity (R − L x ) data from radio galaxies to FSRQs through BLs, which suggests that radio galaxies could be relativistically less beamed population of jetted AGNs. The results are consistent with the unified model for radio galaxies and the conventional blazar subtypes. [ABSTRACT FROM AUTHOR]

We conduct X-ray reverberation mapping and spectral analysis of the radio galaxy Centaurus A to uncover its central structure. We compare the light curve of the hard X-ray continuum from Swift Burst Alert Telescope observations with that of the Fe K |$\alpha$| fluorescence line, derived from the Nuclear Spectroscopic Telescope Array (NuSTAR), Suzaku, XMM–Newton, and Swift X-ray Telescope observations. The analysis of the light curves suggests that a top-hat transfer function, commonly employed in reverberation mapping studies, is improbable. Instead, the relation between these light curves can be described by a transfer function featuring two components: one with a lag of |$0.19_{- 0.02}^{+ 0.10} \,\, \mathrm{pc}/c$|⁠ , and another originating at |$r \\gt 1.7 \,\, \mathrm{pc}$| that produces an almost constant light curve. Further, we analyze the four-epoch NuSTAR and six-epoch Suzaku spectra, considering the time lag of the reflection component relative to the primary continuum. This spectral analysis supports that the reflecting material is Compton-thin, with |$N_{\mathrm{H}} = 3.14_{-0.74}^{+0.44} \times 10^{23} \,\, \mathrm{cm}^{-2}$|⁠. These results suggest that the Fe K |$\alpha$| emission may originate from Compton-thin circumnuclear material located at a sub-parsec scale, likely a dust torus, and materials at a greater distance. [ABSTRACT FROM AUTHOR]

We present here radiosed , a Bayesian inference framework tailored to modelling and classifying broad-band radio spectral energy distributions (SEDs) using only data from publicly released, large-area surveys. We outline the functionality of radiosed , with its focus on broad-band radio emissions that can trace kiloparsec-scale absorption within both the radio jets and the circumgalactic medium of active galactic nuclei (AGN). In particular, we discuss the capability of radiosed to advance our understanding of AGN physics and composition within youngest and most compact sources, for which high-resolution imaging is often unavailable. These young radio AGN typically manifest as peaked spectrum sources that, before radiosed , were difficult to identify owing to the large, broad-band frequency coverage typically required, and yet they provide an invaluable environment for understanding AGN evolution and feedback. We discuss the implementation details of radiosed , and we validate our approach against both synthetic and observational data. Since the surveys used are drawn from multiple epochs of observation, we also consider the output from radiosed in the context of AGN variability. Finally, we show that radiosed recovers the expected SED shapes for a selection of well-characterized radio sources from the literature, and we discuss avenues for further study of these and other sources using radio SED fitting as a starting point. The scalability and modularity of this framework make it an exciting tool for multiwavelength astronomers as next-generation telescopes begin several all-sky surveys. Accordingly, we make the code for radiosed , which is written in python , available on GitHub. [ABSTRACT FROM AUTHOR]

Context. X-shaped radio galaxies (XRGs) are characterised by two pairs of misaligned lobes: active lobes hosting radio jets and the wings. None of the formation mechanisms proposed thus far are able to exhaustively reproduce the diverse features observed among XRGs. Emerging evidence has proposed the existence of sub-populations of XRGs forming via different processes. Aims. The brightest cluster galaxy (BCG) in Abell 3670 (A3670) is a dumbbell system hosting the XRG MRC 2011-298. The morphological and spectral properties of this interesting XRG were first characterised based on Karl G. Jansky Very Large Array (JVLA) data at 1–10 GHz. In the present work, we follow up on MRC 2011-298 with the upgraded Giant Metrewave Radio Telescope (uGMRT) at 120–800 MHz to further constrain its properties and origin. Methods. We carried out a detailed spectral analysis sampling different spatial scales. Integrated radio spectra, spectral index maps, radio colour-colour diagrams, and radiative age maps of both the active lobes and prominent wings were employed to test the origin of the source. Results. We confirm a progressive spectral steepening from the lobes to the wings. The maximum radiative age of the source is ~80 Myr, with the wings being older than the lobes by ≳30 Myr in their outermost regions. Conclusions. The observed properties are in line with an abrupt reorientation of the jets by ~90 deg from the direction of the wings to their present position. This formation mechanism is further supported by the comparison with numerical simulations in the literature, which additionally highlight the role of hydrodynamic processes in the evolution of large wings such as those of MRC 2011-298. It is plausible that the coalescence of supermassive black holes could have triggered the spin-flip of the jets. Moreover, we show that the S-shape of the radio jets is likely driven by precession with a period of P ~ 10 Myr. [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]

