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Title: THE REMARKABLE HIGH PRESSURE OF THE LOCAL LEO COLD CLOUD

Abstract

Using the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope, we have obtained high-resolution ultraviolet spectra of the C I absorption toward two stars behind the Local Leo Cold Cloud (LLCC). At a distance ( Almost-Equal-To 20 pc) that places it well inside the Local Bubble, the LLCC is the nearest example of the coldest known (T Almost-Equal-To 20 K) diffuse interstellar clouds. The STIS measurements of the C I fine-structure excitation toward HD 85259 and HD 83023 indicate that the thermal gas pressure of the LLCC is much greater than that of the warm clouds in the Local Bubble. The mean LLCC pressure measured toward these two stars (60,000 cm{sup -3} K) implies an H I density of Almost-Equal-To 3000 cm{sup -3} and a cloud thickness of Almost-Equal-To 200 AU at the 20 K cloud temperature. Such a thin, cold, dense structure could arise at the collision interface between converging flows of warm gas. However, the measured LLCC pressure is appreciably higher than that expected in the colliding-cloud interpretation given the velocity and column density constraints on warm clouds in the HD 85259 and HD 83023 sightlines. Additional STIS measurements of the Zn II, Ni II,more » and Cr II column densities toward HD 85259 indicate that the LLCC has a modest 'warm cloud' dust depletion pattern consistent with its low dust-to-gas ratio determined from H I 21 cm and 100 {mu}m observations. In support of the inferred sheet-like geometry for the LLCC, a multi-epoch comparison of the Na I absorption toward a high-proper-motion background star reveals a 40% column density variation indicative of LLCC Na I structure on a scale of Almost-Equal-To 50 AU.« less

Authors:
 [1];  [2];  [3];  [4]
  1. Center for Interdisciplinary Exploration and Research in Astrophysics, Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States)
  2. Department of Physics and Astronomy, University of Louisville, Louisville, KY 40292 (United States)
  3. Department of Astronomy, Columbia University, Pupin Physics Laboratories, 550 West 120th Street, New York, NY 10027 (United States)
  4. Department of Astronomy, University of California, Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States)
Publication Date:
OSTI Identifier:
22037025
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 752; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ASTRONOMY; ASTROPHYSICS; ATOMS; COMPARATIVE EVALUATIONS; COSMIC DUST; DENSITY; EXCITATION; FINE STRUCTURE; PROPER MOTION; RESOLUTION; STARS; ULTRAVIOLET SPECTRA

Citation Formats

Meyer, David M., Lauroesch, J. T., Peek, J. E. G., and Heiles, Carl, E-mail: davemeyer@northwestern.edu, E-mail: jtlaur01@louisville.edu, E-mail: goldston@gmail.com, E-mail: heiles@astro.berkeley.edu. THE REMARKABLE HIGH PRESSURE OF THE LOCAL LEO COLD CLOUD. United States: N. p., 2012. Web. doi:10.1088/0004-637X/752/2/119.
Meyer, David M., Lauroesch, J. T., Peek, J. E. G., & Heiles, Carl, E-mail: davemeyer@northwestern.edu, E-mail: jtlaur01@louisville.edu, E-mail: goldston@gmail.com, E-mail: heiles@astro.berkeley.edu. THE REMARKABLE HIGH PRESSURE OF THE LOCAL LEO COLD CLOUD. United States. doi:10.1088/0004-637X/752/2/119.
Meyer, David M., Lauroesch, J. T., Peek, J. E. G., and Heiles, Carl, E-mail: davemeyer@northwestern.edu, E-mail: jtlaur01@louisville.edu, E-mail: goldston@gmail.com, E-mail: heiles@astro.berkeley.edu. Wed . "THE REMARKABLE HIGH PRESSURE OF THE LOCAL LEO COLD CLOUD". United States. doi:10.1088/0004-637X/752/2/119.
@article{osti_22037025,
title = {THE REMARKABLE HIGH PRESSURE OF THE LOCAL LEO COLD CLOUD},
author = {Meyer, David M. and Lauroesch, J. T. and Peek, J. E. G. and Heiles, Carl, E-mail: davemeyer@northwestern.edu, E-mail: jtlaur01@louisville.edu, E-mail: goldston@gmail.com, E-mail: heiles@astro.berkeley.edu},
abstractNote = {Using the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope, we have obtained high-resolution ultraviolet spectra of the C I absorption toward two stars behind the Local Leo Cold Cloud (LLCC). At a distance ( Almost-Equal-To 20 pc) that places it well inside the Local Bubble, the LLCC is the nearest example of the coldest known (T Almost-Equal-To 20 K) diffuse interstellar clouds. The STIS measurements of the C I fine-structure excitation toward HD 85259 and HD 83023 indicate that the thermal gas pressure of the LLCC is much greater than that of the warm clouds in the Local Bubble. The mean LLCC pressure measured toward these two stars (60,000 cm{sup -3} K) implies an H I density of Almost-Equal-To 3000 cm{sup -3} and a cloud thickness of Almost-Equal-To 200 AU at the 20 K cloud temperature. Such a thin, cold, dense structure could arise at the collision interface between converging flows of warm gas. However, the measured LLCC pressure is appreciably higher than that expected in the colliding-cloud interpretation given the velocity and column density constraints on warm clouds in the HD 85259 and HD 83023 sightlines. Additional STIS measurements of the Zn II, Ni II, and Cr II column densities toward HD 85259 indicate that the LLCC has a modest 'warm cloud' dust depletion pattern consistent with its low dust-to-gas ratio determined from H I 21 cm and 100 {mu}m observations. In support of the inferred sheet-like geometry for the LLCC, a multi-epoch comparison of the Na I absorption toward a high-proper-motion background star reveals a 40% column density variation indicative of LLCC Na I structure on a scale of Almost-Equal-To 50 AU.},
doi = {10.1088/0004-637X/752/2/119},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 752,
place = {United States},
year = {2012},
month = {6}
}