Context. Although substantial progress has been made in reconciling lambda cold dark matter (Lambda CDM) simulations with the observed abundance and distribution of satellite galaxies, important tensions persist. Studying satellite systems around spiral galaxies thus remains key to addressing these tensions. Aims. In this series of papers, we report the first results of an ongoing systematic survey, using Dark Energy Camera images, of faint dwarf spheroidal galaxies in the vicinity of the bright late-type spiral NGC 253 galaxy, the brightest member of the Sculptor filament located at a distance of 3.7 Mpc towards Anti-Virgo. Methods. We performed a new NGC 253 satellite search by means of visual inspection, using reprocessed co-added image cutouts from the DESI Legacy image surveys, reaching a very low surface brightness regime (28.0-29.0 mag arcsec(-2)). We used GALFIT software to derive the photometric and structural properties of the five dwarf galaxy candidates. Results. Five new dwarf galaxy candidates have been discovered in the vicinity of NGC 253, which we named Do V, Do VI, Do VII, Do VIII, and Do IX. Assuming that they are associated with NGC 253, their total absolute V-magnitudes fall in the -7 to -9 mag range, which is typical for dwarf satellites in the local Universe. The central surface brightness tends to be extremely low for all the discovered dwarfs and falls roughly in the range of 25-26 mag arcsec(-2) in the g band. We present a new list of galaxy candidates located around the giant spiral NGC 253. Conclusions. With the inclusion of these additional satellite candidates, the overall spatial distribution of the system becomes less flattened and is now broadly consistent with the analogues drawn from the Lambda CDM expectations. Interestingly, the distribution appears to be rather lopsided. However, firm conclusions about the presence or absence of a correlated satellite structure are hampered, as distance information is lacking, the census of observed dwarfs in the system remains far from complete, and spectroscopic velocities are not even available for most known satellites.

Context. Stellar substructures within tidal debris preserve information about their progenitor galaxies’ properties, offering insights into hierarchical mass assembly. Aims. We examine a compact stellar system (CSS) around the nearby spiral galaxy NGC 7531, including the shell-like tidal debris around it. Our goals are to determine the nature of the CSS, reconstruct the accretion history, and understand how the large, diffuse shell-like structure formed. Methods. We present photometric measurements of the shell-like debris and CSS using DESI Legacy Imaging Survey (LS) data. We obtained Keck/LRIS spectroscopic data for the CSS to confirm its association with NGC 7531 and to derive its star formation history (SFH). Deep (∼27.9 mag/arcsec 2 ) amateur telescope images enabled us to make a complete characterisation of the tidal debris structure. Results. We confirm that the CSS is associated with NGC 7531. We rename it NGC 7531-UCD1, since its stellar mass (6050 +460 −630 M ⊙ ), half-light radius ( R h = 0.13 ± 0.05 arcsec), and SFH place it as an ultra-compact dwarf galaxy (UCD). We find that NGC 7531-UCD1 experienced a star formation burst ∼1 Gyr ago. NGC 7531-UCD1 was likely a nuclear star cluster (NSC) that was tidally stripped into a UCD- this is further supported by the presence of tidal tails. We quantify the shell-like debris’ mass as M ★ ∼ 3–11 × 10 8 M ⊙ , implying a merger mass ratio of ∼300:1 to 10:1. Our amateur telescope images confirm new pieces of tidal debris, previously unclear in the DESI LS images. N-body simulations reproduce the tidal features, and require a near radial orbit of the progenitor dwarf galaxy with two pericentric passages. The first pericentre passage coincides with the measured star formation enhancement ∼1 Gyr ago. Conclusions. Our findings agree with theoretical predictions about the NSC to UCD formation pathway via tidal stripping, and further confirm the presence of these objects outside of our Milky Way.

