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In this work, we derive systemic velocities for 8456 RR Lyrae stars. This is the largest dataset of these variables in the Galactic bulge to date. In combination withGaiaproper motions, we computed their orbits using an analytical gravitational potential similar to that of the Milky Way (MW) and identified interlopers from other MW structures, which amount to 22% of the total sample. Our analysis revealed that most interlopers are associated with the halo, and the remainder are linked to the Galactic disk. We confirm the previously reported lag in the rotation curve of bulge RR Lyrae stars, regardless of the removal of interlopers. The rotation patterns of metal-rich RR Lyrae stars are consistent with the pattern of nonvariable metal-rich giants, following the MW bar, while metal-poor stars rotate more slowly. The analysis of the orbital parameter space was used to distinguish bulge stars that in the bar reference frame have prograde orbits from those on retrograde orbits. We classified the prograde stars into orbital families and estimated the chaoticity (in the form of the frequency drift, log ΔΩ) of their orbits. RR Lyrae stars with banana-like orbits have a bimodal distance distribution, similar to the distance distribution seen in metal-rich red clump stars. The fraction of stars with banana-like orbits decreases linearly with metallicity, as does the fraction of stars on prograde orbits (in the bar reference frame). The retrograde-moving stars (in the bar reference frame) form a centrally concentrated nearly spherical distribution. From analyzing anN-body+SPH simulation, we found that some stellar particles in the central parts oscillate between retrograde and prograde orbits and that only a minority stays prograde over a long period of time. Based on the simulation, the ratio of prograde and retrograde stellar particles seems to stabilize within some gigayears after the bar formation. The nonchaoticity of retrograde orbits and their high numbers can explain some of the spatial and kinematical features of the MW bulge that have been often associated with a classical bulge. 

RR Lyrae stars toward the Galactic bulge are used to investigate whether this old stellar population traces the Galactic bar. Although the bar is known to dominate the mass in the inner Galaxy, there is no consensus on whether the RR Lyrae star population, which constitutes some of the most ancient stars in the bulge and thus traces the earliest epochs of star formation, contributes to the barred bulge. We create new reddening maps and derive new extinction laws from visual to near-infrared passbands using improved RR Lyrae period-absolute magnitude-metallicity relations, enabling distance estimates for individual bulge RR Lyrae variables. The extinction law is most uniform inR_IKsandR_JKsand the distances to individual RR Lyrae based on these colors are determined with an accuracy of 6 and 4%, respectively. Using only the near-infrared passbands for distance estimation, we infer the distance to the Galactic center equal tod^cen_JKs= 8217 ± 1(stat) ± 528(sys) pc after geometrical correction. We show that variations in the extinction law toward the Galactic bulge can mimic a barred spatial distribution in the bulge RR Lyrae star population in visual passbands. This arises from a gradient in extinction differences along Galactic longitudes and latitudes, which can create the perception of the Galactic bar, particularly when using visual passband-based distances. A barred angle in the RR Lyrae spatial distribution disappears when near-infrared passband-based distances are used, as well as when reddening law variations are incorporated in visual passband-based distances. The prominence of the bar, traced by RR Lyrae stars, depends on their metallicity, with metal-poor RR Lyrae stars ([Fe/H] < −1.0 dex) showing little to no tilt with respect to the bar. Metal-rich ([Fe/H] > −1.0 dex) RR Lyrae stars do show a barred bulge signature in spatial properties derived using near-infrared distances, with an angle ofι= 18 ± 5 deg, consistent with previous bar measurements from the literature. This also hints at a younger age for this RR Lyrae subgroup. The 5D kinematic analysis, primarily based on transverse velocities, indicates a rotational lag in RR Lyrae stars compared to red clump giants. Despite variations in the extinction law, our kinematic conclusions are robust across different distance estimation methods. 

Context. The Southern Photometric Local Universe Survey (S-PLUS) is a project to map ~9300 sq deg of the sky using twelve bands (seven narrow and five broadbands). Observations are performed with the T80-South telescope, a robotic telescope located at the Cerro Tololo Observatory in Chile. The survey footprint consists of several large contiguous areas, including fields at high and low galactic latitudes, and towards the Magellanic Clouds. S-PLUS uses fixed exposure times to reach point source depths of about 21 mag in the 𝑔riɀ and 20 mag in theuand the narrow filters. Aims. This paper describes the S-PLUS Data Release 4 (DR4), which includes calibrated images and derived catalogues for over 3000 sq deg, covering the aforementioned area. The catalogues provide multi-band photometry performed with the toolsDoPHOTandSExtractor– point spread function (PSF) and aperture photometry, respectively. In addition to the characterization, we also present the scientific potential of the data. Methods. We use statistical tools to present and compare the photometry obtained through different methods. Overall we find good agreement between the different methods, with a slight systematic offset of 0.05 mag between ourPSFand aperture photometry. We show that the astrometry accuracy is equivalent to that obtained in previous S-PLUS data releases, even in very crowded fields where photometric extraction is challenging. The depths of main survey (MS) photometry for a minimum signal-to-noise ratioS/N= 3 reach from ~19.5 for the bluer bands to ~21.5 mag on the red. The range of magnitudes over which accuratePSFphotometry is obtained is shallower, reaching ~19 to ~20.5 mag depending on the filter. Based on these photometric data, we provide star-galaxy-quasar classification and photometric redshift for millions of objects. Results. We demonstrate the versatility of the data by presenting the results of a project to identify members of four Abell galaxy clusters in the Local Universe. The S-PLUS DR4 data allow for a reliable assessment of cluster membership out to a large radius corresponding to 5 ×r₂₀₀. The S-PLUS DR4 can be accessed through the survey data portal. All the software used to generate the catalogues for this release and the scientific investigation presented is available in the collaboration GitHub repository. Conclusions. The S-PLUS DR4 consists of a large, calibrated public dataset, providing powerful ways for studying Galactic and extra-galactic objects through an extensive set of (broad and narrow) filters. 

Abstract We present Dark Energy Spectroscopic Instrument (DESI) observations of the inner halo of M31, which reveal the kinematics of a recent merger—a galactic immigration event—in exquisite detail. Of the 11,416 sources studied in 3.75 hr of on-sky exposure time, 7438 are M31 sources with well-measured radial velocities. The observations reveal intricate coherent kinematic structure in the positions and velocities of individual stars: streams, wedges, and chevrons. While hints of coherent structures have been previously detected in M31, this is the first time they have been seen with such detail and clarity in a galaxy beyond the Milky Way. We find clear kinematic evidence for shell structures in the Giant Stellar Stream, the Northeast Shelf, and Western Shelf regions. The kinematics are remarkably similar to the predictions of dynamical models constructed to explain the spatial morphology of the inner halo. The results are consistent with the interpretation that much of the substructure in the inner halo of M31 is produced by a single galactic immigration event 1–2 Gyr ago. Significant numbers of metal-rich stars ([Fe/H] > − 0.5) are present in all of the detected substructures, suggesting that the immigrating galaxy had an extended star formation history. We also investigate the ability of the shells and Giant Stellar Stream to constrain the gravitational potential of M31, and estimate the mass within a projected radius of 125 kpc to be ${\log }_{10}{M}_{\mathrm{NFW}}(<125\mathrm{kpc})/M_{\odot }={11.80}_{-0.10}^{+0.12}$. The results herald a new era in our ability to study stars on a galactic scale and the immigration histories of galaxies.