• A bright lensed galaxy at z = 5.4 with strong Lyα emission

      McGreer, Ian D; Clément, Benjamin; Mainali, Ramesh; Stark, Daniel P; Gronke, Max; Dijkstra, Mark; Fan, Xiaohui; Bian, Fuyan; Frye, Brenda; Jiang, Linhua; et al. (OXFORD UNIV PRESS, 2018-09)
      We present a detailed study of an unusually bright, lensed galaxy at z = 5.424 discovered within the CFHTLS imaging survey. With an observed flux of i(AB) = 23.0, J141446.82+544631.9 is one of the brightest galaxies known at z > 5. It is characterized by strong Ly alpha emission, reaching a peak in (observed) flux density of >10 (16)erg s (1) cm (2)angstrom (1). A deep optical spectrum from the Large Binocular Telescope places strong constraints on Nv and C IV emission, disfavouring an Active Galactic Nucleus (AGN) source for the emission. However, a detection of the NIV] lambda 1486 emission line indicates a hard ionizing continuum, possibly from hot, massive stars. Resolved imaging from HST deblends the galaxy from a foreground interloper; these observations include narrowband imaging of the Ly alpha emission, which is marginally resolved on approximately lbw kpc scales and has EW0 similar to 260 angstrom. The Ly alpha emission extends over similar to 2000 km s (1) and is broadly consistent with expanding shell models. Spectral energy distribution fitting that includes Spitzer/IRAC photometry suggests a complex star formation history that includes both a recent burst and an evolved population. J1414+5446 lies 30 arcsec from the centre of a known lensing cluster in the CFHTLS; combined with the foreground contribution, this leads to a highly uncertain estimate for the lensing magnification in the range 5 less than or similar to mu less than or similar to 25. Because of its unusual brightness, J1414+5446 affords unique opportunities for detailed study of an individual galaxy near the epoch of re-ionization and a preview of what can be expected from upcoming wide-area surveys that will yield hundreds of similar objects.