The Indian Pulsar Timing Array (InPTA) employs unique features of the upgraded Giant Metrewave Radio Telescope (uGMRT) to monitor dozens of the International Pulsar Timing Array (IPTA) millisecond pulsars (MSPs), simultaneously in the 300–500 MHz and the 1260–1460 MHz bands. This dual-band approach ensures that any frequency-dependent delays are accurately characterised, significantly improving the timing precision for pulsar observations, which is crucial for pulsar timing arrays. We present details of InPTA’s second data release that involves 7 yr of data on 27 IPTA MSPs. This includes sub-banded times of arrival (ToAs), dispersion measures (DM), and initial timing ephemerides for our MSPs. A part of this dataset, originally released in InPTA’s first data release, is being incorporated into IPTA’s third data release, which is expected to detect and characterise nanohertz gravitational waves (GWs) in the coming years. The entire dataset is reprocessed in this second data release providing some of the highest precision DM estimates so far and interesting solar wind-related DM variations in some pulsars. This is likely to characterise the noise introduced by the dynamic inter-stellar ionised medium much better than the previous release thereby increasing sensitivity to any future GW search.

Measurements of the ionisation state of the intergalactic medium (IGM) can probe the sources of the extragalactic ionising background. We provide new measurements of the ionising emissivity of galaxies using measurements of the ionising background and ionising photon mean free path from high-redshift quasar spectra at $2.5 \lt z \lt 6$. Unlike most prior works, we account for radiative-transfer effects and possible neutral islands from the tail of reionisation at $z \gt 5$. We combine our results with measurements of the UV luminosity function to constrain the average escaping ionising efficiency of galaxies, $\langle f_{\textrm{esc}} \xi_{\textrm{ion}}\rangle_{L_{\textrm{UV}}}$. Assuming galaxies with $M_{\textrm{UV}} \lt -11$ emit ionising photons, we find $\log (\langle f_{\textrm{esc}} \xi_{\textrm{ion}}\rangle_{L_{\textrm{UV}}}/{\textrm {erg}^{-1}Hz}) = 24.47_{-0.17}^{+0.09}$ and $24.75_{-0.28}^{+0.15}$ at $z=5$ and 6, and $1\sigma$ upper limits of $24.48$ and $24.31$ at $z = 2.5$ and 4, respectively. We also estimate the population-averaged $f_{\textrm{esc}}$ using measurements of intrinsic ionising efficiency from JWST. We find $\langle f_{\textrm{esc}} \rangle = 0.126_{-0.041}^{+0.034}$ and $0.224_{-0.108}^{+0.098}$ at $z=5$ and 6, and $1\sigma$ upper limits of $f_{\textrm{esc}}\lt 0.138$ and $0.096$ at $z=2.5$ and 4, respectively, for $M_{\textrm{UV}} \lt -11$. Our findings are consistent with prior measurements of $f_{\textrm{esc}} \lesssim 10\%$ at $z \leq 4$, but indicate a factor of several increase between $z = 4$ and 6. The steepness of this evolution is sensitive to the highly uncertain mean free path and ionising background intensity at $z\gt5$. Lastly, we find $1.10^{+0.21}_{-0.39}$ photons per H atom are emitted into the IGM between $z=6$ and $=5.3$. This is $\approx 4\times$ more than needed to complete the last 20% of reionisation absent recombinations, suggesting that reionisation’s end was likely absorption-dominated.