Context. Over the past two decades, our knowledge of the high-redshift (z > 5) radio quasars has expanded, thanks to dedicated high-resolution very long baseline interferometry (VLBI) observations. Distant quasars provide unique information about the formation and evolution of the first galaxies and supermassive black holes in the Universe. Powerful relativistic jets are likely to have played an essential role in these processes. However, the sample of VLBI-observed radio quasars is still too small to allow meaningful statistical conclusions. Aims. We extend the list of the VLBI observed radio quasars to investigate how the source structure and physical parameters are related to radio loudness. Methods. We assembled a sample of ten faint radio quasars located at 5 < z < 6 with their radio-loudness indices spanning between 0.9 − 76. We observed the selected targets with the European VLBI Network (EVN) at 1.7 GHz. The milliarcsecond-scale resolution of VLBI at this frequency allowed us to probe the compact innermost parts of radio-emitting relativistic jets. In addition to the single-band VLBI observations, we collected single-dish and low-resolution radio interferometric data to investigate the spectral properties and variability of our sources. Results. The detection rate of this high-redshift, low-flux-density sample is 90%, with only one target (J0306+1853) remaining undetected. The other nine sources appear core-dominated and show a single, faint and compact radio core on this angular scale. The derived radio powers are typical of Fanaroff-Riley II radio galaxies and quasars. By extending our sample with other VLBI-detected z > 5 sources from the literature, we found that the core brightness temperatures and monochromatic radio powers tend to increase with radio loudness. [ABSTRACT FROM AUTHOR]

We present the first observations of HCO+(1–0) and HCN(1–0) emission in the northern filaments of Centaurus A with ALMA. HCO+(1–0) is detected in nine clumps of the Horseshoe complex, with similar velocities as the CO(1–0) emission. Conversely, HCN(1–0) is not detected, and we derive upper limits on the flux. At a resolution of ∼40 pc, the line ratio of the velocity-integrated intensities IHCO+/ICO varies between 0.03 and 0.08, while IHCO+/IHCN is higher than unity, with an average lower limit of 1.51. These ratios are significantly higher than what is observed in nearby star-forming galaxies. Moreover, the ratio IHCO+/ICO decreases with increasing CO-integrated intensity, contrary to what is observed in the star-forming galaxies. This indicates that the HCO+ emission is enhanced and may not arise from dense gas within the Horseshoe complex. This hypothesis is strengthened by the average line ratio IHCN/ICO < 0.03, which suggests that the gas density is rather low. Using non-local thermal equilibrium, large velocity gradient modelling with RADEX, we explored two possible phases of the gas, which we call 'diffuse' and 'dense' and are characterised by a significant difference in the HCO+ abundance relative to CO, respectively NHCO+/NCO = 10−3 and NHCO+/NCO = 3 × 10−5. The average CO(1–0) and HCO+(1–0) integrated intensities and the upper limit on HCN(1–0) are compatible with both diffuse (nH = 103 cm−3, Tkin = 15 − 165 K) and dense gas (nH = 104 cm−3, Tkin > 65 K). The spectral setup of the present observations also covers SiO(2–1). While undetected, the upper limit on SiO(2–1) is not compatible with the RADEX predictions for the dense gas. We conclude that the nine molecular clouds detected in HCO+(1–0) are likely dominated by diffuse molecular gas. While the exact origin of the HCO+(1–0) emission remains to be investigated, it is likely related to the energy injection within the molecular gas that prevents gravitational collapse and star formation. [ABSTRACT FROM AUTHOR]

