STREGA & STEP Surveys

1. STREGA & STEP Surveys V. Ripepi INAF-Osservatorio Astronomico di Capodimonte, Napoli

2. Introduction and Overview • STREGA & STEP are surveys in the context of INAF-OACN GTO • Small and focused surveys • STREGA • STEP • Requirements/Data reduction plans

3. STREGA@VSTSTRructure and Evolution of the GAlaxy P.I.: Marcella Marconi INAF-OAC: D. De Martino, I. Musella, V. Ripepi, R. Silvotti, M. Capaccioli, M. Dall’Ora, E. Iodice Co-workers from INAF-OARoma, INAF-OATeramo, INAF-OATorino, INAF-OAPadova, INAF-OABologna, University of Pisa, University of Padova, University of Hertfordshire

4. 60° Pal4 30° LeoII LeoI Pal3 Sext Pal12 G.C. Scl F -30° P -60° Fornax Orbit (Dinescu et al 2004) STREGA main aim: • Contributetounveil the Haloformationmechanismbyinvestigating the Southern part of the Fornaxstream (Lynden-bell 1982, Lynden-bell & Lynden-bell 1995, Dinescuet al. 2004) • Wewilluse RR Lyrae, LPVs and turn-off starsastracersto test the presenceofextendedhalos (extra-tidal) aroundFornax and SculptordSphs.

5. Additional goals • Study of the Galactic Warp (CMa overdensity) • Disk and Halo White Dwarf Populations: WD LF  age of the Galactic disk, • IMF, SFR, Galactic dark matter • Disk and Halo Populations of Accreting White Dwarfs (CVs)  • space density, evolution of low mass close binaries, constraints • to the origin of galactic x-ray background. • Galactic star counts  Galactic structure

6. 7 7 3 Pal3 Sext Pal12 Scl 1 10 F -30° P -60° 150 fields Field selection • 3 fields for Pal3 • CORE PROGRAM (first 2 yrs) • 24 fieldsaroundFornax and Sculptor (up to 10 tidalradii) in threedirectionstodistinguishbetweentidaltails and halos. • 3 fieldsfor Pal3. • 1 field for Pal12. • 2 stripsof 10 adiacentfields in the warpregion. • ~70 fields~180 hours • 1 field for Pal12 • SECOND PART (second 2 yrs) • Stripsof 10 adiacentfieldsdistributedtrasversallyto the stream. • For the WARP regionwe are coordinatedwith a project for the PaduaOmegaCAM GTO (P.I: Y. Momany) • ~80 fields~180 hours • 7 alternated fields along a third direction (G. C. ?) for both galaxies • 7 alternated fields (up to ~10 tidal radii) on the opposite direction for both galaxies • 10 alternated fields between Fornax and Sculptor along the orbit

7. Survey strategy • 150 squared deg. at g22 mag with S/N30 • 360 hours over 4 years (2 years for the core program) • Data flow = 0.7 Tb/yr • VLT spectroscopic follow-up planned • 6 FTEs per year (3/5 years) • RR Lyrae, LPV and CVs: • 20 phasepoints in g (21.7 mag, with S/N=30) and 10 phasepoints in i (21.5 mag) forall the 150 fields. • 10 phasepoints in r (21.5) for 50 fieldsaroundgalaxies and clusters. • TO stars, C-M and C-C diagrams: TO stars can bedetected in the co-addedindividualexposures. Oneepoch, deepexposure (r=24.0 mag, S/N=10) on the remaining 100 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 (onlyforCVs) for 20 fields. g, r and i deepframes are obtainedco-addingindividualexposures.

