Now almost 70 years since its introduction, the effective or half-light radius has become a very popular choice for characterising galaxy size. However, the effective radius measures the concentration of light within galaxies and thus does not capture our intuitive definition of size which is related to the edge or boundary of objects. For this reason, we aim to demonstrate the undesirable consequence of using the effective radius to draw conclusions about the nature of faint ultra-diffuse galaxies (UDGs) when compared to dwarfs and Milky Way-like galaxies. Instead of the effective radius

We present an analysis of high-resolution Keck/HIRES spectroscopic observations of J0815+4729, an extremely carbon-enhanced, iron-poor dwarf star. These high-quality data allow us to derive a metallicity of [Fe/H] = −5.49 ± 0.14 from the three strongest Fe I lines and to measure a high [Ca/Fe] = 0.75 ± 0.14. The large carbon abundance of A(C) = 7.43 ± 0.17 (or [C/Fe] ∼ 4.49 ± 0.11) places this star in the upper boundary of the low- carbon band in the A(C)–[Fe/H] diagram, suggesting no contamination from a binary AGB companion. We detect the oxygen triplet at 777 nm for the first time in an

The “Lambda Cold Dark Matter” (CDM) cosmological model is the current theory credited for reproducing the physics responsible for the formation and evolution of large-scale galactic systems in an accelerated expanding universe. In this context, the halos of CDM collapse and convert their energy reaching a state of equilibrium, allowing the formation of galaxies when the matter begins to cool. From an observational point of view, the behaviour of the luminous matter (stars and gas) is very different from that of dark matter. However, there are empirical relationships that reflect the

The interstellar medium is an excellent laboratory to test physical processes that cannot be reproduced in Earth-based laboratories. In this study several nebulae were used as a space laboratory to confirm the existence of an atomic process for which there was no previous experimental confirmation. In 2010, the existence of an atomic process that should occur frequently in astrophysical plasmas throughout the universe was theoretically proposed. The point is that this process — which is termed Rydberg Enhanced Recombination, or RER — had never before been detected, and it’s effectively