The Multi Unit Spectroscopic Explorer (MUSE), a relatively new addition to the Very Large Telescope, has already produced impressive results due to its unprecedented ability to instantaneously acquire more than 1.5 million spectra within its one-square-arcminute field of view of the sky. Renske Smit and colleagues (Mon. Not. R. Astron. Soc. http://doi.org/bzqw; 2017) used MUSE, together with data from the Hubble Space Telescope and SINFONI — another spectrograph on the Very Large Telescope — to look at galaxies hiding behind a massive local cluster of galaxies, which acts as an enormous magnifying glass due to its gravitational field. The large wavelength coverage of the spectrograph and its integral-field capability mean that data can be used to create composite images combining both continuum emission and emission lines (pictured).
Furthermore, the detection of carbon emission at rest-frame ultraviolet wavelengths was a surprise, given its relative absence in local analogues of this type of galaxy. However, as the authors note, their results indicate that the C IV doublet line may become increasingly common at higher redshifts, where young and metal-poor stellar populations start to dominate. Observations of this emission line doublet may therefore prove instrumental in the upcoming era of the James Webb Space Telescope for the study of galaxies during the epoch of reionization, at even higher redshifts (>7), where most Lyα photons would be absorbed by the still largely neutral intergalactic medium.
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