TY  - JOUR
A1  - Izotov, Y. I.
A1  - Schaerer, Daniel
A1  - Worseck, Gabor
A1  - Guseva, N. G.
A1  - Thuan, T. X.
A1  - Verhamme, A.
A1  - Orlitova, I.
A1  - Fricke, K. J.
T1  - J1154+2443: a low-redshift compact star-forming galaxy with a 46 per cent leakage of Lyman continuum photons
JF  - Monthly notices of the Royal Astronomical Society
N2  - We report the detection of the Lyman continuum (LyC) radiation of the compact star-forming galaxy (SFG) J1154+2443 observed with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope. This galaxy, at a redshift of z = 0.3690, is characterized by a high emission-line flux ratio O-32 = [O III] lambda 5007/[O II] lambda 3727 = 11.5. The escape fraction of the LyC radiation f(esc)(LyC) in this galaxy is 46 per cent, the highest value found so far in low-redshift SFGs and one of the highest values found in galaxies at any redshift. The narrow double-peaked Ly alpha emission line is detected in the spectrum of J1154+2443 with a separation between the peaks V-sep of 199 km s(-1), one of the lowest known for Ly alpha-emitting galaxies, implying a high f(esc)(Ly alpha). Comparing the extinction-corrected Ly alpha/H beta flux ratio with the case B value, we find f(esc)(Ly alpha) = 98 per cent. Our observations, combined with previous detections in the literature, reveal an increase of O-32 with increasing f(esc)(LyC). We also find a tight anticorrelation between f(esc)(LyC) and V-sep. The surface brightness profile derived from the COS acquisition image reveals a bright star-forming region in the centre and an exponential disc in the outskirts with a disc scale length alpha = 1.09 kpc. J1154+2443, compared to other known low-redshift LyC leakers, is characterized by the lowest metallicity, 12+log O/H = 7.65 +/- 0.01, the lowest stellar mass M-star = 108.20 M-circle dot, a similar star formation rate SFR = 18.9 M-circle dot yr(-1), and a high specific SFR of 1.2 x 10(-7) yr(-1).
KW  - galaxies: abundances
KW  - galaxies: dwarf
KW  - galaxies: fundamental parameters
KW  - galaxies: ISM
KW  - galaxies: starburst
KW  - dark ages, reionization, first stars
Y1  - 2017
U6  - https://doi.org/10.1093/mnras/stx3115
SN  - 0035-8711
SN  - 1365-2966
VL  - 474
IS  - 4
SP  - 4514
EP  - 4527
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Izotov, Y. I.
A1  - Worseck, Gábor
A1  - Schaerer, Daniel
A1  - Guseva, N. G.
A1  - Thuan, T. X.
A1  - Fricke, K. J.
A1  - Verhamme, Anne
A1  - Orlitova, I.
T1  - Low-redshift Lyman continuum leaking galaxies with high [O III]/[O II] ratios
JF  - Monthly notices of the Royal Astronomical Society
N2  - 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 O-32 = [O III]lambda 5007/[O II]lambda 3727 similar to 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 Ly alpha 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 similar to 153 to similar to 345 km s(-1). We find a general increase of the LyC escape fraction with increasing O-32 and decreasing stellar mass M-star, but with a large scatter of f(esc)(LyC). A tight anticorrelation 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.
KW  - galaxies: abundances
KW  - galaxies: dwarf
KW  - galaxies: fundamental parameters
KW  - galaxies: ISM
KW  - galaxies: starburst
KW  - dark ages, reionization, first stars
Y1  - 2018
U6  - https://doi.org/10.1093/mnras/sty1378
SN  - 0035-8711
SN  - 1365-2966
VL  - 478
IS  - 4
SP  - 4851
EP  - 4865
PB  - Oxford Univ. Press
CY  - Oxford
ER  -