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The CALYMHA survey : Lyα luminosity function and global escape fraction of Lyα photons at z = 2.23

Sobral, David and Matthee, Jorryt and Best, Philip N. and Stroe, Andra and Röttgering, Huub J A and Oteo, Ivàn and Smail, Ian and Morabito, Leah and Paulino-Afonso, Ana (2017) The CALYMHA survey : Lyα luminosity function and global escape fraction of Lyα photons at z = 2.23. Monthly Notices of the Royal Astronomical Society, 466 (1). pp. 1242-1258. ISSN 0035-8711

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    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 L∗=1042.59−0.08+0.16 erg s−1, ϕ∗=10−3.09+0.14−0.34 ϕ∗=10−3.09−0.34+0.14 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.

    Item Type: Journal Article
    Journal or Publication Title: Monthly Notices of the Royal Astronomical Society
    Additional Information: This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version David Sobral, Jorryt Matthee, Philip Best, Andra Stroe, Huub Röttgering, Iván Oteo, Ian Smail, Leah Morabito, Ana Paulino-Afonso; The CALYMHA survey: Lyα luminosity function and global escape fraction of Lyα photons at z = 2.23. Mon Not R Astron Soc 2017; 466 (1): 1242-1258. doi: 10.1093/mnras/stw3090 is available online at: https://academic.oup.com/mnras/article/466/1/1242/2617718/
    Uncontrolled Keywords: galaxies: evolution ; galaxies: haloes ; galaxies: high-redshift ; galaxies: luminosity function ; mass function ; galaxies: statistics ; cosmology: observations
    Subjects:
    Departments: Faculty of Science and Technology > Physics
    ID Code: 84820
    Deposited By: ep_importer_pure
    Deposited On: 22 Feb 2017 10:08
    Refereed?: Yes
    Published?: Published
    Last Modified: 19 Jun 2018 05:30
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/84820

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