Related papers: Can X-rays provide a solution to the abundance dis…

In a very recent work, [1] claim that the scenario of temperature inhomogeneities proposed by [2] ($t2$ > 0) is not able to explain the O$^{2+}$/H$^{+}$ abundance discrepancy observed between the calculations based on the optical [OIII]…

The errors inherent to the use of the standard "ionization correction factor" ("i_CF") method of calculating nebular conditions and relative abundances of H, He, N, O, Ne, S, and Ar in emission line nebulae have been investigated under…

(Abridged) Results from the first dedicated study of Galactic PNe by means of optical integral field spectroscopy with the VLT FLAMES Argus IFU are presented. Three typical Galactic-disk PNe have been mapped with the 11.5''x7.2'' Argus…

The determination of the heavy element abundances from giant extragalactic H II regions is based on collisionally excited lines. We argue that in the presence of temperature variations the abundances determined are lower limits to the real…

The "abundance discrepancy" problem in the study of planetary nebulae (PNe), viz., the problem concerning systematically higher heavy-element abundances derived from optical recombination lines relative to those from collisionally excited…

Context. X-ray flares are common phenomena in pre-main sequence stars. Their analysis gives insights into the physics at work in young stellar coronae. The Orion Nebula Cluster offers a unique opportunity to study large samples of young low…

Emission-line abundances have been uncertain for more than a decade due to unexplained discrepancies in the relative intensities of the forbidden lines and weak permitted recombination lines in planetary nebulae (PNe) and H II regions. The…

We present chemical abundances of carbon (C) and oxygen (O) in the Large and Small Magellanic Clouds from deep and high-quality optical spectra of HII regions. The data have been taken using the Ultraviolet-Visual Echelle Spectrograph at…

Photoionization produces supra-thermal electrons, electrons with much more energy than is found in a thermalized gas at electron temperatures characteristic of nebulae. The presence of these high energy electrons may solve the long-standing…

This paper is the third in a series reporting on a study of carbon abundances in a carefully chosen sample of planetary nebulae representing a large range in progenitor mass and metallicity. We make use of the IUE Final Archive database…

We present results from integral field spectroscopy with PMAS. The observed field contains: five protoplanetary discs (also known as proplyds), the high-velocity jet HH 514 and a bowshock. Spatial distribution maps are obtained for…

We argue that the discrepancies observed in HII regions between abundances derived from optical recombination lines (ORLs) and collisionally excited lines (CELs) might well be the signature of a scenario of the enrichment of the…

We simulate the formation of a large X-ray cluster using a fully 3D hydrodynamical code coupled to a Particle-Mesh scheme which models the dark matter component. We focus on a possible decoupling between electrons and ions temperatures. We…

For bare lead ions, decelerated to the low beam energy of 10 MeV/u, the x-ray emission associated with radiative recombination (RR) at "cold collision" conditions has been studied at the electron cooler of CRYRING@ESR at GSI-Darmstadt.…

The shape of the ionising spectra of galaxies is a key ingredient to reveal their physical properties and to our understanding of the ionising background radiation. A long-standing unsolved problem is the presence of HeII nebular emission…

We measure the metal abundance ratios in the X-ray photoionized gas located near the narrow line region of a sample of Seyfert 2 AGN. The high-resolution X-ray spectra observed with the Chandra high- and low-energy transmission grating…

(Abridged) We use high S/N spectra of 20 HII regions in the giant spiral galaxy M101 to derive electron temperatures for the HII regions and robust metal abundances over radii R = 0.19-1.25 Ro (6-41 kpc). We compare the consistency of…

Using ab-initio photoionization models of giant HII regions, we test methods for abundance determinations based on a direct measurement of the electron temperature, now possible even for moderate to high-metallicity objects. We find that,…

We have compared Monte Carlo photoionization models of H II regions with a uniform density distribution with models with the same central stars and chemical compositions but with 3-D hierarchical clumps. We compare the abundances of He, N,…

(Abridged) Context: Both X-ray and radio observations offer insight into the high-energy processes of young stellar objects (YSOs). The observed thermal X-ray emission can be accompanied by both thermal and nonthermal radio emission. Due to…