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Using X-rays to determine which compact groups are illusoryIf the large-scale galaxy distribution is filamentary, as suggested by some observations and recent hydrodynamical simulations, then lengthwise views of filaments will apparently produce compact groups (CGs) that are in reality stretched out along the line of sight. This possibility has been advocated recently by Hernquist, Katz, & Weinberg (1995). Here we propose a test for this hypothesis using X-ray emission from CGs. The observable quantity Q identical with L(sub x)a(sup 3)(sup p)/(L(sup 2)(sup g))T(sup 1/2)(sub x) should be proportional to the axis ratio of the group, a/c, where a and c are the short and long axes of a prolate distribution, a(sub p) is the radius of the group projected onto the sky, L(sub x) is the bolometric X-ray luminosity, L(sub g) is the group blue luminosity, and T(sub x) is the gas temperature. We find that the distribution of Q is consistent with the notion that many CGs with unusually small values of a/c are frauds, i.e., that the values of Q are anomalously small. Absent other information, it is equally possible that CGs are very gas-poor relative to rich clusters; however, this can be tested using the Sunyaev-Zeldovich effect. If the groups have a close to normal ratio of gas to total mass, but are simply stretched out along the line of sight, a Sunyaev-Zeldovich signal should be detectable.
Document ID
19950054412
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Ostriker, Jeremiah P.
(Princeton University Observatory, Princeton, NJ, United States)
Lubin, Lori M.
(Princeton University Observatory, Princeton, NJ, United States)
Hernquist, Lars
(University of California at Santa Cruz, Santa Cruz, CA United States)
Date Acquired
August 16, 2013
Publication Date
May 10, 1995
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 444
Issue: 2
ISSN: 0004-637X
Subject Category
Astronomy
Accession Number
95A86011
Funding Number(s)
CONTRACT_GRANT: NGT-51295
CONTRACT_GRANT: NSF ASC-93-18185
CONTRACT_GRANT: NSF AST-91-08103
CONTRACT_GRANT: NSF AST-90-18526
CONTRACT_GRANT: NAGW-2422
CONTRACT_GRANT: NAGW-2448
Distribution Limits
Public
Copyright
Other

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