We present HIRES observations for 30 damped Lyman alpha systems, selected on the basis of their large metal column densities from previous, lower resolution data. The measured metal column densities for Fe, Zn, S, Si, Cr, Mn, and Ni are provided for
these 30 systems. Combined with previously observed large metal column density damped Lyman alpha systems, we present a sample of 44 damped Lyman alpha systems observed with high resolution spectrographs (R~30000). These damped Lyman alpha systems probe the most chemically evolved systems at redshifts greater than 1.5. We discuss the context of our sample with the general damped Lyman alpha population, demonstrating that we are probing the top 10% of metal column densities with our sample. In a companion paper, we will present an analysis of the samples elemental abundances in the context of galactic chemical enrichment.
We have investigated dissociative recombination (DR) of NH$^+$ with electrons using a merged beams configuration at the TSR heavy-ion storage ring located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. We present our measured
absolute merged beams recombination rate coefficient for collision energies from 0 to 12 eV. From these data we have extracted a cross section which we have transformed to a plasma rate coefficient for the collisional plasma temperature range from $T_{rm pl} = 10$ to $18000$ K. We show that the NH$^+$ DR rate coefficient data in current astrochemical models are underestimated by up to a factor of $sim 9$. Our new data will result in predicted NH$^+$ abundances lower than calculated by present models. This is in agreement with the sensitivity limits of all observations attempting to detect NH$^+$ in interstellar clouds.
The relation between the stellar mass and size of a galaxys structural subcomponents, such as discs and spheroids, is a powerful way to understand the processes involved in their formation. Using very large catalogues of photometric bulge+disc struct
ural decompositions and stellar masses from the Sloan Digital Sky Survey Data Release Seven, we carefully define two large subsamples of spheroids in a quantitative manner such that both samples share similar characteristics with one important exception: the bulges are embedded in a disc and the pure spheroids are galaxies with a single structural component. Our bulge and pure spheroid subsample sizes are 76,012 and 171,243 respectively. Above a stellar mass of ~$10^{10}$ M$_{odot}$, the mass-size relations of both subsamples are parallel to one another and are close to lines of constant surface mass density. However, the relations are offset by a factor of 1.4, which may be explained by the dominance of dissipation in their formation processes. Whereas the size-mass relation of bulges in discs is consistent with gas-rich mergers, pure spheroids appear to have been formed via a combination of dry and wet mergers.
We present the first systematic study of boron beyond the Local Group. This analysis is performed on a sample of 30 damped Ly{alpha} systems (DLAs) with strong metal-lines, which are expected to trace the interstellar medium of high z galaxies. We re
port on two boron detections at > 3{sigma} significance; one new detection and one confirmation. The ratios of B/O and, for the first time, B/S are compared with previous stellar and interstellar measurements in the Milky Way and Small Magellanic Cloud. The novel comparison with sulphur, which tracks oxygens abundance, alleviates the uncertainty associated with stellar oxygen measurements. For both detections, the inferred B/S ratio is in excess of the prediction of primary boron production from spallation processes. Possible sources of contamination are discussed, as well as physical effects that could impact the observed ratios. However taken at face value, the implication of these measurements suggest potentially higher cosmic ray fluxes in DLAs. The prospects for future boron detections in other high redshift DLAs to confirm our results is also discussed.
