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Structure Within the Local Bubble: Properties of Individual Clouds

Published online by Cambridge University Press:  12 April 2016

J.E. Beckman ,
J. Trapero ,
J.R. Álamo ,
R. Génova  and
I. Lundstrom
J.E. Beckman
Affiliation:
Instituto de Astrofísica de Canarias (IAC), La Laguna, Tenerife, Spain
J. Trapero
Affiliation:
Instituto de Astrofísica de Canarias (IAC), La Laguna, Tenerife, Spain LAEFF, Villafranca del Castillo, Madrid, Spain Instituto de Astrofísica de Andalucía, Granada, Spain
J.R. Álamo
Affiliation:
Instituto de Astrofísica de Canarias (IAC), La Laguna, Tenerife, Spain
R. Génova
Affiliation:
Instituto de Astrofísica de Canarias (IAC), La Laguna, Tenerife, Spain
I. Lundstrom
Affiliation:
Lund Astronomical Observatory, Lund, Sweden

Extract

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Starting from the casual observation that neighbouring lines of sight to stars at similar distances in the LISM show abruptly varying column densities, we developed a technique for measuring properties of single clouds. Fig.l shows an idealized version of this. The steps (Trapero et al. 1992, 1995) are:

  1. – Correct for extinction the distances to local stars used, via B-V (where available), or our own measured Nal or KI absorptions.

  2. – Measure diametral column density towards A from Nal or KI equivalent width and convert to hydrogen: N(H) [cm−2].

  3. – Measure cloud diameter, between E and E’.

  4. – Estimate the number density, n(H) = N(H)/d [cm−3].

  5. – Use a canonical thermal pressure, nT = 3500 K cmThis at least gives the decision cool (<100K) or warm (>5000K).

  6. – Estimate the cloud mass by integrating n(H) over the estimated volume.

Following up, cool cores within warm clouds, or warm envelopes around cool clouds can be identified using distance and velocity as tags. We have found empirical rules of thumb to guide us:

  1. – The KI resonance at 7699Å is ideal for finding cool clouds; it is too weak to show up in warm clouds.

  2. – NaI D doublet lines weaker than 5mÅ typify warm clouds. There are too many of these, by a factor 50, to come from cool cloud edges. This is confirmed by the “low velocity Routly-Spitzer effect” (see below).

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. 191 - 194
Copyright
Copyright © Springer-Verlag 1998

References

Lundstrom, L., Ardeberg, A., Maurice, E., Lindgren, H. (1991): A&A 91, 199 Google Scholar
Routly, P.M., Spitzer, L. Jr.(1952): ApJ 115, 225 Google Scholar
Serra-Ricart, M., Trapero, J., Beckman, J.E., Davies, R.D., Watson, R.A. (1995): AJ 109, 312 Google Scholar
Trapero, J., Beckman, J.E., Génova, R., McKeith, C.D. (1992): ApJ 394, 552 Google Scholar
Trapero, J., Beckman, J.E., Serra-Ricart, M., Davies, R.D., Watson, R.A., García López, R.J. (1995): ApJ 445, 231 Google Scholar
Trapero, J. Sempere, M.J., Beckman, J.E., Hobbs, L.M. (1996): ApJ 457, 731 Google Scholar