Lyman-α Emitters in the context of hierarchical galaxy formation: predictions for VLT/MUSE surveys

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The VLT Multi Unit Spectroscopic Explorer (MUSE) integral-field spectrograph can detect Lyα emitters (LAE) in the redshift range 2.8 z 6.7 in a homogeneous way. Ongoing MUSE surveys will notably probe faint Lyα sources that are usually missed by current narrow-band surveys. We provide quantitative predictions for a typical wedding-cake observing strategy with MUSE based on mock catalogs generated with a semi-analytic model of galaxy formation coupled to numerical Lyα radiation transfer models in gas outflows. We expect ≈ 1500 bright LAEs (FLyα 10⁻¹⁷ erg s⁻¹ cm⁻²) in a typical Shallow Field (SF) survey carried over ≈ 100 arcmin², and ≈ 2,000 sources as faint as 10⁻¹⁸ erg s⁻¹ cm⁻² in a Medium-Deep Field (MDF) survey over 10 arcmin². In a typical Deep Field (DF) survey of 1 arcmin², we predict that ≈ 500 extremely faint LAEs (FLyα 4 × 10⁻¹⁹ erg s⁻¹ cm⁻²) will be found. Our results suggest that faint Lyα sources contribute significantly to the cosmic Lyα luminosity and SFR budget. While the host halos of bright LAEs at z ≈ 3 and 6 have descendants with median masses of 2 × 10¹² and 5 × 10¹³ M respectively, the faintest sources detectable by MUSE at these redshifts are predicted to reside in halos which evolve into typical sub-L* and L* galaxy halos at z = 0. We expect typical DF and MDF surveys to uncover the building blocks of Milky Way-like objects, even probing the bulk of the stellar mass content of LAEs located in their progenitor halos at z ≈ 3.