Atomic data from the Iron Project.XLIV. Transition probabilities and line ratios for Fe VI with fluorescent excitation in planetary nebulae

[Fe II] emission lines are prominent in the infrared (IR), and they are important diagnostic tools for radiative atomic shocks. We investigate the emission characteristics of [Fe II] lines using a shock code developed by Raymond (1979) with updated atomic parameters. We first review general characteristics of IR [Fe II] emission lines from shocked gas, and derive [Fe II] line fluxes as a function of shock speed and ambient density. We have compiled the available IR [Fe II] li...

Fluorescent excitation of spectral lines is demonstrated as a function of temperature-luminosity and the distance of the emitting region from the central stars of planetary nebulae. The electron densities and temperatures are determined, and the method is exemplified through a detailed analysis of spectral observations of a high excitation PN, NGC 6741, observed by Hyung and Aller(1997). Fluorescence should also be important in the determination of element abundances. It is s...

We use the PyNeb 1.1.16 Python package to evaluate the atomic datasets available for the spectral modeling of [Fe II] and [Fe III], which list level energies, A-values, and effective collision strengths. Most datasets are reconstructed from the sources, and new ones are incorporated to be compared with observed and measured benchmarks. For [Fe III], we arrive at conclusive results that allow us to select the default datasets, while for [Fe II], the conspicuous temperature dep...

Photoabsorption by and fluorescence of the K{\alpha} transitions in highly charged iron ions are essential mechanisms for X-ray radiation transfer in astrophysical environments. We study photoabsorption due to the main K{\alpha} transitions in highly charged iron ions from heliumlike to fluorinelike (Fe 24+...17+) using monochromatic X-rays around 6.6 keV at the PETRA III synchrotron photon source. Natural linewidths were determined with hitherto unattained accuracy. The obse...

We investigate the emissivity properties of the main near-IR transitions of the Fe+ ion in the conditions prevailing in the inner regions of jets from young stars, based on a simplified 16-level atom model. We present new diagnostic diagrams involving prominent near-IR line ratios that allow us to constrain the electronic density, temperature, and Fe gas phase abundance ratio, independently of the heating process. Comparison with recent near-IR observations of a sample of HH ...

We have calculated FeII emission line strengths for Active Galactic Nuclei Broad-Line Regions using precise radiative transfer and Iron Project atomic data. We improve the treatment of all previously considered excitation mechanisms for the FeII emission, continuum fluorescence, collisional excitation, fluorescence by self-overlap among the iron lines, and fluorescent excitation by Lyman-alpha. We demonstrate that Lyman-alpha fluorescence is of fundamental importance in deter...

The spectra from Fe-peak elements may be used to determine the temperature and density of various astrophysical objects. Determination of these quantities is underpinned by the accuracy and the comprehensiveness of the underlying atomic structure and collisional calculations. In the following paper, we shall focus specifically on Ni IV lines associated with transitions amongst several low-lying levels. We shall employ modified versions of the parallel Dirac R-matrix codes, co...

NLTE line formation calculations of FeI in the solar atmosphere are extended to include weak optical lines. Previously established atomic models are used to discriminate between different ways of treating collisional interaction processes. To derive a common solar FeI abundance from both strong and weak lines, fine-tuning of the microturbulence velocity parameter and the van-der- Waals damping constants is required. The solar FeI abundances based on all available f-values are...

We present deep spectroscopy of three Galactic planetary nebulae (PNe) with large abundance discrepancy factors (ADFs): NGC6153, M1-42 and Hf2-2. The spectra were obtained with VLT/UVES and cover the whole optical range (3040-11,000 A) with a spectral resolution of ~20,000. For all three PNe, several hundred emission lines were detected and identified, with more than 70 per cent of them as permitted lines. Most of these permitted lines are excited by recombination. Numerous w...

As one of the most important elements in astronomy, iron abundance determinations need to be as accurate as possible. We investigate the accuracy of spectroscopic iron abundance analyses using archetypal metal-poor stars. We perform detailed 3D non-LTE radiative transfer calculations based on 3D hydrodynamic Stagger model atmospheres, and employ a new model atom that includes new quantum-mechanical neutral hydrogen collisional rate coefficients. With the exception of the red ...