Related papers: Can X-rays provide a solution to the abundance dis…
We present VLT UVES echelle spectrophotometry of the Orion nebula in the 3100 to 10400 A range. We have measured the intensity of 555 emission lines, many of them corresponding to permitted lines of different heavy-element ions. This is the…
We propose a methodology to perform a self-consistent analysis of the physical properties of the emitting gas of HII galaxies adequate to the data that can be obtained with the XXI century technology. This methodology requires the…
Clusters of galaxies are thought to contain about ten times as much dark matter as baryonic matter. The dark component therefore dominates the gravitational potential of the cluster, and the baryons confined by this potential radiate X-rays…
In this contribution, we present the results of a study on the high abundance discrepancy factor (ADF $\sim$ 10) planetary nebula (PN) NGC 6153 with MUSE. We have constructed flux maps for dozens of emission lines, that allowed us to build…
X-ray absorption spectroscopy provides a potentially powerful tool in determining the metal abundances in various phases of the interstellar medium (ISM). We present a case study of the sight line toward 4U 1820-303 (Galactic coordinates l,…
The derivation of abundances in gaseous nebulae ionised by massive stars using optical collisionally excited emission lines is studied in this work comparing the direct or $T_e$ method with updated grids of photoionisation models covering a…
We report on medium resolution spectrophotometry of the Orion Nebula region, including for the first time the Extended Orion Nebula and the nearby M~43. The 49 long slit observations were divided into 99 smaller samples, which have allowed…
In this work we present a study of the strong optical collisional emission lines of Ne and Ar in an heterogeneous sample of ionized gaseous nebulae for which it is possible to derive directly the electron temperature and hence the chemical…
We present first strong observational evidence that the X-ray cool-core bias or the apparent bias in the abundance of relaxed clusters is absent in our REFLEX volume-limited sample (ReVols). We show that these previously observed biases are…
We present new observations of O II recombination lines in ten bright planetary nebulae, along with spatially-resolved measurements of O II and [O III] in the Ring nebula NGC 6720, to study the discrepancy between abundances derived from O…
Photoionization models of the giant HII region 30 Doradus are built and confronted to available UV, optical, IR (ISO) and radio spectra, under black-body or CoStar SEDs for the primary source and various density distributions for the…
Based on three years of deep observations of the Galactic center with the Chandra X-ray Observatory, we report the discovery of changes in the intensities and morphologies of two hard X-ray nebulosities. The nebulosities are dominated by…
Aims. The main objective of this article is to provide a simple physical framework with permits a quantitative comparison of measurements of the temperature fluctuations in the ionized interstellar medium with possible mechanisms which can…
Recent work (Corradi et al. 2015, Jones et al. 2016) has shown that the phenomenon of extreme abundance discrepancies, where recombination line abundances exceed collisionally excited line abundances by factors of 10 or more, seem to be…
Based on high quality observations of multiplet V1 of OII and the NLTE atomic computations of OII we study the density and temperature of a sample of HII regions. We find that the signature for oxygen rich clumps of high density and low…
A soft X-ray enhancement has recently been reported toward the high-velocity cloud MS30.7-81.4-118 (MS30.7), a constituent of the Magellanic Stream. In order to investigate the origin of this enhancement, we have analyzed two overlapping…
Bright clusters of galaxies can be seen out to cosmological distances, and thus they can be used to derive cosmological parameters. Although the continuum X-ray emission from the intra-cluster gas is optically thin, the optical depth of…
We present a tutorial on the determination of the physical conditions and chemical abundances in gaseous nebulae. We also include a brief review of recent results on the study of gaseous nebulae, their relevance for the study of stellar…
A recently generated theoretical line list of C II dielectronic recombination lines together with observational data gathered from the literature is used to investigate the electron temperature in a range of astronomical objects, mainly…
We model the X-rays reprocessed by an accretion disk in a fiducial low-mass X-ray binary system with a neutron star primary. An atmosphere, or the intermediate region between the optically thick disk and a Compton-temperature corona, is…