Work

The MUSEHubbleUltra Deep Field Survey

Year: 2020

Type: article

Abstract: Context.The Lyαemitter (LAE) fraction,XLAE, is a potentially powerful probe of the evolution of the intergalactic neutral hydrogen gas fraction. However, uncertainties in the measurement ofXLAEare still under debate. Aims.Thanks to deep data obtained with the integral field spectrograph Multi Unit Spectroscopic Explorer (MUSE), we can measure the evolution of the LAE fraction homogeneously over a wide redshift range ofz ≈ 3–6 for UV-faint galaxies (down to UV magnitudes ofM1500 ≈ −17.75). This is a significantly fainter range than in former studies (M1500 ≤ −18.75) and it allows us to probe the bulk of the population of high-redshift star-forming galaxies. Methods.We constructed a UV-complete photometric-redshift sample following UV luminosity functions and measured the Lyαemission with MUSE using the latest (second) data release from the MUSEHubbleUltra Deep Field Survey. Results.We derived the redshift evolution ofXLAEforM1500 ∈ [ − 21.75; −17.75] for the first time with a equivalent width rangeEW(Lyα) ≥ 65 Å and found low values ofXLAE ≲ 30% atz ≲ 6. The best-fit linear relation isXLAE= 0.07+0.06−0.03z− 0.22+0.12−0.24. ForM1500 ∈ [ − 20.25; −18.75] andEW(Lyα) ≥ 25 Å, ourXLAEvalues are consistent with those in the literature within 1σatz ≲ 5, but our median values are systematically lower than reported values over the whole redshift range. In addition, we do not find a significant dependence ofXLAEonM1500forEW(Lyα) ≥ 50 Å atz ≈ 3–4, in contrast with previous work. The differences inXLAEmainly arise from selection biases for Lyman Break Galaxies (LBGs) in the literature: UV-faint LBGs are more easily selected if they have strong Lyαemission, henceXLAEis biased towards higher values when those samples are used. Conclusions.Our results suggest either a lower increase ofXLAEtowardsz ≈ 6 than previously suggested, or even a turnover ofXLAEatz ≈ 5.5, which may be the signature of a late or patchy reionization process. We compared our results with predictions from a cosmological galaxy evolution model. We find that a model with a bursty star formation (SF) can reproduce our observed LAE fractions much better than models where SF is a smooth function of time.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/201937340