AGN X-ray irradiation of CO gas in NGC 2110 revealed by Chandra and ALMA
Abstract
We report spatial distributions of the Fe-Kα line at 6.4 keV and the CO(J = 2--1) line at 230.538 GHz in NGC 2110, which are respectively revealed by Chandra and ALMA at ≈ 0.5 arcsec. A Chandra 6.2--6.5 keV-to-3.0--6.0 keV image suggests that the Fe-Kα emission extends preferentially in a northwest-to-southeast direction out to 3 arcsec, or 500 pc, on each side. Spatially-resolved spectral analyses support this by finding significant Fe-Kα emission lines only in northwest and southeast regions. Moreover, their equivalent widths are found 1.5 keV, indicative for the fluorescence by nuclear X-ray irradiation as the physical origin. By contrast, CO(J = 2--1) emission is weak therein. For quantitative discussion, we derive ionization parameters by following an X-ray dominated region (XDR) model. We then find them high enough to interpret the weakness as the result of X-ray dissociation of CO and/or H2. Another possibility also remains that CO molecules follow a super-thermal distribution, resulting in brighter emission in higher-J lines. Further follow-up observations are encouraged to draw a conclusion on what predominantly changes the inter-stellar matter properties, and whether the X-ray irradiation eventually affects the surrounding star formation as an AGN feedback.