It is thought that isolated neutron stars receive a natal kick velocity at birth nearly aligned with their spin axis. Direct observational confirmation of this alignment is currently limited to a single source in a supernova remnant (PSR J0538+2817), for which the three-dimensional velocity has been well constrained. Meanwhile, pulsar polarisation statistics suggest the existence of a spin-kick correlation, though both aligned and orthogonal cases remain possible. However, if the velocities of radiopulsars are predominantly aligned with their spin axes, a systematic difference in the observed transverse velocities of pulsars with small and large magnetic obliquities would be expected. In particular, due to projection effects, weakly oblique rotators should exhibit smaller, less scattered transverse velocities. Conversely, the transverse velocities of pulsars with large magnetic inclination should reflect their actual three-dimensional velocities. This study uses this idea to analyse samples of 13 weakly and 25 strongly oblique pulsars with known distances and proper motions. We find that their peculiar velocities are distributed differently, with statistical confidence levels of 0.007 and 0.016 according to the Anderson–Darling and Kolmogorov–Smirnov tests, respectively. We performed a detailed population synthesis of isolated pulsars, considering the evolution of their viewing geometry in isotropic and spin-aligned kick scenarios. The observed split in the transverse velocity distributions and its amplitude are consistent with the spin-aligned kick model, but not with the isotropic case. At the same time, an orthogonal kick would predict a similar effect, but with the opposite sign. This provides robust support for pulsar spin kick alignment based on statistics, independently of polarisation.

The advent of next-generation telescope facilities brings with it an unprecedented amount of data, and the demand for effective tools to process and classify this information has become increasingly important. This work proposes a novel approach to quantify the radio galaxy morphology, through the development of a series of algorithmic metrics that can quantitatively describe the structure of radio source, and can be applied to radio images in an automatic way. These metrics are intuitive in nature and are inspired by the intrinsic structural differences observed between the existing Fanaroff-Riley (FR) morphology types. The metrics are defined in categories of asymmetry, blurriness, concentration, disorder, and elongation (ABCDE/single-lobe metrics), as well as the asymmetry and angle between lobes (source metrics). We apply these metrics to a sample of 480 sources from the Evolutionary Map of the Universe Pilot Survey (EMU-PS) and 72 well resolved extensively studied sources from An Atlas of DRAGNs, a subset of the revised Third Cambridge Catalogue of Radio Sources (3CRR). We find that these metrics are relatively robust to resolution changes, independent of each other, and measure fundamentally different structural components of radio galaxy lobes. These metrics work particularly well for sources with reasonable signal-to-noise and well separated lobes. We also find that we can recover the original FR classification using probabilistic combinations of our metrics, highlighting the usefulness of our approach for future large data sets from radio sky surveys.

We present the serendipitous radio-continuum discovery of a likely Galactic supernova remnant (SNR) G305.4–2.2. This object displays a remarkable circular symmetry in shape, making it one of the most circular Galactic SNRs known. Nicknamed Teleios due to its symmetry, it was detected in the new Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) radio–continuum images with an angular size of 1 320$^{\prime\prime}$$\times$1 260$^{\prime\prime}$ and PA = 0$^\circ$. While there is a hint of possible H$\alpha$ and gamma-ray emission, Teleios is exclusively seen at radio–continuum frequencies. Interestingly, Teleios is not only almost perfectly symmetric, but it also has one of the lowest surface brightnesses discovered among Galactic SNRs and a steep spectral index of $\alpha$=–0.6$\pm$0.3. Our best estimates from Hi studies and the $\Sigma$–D relation place Teleios as a type Ia SNR at a distance of either $\sim$2.2 kpc (near-side) or $\sim$7.7 kpc (far-side). This indicates two possible scenarios, either a young (under 1 000 yr) or a somewhat older SNR (over 10 000 yr). With a corresponding diameter of 14/48 pc, our evolutionary studies place Teleios at the either early or late Sedov phase, depending on the distance/diameter estimate. However, our modelling also predicts X-ray emission, which we do not see in the present generation of eROSITA images. We also explored a type Iax explosion scenario that would point to a much closer distance of $\lt$1 kpc and Teleios size of only $\sim$3.3 pc, which would be similar to the only known type Iax remnant SN1181. Unfortunately, all examined scenarios have their challenges, and no definitive Supernova (SN) origin type can be established at this stage. Remarkably, Teleios has retained its symmetrical shape as it aged even to such a diameter, suggesting expansion into a rarefied and isotropic ambient medium. The low radio surface brightness and the lack of pronounced polarisation can be explained by a high level of ambient rotation measure (RM), with the largest RM being observed at Teleios’s centre.

