@article{11507,
  abstract     = {Lyman-α (Lyα) is intrinsically the brightest line emitted from active galaxies. While it originates from many physical processes, for star-forming galaxies the intrinsic Lyα luminosity is a direct tracer of the Lyman-continuum (LyC) radiation produced by the most massive O- and early-type B-stars (M⋆ ≳ 10 M⊙) with lifetimes of a few Myrs. As such, Lyα luminosity should be an excellent instantaneous star formation rate (SFR) indicator. However, its resonant nature and susceptibility to dust as a rest-frame UV photon makes Lyα very hard to interpret due to the uncertain Lyα escape fraction, fesc, Lyα. Here we explore results from the CAlibrating LYMan-α with Hα (CALYMHA) survey at z = 2.2, follow-up of Lyα emitters (LAEs) at z = 2.2 − 2.6 and a z ∼ 0−0.3 compilation of LAEs to directly measure fesc, Lyα with Hα. We derive a simple empirical relation that robustly retrieves fesc, Lyα as a function of Lyα rest-frame EW (EW0): fesc,Lyα = 0.0048 EW0[Å] ± 0.05 and we show that it constrains a well-defined anti-correlation between ionisation efficiency (ξion) and dust extinction in LAEs. Observed Lyα luminosities and EW0 are easy measurable quantities at high redshift, thus making our relation a practical tool to estimate intrinsic Lyα and LyC luminosities under well controlled and simple assumptions. Our results allow observed Lyα luminosities to be used to compute SFRs for LAEs at z ∼ 0−2.6 within ±0.2 dex of the Hα dust corrected SFRs. We apply our empirical SFR(Lyα,EW0) calibration to several sources at z ≥ 2.6 to find that star-forming LAEs have SFRs typically ranging from 0.1 to 20 M⊙ yr−1 and that our calibration might be even applicable for the most luminous LAEs within the epoch of re-ionisation. Our results imply high ionisation efficiencies (log10[ξion/Hz erg−1] = 25.4−25.6) and low dust content in LAEs across cosmic time, and will be easily tested with future observations with JWST which can obtain Hα and Hβ measurements for high-redshift LAEs.},
  author       = {Sobral, David and Matthee, Jorryt J},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: high-redshift / galaxies: star formation / galaxies: statistics / galaxies: evolution / galaxies: formation / galaxies: ISM},
  publisher    = {EDP Sciences},
  title        = {{Predicting Lyα escape fractions with a simple observable: Lyα in emission as an empirically calibrated star formation rate indicator}},
  doi          = {10.1051/0004-6361/201833075},
  volume       = {623},
  year         = {2019},
}

@article{11535,
  abstract     = {We investigate the clustering and halo properties of ∼5000 Ly α-selected emission-line galaxies (LAEs) from the Slicing COSMOS 4K (SC4K) and from archival NB497 imaging of SA22 split in 15 discrete redshift slices between z ∼ 2.5 and 6. We measure clustering lengths of r0 ∼ 3–6 h−1 Mpc and typical halo masses of ∼1011 M⊙ for our narrowband-selected LAEs with typical LLy α ∼ 1042–43 erg s−1. The intermediate-band-selected LAEs are observed to have r0 ∼ 3.5–15 h−1 Mpc with typical halo masses of ∼1011–12 M⊙ and typical LLy α ∼ 1043–43.6 erg s−1. We find a strong, redshift-independent correlation between halo mass and Ly α luminosity normalized by the characteristic Ly α luminosity, L⋆(z). The faintest LAEs (L ∼ 0.1 L⋆(z)) typically identified by deep narrowband surveys are found in 1010 M⊙ haloes and the brightest LAEs (L ∼ 7 L⋆(z)) are found in ∼5 × 1012 M⊙ haloes. A dependency on the rest-frame 1500 Å UV luminosity, MUV, is also observed where the halo masses increase from 1011 to 1013 M⊙ for MUV ∼ −19 to −23.5 mag. Halo mass is also observed to increase from 109.8 to 1012 M⊙ for dust-corrected UV star formation rates from ∼0.6 to 10 M⊙ yr−1 and continues to increase up to 1013 M⊙ in halo mass, where the majority of those sources are active galactic nuclei. All the trends we observe are found to be redshift independent. Our results reveal that LAEs are the likely progenitors of a wide range of galaxies depending on their luminosity, from dwarf-like, to Milky Way-type, to bright cluster galaxies. LAEs therefore provide unique insight into the early formation and evolution of the galaxies we observe in the local Universe.},
  author       = {Khostovan, A A and Sobral, D and Mobasher, B and Matthee, Jorryt J and Cochrane, R K and Chartab, N and Jafariyazani, M and Paulino-Afonso, A and Santos, S and Calhau, J},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: haloes, galaxies: high-redshift, galaxies: star formation, cosmology: observations, large-scale structure of Universe},
  number       = {1},
  pages        = {555--573},
  publisher    = {Oxford University Press},
  title        = {{The clustering of typical Ly α emitters from z ∼ 2.5–6: Host halo masses depend on Ly α and UV luminosities}},
  doi          = {10.1093/mnras/stz2149},
  volume       = {489},
  year         = {2019},
}

