The mean H$alpha$ EW and Lyman-continuum photon production efficiency for faint $zapprox4-5$ galaxies. (arXiv:1902.02786v1 [astro-ph.GA])

The mean H$alpha$ EW and Lyman-continuum photon production efficiency for faint $zapprox4-5$ galaxies. (arXiv:1902.02786v1 [astro-ph.GA])
<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:+Bouwens_R/0/1/0/all/0/1">Rychard J. Bouwens</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:+Schaye_J/0/1/0/all/0/1">Joop Schaye</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:+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:+Boogaard_L/0/1/0/all/0/1">Leindert A. Boogaard</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:+Mahler_G/0/1/0/all/0/1">Guillaume Mahler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Urrutia_T/0/1/0/all/0/1">Tanya Urrutia</a>

We present the first measurements of the Lyman-continuum photon production
efficiency $xi_{textrm{ion,0}}$ at $zsim4$-5 for galaxies fainter than 0.2
$L^*$ ($-$19 mag). $xi_{textrm{ion,0}}$ quantifies the production rate of
ionizing photons with respect to the UV luminosity density assuming a fiducial
escape fraction of zero. Extending previous measurements of
$xi_{textrm{ion,0}}$ to the faint population is important, as ultra-faint
galaxies are expected to contribute the bulk of the ionizing emissivity. We
probe $xi_{textrm{ion,0}}$ to such faint magnitudes by taking advantage of
200-hour depth Spitzer/IRAC observations from the GREATS program and
$approx$300 3<$z$<6 galaxies with spectroscopic redshifts from the MUSE GTO Deep + Wide programs. Stacked IRAC [3.6]$-$[4.5] colors are derived and used to infer the H$alpha$ rest-frame equivalent widths, which range from 403r{A} to 2818r{A}. The derived $xi_{textrm{ion,0}}$ is $log_{10}(xi_{textrm{ion,0}} / textrm{Hz erg}^{-1}) = 25.36 pm 0.08$ over $-$20.5 < M$_{textrm{UV}}$ < $-$17.5, similar to those derived for brighter galaxy samples at the same redshift and therefore suggesting that $xi_{textrm{ion}}$ shows no strong dependence on $M_{UV}$. The $xi_{textrm{ion,0}}$ values found in our sample imply that the Lyman-continuum escape fraction for $M_{textrm{UV}} approx -19$ star-forming galaxies cannot exceed $approx$8-20% in the reionization era.

We present the first measurements of the Lyman-continuum photon production
efficiency $xi_{textrm{ion,0}}$ at $zsim4$-5 for galaxies fainter than 0.2
$L^*$ ($-$19 mag). $xi_{textrm{ion,0}}$ quantifies the production rate of
ionizing photons with respect to the UV luminosity density assuming a fiducial
escape fraction of zero. Extending previous measurements of
$xi_{textrm{ion,0}}$ to the faint population is important, as ultra-faint
galaxies are expected to contribute the bulk of the ionizing emissivity. We
probe $xi_{textrm{ion,0}}$ to such faint magnitudes by taking advantage of
200-hour depth Spitzer/IRAC observations from the GREATS program and
$approx$300 3<$z$<6 galaxies with spectroscopic redshifts from the MUSE GTO
Deep + Wide programs. Stacked IRAC [3.6]$-$[4.5] colors are derived and used to
infer the H$alpha$ rest-frame equivalent widths, which range from 403r{A} to
2818r{A}. The derived $xi_{textrm{ion,0}}$ is
$log_{10}(xi_{textrm{ion,0}} / textrm{Hz erg}^{-1}) = 25.36 pm 0.08$ over
$-$20.5 < M$_{textrm{UV}}$ < $-$17.5, similar to those derived for brighter
galaxy samples at the same redshift and therefore suggesting that
$xi_{textrm{ion}}$ shows no strong dependence on $M_{UV}$. The
$xi_{textrm{ion,0}}$ values found in our sample imply that the
Lyman-continuum escape fraction for $M_{textrm{UV}} approx -19$ star-forming
galaxies cannot exceed $approx$8-20% in the reionization era.

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