The Origin of the Soft X-Ray Excess in the Seyfert 2 Galaxy NGC 2110

We present and discuss an X-ray image and a medium-resolution X-ray spectrum of the Seyfert 2 galaxy NGC 2110 obtained with the high- resolution imager (HRI) on ROSAT (0.1-2.4 keV) and Goddard's Broad Band X-Ray Telescope (BBXRT; 0.3-11 keV), respectively. Spatially resolved soft X-ray emission, which peaks 4" to the north of the nucleus and near the position of the highest excitation optical emission line gas, is seen in the HRI observation. The extent has a flux ~3 X 10^-13^ ergs cm^-2^ s^-1^ and accounts for 11% +/- 3% of the total 0.1-2.4 keV flux. To model the BBXRT spectrum, a soft excess component is required which has a flux of ~3.5 x 10^-13^ ergs cm^-2^ s^-1^ and accounts for ~14% +/- 6% of the total 0.1-2.4 keV flux. In addition, BBXRT confirms the presence of an ~175 eV equivalent width Fe Kα fluorescence line in NGC 2110. Because of the good agreement between their fluxes, we propose that the soft excess arises from the spatially resolved X-ray emission. This is contrary to previous suggestions that the spectral soft excess in NGC 2110 is due to leakage of the X-ray continuum through a patchy absorber. The temperature of the gas responsible for the soft excess is too high to be accounted for by local shock heating. In order to explain the soft excess and extent as either scattered continuum X-rays or fluorescence from gas photoionized by the nuclear source, the hard X-rays must be emitted anisotropically. However, the soft excess and extent can be well modeled as thermal emission from a hot, outflowing wind, which may also be responsible for confining at least some portion of the optical narrow line-emitting clouds.