The Southern Photometric Local Universe Survey (S-PLUS) is imaging ∼9300 deg2 of the celestial sphere in 12 optical bands using a dedicated 0.8 m robotic telescope, the T80-South, at the Cerro Tololo Inter-american Observatory, Chile. The telescope is equipped with a 9.2k × 9.2k e2v detector with 10 $\rm {\mu m}$ pixels, resulting in a field of view of 2 deg2 with a plate scale of 0.55 arcsec pixel−1. The survey consists of four main subfields, which include two non-contiguous fields at high Galactic latitudes (|b| > 30°, 8000 deg2) and two areas of the Galactic Disc and Bulge (for an additional 1300 deg2). S-PLUS uses the Javalambre 12-band magnitude system, which includes the 5 ugriz broad-band filters and 7 narrow-band filters centred on prominent stellar spectral features: the Balmer jump/[OII], Ca H + K, H δ, G band, Mg b triplet, H α, and the Ca triplet. S-PLUS delivers accurate photometric redshifts (δz/(1 + z) = 0.02 or better) for galaxies with r < 19.7 AB mag and z < 0.4, thus producing a 3D map of the local Universe over a volume of more than $1\, (\mathrm{Gpc}/h)^3$. The final S-PLUS catalogue will also enable the study of star formation and stellar populations in and around the Milky Way and nearby galaxies, as well as searches for quasars, variable sources, and low-metallicity stars. In this paper we introduce the main characteristics of the survey, illustrated with science verification data highlighting the unique capabilities of S-PLUS. We also present the first public data release of ∼336 deg2 of the Stripe 82 area, in 12 bands, to a limiting magnitude of r = 21, available at datalab.noao.edu/splus.

We present the first systematic study of the stellar populations of ultra-diffuse galaxies (UDGs) in the field, integrating the large area search and characterization of UDGs by the SMUDGes survey with the twelve-band optical photometry of the S-PLUS survey. Based on Bayesian modeling of the optical colors of UDGs, we determine the ages, metallicities and stellar masses of 100 UDGs distributed in an area of ∼ 330 deg 2 in the Stripe 82 region. We find that the stellar masses and metallicities of field UDGs are similar to those observed in clusters and follow the trends previously defined in studies of dwarf and giant galaxies. However, field UDGs have younger luminosityweighted ages than do UDGs in clusters. We interpret this result to mean that field UDGs have more extended star formation histories, including some that continue to form stars at low levels to the present time. Finally, we examine stellar population 2 Barbosa et al.scaling relations that show that UDGs are, as a population, similar to other low-surface brightness galaxies.

Context. The origin of the arc-shaped Sh 2-296 nebula is still unclear. Mainly due to its morphology, the nebula has been suggested to be a 0.5 Myr-old supernova remnant (SNR) that could be inducing star formation in the CMa OB1 association. Therefore, this region can be an excellent laboratory for the investigation of the influence of massive stars on their surroundings. Aims. We aim to show, for the first time, that the nebula is part of a large, shell-like structure, which we have designated the "CMa shell", enclosing a bubble created by successive supernova (SN) explosions. We identified three runaway stars, associated with bowshock structures, in the direction of the CMa shell and we investigate the possibility that they have originated in the center of the shell. Methods. By analyzing images of the CMa OB1 association at several wavelengths, we clearly see that the Sh 2-296 nebula is in fact part of a large structure, which can be approximated by a large (with a diameter of ∼ 60 pc) elliptical shell. Using the recent Gaia-DR2 astrometric data, we trace back the path of the three runaway stars, in order to find their original position in the past, with relation to the CMa shell. We also revise the heating and ionization of the Sh 2-296 nebula, by comparing the photon budget provided by the O stars in the region with results from radio observations. Results. We find that the runaway stars have likely been ejected from a Trapezium-like progenitor cluster on three successive SN explosions having taken place ∼ 6, ∼ 2 and ∼ 1 Myr ago. We also show that the few late-type O stars in the region cannot explain the ionization of the Sh 2-296 nebula and other mechanisms need to be at work. Conclusions. We argue that, though we now have evidence for several SNe events in the CMa OB1 association, the SNe probably played a minor role in triggering star formation in these clouds. In contrast, the CMa OB1 association, as it is now, likely testifies to the last stages of a star-forming region.

A large sample of young stellar groups is analysed aiming to investigate their clustering properties and dynamical evolution. A comparison of the Q statistical parameter, measured for the clusters, with the fractal dimension estimated for the projected clouds shows that 52% of the sample has substructures and tends to follow the theoretically expected relation between clusters and clouds, according to calculations for artificial distribution of points. The fractal statistics was also compared to structural parameters revealing that clusters having radial density profile show a trend of parameter s increasing with mean surface stellar density. The core radius of the sample, as a function of age, follows a distribution similar to that observed in stellar groups of Milky Way and other galaxies. They also have dynamical age, indicated by their crossing time, that is similar to unbound associations. The statistical analysis allowed us to separate the sample into two groups showing different clustering characteristics. However, they have the same dynamical evolution, since the whole sample has been revealed as expanding objects, for which the substructures seem to have not been erased. These results are in agreement with simulations that adopt low surface densities and models under supervirial conditions.