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Radio and optical observations of high- and intermediate-velocity gas in the nearby interstellar medium
Observations at the 21-cm wavelength obtained with the Lovell Telescopeare used in a report on the detection of a weak H I emission feature ata velocity + 100 km/s LSR and of column density log N (H I) = 18.5 + or- 0.2 toward the star 4 Lac. The feature corresponds in velocity with ahigh-velocity gas component observed in several UV resonance lines inIUE spectra of this star. The component gas temperature, derived fromradio, optical and UV spectra, lies in the range 5000 to 9000 K and theline-of-sight column thickness is estimated to be less than 10 pc. Therelationship between this observed feature and the widely distributedHigh-Velocity Clouds (HVCs) is considered briefly.
| Studies of the gas and dust distribution in the local interstellar medium
Previous results on the gas and dust distribution in the localinterstellar medium are discussed, with special attention given to thesearch for possible dust concentrations in regions of the sky containinghigh velocity gas components. High-resolution maps of the 4 Lac regionreveal an emission feature which contains much structure, extends fromthe galactic plane, and is inclined at an angle of about 45 deg to theplane. An IR emission known as galactic cirrus, noted at high galacticlatitudes, is suggested by Low et al. (1984) to be due to the presenceof dust.
| IRAS maps for a region of sky containing nearby high-velocity gas, identified from IUE spectra
Detailed IRAS contour maps in the 60 and 100-micron wavebands arepresented for a small region of sky towards which 'high-velocity gascomponents' (HVC) have been clearly identified in spectra of backgroundstars obtained with the IUE satellite. There is a coincidence indirection on the sky between the strongest regions of absorptionproduced by HVC gas and compact regions of brightest IR emission.However, there is no clear evidence at present for identifying the HVCdirectly with the IR emission due to insufficient spatial informationalong the lines-of-sight examined. A comparison of H I column densitiesobtained from both the 100-micron emission and color excess dataindicates that dust emission, rather than atomic line emission, is thedominant contribution to the IRAS observations in the sightlinesconsidered.
| IUE and optical studies of nearby interstellar gas
Red-shifted high velocity interstellar gas components with velocities upto 100 km/sec were detected in the IUE spectra of stars in the Galacticdirection e = 100 deg, b = 7 deg. These are compared with highresolution optical observations of the NaD interstellar lines, whichallow the distribution of the gas to be mapped more extensively than inearlier surveys. Calculations of the temperature sensitive N(Mg I)/N(NaI) ratio are presented, and used with the UV results to partially derivephysical conditions within several of the high velocity clouds.
| Absolute Emission-Line Intensities in Planetary Nebulae. I.
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| The space distribution of stars in selected Milky Way regions derived from photometric and spectroscopic data. I. A region in Lacerta, Centre A.R. = 22h30m, Dec. = +48deg40' ((1900.0).
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