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E-ELT : First Stars and stellar populations in our Galaxy (and outside) :

E-ELT : First Stars and stellar populations in our Galaxy (and outside) : Hints for cosmology ?. Presentation of programmes of the CIFISTgroup by P. Bonifacio ( compressed, updated by F. Spite ). Spectroscopy with an ELT : First stars and resolved stellar populations.

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E-ELT : First Stars and stellar populations in our Galaxy (and outside) :

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  1. E-ELT : First Stars and stellar populations in our Galaxy (and outside) : Hints for cosmology ? Presentation of programmes of the CIFISTgroup by P. Bonifacio (compressed, updated by F. Spite)

  2. Spectroscopy with an ELT:First stars and resolved stellar populations • Piercarlo Bonifacio • (following the “First Stars” programme of R. Cayrel) • CIFIST - Marie Curie Excellence Team • GEPI - Observatoire de Paris • INAF - Osservatorio Astronomico di Trieste

  3. Why an ELT ? 2 aims (2 spectrographs) • We want to look at more numerous “KEY” stars. We have to search farther (catching fainter stars). Even at moderate resolution (R=15000-50000) we need the ELT (and the corresponding spectrograph). And : other galaxies ! • We want to look with very high resolution (R>80000) and very high S/N ratio at interesting (basic) objects already studied with 8m class telescopes : using the foreseen HRELT spectrograph

  4. Two WRONG prejudices • “Useless to have an ELT without AO”: this is true if applied to imaging, but FALSE if applied to spectroscopy, at least...within limits • “An ELT cannot work in the UV-blue” : the gain in efficiency may be less than in the NIR, but it is definitely significant and fruitful.

  5. I will concentrate on the UV-Optical range (IR is important also)

  6. A few projects of cosmological interest Evaluations of Big Bang Nucleosynthesis (Lithium Isotopes) “U-ages” of “First Stars” “Be-ages” of globular clusters and stars” Massive stars and re-ionization Mg : fine structure constant and populations

  7. Big Bang Nucleosynthesis Fields et al. 2004

  8. Primordial deuterium Savage et al. 2007

  9. New Yp (helium) determinations Yp by Izotov et al. 2007

  10. P.Bonifacio et al.2006 WMAP : A(Li)=2.64 Li in First Stars

  11. There is tension between the Li measured on the Spite plateau and SBBN predictions assuming the WMAP baryonic density • Solution ? • boring: Li depletion/destruction inside halo dwarfs or in the global halo of the MW (see other galaxies). • less boring: non-standard BBN e. g. massive decaying particles (gravitino ?) Jedamzik et al. (2006), e.g. Larena- Alimi’s solution etc. • Whichever the case, it would be important to measure Li : • -- in more numerous metal-poor stars in our (MW) Galaxy • --in OTHER galaxies to test theories and understand WMAP discrepancy and the very puzzling trend.

  12. An additional constraint. For example, the destruction or depletion by diffusion of 7Li should also apply to6Li: controversial ! The 6Liisotope

  13. 6Li(Asplund et al. 2oo6 data : 3D models) 6Li : black dots

  14. 6Li in Li doublet1D model (same in 3D) Asplund et al. 2006 : HR is required

  15. Comparison of Stellar -WMAP ages U and Th (when available ! ) : residual abundances provide the datation of old stars : HR spectrograph Slow production of Be may measure the ages of globulars and stars (low resolution is enough, but UV domain ! ) Chronometers

  16. The Uranium datation: left : the star CS 31082-001 (Vanessa Hill et al. 2002 V=11.7) right : id. + a star of the HERES survey (Christlieb et al. 2004, Barklem et al. 2005 most V>15), (Ana Frebel 2007), a third one in preparation (Vanessa Hill). spectro UVES R=75 000 S/N=500

  17. Uranium ages :13.2 Gyears(agreement with WMAP)

  18. Be chronometer

  19. CIFIST : Up-to-date methods 3D model atmospheres 2 groups, 2 codes in the world CIFIST has built a cluster of computers

  20. Courtesy of H.-G. Ludwig

  21. The First generations of stars sources of ionizing photons (reionization ?) sources of metals Coherence ? Extremely Metal Poor stars are the fossil record of the first generations (second/third...)

  22. Reliable yields ! No free parameters ! Strong arguments : dearth of neutrons Reality of such monsters ? SN 2006gy (in NGC 1260) interpreted by a pair creation SN in spite of metals Signature of such Pair creation stars ? not found ! Pair creation instability massive (100Ms) supernovae

  23. Pop III Classical SN II (Z = 0 : no metals) acceptable fit ( O/E of model high ? Zn ?)

  24. Massive pair creation Pop III-SN II. Predicted signature : strong O/E effect and low Zn : not found ! Robust predictions, no free parameters

  25. Free parameters The Japanese school adjusts their models of SN II and hypernovae to our observations : they impose values of mass cut, fallback, lower end mixing, upper end mixing and Ye. In this way, the agreement is good.

