Context. As tracers of the underlying mass distributions, the peculiar velocities of galaxies are valuable probes of the Universe, allowing us to measure the Hubble constant or to map the large-scale structure and its dynamics. The catalogs of peculiar velocities, however, are noisy, scarce, and prone to various interpretation biases. Aims. We measured the radial and bulk flow directly from the largest available sample of peculiar velocities and did not impose a cosmological prior on the velocity field. Furthermore, a minimum assumption on the shape of the radial flow at large distances enabled us to estimate the local Hubble constant. Methods. To address these issues, we analyzed the Cosmicflows-4 catalog (CF4), the most extensive catalog of galaxy peculiar velocities, reaching a redshift z = 0.1. Specifically, we constructed a forward-modeling approach assuming only a flat Universe, which reconstructs the radial and bulk flows of the velocity field directly from measurements of peculiar velocities. Our method was tested on a series of 64 simulated catalogs that mimicked the complex selection function of CF4 in space and in magnitude. Based on our mock data, we propose a simulation-based correction method that we applied to the CF4 data. Results. Our method recovers the radial flow and the direction and magnitude of the bulk flow throughout the covered volume without bias. The incompleteness of the data leads to a systematic amplification of the underlying flow, however, which in turn leads to a systematic overestimation of the amplitude of the bulk flow. By estimating the (cosmic) variance of the density field at large distances from the Lambda Cold Dark Matter (ΛCDM) model, we were able to extract a value of 75.9 ± 1 (stat) km/s/Mpc from the radial inflow. With regard to the bulk flow, a 3σ tension is found with ΛCDM on the supergalactic X direction and on the magnitude of the bulk flow around 140 Mpc/h and 240 Mpc/h. In summary, our work confirms the existing tension on the Hubble constant measured locally and a significant tension in the local bulk flow with ΛCDM predictions. More work is needed to handle all the possible sources of systematic errors inherent to the treating of composite catalogs such as CF4.
Euclid is currently mapping the distribution of matter in the Universe in detail via the weak lensing signature of billions of distant galaxies. The weak lensing signal is most prominent around galaxy clusters and can extend up to distances well beyond their virial radius, thus constraining their total mass. Near the centre of clusters, where contamination by member galaxies is an issue, the weak lensing data can be complemented with strong lensing data. Strong lensing information can also diminish the uncertainty due to the mass-sheet degeneracy and provide high-resolution information about the distribution of matter in the centre of clusters. Here we present a joint strong and weak lensing analysis of the Euclid Early Release Observations of the cluster Abell 2390 at z = 0.228. Thanks to Euclid’s wide field of view of 0.5 deg2, combined with its angular resolution in the visible band of 0.″13 and sampling of 0.″1 per pixel, we constrained the density profile in a wide range of radii, 30 kpc < r< 2000 kpc, from the inner region near the brightest cluster galaxy to beyond the virial radius of the cluster. We find relatively good consistency with earlier X-ray results based on assumptions of hydrostatic equilibrium and thus indirectly confirm the nearly relaxed state of this cluster. We also find consistency with previous results based on weak lensing data and ground-based observations of this cluster. From the combined strong + weak lensing profile, we derive the values of the viral mass M200 = (1.48 ± 0.29) × 1015 M⊙, and virial radius r200 = (2.05 ± 0.13 Mpc), with error bars representing one standard deviation. The profile is well described by a Navarro-Frenk-White model with a concentration c = 6.5 and a small-scale radius of 230 kpc in the 30 kpc < r< 2000 kpc range that is best constrained by strong lensing and weak lensing data. Abell 2390 is the first of many examples where Euclid data will play a crucial role in providing masses for clusters. The large coverage provided by Euclid, combined with the depth of the observations and high angular resolution, will allow us to produce similar results in hundreds of other clusters with rich strong lensing data that is already available.
We introduce a fast method to measure the conversion gain in complementary metal-oxide-semiconductor active pixel sensors, which accounts for nonlinearity and interpixel capacitance (IPC). The standard “mean-variance” method is biased because it assumes that pixel values depend linearly on the signal, and existing methods to correct for nonlinearity still introduce significant biases. While current IPC correction methods are prohibitively slow for a per-pixel application, our new method uses separate measurements of the IPC kernel to calculate the gain almost instantaneously. Using test data from a flight detector of the ESA Euclid mission, the IPC correction recovers the results of slower methods with 0.1% accuracy. The nonlinearity correction ensures that the estimated gain is independent of signal, correcting a bias of more than 2.5%.
We report the first result from a dark photon dark matter search in the mass range from 78.62 to 83.95 μeV/c2 with a dielectric haloscope prototype for (Magnetized Disc and Mirror Axion eXperiment). Putative dark photons would convert to detectable photons within a stack consisting of three sapphire disks and a mirror. The emitted power of this system is received by an antenna and successively digitized using a low-noise receiver. No significant signal attributable to dark photons has been observed above the expected background. Assuming unpolarized dark photon dark matter with a local density of ρχ=0.3 GeV cm3 we exclude a dark photon to photon mixing parameter χ>2.7×10−12 over the full mass range and χ>1.1×10−13 at a mass of 80.57 μeV/c2 with a 95% confidence level. This is the first physics result from a prototype and exceeds previous constraints on χ in this mass range by up to almost three orders of magnitude.
The Jiangmen Underground Neutrino Observatory (JUNO) started physics data taking on 26 August 2025. JUNO consists of a 20-kton liquid scintillator central detector, surrounded by a 35 kton water pool serving as a Cherenkov veto, and almost 1000 m$^2$ of plastic scintillator veto on top. The detector is located in a shallow underground laboratory with an overburden of 1800 m.w.e. This paper presents the performance results of the detector, extensively studied during the commissioning of the water phase, the subsequent liquid scintillator filling phase, and the first physics runs. The liquid scintillator achieved an attenuation length of 20.6 m at 430 nm, while the high coverage PMT system and scintillator together yielded about 1785 photoelectrons per MeV of energy deposit at the detector centre, measured using the 2.223 MeV $γ$ from neutron captures on hydrogen with an Am-C calibration source. The reconstructed energy resolution is 3.4% for two 0.511 MeV $γ$ at the detector centre and 2.9% for the 0.93 MeV quenched Po-214 alpha decays from natural radioactive sources. The energy nonlinearity is calibrated to better than 1%. Intrinsic contaminations of U-238 and Th-232 in the liquid scintillator are below 10$^{-16}$ g/g, assuming secular equilibrium. The water Cherenkov detector achieves a muon detection efficiency better than 99.9% for muons traversing the liquid scintillator volume. During the initial science runs, the data acquisition duty cycle exceeded 97.8%, demonstrating the excellent stability and readiness of JUNO for high-precision neutrino physics.