@article{11541,
  abstract     = {We present new Hubble Space Telescope (HST)/WFC3 observations and re-analyse VLT data to unveil the continuum, variability, and rest-frame ultraviolet (UV) lines of the multiple UV clumps of the most luminous Lyα emitter at z = 6.6, CR7 (COSMOS Redshift 7). Our re-reduced, flux-calibrated X-SHOOTER spectra of CR7 reveal an He II emission line in observations obtained along the major axis of Lyα emission with the best seeing conditions. He II is spatially offset by ≈+0.8 arcsec from the peak of Lyα emission, and it is found towards clump B. Our WFC3 grism spectra detects the UV continuum of CR7’s clump A, yielding a power law with β=−2.5+0.6−0.7 and MUV=−21.87+0.25−0.20⁠. No significant variability is found for any of the UV clumps on their own, but there is tentative (≈2.2 σ) brightening of CR7 in F110W as a whole from 2012 to 2017. HST grism data fail to robustly detect rest-frame UV lines in any of the clumps, implying fluxes ≲2×10−17 erg s−1 cm−2 (3σ). We perform CLOUDY modelling to constrain the metallicity and the ionizing nature of CR7. CR7 seems to be actively forming stars without any clear active galactic nucleus activity in clump A, consistent with a metallicity of ∼0.05–0.2 Z⊙. Component C or an interclump component between B and C may host a high ionization source. Our results highlight the need for spatially resolved information to study the formation and assembly of early galaxies.},
  author       = {Sobral, David and Matthee, Jorryt J and Brammer, Gabriel and Ferrara, Andrea and Alegre, Lara and Röttgering, Huub and Schaerer, Daniel and Mobasher, Bahram and Darvish, Behnam},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, galaxies: ISM, cosmology: observations, dark ages, reionization, first stars, early Universe},
  number       = {2},
  pages        = {2422--2441},
  publisher    = {Oxford University Press},
  title        = {{On the nature and physical conditions of the luminous Ly α emitter CR7 and its rest-frame UV components}},
  doi          = {10.1093/mnras/sty2779},
  volume       = {482},
  year         = {2019},
}

@article{11508,
  abstract     = {Distant luminous Lyman-α emitters (LAEs) are excellent targets for spectroscopic observations of galaxies in the epoch of reionisation (EoR). We present deep high-resolution (R = 5000) VLT/X-shooter observations, along with an extensive collection of photometric data of COLA1, a proposed double peaked LAE at z = 6.6. We rule out the possibility that COLA1’s emission line is an [OII] doublet at z = 1.475 on the basis of i) the asymmetric red line-profile and flux ratio of the peaks (blue/red=0.31 ± 0.03) and ii) an unphysical [OII]/Hα ratio ([OII]/Hα >  22). We show that COLA1’s observed B-band flux is explained by a faint extended foreground LAE, for which we detect Lyα and [OIII] at z = 2.142. We thus conclude that COLA1 is a real double-peaked LAE at z = 6.593, the first discovered at z >  6. COLA1 is UV luminous (M1500 = −21.6 ± 0.3), has a high equivalent width (EW0,Lyα = 120−40+50 Å) and very compact Lyα emission (r50,Lyα = 0.33−0.04+0.07 kpc). Relatively weak inferred Hβ+[OIII] line-emission from Spitzer/IRAC indicates an extremely low metallicity of Z <  1/20 Z⊙ or reduced strength of nebular lines due to high escape of ionising photons. The small Lyα peak separation of 220 ± 20 km s−1 implies a low HI column density and an ionising photon escape fraction of ≈15 − 30%, providing the first direct evidence that such galaxies contribute actively to the reionisation of the Universe at z >  6. Based on simple estimates, we find that COLA1 could have provided just enough photons to reionise its own ≈0.3 pMpc (2.3 cMpc) bubble, allowing the blue Lyα line to be observed. However, we also discuss alternative scenarios explaining the detected double peaked nature of COLA1. Our results show that future high-resolution observations of statistical samples of double peaked LAEs at z >  5 are a promising probe of the occurrence of ionised regions around galaxies in the EoR.},
  author       = {Matthee, Jorryt J and Sobral, David and Gronke, Max and Paulino-Afonso, Ana and Stefanon, Mauro and Röttgering, Huub},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: high-redshift / galaxies: formation / dark ages / reionization / first stars / techniques: spectroscopic / intergalactic medium},
  publisher    = {EDP Sciences},
  title        = {{Confirmation of double peaked Lyα emission at z = 6.593: Witnessing a galaxy directly contributing to the reionisation of the universe}},
  doi          = {10.1051/0004-6361/201833528},
  volume       = {619},
  year         = {2018},
}

@article{11549,
  abstract     = {We investigate the clustering properties of ∼7000 H β + [O III] and [O II] narrowband-selected emitters at z ∼ 0.8–4.7 from the High-z Emission Line Survey. We find clustering lengths, r0, of 1.5–4.0 h−1 Mpc and minimum dark matter halo masses of 1010.7–12.1 M⊙ for our z = 0.8–3.2 H β + [O III] emitters and r0 ∼ 2.0–8.3 h−1 Mpc and halo masses of 1011.5–12.6 M⊙ for our z = 1.5–4.7 [O II] emitters. We find r0 to strongly increase both with increasing line luminosity and redshift. By taking into account the evolution of the characteristic line luminosity, L⋆(z), and using our model predictions of halo mass given r0, we find a strong, redshift-independent increasing trend between L/L⋆(z) and minimum halo mass. The faintest H β + [O III] emitters are found to reside in 109.5 M⊙ haloes and the brightest emitters in 1013.0 M⊙ haloes. For [O II] emitters, the faintest emitters are found in 1010.5 M⊙ haloes and the brightest emitters in 1012.6 M⊙ haloes. A redshift-independent stellar mass dependency is also observed where the halo mass increases from 1011 to 1012.5 M⊙ for stellar masses of 108.5 to 1011.5 M⊙, respectively. We investigate the interdependencies of these trends by repeating our analysis in a Lline−Mstar grid space for our most populated samples (H β + [O III] z = 0.84 and [O II] z = 1.47) and find that the line luminosity dependency is stronger than the stellar mass dependency on halo mass. For L > L⋆ emitters at all epochs, we find a relatively flat trend with halo masses of 1012.5–13 M⊙, which may be due to quenching mechanisms in massive haloes that is consistent with a transitional halo mass predicted by models.},
  author       = {Khostovan, A A and Sobral, D and Mobasher, B and Best, P N and Smail, I and Matthee, Jorryt J and Darvish, B and Nayyeri, H and Hemmati, S and Stott, J P},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: haloes, galaxies: high-redshift, galaxies: star formation, cosmology: observations, large-scale structure of Universe},
  number       = {3},
  pages        = {2999--3015},
  publisher    = {Oxford University Press},
  title        = {{The clustering of H β + [O III] and [O II] emitters since z ∼ 5: Dependencies with line luminosity and stellar mass}},
  doi          = {10.1093/mnras/sty925},
  volume       = {478},
  year         = {2018},
}

