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Ultra-Deep Spectroscopy of Lyman Break Galaxies at z~6

Ultra-Deep Spectroscopy of Lyman Break Galaxies at z~6. Elizabeth Stanway University of Bristol (ex-UW Madison). Also: Andy Bunker, Karl Glazebrook, Richard Ellis, Bob Abraham, Malcolm Bremer, Laura Douglas. Elizabeth Stanway - A Century of Cosmology, Venice, 30th August 2007.

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Ultra-Deep Spectroscopy of Lyman Break Galaxies at z~6

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  1. Ultra-Deep Spectroscopy of Lyman Break Galaxies at z~6 Elizabeth Stanway University of Bristol (ex-UW Madison) Also: Andy Bunker, Karl Glazebrook, Richard Ellis, Bob Abraham, Malcolm Bremer, Laura Douglas Elizabeth Stanway - A Century of Cosmology, Venice, 30th August 2007

  2. The Status of LBG Spectroscopy at z~6 • Challenges • Lyman Break Galaxies are much harder to confirm than Lyman-a Emitters • LBGs at z~6 are very faint (m*AB>26) • The sky is bright at these wavelengths (OH line emission) • Fields • The majority of spectroscopy has been on public imaging • Private fields include CL1252 (Dow-Hygelund et al 07), BDF (Lehnert & Bremer 04), ERGS (Douglas et al 07) • Instruments • Require good red sensitivity • Require either good sky subtraction or high resolution • Spectrographs used include GMOS, DEIMOS, LRIS, FORS2 Elizabeth Stanway - Venice, 30th Aug 2007

  3. GLARE: Gemini-GMOS spectroscopy • Targeted galaxies in GOODS-S and the HUDF • 22 slits placed on i’-drops, 36hrs of integration with R~1000 • 5 galaxies with secure redshifts, 9 more possible line emitters. • Tight limits (Wlim<10Å) on remaining candidates. At least 45% have EW<10Å Number Tail with EW>100Å Nod & Shuffle reduction => dipole signal EW (rest)

  4. Keck/DEIMOS spectroscopy • Targeted galaxies in GOODS-S and the HUDF • 39 slits placed on i’-drops, min 3hrs/mask, R~5000 • 9 galaxies with secure redshifts, 8 more possible line emitters. • Limits Wlim<12Å on GOODS candidates, Wlim<10-30Å in HUDF. Raw Smooth z=5.99, z’=26.93, W0>250Å

  5. Keck/DEIMOS spectroscopy • Targeted galaxies in GOODS-S and the HUDF • 39 slits placed on i’-drops, min 3hrs/mask, R~5000 • 9 galaxies with secure redshifts, 8 more possible line emitters. • Limits Wlim<12Å on GOODS candidates, Wlim<10-30Å in HUDF. z=5 ERGS spectroscopy High EW tail

  6. z=6 LBGs in a Cosmological Context We see galaxies with large EW at both bright and faint magnitudes => top heavy IMF? Metallicity evolution? Age evolution? We see no evidence for a difference in size between emitters and non-emitters, BUT have small number statistics Elizabeth Stanway - Venice, 30th Aug 2007

  7. Conclusions • Spectroscopy of LBGs at z=6 has benefited from enormous investment of telescope time in recent years • The sample of confirmed galaxies is nevertheless small compared with those at z=5 and below • But the EW distribution is quantifiably different to that at lower redshifts (with a high EW tail). • This sample is HUDF dominated and therefore • a) intrinsically fainter and b) slightly more distant • LBGs at z=6 are younger sources? Elizabeth Stanway - Venice, 30th Aug 2007

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