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The local distribution of NA I interstellar gas
We present high-resolution absorption measurements (lambda/Delta lambdaapproximately 75,000) of the interstellar Na I D lines at 5890 A toward80 southern hemisphere early-type stars located in the localinterstellar medium (LISM). Combining these results with other sodiummeasurements taken from the literature, we produce galactic maps of thedistribution of neutral sodium column density for a total of 293 starsgenerally lying within approximately 250 pc of the Sun. These mapsreveal the approximate shape of the mid-plane contours of the rarefiedregion of interstellar space termed the Local Bubble. Its shape is seenas highly asymmetric, with a radius ranging from 30 to 300 pc, and withan average radius of 60 pc. Similar plots of the Galactic mid-planedistribution of sources emitting extreme ultraviolet radiation show thatthey also trace out similar contours of the Local Bubble derived from NaI absorption measurements. We conclude that the Local Bubble absorptioninterface can be represented by a hydrogen column density,NuETA = 2 x 1019 cm-2, which explainsboth the local distribution of Na I absorption and the observed galacticdistribution of extreme ultraviolet sources. The derived mid-planecontours of the Bubble generally reproduce the large-scale featurescarved out in the interstellar medium by several nearby galactic shellstructures.
| Optical spectroscopy of the high-latitude cloud LYNDS 1569
The interstellar material toward L1569 is studied in detail usingcombined optical and IR data. The cloud associated with the 9.0 km/scomponent of CO emission is seen to have N(CH) = (3.5 + or - 0.3) x 10to 13th/sq cm and two components of atomic Na I absorption at LSRvelocities of 9/0 and 22 km/s with column densities of N(Na I) = (7.3 +or - 1.3) x 10 to the 12th and (2.0 + or - 0.5) x 10 to the 11th/sq cm,respectively. Observed Ca II absorption in one direction is seen atvelocities of 9.6 and 21.6 km/s, and the 21.6 km/s component has a valueof N(Ca II)/N(Na I) greater than 64. Evidence for cloud heating and foran angular size of 30 arcmin for the L1569 cloud associated with theabsorption toward HD 25154 is discussed. This angular size, combinedwith a distance estimate of 150 pc, is used to derive approximate valuesof d = 1.2 pc and M = 50 solar masses. The CH column density isapproximately double that for dark clouds of comparable extinction inthe Galactic plane.
| Estimation of stellar intrinsic colours, distances and colour excesses based on the Stromgren and H-beta photometry of 804 B, A, and F stars in 10 Selected Areas
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989A&AS...78..105F&db_key=AST
| Four-colour UVBY and H-beta photometry of all A and F stars brighter than MPG of about 11.0 mag in 4 Selected Areas at intermediate galactic latitudes
As a second part of an investigation of the distribution of interstellardust in the solar vicinity, uvby-beta photometry has been obtained for260 stars of spectral types A and F, and brighter than mpg of11.0 mag in four Kapteyn's Selected Areas. The observed areas are: SA95, SA 120, SA 168, and SA 200. They are centered at intermediategalactic latitudes, in the range from b of about -38 deg to -42 deg.From the observed (b-y) versus beta diagrams it can be seen that starsin SA 95 are strongly affected by reddening, while the other areas showvery little absorption.
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