@article{11555,
  abstract     = {We investigate the morphology of the [C II] emission in a sample of ‘normal’ star-forming galaxies at 5 < z < 7.2 in relation to their UV (rest-frame) counterpart. We use new Atacama Large Millimetre/submillimetre Array (ALMA) observations of galaxies at z ∼ 6–7, as well as a careful re-analysis of archival ALMA data. In total 29 galaxies were analysed, 21 of which are detected in [C II]. For several of the latter the [C II] emission breaks into multiple components. Only a fraction of these [C II] components, if any, is associated with the primary UV systems, while the bulk of the [C II] emission is associated either with fainter UV components, or not associated with any UV counterpart at the current limits. By taking into account the presence of all these components, we find that the L[CII]–SFR (star formation rate) relation at early epochs is fully consistent with the local relation, but it has a dispersion of 0.48 ± 0.07 dex, which is about two times larger than observed locally. We also find that the deviation from the local L[CII]–SFR relation has a weak anticorrelation with the EW(Ly α). The morphological analysis also reveals that [C II] emission is generally much more extended than the UV emission. As a consequence, these primordial galaxies are characterized by a [C II] surface brightness generally much lower than expected from the local Σ[CII]−ΣSFR relation. These properties are likely a consequence of a combination of different effects, namely gas metallicity, [C II] emission from obscured star-forming regions, strong variations of the ionization parameter, and circumgalactic gas in accretion or ejected by these primeval galaxies.},
  author       = {Carniani, S and Maiolino, R and Amorin, R and Pentericci, L and Pallottini, A and Ferrara, A and Willott, C J and Smit, R and Matthee, Jorryt J and Sobral, D and Santini, P and Castellano, M and De Barros, S and Fontana, A and Grazian, A and Guaita, L},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, galaxies: ISM, galaxies: formation},
  number       = {1},
  pages        = {1170--1184},
  publisher    = {Oxford University Press},
  title        = {{Kiloparsec-scale gaseous clumps and star formation at z = 5–7}},
  doi          = {10.1093/mnras/sty1088},
  volume       = {478},
  year         = {2018},
}

@article{11557,
  abstract     = {Deep narrow-band surveys have revealed a large population of faint Ly α emitters (LAEs) in the distant Universe, but relatively little is known about the most luminous sources (⁠LLyα≳1042.7 erg s−1; LLyα≳L∗Lyα⁠). Here we present the spectroscopic follow-up of 21 luminous LAEs at z ∼ 2–3 found with panoramic narrow-band surveys over five independent extragalactic fields (≈4 × 106 Mpc3 surveyed at z ∼ 2.2 and z ∼ 3.1). We use WHT/ISIS, Keck/DEIMOS, and VLT/X-SHOOTER to study these sources using high ionization UV lines. Luminous LAEs at z ∼ 2–3 have blue UV slopes (⁠β=−2.0+0.3−0.1⁠) and high Ly α escape fractions (⁠50+20−15 per cent) and span five orders of magnitude in UV luminosity (MUV ≈ −19 to −24). Many (70 per cent) show at least one high ionization rest-frame UV line such as C IV, N V, C III], He II or O III], typically blue-shifted by ≈100–200 km s−1 relative to Ly α. Their Ly α profiles reveal a wide variety of shapes, including significant blue-shifted components and widths from 200 to 4000 km s−1. Overall, 60 ± 11  per cent appear to be active galactic nucleus (AGN) dominated, and at LLyα > 1043.3 erg s−1 and/or MUV < −21.5 virtually all LAEs are AGNs with high ionization parameters (log U = 0.6 ± 0.5) and with metallicities of ≈0.5 − 1 Z⊙. Those lacking signatures of AGNs (40 ± 11  per cent) have lower ionization parameters (⁠logU=−3.0+1.6−0.9 and log ξion = 25.4 ± 0.2) and are apparently metal-poor sources likely powered by young, dust-poor ‘maximal’ starbursts. Our results show that luminous LAEs at z ∼ 2–3 are a diverse population and that 2×L∗Lyα and 2×M∗UV mark a sharp transition in the nature of LAEs, from star formation dominated to AGN dominated.},
  author       = {Sobral, David and Matthee, Jorryt J and Darvish, Behnam and Smail, Ian and Best, Philip N and Alegre, Lara and Röttgering, Huub and Mobasher, Bahram and Paulino-Afonso, Ana and Stroe, Andra and Oteo, Iván},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: active, galaxies: evolution, galaxies: high-redshift, galaxies: ISM, galaxies: starburst, cosmology: observations},
  number       = {2},
  pages        = {2817--2840},
  publisher    = {Oxford University Press},
  title        = {{The nature of luminous Ly α emitters at z ∼ 2–3: Maximal dust-poor starbursts and highly ionizing AGN}},
  doi          = {10.1093/mnras/sty782},
  volume       = {477},
  year         = {2018},
}

