Explanipedia

The Velocity Field Olympics: Assessing velocity field reconstructions with direct distance tracers Open

Richard Stiskalek, Harry Desmond, Julien Devriendt, Adrianne Slyz, Guilhem Lavaux , et al. · 2025

The peculiar velocity field of the local Universe provides direct insights into its matter distribution and the underlying theory of gravity, and is essential in cosmological analyses for modelling deviations from the Hubble flow. Numerous…

Euclid: An emulator for baryonic effects on the matter bispectrum Open

P.A Burger, Giovanni Aricò, Laila Linke, Raúl E. Angulo, Jeger C. Broxterman , et al. · 2025

The Euclid mission and other next-generation large-scale structure surveys will enable high-precision measurements of the cosmic matter distribution. Understanding the impact of baryonic processes such as star formation and active galactic…

Unions with UNIONS: Using Galaxy–Galaxy Lensing to Probe Galaxy Mergers Open

Isaac Cheng, J. Elvin-Poole, Michael J. Hudson, Ruxin Barré, Sara L. Ellison , et al. · 2025

We use galaxy–galaxy lensing to investigate how the dark matter (DM) haloes and stellar content of galaxies with 0.012 ≤ z ≤ 0.32 and change as a result of the merger process. To this end, we construct two samples of galax…

Cosmology from UNIONS weak lensing profiles of galaxy clusters Open

Charlie T. Mpetha, James E. Taylor, Yuba Amoura, Roan Haggar, Thomas de Boer , et al. · 2025

Cosmological information is encoded in the structure of galaxy clusters. In Universes with less matter and larger initial density perturbations, clusters form earlier and have more time to accrete material, leading to a more extended infal…

Uncertainties in the Hubble constant from peculiar velocities Open

Amber M. Hollinger, Michael J. Hudson · 2025

Recent measurements of the Hubble constant using type Ia supernovae explicitly correct for their estimated peculiar velocities using the 2M++ reconstruction of the local density field. The amount of uncertainty from this reconstruction pro…

Lensing without mass: The matter density profile in cosmic voids from UNIONS Open

H. M. Martin, Michael J. Hudson, Alex Woodfinden, Lucie Baumont, Thomas de Boer , et al. · 2025

We measure the distribution of matter contained within the emptiest regions of the Universe: cosmic voids. We use the large overlap between the Ultraviolet Near-Infrared Optical Northern Survey (UNIONS) and voids identified in the LOWZ and…

JWST Reveals a Likely Jellyfish Galaxy at z=1.156 Open

Ian Roberts, Michael L. Balogh, Visal Sok, Adam Muzzin, Michael J. Hudson , et al. · 2025

We report the discovery of COSMOS2020-635829 as a likely jellyfish galaxy undergoing to ram pressure stripping in a (proto)cluster at $z > 1$. High-resolution imaging from the James Webb Space Telescope reveals a symmetric stellar disk cou…

Truncated Star Formation and Ram Pressure Stripping in the Coma Cluster Open

Ariel O. Broderick, Ian Roberts, Michael J. Hudson · 2025

We use 45 galaxies from the Mapping Nearby Galaxies at Apache Point Observatory survey to study the physical drivers of star formation quenching in the Coma Cluster. We measure specific star formation rate (sSFR) radial profiles for the Co…

Galaxies OBserved as Low-luminosity Identified Nebulae (GOBLIN): Catalog of 43 000 high-probability dwarf galaxy candidates in the UNIONS survey Open

Nick Heesters, David Chemaly, Oliver Müller, Elisabeth Sola, S. Fabbro , et al. · 2025

The detection of low-surface-brightness galaxies beyond the Local Group poses significant observational challenges, yet these faint systems are fundamental to our understanding of dark matter, hierarchical galaxy formation, and cosmic stru…

High frequency ultrasound for pyoderma gangrenosum: A case series Open

Kristie Ross, Shivani Thacker, Michael J. Hudson, M. Shea, Alex G. Ortega‐Loayza · 2025

UNIONS: A direct measurement of intrinsic alignment with BOSS/eBOSS spectroscopy Open

