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Probing the interstellar medium with pulsars on AU scalesWe present a new technique, multiepoch observations of 21 cm absorption against high-velocity pulsars, to probe the properties of the cold neutral hydrogen gas (H I) in the interstellar medium (ISM) at AU scales. In three epochs, over a 1.7 yr interval, we find evidence for significant opacity variations toward all of the pulsars in our sample. Small-scale structure in the ISM is detected on a range of scales from 5 AU to 100 AU, over a wide range of distances (50-2600 pc), opacities (tau(sub max) = 0.1 - 2.5) and directions (anticenter, interarm, high latitude, and local ISM). It appears that small-scale structure is a general property of the ISM and is not confined to special lines of sight. A significant fraction (10%-15%) of the cold H I gas is in this form. These opacity variations do not show any strong correlations with such parameters as transverse distance or integrated opacity, and there is no obvious relation between these structures and those seen in the ionized phase of the ISM.
Document ID
19950037124
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Frail, Dale A.
(National Radio Astronomy Observatory, Socorro, NM United States)
Weisberg, Joel M.
(Carleton College, Northfield, MN United States)
Cordes, James M.
(Cornell Univ. Ithaca, NY, United States)
Mathers, Corey
(Carleton College, Northfield, MN United States)
Date Acquired
August 16, 2013
Publication Date
November 20, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 436
Issue: 1
ISSN: 0004-367X
Subject Category
Astrophysics
Accession Number
95A68723
Funding Number(s)
CONTRACT_GRANT: NSF AST-92-22435
CONTRACT_GRANT: NSF AST-92-18075
CONTRACT_GRANT: NSF AST-89-19061
Distribution Limits
Public
Copyright
Other

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