We present a catalog of 4539 fast radio bursts (FRBs) observed with the Canadian Hydrogen Intensity Mapping Experiment telescope between 2018 July 25 and 2023 September 15. These bursts originate from 3641 unique sources, including 981 bursts from 83 known repeating sources. For each FRB, the catalog provides an O(10 ') estimate of sky location along with corresponding measurements of cumulative exposure time and survey sensitivity over the observing period. It includes a total-intensity dynamic spectrum between 400 and 800 MHz at 0.983 ms resolution. From this spectrum, we constrain a model of the burst morphology and measure key parameters such as arrival time, intrinsic temporal width, dispersion measure, scattering time, and flux density. This second catalog includes all FRBs from the first catalog, with every event reprocessed using a uniform and improved analysis framework. We show that previously published inferences remain valid under the updated measurements. We assess consistency of the detection rate across observational parameters, present initial distributions of burst properties, and outline ongoing and future studies that will use this catalog to investigate the nature of FRBs and their utility as astrophysical and cosmological probes.

Most massive stars (∼8–25 M _⊙ ) interact with a binary companion during their lifetimes. These interactions can remove the hydrogen-rich envelope, producing intermediate-mass (∼2–8 M _⊙ ) and helium-rich stars. These “stripped stars” are predicted to emit predominantly in the ultraviolet (UV) and can therefore be identified via a UV excess—provided they are not outshone by their companion. However, despite their importance to binary evolution, supernovae, and ionizing feedback, few stripped stars have been confirmed. This is likely due to the scarcity of wide-field, high angular-resolution, UV surveys of stellar populations with reliable distances and extinction estimates. To address this, we present the Stripped-Star Ultraviolet Magellanic Clouds Survey catalog. We use the Tractor forward modeling software to perform point-spread function photometry on 2420 Swift UVOT images of the LMC and SMC. The resulting catalog contains 734,862 sources in three UV filters to a depth of ∼20 Vega mag. We perform validation tests on the photometry pipeline and highlight the catalog’s broad applicability. We then identify sources with excess UV light compared to main-sequence stars and apply a series of quality cuts. From this, we identify 522 candidate stripped stars in the LMC and 298 in the SMC. We assess the potential contamination from other UV excess systems and argue the dominant uncertainty to be dust: early main-sequence stars can mimic the colors of stripped-star binaries when extinction is overcorrected. This survey lays the groundwork for the first systematic census of stripped stars and opens new windows into binary evolution and massive star populations.

We present the spatial part of the point source signal extraction strategy for the upcoming CHORD galaxy survey. CHORD, the Canadian Hydrogen Observatory and Radio-transient Detector, is an under-construction drift-scanning compact interferometric radio telescope. CHORD comprises 512 six meter dishes and observes in the 300 to 1500 MHz frequency range. One of its science goals is producing a catalogue of galaxies detected by the neutral hydrogen (HI) 21 cm emission line. CHORD's highly redundant dish layout creates the problem of spatial aliasing, the effect where the same signal could be feasibly produced from sources at multiple locations on the sky. The search will be done with a matched filter in the visibility plane. This paper presents the search strategy and a prediction tool that can quickly estimate the matched filter response at a given sky position, allowing a prediction of alias locations and severity. This tool confirms that although aliases are impossible to distinguish in a single snapshot, they become possible to distinguish when combining data over a period of time. It predicts that aliases will be harder to distinguish for observations closer to the celestial equator, but that scanning with offset adjacent strips can remove this degeneracy. It predicts that the optimal strategy for a single offset to disambiguate aliases is to re-point the array in declination by about two degrees. A future paper will combine these findings with realistic noise estimates and galaxy population statistics to make forecasts of the population of galaxies that CHORD will detect.

We have combined Wide-field Infrared Survey Explorer (WISE) and NEOWISE science exposures spanning from 2010 January through 2024 July to create the deepest ever full-sky maps at 3.4 μ m (W1) and 4.6 μ m (W2). These maps, which we publicly release, are based on ∼11.5 yr of WISE and NEOWISE observations in each of these two bands. As our new all-sky set of full-depth unWISE coadds uniformly incorporates observations from the entirety of the WISE and NEOWISE missions, it represents a valuable legacy dataset for Galactic and extragalactic astronomy in the infrared.

