If the large-scale galaxy distribution is filamentary, as suggested by some observations and recent hydrody-namical 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 ≡ L_xa_p~3/L_g~2T_x~(1/2) 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_p is the radius of the group projected onto the sky, L_x is the bolometric X-ray luminosity, L_g is the group blue luminosity, and T_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.
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