Low-redshift Lyman continuum leaking galaxies with high [O iii]/[O ii] ratios

Abstract

We present observations with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope of five star-forming galaxies at redshifts z in the range 0.2993 -0.4317 and with high emission-line flux ratios O 32 = [O iii]λ5007/[O ii]λ3727 ∼ 8 -27 aiming to detect the Lyman continuum (LyC) emission. We detect LyC emission in all galaxies with the escape fractions f esc (LyC) in a range of 2 -72 per cent. A narrow Lyα emission line with two peaks in four galaxies and with three peaks in one object is seen in medium-resolution COS spectra with a velocity separation between the peaks V sep varying from ∼153 km s −1 to ∼ 345 km s −1 . We find a general increase of the LyC escape fraction with increasing O 32 and decreasing stellar mass M ⋆ , but with a large scatter of f esc (LyC). A tight anti-correlation is found between f esc (LyC) and V sep making V sep a good parameter for the indirect determination of the LyC escape fraction. We argue that one possible source driving the escape of ionizing radiation is stellar winds and radiation from hot massive stars.

The Lyman Continuum Escape Survey. II. Ionizing Radiation as a Function of the [O iii]/[O ii] Line Ratio

“…Robertson et al 2015 Figure 1). This contradiction is also apparent in low-redshift green pea galaxies (Izotov et al 2018b;Jaskot et al 2019). We evaluate this further in Figure 4 This diagram is widely used to examine the gas-phase metallicity and ionization state in the local universe (e.g.…”

Outside the Lyman-break box: detecting Lyman continuum emitters at 3.5 < z < 5.1 with CLAUDS

“…The high [OIII]/[OII] ratios, high densities and possible presence of shocks found in some GPs indicate that they may be leaking ionizing photons into the IGM (Jaskot & Oey 2013;Nakajima & Ouchi 2014;Faisst 2016). Research by Izotov et al (2016Izotov et al ( , 2018b reports the detection of escaping LyC radiation from four compact star-forming galaxies (SFGs) 1 with f esc ∼ 6-13%. More recently, the same group reported the highest f esc = 46 ± 2% detection to date in low redshift compact SFGs (Izotov et al 2018a).…”

The role of galaxies and AGN in reionizing the IGM – III. IGM–galaxy cross-correlations at z ∼ 6 from eight quasar fields with DEIMOS and MUSE

“…At z 4 where the escape fraction is directly measurable, it is found to be highly varying in individual objects but on average is around the ∼ 5 − 10 % required for reionisation (e.g. Shapley et al 2006;Izotov et al 2016Izotov et al , 2018Vanzella et al 2016Vanzella et al , 2018Steidel et al 2018;Fletcher et al 2019).…”