@article{11558,
  abstract     = {We present and explore deep narrow- and medium-band data obtained with the Subaru and the Isaac Newton Telescopes in the ∼2 deg2 COSMOS field. We use these data as an extremely wide, low-resolution (R ∼ 20–80) Integral Field Unit survey to slice through the COSMOS field and obtain a large sample of ∼4000 Ly α emitters (LAEs) from z ∼ 2 to 6 in 16 redshift slices (SC4K). We present new Ly α luminosity functions (LFs) covering a comoving volume of ∼108 Mpc3. SC4K extensively complements ultradeep surveys, jointly covering over 4 dex in Ly α luminosity and revealing a global (2.5 < z < 6) synergy LF with α=−1.93+0.12−0.12⁠, log10Φ∗Lyα=−3.45+0.22−0.29 Mpc−3, and log10L∗Lyα=42.93+0.15−0.11 erg s−1. The Schechter component of the Ly α LF reveals a factor ∼5 rise in L∗Lyα and a ∼7 × decline in Φ∗Lyα from z ∼ 2 to 6. The data reveal an extra power-law (or Schechter) component above LLy α ≈ 1043.3 erg s−1 at z ∼ 2.2–3.5 and we show that it is partially driven by X-ray and radio active galactic nucleus (AGN), as their Ly α LF resembles the excess. The power-law component vanishes and/or is below our detection limits above z > 3.5, likely linked with the evolution of the AGN population. The Ly α luminosity density rises by a factor ∼2 from z ∼ 2 to 3 but is then found to be roughly constant (⁠1.1+0.2−0.2×1040 erg s−1 Mpc−3) to z ∼ 6, despite the ∼0.7 dex drop in ultraviolet (UV) luminosity density. The Ly α/UV luminosity density ratio rises from 4 ± 1 per cent to 30 ± 6 per cent from z ∼ 2.2 to 6. Our results imply a rise of a factor of ≈2 in the global ionization efficiency (ξion) and a factor ≈4 ± 1 in the Ly α escape fraction from z ∼ 2 to 6, hinting for evolution in both the typical burstiness/stellar populations and even more so in the typical interstellar medium conditions allowing Ly α photons to escape.},
  author       = {Sobral, David and Santos, Sérgio and Matthee, Jorryt J and Paulino-Afonso, Ana and Ribeiro, Bruno and Calhau, João and Khostovan, Ali A},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: formation, galaxies: high-redshift, galaxies: luminosity function, mass function, galaxies: statistics},
  number       = {4},
  pages        = {4725--4752},
  publisher    = {Oxford University Press},
  title        = {{Slicing COSMOS with SC4K: The evolution of typical Ly α emitters and the Ly α escape fraction from z ∼ 2 to 6}},
  doi          = {10.1093/mnras/sty378},
  volume       = {476},
  year         = {2018},
}

@article{11518,
  abstract     = {We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [C II]158 mm line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Lyα emitting galaxy at z = 6.6 that consists of three separated UV-continuum components. Our observations reveal several well-separated components of [C II] emission. The two most luminous components in [C II] coincide with the brightest UV components (A and B), blueshifted by »150 km s−1 with respect to the
peak of Lyα emission. Other [C II] components are observed close to UV clumps B and C and are blueshifted by »300 and ≈80 km s−1 with respect to the systemic redshift. We do not detect FIR continuum emission due to dust with a 3σ limiting luminosity LIR T L d 35 K 3.1 10 = <´ 10 ( ) . This allows us to mitigate uncertainties in the dust-corrected SFR and derive SFRs for the three UV clumps A, B, and C of 28, 5, and 7 M yr−1. All clumps have [C II] luminosities consistent within the scatter observed in the local relation between SFR and L[ ] C II , implying that strong Lyα emission does not necessarily anti-correlate with [C II] luminosity. Combining
our measurements with the literature, we show that galaxies with blue UV slopes have weaker [C II] emission at fixed SFR, potentially due to their lower metallicities and/or higher photoionization. Comparison with hydrodynamical simulations suggests that CR7ʼs clumps have metallicities of 0.1 Z Z 0.2 < < . The observed ISM structure of CR7 indicates that we are likely witnessing the build up of a central galaxy in the early universe through complex accretion of satellites.},
  author       = {Matthee, Jorryt J and Sobral, D. and Boone, F. and Röttgering, H. and Schaerer, D. and Girard, M. and Pallottini, A. and Vallini, L. and Ferrara, A. and Darvish, B. and Mobasher, B.},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, dark ages, reionization, first stars – galaxies: formation – galaxies: high-redshift – galaxies: ISM – galaxies: kinematics and dynamics},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{ALMA reveals metals yet no dust within multiple components in CR7}},
  doi          = {10.3847/1538-4357/aa9931},
  volume       = {851},
  year         = {2017},
}