Context. Local primordial non-Gaussianities, characterized by the parameter f(NL)(loc), provide a powerful window into the physics of inflation. Cross-correlating high-redshift tracer samples with the Cosmic Microwave Background (CMB) lensing potential offers a particularly robust probe of floc NL , mitigating imaging systematics that typically affect large-scale measurements from tracer auto-spectra. In this context, the Ultraviolet Near Infrared Optical Northern Survey (UNIONS) enables the selection of u-dropout highredshift Lyman-break galaxies (LBGs). Aims. We aim to forecast the expected precision on f(NL)(loc)that is achievable from analyzing the cross-correlation power spectrum between the distribution of UNIONS-selected LBGs and the CMB lensing potential measured by the Planck satellite. Methods. We performed a Markov chain Monte Carlo forecast to estimate the uncertainties on f(NL)(loc)and on a galaxy bias parameter b0, which captured our uncertainty in the tracer bias. Results. We forecast sigma(f(NL)(loc)) = 34 for an idealized photometric sample of r < 24.3 LBGs selected with a Random Forest classification algorithm from UNIONS-like ugriz imaging, with a resulting surface density of 1100 deg(-2) over 3730 deg(2). This precision can be improved to sigma(floc NL) = 20 after spectroscopic follow-up with the Dark Energy Spectroscopic Instrument (DESI), during its next phase starting in 2029, DESI-II. We also tested a more realistic selection using early UNIONS data, based on a u-dropout color cut over the ugr imaging, which yields a denser sample of r < 24.2 objects at 1400 deg(-2 )over 4760 deg(2). From this sample-covering a larger footprint and expected to have a higher large-scale galaxy bias-we forecast an improved constraint of sigma(floc NL) = 20, with a similar precision that is achievable after DESI-II follow-up. In addition, we performed a preliminary validation of the redshift distribution using the clustering-redshift method with DESI DR1 data, confirming the calibration from deep, small-area photometric fields. However, accounting for uncertainties in the clustering-redshift distribution significantly degrades the f(NL)(loc) constraining power.

Context. Although substantial progress has been made in reconciling lambda cold dark matter (ΛCDM) simulations with the observed abundance and distribution of satellite galaxies, important tensions persist. Studying satellite systems around spiral galaxies thus remains key to addressing these tensions. Aims. In this series of papers, we report the first results of an ongoing systematic survey, using Dark Energy Camera images, of faint dwarf spheroidal galaxies in the vicinity of the bright late-type spiral NGC 253 galaxy, the brightest member of the Sculptor filament located at a distance of 3.7 Mpc towards Anti-Virgo. Methods. We performed a new NGC 253 satellite search by means of visual inspection, using reprocessed co-added image cutouts from the DESI Legacy image surveys, reaching a very low surface brightness regime (28.0–29.0 mag arcsec−2). We used GALFIT software to derive the photometric and structural properties of the five dwarf galaxy candidates. Results. Five new dwarf galaxy candidates have been discovered in the vicinity of NGC 253, which we named Do V, Do VI, Do VII, Do VIII, and Do IX. Assuming that they are associated with NGC 253, their total absolute V-magnitudes fall in the −7 to −9 mag range, which is typical for dwarf satellites in the local Universe. The central surface brightness tends to be extremely low for all the discovered dwarfs and falls roughly in the range of 25–26 mag arcsec−2 in the g band. We present a new list of galaxy candidates located around the giant spiral NGC 253. Conclusions. With the inclusion of these additional satellite candidates, the overall spatial distribution of the system becomes less flattened and is now broadly consistent with the analogues drawn from the ΛCDM expectations. Interestingly, the distribution appears to be rather lopsided. However, firm conclusions about the presence or absence of a correlated satellite structure are hampered, as distance information is lacking, the census of observed dwarfs in the system remains far from complete, and spectroscopic velocities are not even available for most known satellites.

