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  - 
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  -