Related papers: Molecular chemistry and the missing mass problem i…
Molecular clouds are the principle stellar nurseries of our universe, keeping them in the focus of both observational and theoretical studies. From observations, some of the key properties of molecular clouds are well known but many…
Whenever observations are compared to theories, an estimate of the uncertainties associated with the observations is vital if the comparison is to be meaningful. However, many determinations of temperatures, densities and abundances in…
Comets have similar compositions to interstellar medium ices, suggesting at least some of their molecules maybe inherited from an earlier stage of evolution. To investigate the degree to which this might have occurred we compare the…
In this paper we discuss the calculation of chemical abundances in planetary nebulae and H II regions through ionization correction factors (ICFs). We review the first ICFs proposed in the literature based on ionization potential…
Planetary nebulae (PNe) are the only single stars in galaxies outside the Local Group that can be used as kinematic tracers of the diffuse light in the extended halo. Analysing their luminosity-specific number density across galaxies of…
We present deep high-resolution (R~15,000) and high-quality UVES optical spectrophotometry of nine planetary nebulae with dual-dust chemistry. We compute physical conditions from several diagnostics. Ionic abundances for a large number of…
Collisions between interstellar gas clouds are potentially an important mechanism for triggering star formation. This is because they are able to rapidly generate large masses of dense gas. Observationally, cloud collisions are often…
Binarity has been hypothesised to play an important, if not ubiquitous, role in the formation of planetary nebulae (PNe). Yet there remains a severe paucity of known binary central stars required to test the binary hypothesis and to place…
We analyse a large sample of galactic planetary nebulae based on their chemical composition and morphology. A recent morphological classification system is adopted, and several elements are considered, namely He, N, O, S, Ar, Ne, and C in…
We report results of an HST "snapshot" survey aimed at finding resolved binary companions of the central stars of Galactic planetary nebulae (PNe). Using WF/PC and WFPC2, we searched the fields of 113 PNe for stars whose close proximity to…
Planetary nebulae (PNe) are essential tracers of the kinematics of the diffuse halo and intracluster light where stellar spectroscopy is unfeasible, due to their strong emission lines. However, that is not all they can reveal about the…
Pre-stellar cores within molecular clouds provide the very initial conditions in which stars are formed. We use the IRAM 30m telescope and the PdBI to study the chemical and physical properties of the starless core FeSt 1-457 (Core 109), in…
[Abridged] Investigations of neutron(n)-capture element nucleosynthesis and chemical evolution have largely been based on stellar spectroscopy. However, the recent detection of these elements in several planetary nebulae (PNe) indicates…
(Abridged) Massive stars can determine the evolution of molecular clouds with their strong ultraviolet (UV) radiation fields. Moreover, UV radiation is relevant in setting the thermal gas pressure in star-forming clouds, whose influence can…
Carbon monoxide (CO) is a poor tracer of H$_{2}$ in the diffuse interstellar medium (ISM), where most of the carbon is not incorporated into CO molecules unlike the situation at higher extinctions. We present a novel, indirect method to…
High spectral resolution spectroscopy has proved to be very useful for the advancement of chemical abundances studies in photoionized nebulae, such as H II regions and planetary nebulae (PNe). Classical analyses make use of the intensity of…
Since the last IAU symposium on planetary nebulae (PNe), several deep spectroscopic surveys of the relatively faint optical recombination lines (ORLs) emitted by heavy element ions in PNe and H II regions have been completed. New diagnostic…
This paper presents a homogeneous study of abundances in a sample of 79 northern galactic planetary nebulae whose morphological classes have been uniformly determined. Ionic abundances and plasma diagnostics were derived from selected…
The past decade has led to significant improvements in our understanding of the physical structure of the molecular cores of cold dark clouds. Observational efforts, in combination with improved knowledge of cloud structure, now provide…
Understanding the chemical evolution in star-forming cores is a necessary pre-condition to correctly assess physical conditions when using molecular emission. We follow the evolution of chemistry and molecular line profiles through the…