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

• Published in: Monthly notices of the Royal Astronomical Society 2018-08, Vol.478 (4), p.4851-4865
• Main Authors: Izotov, Y I, Worseck, G, Schaerer, D, Guseva, N G, Thuan, T X, Fricke, Verhamme, A, Orlitová, I
• Format: Article
• Language: English
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/sty1378

ABSTRACT We present observations with the Cosmic Origins Spectrograph (COS) 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 O32 = [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 fesc(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 Vsep varying from ∼153 to ∼345 km s−1. We find a general increase of the LyC escape fraction with increasing O32 and decreasing stellar mass M⋆, but with a large scatter of fesc(LyC). A tight anticorrelation is found between fesc(LyC) and Vsep making Vsep 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.