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« Hot » scientific researches at VLT in cosmology

« Hot » scientific researches at VLT in cosmology. At increasing redshifts. Mass Galaxy formation/gas accretion Star formation/enrichment Ages, history Beyond the reionisation epochs. Kinematics/Dynamics Chemistry/dust Stellar populations Searches for z ~ 6-7. .

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« Hot » scientific researches at VLT in cosmology

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  1. « Hot » scientific researches at VLT in cosmology At increasing redshifts Mass Galaxy formation/gas accretion Star formation/enrichment Ages, history Beyond the reionisation epochs Kinematics/Dynamics • Chemistry/dust • Stellar populations • Searches for z ~ 6-7  To be improved by:  higher spectral resolution (3000 < R < 15000)  3D spectroscopy in the near IR (high z)

  2. Galaxy spectroscopy pre-requisites(Liang et al, 2003a, A&A submitted) • R>1000 spectroscopy for: • extinction ( Balmer lines corrected • for stellar absorption) • SFRs • gas chemistry • proper analysis of stellar populations

  3. Spectral resolution Based on ISAAC ETC 3000 500 Assuming low read-out noise CCDs and that OH sky lines dominate at l > 0.7 mm Low resolution: should be > 1000 (extinction, SFRs, gas abundances) Medium resolution : ~ 10000-20000 (dynamics, stellar populations) Much better detection of emission/absorption lines at R ~ few 1000 Recently illustrated by: Steidel (2004): several 100 spectra 1.4 < z < 2.6 (DEIMOS R=5000) ~ 10/arcmin2, 5 times more than LBGs VIMOS survey, I=24 (R=250): very few objects at z > 1.4

  4. - extinction corrected Ha SFRs are close to mid-IR estimates (Elbaz et al, 2002) for SFR < 150 MO/yr (i.e. below ULIRGs)  Double check on SFR estimates Estimating extinctions and SFRs at z ~1(Flores et al, 2003, A&A in press) FORS2/ISAAC: 16 ISO galaxies, 0.4< z <1 , R=1250 to 2000

  5. 3D to test the merging hypothesis

  6. Galaxy populations: what do we know ?

  7. IJK Image quality requirements ISAAC, Ks=28, van Dokkum et al. 2003 Distant galaxies are small and low surface brightness sources! 3D spectroscopy at R> 3000  0.2 « FWHM » arcsec (8 m) or 0.06 « FWHM » arcsec ( 30m)  0.02 « FWHM » arcsec ( 100m)  need to concentrate the light!

  8. Spatial resolution FWHM Microlenses • AO sharpens the PSF • FWHM decreases. • Gain in angular resolution. • Increase of the fraction of light into a sub-aperture. • More object, less sky. • Increase of the spectral S/N

  9. FALCON AO system IFUs WFS • Several independent AO systems in a wide field. • Integration of DM and pupil relay optics in an « adaptive button » Þ µ-DM required. • Problem : no optical feedback from DM to WFS. • Critical point : servo loop, to be studied. • sky coverage is essential

  10. Performances based on simulations • 10 Cosmological fields (b > 45°), 100 objects/field • Tomographic reconstruction of on-axis phase (F Assemat et al, 2003) • Fraction of light in a 0.25 square aperture increased by at least a factor 2 in J band (1.25 µm) and H band (1.65 µm). • FWHM < 0.2 arcsec  sky coverage of 50% (GS with V<16, S/N=10) • allow to reach ~ 0.06 arcsec (FWHM) on a 30m, 0.02 arcsec on a 100m • Requirements : µ-DMs with 50-70 actuators for 8m, 15 times more for 30 m (but density conserved), very sensitive WFS with a high number of apertures.

  11. Which field of view for galaxy spectroscopy ? multi-object 3D spectroscopy at R>> 1000 (AO does not need to correct all the field, just the scientific targets!) • Small fields severely affected by cosmic variance • (e.g. HDF-N & S, ~ 6 arcmin2) • Galaxy correlation scales 4-9 Mpc (z=0 to z=4, LBGs) • F =9 to 20 arcmin a minimum also # density of LBGs, LIRGs, sub-mm, Ellipticals : 0.01 to few / arcmin2

  12. Discussion • z= 1000 (WMAP): accurate physics & cosmological parameters • z= 0: first detailed star formation histories (Local Group) detailed dynamics (FP) and galaxy properties z= 1 to > 6: ELTs + (3D spectroscopy, R>>1000 and fov=10 arcmin): the only way to understand the physics of the galaxy formation

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