The Italian National Institute for Astrophysics (INAF) releases today the images of five galaxies in the local Universe, captured by the VST (VLT Survey Telescope), an Italian telescope managed by INAF in Chile. The new images feature these iconic galaxies in great detail, revealing their shape, colours and distribution of stars up to large distances from the centre. Two of these galaxies, the irregular NGC 3109 and the dwarf irregular Sextans A, are located at about four million light years from us, towards the edge of the Local Group, the aggregate of galaxies to which the Milky Way belongs. Two more galaxies, the beautiful spiral galaxy known as Southern Pinwheel (also referred to as NGC 5236 or M 83) and the irregular galaxy NGC 5253, are located at distances of 15 and 11 million light years from us, respectively, whereas the fifth and most distant one, the spiral galaxy IC 5332, is about 30 million light-years away.
The observations were obtained in three filters, or colours, as part of VST-SMASH (VST Survey of Mass Assembly and Structural Hierarchy). This project, led by Crescenzo Tortora, an INAF researcher in Naples, aims at understanding the mechanisms leading to the formation of the many different galaxies that populate the cosmos. The five galaxies whose images are released today are part of a sample of 27 galaxies the team is studying using the VST. The telescope, housing a 2.6-m diameter mirror, was built in Italy and has been hosted at the European Southern Observatory’s (ESO) Paranal observatory in Chile since 2012.
These galaxies have been carefully selected in the same portion of the sky that, in coming years, is also being observed by the European Space Agency’s (ESA) Euclid satellite. The project will provide a more detailed optical counterpart (up to wavelengths corresponding to the colour blue) to the space-based data collected with Euclid’s VIS instrument (at wavelengths corresponding to the colour red) and with its NISP instrument in the near infrared. The survey has been presented in an article in ESO’s Messenger magazine.
Data analysis is still in its early phases, but observations have already proven effective in examining galaxies down to very low surface brightnesses, which would have been hard to observe only a few years ago. The VST was the key instrument to obtain these images in a relatively short time, thanks to its large field of view of one square degree, equivalent to roughly four times the surface of the full moon in the sky: only 10 hours of observations per square degree were needed to image the field surrounding these galaxies in all three filters.
