Cosmology with Large Telescopes: an ESO-centric view Catherine - PowerPoint PPT Presentation

Cosmology with Large Telescopes: an ESO-centric view Catherine Cesarsky ESO Venice, August 2007

The Very Large Telescope (VLT)

The ALMA Project (2012)

ELTs: the world scene • 2 US projects – Giant Magellan Telescope (21-m) • Carnegie & US Universities – Thirty Meter Telescope • Caltech, U. of Calif., Canada GMT TMT

E-ELT • 42m baseline diameter • Innovative 5-mirror design • Excellent image quality 50 mas Axis 1’ 2’ 3’ 4’ 5’ • Reconfigurable: multiple foci F/16 gravity Coude F/15+F/16 invariant

E-ELT Stiff mechanics FE models and analysis 85008 elements 27106 nodes Cross Altitude: 2.1 Hz Altitude locked rotor: 2.5 Hz

E-ELT Powerful built-in AO - M4+M5: GLAO, LTAO - Plus post-focal AO : ExAO, MCAO, MOAO, … M4 AO mirror (adaptive) options WAVEFRONT ABERRATION Waves 1.0000 M5 (tip-tilt) 0.5000 0.0000 Field = ( 0.000,0.0833) Degrees Wavelength = 586.0 nm Defocusing = 0.000000 cm Optical design laser friendly

E-ELT Instrumentation friendly Nasmyth : MCAO module Coude: Codex

Part 1:Fundamental Cosmology • Spectroscopy of distant supernovae • Ly � forest: • small scale coherence length of the mass distribution • variation of physical constants • dynamic measurement of the acceleration of the Universe • Age of the oldest stars

Supernova evidence for acceleration Riess et al. 2004

ESSENCE • World-wide collaboration to find and characterise SNe Ia with 0.2 < z < 0.8 • Search with CTIO 4m Blanco telescope • Spectroscopy with VLT, Gemini, Keck, Magellan • Goal: Measure distances to 200 SNe Ia with an overall accuracy of 5% � determine � to 10% overall

SNLS – The SuperNova Legacy Survey • World-wide collaboration to find and characterise SNe Ia with 0.2 < z < 0.8 • Search with CFHT 4m telescope • Spectroscopy with VLT, Gemini, Keck, Magellan • Goal: Measure distances to 1000 SNe Ia with an overall accuracy of 5% � determine � to 7% overall

First cosmology results published • SNLS – Astier et al. 2006 – 71 distant SNe Ia – various papers describing spectroscopy (Lidman et al. 2006, Hook et al. 2006), rise time (Conley et al. 2006) and individual SNe (Howell et al. 2006) • ESSENCE – Wood-Vasey et al. 2007 – 60 distant SNe Ia – Miknaitis et al. 2007 – description of the survey – Davis et al. 2007 – comparison to exotic dark energy proposals – spectroscopy (Matheson et al. 2005, Blondin et al. 2006)

Time variable w? w=w0+wa (1-a) Distance module versus z Wood-Vasey et al. 2007 Residuals for (-1, 0.27, 0.73) universe

High-z SNe with ELTs: What type of AO? • Use a low-z reference galaxy image shifted to higher z: – angular scale changes – surface brightness changes (+ crude galaxy evolution model) • “Supernova” = point source with approx 80% of galaxy flux • Convolve with different AO PSFs

Simulations for a 42m telescope H band on axis, z=1.65 LTAO MCAO Few (~ 2’ arcsec FOV) GLAO No AO (~5’ PSFs from FOV) Le Louarn et al.

High-z Supernovae with ELT • ELT ideal for high-z spectroscopy – redshifts and types – detailed test of evolution • 42m ELT with AO could reach – z =1.7 (no OH suppression) – or z~4 with OH suppression – using AO GRBs could also be used for similar purposes Statistical Comparison of high and low-z spectral features –Garavini et al.(2007)

Combined analysis of Lyman � forest matter power spectrum, weak lensing and CMB Conclusion: Sigma 8 (co-moving rms of density fluctuations in sphere of radius 8/h Mpc) slightly higher than with WMAP alone Lesgourgues et al.2007 (VHS; Viel et al.2006)

Cosmic structure at small scales Lyman � -forests of two pairs of QSOs observed with UVES; separations: ~ 1’. z ~ 2.6 and 2.1; (B mag : 18.8-20.5) (d’Odorico et al. 2006) With the 2 nd generation VLT instrument X-shooter , higher SNR to fainter magnitudes will make Observations of distant QSO pairs can be used to measure the structure of the intergalactic H I possible to increase significantly and to derive the cosmological parameters. the QSO pair sample Present results fit with the concordance model.