Studying the diffuse Galactic synchrotron emission (hereafter, DGSE) at arc-minute angular scale is important to remove the foregrounds for the cosmological 21-cm observations. Statistical measurements of the large-scale DGSE can also be used to constrain the magnetic field and the cosmic ray electron density of our Galaxy’s interstellar medium. Here, we have used the Murchison Widefield Array drift scan observations at $154.2 \, \textrm{MHz}$ to measure the angular power spectrum $({\mathcal C}_{\ell})$ of the DGSE of a region of the sky from right ascension $349^{\circ}$ to $70.3^{\circ}$ at the fixed declination $-26.7^{\circ}$. In this RA range, we have chosen 24 pointing centers (PCs), for which we have removed all the bright point sources above $\sim430 \, \textrm{mJy}\,(3\sigma)$, and applied the Tapered Gridded Estimator on residual data to estimate the ${\mathcal C}_{\ell}$. We use the angular multipole range $65 \le \ell \le 650$ to fit the data with a model, ${\mathcal C}^M_{\ell}=A\times \left(\frac{1\,000}{\ell}\right)^{\beta}+C$, where we interpret the model as the combination of a power law $(\propto \ell^{-\beta})$ nature of the DGSE and a constant part due to the Poisson fluctuations of the residual point sources. We are able to fit the model ${\mathcal C}^M_{\ell}$ for six PCs centered at $\alpha=352.5^{\circ}, 353^{\circ}, 357^{\circ}, 4.5^{\circ}, 4^{\circ}$, and $1^{\circ}$. We run the Markov Chain Monte Carlo (MCMC) ensemble sampler to get the best-fit values of the parameters $A, \beta$, and C for these PCs. We see that the values of A vary in the range 155–400 mK$^{2}$, whereas the $\beta$ varies in the range $0.9$–$1.7$. We find that the value of $\beta$ is consistent at $2-\sigma$ level with the earlier measurement of the DGSE at similar frequency and angular scales.

This work introduces GalProTE, a proof-of-concept Machine Learning model, leveraging Transformer Encoder architecture to efficiently determine the stellar age, metallicity, and dust attenuation of galaxies from optical spectra. Designed to address the challenges posed by the vast datasets produced by modern astronomical surveys, GalProTE offers a significant improvement in processing speed while maintaining accuracy. Using the E-MILES spectral library, we generate a dataset of 111936 diverse templates by expanding the original 636 simple stellar population models with varying extinction levels, combinations of multiple spectra, and noise modifications. This ensures robust training over the spectral range of 4750–7100 Å at a resolution of 2.5 Å. GalProTE architecture employs four parallel attention-based encoders with varying kernel sizes to capture diverse spectral features. The model demonstrates a mean squared error (MSE) of 0.27% with a standard deviation of 0.10% between the input spectra and the GalProTE-generated spectra for the synthetic test dataset. Performance evaluation against real data from two galaxies in the PHANGS-MUSE survey (NGC4254 and NGC5068) demonstrates its ability to extract physical parameters efficiently, with spectral fit residuals showing a mean of -0.02% and 0.28%, and standard deviations of 4.3% and 5.3%, respectively. To contextualize these results, we compare age, metallicity and dust attenuation maps generated by GalProTE with those of pPXF, a state-of-the-art spectral fitting tool. While pPXF achieves robust results, it requires approximately 11 sec per spectrum. In contrast, GalProTE processes a spectrum in less than 4 ms – a speedup factor exceeding 2750, while also consuming 68 times less power per spectrum. The comparison with pPXF maps from PHANGS-MUSE underscores GalProTE’s capacity to enhance traditional methods through machine learning, paving the way for faster, more energy-efficient, and more comprehensive analyses of galactic properties. This study demonstrates the potential of GalProTE as an efficient, scalable, and sustainable solution for processing large astronomical surveys.

