Citation for published item:orlD hF nd wttheeD tF nd festD F nd troeD eF nd ¤ ottgeringD rF nd yteoD sF nd milD sF nd woritoD vF nd ulinoEefonsoD eF @PHIUA 9he gevwre survey X vy luminosity funtion nd glol espe frtion of vy photons t z a PFPQF9D wonthly noties of the oyl estronomil oietyFD RTT @IAF ppF IPRPEIPSVF Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTWe 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 ∼10 42.3 erg s −1 . We find 188 Lyα emitters over 7.3 × 10 5 Mpc 3 , 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 , 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.

We report the identification of an extreme proto-cluster of galaxies in the early Universe whose core (nicknamed Dusty Red Core, DRC, because of its very red color in the Herschel SPIRE 250-, 350and 500-µm bands) is formed by at least ten dusty star-forming galaxies (DSFGs), spectroscopically confirmed to lie at z spec = 4.002 via detection of [C i](1-0), 12 CO(6-5), 12 CO(4-3), 12 CO(2-1) and H 2 O(2 11 − 2 02 ) emission lines, detected using ALMA and ATCA. The spectroscopically-confirmed components of the proto-cluster are distributed over a 260 kpc × 310 kpc region and have a collective obscured star-formation rate (SFR) of ∼ 6500 M ⊙ yr −1 , considerably higher than has been seen before in any proto-cluster of galaxies or over-densities of DSFGs at z 4. Most of the star formation is taking place in luminous DSFGs since no Lyα emitters are detected in the proto-cluster core, apart from a Lyα blob located next to one of the DRC dusty components, extending over 60 kpc. The total obscured SFR of the proto-cluster could rise to SFR ∼ 14, 400 M ⊙ yr −1 if all the members of an over-density of bright DSFGs discovered around DRC in a wide-field LABOCA 870-µm image are part of the same structure. [C i](1-0) emission reveals that DRC has a total molecular gas mass of at least M H2 ∼ 6.6 × 10 11 M ⊙ , and its total halo mass could be as high as ∼ 4.4 × 10 13 M ⊙ , indicating that it is the likely progenitor of a cluster at least as massive as Coma at z = 0. The relatively short gas-depletion times of the DRC components suggest either the presence of a mechanism able to trigger extreme star formation simultaneously in galaxies spread over a few hundred kpc or the presence of gas flows from the cosmic web able to sustain star formation over several hundred million years.