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Evolution in the properties of Lyman-alpha emitters between redshifts z ~ 3 and z ~ 2

Evolution in the properties of Lyman-alpha emitters between redshifts z ~ 3 and z ~ 2. Kim Nilsson Max-Planck-Institut f ür Astronomie. Christian Tapken, Palle Møller, Wolfram Freudling, Johan Fynbo, Klaus Meisenheimer, Peter Laursen, Göran Östlin. Background - Properties of LAEs. ?.

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Evolution in the properties of Lyman-alpha emitters between redshifts z ~ 3 and z ~ 2

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  1. Evolution in the properties of Lyman-alpha emitters between redshifts z ~ 3 and z ~ 2 Kim Nilsson Max-Planck-Institut für Astronomie Christian Tapken, Palle Møller, Wolfram Freudling, Johan Fynbo, Klaus Meisenheimer, Peter Laursen, Göran Östlin

  2. Background - Properties of LAEs ? Mass Age (Myrs) Mass (108 Msun) Age (Myrs) Blue points at z ~ 3, green points at z ~ 4.5, red points at z ~ 5.5. Gawiser et al., 2006, 2007, Finkelstein et al. 2007, 2008, Lai et al., 2007, 2008, Nilsson et al., 2007, Pirzkal et al., 2007

  3. Data-set • 0.2 deg2 in central part of COSMOS field with ESO2.2m/MPG + WFI • Filter centred on Ly at z = 2.25 ± 0.05 • 30 hours net exposure, flux limit 25.3 magnitudes (AB) • 187 candidates, of which 166 LAE candidates, 17 GALEX-detected and 4 CIV emitting candidates

  4. Reasons for evolution: • A large spread of SEDs observed; red and blue. Some very red objects • Larger fraction of AGN • Change in SFR ratios • Narrower EW distribution

  5. 1) A large spread of SEDs; red and blue Red points are AGN Lines from fitting at z ~ 3 (green; Nilsson et al. 2007, black; Gawiser et al. 2008). Nilsson et al., 2008, submitted to A&A

  6. 2) Larger fraction of AGN • Out of 166 LAE candidates at least nine AGN (7 XMM and 2 VLA) • Out of 17 GALEX detected candidates at least four AGN • Percentage of AGN content at least 5 %, larger than surveys have shown at redshifts z ~ 3 and beyond

  7. 3) Change in SFR ratios Nilsson et al., 2008, submitted to A&A

  8. 4) Narrower EW distribution w0 = 76+11-8 Å Gronwall et al. 2007 Nilsson et al. 2008 w0 = 53 ±3 Å Nilsson et al., 2008, submitted to A&A

  9. Properties of LAEs v. 2 !? Mass Age (Myrs) Mass (108 Msun) Age (Myrs) Blue points at z ~ 3, green points at z ~ 4.5, red points at z ~ 5.5. Gawiser et al., 2006, 2007, Finkelstein et al. 2007, 2008, Lai et al., 2007, 2008, Nilsson et al., 2007, Pirzkal et al., 2007

  10. Summary • Evolution in properties of LAEs between redshift z > 3 and z ~ 2 • Larger fraction of very red galaxies and AGN • More dust content, smaller equivalent widths • Little known about properties of LAEs at all redshifts • Looking forward to finishing SED fit!

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