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XRISM Discovery of Multiple Ionized Fe-K Emission and Absorption Components in Centaurus A

Taishu Kayanoki, Yasushi Fukazawa, Junjie Mao, Jon M. Miller, Luigi Gallo, Tahir Yaqoob, Richard Mushotzky, David Bogensberger, Misaki Mizumoto, Kouichi Hagino, Hirofumi Noda, Yoshihiro Ueda, Makoto Tashiro, Yuya Nakatani, Toshiya Iwata, Misaki Urata

Abstract

We present the first clear detection of ionized Fe-K emission and absorption components in the nearby radio galaxy Centaurus A, revealed by the high-resolution XRISM/Resolve detector. In the 6.5-6.9 keV band, XRISM reveals multiple Fe XXV and Fe XXVI emission components. One is a broad (with a width of sigma = 3000 km/s) and redshifted (+3400 km/s) component, originating at D = 0.02 pc from the central black hole. The other two components are narrow (with a width of sigma = 500 km/s) and exhibit redshifted and blueshifted velocities (+2600 km/s and -1500 km/s), originating from more distant regions (D = 0.1 pc). The photo-ionized model explains the broader component, while the two narrower components can be explained by either photo-ionization or collisional ionization. One interpretation is that the broader component is an outflow at ~10^2 R_S (R_S; Schwarzschild radius) and the narrow component is a shock-heated plasma close to the torus, with a possible connection to the JWST-discovered outflow outside the torus. Two blueshifted absorption lines are detected at ~7.1 keV (~10^4 km/s) and ~10.6 keV (~10^5 km/s). The line significance of the 10.6 keV line is above 98%. The absorption line components might be attributed to the broad emission component. These results demonstrate the high potential of XRISM/Resolve to characterize ionized emission and absorption features in the Fe-K band. Our findings establish a new benchmark in the study of circumnuclear environments in low-luminosity radio galaxies, thereby contributing to a broader understanding of AGN unification.

XRISM Discovery of Multiple Ionized Fe-K Emission and Absorption Components in Centaurus A

Abstract

We present the first clear detection of ionized Fe-K emission and absorption components in the nearby radio galaxy Centaurus A, revealed by the high-resolution XRISM/Resolve detector. In the 6.5-6.9 keV band, XRISM reveals multiple Fe XXV and Fe XXVI emission components. One is a broad (with a width of sigma = 3000 km/s) and redshifted (+3400 km/s) component, originating at D = 0.02 pc from the central black hole. The other two components are narrow (with a width of sigma = 500 km/s) and exhibit redshifted and blueshifted velocities (+2600 km/s and -1500 km/s), originating from more distant regions (D = 0.1 pc). The photo-ionized model explains the broader component, while the two narrower components can be explained by either photo-ionization or collisional ionization. One interpretation is that the broader component is an outflow at ~10^2 R_S (R_S; Schwarzschild radius) and the narrow component is a shock-heated plasma close to the torus, with a possible connection to the JWST-discovered outflow outside the torus. Two blueshifted absorption lines are detected at ~7.1 keV (~10^4 km/s) and ~10.6 keV (~10^5 km/s). The line significance of the 10.6 keV line is above 98%. The absorption line components might be attributed to the broad emission component. These results demonstrate the high potential of XRISM/Resolve to characterize ionized emission and absorption features in the Fe-K band. Our findings establish a new benchmark in the study of circumnuclear environments in low-luminosity radio galaxies, thereby contributing to a broader understanding of AGN unification.
Paper Structure (30 sections, 8 equations, 19 figures, 12 tables)

This paper contains 30 sections, 8 equations, 19 figures, 12 tables.

Table of Contents

  1. Introduction
  2. Observation and data reduction
  3. XRISM
  4. NuSTAR
  5. Spectral analysis
  6. Continuum modeling
  7. Search for lines
  8. Physical modeling for the neutral fluorescence lines
  9. Gaussian modeling for ionized Fe-K emission lines
  10. Physical modeling of the ionized emission line features
  11. Photo-ionized emission modeling
  12. Collisional ionized emission modeling
  13. Combination of the photo-ionized emission and collisional ionized emission
  14. Modeling of the absorption line features
  15. PION modeling
  16. ...and 15 more sections

Figures (19)

  • Figure 1: XRISM/Resolve ($3-12$ keV) and NuSTAR ($11.2-60$ keV) spectra with the model curve of the MT3 model, wherein the black point, the blue point, the green point, and the red line represent the Resolve spectra, FPMA spectra, FPMB spectra, and the model curve of the MT3 model, respectively. The Resolve spectrum is binned by a factor of 10 after the optimal binning for visual clarity.
  • Figure 2: $3.4-6.1$ keV band
  • Figure 3: $6.1-7.5$ keV band
  • Figure 4: $10.2-11.1$ keV band
  • Figure 6: XRISM/Resolve ($6.2-7.2$ keV) spectra with the model curve of the MT3 plus five Gaussian model, wherein the black point, the red line, the cyan dashed-line, the blue dashed-line, the orange dashed-line, the green dashed-line, and the magenta dashed-line represent the Resolve spectra, MT3 model, power-low component, first, second, third MyTorus component, and Gaussian component, respectively. The Resolve spectrum is binned by a factor of 3 after the optimal binning for visual clarity.
  • ...and 14 more figures