2022/02/01 by D. Schaerer, Y. I. Izotov, G. Worseck +13 · 60 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Hubble space telescope #Physics #Redshift #Space Telescope Imaging Spectrograph #Spectral line #Spectrograph #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1051/0004-6361/202243149
published in Astronomy and Astrophysics 658, L11 (EDP Sciences) · 6 pages, 3 figures; Accepted for publication in A\&A Letters
openalex publication_date 2022/02/01 · openalex created_date 2022/02/13 · arxiv created 2022/02/15 · arxiv updated 2022/03/02 · openalex updated_date 2026/08/05
Using the Space Telescope Imaging Spectrograph, we have obtained ultraviolet spectra from ∼1200 to 2000 Å of known Lyman continuum (LyC) emitting galaxies at low redshift ( z ∼ 0.3 − 0.4) with varying absolute LyC escape fractions ( f esc ∼ 0.01 − 0.72). Our observations include in particular the galaxy J1243+4646, which has the highest known LyC escape fraction at low redshift. While all galaxies are known Lyman alpha emitters, we consistently detect an inventory of additional emission lines, including C IV λ 1550, He II λ 1640, O III ] λ 1666, and C III ] λ 1909, whose origin is presumably essentially nebular. C IV λ 1550 emission is detected above 4 σ in six out of eight galaxies, with equivalent widths of EW(C IV ) = 12 − 15 Å for two galaxies, which exceeds the previously reported maximum emission in low- z star-forming galaxies. We detect C IV λ 1550 emission in all LyC emitters with escape fractions f esc > 0.1 and find a tentative increase in the flux ratio C IV λ 1550/C III ] λ 1909 with f esc . Based on the data, we propose a new criterion to select and classify strong leakers (galaxies with f esc > 0.1): C IV λ 1550/C III ] λ 1909 ≳ 0.75. Finally, we also find He II λ 1640 emission in all the strong leakers with equivalent widths from 3 to 8 Å rest frame. These are among the highest values observed in star-forming galaxies and are primarily due to a high rate of ionizing photon production. The nebular He II λ 1640 emission of the strong LyC emitters does not require harder ionizing spectra at > 54 eV compared to those of typical star-forming galaxies at similarly low metallicity.