NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
NE VIII lambda 774 and time variable associated absorption in the QSO UM 675We discuss measurements of Ne VIII lambda 774 absorption and the time variability of other lines in the z(sub a) approximately equal z(sub e) absorption system of the z(sub e) = 2.15 QSO UM 675 (0150-203). The C IV lambda 1549 and N V 1240 doublets at z(sub a) = 2.1340 (shifted approximately 1500 km/s from z(sub e) strengthened by a factor of approximately 3 between observations by Sargent, Boksenberg and Steidel (1981 November) and our earliest measurements (1990 November and December). We have no information on changes in other z(sub a) approximately equal z(sub e) absorption lines. Continued monitoring since 1990 November shows no clear changes in any of the absorptions between approximately 1100 and 1640 A rest. The short timescale of the variability (less than or approximately equal to 2.9 yr rest) strongly suggests that the clouds are dense, compact, close to the QSO, and photoionized by the QSO continuum. If the line variability is caused by changes in the ionization, the timescale requires densities greater than approximately 4000/cu cm. Photoionization calculations place the absorbing clouds within approximately 200 pc of the continuum source. The full range of line ionizations (from Ne VIII lambda 774 to C III lambda 977) in optically thin gas (no Lyman limit) implies that the absorbing regions span a factor of more than approximately 10 in distance or approximately 100 in density. Across these regions, the total hydrogen (H I + H II) column ranges from a few times 10(exp 18)/sq cm in the low-ionization gas to approximately 10(exp 20)/sq cm where the Ne VIII doublet forms. The metallicity is roughly solar or higher, with nitrogen possibly more enhanced by factors of a few. The clouds might contribute significant line emission if they nearly envelop the QSO. The presence of highly ionized Ne VIII lambda 774 absorption near the QSO supports recent studies that link z(sub a) approximately equal to z(sub e) systems with X-ray 'wamr absorbers. We show that the Ne VIII absorbing gas would itself produce measurable warm absorption -- characterized by bound-free O VII or O VIII edegs near 0.8 keV -- if the column densities were N(sub H) greater than or approximately equal to 10(exp 21)/sq cm (for solar abundances).
Document ID
19950054611
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Hamann, Fred
(University of California at San Diego, La Jolla, CA United States)
Barlow, Thomas A.
(University of California at San Diego, La Jolla, CA United States)
Beaver, E. A.
(University of California at San Diego, La Jolla, CA United States)
Burbidge, E. M.
(University of California at San Diego, La Jolla, CA United States)
Cohen, Ross D.
(University of California at San Diego, La Jolla, CA United States)
Junkkarinen, Vesa
(University of California at San Diego, La Jolla, CA United States)
Lyons, R.
(University of California at San Diego, La Jolla, CA United States)
Date Acquired
August 16, 2013
Publication Date
April 20, 1995
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 443
Issue: 2
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A86210
Funding Number(s)
CONTRACT_GRANT: NAG5-1630
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available