  26. Magnesium isotopes • Useful for two (linked) questions: • 1) First stars population : • dominated by massive stars or AGB ? • 2) Stability of the fine structure constant (J. Webb , P. Petitjean) : • Mg lines shifted by isotopic effect in old • (high z) inter galactic clouds ? • To be observed : intrinsically faint dwarfs

  27. Metal-poor K dwarfs....FAINT ! courtesy of L. Sbordone T=4500 log g =4.5 [Fe/H]=-2.0

  28. Limiting magnitude Spectral range(s) Spectral resolution(s) OBSERVATIONSHow do we translate this wish-list (in particular analysis of populations in other galaxies) into instrumental requirements ?

  29. Courtesy of N.Christlieb

  30. Metallicity distribution of 34000 SDSS (Sloan) stars with spectra and TO colours g ~17

  31. How far can we go ? The first limitation is the angular resolution AO From the Science Case for the ELT Proxima Cen is at 1.29 pc 40m telescope, 500nm light: diffraction limit ~3mas

  32. Globular cluster in NGC 253 (Sculptor Group)

  33. RGB of old metal-poor populations is at Mv -3.0 to -2.5, for higher metallicities it becomes fainter Mv ~0 is a goal

  34. RGB V=24 RGB V=28

  35. Paranal sky brightness (Patat 2003) No AO 0.8” image Vsky=22.3 Bsky=23.4 AO 0.3” image Vsky=24.5 Bsky=25.5 (Sculptor Group) AO 0.1” image Vsky=26.9 Bsky=27.9 (NGC 3115) AO 0.003” Vsky=34.5 Bsky=35.5

  36. Resolution requirements • isotopic ratios: 80 000-150 000 • ISM: 80 000-300 000 • chemical abundances of individual elements: R=15 000-50 000

  37. Optical wavelength coverage • Minimum 380-672 nm • Desirable 300-950 nm N.B. for many purposes it is not necessary to have a continuous wavelength coverage, small selected ranges will suffice ⇒ non echelle gratings (?) e.g. a “stellar population” spectrograph, two simultaneous ranges (380-420nm)+(640-680nm), R=15000-20000 (dichroic +2 VPH ?) would be able to provide crucial information on distant stellar populations

  38. Summary • spectroscopy on ELT important for: BBN Li, isotopic ratios, chemical composition and history of distant stellar populations • Up to V=22 no AO needed • Two spectrographs needed: 1) high resolution, high stability (CODEX R=150 000) for isotopic ratios, accurate line profiles, ISM; 2) high efficiency, resolution 15 000 - 20 000; perhaps limited (but carefully selected) spectral coverage, for distant stellar populations • Preliminary surveys needed

  39. Analysis of future Surveys as source of stars of extremely low metallicity • -SEGUE - Pan-STARRS - Sky Mapper - LSST • Analysis by P. Bonifacio

  40. SEGUE The SDSS telescope is beeing used targetting Galactic stars ugriz photometry + low resolution spectroscopy. Covers mainly NORTHERN hemisphere

  41. Pan-STARRS Four 1.8m telescopes at Mauna Kea, mainly aimed at stellar variability 3° field of view. Photometry in a wide (“V+R”) band, plus griz

  42. SkyMapper 1.3m telescope (Siding Springs), will cover all the southern sky in 6 bands. In addition to the 5 Sloan bands, Strömgren v will guarantee a good sensitivity to metallicity, 3% precision up to m = 18

  43. Large Synoptic Survey Telescope 8.4m telescope, situated at Cerro Pachon (Chile), 10° field of view, six bands, 5 Sloan-like + a NIR Y band. First light foreseen in 2014

  44. CONCLUSION : SEGUE, thanks to the spectra, and SkyMapper thanks to the v filter, will have a useful metallicity sensitivity. The other surveys ( broad band colours) will allow at most a selection at [Fe/H] <-2.0 (not enough !). AN IMPROVEMENT : Follow-up with narrow-band filters centered on CaIIK line may reach discrimination down to [Fe/H] <-3.5. Pilot project in progress at ESO with 2.2m telescope + WFI

  45. (annexes) The end

  46. Globular clusters have also been used rather than halo field stars (Larena & Alimi’s paper for example) for observing primitive Li abundance in old objects. OK, but globulars usually show abundance anomalies : they produce strong gravitational wells, retaining some ejecta (winds of evolved stars) modifying the initial abundances. A remark

  47. Acknowledgements • Norbert Christlieb • Hans-Günther Ludwig • Luca Sbordone • Paolo Molaro • Luca Pasquini • Codex Team....

  48. An important observation of the isotopes Interstellar matter

  49. In the ISM the two isotopes may be split Knauth Federman Lambert 2003 Mac Donald R=360 000 SNR=500 texp 10h towards ζ Oph V=2.6 MEASURES in low metallicity high-velocity clouds ?

  50. Methods The critical abundances will be determined using up-to-date models of stellar atmospheres : latest continuous opacities, UV diffusion taken into account, 3D atmospheres (CIFIST computer cluster)

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