Ly α blobs (LABs) are large, spatially extended Ly α -emitting objects whose nature remains unclear. Their statistical properties, such as number densities and luminosity functions, are still uncertain because of small sample sizes and large cosmic variance. The One-hundred-deg ^2 DECam Imaging in Narrowbands (ODIN) survey, with its large volume, offers an opportunity to overcome these limitations. We describe our LAB selection method and present 112 new LABs in the 9 deg ^2 E-COSMOS field. We begin with the conventional LAB selection approach, crossmatching Ly α -emitting galaxies with extended Ly α sources, yielding 89 LAB candidates. To obtain a more complete LAB sample, we introduce a new selection pipeline that models all galaxies detected in deep broadband imaging, subtracts them from the narrowband image, and then directly detects extended Ly α emission. This method successfully identifies 23 additional low-SB LABs, which could otherwise be missed by the conventional method. The number density of ODIN LABs near an ODIN protocluster ( n = 7.5 × 10 ^−5 cMpc ^−3 ) is comparable to that found in the SSA22 protocluster and is 4 times higher than the average across the field. The cumulative Ly α luminosity function within the protocluster regions is similar to that measured for the LABs in the SSA22 protocluster, suggesting a large excess of luminous LABs relative to the average field. These findings suggest the Ly α luminosities and number densities of LABs are environment-dependent. ODIN will provide an expansive LAB and protocluster samples across six additional fields and two more redshifts, allowing us to investigate the nature of LABs in relation to their environments.

We present a clustering analysis of Lyman-α emitters (LAEs) using spectroscopic observations from the Dark Energy Spectroscopic Instrument (DESI) of candidates selected from the Blanco/DECam Intermediate-Band Imaging Survey (IBIS). We measure the two-point correlation function and the power spectrum, including cross-correlations with DESI quasars. Using both analytical and halo occupation distribution (HOD) simulation-based modeling, we find a linear bias of b ∼ 2.31–2.62 for LAEs over the redshift range 2.26 < z < 3.41. The analytical modeling also provides constraints on the strength of radiative transfer effects, while the HOD analysis characterizes the LAE-halo connection across multiple models. Finally, we quantify the magnitude of non-perturbative clustering effects such as Fingers of God in the LAE population, providing essential input for the accurate modeling of LAE-based cosmological analyses in forthcoming high-redshift surveys such as DESI-II.

There is almost no data analysis operation more important to astronomy than the detection of sources (stars or galaxies, say) in imaging. Here we write down a set of reasonable assumptions for well-understood (or well-calibrated) background-dominated imaging (faint sources) and find the detection methods that flow from those assumptions. Our methods are hypothesis comparisons, involving matched filters. We show that they are generally preferable to one-hypothesis ( p -value or n -sigma-deviation) methods, especially for avoiding spurious detection of nonstar image features. We consider the case in which there are multiple images at each point on the sky, and—more importantly for our purposes—when those images are taken through different bandpasses. Detection in multiband imaging involves making choices about the range of colors or spectral energy distributions to which the method will be most sensitive; we deliver methods based on Bayesian decision theory and also frequentist methods that deliver similar outcomes in real-data tests. We discuss relationships between these methods and standard practices. The methods we present perform well, but our main point is that methods should be principled—that is, they should flow from our fundamental assumptions about the data.

The Canadian Hydrogen Observatory and Radio-transient Detector (CHORD) is a next-generation wideband radio interferometer currently being constructed and commissioned at the Dominion Radio Astrophysical Observatory in British Columbia, Canada. CHORD is designed for precision 21 cm cosmology, fast radio transient discovery, spectral line galaxy surveys, and pulsar science using a highly redundant large-N, small-diameter drift-scan array architecture. The telescope consists of a 512-element core array of 6 m dishes operating from 300–1500 MHz in drift-scan mode, together with two 64-dish outrigger stations located at the Hat Creek Radio Observatory and the Green Bank Observatory for long-baseline transient localization. The instrument supports multiple simultaneous digital backends for interferometric correlation, FRB detection, pulsar beamforming, and high spectral resolution surveys. CHORD is designed with an emphasis on precision beam control and stable instrumental response, incorporating lessons learned from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) while providing a substantial increase in sensitivity. Initial performance has been evaluated using a three-dish engineering array, and a 64-dish pathfinder array is currently being commissioned. The full array will be commissioned in 2028.

