Volume 616, August 2018
|Number of page(s)||5|
|Section||Letters to the Editor|
|Published online||24 August 2018|
Letter to the Editor
Intense C III] λλ1907,1909 emission from a strong Lyman continuum emitting galaxy
Observatoire de Genève, Universitéde Genève, 51 Ch. des Maillettes, 1290 Versoix, Switzerland
2 CNRS, IRAP, 14 Avenue E. Belin, 31400 Toulouse, France
3 Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, 14-b Metrolohichna str., Kyiv 03143, Ukraine
4 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
5 Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany
6 Astronomy Department, University of Virginia, PO Box 400325, Charlottesville, VA 22904-4325, USA
Accepted: 31 July 2018
We have obtained the first complete ultraviolet (UV) spectrum of a strong Lyman continuum (LyC) emitter at low redshift – the compact, low-metallicity, star-forming galaxy J1154+2443 – with a Lyman continuum escape fraction of 46% discovered recently. The Space Telescope Imaging Spectrograph spectrum shows strong Lyα and C III] λ1909 emission, as well as O III] λ1666. Our observations show that strong LyC emitters can have UV emission lines with a high equivalent width (e.g. EW(C III]) = 11.7 ± 2.9 Å rest-frame), although their equivalent widths should be reduced due to the loss of ionizing photons. The intrinsic ionizing photon production efficiency of J1154+2443 is high, log(ξ0ion = 25.56 erg−1 Hz), comparable to that of other recently discovered z ~ 0.3−0.4 LyC emitters. Combining our measurements and earlier determinations from the literature, we find a trend of increasing ξ0ion with increasing C III] λ1909 equivalent width, which can be understood by a combination of decreasing stellar population age and metallicity. Simple ionization and density-bounded photoionization models can explain the main observational features including the UV spectrum of J1154+2443.
Key words: galaxies: starburst / galaxies: high-redshift / dark ages, reionization, first stars / ultraviolet: galaxies
© ESO 2018
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