In the host galaxies of radio active galactic nuclei (AGN), kinematically disturbed gas due to jet-driven feedback is a widely observed phenomenon. Simulations predict that the impact of jets on the surrounding gas changes as they grow. Useful insights into this phenomenon can be obtained by characterising radio AGN into different evolutionary stages and studying their impact on gas kinematics. We present a systematic study of the [O III] gas kinematics for a sample of 5720 radio AGN up to z ∼ 0.8 with a large 1.4 GHz luminosity range of ≈1022.5 − 1028 W Hz−1, and 1693 [O III] detections. Our careful separation of radio emission from AGN and star formation allows us to isolate the impact of radio jets. Taking advantage of the wide frequency coverage of LOFAR and VLA surveys from 144 − 3000 MHz, we determine the radio spectral shapes, using them to characterise sources into different stages of the radio AGN life cycle. We determine the [O III] kinematics from SDSS spectra and link it to the life cycle. Our main conclusion is that the [O III] gas is ∼3 times more likely to be disturbed in the peaked spectrum (PS) sources (that represent a young phase of activity) than non-peaked spectrum (NPS) sources (that represent more evolved sources) at z < 0.4. This changes to a factor of ∼2 at z > 0.4. This shows that on average, the strong impact of jets is limited to the initial stages of the radio AGN life cycle. At later stages, the impact on gas is more gentle. We also determine the dependence of this trend on 1.4 GHz and [O III] luminosities, and find that the difference between the two groups increases with 1.4 GHz luminosity. Young radio AGN with L1.4 GHz > 1025 W Hz−1 have the most extreme impact on [O III]. Using a stacking analysis, we are further able to trace the changing impact on [O III] in the high frequency peaked spectrum (i.e. youngest), low frequency peaked spectrum ("less young"), and non-peaked spectrum (evolved) radio AGN. [ABSTRACT FROM AUTHOR]

We present the second data release of the MeerKAT Absorption Line Survey (MALS), consisting of wideband continuum catalogues of 391 pointings observed at L band. The full wideband catalogue covers 4344 deg2 of sky, reaches a depth of 10 µJy beam−1, and contains 971 980 sources. With its balance between survey depth and sky coverage, MALS DR2 covers five orders of magnitude of flux density, presenting a robust view of the extragalactic radio source population down to 200 µJy. Using this catalogue, we perform a measurement of the cosmic radio dipole, an anisotropy in the number counts of radio sources with respect to the cosmic background, analogous to the dipole found in the cosmic microwave background (CMB). For this measurement, we present the characterisation of completeness and noise properties of the catalogue, and show that a declination-dependent systematic affects the number density of faint sources. In the dipole measurement on the MALS catalogue, we recover reasonable dipole measurements once we model the declination systematic with a linear fit between the size of the major axis of the restoring beam and the amount of sources of each pointing. The final results are consistent with the CMB dipole in terms of direction and amplitude, unlike many recent measurements of the cosmic radio dipole made with other centimetre wavelength catalogues, which generally show a significantly larger amplitude. This result demonstrates the value of dipole measurements with deeper and more sparse radio surveys, as the population of faint sources probed may have had a significant impact on the measured dipole. [ABSTRACT FROM AUTHOR]