We use the forward modeling pipeline, Obiwan, to study the imaging systematics of the Luminous Red Galaxies (LRGs) targeted by the Dark Energy Spectroscopic Instrument (DESI). We update the Obiwan pipeline, which had previously been developed to simulate the optical images used to target DESI data, to further simulate WISE images in the infrared. This addition makes it possible to simulate the DESI LRGs sample, which utilizes WISE data in the target selection. Deep DESI imaging data combined with a method to account for biases in their shapes is used to define a truth sample of potential LRG targets. We simulate a total of 15 million galaxies to obtain a simulated LRG sample (Obiwan LRGs) that predicts the variations in target density due to imaging properties. We find that the simulations predict the trends with depth observed in the data, including how they depend on the intrinsic brightness of the galaxies. We observe that faint LRGs are the main contributing power of the imaging systematics trend induced by depth. We also find significant trends in the data against Galactic extinction that are not predicted by Obiwan. These trends depend strongly on the particular map of Galactic extinction chosen to test against, implying Large-Scale Structure systematic contamination (e.g. Cosmic-Infrared Background) in the Galactic extinction maps is a likely root cause. We additionally observe that the DESI LRGs sample exhibits a complex dependency on a combination of seeing, depth, and intrinsic galaxy brightness, which is not replicated by Obiwan, suggesting discrepancies between the current simulation settings and the actual observations. The detailed findings we present should be used to guide any observational systematics mitigation treatment for the clustering of the DESI LRG sample.

The Panchromatic Hubble Andromeda Southern Treasury (PHAST) is a large 195-orbit Hubble Space Telescope program imaging ∼0.45 deg 2 of the southern half of M31's star-forming disk at optical and near-ultraviolet (NUV) wavelengths. The PHAST survey area extends the northern coverage of the Panchromatic Hubble Andromeda Treasury (PHAT) down to the southern half of M31, covering out to a radius of ∼13 kpc along the southern major axis and in total ∼two-thirds of M31's star-forming disk. This new legacy imaging yields stellar photometry of over 90 million resolved stars using the Advanced Camera for Surveys in the optical (F475W and F814W), and the Wide Field Camera 3 (WFC3) in the NUV (F275W and F336W). The photometry is derived using all overlapping exposures across all bands, and achieves a 50% completeness-limited depth of F475W ∼ 27.7 in the lowest surface density regions of the outer disk and F475W ∼ 26.0 in the most crowded, high surface brightness regions near M31's bulge. We provide extensive analysis of the data quality, including artificial star tests to quantify completeness, photometric uncertainties, and flux biases, all of which vary due to the background source density and the number of overlapping exposures. We also present seamless population maps of the entire M31 disk, which show relatively well-mixed distributions for stellar populations older than 1–2 Gyr, and highly structured distributions for younger populations. The combined PHAST + PHAT photometry catalog of ∼0.2 billion stars is the largest ever produced for equidistant sources and is available for public download by the community.

In this paper, we investigate the possibility of selecting high-redshift Lyman-Break Galaxies (LBG) using current and future broadband wide photometric surveys, such as the Ultraviolet Near Infrared Optical Northern Survey (UNIONS) or the Vera C. Rubin Legacy Survey of Space and Time (LSST), using a Random Forest algorithm. This work is conducted in the context of future large-scale structure spectroscopic surveys like DESI-II, the next phase of the Dark Energy Spectroscopic Instrument (DESI), which will start around 2029. We use deep imaging data from the Hyper Suprime Camera (HSC) and the Canada-France-Hawaii Telescope Large Area U-band Deep Survey (CLAUDS) on the COSMOS and XMM-LSS fields. To predict the selection performance of LBGs with image quality similar to UNIONS, we degrade the u,g,r,i and z bands to UNIONS depth. The Random Forest algorithm is trained with the u,g,r,i and z bands to classify LBGs in the 2.5 < z < 3.5 range. We find that fixing a target density budget of 1,100 deg -2 , the Random Forest approach gives a density of z > 2 targets of 873 deg -2 , and a density of 493 deg -2 of confirmed LBGs after spectroscopic confirmation with DESI. This UNIONS-like selection was tested in a dedicated spectroscopic observation campaign of 1,000 targets with DESI on the COSMOS field, providing a safe spectroscopic sample with a mean redshift of 3. This sample is used to derive forecasts for DESI-II, assuming a sky coverage of 5,000 deg 2 . We predict uncertainties on Alcock-Paczynski parameters α ⊥ and α ∥ to be 0.7% and 1% for 2.6 < z < 3.2, resulting in a potential 2% measurement of the dark energy fraction at high redshift. Additionally, we estimate the uncertainty in local non-Gaussianity and predict σ f NL ≈ 7, which would be comparable to the current best precision achieved by Planck . The latter forecast suggests that achieving the precision required to place stringent constraints on inflationary models ( σ f NL ≈ 1) using spectroscopic galaxy surveys necessitates the development of a next-generation (Stage V) spectroscopic survey.

