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Scientific paper
Jun 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000phdt.........2c&link_type=abstract
Thesis (PhD). THE JOHNS HOPKINS UNIVERSITY, Source DAI-B 61/10, p. 5369, Jun 2000, 234 pages.
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1
Interstellar Medium, Puppis-Vela, Spectroscopy
Scientific paper
The interstellar medium (ISM) toward Puppis-Vela (l = 245° to 275°, b = -15° to +5°) has been studied using high resolution, R ~ 75,000-90,000, high signal-to-noise, S/N ~ 100, optical Na I and Ca II absorption spectra along several hundred lines of sight. The distance of the Vela supernova remnant was found to be at d ~ 250 pc, a factor of two less than the canonical value. Lines of sight passing through the Vela supernova remnant were seen to have optical spectra that varied over epochs of a few years, including those toward HD 72089, HD 72127, HD 72997, HD 73658, HD 74455, HD 75309, and HD 75821. The variability of the first three lines of sight had been previously documented, but variability in the spectra toward the latter four stars had not been observed. An analysis of the Local ISM (d < 200 pc) toward Puppis-Vela is presented, and using both Na I absorption features and accurate distances to the stars, courtesy of Hipparcos trigonometric parallax data, spatially compact, homogeneous velocity components were mapped. In the Local ISM, the Puppis-Vela region abuts the apparent extension of the Local Bubble (or Cavity) known as the β CMa tunnel, and the compiled Na I lines of sight suggest that within 200 pc, the extent of the tunnel is confined to a region smaller than was previously thought. The technique of identifying and mapping individual velocity components in three dimensions was extended to the Puppis-Vela ISM out to d ~ 1 kpc, and a total of 7 velocity components were identified. Gas with velocities higher than that expected in the ambient ISM combined with higher than normal reddening was detected toward two regions, (l ~ 254°, b ~ -1°) and (l ~ 251°, b ~ -7°), suggesting the presence of previously unidentified structures. Nearby, gas associated with the IRAS Vela Shell was detected in Na I at distances >~ 300 pc. The Na I velocity components from IRAS Vela Shell sight lines were fit with a model of a spherically expanding filled sphere with an average expansion rate of ~12 km s-1, consistent with previous studies which used other ions. In addition to a thorough analysis of the gaseous component of the ISM in Puppis-Vela, a correlation between the gas and dust was sought. Using column densities of Na I and color excesses, E(B - V), as indicators of the respective amounts of gas and dust present along each line of sight, a linear empirical relationship was found: N(Na I) = -1.9 × 1012 + 4.6 × 1013 E(B - V).
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