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High-Resolution Optical Observations of Diffuse Clouds

Published online by Cambridge University Press:  12 April 2016

Daniel Welty
Daniel Welty*
Affiliation:
University of Chicago, Dept. of Astronomy & Astrophysics, 5640 S. Ellis Ave., Chicago, IL 60637, USA

Abstract

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We describe results from high-resolution (Δv = 0.3-1.5 km s−1) observations of absorption lines due to interstellar Na I, Ca II, K I, Ca I, and Ti II. At those resolutions, we can identify and characterize many (but not all) of the individual clouds along a given line of sight; complex spatial and/or velocity structure appears to be the norm. Both the spectra and the statistics of individual cloud properties derived from fits to the observed line profiles suggest that: 1) the five species are not entirely coextensive in the neutral ISM; 2) the typical separation between adjacent components (in Na I and Ca II) is ~1.2 km s−1; 3) the median line widths (FWHM) for components in Na I, K I, and Ca I are ≾ 1.2 km s−1; 4) larger line widths for Ca II, even for “corresponding” components at similar velocities, suggest that Ca II is more widely distributed; 5) line widths for clouds in the Galactic halo and in the local ISM (within 100 pc) are generally somewhat larger than for clouds in the general Galactic disk; and 6) components with very different properties (line width, relative abundances, overall column densities) are often separated by only several km s−1. Observations of multiple systems and lines of sight in restricted regions reveal complex spatial structure and velocity coincidences even within 100 pc. These high-resolution optical spectra can be used to model lower resolution UV spectra of many other neutral and singly ionized species, enabling abundances and physical properties to be derived for individual interstellar clouds.

Type
Part IV Clouds, Ionized Gas, and Particles in the Local ISM
Information
International Astronomical Union Colloquium , Volume 166: The Local Bubble and Beyond , 1997 , pp. 149 - 160
Copyright
Copyright © Springer-Verlag 1998

References

Barlow, M.J., Crawford, I.A., Diego, F., Dryburgh, M., Fish, A.C., Howarth, I.A., Spyromilio, J., & Walker, D.D. (1995): MNRAS 272, 333 CrossRefGoogle Scholar
Blades, J.C., Sahu, M.S., He, L., Crawford, I.A., Barlow, M.J., & Diego, F. (1997): ApJ 478, 648 Google Scholar
Blades, J.C., Wynne-Jones, I., & Wayte, R.C. (1980): MNRAS 193, 849 Google Scholar
Crane, P., Lambert, D.L., & Sheffer, Y. (1995): ApJS 99, 107 CrossRefGoogle Scholar
Crawford, I.A. (1995): MNRAS 277, 458 Google Scholar
Crawford, I.A., Craig, N., & Welsh, B.Y. (1997): A&A 317, 889 Google Scholar
Crawford, I.A. & Dunkin, S.K. (1995): MNRAS 273, 219 Google Scholar
Crinklaw, G., Federman, S.R., & Joseph, C.L. (1994): ApJ 424, 748 CrossRefGoogle Scholar
Diego, F. et al. (1995): MNRAS 272, 323 Google Scholar
Fitzpatrick, E.L. & Spitzer, L. (1997): ApJ 475, 623 CrossRefGoogle Scholar
Frail, D.A., Weisberg, J.M., Cordes, J.M., & Mathers, C. (1994): ApJ 436, 144 Google Scholar
Frisch, R.C. & Welty, D.E. (1997): in preparationGoogle Scholar
Heiles, C. (1997): ApJ 481, 193 CrossRefGoogle Scholar
Hobbs, L.M. (1969): ApJ 157, 135 Google Scholar
Hobbs, L.M. (1984): ApJS 56, 315 Google Scholar
Jenkins, E.B. (1997): these proceedingsGoogle Scholar
Jenkins, E.B. &: Shaya, E.J. (1979): ApJ 231, 55 Google Scholar
Marschall, L.A. & Hobbs, L.M. (1972): ApJ 173, 43 Google Scholar
Meyer, D.M. (1994): in The First Symposium on the Infrared Cirrus and Diffuse Interstellar Clouds, ed. Cutri, R.M. & Latter, W.B. (San Francisco: PASP), 3 Google Scholar
Meyer, D.M. & Blades, J.C. (1996): ApJ 464, L179 Google Scholar
Pettini, M. (1988): Proc. Astron. Soc. Aust. 7, 527 Google Scholar
Piskunov, N., Wood, B.E., Linsky, J.L., Dempsey, R.C., & Ayres, T.R. (1997):ApJ 474, 315 CrossRefGoogle Scholar
Savage, B.D., Cardelli, J.A., & Sofia, U.J. (1992): ApJ 430, 650 Google Scholar
Savage, B.D. & Sembach, K.R. (1996): ARA&A 34, 279 Google Scholar
Sembach, K.R., Danks, A.C., & Lambert, D.L. (1996): ApJ 460, L61 Google Scholar
Stokes, G.M. (1978): ApJS 36, 115 Google Scholar
Tuli, R.G. (1972): in Proc. ESO/CERN Conference on Auxiliary Instrumentation for Large Telescopes (Geneva: ESO), 259 Google Scholar
Watson, J.K. & Meyer, D.M. (1996): ApJ 473, L127 Google Scholar
Welsh, B.Y., Crawford, I.A., & Lallement, R. (1997): these proceedingsGoogle Scholar
Welty, D.E., Hobbs, L.M., & Kulkami, V.P. (1994): ApJ 436, 152 Google Scholar
Welty, D.E., Hobbs, L.M., Lauroesch, J.T., Morton, D.C., Spitzer, L., & York, D.G. (1997a): in preparationGoogle Scholar
Welty, D.E., Hobbs, L.M., & Morton, D.C. (1997b): in preparationGoogle Scholar
Welty, D.E., Lauroesch, J.T., & Fowler, J.R. (1997c): in preparationGoogle Scholar
Welty, D.E., Morton, D.C., & Hobbs, L.M. (1996): ApJS 106, 533 CrossRefGoogle Scholar