SCIENCE GOALS OF EXTREMELY LARGE TELESCOPES Sandro D’Odorico European Southern Observatory RENCONTRES DE MORIOND Contents and Structures of the Universe La Thuile, Val d’Aosta, Italy; March 18-25, 2006

s.d’odorico_Moriond_1 TELESCOPE GROWTH SINCE GALILEO Telescope size driven by glas technology for primary surface: (lenses-->monolithic mirrors  segmented mirrors) Today, advances in fabrication and control technologies allow EL segmented primary mirrors to be built for affordable costs and with competitive schedules

s.d’odorico_Moriond_2 RAPID GROWTH OF GROUND-BASED ASTRONOMY IN LITTLE MORE THAN A GENERATION USA and European Astronomers surveying sites for 4m telescopes on Atacama Cerro Morado, Chile, ~1962 (ESO archive photo) LaSilla Obs VLT Obs ALMA- a joint ESO-USA project, under construction

s.d’odorico_Moriond_3 THREE ELTs PROJECTS PRESENTLY UNDERGOING CONCEPTUAL – PHASE A STUDIES:  TMT ( Caltech, Univ. California, AURA, CANADA) 30m  European ELT 30-60m  Giant Magellan Telescope (Carnegie+ USA Univ.) 7x8m TMT European ELT GMT Projected cost : 500 – 700 Million EUROS (~ x 1.15 $) Start of operation: 2016

JWST JWST: NIR and Thermal IR cameras and spectrographs ALMA : antenna array for high angular resolution submillimeter observations CONTEXT IN THE 2 ND DECADE OF THE 3 RD MILLENNIUM: ELTs WILL WORK IN SINERGY WITH THE OTHER TWO MAJOR MULTI-SCOPE FACILITIES OF THAT DECADE, ALMA and JWST s.d’odorico_moriond_4

s.d’odorico-moriond-5 Northern Hemisphere ACTUAL COLLECTING AREA OF LARGE TELESCOPES Southern Hemisphere

s.d’odorico_Moriond_6 GAIN FROM AN ELT – OBSERVING REGIMES  More photons from the larger collecting area (  fainter sources within reach, higher S/N ratios for brightest sources) For photon-noise dominated observations, the S/N gain proportional to D at fixed time and flux, the speed (1/ time required to reach given S/N ) to D 2 ). For sky limited observations of point-like sources at natural seeing (0.7 at V, 0.4” FWHM at K), the S/N proportional to D, the speed to D 2.  Higher angular resolution (  = 1.22 / D ) if atmospheric turbulence can be properly corrected with Adaptive Optics putting a significant fraction of the flux of point-like sources within the Airy disk For sky limited observations of point-like, diffraction limited sources the S/N is proportional to D 2, the speed to D 4. Point-like: stars in the Galaxy and in nearby galaxies, SN, GRB Extended: even at the highest z, galaxies up to a few tens of arcsec in size All of the above provided that instruments at least as efficient as those at 10m class telescopes can be built

s.d’odorico_Moriond_7 GAIN FROM AN ELT –THE ROLE OF ADAPTIVE OPTICS  To fully realize the ELT advantage the telescopes must be equipped with efficient AO system-s ahead of the instruments.  The AO system will consist of an array of artificial laser stars, of a number of wavefront sensors for the laser stars and natural stars in the field, 1-2 fast adaptive mirrors in the telescope optical train and/or in a separate system  Current performance predictions from extrapolation of various flavors of AOs being tested at 8-10m telescopes: - on small, central field (< 30”) very good correction at NIR and thermal IR - on selected regions of large fields (10’) moderate correction in NIR - at visual- red wavelengths on axis and on large fields natural seeing improvement through correction of the Ground Layer of the atmosphere

s.d’odorico_Moriond_8 PRIMARY SCIENCE CASES FOR THE ELTs  From the original science drivers - now filtered through the instrument concept studies (OWL, TMT, ELT)  Mostly similar for the different projects, a few differences. With minimal personal bias 1. Detection and Characterization of Giant to Terrestrial Mass Planets 2. Stellar Populations in external galaxies up to Virgo as tracers of the star formation history though the life of the universe 3. Accurate redshift and characterization of SN up to redshift ~2 4. Detailed properties of galaxies and IGM 1 < z < 5 (mass, metallicity, luminosity function, SFR, extinction, tomography and metal content of IGM) 5. Redshift and characterization of galaxies up to z ~10 (reionisation?), GRBs to the same z as probes of IGM 6. Direct measurement of the expansion history of the Universe (E-ELT science case only) 7. Test of the variability of fundamental constants ………………………..………………………..