We present the first radio–continuum detection of the circumstellar shell around the well-known WN8 type Wolf-Rayet star WR16 at 943.5 MHz using the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey. At this frequency, the shell has a measured flux density of 72.2$\pm$7.2 mJy. Using previous Australia Telescope Compact Array (ATCA) measurements at 2.4, 4.8, and 8.64 GHz, as well as the Evolutionary Map of the Universe (EMU) observations of the star itself, we determine a spectral index of $\alpha\,=\,+0.74\pm0.02$, indicating thermal emission. We propose that the shell and star both exhibit thermal emission, supported by the its appearance in near-infrared and H$\alpha$ observations. The latest Gaia parallax is used to determine a distance of 2.28$\pm$0.09 kpc. This star is well known for its surrounding circular nebulosity, and using the distance and an angular diameter of $8.^{\prime}42$, we determine the shell size to be 5.57$\pm$0.22 pc. We use the Gaia proper motion (PM) of WR16 to determine peculiar velocities of the star as $V_{\alpha}(pec) =$ –45.3$\pm$5.4 km s$^{-1}$ and $V_{\delta}(pec) =$ 22.8$\pm$4.7 km s$^{-1}$, which indicates that the star is moving in a north-west direction, and translates to a peculiar tangential velocity to be 50.7$\pm$6.9 km s$^{-1}$. We also use these proper motion (PM) to determine the shell’s origin, estimate an age of $\sim 9500\pm 1300$ yr, and determine its average expansion velocity to be $280\pm40$ km s$^{-1}$. This average expansion velocity suggests that the previous transitional phase is a Luminous Blue Variable (LBV) phase, rather than a Red Super Giant (RSG) phase. We also use the measured flux at 943.5 MHz to determine a mass-loss rate of $1.753\times 10^{-5}\,{\rm M}_\odot\,$yr$^{-1}$, and use this to determine a lower-limit on ionising photons of $N_{UV} \gt 1.406\times 10^{47}\,\textit{s}^{-1}$.

We investigate the evolution of active galactic nucleus jets on kiloparsec-scales due to their interaction with the clumpy interstellar medium (ISM) of the host galaxy and, subsequently, the surrounding circumgalactic environment. Hydrodynamic simulations of this jet–environment interaction are presented for a range of jet kinetic powers, peak densities of the multiphase ISM, and scale radii of the larger-scale environment – characteristic of either a galaxy cluster or poor group. Synthetic radio images are generated by considering the combination of synchrotron radiation from the jet plasma and free-free absorption from the multiphase ISM. We find that jet propagation is slowed by interactions with a few very dense clouds in the host galaxy ISM, producing asymmetries in lobe length and brightness which persist to scales of tens of kpc for poor group environments. The classification of kiloparsec-scale jets is highly dependent on surface brightness sensitivity and resolution. Our simulations of young active sources can appear as restarted sources, showing double-double lobe morphology, high core prominence (CP $\gt 0.1$), and the expected radio spectra for both the inner- and outer-lobe components. We qualitatively reproduce the observed inverse correlation between peak frequency and source size and find that the peak frequency of the integrated radio spectrum depends on ISM density but not the jet power. Spectral turnover in resolved young radio sources therefore provides a new probe of the ISM.

We present Evolutionary Map of the Universe Search Engine (EMUSE), a tool designed for searching specific radio sources within the extensive datasets of the Evolutionary Map of the Universe (EMU) survey, with potential applications to other Big Data challenges in astronomy. Built on a multimodal approach to radio source classification and retrieval, EMUSE fine-tunes the OpenCLIP model on curated radio galaxy datasets. Leveraging the power of foundation models, our work integrates visual and textual embeddings to enable efficient and flexible searches within large radio astronomical datasets. We fine-tune OpenCLIP using a dataset of 2 900 radio galaxies, encompassing various morphological classes, including FR-I, FR-II, FR-x, R-type, and other rare and peculiar sources. The model is optimised using adapter-based fine-tuning, ensuring computational efficiency while capturing the unique characteristics of radio sources. The fine-tuned model is then deployed in the EMUSE, allowing for seamless image and text-based queries over the EMU survey dataset. Our results demonstrate the model’s effectiveness in retrieving and classifying radio sources, particularly in recognising distinct morphological features. However, challenges remain in identifying rare or previously unseen radio sources, highlighting the need for expanded datasets and continuous refinement. This study showcases the potential of multimodal machine learning in radio astronomy, paving the way for more scalable and accurate search tools in the field. The search engine is accessible at https://askap-emuse.streamlit.app/ and can be used locally by cloning the repository at https://github.com/Nikhel1/EMUSE.