We describe the CHIME All-sky Multiday Pulsar Stacking Search (CHAMPSS) project. This novel radio pulsar survey revisits the full Northern Sky daily, offering unprecedented opportunity to detect highly intermittent pulsars, as well as faint sources via long-term data stacking. CHAMPSS uses the CHIME/FRB datastream, which consists of 1024 stationary beams streaming intensity data at 0.983 ms resolution, 16384 frequency channels across 400–800 MHz, continuously being searched for single, dispersed bursts/pulses. In CHAMPSS, data from adjacent east-west beams are combined to form a grid of tracking beams, allowing longer exposures at fixed positions. These tracking beams are dedispersed to many trial dispersion measures (DM) to a maximum DM beyond the Milky Way's expected contribution, and Fourier transformed in time to form power spectra. Repeated observations are searched daily to find intermittent sources, and power spectra of the same sky positions are incoherently stacked, increasing sensitivity to faint persistent sources. The 0.983 ms time resolution limits our sensitivity to millisecond pulsars; we have full sensitivity to pulsars with P > 60ms, with sensitivity gradually decreasing from 60 ms to 2 ms as higher harmonics are beyond the Nyquist limit. In a commissioning survey, data covering ∼ 1/16 of the CHIME sky was processed and searched in quasi-realtime over two months, leading to the discovery of eleven new pulsars, each with S_600 > 0.1 mJy. When operating at scale, CHAMPSS will stack >1 year of data along each sightline, reaching a sensitivity of ≲ 30 μJy for all sightlines above a declination of 10^∘, and off of the Galactic plane.

We present the measurements and cosmological implications of the galaxy two-point clustering using over 4.7 million unique galaxy and quasar redshifts in the range 0.1 < z < 2.1 divided into six redshift bins over a similar to 7, 500 square degree footprint, from the first year of observations with the Dark Energy Spectroscopic Instrument (DESI Data Release 1). By fitting the full power spectrum, we extend previous DESI DR1 baryon acoustic oscillation (BAO) measurements to include redshift-space distortions and signals from the matter-radiation equality scale. For the first time, this Full-Shape analysis is blinded at the catalogue-level to avoid confirmation bias and the systematic errors are accounted for at the two-point clustering level, which automatically propagates them into any cosmological parameter. When analysing the data in terms of compressed model-agnostic variables, we obtain a combined precision of 4.7% on the amplitude of the redshift space distortion (RSD) signal reaching a similar precision with just one year of DESI data than with twenty years of observation from the previous generation survey. We also analyse the data to directly constrain the cosmological parameters within the Lambda CDM model using perturbation theory and combine this information with the reconstructed DESI DR1 galaxy BAO. Using a Big Bang Nucleosynthesis Gaussian prior on the baryon density parameter, omega(b), and a weak Gaussian prior on the spectral index, n(s), we constrain the matter density is Omega(m) = 0.296 +/- 0.010 and the Hubble constant H-0 = (68.63 +/- 0.79)[km s(-1)Mpc(-1)]. Additionally, we measure the amplitude of clustering sigma(8) = 0.841 +/- 0.034. The DESI DR1 galaxy clustering results are in agreement with the Lambda CDM model based on general relativity with parameters consistent with those from Planck. The cosmological interpretation of these results in combination with DESI DR1 Ly-alpha forest data and external datasets are presented in the companion paper [1].

