paper

AGN X-ray irradiation of CO gas in NGC 2110 revealed by and ALMA

arXiv:2004.09394 · doi:10.3847/1538-4357/ab8b62

Abstract

We report spatial distributions of the Fe-K line at 6.4 keV and the CO( = 2--1) line at 230.538 GHz in NGC 2110, which are respectively revealed by and ALMA at 0.5 arcsec. A 6.2--6.5 keV-to-3.0--6.0 keV image suggests that the Fe-K 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-K 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( = 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 H. Another possibility also remains that CO molecules follow a super-thermal distribution, resulting in brighter emission in higher- 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.

15 pages, 11 figures, 3 tables. Accepted for publication in ApJ

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