Context. The formation of cosmic structures culminates with the assembly of galaxy clusters, a process that is quite different from cluster to cluster. Aims: We present the study of the structure and dynamics of the Lyra complex, consisting of the two clusters RXC J1825.3+3026 and CIZA J1824.1+3029, which was very recently studied by using both X

In this paper we report the current status of a new research program. The primary goal of the “Vanishing and Appearing Sources during a Century of Observations” project is to search for vanishing and appearing sources using existing survey data to find examples of exceptional astrophysical transients. The implications of finding such objects extend

Crater II is the fourth largest galaxy among the satellites of the Milky Way, only surpassed by the Magellanic Clouds, Sagittarius and the recently discovered Antlia II galaxy. This galaxy lies in the frontier between classical satellites and ultra-faint dwarf galaxies. We explore the stellar population of Crater II through both its variable star

Starting with its earliest Data Releases, the Sloan Digital Sky Survey (SDSS) has a long history of producing visually inspected quasar catalogs. Here, we report on the quasar catalog from the sixteenth SDSS Data Release, DR16Q. The catalog comprises more than 750,000 unique quasars, of which 225,000 are new (as compared to the fourteenth data

Our Galaxy is known to contain a central boxy/peanut-shaped bulge, yet the importance of a classical, pressure-supported component within the central part of the Milky Way is still being debated. It should be most visible at low metallicity, a regime that has not yet been studied in detail. Using metallicity-sensitive narrow-band photometry, the

We present an extensive study of the Sagittarius II (Sgr II) stellar system using MegaCam g and i photometry, narrow-band, metallicity-sensitive calcium H&K doublet photometry and Keck II/DEIMOS multiobject spectroscopy. We derive and refine the Sgr II structural and stellar properties inferred at the time of its discovery. The colour-magnitude