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Hitomi constraints on the 3.5 keV line in the Perseus galaxy cluster.

Aharonian, F. A. and Akamatsu, H. and Akimoto, F. and Allen, S. W. and Angelini, L. and Arnaud, K. A. and Audard, M. and Awaki, H. and Axelsson, M. and Bamba, A. and Bautz, M. W. and Blandford, R. D. and Bulbul, E. and Brenneman, L. W. and Brown, G. V. and Cackett, E. M. and Chernyakova, M. and Chiao, M. P. and Coppi, P. and Costantini, E. and Plaa, J. de and Herder, J.-W. den and Done, C. and Dotani, T. and Ebisawa, K. and Eckart, M. E. and Enoto, T. and Ezoe, Y. and Fabian, A. C. and Ferrigno, C. and Foster, A. R. and Fujimoto, R. and Fukazawa, Y. and Furuzawa, A. and Galeazzi, M. and Gallo, L. C. and Gandhi, P. and Giustini, M. and Goldwurm, A. and Gu, L. and Guainazzi, M. and Haba, Y. and Hagino, K. and Hamaguchi, K. and Harrus, I. and Hatsukade, I. and Hayashi, K. and Hayashi, T. and Hayashida, K. and Hiraga, J. and Hornschemeier, A. E. and Hoshino, A. and Hughes, J. P. and Ichinohe, Y. and Iizuka, R. and Inoue, H. and Inoue, S. and Inoue, Y. and Ishibashi, K. and Ishida, M. and Ishikawa, K. and Ishisaki, Y. and Itoh, M. and Iwai, M. and Iyomoto, N. and Kaastra, J. S. and Kallman, T. and Kamae, T. and Kara, E. and Kataoka, J. and Katsuda, S. and Katsuta, J. and Kawaharada, M. and Kawai, N. and Kelley, R. L. and Khangulyan, D. and Kilbourne, C. A. and King, A. L. and Kitaguchi, T. and Kitamoto, S. and Kitayama, T. and Kohmura, T. and Kokubun, M. and Koyama, S. and Koyama, K. and Kretschmar, P. and Krimm, H. A. and Kubota, A. and Kunieda, H. and Laurent, P. and Lebrun, F. and Lee, S.-H. and Leutenegger, M. A. and Limousin, O. and Loewenstein, M. and Long, K. S. and Lumb, D. H. and Madejski, G. M. and Maeda, Y. and Maier, D. and Makishima, K. and Markevitch, M. and Matsumoto, H. and Matsushita, K. and McCammon, D. and McNamara, B. R. and Mehdipour, M. and Miller, E. D. and Miller, J. M. and Mineshige, S. and Mitsuda, K. and Mitsuishi, I. and Miyazawa, T. and Mizuno, T. and Mori, H. and Mori, K. and Moseley, H. and Mukai, K. and Murakami, H. and Murakami, T. and Mushotzky, R. F. and Nakagawa, T. and Nakajima, H. and Nakamori, T. and Nakano, T. and Nakashima, S. and Nakazawa, K. and Nobukawa, K. and Nobukawa, M. and Noda, H. and Nomachi, M. and Dell, S. L. O’ and Odaka, H. and Ohashi, T. and Ohno, M. and Okajima, T. and Ota, N. and Ozaki, M. and Paerels, F. and Paltani, S. and Parmar, A. and Petre, R. and Pinto, C. and Pohl, M. and Porter, F. S. and Pottschmidt, K. and Ramsey, B. D. and Reynolds, C. S. and Russell, H. R. and Safi-Harb, S. and Saito, S. and Sakai, K. and Sameshima, H. and Sasaki, T. and Sato, G. and Sato, K. and Sato, R. and Sawada, M. and Schartel, N. and Serlemitsos, P. J. and Seta, H. and Shidatsu, M. and Simionescu, A. and Smith, R. K. and Soong, Y. and Stawarz, Ł. and Sugawara, Y. and Sugita, S. and Szymkowiak, A. E. and Tajima, H. and Takahashi, H. and Takahashi, T. and Takeda, S. and Takei, Y. and Tamagawa, T. and Tamura, K. and Tamura, T. and Tanaka, T. and Tanaka, Yasuo and Tanaka, Yasuyuki and Tashiro, M. and Tawara, Y. and Terada, Y. and Terashima, Y. and Tombesi, F. and Tomida, H. and Tsuboi, Y. and Tsujimoto, M. and Tsunemi, H. and Tsuru, T. and Uchida, H. and Uchiyama, H. and Uchiyama, Y. and Ueda, S. and Ueda, Y. and Ueno, S. and Uno, S. and Urry, C. M. and Ursino, E. and Vries, C. P. de and Watanabe, S. and Werner, N. and Wik, D. R. and Wilkins, D. R. and Williams, B. J. and Yamada, S. and Yamaguchi, H. and Yamaoka, K. and Yamasaki, N. Y. and Yamauchi, M. and Yamauchi, S. and Yaqoob, T. and Yatsu, Y. and Yonetoku, D. and Yoshida, A. and Zhuravleva, I. and Zoghbi, A. (2017) 'Hitomi constraints on the 3.5 keV line in the Perseus galaxy cluster.', Astrophysical journal letters., 837 (1). L15.


High-resolution X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified E=3.5 keV emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The emission line expected for Perseus based on the XMM-Newton signal from the large cluster sample under the dark matter decay scenario is too faint to be detectable in the Hitomi data. However, the previously reported 3.5 keV flux from Perseus was anomalously high compared to the sample-based prediction. We find no unidentified line at the reported high flux level. Taking into account the XMM measurement uncertainties for this region, the inconsistency with Hitomi is at a 99% significance for a broad dark-matter line and at 99.7% for a narrow line from the gas. We do not find anomalously high fluxes of the nearby faint K line or the Ar satellite line that were proposed as explanations for the earlier 3.5 keV detections. We do find a hint of a broad excess near the energies of high-n transitions of Sxvi (E=3.44 keV rest-frame) -- a possible signature of charge exchange in the molecular nebula and another proposed explanation for the unidentified line. While its energy is consistent with XMM pn detections, it is unlikely to explain the MOS signal. A confirmation of this interesting feature has to wait for a more sensitive observation with a future calorimeter experiment.

Item Type:Article
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Publisher statement:© 2017. The American Astronomical Society. All rights reserved.
Date accepted:19 February 2017
Date deposited:11 July 2017
Date of first online publication:03 March 2017
Date first made open access:11 July 2017

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