Very long baseline interferometry (VLBI) astrometry is used to determine the three-dimensional position and proper motion of astronomical objects. A typical VLBI astrometric campaign generally includes around ten observations, making it challenging to characterise systematic uncertainties. Our study on two bright pulsars, B0329+54 and B1133+16, involves analysis of broadband Very Long Baseline Array (VLBA) data over $\sim30$ epochs (spanning approximately 3.5 yr). This extended dataset has significantly improved the precision of the astrometric estimates of these pulsars. Our broadband study suggests that, as expected, the primary contribution to systematic uncertainties in L-band VLBI astrometry originates from the ionosphere. We have also assessed the effectiveness of the modified total electron content (TEC) mapping function, which converts vertical TEC to slant TEC, in correcting ionospheric dispersive delays using global TEC maps. The astrometric parameters (parallax and proper motion) obtained from the multiple datasets, calibrated using the traditional and the modified TEC mapping functions, are consistent. However, the reduced chi-square values from least-squares fitting and precision of the fitted astrometric parameters show no significant improvement, and hence, the effectiveness of the new TEC mapping function on astrometry is unclear. For B0329+54, the refined parallax estimate is $0.611^{+0.013}_{-0.013}$ mas, with best-fit proper motion of $\mu_{\alpha} = 16.960^{+0.011}_{-0.010}\, \textrm{mas}\,{\rm yr}^{-1}$ in R.A. and and $\mu_{\delta} = -10.382^{+0.022}_{-0.022}\,\textrm{mas}\,{\rm yr}^{-1}$ in Dec. These correspond to a distance of $1.64^{+0.03}_{-0.03}$ kpc and a transverse velocity of $\sim 154\, \textrm{km}\,{\rm s}^{-1}$. For B1133+16, the new estimated parallax is $2.705^{+0.009}_{-0.009}$ mas, with proper motions of $\mu_{\alpha} = -73.777^{+0.008}_{-0.008}\, \textrm{mas}\,{\rm yr}^{-1}$ and $\mu_{\delta} = 366.573^{+0.019}_{-0.019}\, \textrm{mas}\,{\rm yr}^{-1}$, implying a distance of $370^{+1}_{-1}$ pc and a transverse velocity of $\sim 656\, \textrm{km}\,{\rm s}^{-1}$. The proper motions of B0329+54 and B1133+16 are consistent within $1\sigma$ of the most precise values reported in the literature to date while achieving more than a twofold improvement in precision. Similarly, the parallax measurements for both pulsars show a $\sim 73\%$ enhancement in precision, with differences of approximately $\lt 1\sigma$ compared to the most precise published values to date.

We present a systematic search for Odd Radio Circles (ORCs) and other unusual radio morphologies using data from the first year of the Evolutionary Map of the Universe (EMU) survey. ORCs are rare, enigmatic objects characterised by edge-brightened rings of radio emission, often found in association with distant galaxies. To identify these objects, we employ a hybrid methodology combining supervised object detection techniques and visual inspection of radio source candidates. This approach leads to the discovery of five new ORCs and two additional candidate ORCs, expanding the known population of these objects. In addition to ORCs, we also identify 55 Galaxies with Large-scale Ambient Radio Emission (GLAREs), which feature irregular, rectangular, or circular shapes of diffuse radio emission mostly surrounding central host galaxies. These GLAREs may represent different evolutionary stages of ORCs and studying them could offer valuable insights into their evolutionary processes. We also highlight a subset of Starburst Radio Ring Galaxies, which are star-forming galaxies exhibiting edge-brightened radio rings surrounding their central star-forming regions. We emphasise the importance of multi-wavelength follow-up observations to better understand the physical properties, host galaxy characteristics, and evolutionary pathways of these radio sources.