@article{11562,
  abstract     = {We present the CAlibrating LYMan-α with Hα (CALYMHA) pilot survey and new results on Lyman α (Lyα) selected galaxies at z ∼ 2. We use a custom-built Lyα narrow-band filter at the Isaac Newton Telescope, designed to provide a matched volume coverage to the z = 2.23 Hα HiZELS survey. Here, we present the first results for the COSMOS and UDS fields. Our survey currently reaches a 3σ line flux limit of ∼4 × 10−17 erg s−1 cm−2, and a Lyα luminosity limit of ∼1042.3 erg s−1. We find 188 Lyα emitters over 7.3 × 105 Mpc3, but also find significant numbers of other line-emitting sources corresponding to He II, C III] and C IV emission lines. These sources are important contaminants, and we carefully remove them, unlike most previous studies. We find that the Lyα luminosity function at z = 2.23 is very well described by a Schechter function up to LLy α ≈ 1043 erg s−1 with L∗=1042.59+0.16−0.08 erg s−1, ϕ∗=10−3.09+0.14−0.34 Mpc−3 and α = −1.75 ± 0.25. Above LLy α ≈ 1043 erg s−1, the Lyα luminosity function becomes power-law like, driven by X-ray AGN. We find that Lyα-selected emitters have a high escape fraction of 37 ± 7 per cent, anticorrelated with Lyα luminosity and correlated with Lyα equivalent width. Lyα emitters have ubiquitous large (≈40 kpc) Lyα haloes, ∼2 times larger than their Hα extents. By directly comparing our Lyα and Hα luminosity functions, we find that the global/overall escape fraction of Lyα photons (within a 13 kpc radius) from the full population of star-forming galaxies is 5.1 ± 0.2 per cent at the peak of the star formation history. An extra 3.3 ± 0.3 per cent of Lyα photons likely still escape, but at larger radii.},
  author       = {Sobral, David and Matthee, Jorryt J and Best, Philip and Stroe, Andra and Röttgering, Huub and Oteo, Iván and Smail, Ian and Morabito, Leah and Paulino-Afonso, Ana},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: haloes, galaxies: high-redshift, galaxies: luminosity function, mass function, galaxies: statistics, cosmology: observations},
  number       = {1},
  pages        = {1242--1258},
  publisher    = {Oxford University Press},
  title        = {{The CALYMHA survey: Lyα luminosity function and global escape fraction of Lyα photons at z = 2.23}},
  doi          = {10.1093/mnras/stw3090},
  volume       = {466},
  year         = {2017},
}

@article{11564,
  abstract     = {We study the production rate of ionizing photons of a sample of 588 Hα emitters (HAEs) and 160 Lyman-α emitters (LAEs) at z = 2.2 in the COSMOS field in order to assess the implied emissivity from galaxies, based on their ultraviolet (UV) luminosity. By exploring the rest-frame Lyman Continuum (LyC) with GALEX/NUV data, we find fesc < 2.8 (6.4) per cent through median (mean) stacking. By combining the Hα luminosity density with intergalactic medium emissivity measurements from absorption studies, we find a globally averaged 〈fesc〉 of 5.9+14.5−4.2 per cent at z = 2.2 if we assume HAEs are the only source of ionizing photons. We find similarly low values of the global 〈fesc〉 at z ≈ 3–5, also ruling out a high 〈fesc〉 at z < 5. These low escape fractions allow us to measure ξion, the number of produced ionizing photons per unit UV luminosity, and investigate how this depends on galaxy properties. We find a typical ξion ≈ 1024.77 ± 0.04 Hz erg−1 for HAEs and ξion ≈ 1025.14 ± 0.09 Hz erg−1 for LAEs. LAEs and low-mass HAEs at z = 2.2 show similar values of ξion as typically assumed in the reionization era, while the typical HAE is three times less ionizing. Due to an increasing ξion with increasing EW(Hα), ξion likely increases with redshift. This evolution alone is fully in line with the observed evolution of ξion between z ≈ 2 and 5, indicating a typical value of ξion ≈ 1025.4 Hz erg−1 in the reionization era.},
  author       = {Matthee, Jorryt J and Sobral, David and Best, Philip and Khostovan, Ali Ahmad and Oteo, Iván and Bouwens, Rychard and Röttgering, Huub},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, cosmology: observations, dark ages, reionization, first stars},
  number       = {3},
  pages        = {3637--3655},
  publisher    = {Oxford University Press},
  title        = {{The production and escape of Lyman-Continuum radiation from star-forming galaxies at z ∼ 2 and their redshift evolution}},
  doi          = {10.1093/mnras/stw2973},
  volume       = {465},
  year         = {2017},
}

@article{11566,
  abstract     = {While traditionally associated with active galactic nuclei (AGN), the properties of the C II] (λ = 2326 Å), C III] (λ, λ = 1907, 1909 Å) and C IV (λ, λ = 1549, 1551 Å) emission lines are still uncertain as large, unbiased samples of sources are scarce. We present the first blind, statistical study of C II], C III] and C IV emitters at z ∼ 0.68, 1.05, 1.53, respectively, uniformly selected down to a flux limit of ∼4 × 10−17 erg s−1 cm−1 through a narrow-band survey covering an area of ∼1.4 deg2 over COSMOS and UDS. We detect 16 C II], 35 C III] and 17 C IV emitters, whose nature we investigate using optical colours as well as Hubble Space Telescope (HST), X-ray, radio and far-infrared data. We find that z ∼ 0.7 C II] emitters are consistent with a mixture of blue (UV slope β = −2.0 ± 0.4) star-forming (SF) galaxies with discy HST structure and AGN with Seyfert-like morphologies. Bright C II] emitters have individual X-ray detections as well as high average black hole accretion rates (BHARs) of ∼0.1 M⊙ yr−1. C III] emitters at z ∼ 1.05 trace a general population of SF galaxies, with β = −0.8 ± 1.1, a variety of optical morphologies, including isolated and interacting galaxies and low BHAR (<0.02 M⊙ yr−1). Our C IV emitters at z ∼ 1.5 are consistent with young, blue quasars (β ∼ −1.9) with point-like optical morphologies, bright X-ray counterparts and large BHAR (0.8  M⊙ yr−1). We also find some surprising C II], C III] and C IV emitters with rest-frame equivalent widths (EWs) that could be as large as 50–100 Å. AGN or spatial offsets between the UV continuum stellar disc and the line-emitting regions may explain the large EW. These bright C II], C III] and C IV emitters are ideal candidates for spectroscopic follow-up to fully unveil their nature.},
  author       = {Stroe, Andra and Sobral, David and Matthee, Jorryt J and Calhau, João and Oteo, Ivan},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: active, galaxies: high-redshift, quasars: emission lines, galaxies: star formation, cosmology: observations},
  number       = {3},
  pages        = {2558--2574},
  publisher    = {Oxford University Press},
  title        = {{A 1.4 deg2 blind survey for C II], C III] and C IV at z ∼ 0.7–1.5 – I. Nature, morphologies and equivalent widths }},
  doi          = {10.1093/mnras/stx1712},
  volume       = {471},
  year         = {2017},
}

