P.I. Marcella Marconi INAF-OAC: I. Musella, V. Ripepi, D. De Martino, R. Silvotti,

1. STREGA@VST: Structure and Evolution of the Galaxy P.I.Marcella Marconi INAF-OAC: I. Musella, V. Ripepi, D. De Martino, R. Silvotti, M. Dall’Ora, E. Iodice INAF-OA Roma University Torvergata Roma INAF-OA Teramo University Federico II Naples INAF-OA Torino University of Padova INAF-OA Padova University of Pisa INAF-OA Bologna University of Hertfordshire VST workshop Napoli 21 Luglio 2009

2. Why STREGA? Observations outer Galactic halo clumpy Need to quantify the importance of accretion and interaction mechanisms in the Galactic halo formation. In agreement with theoretical models of hierarchical formation of structures based on Cold Dark Matter cosmology: • Sagittarius  stream evidence • Canis Major (?)  stellar overdensity • Peculiar Galactic Globular Cluster  tidal tails • New SDSS ultra-faint dSphs • (Substructures evidence also in M31 halo) VST workshop Napoli 21 Luglio 2009

3. Why with VST? • Large field of view • High photometric accuracy • Spatial resolution VST workshop Napoli 21 Luglio 2009

4. STREGA main scientific goal Investigate Halo formation mechanisms • Tracing tidal tails and halos around stellar clusters and galaxies • Identifying new very faint stellar systems by using recent techniques (Belokurov et al. 2006) • Mapping extended regions of Fornax orbit • → Fornax stream Strong interest from: Tools: 1)Variable stars (RR Lyrae, LPVs) 2) Main-Sequence and Turn off stars INAF-OA Napoli INAF-OA Roma INAF-OA Teramo University Torvergata Roma University Federico II Napoli University of Hertfordshire VST workshop Napoli 21 Luglio 2009

5. They trace the oldest stellar population (age > 9 Gyr) Low-mass evolved stars  Ideal for studying the 3D structure of the Halo Well known standard candles   Large amplitude (~1mag) and short period (< 1 d) variability  Very easy to recognize RRLyrae advantages Recognized powerful tool to detect stellar overdensities in the Galactic halo (see e.g. Vivas & Zinn 2006, Vivas et al. 2009, Mateu et al. 2009) and to characterize their stellar properties providing clues on the Galactic Halo SFH VST workshop Napoli 21 Luglio 2009

6. MS and TO stars advantages MS stars are very useful to identify extra-tidal populations. TO stars are very easy to recognize (bluest region) They trace the oldest stellar population (age > 9 Gyr) and are >100 times more abundant than RR Lyrae stars VST workshop Napoli 21 Luglio 2009

7. 7 7 60° 1 10 Pal4 30° LeoI LeoII Pal3 Sext KIDS Pal12 G.C. Scl F -30° P ω-cen NGC6752 -60° Fornax Orbit (Dinescu et al 2004) STREGA survey 165 sq. deg. in 4 years → 370 hours Imaging in g,r,i to g24 mag (S/N>10) seeing < 1.2, grey time (u, vS, Hα on 20 fields for additional goals) No strict requirement on the seeing and lunar phase ! Time-series observations in g and i (and in r only for 50 fields) VST workshop Napoli 21 Luglio 2009

8. Pisa University INAF-OA Bologna INAF-OA Napoli STREGA further goals Galactic star counts  Galactic structure INAF-OA Padova Padova University (↔ OmegaCAM GTO) INAF-OA Napoli Study the Galactic Warp (CMa overdensity) Investigate Disk and Halo White Dwarfs and Interacting binaries populations INAF-OA Napoli INAF-OA Torino VST workshop Napoli 21 Luglio 2009

9. Survey field selection • CORE PROGRAM (first 2 yrs) • 38 fields around Fornax and Sculptor, 3 fields around Phoenix, 13 fields around Sextans (up to at least 3 tidal radii for each galaxy) in three directions to distinguish between tidal tails and halos. • 3 fields for Pal3. • 1 field for Pal12. • 8 fields for omega Cen and 8 fields for NGC6752 • 2 strips of 10 adiacent fields in the warp region • ~ 95 fields ~ 220 hours • SECOND PART (second 2 yrs) • strips of adiacent fields distributed trasversally to the stream. • extension to 10 tidal radii for interesting systems investigated in the core program • ~70 fields ~ 150 hours VST workshop Napoli 21 Luglio 2009

10. Single exposure times and limit magnitudes • RR Lyrae, LPVs and CVs: • 20 phase points in g (21.7 mag, with S/N=30) and 10 phase points in i (21.5 mag) • 10 phase points in r (21.5) for 50 fields around galaxies and clusters. • TO and MS stars: from co-adding of individual exposures. One epoch, deep exposure (r=24.0 mag, S/N=10) for the remaining fields • WDs and CVs: u (23.4 mag), g (23.6 mag), r (23.6 mag), i (23.4 mag) and vStromgren (23.4 mag) with S/N=30 and Halpha (3x10-16erg/cm2/s) with S/N=10 (only for CVs) for 20 fields. g, r and i deep frames are obtained co-adding individual exposures. VST workshop Napoli 21 Luglio 2009

11. Survey management plan • Year 3: Obs/data red./expl. • Year 4: Obs/data red./expl.. • Year 5: expl. • Year 1: Obs./data red. • Year 2: Obs/data red./expl. Core Project Data reduction based on VSTCeN hardware and software resources. VST workshop Napoli 21 Luglio 2009

12. VLT spectroscopic follow up Fornax Stream tracers: kinematic and chemical properties of the extra-tidal stars: VIMOS@VLT for radial velocities and FORS@VLT for chemicalabundances WDs:accurate FORS@VLT spectra for the brightest objects among cool and ultracool WDs IBs:FORS@VLT spectra to study the SED of faint objects for classification purposes and time resolved spectroscopy to provide binary parameters. ~10 VLT nights for the whole program. For WDs and IBs we will use VST follow up for the measurement of proper motions VST workshop Napoli 21 Luglio 2009

13. Final remarks • STREGA is an ideal project for VST (grey time, medium seeing). • It will contribute significantly to our understanding of galactic formation mechanisms. • It is based on a strong national collaboration. • Synergy with KIDS under definition for the fields between Fornax and Sculptor. VST workshop Napoli 21 Luglio 2009