Systematic study of X-ray cavities in the brightest galaxy in the Draco constellation NGC 6338




We present results based on the systematic analysis of currently available Chandra archive data on the brightest galaxy in the Draco constellation, NGC 6338, in order to investigate the properties of the X-ray cavities. In the central ∼6 kpc, at least two, possibly three, X-ray cavities are evident. All these cavities are roughly of ellipsoidal shape and show a decrement in surface brightness of several tens of per cent. In addition to these cavities, a set of X-ray bright filaments are also noticed which are spatially coincident with the Hα filaments over an extent of 15 kpc. The Hα emission-line filaments are perpendicular to the X-ray cavities. Spectroscopic analysis of the hot gas in the filaments and cavities reveals that the X-ray filaments are cooler than the gas contained in the cavities. The emission-line ratios and the extended, asymmetric nature of the Hα emission-line filaments seen in this system require a harder ionizing source than that produced by star formation and/or young, massive stars. Radio emission maps derived from the analysis of 1.4-GHz Very Large Array Faint Images of the Radio Sky at Twenty-Centimeters survey data failed to show any association of these X-ray cavities with radio jets; however, the cavities are filled by radio emission. The total power of the cavities is 17 × 1042 erg s−1 and the ratio of radio luminosity to cavity power is ∼10−4, implying that most of the jet power is mechanical.