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28th of February 2018
ATNF Colloquium
Hunting for the first stars I: Attempts to demystify He II with MUSE
by Themiya Nanayakkara (Leiden)
Abstract. In the quest for identifying pop-III stars, the most sought-after emission line is He II, however, stellar population models are unable to accurately predict the He II features while being consistent with other emission line diagnostics. To produce He II ionizing photons, stellar populations require sources of hard ionizing radiation with energies >= 54.4 eV and sources such as AGN, shocks, X-Ray binaries, stellar rotation and/or binary stellar evolution, and post-AGB stars have been suggested as possible contributors. To accurately identify relative contributions from these wide variety of sources, high signal-to-noise spectra with rest-frame UV/optical coverage and advanced stellar population/photoionization models are required.
The VLT/MUSE GTO program has obtained deep ā‰ˆ10-30h exposures of the Hubble legacy fields yielding rest-UV spectra of galaxies at zā‰ˆ2-6. In this talk I will present recent results of the MUSE program and compare the z=2-4 He II emitters with expectations from photoionization modelling to explore their stellar population and ISM conditions. I will address the necessity to obtain high signal-to-noise spectra of individual galaxies to model rest UV emission and absorption systems along with auxiliary rest-NIR lines to constrain stellar population properties of galaxies at high-z, which will be aided by combined studies by MUSE and JWST in future. I will further briefly discuss the prospects of observing population IIII systems in the early universe.
The image above shows the MUSE (Multi Unit Spectroscopic Explorer) in 2013 at the Centre de Recherche Astrophysique de Lyon, France, just before it was shipped to Chile for installation on ESO's Very Large Telescope (Image credit: Eric Le Roux / Service Communication / UCBL / MUSE)

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