Tracking X-ray outflows with optical/infrared footprint lines
Abstract
We use cloudy photoionization models to predict the flux profiles for optical/infrared (IR) emission lines that trace the footprint of X-ray gas, such as [Fe X] 6375 Å and [Si X] 1.43 $\mu\mathrm{m}$. These are subset of coronal lines, from ions with ionization potential greater than or equal to that of O VII, i.e. 138 eV. The footprint lines are formed in gas over the same range in ionization state as the H- and He-like of O and Ne ions, which are also the source of X-ray emission lines. The footprint lines can be detected with optical and IR telescopes, such as the Hubble Space Telescope/STIS and James Webb Space Telescope/NIRSpec, and can potentially be used to measure the kinematics of the extended X-ray emission gas. As a test case, we use the footprints to quantify the properties of the X-ray outflow in the type 1 Seyfert galaxy NGC 4151. To confirm the accuracy of our method, we compare our model predictions to the measured flux from archival STIS spectra and previous ground-based studies, and the results are in good agreement. We also use our X-ray footprint method to predict the mass profile for the X-ray emission-line gas in NGC 4151 and derive a total spatially integrated X-ray mass of $7.8(\pm 2.1) \times 10^{5}\, {\rm M}_{\odot }$, in comparison to $5.4(\pm 1.1) \times 10^{5}\, {\rm M}_{\odot }$ measured from a Chandra X-ray analysis. Our results indicate that high-ionization footprint emission lines in the optical and near-IR can be used to accurately trace the kinematics and physical conditions of active galactic nucleus-ionized, X-ray emission-line gas.
- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2022
- DOI:
- 10.1093/mnras/stac173
- arXiv:
- arXiv:2110.11436
- Bibcode:
- 2022MNRAS.511.1420T
- Keywords:
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- galaxies: active;
- galaxies: kinematics and dynamics;
- galaxies: Seyfert;
- X-rays: galaxies;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- doi:10.1093/mnras/stac173