(2008)

Alcock-Paczynski test using the X-shooter (2 nd generation VLT spectrograph) # of QSO pairs (V mag of the faintest one) Expected SNR with Xshooter 2 < z < 3 � z < 0.1 �� < 3’ � < +15° � The transverse distance scale, which is sensitive to the vacuum energy ( � ?) can be determined through the 3-D correlation of Ly � forests of neighboring QSO spectra .An accuracy of 10 % on can be achieved analyzing 13 ( � /1’) � QSO pairs with separation < � (McDonald 2003). � Given the current counts on QSO pairs (left plot) and the performance prediction on the X-shooter the measurement becomes possible with ~140 hr exposure time ( � 120 faint QSOs)

Variability of Physical Constants from QSO Absortion Line Spectra In many models the cosmological evolution of dark energy is accompanied by variations of the fine-structure constant � and of the electron/proton mass ratio � . These variations could be used to trace the evolution with z of the equation of state parameter w From accurate measurements of the absorption line centers in QSO metal absorption lines From Molecular Rotational vs. Vibrational modes of H2 molecules

Measurement of a possible variability of fundamental constants: upper limits of �� from Keck (HIRES) and VLT (UVES) spectra of QSO Very accurate measurements of lines centers of different ion transitions in QSO absorption systems. Status: detection at the limit of accuracy, possibly still biased by systematic errors. Contradictory results from different data sets or the application of different methods. Fig.1 Fig.2 Murphy et al.- fig1 (2004), Chand et al -fig2- (2004)., Levshakov et al (2007)

e.g. Variation of µ = m p /m e Ivanchik et al. (2005, A&A, 440, 45), see also Reinhold et al. (2006), Murphy et al (2006) and many more….. The wavelength of electron-vibro- rotational lines depend on the reduced mass of the molecule Laboratory obs � � µ � � i ( 1 z ) 1 K = + + � � abs i lab � µ � � i Coefficients K have been calculated (Varshalovich and Potekhin 1995) Observations

Profiles of lines selected Q0347-383 Q0405-443 UVES: 20 hours per line of sight Absorptions free of blending and Narrow lines

Correlation between (z-< z>)/(1+<z>) and K? • Systematics ? -> Need for more laboratory wavelength measurements •Increase the number of lines of sight WITH the same absorption lines •Increase S/N ratio

High-Precision Spectrographs at ELTs (e.g. CODEX @ 42m) will be able to increase the accuracy by 2 orders of magnitude (better S/N, special calibration techniques) and give much more significant constraints Reconstruction of equation of state Simulated data set as state-of-art and band of uncertainty (grey area): (upper panels) and with CODEX at dashed line corresponding to input to ELT , for a given DE model , lower simulations, solid line reconstruction’s panels (Martins, 2006) best fit. (Martins, 2006)

Cosmic Dynamics Experiment De- or acceleration of the universal expansion rate causes a small change in observed redshifts as a function of time: Measuring � (z): • Allows us to watch, in real-time, the Universe changing its expansion rate. • Most direct and model- independent route to the expansion history. • First non-geometric measurement of the global RW metric. • Independent confirmation and quantification of accelerated expansion. z & v & Solid lines: Dashed lines: in cm/s

Cosmic Dynamics Experiment Measuring the redshift drift requires: • E-ELT • High resolution, extremely stable spectrograph • ~15 yr long spectroscopic monitoring campaign Best place to observe the redshift drift: the Lyman- � forest.

Cosmic Dynamics Experiment Can we collect enough photons to achieve the required accuracy? Yes: 20 known QSOs with 2 < z < 5 are bright enough to achieve a 3 c m / s radial velocity accuracy 4 cm/s of 3 cm/s with 3200 hours on a 42-m ELT.

Cosmic Dynamics Experiment Simulations: Shrinks with observing time 2.2 nights/month over 15 years will deliver any one of these sets of Grows with time points. Different sets correspond to different target � t = 15 years selection strategies.

Cosmic Dynamics Experiment • 1.7 nights/month over 20 years will unequivocally prove the existence of dark energy without assuming flatness, using any other cosmological constraints or making any � t = 20 years other astrophysical assumption whatsoever. • Provides independent confirmation of SNIa results, using a different method and complementary redshift range. • Data will enable lots of other science (e.g. varying � ), enormous legacy value.

Age of Universe 14.2 ± 2.5 Gyr UVES Cayrel et al. 2001

Part 2: Evolution of the components of the Universe • History of the mass assembly of galaxies: multiwavelength surveys, 3D studies of galaxies • Ly � forest as probe of distant galaxies and IGM • GRBs: galaxies and IGM far and near