Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-alpha emitters. (arXiv:2002.11117v1 [astro-ph.GA])

Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-alpha emitters. (arXiv:2002.11117v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Maseda_M/0/1/0/all/0/1">Michael V. Maseda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bacon_R/0/1/0/all/0/1">Roland Bacon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lam_D/0/1/0/all/0/1">Daniel Lam</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Matthee_J/0/1/0/all/0/1">Jorryt Matthee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brinchmann_J/0/1/0/all/0/1">Jarle Brinchmann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schaye_J/0/1/0/all/0/1">Joop Schaye</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Labbe_I/0/1/0/all/0/1">Ivo Labbe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schmidt_K/0/1/0/all/0/1">Kasper B. Schmidt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Boogaard_L/0/1/0/all/0/1">Leindert Boogaard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bouwens_R/0/1/0/all/0/1">Rychard Bouwens</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cantalupo_S/0/1/0/all/0/1">Sebastiano Cantalupo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Franx_M/0/1/0/all/0/1">Marijn Franx</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hashimoto_T/0/1/0/all/0/1">Takuya Hashimoto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Inami_H/0/1/0/all/0/1">Hanae Inami</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kusakabe_H/0/1/0/all/0/1">Haruka Kusakabe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mahler_G/0/1/0/all/0/1">Guillaume Mahler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nanayakkara_T/0/1/0/all/0/1">Themiya Nanayakkara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Richard_J/0/1/0/all/0/1">Johan Richard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wisotzki_L/0/1/0/all/0/1">Lutz Wisotzki</a>

While low-luminosity galaxies dominate number counts at all redshifts, their
contribution to cosmic Reionization is poorly understood due to a lack of
knowledge of their physical properties. We isolate a sample of 35 z~4-5
continuum-faint Lyman-alpha emitters from deep VLT/MUSE spectroscopy and
directly measure their Halpha emission using stacked Spitzer/IRAC Ch. 1
photometry. Based on Hubble Space Telescope imaging, we determine that the
average UV continuum magnitude is fainter than -16 (~0.01 L_star), implying a
median Lyman-alpha equivalent width of 249 Angstroms. By combining the Halpha
measurement with the UV magnitude we determine the ionizing photon production
efficiency, xi_ion, a first for such faint galaxies. The measurement of log
(xi_ion [Hz/erg]) = 26.28 (+0.28; -0.40) is in excess of literature
measurements of both continuum- and emission line-selected samples, implying a
more efficient production of ionizing photons in these lower-luminosity,
Lyman-alpha-selected systems. We conclude that this elevated efficiency can be
explained by stellar populations with metallicities between 4e-4 and 0.008,
with light-weighted ages less than 3 Myr.

http://arxiv.org/icons/sfx.gif