Context. Some giant radio galaxies selected at X-rays with active galactic nuclei (AGN) show signs of a restarted nuclear activity (old lobes plus a nuclear young radio source probed by giga-hertz peaked spectra). The study of these sources gives us insights into the AGN activity history. More specifically, the kinematics and properties of the outflows can be used as a tool to describe the activity of the source. Aims. One object in this peculiar class is Mrk 1498, a giant low-frequency double radio source that shows extended emission in [O III]. This emission is likely related to the history of the nuclear activity of the galaxy. We investigate whether this bubble-like emission might trace an outflow from either present or past AGN activity. Methods. Using a medium-resolution spectroscopy (R ∼ 10 000) available with MEGARA/GTC, we derived kinematics and fluxes of the ionised gas from modelling the [O III] and Hβ features. We identified three kinematic components and mapped their kinematics and flux. Results. All the components show an overall blue to red velocity pattern, with similar peak-to-peak velocities but a different velocity dispersion. At a galactocentric distance of ∼2.3 kpc, we found a blob with a velocity up to 100 km s−1, and a high velocity dispersion (∼170 km s−1) that is spatially coincident with the direction of the radio jet. The observed [O III]/Hβ line ratio indicates possible ionisation from AGN or shocks nearly everywhere. The clumpy structure visibile in HST images at kiloparsec scales show the lowest values of log[O III]/Hβ (< 1), which is likely not related to the photoionisation by the AGN. Conclusions. Taking optical and radio activity into account, we propose a scenario of two different ionised gas features over the radio AGN lifecycle of Mrk 1498. The radio emission suggests at least two main radio activity episodes: an old episode at megaparsec scales (formed during a time span of ∼100 Myr), and a new episode from the core (> 2000 yr ago). At optical wavelengths, we observe clumps and a blob that are likely associated with fossil outflow. The latter is likely powered by past episodes of the flickering AGN activity that may have occurred between the two main radio phases. [ABSTRACT FROM AUTHOR]

Context. Self-supervised learning (SSL) applied to natural images has demonstrated a remarkable ability to learn meaningful, low-dimension representations without labels, resulting in models that are adaptable to many different tasks. Until now, applications of SSL to astronomical images have been limited to Galaxy Zoo datasets, which require a significant amount of preprocessing to prepare sparse images centered on a single galaxy. With wide-field survey instruments at the forefront of the Square Kilometer Array (SKA) era, this approach to gathering training data is impractical. Aims. We demonstrate that continuum images from surveys such as the MeerKAT Galactic Cluster Legacy Survey (MGCLS) can be successfully used with SSL, without extracting single-galaxy cutouts. Methods. Using the SSL framework DINO, we experimented with various preprocessing steps, augmentations, and architectures to determine the optimal approach for this data. We trained both ResNet50 and Vision Transformer (ViT) backbones. Results. Our models match state-of-the-art results (trained on Radio Galaxy Zoo) for FRI/FRII morphology classification. Furthermore, they predict the number of compact sources via linear regression with much higher accuracy. Open-source foundation models trained on natural images such as DINOv2 also excel at simple FRI/FRII classification; the advantage of domain-specific backbones is much smaller models trained on far less data. Smaller models are more efficient to fine-tune, and doing so results in a similar performance between our models, the state-of-the-art, and open-source models on multi-class morphology classification. Conclusions. Using source-rich crops from wide-field images to train multi-purpose models is an easily scalable approach that significantly reduces data preparation time. For the tasks evaluated in this work, twenty thousand crops is sufficient training data for models that produce results similar to state-of-the-art. In the future, complex tasks like source detection and characterization, together with domain-specific tasks, ought to demonstrate the true advantages of training models with radio astronomy data over natural-image foundation models. [ABSTRACT FROM AUTHOR]

