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A XRISM/Resolve view of the dynamics in the hot gaseous atmosphere of M87

XRISM Collaboration, M. Audard, H. Awaki, R. Ballhausen, A. Bamba, E. Behar, R. Boissay-Malaquin, L. Brenneman, G. V. Brown, L. Corrales, E. Costantini, R. Cumbee, M. Diaz Trigo, C. Done, T. Dotani, K. Ebisawa, M. E. Eckart, D. Eckert, S. Eguchi, T. Enoto, Y. Ezoe, A. Foster, R. Fujimoto, Y. Fujita, Y. Fukazawa, K. Fukushima, A. Furuzawa, L. Gallo, J. A. García, L. Gu, M. Guainazzi, K. Hagino, K. Hamaguchi, I. Hatsukade, K. Hayashi, T. Hayashi, N. Hell, E. Hodges-Kluck, A. Hornschemeier, Y. Ichinohe, D. Ishi, M. Ishida, K. Ishikawa, Y. Ishisaki, J. Kaastra, T. Kallman, E. Kara, S. Katsuda, Y. Kanemaru, R. Kelley, C. Kilbourne, S. Kitamoto, S. Kobayashi, T. Kohmura, A. Kubota, M. Leutenegger, M. Loewenstein, Y. Maeda, M. Markevitch, H. Matsumoto, K. Matsushita, D. McCammon, B. McNamara, F. Mernier, E. D. Miller, J. M. Miller, I. Mitsuishi, M. Mizumoto, T. Mizuno, K. Mori, K. Mukai, H. Murakami, R. Mushotzky, H. Nakajima, K. Nakazawa, J. -U. Ness, K. Nobukawa, M. Nobukawa, H. Noda, H. Odaka, S. Ogawa, A. Ogorzałek, T. Okajima, N. Ota, S. Paltani, R. Petre, P. Plucinsky, F. S. Porter, K. Pottschmidt, K. Sato, T. Sato, M. Sawada, H. Seta, M. Shidatsu, A. Simionescu, R. Smith, H. Suzuki, A. Szymkowiak, H. Takahashi, M. Takeo, T. Tamagawa, K. Tamura, T. Tanaka, A. Tanimoto, M. Tashiro, Y. Terada, Y. Terashima, Y. Tsuboi, M. Tsujimoto, H. Tsunemi, T. Tsuru, A. Tümer, H. Uchida, N. Uchida, Y. Uchida, H. Uchiyama, S. Ueda, Y. Ueda, S. Uno, J. Vink, S. Watanabe, B. J. Williams, S. Yamada, S. Yamada, H. Yamaguchi, K. Yamaoka, N. Yamasaki, M. Yamauchi, S. Yamauchi, T. Yaqoob, T. Yoneyama, T. Yoshida, M. Yukita, I. Zhuravleva, M. Charbonneau, N. Dizdar, M. Fujita, D. Ito, J. Martin, H. McCall, H. Russell, J. ZuHone

TL;DR

XRISM Resolve delivers the first direct measurements of ICM velocities in the Virgo/M87 core, revealing a sharp central velocity-dispersion peak ($\

Abstract

The XRISM/Resolve microcalorimeter directly measured the gas velocities in the core of the Virgo Cluster, the closest example of AGN feedback in a cluster. This proximity allows us to resolve the kinematic impact of feedback on scales down to 5 kpc. Our spectral analysis reveals a high velocity dispersion of $σ_v$=262 (+45 / -38) km/s near the AGN, which steeply declines to ~60 km/s between 5 and 25 kpc in the northwest direction. The observed line-of-sight bulk velocity in all regions is broadly consistent with the central galaxy, M87, with a mild trend toward blueshifted motions at larger radii. Systematic uncertainties have been carefully assessed and do not affect the measurements. The central velocities, if attributed entirely to isotropic turbulence, correspond to a transonic ICM at sub-6 kpc scales with three-dimensional Mach number 0.69 (+0.14 / -0.11) and a non-thermal pressure fraction of 21 (+7 / -5)%. Simple models of weak shocks and sound waves and calculations assuming isotropic turbulence both support the hypothesis that the velocity field reflects a mix of shock-driven expansion and turbulence. Compared to other clusters observed by XRISM to date, M87's central region stands out as the most kinematically disturbed, exhibiting both the highest velocity dispersion and the largest 3D Mach number, concentrated at the smallest physical scales.

