ChandraView of the Dynamically Young Cluster of Galaxies A1367. I. Small‐Scale Structures

The 40 ks \emph{Chandra} ACIS-S observation of A1367 provides new insightsinto small-scale structures and point sources in this dynamically youngcluster. Here we concentrate on small-scale extended structures. A ridge-likestructure around the center (``the ridge'') is significant in the \chandra\image. The ridge, with a projected length of $\sim$ 8 arcmin (or 300h$_{0.5}^{-1}$ kpc), is elongated from northwest (NW) to southeast (SE), as isthe X-ray surface brightness distribution on much larger scales ($\sim$ 2h$_{0.5}^{-1}$ Mpc). The ridge is cooler than its western and southernsurroundings while the differences from its eastern and northern surroundingsare small. We also searched for small-scale structures with sizes $\sim$arcmin. Nine extended features, with sizes from $\sim$ 0.5$'$ to 1.5$'$, weredetected at significance levels above 4 $\sigma$. Five of the nine features arelocated in the ridge and form local crests. The nine extended features can bedivided into two types. Those associated with galaxies (NGC 3860B, NGC 3860 andUGC 6697) are significantly cooler than their surroundings (0.3 - 0.9 keV vs. 3- 4.5 keV). The masses of their host galaxies are sufficient to bind theextended gas. These extended features are probably related to thermal halos orgalactic superwinds of their host galaxies. The existence of these relativelycold halos imply that galaxy coronae can survive in cluster environment (e.g.,Vikhlinin et al. 2001). Features of the second type are not apparentlyassociated with galaxies. Their temperatures may not be significantly differentfrom those of their surroundings. This class of extended features may berelated to the ridge. We consider several possibilities for the ridge and thesecond type of extended features. The merging scenario is preferred.