8. STEP Survey- the SMC in Time: Evolution of a Prototype interacting dwarf galaxy V. Ripepi, M. Marconi, I. Musella, M. Dall’Ora, A. Ruoppo, M. Capaccioli INAF-Osservatorio Astronomico di Capodimonte, Napoli Co-I: M.R. Cioni (Univ. Hertfordshire) G. Clementini, M. Tosi, G. Macario, D. Romano, M. Cignoni (INAF-OABo) E. Cappellaro (INAF-OAPD) E. Brocato, G. Raimondo, M. Cantiello (INAF-OATeramo) A. Nota, M. Sirianni (STSCI) J.S. Gallagher (Univ. Wisconsin) E. Grebel (Max-Planck Institute)

9. Why SMC • In hierarchical (CDM) models DGs are possible “building blocks” of larger galaxies (including MW)  understanding DGs star formation and chemical enrichment histories is fundamental • Local Group DGs are ideal laboratories for understanding DG properties: we can explore in detail ages, metallicities and spatial distributions of their stellar populations. • Among LG DGs the Small Magellanic Cloud is the closest late-type dwarf • tidal interacting with its neighbours: Wing and Bridge towards the LMC  probe galaxy interaction models

10. OGLE OGLE III STEP Main survey goals • To study in detail the SFH of SMC and of its stellar cluster component through deep (1-2 mag fainter than the TO of the oldest population) CMD over the whole SMC body. • To study systematically for the first time the Wing and Bridge stellar populations both on the basis of CMDs and of variable stars as tracers (e.gCepheids,  Scuti etc.).

11. Survey description • DEEP SURVEY: • Imaging of 35 sq. deg at B~25, V~24.5, i’~23.8 with S/N=10 ( ~ 30 on the body, 3 on the Bridge, 2 in the directions of the Magellanic Stream) • Seeing < 1.2” and grey time required 76.4 h • SHALLOW SURVEY: • Time series photometry (30 phase points in V, 10 in B and i’) on 30 sq. deg properly placed along the wing and the bridge: B~20, V~19.5, i’ 18.5 (expected magnitude of RR Lyrae) with S/N=100. • Summing up the exposures  same limiting magnitudes as above but with S/N=5. • Seeing <1.2” and bright time required 84.5 h • VLT FOLLOW-UP • medium and high resolution multiobject spectroscopy with VLT (FORS and FLAMES) is required for radial velocity and abundance determinations   40 h VLT time • Survey Summary: • 65 Squared degrees imaged in BVi at V24.5 mag • 170 h VST time over two years • 5 FTEs per year (3/4 years) • FLAMES/FORS2@VLT follow up planned

12. Other on-going studies on SMC: • On-going studies on the SMC and/or the Magellanic system are characterized by: • very deep photometry and very small FOV (e.g. HST) • deep photometry but small/patchy FOV (e.g. IAC group) • very shallow photometry and wide FOV (e.g. OGLE) NO ON-GOING STUDY WILL SECURE DEEP PHOTOMETRY ON A WIDE FOV AS STEP WILL.

13. VMC@VISTA Survey HST/VLT Fields Complementary observations/surveys • HST photometry on selected fields, old and young clusters (P.I. J. Gallagher/A. Nota). Observations completed. Data reduction on-going. • VLT spectroscopy (CaII triplet) on several SMC fields (P.I. E. Grebel). Observations completed. Data reduction on-going. • The Vista near-infrared YHKs survey of the Magellanic System (VMC@VISTA) ESO Public survey (P.I: M.R. Cioni): YHKs photometry of the Magellanic System (LMC, SMC, Bridge, Stream): 184 sq. deg. at Ks=20.3 mag in five years. Already approved by ESO .

14. Surveys requiremens • STREGA & STEP have similar requirements: • Good pre-reduction (overscan, etc.) • Good photometric precision  PSF photometry (especially need for STEP, the SMC body can be really crowded) • Good accuracy (i.e.< 0.02 mag)  reliable photometric calibration • Efficient variable star finder  image subtraction analysis

15. Present plans for data reduction • “Standard” pre-reduction with Astrowise including correction for bias, flat-field……astrometry • PSF photometry with DAOPHOT/ALLSTAR: custom automatic PSF modeling by using shell scripts. Slow! Looking for better solutions (PSFEx?). • Standard photometric plan + Astrowise • Efficient variable star finder: image subtraction analysis with VODIA/MDIA (new comparison tests useful) • Light curve analysis: custom programs • We are going to start tests with proprietary WFI data.

16. Conclusions • STREGA & STEP are two small and well aimed surveys in the framework of INAF-OACN GTO time. • STREGA was conceived in 2004. Needed an update at the light of other large surveys ongoing or planned. • Data reduction with AW, but we need PSF photometry.