Tidal features from galaxy mergers, particularly stellar streams, offer valuable insights into galaxy assembly and dark matter halo properties. This paper aims to identify a large sample of nearby stellar streams suitable for detailed modelling and comparison with simulations to enable population-level constraints on halo properties. We visually inspect and compile a tidal feature catalogue for 19,387 galaxies with redshift z <= 0.02 from the Siena Galaxy Atlas 2020 using original, model, and residual images from the DESI Legacy Imaging Surveys. Residual images, produced by subtracting models of all sources, enhance the detectability of faint asymmetries such as tidal features. We find that 11.9 +/- 0.2% of galaxies host detectable tidal features, more frequently around early-type than late-type galaxies. The tidal feature fraction increases with stellar mass, from 2.4 +/- 0.4% at similar to 10(8 )M(circle dot )to 36.5 +/- 1.2% at similar to 5 x 10(11) M-circle dot. From this, we present the first release of STRRINGS: STReams in Residual Images of Nearby GalaxieS, a subsample of 35 galaxies with long, narrow streams suitable for modelling. We segment these streams and derive their geometry, surface brightness, colours, and stellar masses. The median g-band surface brightness is 26.8 mag arcsec(-2), reaching 27.5 mag arcsec(-2) for the faintest stream. Mass ratios are consistent with minor mergers, and we identify five potential dwarf galaxy progenitors. Our streams are typically longer (median 124 kpc) than the literature, with comparable widths. Stream mass correlates with length and colour, and wider streams lie at larger galactocentric radii. STRRINGS will be expanded and used to constrain halo properties in future work.

We describe the Canadian Hydrogen Intensity Mapping Experiment (CHIME) All-sky Multiday Pulsar Stacking Search (CHAMPSS) project. This novel radio pulsar survey revisits the full northern sky daily, offering unprecedented opportunity to detect highly intermittent pulsars, as well as faint sources via long-term data stacking. CHAMPSS uses the CHIME/FRB datastream, which consists of 1024 stationary beams streaming intensity data at 0.983 ms resolution, with 16,384 frequency channels across 400–800 MHz, continuously being searched for single, dispersed bursts/pulses. In CHAMPSS, data from adjacent east–west beams are combined to form a grid of tracking beams, allowing longer exposures at fixed positions. These tracking beams are dedispersed to many trial dispersion measures (DM) to a maximum DM beyond the Milky Way’s expected contribution, and Fourier transformed in time to form power spectra. Repeated observations are searched daily to find intermittent sources, and power spectra of the same sky positions are incoherently stacked, increasing sensitivity to faint persistent sources. The 0.983 ms time resolution limits our sensitivity to millisecond pulsars; we have full sensitivity to pulsars with P > 60 ms, with sensitivity gradually decreasing from 60 ms to 2 ms, as higher harmonics are beyond the Nyquist limit. In a commissioning survey, data covering ∼1/16 of the CHIME sky were processed and searched in quasi-realtime over two months, leading to the discovery of 11 new pulsars, each with S _600 > 0.1 mJy. When operating at scale, CHAMPSS will stack >1 yr of data along each sightline, reaching a sensitivity of ≲30 μ Jy for all sightlines above a decl. of 10°, and off of the Galactic plane.

We present cosmological results from the measurement of baryon acoustic oscillations (BAO) in galaxy, quasar and Lyman-$\alpha$ forest tracers from the first year of observations from the Dark Energy Spectroscopic Instrument (DESI), to be released in the DESI Data Release 1. DESI BAO provide robust measurements of the transverse comoving distance and Hubble rate, or their combination, relative to the sound horizon, in seven redshift bins from over 6 million extragalactic objects in the redshift range $0.1-1$ and $w_a<0$. This preference is 2.6$\sigma$ for the DESI+CMB combination, and persists or grows when SN~Ia are added in, giving results discrepant with the $\Lambda$CDM model at the $2.5\sigma$, $3.5\sigma$ or $3.9\sigma$ levels for the addition of Pantheon+, Union3, or DES-SN5YR datasets respectively. For the flat $\Lambda$CDM model with the sum of neutrino mass $\sum m_\nu$ free, combining the DESI and CMB data yields an upper limit $\sum m_\nu < 0.072$ $(0.113)$ eV at 95% confidence for a $\sum m_\nu>0$ $(\sum m_\nu>0.059)$ eV prior. These neutrino-mass constraints are substantially relaxed in models beyond $\Lambda$CDM. [Abridged.]