s.d’odorico_moriond_9 INSTRUMENTS CONCEPTS MOST RELEVANT FOR COSMOLOGY-RELATED STUDIES (TMT, E-ELT) SINGLE OR MULTI INTEGRAL FIELDS, NIR SPECTROGRAPH Science Cases: 3, 4, 5 Requirements: ~5”x5”, 20mas sampling [ single field]; ~20 IFU 2” x 2” over 5’ x 5’ field / Z, J, H, K bands/ R= / throughput (including telescope) > 15%/  limiting magnitude Ks in a few hours integration at S/N=10 AO requirements: EE % within 50 mas at H. Via LTAO for the single field, via MOAO for large field Flavors: IRIS, IRMOS at TMT, WSPEC, MOMSI at E-ELT Challenges: AO performance over large field/ positionable, cryogenic IFU s

s.d’odorico_moriond_10 INSTRUMENTS CONCEPTS MOST RELEVANT FOR COSMOLOGY-RELATED STUDIES (TMT, E-ELT) MULTI OBJECT VISIBLE SPECTROGRAPH Science Cases: 4, mapping of dark halos in ellipticals from GC and PN Requirements: Field>40 sqmin, Spectral range : nm, Resolution = / Throughput >25% including telescope AO requirements: Improvement of seeing median value by 20-30% with GLAO Flavors: WFOS at TMT, WSPEC at E-ELT (?) Challenges: Size and cost of instrument, performance of GLAO over large field, UV coverage HIGH RESOLUTION OPTICAL SPECTROGRAPH Science Cases: 4,5, 6, 7 Requirements: R= , throughput >15% including telescope, AO requirements: Seeing median improvement by GLAO desiderable Flavors: HROS at TMT, CODEX at E-ELT Challenges: Size of instrument and instrument components, cost, schedule, long-term calibration Nr of QSO from SDSS observable in 3hrs at high resolution, for different S/N, as function of telescope diameter (credit TMT MTHR study)

s.d’odorico_Moriond_11 CODEX ( Cosmic Dynamics Experiment ): an instrument for High Resolution Spectroscopy at the ELTs Legacy Science Program: To test the cosmological model by measuring the predicted drift in the redshift of distant sources as a function of time (Sandage,1962) Science Case and Instrument Concept Study carried out by ESO, IoA Cambridge, Obs.Geneve and INAF Trieste ( Pasquini et al. 2005) Magnitude of the effect: H 0 = 70 km/s/Mpc  t = 10 yr; at z=4  = 1 x A  v ~ 5 cm/s redshift

s.d’odorico_Moriond_12 CODEX : Cosmic Dynamics Experiment The idea and the targets: To use ELT huge collecting area and an high resolution spectrograph with a highly accurate and stable wavelength scale to measure from high S/N spectra the shifts in the Ly  forest and metal systems in the direction of bright QSOs over a large time interval (>10 years). Capitalizing and expanding the expertise and methodology acquired with the successful spectroscopic planet searches (HARPS) and Ly  forest studies with UVES at the VLT. The Instrument: High Resolution Spectrograph operating in the spectral range: nm at R = with a stability of ~1cm / s. Improvement of a factor ~10-20 over HARPS short term accuracy. Long term,stable calibration provided by a laser frequency comb tied to an atomic clock (prototype under study)

s.d’odorico_Moriond_18 CODEX : Cosmic Dynamics Experiment Ly  forest Metal lines QSO Absorption Spectrum, z em = 3 Experiment is unique in probing the dynamical effect of dark energy and doing so in the redshift range z = Ly  lines in very large number over the measurable redshift interval Narrow metallic lines can be used at lower redshift. Peculiar motions expected to be 10 times smaller than Hubble flow. Sufficient number of bright QSO

s.d’odorico_Moriond_14 CODEX : Cosmic Dynamics Experiment Simulated result from 30 QSO randomly distributed in the range 2 < z <4.5 S/N = 3000 per Å pixel/epoch (no metal lines used)  t = 20 years Green points: 0.1 z bins, Blue: 0.5 z bins; Red line: Model with H 0 =70 Km/s/Mpc, Ω m =0.3 Ω  =0.7 The cosmic signal is detected at >99% significance SIMULATIONS Pasquini et al 2005

s.d’odorico_Moriond_15_ CODEX : Cosmic Dynamics Experiment “Immediate” science: Testing the Variability of the Fine Structure Constant α =e 2 /hc Fundamental constants supposedly universal and invariable quantities Measured variations would have far reaching consequences on current theories Astronomical observations hold the potential to probe the value in the past (high z) by a measurement of relative shift of pairS of absortion lines with different sensitivies to the variation of α Keck/Hires 143 systems Δα/α=(-0.57±0.11)×10-5 Murphy et al 2004 VLT/UVES 23 systems Δα/α=(+0.6±0.6)×10-6 Chand et al 2004 CODEX accuracy of  /  = will represent an improvement by two order of magnitudes with respect to present measurements