@article{11567,
  abstract     = {Recently, the C III] and C IV emission lines have been observed in galaxies in the early Universe (z > 5), providing new ways to measure their redshift and study their stellar populations and active galactic nuclei (AGN). We explore the first blind C II], C III] and C IV survey (z ∼ 0.68, 1.05, 1.53, respectively) presented in Stroe et al. (2017). We derive luminosity functions (LF) and study properties of C II], C III] and C IV line emitters through comparisons to the LFs of H α and Ly α emitters, UV selected star-forming (SF) galaxies and quasars at similar redshifts. The C II] LF at z ∼ 0.68 is equally well described by a Schechter or a power-law LF, characteristic of a mixture of SF and AGN activity. The C III] LF (z ∼ 1.05) is consistent to a scaled down version of the Schechter H α and Ly α LF at their redshift, indicating a SF origin. In stark contrast, the C IV LF at z ∼ 1.53 is well fit by a power-law, quasar-like LF. We find that the brightest UV sources (MUV < −22) will universally have C III] and C IV emission. However, on average, C III] and C IV are not as abundant as H α or Ly α emitters at the same redshift, with cosmic average ratios of ∼0.02–0.06 to H α and ∼0.01–0.1 to intrinsic Ly α. We predict that the C III] and C IV lines can only be truly competitive in confirming high-redshift candidates when the hosts are intrinsically bright and the effective Ly α escape fraction is below 1 per cent. While C III] and C IV were proposed as good tracers of young, relatively low-metallicity galaxies typical of the early Universe, we find that, at least at z ∼ 1.5, C IV is exclusively hosted by AGN/quasars, especially at large line equivalent widths.},
  author       = {Stroe, Andra and Sobral, David and Matthee, Jorryt J and Calhau, João and Oteo, Ivan},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: active, galaxies: high redshift, galaxies: luminosity function, mass function, quasars: emission lines, star formation, cosmology: observations},
  number       = {3},
  pages        = {2575--2586},
  publisher    = {Oxford University Press},
  title        = {{A 1.4 deg2 blind survey for C II], C III] and C IV at z ∼ 0.7–1.5 – II. Luminosity functions and cosmic average line ratios}},
  doi          = {10.1093/mnras/stx1713},
  volume       = {471},
  year         = {2017},
}

@article{11572,
  abstract     = {We present spectroscopic follow-up of candidate luminous Ly α emitters (LAEs) at z = 5.7–6.6 in the SA22 field with VLT/X-SHOOTER. We confirm two new luminous LAEs at z = 5.676 (SR6) and z = 6.532 (VR7), and also present HST follow-up of both sources. These sources have luminosities LLy α ≈ 3 × 1043 erg s−1, very high rest-frame equivalent widths of EW0 ≳ 200 Å and narrow Ly α lines (200–340 km s−1). VR7 is the most UV-luminous LAE at z > 6.5, with M1500 = −22.5, even brighter in the UV than CR7. Besides Ly α, we do not detect any other rest-frame UV lines in the spectra of SR6 and VR7, and argue that rest-frame UV lines are easier to observe in bright galaxies with low Ly α equivalent widths. We confirm that Ly α line widths increase with Ly α luminosity at z = 5.7, while there are indications that Ly α lines of faint LAEs become broader at z = 6.6, potentially due to reionization. We find a large spread of up to 3 dex in UV luminosity for >L⋆ LAEs, but find that the Ly α luminosity of the brightest LAEs is strongly related to UV luminosity at z = 6.6. Under basic assumptions, we find that several LAEs at z ≈ 6–7 have Ly α escape fractions ≳ 100  per cent, indicating bursty star formation histories, alternative Ly α production mechanisms, or dust attenuating Ly α emission differently than UV emission. Finally, we present a method to compute ξion, the production efficiency of ionizing photons, and find that LAEs at z ≈ 6–7 have high values of log10(ξion/Hz erg−1) ≈ 25.51 ± 0.09 that may alleviate the need for high Lyman-Continuum escape fractions required for reionization.},
  author       = {Matthee, Jorryt J and Sobral, David and Darvish, Behnam and Santos, Sérgio and Mobasher, Bahram and Paulino-Afonso, Ana and Röttgering, Huub and Alegre, Lara},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution – galaxies: high-redshift, dark ages, reionization, first stars, cosmology: observations},
  number       = {1},
  pages        = {772--787},
  publisher    = {Oxford University Press},
  title        = {{Spectroscopic properties of luminous Ly α emitters at z ≈ 6–7 and comparison to the Lyman-break population}},
  doi          = {10.1093/mnras/stx2061},
  volume       = {472},
  year         = {2017},
}

