A bottom-up search for Lyman-continuum leakage in the Hubble Ultra Deep Field. (arXiv:2206.10799v3 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Rivera_Thorsen_T/0/1/0/all/0/1">T. Emil Rivera-Thorsen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hayes_M/0/1/0/all/0/1">Matthew Hayes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Melinder_J/0/1/0/all/0/1">Jens Melinder</a>

Context: Studies of the production and escape of Lyman Continuum from
galaxies often rely on array of indirect observational tracers in preselection
of candidate leakers.

Aims: Here, we investigate how much ionizing radiation might be missed due to
these selection criteria by completely removing them and performing a search
selected purely from rest-frame LyC emission; and how that affects our
estimates of the ionizing background.

Methods: We invert the conventional method and perform a bottom-up search for
Lyman-continuum leaking galaxies at redshifts $2 < z < 3.5$. Using archival
data from HST and VLT/MUSE, we run source finding software on UV-filter HST
images from the HUDF, and subject all detected sources to a series of tests to
eliminate those that are inconsistent with being ionizing sources.

Results: We find 6 new and one previously identified candidate leakers with
absolute escape fractions ranging from 36% to 100%. Our filtering criteria
eliminate one object previously reported as a candidate ionizing emitter in the
literature, while we report non-detection in the rest frame Lyman continuum of
two other previously reported sources. We find that our candidates make a
contribution to the metagalactic ionizing field of $log_{10}(epsilon_{nu}) =
25.32(+0.25)(-0.21)$ and $25.29(+0.27)(-0.22)$ erg/s/Hz/cMpc$^3$ for the full
set of candidates and for the 4 strongest candidates only; both values are
higher than but consistent with other recent figures in the literature.

Conclusions: Our findings suggest that galaxies that do not meet the usual
selection criteria may make a non-negligible contribution to the cosmic
ionizing field. We recommend that similar searches be carried out on a larger
scale in well-studied fields with both UV and large ancillary data coverage,
for example in the full set of CANDELS fields.

Context: Studies of the production and escape of Lyman Continuum from
galaxies often rely on array of indirect observational tracers in preselection
of candidate leakers.

Aims: Here, we investigate how much ionizing radiation might be missed due to
these selection criteria by completely removing them and performing a search
selected purely from rest-frame LyC emission; and how that affects our
estimates of the ionizing background.

Methods: We invert the conventional method and perform a bottom-up search for
Lyman-continuum leaking galaxies at redshifts $2 < z < 3.5$. Using archival
data from HST and VLT/MUSE, we run source finding software on UV-filter HST
images from the HUDF, and subject all detected sources to a series of tests to
eliminate those that are inconsistent with being ionizing sources.

Results: We find 6 new and one previously identified candidate leakers with
absolute escape fractions ranging from 36% to 100%. Our filtering criteria
eliminate one object previously reported as a candidate ionizing emitter in the
literature, while we report non-detection in the rest frame Lyman continuum of
two other previously reported sources. We find that our candidates make a
contribution to the metagalactic ionizing field of $log_{10}(epsilon_{nu}) =
25.32(+0.25)(-0.21)$ and $25.29(+0.27)(-0.22)$ erg/s/Hz/cMpc$^3$ for the full
set of candidates and for the 4 strongest candidates only; both values are
higher than but consistent with other recent figures in the literature.

Conclusions: Our findings suggest that galaxies that do not meet the usual
selection criteria may make a non-negligible contribution to the cosmic
ionizing field. We recommend that similar searches be carried out on a larger
scale in well-studied fields with both UV and large ancillary data coverage,
for example in the full set of CANDELS fields.

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