Lyman alpha and Lyman continuum emission of Mg ii-selected star-forming galaxies. Issue 2 (22nd July 2022)

• Record Type: Journal Article
• Authors: Izotov, Y I; Chisholm, J; Worseck, G; Guseva, N G; Schaerer, D; Prochaska, J X
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 515:Issue 2(2022)
• Page Start: 2864
• Page End: 2881
• Publication Date: 2022-07-22
• Subjects: galaxies: abundances -- galaxies: dwarf -- galaxies: fundamental parameters -- galaxies: ISM -- galaxies: starburst -- dark ages, reionization, first stars; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac1899
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present observations with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope of seven compact low-mass star-forming galaxies at redshifts, z, in the range 0.3161–0.4276, with various O3 Mg2 = [O iii ] λ5007/Mg ii λ2796+2803 and Mg2 = Mg ii λ2796/Mg ii λ2803 emission-line ratios. We aim to study the dependence of leaking Lyman continuum (LyC) emission on the characteristics of Mg ii emission together with the dependencies on other indirect indicators of escaping ionizing radiation. LyC emission with escape fractions f esc (LyC) = 3.1–4.6 per cent is detected in four galaxies, whereas only 1σ upper limits of f esc (LyC) in the remaining three galaxies were derived. A strong narrow Lyα emission line with two peaks separated by $V_{\rm sep}\, \sim$ 298–592 km s −1 was observed in four galaxies with detected LyC emission and very weak Lyα emission is observed in galaxies with LyC non-detections. Our new data confirm the tight anticorrelation between f esc (LyC) and V sep found for previous low-redshift galaxy samples. V sep remains the best indirect indicator of LyC leakage among all considered indicators. It is found that escaping LyC emission is detected predominantly in galaxies with Mg$_2\, \gtrsim$ 1.3. A tendency of an increase of f esc (LyC) with increasing of both the O3 Mg2 and Mg2 is possibly present. However, there is substantial scatter in these relations not allowing their use for reliable prediction of f esc (LyC).