AGN X-Ray Irradiation of CO Gas in NGC 2110 Revealed by Chandra and ALMA
2020; IOP Publishing; Volume: 895; Issue: 2 Linguagem: Inglês
10.3847/1538-4357/ab8b62
ISSN1538-4357
AutoresT. Kawamuro, Takuma Izumi, Kyoko Onishi, Masatoshi Imanishi, Dieu D. Nguyen, Shunsuke Baba,
Tópico(s)Galaxies: Formation, Evolution, Phenomena
ResumoWe report spatial distributions of the Fe-K$\alpha$ 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 $\approx$ 0.5 arcsec. A $Chandra$ 6.2--6.5 keV-to-3.0--6.0 keV image suggests that the Fe-K$\alpha$ emission extends preferentially in a northwest-to-southeast direction out to $\sim$ 3 arcsec, or 500 pc, on each side. Spatially-resolved spectral analyses support this by finding significant Fe-K$\alpha$ emission lines only in northwest and southeast regions. Moreover, their equivalent widths are found $\sim$ 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 H$_2$. 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.
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