Fabian Hervas Peters, M. Kilbinger, Romain Paviot, Lucie Baumont, Elisa Russier , et al. · 2025

Context. During their formation, galaxies are subject to tidal forces, which create correlations between their shapes and the large-scale structure of the Universe, known as intrinsic alignment. This alignment is a source of contamination …

Gravitational Lenses in UNIONS and Euclid (GLUE) I: A Search for Strong Gravitational Lenses in UNIONS with Subaru, CFHT, and Pan-STARRS Data Open

Christopher J. Storfer, E. A. Magnier, Xiaosheng Huang, D. Rubin, David J. Schlegel , et al. · 2025

We present the results of our pipeline for discovering strong gravitational lenses in the ongoing Ultraviolet Near-Infrared Optical Northern Survey (UNIONS). We successfully train the deep residual neural network (ResNet) based on CMU-Deep…

Deep in the Fields of the Andromeda Halo: Discovery of the Pegasus VII Dwarf Galaxy in UNIONS Open

Simon E. T. Smith, Alan W. McConnachie, Stephen Gwyn, Christian R. Hayes, M. Gatto , et al. · 2025

We present the newly discovered dwarf galaxy Pegasus VII (Peg VII), a member of the M31 subgroup which has been uncovered in the ri photometric catalogs from the Ultraviolet Near-Infrared Optical Northern Survey and confirmed with follow-u…

No Evidence of Asymmetrically Enhanced Star Formation in Infalling Galaxies in UNIONS Open

Lauren M. Foster, Laura C. Parker, Stephen Gwyn, Ian Roberts, James E. Taylor , et al. · 2025

Ram pressure stripping is a well-known environmental quenching mechanism that removes gas from galaxies infalling into groups and clusters. In some extreme examples of ram pressure stripping, galaxies with extended gas tails show evidence …

Searching for strong lensing by late-type galaxies in UNIONS Open

J.A. Acevedo Barroso, B. Clément, F. Courbin, R. Gavazzi, Cameron Lemon , et al. · 2025

Recent wide-field galaxy surveys have led to an explosion in numbers of galaxy-scale strong gravitational lens candidates. However, the vast majority feature massive luminous red galaxies as the main deflectors, with late-type galaxies bei…

No Evidence of Asymmetrically Enhanced Star Formation in Infalling Galaxies in UNIONS Open

Lauren M. Foster, Laura C. Parker, Stephen Gwyn, Ian Roberts, James E. Taylor , et al. · 2025

Ram pressure stripping is a well-known environmental quenching mechanism that removes gas from galaxies infalling into groups and clusters. In some extreme examples of ram pressure stripping, galaxies with extended gas tails show evidence …

Deep in the Fields of the Andromeda Halo: Discovery of the Pegasus VII dwarf galaxy in UNIONS Open

Simon E. T. Smith, Alan W. McConnachie, Stephen Gwyn, Christian R. Hayes, M. Gatto , et al. · 2025

We present the newly discovered dwarf galaxy Pegasus VII (Peg VII), a member of the M31 sub-group which has been uncovered in the $ri$ photometric catalogs from the Ultraviolet Near-Infrared Optical Northern Survey and confirmed with follo…

Unions with UNIONS: Using galaxy-galaxy lensing to probe galaxy mergers Open

Isaac Cheng, J. Elvin-Poole, Michael J. Hudson, Ruxin Barré, Sara L. Ellison , et al. · 2025

We use galaxy-galaxy lensing to investigate how the dark matter (DM) haloes and stellar content of galaxies with $0.012 \leq z \leq 0.32$ and $10 \leq \log_{10}(M_\star/\mathrm{M}_\odot) \leq 12$ change as a result of the merger process. T…

The Velocity Field Olympics: Assessing velocity field reconstructions with direct distance tracers Open

Richard Stiskalek, Harry Desmond, Julien Devriendt, Adrianne Slyz, Guilhem Lavaux , et al. · 2025

The peculiar velocity field of the local Universe provides direct insights into its matter distribution and the underlying theory of gravity, and is essential in cosmological analyses for modelling deviations from the Hubble flow. Numerous…

