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« 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. . - PowerPoint PPT Presentation
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Kinematics/Dynamics
Chemistry/dustStellar populations
Searches for z ~ 6-7
« Hot » scientific researches at VLT in cosmology
Mass
Galaxy formation/gas accretion
Star formation/enrichmentAges, history
Beyond the reionisation epochs
At increasing redshifts
To be improved by:
higher spectral resolution (3000 < R < 15000)
3D spectroscopy in the near IR (high z)
R>1000 spectroscopy for:
- extinction ( Balmer lines corrected for stellar absorption)- SFRs
-gas chemistry
-proper analysis of stellar populations
Galaxy spectroscopy pre-requisites(Liang et al, 2003a, A&A submitted)
Spectral resolution
Assuming low read-out noise CCDs and that OH sky lines dominateat > 0.7 m
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 LBGsVIMOS survey, I=24 (R=250): very few objects at z > 1.4
3000
500
Based on ISAAC ETC
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
- extinction corrected H 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
3D to test the merging hypothesis
Galaxy populations: what do we know ?Redshift/
# objects
z < 1.3
Several 10000s
1.3 < z < 2.6
z desert ?
but Steidel..
z=3-5
1000 LBGs
SCUBA’s
z > 6
2 QSOs,
3 galaxies ??
Epoch of Formation of disks ?
??? Ellipticals forming?
Reionisation
First stars ?
Extinction/
SFR
Still uncertain but SIRTF/VLT
Unknown
??
Largely model dependent
unknown
Stellar mass/
Metal
Uncertain
Few measures
Very uncert.
??
Very uncert.
5 measures ?
???
??
Mass/
Dynamics
TF uncertain
FP for E’s ?
none Small ’s ? ??
Image quality requirements
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!
IJK
ISAAC, Ks=28, van Dokkum et al. 2003
FWHM
Microlenses
AO sharpens the PSF
FWHM decreases.
Gain in angular
resolution.
Spatial resolution
Increase of the fraction of light
into a sub-aperture.
More object, less sky.
Increase of the spectral S/N
Integration of DM and pupil relay optics in an « adaptive button » µ-DM required. Problem : no optical feedback from DM to WFS. Critical point : servo loop, to be studied.
sky coverage is essential
Several independent AO systems in a wide field.
IFUs WFS
FALCON AO system
10 Cosmological fields (b 45°), 100 objects/fieldTomographic 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 100mRequirements : 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.
Performances based on simulations
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)
=9 to 20 arcmin a minimum
also # density of LBGs, LIRGs, sub-mm, Ellipticals :
0.01 to few / arcmin2
Which field of view for galaxy spectroscopy ?
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
Discussion