The REBELS ALMA Survey: efficient Ly alpha transmission of UV-bright z similar or equal to 7 galaxies from large velocity offsets and broad line widths

Research output: Contribution to journalJournal articleResearchpeer-review

Documents

  • stac3064

    Final published version, 2.51 MB, PDF document

  • Ryan Endsley
  • Daniel P. Stark
  • Rychard J. Bouwens
  • Sander Schouws
  • Renske Smit
  • Mauro Stefanon
  • Hanae Inami
  • Rebecca A. A. Bowler
  • Valentino Gonzalez
  • Manuel Aravena
  • Elisabete da Cunha
  • Pratika Dayal
  • Andrea Ferrara
  • Luca Graziani
  • Themiya Nanayakkara
  • Andrea Pallottini
  • Raffaella Schneider
  • Laura Sommovigo
  • Michael Topping
  • Paul van der Werf

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 alpha 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 alpha 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 similar to 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 alpha spectroscopy of eight UV-bright (M-UV similar to -22) galaxies at z similar or equal to 7 selected from the ALMA REBELS survey. We detect Ly alpha in four of eight galaxies and use the [C ii] systemic redshifts to investigate the Ly alpha velocity profiles. The Ly alpha lines are significantly redshifted from systemic (average velocity offset = 223 km s(-1)) and broad (FWHM approximate to 300-650 km s(-1)), with two sources showing emission extending to approximate to 750 km s(-1). We find that the broadest Ly alpha profiles are associated with the largest [C ii] line widths, suggesting a potential link between the Ly alpha FWHM and the dynamical mass. Since Ly alpha 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 alpha visibility of the most UV-luminous reionization-era galaxies.

Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Volume517
Issue number4
Pages (from-to)5642-5659
Number of pages18
ISSN0035-8711
DOIs
Publication statusPublished - 10 Nov 2022

    Research areas

  • galaxies: evolution, galaxies: high-redshift, dark ages, reionization, first stars, LYMAN-BREAK GALAXIES, STAR-FORMATION RATE, ULTRA-DEEP SURVEY, C II EMISSION, LUMINOSITY FUNCTION, COSMIC REIONIZATION, ACCELERATED REIONIZATION, INTERGALACTIC MEDIUM, ULTRAVIOLET-SPECTRA, INTERSTELLAR-MEDIUM

ID: 326729796