X-ray emission from the local supercluster: Possible evidence for hot, diffuse cas

The HEAO 1 A2 full sky, 2-10 keV X-ray map was searched for emission correl ated with the plane of the Local Supercluster of galaxies. After removing s trong point and moderately extended sources (e.g., the core of the Virgo cl uster), there remained a statistically significant component of "diffuse" X -rays in the plane of the supercluster. Fitting this diffuse component with a simple "pillbox" model of the local supercluster implies a volume X-ray emissivity of epsilon(x) - 3.0 +/- 0.3 x 10(39)(R-SC/20 Mpc)(-1) ergs s(-1) Mpc(-3), where R-SC is the radius of the supercluster and the error is pho ton counting noise only. If one considers fluctuations in the X-ray backgro und as an additional component of noise, then the detection is reduced cons iderably to 2.3 sigma. However, the significance level implied by this valu e (i.e., 99%) is consistent with the distribution of fits to the model obta ined by rotating the original data. If the source of the X-ray emission is bremsstrahlung from a uniformly distributed plasma with temperature T-e, th en the implied electron number density is N-e = 2.5 x 10(-6) (R-SC/20 Mpc)( -1/2)(kT(e)/10 keV)(-1/4) cm(-3). This value is about an order of magnitude larger than the average baryon number density implied by nucleosynthesis a nd is consistent with a collapse factor of 10. A search for similar structu re in the COBE 53 GHz microwave background map yielded a marginal detection with an amplitude of similar to-17+/-5 mu K (statistical error only), whic h is consistent with the Sunyaev-Zeldovich (SZ) effect expected from 10 keV gas. This latter value is comparable to the amplitude of intrinsic large-s cale fluctuations in the microwave background and should be considered to b e a 1 a result at best.