• Canada
• Research softwareclose
• Other research productsclose
• 2012-2021close
• European Commission close
• CL close
• AR close
• English close

We present the first search for galaxy counterparts of intervening high-z (2 < z < 3.6) sub-damped Lyα absorbers (sub-DLAs) and DLAs towards gamma-ray bursts (GRBs). Our final sample comprises five intervening sub-DLAs and DLAs in four GRB fields. To identify candidate galaxy counterparts of the absorbers we used deep optical- and near-infrared imaging, and low-, mid- and high-resolution spectroscopy acquired with 6-m to 10-m class telescopes, the Hubble and the Spitzer Space Telescopes. Furthermore, we used the spectroscopic information and spectral-energy-distribution fitting techniques to study them in detail. Our main result is the detection and spectroscopic confirmation of the galaxy counterpart of the intervening DLA at z = 3.096 in the field of GRB 070721B (zGRB = 3.6298) as proposed by other authors. We also identify good candidates for the galaxy counterparts of the two strong Mg ii absorbers at z = 0.6915 and 1.4288 towards GRB 050820A (zGRB = 2.615). The properties of the detected DLA galaxy are typical for Lyman-break galaxies (LBGs) at similar redshifts; a young, highly star-forming galaxy that shows evidence for a galactic outflow. This supports thehypothesis that a DLA can be the gaseous halo of an LBG. In addition, we report a redshift coincidence of different objects associated with metal lines in the same field, separated by 130–161 kpc. The high detection rate of three correlated structures on a length scale as short as ~150 kpc in two pairs of lines of sight is intriguing. The absorbers in each of these are most likely not part of the same gravitationally bound structure. They more likely represent groups of galaxies.

Streamflow in south-central Chile (SCC, ∼ 37–42∘ S) is vital for agriculture, forestry production, hydroelectricity, and human consumption. Recent drought episodes have generated hydrological deficits with damaging effects on these activities. This region is projected to undergo major reductions in water availability, concomitant with projected increases in water demand. However, the lack of long-term records hampers the development of accurate estimations of natural variability and trends. In order to provide more information on long-term streamflow variability and trends in SCC, here we report findings of an analysis of instrumental records and a tree-ring reconstruction of the summer streamflow of the Río Imperial (∼ 37∘ 40′ S–38∘ 50′ S). This is the first reconstruction in Chile targeted at this season. Results from the instrumental streamflow record (∼ 1940 onwards) indicated that the hydrological regime is fundamentally pluvial with a small snowmelt contribution during spring, and evidenced a decreasing trend, both for the summer and the full annual record. The reconstruction showed that streamflow below the average characterized the post-1980 period, with more frequent, but not more intense, drought episodes. We additionally found that the recent positive phase of the Southern Annular Mode has significantly influenced streamflow. These findings agree with previous studies, suggesting a robust regional signal and a shift to a new hydrological scenario. In this paper, we also discuss implications of these results for water managers and stakeholders; we provide rationale and examples that support the need for the incorporation of tree-ring reconstructions into water resources management.