We have examined the nuclear spectra of very massive star-forming galaxies at $z \sim 0$ to understand how they differ from other galaxies with comparable masses, which are typically passive. We selected a sample of 126 nearby massive star-forming galaxies ($\lt100\,\textrm{Mpc}$, $10^{11.3}\,\mathrm{M_\odot} \leq M_\textrm{stellar} \leq 10^{11.7}\,\mathrm{M_\odot}$, $1 \,\mathrm{M_\odot\,yr^{-1}}\lt \textrm{SFR} \lt13 \,\mathrm{M_\odot\,yr^{-1}}$) from the 2MRS-Bright WXSC catalogue. LEDA morphologies indicate at least 63% of our galaxies are spirals, while visual inspection of Dark Energy Survey images reveals 75% of our galaxies to be spirals with the remainder being lenticular. Of our sample 59 have archival nuclear spectra, which we have modelled and subsequently measured emission lines ([NII]${\lambda 6583}$, H$\alpha{\lambda 6563}$, [OIII]${\lambda 5008}$, and H$\beta{\lambda 4863}$), classifying galaxies as star-forming, LINERs or AGNs. Using a BPT diagram we find $83 \pm 6$% of our galaxies, with sufficient signal-to-noise to measure all 4 emission lines, to be LINERs. Using the [NII]${\lambda 6583}$/H$\alpha{\lambda 6563}$ emission line ratio alone we find that $79 \pm 6$% of the galaxies (46 galaxies) with archival spectra are LINERs, whereas just $\sim 30\%$ of the overall massive galaxy population are LINERs (Belfiore et al. 2016, MNRAS, 461, 3111). Our sample can be considered a local analogue of the Ogle et al. (2019, VizieR Online Data Catalog, p. J/ApJS/243/14; 2016, ApJ, 817, 109) sample of $z \sim 0.22$ massive star-forming galaxies in terms of selection criteria, and we find 64% of their galaxies are LINERs using SDSS spectra. The high frequency of LINER emission in these massive star-forming galaxies indicates that LINER emission in massive galaxies may be linked to the presence of gas that fuels star formation.

This study presents the black hole accretion history of obscured active galactic nuclei (AGNs) identified from the JWST CEERS survey by Chien et al. (2024) using mid-infrared (MIR) SED fitting. We compute black hole accretion rates (BHARs) to estimate the black hole accretion density (BHAD), $\rho_{L_{\text{disk}}}$, across $0 \lt z \lt 4.25$. MIR luminosity functions (LFs) are also constructed for these sources, modeled with modified Schechter and double power law forms, and corresponding BHAD, $\rho_{\text{LF}}$, is derived by integrating the LFs and multiplying by the luminosity. Both $\rho_{\text{LF}}$ extend to luminosities as low as $10^7 \, {\rm L}_{\odot}$, two orders of magnitude fainter than pre-JWST studies. Our results show that BHAD peaks between redshifts 1 and 3, with the peak varying by method and model, $z \simeq$ 1 - 2 for $\rho_{L_{\text{disk}}}$ and the double power law, and $z \simeq$ 2 - 3 for the modified Schechter function. A scenario where AGN activity peaks before cosmic star formation would challenge existing black hole formation theories, but our present study, based on early JWST observations, provides an initial exploration of this possibility. At $z \sim 3$, $\rho_{\text{LF}}$ appears higher than X-ray estimates, suggesting that MIR observations are more effective in detecting obscured AGNs missed by X-ray observations. However, given the overlapping error bars, this difference remains within the uncertainties and requires confirmation with larger samples. These findings highlight the potential of JWST surveys to enhance the understanding of co-evolution between galaxies and AGNs.

