Back to Search
Start Over
REBELS ALMA Survey: efficient Ly α transmission of UV-bright z ≃ 7 galaxies from large velocity offsets and broad line widths.
- Source :
- Monthly Notices of the Royal Astronomical Society; Dec2022, Vol. 517 Issue 4, p5642-5659, 18p
- Publication Year :
- 2022
-
Abstract
- Recent work has shown that UV-luminous reionization-era galaxies often exhibit strong Lyman-alpha emission despite being situated at redshifts where the IGM is thought to be substantially neutral. It has been argued that this enhanced Ly α transmission reflects the presence of massive galaxies in overdense regions which power large ionized bubbles. An alternative explanation is that massive galaxies shift more of their Ly α profile to large velocities (relative to the systemic redshift) where the IGM damping wing absorption is reduced. Such a mass-dependent trend is seen at lower redshifts, but whether one exists at z ∼ 7 remains unclear owing to the small number of existing systemic redshift measurements in the reionization era. This is now changing with the emergence of [C ii ]-based redshifts from ALMA. Here, we report MMT/Binospec Ly α spectroscopy of eight UV-bright (M<subscript>UV</subscript> ∼ −22) galaxies at z ≃ 7 selected from the ALMA REBELS survey. We detect Ly α in four of eight galaxies and use the [C ii ] systemic redshifts to investigate the Ly α velocity profiles. The Ly α lines are significantly redshifted from systemic (average velocity offset = 223 km s<superscript>–1</superscript>) and broad (FWHM ≈ 300–650 km s<superscript>−1</superscript>), with two sources showing emission extending to ≈750 km s<superscript>−1</superscript>. We find that the broadest Ly α profiles are associated with the largest [C ii ] line widths, suggesting a potential link between the Ly α FWHM and the dynamical mass. Since Ly α photons at high velocities transmit efficiently through the z  = 7 IGM, our data suggest that velocity profiles play a significant role in boosting the Ly α visibility of the most UV-luminous reionization-era galaxies. [ABSTRACT FROM AUTHOR]
- Subjects :
- GALAXIES
REDSHIFT
VELOCITY
GALACTIC evolution
GALACTIC redshift
Subjects
Details
- Language :
- English
- ISSN :
- 00358711
- Volume :
- 517
- Issue :
- 4
- Database :
- Complementary Index
- Journal :
- Monthly Notices of the Royal Astronomical Society
- Publication Type :
- Academic Journal
- Accession number :
- 160354296
- Full Text :
- https://doi.org/10.1093/mnras/stac3064