SPECTROSCOPIC CONFIRMATION OF z ∼ 7 LYMAN BREAK GALAXIES: PROBING THE EARLIEST GALAXIES AND THE EPOCH OF REIONIZATION

By L. Pentericci, A. Fontana, E. Vanzella, M. Castellano, A. Grazian, M. Dijkstra, K. Boutsia, S. Cristiani, Mark Dickinson, E. Giallongo and 5 more. 2011

222 citations recorded by the source corpus.

We present the final results from our ultra-deep spectroscopic campaign with FORS2 at the ESO Very Large Telescope (VLT) for the confirmation of z ≃ 7 “z-band dropout” candidates selected from our VLT/Hawk-I imaging survey over three independent fields. In particular, we report on two newly discovered galaxies at redshift ∼6.7 in the New Technology Telescope Deep Field. Both galaxies show an Lyα emission line with rest-frame equivalent widths (EWs) of the order of 15–20 Å and luminosities of (2–4) × 1042 erg s−1. We also present the results of ultra-deep observations of a sample of i-dropout galaxies, from which we set a solid upper limit on the fraction of interlopers. Out of the 20 z-dropouts observed we confirm 5 galaxies at 6.6 < z < 7.1. This is systematically below the expectations drawn on the basis of lower redshift observations: in particular, there is a significant lack of objects with intermediate Lyα EWs (between 20 and 55 Å). We conclude that the observed trend for the rising fraction of Lyα emission in Lyman break galaxies from z ∼ 3 to z ∼ 6 is most probably reversed from z ∼ 6 to z ∼ 7. Explaining the observed rapid change in the Lyα emitter fraction among the dropout population with reionization requires a fast evolution of the neutral fraction of hydrogen in the universe. Assuming that the universe is completely ionized at z = 6 and adopting a set of semi-analytical models, we find that our data require a change of the neutral hydrogen fraction of the order of in a time Δz ∼ 1, provided that the escape fraction does not increase dramatically over the same redshift interval.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/333faec2a2dfd8a61d9b529dbbca520655829e6e

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In Astronomy and Astrophysics

1. Richard S. Ellis
2. P. Oesch
3. P. V. van Dokkum
4. R. Bouwens
5. M. Franx
6. J. Dunlop
7. P. Hopkins
8. L. Hernquist

In Instrumentation

1. Richard S. Ellis
2. R. Bouwens
3. P. V. van Dokkum
4. M. Franx
5. P. Oesch
6. J. Dunlop
7. G. Illingworth
8. I. Labbé

Citations in the corpus

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• Signatures of X-rays in the early Universe (2012, background): “…and still allow stellar UV emission to complete reionization at z ∼ 6–7, consistent with recent observations (e.g. Bolton et al. 2011; Dijkstra et al. 2011; Pentericci et al. 2011; Schroeder et al. 2012).1 Several observations indirectly limit the allowed contribution of X-rays to reionization.”
• Cool Gas in High-Redshift Galaxies (2013, background): “…at near–IR wavelengths, and narrow band near–IR surveys, are now systematically detecting galaxies at z ∼ 6 to 10, corresponding to the tail–end of cosmic reionization when the Universe was less than 1Gyr old (Bouwens et al. 2012a,b; Pentericci et al. 2011, Bradac et al. 2012; Coe et al. 2013).”
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• The galaxy stellar mass function at 3.5 ≤z ≤ 7.5 in the CANDELS/UDS, GOODS-South, and HUDF fields (2015, result): “…spectroscopic redshifts were added to the present sample by a collection of high-redshift LBGs from Fontana et al. (2010), Vanzella et al. (2011), Pentericci et al. (2011) and preliminary results of the ESO Large Programme (PI L. Pentericci) with 140 expected A96, page 4 of 25 hours of FORS2…”
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