TY  - JOUR
A1  - Draganova, Nadya
A1  - Richter, Philipp
A1  - Fechner, Cora
T1  - High-resolution observations of two O VI absorbers at z approximate to 2 toward PKS 1448-232
JF  - Astronomy and astrophysics : an international weekly journal
N2  - To explore the ionization conditions in highly-ionized absorbers at high redshift, we study in detail two intervening O vi absorbers at z approximate to 2 toward the quasar PKS 1448-232, based on high (R approximate to 75 000) and intermediate (R approximate to 45 000) resolution optical VLT/UVES spectra. We find that both absorption systems are composed of several narrow subcomponents with typical Civ/O VI Doppler-parameters of b < 10 km s(-1). This implies that the gas temperatures are T < 10(5) K and that the absorbers are photoionized by the UV background. The system at z = 2.1098 represents a simple, isolated O VI absorber that has only two absorption components and is relatively metal-rich (Z similar to 0.6 solar). Ioinization modeling implies that the system is photoionized with O VI, C IV, and H I coexisting in the same gas phase. The second system at z = 2.1660 represents a complicated, multi-component absorption system with eight O VI components spanning almost 300 km s(-1) in radial velocity. The photoionization modeling implies that the metallicity is non-uniform and relatively low (<= 0.1 solar) and that the O VI absorption must arise in a gas phase that differs from that traced by C IV, C III, and H I. Our detailed study of the two O VI systems towards PKS 1448-232 shows that multi-phase, multi-component high-ion absorbers similar to the one at z = 2.1660 can be described by applying a detailed ionization modeling of the various subcomponents to obtain reliable measurements of the physical conditions and the metal abundances in the gas.
KW  - intergalactic medium
KW  - quasars: absorption lines
KW  - cosmology: observations
Y1  - 2012
U6  - https://doi.org/10.1051/0004-6361/201116730
SN  - 0004-6361
VL  - 538
IS  - 1
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - THES
A1  - Draganova, Nadya
T1  - On the diversity of O VI absorbers at high redshift
Y1  - 2013
CY  - Potsdam
ER  -