Spatially Resolved X‐Ray Spectra of NGC 4258

We report a spatially resolved, X-ray spectral analysis of NGC 4258 usingarchival {\it Chandra} and {\it XMM-Newton} observations. The {\it XMM-Newton}spectra of the nuclear region are well described by two power-law components, asoft (0.57 keV) thermal component, and an Fe K$\alpha$ line with EW = 40 $\pm$33 eV. The properties of the second, weaker power-law component are similar tothose of an off-nuclear source $2.5\arcsec$ SW of the nucleus. The spectrum ofthe extended emission of the entire galaxy is well described by two thermalcomponents (MEKAL) models with temperatures $\simeq 0.60$ and 0.22 keV. The{\it Chandra} and {\it XMM-Newton} spectra along the anomalous arms show thatthe absorbing column density to the SE anomalous arm is consistent withabsorption by gas in our Galaxy, while the absorbing column to the NW anomalousarm is higher, indicating that the NW arm is partially on the far side of thegalactic disk. The combined {\it Chandra} data clearly detect the X-rayemission from the hot spots at the end of the approximately N-S radio jets. Byassuming the hot spots represent shocked thermal gas at the ends of the jets,we estimate shock powers of $\simeq 3 \times 10^{39} f^{-1/2}$ \ergps ($f $ isthe filling factor), similar to the radiative power in the inner anomalousarms, consistent with the notion that the jets could be responsible for heatingthe gas in the anomalous arms.