We present VLT/UVES spectroscopy of the quasar Q0841+129, whose spectrum shows a proximate damped Lyman-alpha (PDLA) absorber at z=2.47621 and a proximate sub-DLA at z=2.50620, both lying close in redshift to the QSO itself at z_em=2.49510+/-0.00003.
This fortuitous arrangement, with the sub-DLA acting as a filter that hardens the QSOs ionizing radiation field, allows us to model the ionization level in the foreground PDLA, and provides an interesting case-study on the origin of the high-ion absorption lines Si IV, C IV, and O VI in DLAs. The high ions in the PDLA show at least five components spanning a total velocity extent of ~160 km/s, whereas the low ions exist predominantly in a single component spanning just 30 km/s. We examine various models for the origin of the high ions. Both photoionization and turbulent mixing layer models are fairly successful at reproducing the observed ionic ratios after correcting for the non-solar relative abundance pattern, though neither model can explain all five components. We show that the turbulent mixing layer model, in which the high ions trace the interfaces between the cool PDLA gas and a hotter phase of shock-heated plasma, can explain the average high-ion ratios measured in a larger sample of 12 DLAs.
Q0151+048 is a physical QSO pair at z ~ 1.929 with a separation of 3.3 arcsec on the sky. In the spectrum of Q0151+048A (qA), a DLA is observed at a higher redshift. We have previously detected the host galaxies of both QSOs, as well as a Lya blob. W
e performed low-resolution spectroscopy with the slit aligned with the extended emission. We also observed the system using the medium-resolution VLT/X-shooter spectrograph and the slit aligned with the two QSOs. We measure systemic redshifts of zem(A)=1.92924{pm}0.00036 and zem(B)=1.92863{pm}0.00042 from the H{beta} and H{alpha} emission lines, respectively. We estimate the masses of the black holes of the two QSOs to be 10^9.33 M{odot} and 10^8.38 M{odot} for qA and qB, respectively. From this we infered the mass of the dark matter halos hosting the two QSOs: 10^13.74 M{odot} and 10^13.13 M{odot} for qA and qB, respectively. We observe a velocity gradient along the major axis of the Lya blob consistent with the rotation curve of a large disk galaxy, but it may also be caused by gas inflow or outflow. We detect residual continuum in the DLA trough which we interpret as emission from the host galaxy of qA. The derived H0 column density of the DLA is log NH0 = 20.34 {pm} 0.02. Metal column densities results in an overall metallicity of 0.01 Z{odot}. We detect CII* which allows us to make a physical model of the DLA cloud. From the systemic redshifts of the QSOs, we conclude that the Lya blob is associated with qA rather than with the DLA. The DLA must be located in front of both the Lya blob and qA at a distance larger than 30 kpc. The two QSOs accrete at normal eddington ratios. The DM halo of this double quasar will grow to the mass of our local super-cluster at z=0. We point out that those objects therefore form an ideal laboratory to study the physical interactions in a z=2 pre-cursor of our local super-cluster.
We continue our recent work to characterize the plasma content of high-redshift damped and sub-damped Lyman-alpha systems (DLAs/sub-DLAs), which represent multi-phase gaseous (proto)galactic disks and halos seen toward a background source. We survey
N V absorption in a sample of 91 DLAs and 18 sub-DLAs in the redshift range 1.67<z<4.28 with unblended coverage of the N V doublet, using data from VLT/UVES, Keck/HIRES, and Keck/ESI. In DLAs, we find eight secure N V detections, four marginal detections, and 79 non-detections. The detection rate of N V in DLAs is therefore 13^{+5}_{-4}%. Two sub-DLA N V detections are found among a sample of 18, at a similar detection rate of 11^{+15}_{-7}%. We show that the N V detection rate is a strong function of metallicity, increasing by a factor of ~4 at [N/H]=[NI/HI]>-2.3. The N V and CIV component b-value distributions in DLAs are statistically similar, but the median b(N V) of 18 km/s is lower than the median b(O VI) of 25 km/s. Some ~20% of the N V components have b<10 km/s and thus arise in warm photoionized plasma at log (T/K)<4.92; local sources of ionizing radiation (as opposed to the extragalactic background) are required to keep the cloud sizes physically reasonable. The nature of the remaining ~80% of (broad) N V components is unclear; models of radiatively-cooling collisionally-ionized plasma at log(T/K)=5.2-5.4 are fairly successful in reproducing the observed integrated high-ion column density ratios and the component line widths, but we cannot rule out photoionization by local sources. Finally, we identify several unusual DLAs with extremely low metallicity (<0.01 solar) but strong high-ion absorption [log N(N V)>14 or log N(O VI)>14.2] that present challenges to either galactic inflow or outflow models.
(Abridged) We use VLT/UVES high-resolution optical spectroscopy of seven GRB afterglows at z_GRB>2 to investigate circumburst and interstellar plasma in the host galaxies. Our sample consists of GRBs 021004, 050730, 050820, 050922C, 060607, 071031, a
nd 080310. Four of these spectra were taken in rapid-response mode, within 30 minutes of the Swift GRB detection. We identify several distinct categories of high-ion absorption at velocities close to z_GRB: (i) Strong high-ion components at z_GRB itself are always seen in OVI, CIV, and SiIV, and usually (in 6 of 7 cases) in NV. We discuss circumburst and interstellar models for the origin of this absorption. Using the non-detection of SIV* toward GRB 050730 together with a UV photo-excitation model, we place a lower limit of 400 pc on the distance of the SIV-bearing gas from the GRB. (ii) Complex, multi-component CIV and SiIV profiles extending over 100-400 km/s around z_GRB are observed in each spectrum; these velocity fields are similar to those measured in damped Lyman-alpha systems at similar redshifts, suggesting a galactic origin. (iii) Asymmetric, blueshifted, absorption-line wings covering 65-140 km/s are seen in the CIV, SiIV, and OVI profiles in 4 of the 7 spectra. The wing kinematics together with the observation that two wings show Galactic CIV/SiIV ratios suggest these features trace outflowing ISM gas in the GRB host galaxies. (iv) High-velocity (HV; 500-5000 km/s) components are detected in 6 of the 7 spectra. The HV components show diverse properties. In the cases of GRBs 071031 and 080310, both the ionization level (very high CIV/SiIV ratios and absence of neutral-phase absorption) and the kinematics of the HV components can be explained by Wolf-Rayet winds from the GRB progenitors.
