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Lyman-alpha searches at z>6

Lyman-alpha searches at z>6. Astrophysical principles. Minimum Flux limit Previous surveys(e.g. Pritchett, Djorgovski) in the early 1990’s were based on the simple paradigm of a monolithic collapse(Eggen, Lynden-Bell and Sandage, 1962) expected star formation rates of 50-500 M sol yr -1

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Lyman-alpha searches at z>6

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  1. Lyman-alpha searches at z>6 Richard McMahon

  2. Astrophysical principles Minimum Flux limit • Previous surveys(e.g. Pritchett, Djorgovski) in the early 1990’s were based on the simple paradigm of a monolithic collapse(Eggen, Lynden-Bell and Sandage, 1962) • expected star formation rates of 50-500 Msol yr-1 • Assume SFR detection limits more appropriate to a slowly disc or sub-galactic units in a halo • i.e. 1-3 Msol yr-1 • 0.5 - 1.0  10-17erg s-1 cm-2 Minimum Volume • search a comoving volume within which you expect to find the progenitors of around 10 L* galaxies. • Local density 1.4±0.2  10-2 h50 Mpc-3 (e.g. Loveday etal, 1992) • minimum is 1000 Mpc3 [c.f. 10Mpc cube] Richard McMahon

  3. Basic observational principles • Target spectral regions where night sky is dark • between the intense OH line emission • For z>5; i.e. >7295 angstroms • Optical; 7600-7700 z=5.25 - 5.33 • 8100-8250 z=5.66 - 5.79 • 9050-9300 z=6.44 - 6.65 • Sky background is 0.5-1.0  10-17erg cm-2 s-1 ang-1 Richard McMahon

  4. Richard McMahon

  5. An extremely luminous galaxy at z=5.74 • 90” x 90” • 500 x 500 h-1kpc(real) • 3.3 x 3.3 h-1 Mpc(comoving) • Ly- flux 1.7 x 10-17 erg cm-2 s-1 • SFR 10 Msol/yr [0.7, 0.3, 0.7] • Look forward time • z=0 14.5Gyr • z=5.7 1.04Gyr • z=10 0.50Gyr Hu, McMahon, Cowie, 1999, ApJ, 522, L9 Richard McMahon

  6. 8150/105 Z I V B R Hu, McMahon, Cowie, 1999, ApJ, 522, L9 Richard McMahon

  7. A Redshift z=6.56 galaxy behind the cluster Abell 360 Hu, Cowie, McMahon, Capak, Iwamuro, Kneib, Maihara, Motohara ApJ Letters accepted; Feb 20th Richard McMahon

  8. Imaging Observations • Narrow band imaging; 9135 /116  • 21,000 secs with LRIS and Keck-I, II • Broad optical imaging • V; 2,400 secs • R; 27,900 secs • Z; 9,820 secs • Near Infra-red broad band imaging • J; 13,280 secs • H; 7,680 secs • K; 15,360 secs • Total; • Optical: 61,000 secs [19hrs] • IR: 34,000 secs [10hrs] Richard McMahon

  9. Keck 10m + LRIS Narrow Band; 9135/118 5.8hrs; 5sigma 1.6x10-17 erg cm-2 s-1 R Band; 7.8 hrs 5” Richard McMahon

  10. The thumbnail images are 19” on a side, centred on the position of the emission, and the circles are 1.2'' in radius. Richard McMahon

  11. Observed frame SED Ly- V R Z J H K Richard McMahon

  12. Richard McMahon

  13. Some numbers • Delta z per filter 0.1 • 5 sigma flux limit in 6hrs with Keck; • 1.6 x 10-17 erg cm-2 s-1 • Amplification factor is 4.5 • Unlensed star formation rate; Salpeter IMF(down to 0.1Mol) • 40 Msol/yr from continuum • 2 Msol/yr from Lyman-alpha line • Surface density of Lyman-alpha galaxies at z=6.6 from 1 object • 4 to 70 per square minute per unit redshift (1 sigma limits) • 0.1 to 2.7 Msol per Mpc3 Richard McMahon

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