Paper: XRISM Constraints on Unidentified X-Ray Emission Lines, Including the 3.5 keV Line, in the Stacked Spectrum of 10 Galaxy Clusters
Authors: Marc Audard, Hisamitsu Awaki, Ralf Ballhausen, Aya Bamba, Ehud Behar, Rozenn Boissay-Malaquin, Laura Brenneman, Gregory V. Brown, Lia Corrales, Elisa Costantini, Renata Cumbee, Maria Diaz Trigo, Chris Done, Tadayasu Dotani, Ken Ebisawa, Megan E. Eckart, Dominique Eckert, Satoshi Eguchi, Teruaki Enoto, Yuichiro Ezoe, Adam Foster, Ryuichi Fujimoto, Yutaka Fujita, Yasushi Fukazawa, Kotaro Fukushima, Akihiro Furuzawa, Luigi Gallo, Javier A. García, Liyi Gu, Matteo Guainazzi, Kouichi Hagino, Kenji Hamaguchi, Isamu Hatsukade, Katsuhiro Hayashi, Takayuki Hayashi, Natalie Hell, Edmund Hodges-Kluck, Ann Hornschemeier, Yuto Ichinohe, Daiki Ishi, Manabu Ishida, Kumi Ishikawa, Yoshitaka Ishisaki, Jelle Kaastra, Timothy Kallman, Erin Kara, Satoru Katsuda, Yoshiaki Kanemaru, Richard Kelley, Caroline Kilbourne, Shunji Kitamoto, Shogo Kobayashi, Takayoshi Kohmura, Aya Kubota, Maurice Leutenegger, Michael Loewenstein, Yoshitomo Maeda, Maxim Markevitch, Hironori Matsumoto, Kyoko Matsushita, Dan McCammon, Brian McNamara, François Mernier, Eric D. Miller, Jon M. Miller, Ikuyuki Mitsuishi, Misaki Mizumoto, Tsunefumi Mizuno, Koji Mori, Koji Mukai, Hiroshi Murakami, Richard Mushotzky, Hiroshi Nakajima, Kazuhiro Nakazawa, Jan-Uwe Ness, Kumiko Nobukawa, Masayoshi Nobukawa, Hirofumi Noda, Hirokazu Odaka, Shoji Ogawa, Anna Ogorzałek, Takashi Okajima, Naomi Ota, Stephane Paltani, Robert Petre, Paul Plucinsky, Frederick S. Porter, Katja Pottschmidt, Kosuke Sato, Toshiki Sato, Makoto Sawada, Hiromi Seta, Megumi Shidatsu, Aurora Simionescu, Randall Smith, Hiromasa Suzuki, Andrew Szymkowiak, Hiromitsu Takahashi, Mai Takeo, Toru Tamagawa, Keisuke Tamura, Takaaki Tanaka, Atsushi Tanimoto, Makoto Tashiro, Yukikatsu Terada, Yuichi Terashima, Yohko Tsuboi, Masahiro Tsujimoto, Hiroshi Tsunemi, Takeshi Tsuru, Ayşegül Tümer, Hiroyuki Uchida, Nagomi Uchida, Yuusuke Uchida, Hideki Uchiyama, Shutaro Ueda, Yoshihiro Ueda, Shinichiro Uno, Jacco Vink, Shin Watanabe, Brian J. Williams, Satoshi Yamada, Shinya Yamada, Hiroya Yamaguchi, Kazutaka Yamaoka, Noriko Yamasaki, Makoto Yamauchi, Shigeo Yamauchi, Tahir Yaqoob, Tomokage Yoneyama, Tessei Yoshida, Mihoko Yukita, Irina Zhuravleva, Jean-Paul Breuer, Priyanka Chakraborty, Stefano Ettori, Andrew Fabian, Annie Heinrich, Marie Kondo, Julie HLavacek-Larrondo, Hannah McCall, Paul Nulsen, Tom Rose, Helen Russell, Arnab Sarkar, Evan Scannapieco, Kazunori Suda, Ming Sun, Prathamesh Tamhane, Nhut Truong, Norbert Werner, Congyao Zhang
Figure caption: The stacked XRISM spectra in the rest-frame 3–4 keV. Black shows the full cluster sample (10 clusters, 3.75 Ms total exposure), red shows the hot subsample (six clusters with M200c > 1014.5 M⊙, 2.49 Ms total exposure), and blue shows the cool clusters in the sample (four clusters with M200c < 1014.5 M⊙, 1.26 Ms total). The green curve shows the best fit with a two bapec model to the full sample. For clarity, the hot cluster spectrum is lowered by a factor of 2, and the cool cluster spectrum is lowered by a factor of 3. Detected atomic lines in this energy range are marked. The atomic lines have a velocity dispersion of 150–160 km s−1, which is ∼6 times smaller than the velocity dispersion we adopted for the DM line search in the full sample. For the cool and hot subsamples, the difference is ∼4 and ∼7 times, respectively. Thus, the expected DM line in these spectra should be 4–7 times broader than the shown atomic lines. The green bracket shows the 90% confidence interval on the unidentified 3.5 keV line energy for the most restrictive XMM-Newton MOS stacked-clusters sample in B14.