STREGA: STRucture and Evolution of the GAlaxy. I. Survey Overview and First Results

TL;DR

STREGA is a comprehensive survey using the VST telescope to map the Galactic halo, aiming to understand galaxy formation and evolution through stellar tracers and preliminary analysis of stellar density profiles around omega Centauri.

Contribution

This paper introduces the STREGA survey, detailing its design, methods, and initial findings, including the stellar density profile and extratidal stars around omega Centauri.

Findings

Detected extratidal cluster stars around omega Centauri.

Confirmed the cluster's tidal radius at about 1.2 degrees.

Provided preliminary stellar density profiles for the surveyed region.

Abstract

STREGA (STRucture and Evolution of the GAlaxy) is a Guaranteed Time survey being performed at the VST (the ESO VLT Survey Telescope) to map about 150 square degrees in the Galactic halo, in order to constrain the mechanisms of galactic formation and evolution. The survey is built as a five-year project, organized in two parts: a core program to explore the surrounding regions of selected stellar systems and a second complementary part to map the southern portion of the Fornax orbit and extend the observations of the core program. The adopted stellar tracers are mainly variable stars (RR~Lyraes and Long Period Variables) and Main Sequence Turn-off stars for which observations in the g,r,i bands are obtained. We present an overview of the survey and some preliminary results for three observing runs that have been completed. For the region centered on $\omega$~Cen (37 deg^2), covering about three tidal radii, we also discuss the detected stellar density radial profile and angular distribution, leading to the identification of extratidal cluster stars. We also conclude that the cluster tidal radius is about 1.2 deg, in agreement with values in the literature based on the Wilson model.