Context. The upcoming Square Kilometer Array (SKA) will set a new standard regarding data volume generated by an astronomical instrument, which is likely to challenge widely adopted data-analysis tools that scale inadequately with the data size. Aims. The aim of this study is to develop a new source detection and characterization method for massive radio astronomical datasets based on modern deep-learning object detection techniques. For this, we seek to identify the specific strengths and weaknesses of this type of approach when applied to astronomical data. Methods. We introduce YOLO-CIANNA, a highly customized deep-learning object detector designed specifically for astronomical datasets. In this paper, we present the method and describe all the elements introduced to address the specific challenges of radio astronomical images. We then demonstrate the capabilities of this method by applying it to simulated 2D continuum images from the SKA observatory Science Data Challenge 1 (SDC1) dataset. Results. Using the SDC1 metric, we improve the challenge-winning score by +139% and the score of the only other post-challenge participation by +61%. Our catalog has a detection purity of 94% while detecting 40–60% more sources than previous top-score results, and exhibits strong characterization accuracy. The trained model can also be forced to reach 99% purity in post-process and still detect 10–30% more sources than the other top-score methods. It is also computationally efficient, with a peak prediction speed of 500 images of 512×512 pixels per second on a single GPU. Conclusions. YOLO-CIANNA achieves state-of-the-art detection and characterization results on the simulated SDC1 dataset and is expected to transfer well to observational data from SKA precursors. [ABSTRACT FROM AUTHOR]

Context. High-redshift radio(-loud) galaxies (HzRGs) are massive galaxies with powerful radio-loud active galactic nuclei (AGNs) and serve as beacons for protocluster identification. However, the interplay between HzRGs and the large-scale environment remains unclear. Aims. To understand the connection between HzRGs and the surrounding obscured star formation, we investigated the overdensity and spatial distribution of submillimeter-bright galaxies (SMGs) in the field of 4C 23.56, a well-known HzRG at z = 2.48. Methods. We used SCUBA-2 data (σ ∼ 0.6 mJy) to estimate the 850 μm source number counts and examine the radial and azimuthal overdensities of the 850 μm sources in the vicinity of the HzRG. Results. The angular distribution of SMGs is inhomogeneous around the HzRG 4C 23.56, with fewer sources oriented along the radio jet. We also find a significant overdensity of bright SMGs (S​850 μm ≥ 5 mJy). Faint and bright SMGs exhibit different spatial distributions. The former are concentrated in the core region, while the latter prefer the outskirts of the HzRG field. High-resolution observations show that the seven brightest SMGs in our sample are intrinsically bright, suggesting that the overdensity of bright SMGs is less likely due to the source multiplicity. [ABSTRACT FROM AUTHOR]

During the epoch of reionization (EoR), the 21-cm signal allows direct observation of the neutral hydrogen (H  i) in the intergalactic medium (IGM). In the post-reionization era, this signal instead probes H  i in galaxies, which traces the dark matter density distribution. With new numerical simulations, we investigated the end stages of reionization to elucidate the transition of our Universe into the post-reionization era. Our models are consistent with the latest high-redshift measurements, including ultraviolet (UV) luminosity functions up to redshift |$\simeq$| 8. Notably, these models consistently reproduced the evolution of the UV photon background, which is constrained from Lyman- |$\alpha$| absorption spectra. We studied the dependence of this background on the nature of photon sinks in the IGM, requiring mean free path of UV photons to be |$\sim$| 10 comoving-megaparsecs (cMpc) during the EoR that increases gradually with time during late stages (⁠|$z\lesssim 6$|⁠). Our models revealed that the reionization of the IGM transitioned from an inside-out to an outside-in process when the Universe is less than 0.01 per cent neutral. During this epoch, the 21-cm signal also shifted from probing predominantly the H  i in the IGM to that in galaxies. Furthermore, we identified a statistically significant number of large neutral islands (with sizes up to 40 cMpc) persisting until very late stages (⁠|$5 \lesssim z \lesssim 6$|⁠) that can imprint features in Lyman- |$\alpha$| absorption spectra and also produce a knee-like feature in the 21-cm power spectrum. [ABSTRACT FROM AUTHOR]