847 research outputs found
Atomic Data for Permitted Resonance Lines of Atoms and Ions from H to Si, and S, Ar, Ca and Fe
We list vacuum wavelengths, energy levels, statistical weights, transition
probabilities and oscillator strengths for permitted resonance spectral lines
of all ions of 18 astrophysically important elements (H through Si, S, Ar, Ca,
Fe). Using a compilation of experimental energy levels, we derived accurate
wavelengths for 5599 lines of 1828 ground-term multiplets which have gf-values
calculated in the Opacity Project. We recalculated the Opacity Project
multiplet gf-values to oscillator strengths and transition probabilities of
individual lines. For completeness, we added 372 resonance lines of NeI, ArI,
FeI and FeII ions which are not covered by the Opacity Project.
Intercombination and forbidden lines are not included in the present
compilation.Comment: 6 pages of text, latex, 1 figure, 4 tables; tables in ASCII format
available at ftp://asta.pa.uky.edu/dima/lines/ or at
http://www.pa.uky.edu/~verner/atom.html Accepted by Atomic Data Nucl. Data
Table
Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization Cross Sections of Atoms and Ions
We present a complete set of analytic fits to the non-relativistic
photoionization cross sections for the ground states of atoms and ions of
elements from H through Si, and S, Ar, Ca, and Fe. Near the ionization
thresholds, the fits are based on the Opacity Project theoretical cross
sections interpolated and smoothed over resonances. At higher energies, the
fits reproduce calculated Hartree-Dirac-Slater photoionization cross sections.Comment: 24 pages including Postscript figures and tables, uses aaspp4.sty,
accepted for publication in Astrophysical Journal. Misprint in Eq.(1) is
correcte
Continuum Pumping of [Fe II] in the Orion Nebula
This paper presents detailed comparisons between numerical simulations of Fe II emission spectra and recent high-resolution and signal-to-noise spectra of the Orion Nebula. We have identified 40 [Fe II] lines in the spectrum, allowing extensive comparisons between theory and observations. The identifications are based on predictions of a realistic model of the Fe II atom, which includes the lowest 371 levels (all levels up to 11.6 eV). We investigate the dependence of the spectrum on electron density and on pumping by the stellar continuum. Orion is important because it provides a relatively simple environment in which to test complex simulations. We have identified the pumping routes that are responsible for the observed emission. Our theoretical model of Fe II emission is in good agreement with the observational data
A New Window into Gravitationally Produced Scalar Dark Matter
Conventional scenarios of purely gravitationally produced dark matter with
masses below the Hubble parameter at the end of inflation are in tension with
Cosmic Microwave Background (CMB) constraints on the isocurvature power
spectrum. We explore a more general scenario with a non-minimal coupling
between the scalar dark matter field and gravity, which allows for
significantly lighter scalar dark matter masses compared to minimal coupling
predictions. By imposing relic abundance, isocurvature, Lyman-, and Big
Bang Nucleosynthesis (BBN) constraints, we show the viable parameter space for
these models. Our findings demonstrate that the presence of a non-minimal
coupling expands the parameter space, yielding a dark matter mass lower bound
of .Comment: 6 pages, 3 figures (Supplementary Material: 14 pages, 6 figures
Scattering by Interstellar Dust Grains. II. X-Rays
Scattering and absorption of X-rays by interstellar dust is calculated for a
model consisting of carbonaceous grains and amorphous silicate grains. The
calculations employ realistic dielectric functions with structure near X-ray
absorption edges, with resulting features in absorption, scattering, and
extinction.
Differential scattering cross sections are calculated for energies between
0.3 and 10 keV. The median scattering angle is given as a function of energy,
and simple but accurate approximations are found for the X-ray scattering
properties of the dust mixture, as well as for the angular distribution of the
scattered X-ray halo for dust with simple spatial distributions. Observational
estimates of the X-ray scattering optical depth are compared to model
predictions. Observations of X-ray halos to test interstellar dust grain models
are best carried out using extragalactic point sources.Comment: ApJ, accepted. 27 pages, 12 figures. Much of this material was
previously presented in astro-ph/0304060v1,v2,v3 but has been separated into
the present article following recommendation by the refere
- âŠ