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Abstract We present the Local GroupL-Band Survey, a Karl G. Jansky Very Large Array (VLA) survey producing the highest-quality 21 cm and 1–2 GHz radio continuum images to date, for the six VLA-accessible, star-forming, Local Group galaxies. Leveraging the VLA’s spectral multiplexing power, we simultaneously survey the 21 cm line at high 0.4 km s⁻¹velocity resolution, the 1–2 GHz polarized continuum, and four OH lines. For the massive spiral M31, the dwarf spiral M33, and the dwarf irregular galaxies NGC 6822, IC 10, IC 1613, and the Wolf–Lundmark–Melotte Galaxy, we use all four VLA configurations and the Green Bank Telescope to reach angular resolutions of <5″ (10–20 pc) for the 21 cm line with <10²⁰cm⁻²column density sensitivity, and even sharper views (<2″; 5–10 pc) of the continuum. Targeting these nearby galaxies (D ≲ 1 Mpc) reveals a sharp, resolved view of the atomic gas, including 21 cm absorption, and continuum emission from supernova remnants and Hiiregions. These data sets can be used to test theories of the abundance and formation of cold clouds, the driving and dissipation of interstellar turbulence, and the impact of feedback from massive stars and supernovae. Here, we describe the survey design and execution, scientific motivation, data processing, and quality assurance. We provide a first look at and publicly release the wide-field 21 cm Hidata products for M31, M33, and four dwarf irregular targets in the survey, which represent some of the highest-physical-resolution 21 cm observations of any external galaxies beyond the LMC and SMC. 

ABSTRACT In this work, we present two new ∼109 particle self-consistent simulations of the merger of a Sagittarius-like dwarf galaxy with a Milky Way (MW)-like disc galaxy. One model is a violent merger creating a thick disc, and a Gaia–Enceladus/Sausage-like remnant. The other is a highly stable disc which we use to illustrate how the improved phase space resolution allows us to better examine the formation and evolution of structures that have been observed in small, local volumes in the MW, such as the z−vz phase spiral and clustering in the vR−vϕ plane when compared to previous works. The local z−vz phase spirals are clearly linked to the global asymmetry across the disc: we find both 2-armed and 1-armed phase spirals, which are related to breathing and bending behaviours, respectively. Hercules-like moving groups are common, clustered in vR−vϕ in local data samples in the simulation. These groups migrate outwards from the inner galaxy, matching observed metallicity trends even in the absence of a galactic bar. We currently release the best-fitting ‘present-day’ merger snapshots along with the unperturbed galaxies for comparison.