arXiv · 1710.04648
Measurements of resonant scattering in the Perseus cluster core with Hitomi SXS
Abstract
Thanks to its high spectral resolution (~5 eV at 6 keV), the Soft X-ray Spectrometer (SXS) on board Hitomi enables us to measure the detailed structure of spatially resolved emission lines from highly ionized ions in galaxy clusters for the first time. In this series of papers, using the SXS we have measured the velocities of gas motions, metallicities and the multi-temperature structure of the gas in the core of the Perseus cluster. Here, we show that when inferring physical properties from line emissivities in systems like Perseus, the resonant scattering (RS) effect should be taken into account. In the Hitomi waveband, RS mostly affects the FeXXV He$\alpha$ line ($w$) - the strongest line in the spectrum. The flux measured by Hitomi in this line is suppressed by a factor ~1.3 in the inner ~30 kpc, compared to predictions for an optically thin plasma; the suppression decreases with the distance from the center. The $w$ line also appears slightly broader than other lines from the same ion. The observed distortions of the $w$ line flux, shape and distance dependence are all consistent with the expected effect of the resonant scattering in the Perseus core. By measuring the ratio of fluxes in optically thick ($w$) and thin (FeXXV forbidden, He$\beta$, Ly$\alpha$) lines, and comparing these ratios with predictions from Monte Carlo radiative transfer simulations, the velocities of gas motions have been obtained. The results are consistent with the direct measurements of gas velocities from line broadening described elsewhere in this series, although the systematic and statistical uncertainties remain significant. Further improvements in the predictions of line emissivities in plasma models, and deeper observations with future X-ray missions will enable RS measurements to provide powerful constraints on the amplitude and anisotropy of clusters gas motions.
Explore related subjects
Keep this discovery
Hitomi Collaboration, Felix Aharonian, Hiroki Akamatsu, Fumie Akimoto, Steven W. Allen, Lorella Angelini, Marc Audard, Hisamitsu Awaki, Magnus Axelsson, Aya Bamba, Marshall W. Bautz, Roger Blandford, Laura W. Brenneman, Greg V. Brown, Esra Bulbul, Edward M. Cackett, Maria Chernyakova, Meng P. Chiao, Paolo S. Coppi, Elisa Costantini, Jelle de Plaa, Cor P. de Vries, Jan-Willem den Herder, Chris Done, Tadayasu Dotani, Ken Ebisawa, Megan E. Eckart, Teruaki Enoto, Yuichiro Ezoe, Andrew C. Fabian, Carlo Ferrigno, Adam R. Foster, Ryuichi Fujimoto, Yasushi Fukazawa, Akihiro Furuzawa, Massimiliano Galeazzi, Luigi C. Gallo, Poshak Gandhi, Margherita Giustini, Andrea Goldwurm, Liyi Gu, Matteo Guainazzi, Yoshito Haba, Kouichi Hagino, Kenji Hamaguchi, Ilana M. Harrus, Isamu Hatsukade, Katsuhiro Hayashi, Takayuki Hayashi, Kiyoshi Hayashida, Junko S. Hiraga, Ann Hornschemeier, Akio Hoshino, John P. Hughes, Yuto Ichinohe, Ryo Iizuka, Hajime Inoue, Yoshiyuki Inoue, Manabu Ishida, Kumi Ishikawa, Yoshitaka Ishisaki, Jelle Kaastra, Tim Kallman, Tsuneyoshi Kamae, Jun Kataoka, Satoru Katsuda, Nobuyuki Kawai, Richard L. Kelley, Caroline A. Kilbourne, Takao Kitaguchi, Shunji Kitamoto, Tetsu Kitayama, Takayoshi Kohmura, Motohide Kokubun, Katsuji Koyama, Shu Koyama, Peter Kretschmar, Hans A. Krimm, Aya Kubota, Hideyo Kunieda, Philippe Laurent, Shiu-Hang Lee, Maurice A. Leutenegger, Olivier O. Limousin, Michael Loewenstein, Knox S. Long, David Lumb, Greg Madejski, Yoshitomo Maeda, Daniel Maier, Kazuo Makishima, Maxim Markevitch, Hironori Matsumoto, Kyoko Matsushita, Dan McCammon, Brian R. McNamara, Missagh Mehdipour, Eric D. Miller, Jon M. Miller, Shin Mineshige. 2017-10-12. Measurements of resonant scattering in the Perseus cluster core with Hitomi SXS. https://doi.org/10.1093/pasj/psx127
Cite the original work for its findings. Save a collection to share your selection of sources.