TY - JOUR A1 - Schaerer, Daniel A1 - Izotov, Yuri I. A1 - Worseck, Gábor A1 - Berg, Danielle A1 - Chisholm, John A1 - Jaskot, Anne A1 - Nakajima, Kimihiko A1 - Ravindranath, Swara A1 - Thuan, Trinh X. A1 - Verhamme, Anne T1 - Strong Lyman continuum emitting galaxies show intense C IV λ 1550 emission JF - Astronomy and astrophysics N2 - Using the Space Telescope Imaging Spectrograph, we have obtained ultraviolet spectra from similar to 1200 to 2000 angstrom of known Lyman continuum (LyC) emitting galaxies at low redshift (z similar to 0.3-0.4) with varying absolute LyC escape fractions ( f(esc) similar to 0.01-0.72). Our observations include in particular the galaxy J1243+4646, which has the highest known LyC escape fraction at low redshift. While all galaxies are known Lyman alpha emitters, we consistently detect an inventory of additional emission lines, including C IV lambda 1550, He II lambda 1640, O III] lambda 1666, and C III] lambda 1909, whose origin is presumably essentially nebular. C IV lambda 1550 emission is detected above 4 sigma in six out of eight galaxies, with equivalent widths of EW(C IV) = 12-15 angstrom for two galaxies, which exceeds the previously reported maximum emission in low-z star-forming galaxies. We detect C IV lambda 1550 emission in all LyC emitters with escape fractions f(esc) > 0.1 and find a tentative increase in the flux ratio C IV lambda 1550 /C III] lambda 1909 with f(esc). Based on the data, we propose a new criterion to select and classify strong leakers (galaxies with f(esc) > 0.1): C IV lambda 1550 /C III] lambda 1909 greater than or similar to 0.75. Finally, we also find He II lambda 1640 emission in all the strong leakers with equivalent widths from 3 to 8 angstrom rest frame. These are among the highest values observed in star-forming galaxies and are primarily due to a high rate of ionizing photon production. The nebular He II lambda 1640 emission of the strong LyC emitters does not require harder ionizing spectra at >54 eV compared to those of typical star-forming galaxies at similarly low metallicity. KW - galaxies: starburst KW - galaxies: high-redshift KW - dark ages, reionization KW - first stars KW - ultraviolet: galaxies Y1 - 2022 U6 - https://doi.org/10.1051/0004-6361/202243149 SN - 0004-6361 SN - 1432-0746 VL - 658 PB - EDP Sciences CY - Les Ulis ER - 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 - Furniss, Amy A1 - Worseck, Gabor A1 - Fumagalli, Michele A1 - Johnson, Caitlin A. A1 - Williams, David A. A1 - Pontrelli, P. A1 - Prochaska, J. Xavier T1 - Spectroscopic Redshift of the Gamma-Ray Blazar B2 1215+30 from Ly alpha Emission JF - The astronomical journal N2 - We report on Cosmic Origin Spectrograph observations of the gamma-ray bright blazar B2 1215+30, collected in 2015 November. These observations allow for the confirmation of the source redshift from the detection of a Lyα emission feature at λ ~ 1374 Å. The emission feature places the source at a redshift of z = 0.1305 ± 0.003, confirming the source's ground-based spectral measurement. The gamma-ray emission of the source is discussed in the context of the source distance, required for the accurate reconstruction of the intrinsic gamma-ray emission taking the absorption by the extragalactic background light into account. The source distance is found to be low enough that the previously reported detection of an exceptional flaring event from B2 1215+30 in 2014 cannot be used to investigate opacity-specific spectral and variability characteristics introduced by possible ultra-high-energy cosmic-ray propagation. KW - galaxies:distances and redshifts KW - galaxies: individual (B2 1215+30) KW - gamma rays: galaxies KW - ultraviolet: galaxies Y1 - 2019 U6 - https://doi.org/10.3847/1538-3881/aaf28b SN - 0004-6256 SN - 1538-3881 VL - 157 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER -