Related papers: The relation between column densities of interstel…
We measured the galactic hydrogen column densities to the neutron-star binaries GX 17+2, 4U 1705-44, and 4U 1728-34 by modeling the Mg and Si absorption edges found in high-resolution X-ray spectra obtained by the Chandra X-ray Observatory.…
We report on a comparison between 21 cm rotation measure (RM) and the optically-thin atomic hydrogen column density (N_HI) measured towards unresolved extragalactic sources in the Galactic plane of the northern sky. HI column densities…
We present an analysis of the Fe II, Ge II, Mg I, Mg II, S I, S II, Si II and Zn II interstellar lines for 63 stars. The column density of Mg II, S II, Si II and Zn II is well correlated with the distance. However, the column density --…
Ultra-high spectral resolution observations of time-varying interstellar absorption towards {\kappa} Vel are reported, using the Ultra-High Resolution Facility on the Anglo-Australian Telescope. Detections of interstellar Ca I, Ca II, K I,…
To complement the optical absorption-line survey of diffuse molecular gas in Paper I, we obtained and analyzed far ultraviolet H$_2$ and CO data on lines of sight toward stars in Cep OB2 and Cep OB3. Possible correlations between column…
We present measurements of the oxygen abundance of the Milky Way's ISM by observing the K-shell X-ray photoionization edge towards galaxy clusters. This effect is most easily observed towards objects with galactic columns (n_H) of a few…
We present high-resolution (FWHM ~ 0.3-1.5 km/s) spectra of interstellar Ca I absorption toward 30 Galactic stars. Comparisons of the column densities of Ca I, Ca II, K I, and other species -- for individual components identified in the…
The detection of complex organic molecules (COMs) toward cold sources such as pre-stellar cores (with T<10 K), has challenged our understanding of the formation processes of COMs in the interstellar medium. Recent modelling on COM chemistry…
The rotational transitions of carbon monoxide (CO) are the primary means of investigating the density and velocity structure of the molecular interstellar medium. Here we study the lowest four rotational transitions of CO towards…
Iram 30-m Observations towards eight protostellar outflow sources were taken in the 96-\SI{176}{\giga\hertz} range. Transitions of CH$_3$OH and CH$_3$CHO were detected in seven of them. The integrated emission of the transitions of each…
Molecular hydrogen being unobservable in cold molecular clouds, the column density measurements of molecular gas currently rely either on dust emission observation in the far-IR or on star counting. (Sub-)millimeter observations of numerous…
We have used the IRAM 30-m and FCRAO 14-m telescopes to observe the molecular clumps associated with 12 ultracompact (UC) HII regions in the J=6-5, 8-7 and 13-12 rotational transitions of methyl-acetylene (CH3C2H). Under the assumption of…
We present measurements of the column densities of interstellar DI, OI, NI, and H2 made with FUSE, and of HI made with IUE toward the sdO star LSE 44, at a distance of 554+/-66 pc. This target is among the seven most distant Galactic sight…
We investigate differences in the molecular abundances between magnetically super- and sub-critical prestellar cores, performing three-dimensional non-ideal magnetohydrodynamical (MHD) simulations with varying densities and magnetic field…
High quality archival spectra of interstellar absorption from C I toward 9 stars, taken with the Goddard High Resolution Spectrograph on the Hubble Space Telescope, were analyzed. Our sample was supplemented by two sight lines, 23 Ori and…
The Atacama Pathfinder Experiment (APEX) 12m telescope was used to observe the N=1-0, J=0-1 ground state transitions of OH+ at 909.1588 GHz with the CHAMP+ heterodyne array receiver. Two blended hyperfine structure transitions were detected…
We present a detailed analysis of a high resolution spectrum of the damped Ly$\alpha$ system at $z_{\rm abs}$~=~2.8112toward PKS~0528-250. The absorption redshift is slightly larger than the emission redshift of the quasar. We estimate the…
Methanol is an abundant molecule in space. The column density of CH$_3^{18}$OH is in some star-forming regions so high that the search for CH$_3^{17}$OH is promising. But only very few transition frequencies of CH$_3^{17}$OH with a…
We present new measurements of the interstellar gas-phase oxygen abundance along the sight lines towards 19 early-type galactic stars at an average distance of 2.6 kpc. We derive O {\small I} column densities from {\it HST}/STIS…
As an independent check on previous measurements of the isotopic abundance of oxygen through the Galaxy, we present a detailed analysis of the ground state rotational lines of 16OH and 18OH in absorption towards the giant molecular cloud…