| 1. |
- Kawamuro, Taiki, et al.
(författare)
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AGN X-Ray Irradiation of CO Gas in NGC 2110 Revealed by Chandra and ALMA
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 895:2
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Tidskriftsartikel (refereegranskat)abstract
- We 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 Atacama Large Millimeter/submillimeter Array (ALMA) at 05. 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 3 '', or similar to 500 pc, on each side. Spatially resolved spectral analyses support this by finding significant Fe-K alpha emission lines only in the northwest and southeast regions. Moreover, their equivalent widths are found to be similar to 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 superthermal distribution, resulting in brighter emission in higher-J lines. Further follow-up observations are encouraged to draw a conclusion on what predominantly changes the interstellar matter properties and whether the X-ray irradiation eventually affects the surrounding star formation as active galactic nucleus (AGN) feedback.
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| 2. |
- Kawamuro, Taiki, et al.
(författare)
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Hard X-Ray Irradiation Potentially Drives Negative AGN Feedback by Altering Molecular Gas Properties
- 2021
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Ingår i: Astrophysical Journal, Supplement Series. - : American Astronomical Society. - 1538-4365 .- 0067-0049. ; 257:2
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the role of active galactic nucleus (AGN) X-ray irradiation on the interstellar medium (ISM), we systematically analyzed Chandra and Atacama Large Millimeter/submillimeter Array CO (J = 2-1) data for 26 hard X-ray (>10 keV) selected AGNs at redshifts below 0.05. While Chandra unveils the distribution of X-ray-irradiated gas via Fe-K alpha emission, the CO (J = 2-1) observations reveal that of cold molecular gas. At high resolutions less than or similar to 1 '', we derive Fe-K alpha and CO (J = 2-1) maps for the nuclear 2 '' region and for the external annular region of 2 ''-4 '', where 2 '' is similar to 100-600 pc for most of our AGNs. First, focusing on the external regions, we find the Fe-K alpha emission for six AGNs above 2 sigma. Their large equivalent widths (greater than or similar to 1 keV) suggest a fluorescent process as their origin. Moreover, by comparing the 6-7 keV/3-6 keV ratio, as a proxy of Fe-K alpha, and CO (J = 2-1) images for three AGNs with the highest significant Fe-K alpha detections, we find a possible spatial separation. These suggest the presence of X-ray-irradiated ISM and the change in the ISM properties. Next, examining the nuclear regions, we find that (1) the 20-50 keV luminosity increases with the CO (J = 2-1) luminosity; (2) the ratio of CO (J = 2-1)/HCN (J = 1-0) luminosities increases with 20-50 keV luminosity, suggesting a decrease in the dense gas fraction with X-ray luminosity; and (3) the Fe-K alpha-to-X-ray continuum luminosity ratio decreases with the molecular gas mass. This may be explained by a negative AGN feedback scenario: the mass accretion rate increases with gas mass, and simultaneously, the AGN evaporates a portion of the gas, which possibly affects star formation.
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