A XRISM/Resolve view of the dynamics in the hot gaseous atmosphere of M87

TL;DR

XRISM Resolve delivers the first direct measurements of ICM velocities in the Virgo/M87 core, revealing a sharp central velocity-dispersion peak ($\

Abstract

The XRISM/Resolve microcalorimeter directly measured the gas velocities in the core of the Virgo Cluster, the closest example of AGN feedback in a cluster. This proximity allows us to resolve the kinematic impact of feedback on scales down to 5 kpc. Our spectral analysis reveals a high velocity dispersion of =262 (+45 / -38) km/s near the AGN, which steeply declines to ~60 km/s between 5 and 25 kpc in the northwest direction. The observed line-of-sight bulk velocity in all regions is broadly consistent with the central galaxy, M87, with a mild trend toward blueshifted motions at larger radii. Systematic uncertainties have been carefully assessed and do not affect the measurements. The central velocities, if attributed entirely to isotropic turbulence, correspond to a transonic ICM at sub-6 kpc scales with three-dimensional Mach number 0.69 (+0.14 / -0.11) and a non-thermal pressure fraction of 21 (+7 / -5)%. Simple models of weak shocks and sound waves and calculations assuming isotropic turbulence both support the hypothesis that the velocity field reflects a mix of shock-driven expansion and turbulence. Compared to other clusters observed by XRISM to date, M87's central region stands out as the most kinematically disturbed, exhibiting both the highest velocity dispersion and the largest 3D Mach number, concentrated at the smallest physical scales.

Paper Structure

This paper contains 30 sections, 7 equations, 10 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Observations and Data Reduction
  3. XRISM/Resolve
  4. Observations
  5. Data Reduction
  6. Chandra
  7. Observations
  8. Data Reduction
  9. NuSTAR
  10. Observations
  11. Data Reduction
  12. Data Analysis
  13. Non-thermal contribution from the AGN and LMXBs
  14. Chandra
  15. NuSTAR
  16. ...and 15 more sections

Figures (10)

  • Figure 1: Residual Chandra images (images divided by the best-fit models to emphasize substructure) of M87 with the central and northwest Resolve pointings overlaid. Left: 0.5-2.0 keV image. In this energy band, M87's AGN/jet and arms are prominent. Right: 3.0-7.0 keV image. The AGN and jet have been masked and filled in with values of surrounding pixels. The division into 3 sky regions is illustrated by the black shapes, with the corresponding detector regions shown in color. This energy band was used for image ARF creation.
  • Figure 2: Flux comparison between best-fit values from Chandra (red), XRISM with abundances free (blue), and XRISM with abundances tied to Fe (orange). The red-filled triangle point comes from resolved LMXBs in 2005 Chandra data. The white-filled triangle point comes from a value taken from 2024 Chandra data within a 0.6’ radius, extrapolated to the expected value for a 1’ radius for comparison with detector 1. XRISM fits were performed in the band 3-11 keV.
  • Figure 3: Observed spectra, best-fit models, and fit residuals using default choice of modeling (see subsection \ref{['subsec:model']}). Top panels: 4.2-7 keV fit for each of the 3 regions, including components that contributed to the total model. Contributions from off-set regions due to spatial spectral mixing are plotted as dashed lines. Bottom panels: Zoomed view of the strongest He-like Fe emission lines and fit residuals from the 4.2-7 keV fit.
  • Figure 4: Distribution of the velocity-related properties of the ICM from the default 4.2-7 keV fit, as described in the text. Note that the redshifts are not heliocentric corrected, as this step is performed in the conversion to bulk velocity.
  • Figure 5: Distribution of the measured properties of the ICM shown with 1$\sigma$ uncertainties. The four panels show (1) gas temperature, (2) Fe abundance with respect to solar, (3) line-of-sight velocity dispersion, (4) redshift. The gray shaded regions demarcate the statistical uncertainties from the default 4.2-7 keV band fit. The points, from left to right, correspond to (A) the 4.2-7 keV band but calculated with AtomDB v. 3.0.9, (B) the 4.2-7 keV band but using the LMXB fluxes from the model where abundances are tied to Fe, (C) the 4.2-7 keV band with a 2T model, (D, E) the 4.2-7 keV band with off-axis ARFs varied by $\pm 30\%$, (F, G) the 4.2-7 keV band with the NXB normalization varied by $\pm 20\%$, (H) the 4.2-7 keV band with the default choices calculated with SPEX 3.08.01, (I) the 3-11 keV band in AtomDB 3.1.3, with default choices but the He-like Fe W line removed, and (J) the 3-11 keV band with the default choices calculated in AtomDB 3.1.3.
  • ...and 5 more figures