We investigate the physical processes occurring in the multiphase gas of a damped Lyα absorber (DLA). We base our analysis on a high-quality Keck High-Resolution Echelle Spectrometer (HIRES) spectrum of the QSO J1211+0422 in which a DLA is detected at z ! 2.377. There is little contamination of the high-ion (O VI, N V, C IV, Si IV) absorption, allowing us to explore the properties of the highly...

We present Gemini-North GMOS-IFU observations of the central starburst clumps and inner wind of M82, together with WIYN DensePak IFU observations of the inner 2× 0.9 kpc of the disk. These cover the emission lines of Hα, [N ii], [S ii], and [S iii] at a spectral resolution of 45–80 km s. The high signal-to-noise of the data is sufficient to accurately decompose the emission line profiles into m...

Aims. We have examined a stream-source model for the production of the cometary tails observed in the Helix Nebula NGC 7293 in which a transonic or moderately supersonic stream of ionized gas overruns a source of ionized gas. We have compared the velocity structures calculated with the available observational data. We have also investigated the suggestion that faint striations visible in the ne...

We present high-resolution spectra (R ∼ 3 km s −1) of the interstellar Na  and Ca  interstellar absorption lines observed towards 3 early-type stars with distances of 360 to 1380pc along the line-of-sight towards the 800pc distant Shajn 147 (S147) Supernova Remnant (SNR). These data are supplemented with far-UV (912-1180Å) aborption spectra of HD 36 665 and HD 37 318 recorded with the NASA F...

We present results from new calculations of the X-ray reflection spectrum from ionized accretion discs. These computations improve on our previous models by including the condition of hydrostatic balance in the vertical direction, following the work of Nayakshin, Kazanas & Kallman. We find that an ionized Fe Kα line is prominent in the reflection spectra for a wide variety of physical condition...

We have searched for evidence of soft X-ray absorption by hot metals in the vicinity of the Galaxy in the spectra of a small sample of fifteen type I AGN observed with the high resolution X-ray gratings on board Chandra. This is an extension of our previous survey of hot O vii and O viii absorbing gas in the vicinity of the Galaxy. The strongest absorption signatures within a few hundred km s o...

We describe a new method for accurately determining total gas-phase abundances for the Galactic halo interstellar medium with minimal ionization uncertainties. For sight lines toward globular clusters containing both ultraviolet-bright stars and radio pulsars, it is possible to measure column densities of H I and several ionization states of selected metals using ultraviolet absorption line mea...

The nonreciprocal propagation of electromagnetic waves in ionized gaseous media is discussed, and experimental observations are reported in this paper. The classical Faraday experiment in the optics of anisotropic media has suggested an analogous phenomenon at microwave frequencies. The anisotropic behavior of the free electron gas which is immersed in a magnetic field and subjected to an incid...

This article reviews observations and models of the diffuse ionized gas that permeates the disk and halo of our Galaxy and others. It was inspired by a series of invited talks presented during an afternoon scientific session of the 65th birthday celebration for Professor Carl Heiles held at Arecibo Observatory in August 2004. This review is in recognition of Carl’s long standing interest in and...

We present results from new calculations of the X-ray reflection spectrum from ionized accretion discs. These computations improve on our previous models by including the condition of hydrostatic balance in the vertical direction, following the work of Nayakshin, Kazanas & Kallman. We find that an ionized Fe Kα line is prominent in the reflection spectra for a wide variety of physical condition...