Optical studies of interstellar material in low density regions of the Galaxy. I - A survey of interstellar NA I and CA II absorption toward 57 distant stars

Details Optical studies of interstellar material in low density regions of the Galaxy. I - A survey of interstellar NA I and CA II absorption toward 57 distant stars Optical studies of interstellar material in low density regions of the Galaxy. I - A survey of interstellar NA I and CA II absorption toward 57 distant stars

Jul 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26as..100..107s&link_type=abstract

Astronomy and Astrophysics Supplement Series (ISSN 0365-0138), vol. 100, no. 1, p. 107-171.

Astronomy and Astrophysics

Astrophysics

93

Absorption Spectra, B Stars, Calcium, Interstellar Matter, Milky Way Galaxy, O Stars, Sodium, Astronomical Photometry, Density Distribution, Galactic Halos, Interstellar Gas, Spectral Line Width

Scientific paper

We present high-resolution spectra of the Na I D and Ca II K lines toward 57 late-O and early-B stars along extended (d greater than 1 kpc) low-density paths through the Milky Way disk and halo. The sight lines preferentially sample diffuse gas in the interstellar medium (ISM) along interarm, Galactic center, and high latitude directions. We measure equivalent widths, apparent column densities, and absorption component structure. The Ca II to Na I ratios presented as a function of velocity for each sight line exhibit variations due to elemental depletion, ionization, and density enhancements. Absorption along high latitude sight lines is kinematically simpler than it is along interarm and Galactic center sight lines. Galactic rotation noticeably broadens the absorption profiles of distant stars located in these latter directions. Along several sight lines, we see Ca II absorption at velocities corresponding to large distances (/z/ about 1 kpc) from the Galactic plane. The effects of differences in the Ca II and Na I scale heights and nonzero velocity dispersions are readily apparent in the data. Brief notes are given for several sight lines with interesting absorption properties.

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