Searches for impulsive, astrophysical transients are often highly computationally demanding. A notable example is the dedispersion process required for performing blind searches for fast radio bursts (FRBs) in radio telescope data. We introduce a novel approach – efficient summation of arbitrary masks (ESAM) – which efficiently computes 1D convolution of many arbitrary 2D masks and can be used to carry out dedispersion over thousands of dispersion trials efficiently. Our method matches the accuracy of the traditional brute force technique in recovering the desired signal-to-noise ratio while reducing computational cost by around a factor of 10. We compare its performance with existing dedispersion algorithms, such as the fast dispersion measure transform algorithm, and demonstrate how ESAM provides freedom to choose arbitrary masks and further optimise computational cost versus accuracy. We explore the potential applications of ESAM beyond FRB searches.

The next-generation radio astronomy instruments are providing a massive increase in sensitivity and coverage, largely through increasing the number of stations in the array and the frequency span sampled. The two primary problems encountered when processing the resultant avalanche of data are the need for abundant storage and the constraints imposed by I/O, as I/O bandwidths drop significantly on cold storage. An example of this is the data deluge expected from the SKA Telescopes of more than 60 PB per day, all to be stored on the buffer filesystem. While compressing the data is an obvious solution, the impacts on the final data products are hard to predict. In this paper, we chose an error-controlled compressor – MGARD – and applied it to simulated SKA-Mid and real pathfinder visibility data, in noise-free and noise-dominated regimes. As the data have an implicit error level in the system temperature, using an error bound in compression provides a natural metric for compression. MGARD ensures the compression incurred errors adhere to the user-prescribed tolerance. To measure the degradation of images reconstructed using the lossy compressed data, we proposed a list of diagnostic measures, exploring the trade-off between these error bounds and the corresponding compression ratios, as well as the impact on science quality derived from the lossy compressed data products through a series of experiments. We studied the global and local impacts on the output images for continuum and spectral line examples. We found relative error bounds of as much as 10%, which provide compression ratios of about 20, have a limited impact on the continuum imaging as the increased noise is less than the image RMS, whereas a 1% error bound (compression ratio of 8) introduces an increase in noise of about an order of magnitude less than the image RMS. For extremely sensitive observations and for very precious data, we would recommend a $0.1\%$ error bound with compression ratios of about 4. These have noise impacts two orders of magnitude less than the image RMS levels. At these levels, the limits are due to instabilities in the deconvolution methods. We compared the results to the alternative compression tool DYSCO, in both the impacts on the images and in the relative flexibility. MGARD provides better compression for similar error bounds and has a host of potentially powerful additional features.

Emission line galaxies (ELGs) are crucial for cosmological studies, particularly in understanding the large-scale structure of the Universe and the role of dark energy. ELGs form an essential component of the target catalogue for the Dark Energy Spectroscopic Instrument (DESI), a major astronomical survey. However, the accurate selection of ELGs for such surveys is challenging due to the inherent uncertainties in determining their redshifts with photometric data. In order to improve the accuracy of photometric redshift estimation for ELGs, we propose a novel approach CNN–MLP that combines convolutional neural networks (CNNs) with multilayer perceptrons (MLPs). This approach integrates both images and photometric data derived from the DESI Legacy Imaging Surveys Data Release 10. By leveraging the complementary strengths of CNNs (for image data processing) and MLPs (for photometric feature integration), the CNN–MLP model achieves a $\sigma_{\mathrm{NMAD}}$ (normalised median absolute deviation) of 0.0140 and an outlier fraction of 2.57%. Compared to other models, CNN–MLP demonstrates a significant improvement in the accuracy of ELG photometric redshift estimation, which directly benefits the target selection process for DESI. In addition, we explore the photometric redshifts of different galaxy types (Starforming, Starburst, AGN, and Broadline). Furthermore, this approach will contribute to more reliable photometric redshift estimation in ongoing and future large-scale sky surveys (e.g. LSST, CSST, and Euclid), enhancing the overall efficiency of cosmological research and galaxy surveys.

