Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z > 7
Abstract
Although low-mass star-forming galaxies are the leading candidates of the reionization process, we cannot conclusively rule out high-mass star-forming galaxies as candidates. While most simulations indicate the former is the best candidate, some models suggest that at z ≥ 6 massive, UV-bright galaxies - "oligarchs" - account for at least 80% of the ionizing budget. To test this hypothesis, we target massive ( ${\mathrm{log}}_{10}({\text{}}{M}_{\star }[{\text{}}{M}_{\odot }])\gt 10$ ), UV-bright (M UV ~ -22) Lyα emitters at z > 7 in archival data, observed with similar resolution spectrographs (Very Large Telescope/X-shooter and Keck/MOSFIRE). To increase the reliability of our conclusions, we stack all spectra and obtain a deep-stacked spectrum of 24.75 hr. The stacked Lyα profile displays a clear asymmetric red peak and an absence of a blue peak. We additionally estimate the intrinsic stacked Lyα profile of our targets by correcting for intergalactic medium (IGM) transmission using a range of neutral hydrogen fractions, finding no significant change in the profile. We measure a velocity offset V red > 300 km s-1 and an asymmetry in our red peak A ~ 3. Using various models and estimators, such as the peak separation, the asymmetry of the red peak, the ratio between Lyα and Hβ, and the β slope, we conclude that the escape fraction in these three UV-bright, massive (~1010 M ⊙), z ≥ 7 galaxies is f esc(LyC) ≤ 10%.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2023
- DOI:
- 10.3847/1538-4357/acac9d
- arXiv:
- arXiv:2301.03599
- Bibcode:
- 2023ApJ...944...61W
- Keywords:
-
- Lyman-alpha galaxies;
- Reionization;
- High-redshift galaxies;
- 978;
- 1383;
- 734;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 11 pages, 4 figures, 2 tables. Accepted for publication in ApJ