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The European Extremely Large Telescope Studying the first galaxies at z>7 Ross McLure Institute for Astronomy, Edinburgh University Slide 2 2 Studying the first galaxies at z>7 Outline n Motivation for studying high-redshift galaxies n Current techniques for selecting galaxies at high redshift n What do we know about 4 3 Studying the first galaxies at z>7 Motivation 1: WMAP and quasar surveys at z>5 show that the epoch of reionisation probably occurs within the redshift interval 6 4 Studying the first galaxies at z>7 Motivation 2: WMAP and quasar surveys at z>5 show that the epoch of reionisation probably occurs within the redshift interval 6 5 Studying the first galaxies at z>7 Selecting galaxies at high redshift Two basic techniques: 1. Lyman-break selection (LBGs) 2. Narrow-band selection of Lyman alpha emitters (LAEs) B V R i z J H K 3.6m 4.5m McLure et al. [2008) Slide 6 6 Studying the first galaxies at z>7 Selecting galaxies at high redshift Two basic techniques: 1. Lyman-break selection (LBGs) 2. Narrow-band selection of Lyman alpha emitters (LAEs) B V R i z J H K 3.6m 4.5m z=5.5 BC model McLure et al. [2008) Slide 7 7 Studying the first galaxies at z>7 Selecting galaxies at high redshift Two basic techniques: 1. Lyman-break selection (LBGs) 2. Narrow-band selection of Lyman alpha emitters (LAEs) z=4.7z=5.7z=6.6 Narrow-band filters sample dark region between sky lines Clean selection method if combined with deep multi-wavelength imaging data However: Selects over very narrow redshift range => large area detectors needed Only a minority of z>4 galaxies appear to be strong Lyman-alpha emitters Slide 8 8 Studying the first galaxies at z>7 What do we know about the 3 9 Studying the first galaxies at z>7 The depth and spatial resolution of the HST ACS imaging in the Ultra Deep Field and wider GOODS N+S fields has been crucial Has allowed high-redshift luminosity function be traced as faint as ~0.1 L* However: Very small areas (HUDF ~13 arcmin 2 ] Potential for large cosmic variance, particularly at bright-end of LF What do we know about the 3 10 Studying the first galaxies at z>7 B-drops at z~4 V-drops at z~5 i-drops at z~6 Adapted from Bouwens et al. (2007) What do we know about the 3 11 Studying the first galaxies at z>7 Small area of HST fields means there is virtually no information brighter than M* What do we know about the 3 12 Studying the first galaxies at z>7 Studying the most luminous objects at z>5 with UKIDSS Ultra-Deep Survey (UDS) McLure et al. (2006, 2008) Deepest, wide-area (1 square degree), near-IR survey undertaken >200 times larger than UDF - picks up rare bright objects Slide 13 13 Studying the first galaxies at z>7 Studying the most luminous objects at z>5 with UKIDSS Ultra-Deep Survey (UDS) McLure et al. (2006, 2008) Deep, wide area, imaging allows much improved determination of bright end of z=5 and z=6 luminosity function Combined with deep HST data, allows determination of LF evolution over full 10L* 14 Studying the first galaxies at z>7 Studying the most luminous objects at z>5 with UKIDSS Ultra-Deep Survey (UDS) McLure et al. (2006, 2008) 1. Wide area allows accurate clustering analysis: r o =8 Mpc, halo masses ~ 5x10 11 M 2. Stacking analysis allows estimate of typcal stellar masses: M stars ~ 10 10 M 3. Combination of LF and typical M/L allows estimate of stellar mass function/density Stellar mass in place by z~6 is ~4x10 6 M Mpc -3 Suggests significant levels of starformation at z>7 Slide 15 15 Studying the first galaxies at z>7 Grey square is an estimate of starformation rate necessary for reionisation (Stiavelli et al. 2003) Appears that z~6 galaxy population maybe be insufficient Suggests significant contribution from earlier galaxy population at z>7 Bouwens et al. (2008) Is the starformation rate at z~6 enough to reionise the Universe? Slide 16 16 Studying the first galaxies at z>7 Current redshift record holder is z=6.96 LAE (Iye et al. 2006) Narrow-band imaging sensitive to range 6.94 17 Studying the first galaxies at z>7 Current redshift record holder is z=6.96 LAE (Iye et al. 2006) Narrow-band imaging sensitive to range 6.94 18 Studying the first galaxies at z>7 z phot =7.6, M stars 2x10 9 M , SFR~ 8 M yr -1 Abell 1689, z=0.18 8 candidates at z~7.4 from GOODS fields Candidates now regularly appearing at 7 19 The galaxy population at 77 candidates will come from: HST WFC3, Ultra-VISTA survey, Hyper-Suprime cam...... Ideally, would like to spatially resolve these objects and study their continuum spectra, not just Lyman-alpha Slide 20 20 The galaxy population at 7 21 The galaxy population at 7 22 Studying the first galaxies at z>7 Summary n Galaxy population studies at 47 galaxy candidates now being published n ELT+AO should be able to spatially resolve z>7 objects n ELT already required to obtain continuum spectra of L* galaxies at z~6 we already know about..... Slide 23 23 Studying the first galaxies at z>7 Slide 24 24 Studying the first galaxies at z>7 Slide 25 25 Studying the first galaxies at z>7 Slide 26 26 Studying the first galaxies at z>7 Slide 27 27 Studying the first galaxies at z>7 Slide 28 28 Studying the first galaxies at z>7 Slide 29 29 Studying the first galaxies at z>7 Slide 30 30 Studying the first galaxies at z>7 Slide 31 31 Studying the first galaxies at z>7 Slide 32 32 Studying the first galaxies at z>7 Slide 33 33 Slide 34 34 Slide 35 35 Slide 36 36