@article{11573,
  abstract     = {We present dynamical measurements from the KMOS (K-band multi-object spectrograph) Deep Survey (KDS), which comprises 77 typical star-forming galaxies at z ≃ 3.5 in the mass range 9.0 < log (M⋆/M⊙) < 10.5. These measurements constrain the internal dynamics, the intrinsic velocity dispersions (σint) and rotation velocities (VC) of galaxies in the high-redshift Universe. The mean velocity dispersion of the galaxies in our sample is σint=70.8+3.3−3.1kms−1⁠, revealing that the increasing average σint with increasing redshift, reported for z ≲ 2, continues out to z ≃ 3.5. Only 36 ± 8 per cent of our galaxies are rotation-dominated (VC/σint > 1), with the sample average VC/σint value much smaller than at lower redshift. After carefully selecting comparable star-forming samples at multiple epochs, we find that the rotation-dominated fraction evolves with redshift with a z−0.2 dependence. The rotation-dominated KDS galaxies show no clear offset from the local rotation velocity–stellar mass (i.e. VC–M⋆) relation, although a smaller fraction of the galaxies are on the relation due to the increase in the dispersion-dominated fraction. These observations are consistent with a simple equilibrium model picture, in which random motions are boosted in high-redshift galaxies by a combination of the increasing gas fractions, accretion efficiency, specific star formation rate and stellar feedback and which may provide significant pressure support against gravity on the galactic disc scale.},
  author       = {Turner, O. J. and Cirasuolo, M. and Harrison, C. M. and McLure, R. J. and Dunlop, J. S. and Swinbank, A. M. and Johnson, H. L. and Sobral, D. and Matthee, Jorryt J and Sharples, R. M.},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, galaxies: kinematics and dynamics},
  number       = {2},
  pages        = {1280--1320},
  publisher    = {Oxford University Press},
  title        = {{The KMOS Deep Survey (KDS) – I. Dynamical measurements of typical star-forming galaxies at z ≃ 3.5}},
  doi          = {10.1093/mnras/stx1366},
  volume       = {471},
  year         = {2017},
}

@article{11574,
  abstract     = {We present new results from the widest narrow-band survey search for Lyα emitters at z = 5.7, just after reionization. We survey a total of 7 deg2 spread over the COSMOS, UDS and SA22 fields. We find over 11 000 line emitters, out of which 514 are robust Lyα candidates at z = 5.7 within a volume of 6.3 × 106 Mpc3. Our Lyα emitters span a wide range in Lyα luminosities, from faint to bright (LLyα ∼ 1042.5–44 erg s−1) and rest-frame equivalent widths (EW0 ∼ 25–1000 Å) in a single, homogeneous data set. By combining all our fields, we find that the faint end slope of the z = 5.7 Lyα luminosity function is very steep, with α=−2.3+0.4−0.3⁠. We also present an updated z = 6.6 Lyα luminosity function, based on comparable volumes and obtained with the same methods, which we directly compare with that at z = 5.7. We find a significant decline of the number density of faint Lyα emitters from z = 5.7 to 6.6 (by 0.5 ± 0.1 dex), but no evolution at the bright end/no evolution in L*. Faint Lyα emitters at z = 6.6 show much more extended haloes than those at z = 5.7, suggesting that neutral Hydrogen plays an important role, increasing the scattering and leading to observations missing faint Lyα emission within the epoch of reionization. Altogether, our results suggest that we are observing patchy reionization which happens first around the brightest Lyα emitters, allowing the number densities of those sources to remain unaffected by the increase of neutral Hydrogen fraction from z ∼ 5 to 7.},
  author       = {Santos, Sérgio and Sobral, David and Matthee, Jorryt J},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: high-redshift, galaxies: luminosity function, mass function, cosmology: observations, dark ages, reionization, first stars},
  number       = {2},
  pages        = {1678--1691},
  publisher    = {Oxford University Press},
  title        = {{The Lyα luminosity function at z= 5.7–6.6 and the steep drop of the faint end: Implications for reionization}},
  doi          = {10.1093/mnras/stw2076},
  volume       = {463},
  year         = {2016},
}

@article{11576,
  abstract     = {We use new near-infrared spectroscopic observations to investigate the nature and evolution of the most luminous Hα emitters at z ∼ 0.8–2.23, which evolve strongly in number density over this period, and compare them to more typical Hα emitters. We study 59 luminous Hα emitters with LHα > L∗Hα⁠, roughly equally split per redshift slice at z ∼ 0.8, 1.47 and 2.23 from the HiZELS and CF-HiZELS surveys. We find that, overall, 30 ± 8 per cent are active galactic nuclei [AGNs; 80 ± 30 per cent of these AGNs are broad-line AGNs, BL-AGNs], and we find little to no evolution in the AGN fraction with redshift, within the errors. However, the AGN fraction increases strongly with Hα luminosity and correlates best with LHα/L∗Hα(z)⁠. While LHα ≤ L∗Hα(z) Hα emitters are largely dominated by star-forming galaxies (>80 per cent), the most luminous Hα emitters (⁠LHα>10L∗Hα(z)⁠) at any cosmic time are essentially all BL-AGN. Using our AGN-decontaminated sample of luminous star-forming galaxies, and integrating down to a fixed Hα luminosity, we find a factor of ∼1300 evolution in the star formation rate density from z = 0 to 2.23. This is much stronger than the evolution from typical Hα star-forming galaxies and in line with the evolution seen for constant luminosity cuts used to select ‘ultraluminous’ infrared galaxies and/or sub-millimetre galaxies. By taking into account the evolution in the typical Hα luminosity, we show that the most strongly star-forming Hα-selected galaxies at any epoch (⁠LHα>L∗Hα(z)⁠) contribute the same fractional amount of ≈15 per cent to the total star formation rate density, at least up to z = 2.23.},
  author       = {Sobral, David and Kohn, Saul A. and Best, Philip N. and Smail, Ian and Harrison, Chris M. and Stott, John and Calhau, João and Matthee, Jorryt J},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, cosmology: observations},
  number       = {2},
  pages        = {1739--1752},
  publisher    = {Oxford University Press},
  title        = {{The most luminous H α emitters at z ∼ 0.8–2.23 from HiZELS: Evolution of AGN and star-forming galaxies}},
  doi          = {10.1093/mnras/stw022},
  volume       = {457},
  year         = {2016},
}

