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| Paper: |
Identifying the Contributors to Cosmic Reionization with the Habitable World Observatory: LyC Escape Calibration in Faint Galaxies |
| Monograph: |
10, HWO25 Proceedings Part I: Community Science Case Development Documents |
| Page: |
189 |
| Authors: |
Annalisa Citro; Claudia. M. Scarlata; Cody A. Carr; Yumi Choi; Sophia R. Flury; Matthew J. Hayes; Anne Jaskot; Gagandeep Kaur; Alexandra Le Reste; Matilde Mingozzi; Themiya Nanayakkara; Sally Oey |
| DOI: |
10.26624/OMYP5652 |
| Abstract: |
Investigating how small-scale physical processes shape large-scale astrophysical phenomena is one of the
key science themes of the Astro2020 decadal Survey. An example of this interplay is Cosmic Reionization,
where ionizing photons from galaxies escaped into the intergalactic medium (IGM), driving its transition
from neutral to ionized at z>6. Star-forming galaxies are thought to be the dominant sources of reionization.
However, an open question remains as to whether bright or faint star-forming galaxies are the primary
reionization contributors. This depends on the escape fraction fLyC
esc—the fraction of ionizing photons that
successfully escape the galaxy’s interstellar and circumgalactic medium to reach the IGM. Performing direct
measurements of fLyC
esc during the reionization epoch is not feasible, due to the near-zero transmission of the
IGM at z ≳ 4. However, by calibrating fLyC
esc against indirect indicators (i.e., galaxy properties that correlate
with fLyC
esc) at lower redshifts, we can estimate its value in galaxies during reionization. Currently, fLyC
esc
calibrations are mostly limited to∼ 90 sources brighter MUV ∼ −18 at z∼0.3. Yet, recent models suggest
that fainter galaxies (down to MUV ∼ −13) may be the major contributors to reionization. Our science goal
is to extend fLyC
esc calibrations via indirect indicators to such faint magnitudes. With the Habitable Worlds
Observatory, we aim to achieve a ∼20-fold increase in statistical power. Additionally, we plan to reach
magnitudes as faint as 1/100 L∗ at z∼0.1. Suitable targets will be selected from the upcoming Ultraviolet
Explorer (UVEX) survey. Through this science case, we will be able to place robust constraints on the role of
faint galaxies in the reionization of the Universe and identify its primary contributors. |
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