The Australian SKA Pathfinder (ASKAP) offers powerful new capabilities for studying the polarised and magnetised Universe at radio wavelengths. In this paper, we introduce the Polarisation Sky Survey of the Universe’s Magnetism (POSSUM), a groundbreaking survey with three primary objectives: (1) to create a comprehensive Faraday rotation measure (RM) grid of up to one million compact extragalactic sources across the southern $\sim50$% of the sky (20,630 deg$^2$); (2) to map the intrinsic polarisation and RM properties of a wide range of discrete extragalactic and Galactic objects over the same area; and (3) to contribute interferometric data with excellent surface brightness sensitivity, which can be combined with single-dish data to study the diffuse Galactic interstellar medium. Observations for the full POSSUM survey commenced in May 2023 and are expected to conclude by mid-2028. POSSUM will achieve an RM grid density of around 30–50 RMs per square degree with a median measurement uncertainty of $\sim$1 rad m$^{-2}$. The survey operates primarily over a frequency range of 800–1088 MHz, with an angular resolution of 20” and a typical RMS sensitivity in Stokes Q or U of 18 $\mu$Jy beam$^{-1}$. Additionally, the survey will be supplemented by similar observations covering 1296–1440 MHz over 38% of the sky. POSSUM will enable the discovery and detailed investigation of magnetised phenomena in a wide range of cosmic environments, including the intergalactic medium and cosmic web, galaxy clusters and groups, active galactic nuclei and radio galaxies, the Magellanic System and other nearby galaxies, galaxy halos and the circumgalactic medium, and the magnetic structure of the Milky Way across a very wide range of scales, as well as the interplay between these components. This paper reviews the current science case developed by the POSSUM Collaboration and provides an overview of POSSUM’s observations, data processing, outputs, and its complementarity with other radio and multi-wavelength surveys, including future work with the SKA.

We present an analysis of the hard X-ray emission from the central region of Abell 3667 using deep NuSTAR observations. While previous studies on the nature of the hard X-ray excess have been controversial, our analysis of the central region suggests that the excess is primarily thermal, best described by a two-temperature (2T) model, with the high-temperature component likely arising from merger-induced heating. This interpretation contrasts with some earlier suggestions of non-thermal emission due to inverse Compton scattering of relativistic electrons. Additionally, we set a lower limit on the magnetic field strength of $\sim 0.2 \, \unicode{x03BC}$G in the central region, consistent with values found in other dynamically active clusters and compatible with those inferred from equipartition and Faraday rotation measurements. Since our study is focused on the central region of the cluster, further high-resolution observations of the outer regions will be critical to fully disentangle the thermal and non-thermal contributions to the X-ray.

Here we analyse the archival data for a set of 27 Transiting Exoplanet Survey Satellite Targets of Interest in search for artificially generated radio signals, or ‘technosignatures’, interrupted by occultation. Exoplanetary eclipses are notable events to observe in the search for technosignatures, as they mark the geometrical alignment of the target, its host star, and Earth. During an eclipse event, any signal emanating from the target of interest should cease for the duration of the eclipse and resume after the line-of-sight has been restored. Target observations were made by Breakthrough Listen using Murriyang, the CSIRO Parkes 64-m radio telescope, coupled with the ultra-wide low frequency receiver covering a continuous range of frequencies spanning 704–4 032 MHz inclusive. Each target was observed in a pattern consisting of six back-to-back 5-min source and reference sky positions for comparison during data analysis. We performed a Doppler search for narrowband signals with a minimum signal-to-noise ratio of 10, a minimum drift rate of $\pm\,0.1$ Hz/s, and a maximum drift rate of $\pm\,4.0$ Hz/s using the turboseti pipeline. In the analysis of 1 954 880 signals, 14 639 passed automated radio interference filters where each event was presented as a set of stacked dynamic spectra. Despite manually inspecting each diagram for a signal of interest, all events were attributed to terrestrial radio frequency interference.