@article{11578,
  abstract     = {We present the first results from our CAlibrating LYMan α with Hα (CALYMHA) pilot survey at the Isaac Newton Telescope. We measure Lyα emission for 488 Hα selected galaxies at z = 2.23 from High-z Emission Line Survey in the COSMOS and UDS fields with a specially designed narrow-band filter (λc = 3918 Å, Δλ = 52 Å). We find 17 dual Hα-Lyα emitters [fLyα > 5 × 10−17 erg s−1 cm−2, of which five are X-ray active galactic nuclei (AGN)]. For star-forming galaxies, we find a range of Lyα escape fractions (fesc, measured with 3 arcsec apertures) from 2 to 30 per cent. These galaxies have masses from 3 × 108 M⊙ to 1011 M⊙ and dust attenuations E(B − V) = 0–0.5. Using stacking, we measure a median escape fraction of 1.6 ± 0.5 per cent (4.0 ± 1.0 per cent without correcting Hα for dust), but show that this depends on galaxy properties. The stacked fesc tends to decrease with increasing star formation rate and dust attenuation. However, at the highest masses and dust attenuations, we detect individual galaxies with fesc much higher than the typical values from stacking, indicating significant scatter in the values of fesc. Relations between fesc and UV slope are bimodal, with high fesc for either the bluest or reddest galaxies. We speculate that this bimodality and large scatter in the values of fesc is due to additional physical mechanisms such as outflows facilitating fesc for dusty/massive systems. Lyα is significantly more extended than Hα and the UV. fesc continues to increase up to at least 20 kpc (3σ, 40 kpc [2σ]) for typical star-forming galaxies and thus the aperture is the most important predictor of fesc.},
  author       = {Matthee, Jorryt J and Sobral, David and Oteo, Iván and Best, Philip and Smail, Ian and Röttgering, Huub and Paulino-Afonso, Ana},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, galaxies: ISM},
  number       = {1},
  pages        = {449--467},
  publisher    = {Oxford University Press},
  title        = {{The CALYMHA survey: Lyα escape fraction and its dependence on galaxy properties at z = 2.23}},
  doi          = {10.1093/mnras/stw322},
  volume       = {458},
  year         = {2016},
}

@article{11579,
  abstract     = {CR7 is the brightest z = 6.6 Ly α emitter (LAE) known to date, and spectroscopic follow-up by Sobral et al. suggests that CR7 might host Population (Pop) III stars. We examine this interpretation using cosmological hydrodynamical simulations. Several simulated galaxies show the same ‘Pop III wave’ pattern observed in CR7. However, to reproduce the extreme CR7 Ly α/He II1640 line luminosities (⁠Lα/HeII⁠) a top-heavy initial mass function and a massive ( ≳ 107 M⊙) Pop III burst with age ≲ 2 Myr are required. Assuming that the observed properties of Ly α and He II emission are typical for Pop III, we predict that in the COSMOS/UDS/SA22 fields, 14 out of the 30 LAEs at z = 6.6 with Lα > 1043.3 erg s−1 should also host Pop III stars producing an observable LHeII≳1042.7ergs−1⁠. As an alternate explanation, we explore the possibility that CR7 is instead powered by accretion on to a direct collapse black hole. Our model predicts Lα, LHeII⁠, and X-ray luminosities that are in agreement with the observations. In any case, the observed properties of CR7 indicate that this galaxy is most likely powered by sources formed from pristine gas. We propose that further X-ray observations can distinguish between the two above scenarios.},
  author       = {Pallottini, A. and Ferrara, A. and Pacucci, F. and Gallerani, S. and Salvadori, S. and Schneider, R. and Schaerer, D. and Sobral, D. and Matthee, Jorryt J},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, black hole physics, stars: Population III, galaxies: high-redshift},
  number       = {3},
  pages        = {2465--2470},
  publisher    = {Oxford University Press},
  title        = {{The brightest Lyα emitter: Pop III or black hole?}},
  doi          = {10.1093/mnras/stv1795},
  volume       = {453},
  year         = {2015},
}

@article{11583,
  abstract     = {Candidate galaxies at redshifts of z ∼ 10 are now being found in extremely deep surveys, probing very small areas. As a consequence, candidates are very faint, making spectroscopic confirmation practically impossible. In order to overcome such limitations, we have undertaken the CF-HiZELS survey, which is a large-area, medium-depth near-infrared narrow-band survey targeted at z = 8.8 Lyman α (Lyα) emitters (LAEs) and covering 10 deg2 in part of the SSA22 field with the Canada–France–Hawaii Telescope (CFHT). We surveyed a comoving volume of 4.7 × 106 Mpc3 to a Lyα luminosity limit of 6.3 × 1043舁erg舁s−1. We look for Lyα candidates by applying the following criteria: (i) clear emission-line source, (ii) no optical detections (ugriz from CFHTLS), (iii) no visible detection in the optical stack (ugriz > 27), (iv) visually checked reliable NBJ and J detections and (v) J − K ≤ 0. We compute photometric redshifts and remove a significant amount of dusty lower redshift line-emitters at z ∼ 1.4 or 2.2. A total of 13 Lyα candidates were found, of which two are marked as strong candidates, but the majority have very weak constraints on their spectral energy distributions. Using follow-up observations with SINFONI/VLT, we are able to exclude the most robust candidates as LAEs. We put a strong constraint on the Lyα luminosity function at z ∼ 9 and make realistic predictions for ongoing and future surveys. Our results show that surveys for the highest redshift LAEs are susceptible of multiple contaminations and that spectroscopic follow-up is absolutely necessary.},
  author       = {Matthee, Jorryt J and Sobral, David and Swinbank, A. M. and Smail, Ian and Best, P. N. and Kim, Jae-Woo and Franx, Marijn and Milvang-Jensen, Bo and Fynbo, Johan},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, cosmology: observations, dark ages, reionization, first stars},
  number       = {3},
  pages        = {2375--2387},
  publisher    = {Oxford University Press},
  title        = {{A 10 deg2 Lyman α survey at z=8.8 with spectroscopic follow-up: Strong constraints on the luminosity function and implications for other surveys}},
  doi          = {10.1093/mnras/stu392},
  volume       = {440},
  year         = {2014},
}