TY  - JOUR
A1  - Schaerer, Daniel
A1  - Izotov, Yuri I.
A1  - Nakajima, K.
A1  - Worseck, Gabor
A1  - Chisholm, J.
A1  - Verhamme, A.
A1  - Thuan, T. X.
A1  - de Barros, S.
T1  - Intense C III] lambda lambda 1907,1909 emission from a strong Lyman continuum emitting galaxy
JF  - Astronomy and astrophysics : an international weekly journal
N2  - We have obtained the first complete ultraviolet (UV) spectrum of a strong Lyman continuum (LyC) emitter at low redshift - the compact, low-metallicity, star-forming galaxy J1154+2443 - with a Lyman continuum escape fraction of 46% discovered recently. The Space Telescope Imaging Spectrograph spectrum shows strong Ly alpha and C III] lambda 1909 emission, as well as O III] lambda 1666. Our observations show that strong LyC emitters can have UV emission lines with a high equivalent width (e.g. EW(C III]) = 11.7 +/- 2.9 angstrom rest-frame), although their equivalent widths should be reduced due to the loss of ionizing photons. The intrinsic ionizing photon production efficiency of J1154+2443 is high, log(xi(0)(ion)) = 25.56 erg(-1) Hz, comparable to that of other recently discovered z similar to 0.3-0.4 LyC emitters. Combining our measurements and earlier determinations from the literature, we find a trend of increasing xi(0)(ion) with increasing C III] lambda 1909 equivalent width, which can be understood by a combination of decreasing stellar population age and metallicity. Simple ionization and density-bounded photoionization models can explain the main observational features including the UV spectrum of J1154+2443.
KW  - galaxies: starburst
KW  - galaxies: high-redshift
KW  - dark ages, reionization, first stars
KW  - ultraviolet: galaxies
Y1  - 2018
U6  - https://doi.org/10.1051/0004-6361/201833823
SN  - 1432-0746
VL  - 616
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Izotov, Yuri I.
A1  - Chisholm, John
A1  - Worseck, Gábor
A1  - Guseva, Natalia G.
A1  - Schaerer, Daniel
A1  - Prochaska, Jason Xavier
T1  - Lyman alpha and Lyman continuum emission of Mg II-selected star-forming galaxies
JF  - Monthly notices of the Royal Astronomical Society
N2  - 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 O3Mg2 = [O III] lambda 5007/Mg II lambda 2796+2803 and Mg-2 = Mg II lambda 2796/Mg II lambda 2803 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 1 sigma upper limits of f(esc)(LyC) in the remaining three galaxies were derived. A strong narrow Ly alpha emission line with two peaks separated by V-sep similar to 298-592 km s(-1) was observed in four galaxies with detected LyC emission and very weak Ly alpha 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 greater than or similar to 1.3. A tendency of an increase of f(esc)(LyC) with increasing of both the O3Mg2 and Mg-2 is possibly present. However, there is substantial scatter in these relations not allowing their use for reliable prediction of f(esc)(LyC).
KW  - galaxies: abundances
KW  - galaxies: dwarf
KW  - galaxies: fundamental parameters
KW  - galaxies: ISM
KW  - galaxies: starburst
KW  - dark ages
KW  - reionization
KW  - first stars
Y1  - 2022
U6  - https://doi.org/10.1093/mnras/stac1899
SN  - 0035-8711
SN  - 1365-2966
VL  - 515
IS  - 2
SP  - 2864
EP  - 2881
PB  - Oxford University Press
CY  - Oxford
ER  -