Uncertainties in the Hubble Constant from Peculiar Velocities Open

Amber M. Hollinger, Michael J. Hudson · 2025

Recent measurements of the Hubble constant using type Ia supernovae explicitly correct for their estimated peculiar velocities using the 2M++ reconstruction of the local density field. The amount of uncertainty from this reconstruction pro…

Galaxy-Point Spread Function correlations as a probe of weak-lensing systematics with UNIONS data Open

Sacha Guerrini, M. Kilbinger, Hubert Leterme, Axel Guinot, Jingwei Wang , et al. · 2024

Weak gravitational lensing requires precise measurements of galaxy shapes and therefore an accurate knowledge of the PSF model. The latter can be a source of systematics that affect the shear two-point correlation function. A key stake of …

Constraining cosmological parameters using density split lensing and the conditional stellar mass function Open

Pierre Burger, Darshan P. Patel, Michael J. Hudson · 2024

In this work, we develop a simulation-based model to predict the excess surface mass density (ESD) depending on the local density environment. Using a conditional stellar mass function, our foreground galaxies are tailored toward the brigh…

Cosmological parameters from the joint analysis of density split and second order statistics: An emulator based on the halo occupation distribution Open

Pierre Burger, E. Paillas, Michael J. Hudson · 2024

Selective Liquid–Liquid Extraction of Thorium(IV) from Rare-Earth Element Mixtures Open

Wyatt B. Larrinaga, Bailey J. Lake, Victoria D. Pacanowski, Michael G. Patterson, Michael J. Hudson , et al. · 2024

One of the major challenges in processing rare-earth element (REE) materials arises from the large amounts of radioactive thorium (Th) that are often found within REE minerals, encouraging enhanced metal separation procedures. We report he…

Black Hole–Halo Mass Relation from UNIONS Weak Lensing Open

Qinxun Li, M. Kilbinger, Wentao Luo, Kai Wang, Huiyuan Wang , et al. · 2024

This Letter presents, for the first time, direct constraints on the black hole–halo mass relation using weak gravitational-lensing measurements. We construct type I and type II active galactic nucleus (AGN) samples from the Sloan Digital S…

Cosmological parameters from the joint analysis of Density Split and Second Order Statistics: an Emulator based on the Halo Occupation Distribution Open

Pierre Burger, E. Paillas, Michael J. Hudson · 2024

In this work, we develop a simulation-based model to predict the density split (DSS) and second-order shear and clustering statistics. A simulation-based model has the potential to model highly non-linear scales where current DSS models fa…

Cosmological parameters estimated from peculiar velocity–density comparisons: calibrating 2M++ Open

Amber M. Hollinger, Michael J. Hudson · 2024

Cosmological parameters can be measured by comparing peculiar velocities with those predicted from a galaxy density field. Previous work has tested the accuracy of this approach with N-body simulations, but generally on idealized mock gala…

The Discovery of the Faintest Known Milky Way Satellite Using UNIONS Open

Simon E. T. Smith, W. Cerny, Christian R. Hayes, Federico Sestito, Jaclyn Jensen , et al. · 2024

We present the discovery of Ursa Major III/UNIONS 1, the least luminous known satellite of the Milky Way, which is estimated to have an absolute V -band magnitude of mag, equivalent to a total stellar mass of M ⊙ . Urs…

Cosmological parameters estimated from velocity -- density comparisons: Calibrating 2M++ Open

Amber M. Hollinger, Michael J. Hudson · 2023

Cosmological parameters can be measured by comparing peculiar velocities with those predicted from a galaxy density field. Previous work has tested the accuracy of this approach with N-body simulations, but generally on idealised mock gala…

The discovery of the faintest known Milky Way satellite using UNIONS Open

Simon E. T. Smith, W. Cerny, Christian R. Hayes, Federico Sestito, Jaclyn Jensen , et al. · 2023

We present the discovery of Ursa Major III/UNIONS 1, the least luminous known satellite of the Milky Way, which is estimated to have an absolute V-band magnitude of $+2.2^{+0.4}_{-0.3}$ mag, equivalent to a total stellar mass of 16$^{+6}_{…

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