* Astronomy

Title: Parsec-scale dust emission from the polar region in the type 2 nucleus of NGC 424
Authors: Sebastian F. Hoenig (1), Makoto Kishimoto (2), Robert Antonucci (1), Alessandro Marconi (3), M. Almudena Prieto (4), Konrad Tristram (2), Gerd Weigelt (2) ((1) UCSB, (2) MPIfR, (3) Univ. Firenze, (4) IAC)

Observations with Subaru telescope have detected surprisingly strong Lyman continuum (LyC; ~900 \AA\ in the rest-frame) from some Lyman alpha emitters (LAEs) at z=3.1. We have examined the stellar population which simultaneously accounts for the strength of the LyC and the spectral slope of non-ionising ultraviolet of the LAEs. As a result, we have found that stellar populations with metallicity Z\geq1/50 Z_\odot can explain the observed LyC strength only with a very top-heavy initial mass function (IMF; < m > ~ 50 solar masses). However, the critical metallicity for such an IMF is expected to be much lower. A very young (~1 Myr) and massive (~100 solar masses) extremely metal-poor (Z\leq5 x 10^{-4}Z_\odot) or metal-free (so-called Population III) stellar population can also reproduce the observed LyC strength if the mass fraction of such 'primordial' stellar population is ~1% in total stellar mass of the LAEs.

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