Hitomi observation of radio galaxy NGC 1275: The first X-ray microcalorimeter spectroscopy of Fe-Kα line emission from an active galactic nucleus
Done, Chris; Safi-Harb, Samar; Hamaguchi, Kenji; Nakagawa, Takao; McNamara, Brian R.; Dotani, Tadayasu; Miller, Eric D.; Fabian, Andrew C.; Brenneman, Laura W.; Sugawara, Yasuharu; Maeda, Yoshitomo; Ishida, Manabu; Katsuda, Satoru; Petre, Robert; Enoto, Teruaki; Kunieda, Hideyo; Haba, Yoshito; Allen, Steven W.; Gandhi, Poshak; Tsujimoto, Masahiro; Okajima, Takashi; Eckart, Megan E.; Hayashi, Takayuki; Hoshino, Akio; Iizuka, Ryo; Kelley, Richard L.; Kilbourne, Caroline A.; Leutenegger, Maurice A.; Mori, Hideyuki; Porter, Frederick S.; Sato, Kosuke; Serlemitsos, Peter J.; Szymkowiak, Andrew; Yaqoob, Tahir; Yamaoka, Kazutaka; Fukazawa, Yasushi; Kamae, Tsuneyoshi; Kokubun, Motohide; Makishima, Kazuo; Nakazawa, Kazuhiro; Ohno, Masanori; Sato, Goro; Sugita, Satoshi; Tajima, Hiroyasu; Takahashi, Tadayuki; Tashiro, Makoto S.; Terada, Yukikatsu; Yamauchi, Makoto; Yamaguchi, Hiroya; Koyama, Katsuji; Hughes, John P.; Kretschmar, Peter; Pottschmidt, Katja; Ezoe, Yuichiro; Ishikawa, Kumi; Ohashi, Takaya; Mitsuda, Kazuhisa; Fujimoto, Ryuichi; Gu, Liyi; Reynolds, Christopher S.; Mehdipour, Missagh; Uchida, Hiroyuki; Ueda, Yoshihiro; Kawamuro, Taiki; Awaki, Hisamitsu; Terashima, Yuichi; Yamasaki, Noriko Y.; Ebisawa, Ken; Zoghbi, Abderahmen; Miller, Jon M.; Hayashida, Kiyoshi; Nakajima, Hiroshi; Matsumoto, Hironori; Takahashi, Hiromitsu; Paerels, Frits; Kaastra, Jelle; Bamba, Aya; Mori, Koji; Guainazzi, Matteo; Uchiyama, Yasunobu; Kitaguchi, Takao; Urry, C. Megan; Krimm, Hans A.; Miyazawa, Takuya; Kubota, Aya; Nobukawa, Masayoshi; Nakashima, Shinya; Tsuru, Takeshi Go; Tanaka, Takaaki; Galeazzi, Massimiliano; Gallo, Luigi C.; Yonetoku, Daisuke; Angelini, Lorella; Tombesi, Francesco; Mukai, Koji; Uchiyama, Hideki; Hitomi Collaboration; Aharonian, Felix; Akamatsu, Hiroki; Akimoto, Fumie; Audard, Marc; Axelsson, Magnus; Bautz, Marshall W.; Blandford, Roger; Brown, Gregory V.; Bulbul, Esra; Cackett, Edward M.; Chernyakova, Maria; Chiao, Meng P.; Coppi, Paolo S.; Costantini, Elisa; de Plaa, Jelle; de Vries, Cor P.; den Herder, Jan-Willem; Ferrigno, Carlo; Foster, Adam R.; Furuzawa, Akihiro; Giustini, Margherita; Goldwurm, Andrea; Hagino, Kouichi; Harrus, Ilana M.; Hatsukade, Isamu; Hayashi, Katsuhiro; Hiraga, Junko S.; Hornschemeier, Ann; Ichinohe, Yuto; Inoue, Hajime; Inoue, Yoshiyuki; Ishisaki, Yoshitaka; Iwai, Masachika; Kallman, Tim; Kataoka, Jun; Kawai, Nobuyuki; Kitamoto, Shunji; Kitayama, Tetsu; Kohmura, Takayoshi; Koyama, Shu; Laurent, Philippe; Lee, Shiu-Hang; Limousin, Olivier O.; Loewenstein, Michael; Long, Knox S.; Lumb, David; Madejski, Greg; Maier, Daniel; Markevitch, Maxim; Matsushita, Kyoko; McCammon, Dan; Mineshige, Shin; Mitsuishi, Ikuyuki; Mizuno, Tsunefumi; Murakami, Hiroshi; Mushotzky, Richard F.; Nakamori, Takeshi; Nobukawa, Kumiko K.; Noda, Hirofumi; Odaka, Hirokazu; Ota, Naomi; Ozaki, Masanobu; Paltani, Stéphane; Pinto, Ciro; Saito, Shinya; Sakai, Kazuhiro; Sasaki, Toru; Sato, Rie; Sawada, Makoto; Schartel, Norbert; Seta, Hiromi; Shidatsu, Megumi; Simionescu, Aurora; Smith, Randall K.; Soong, Yang; Stawarz, Łukasz; Takei, Yoh; Tamagawa, Toru; Tamura, Takayuki; Tanaka, Yasuo; Tanaka, Yasuyuki T.; Tawara, Yuzuru; Tomida, Hiroshi; Tsuboi, Yohko; Tsunemi, Hiroshi; Ueda, Shutaro; Ursino, Eugenio; Watanabe, Shin; Werner, Norbert; Wilkins, Dan R.; Williams, Brian J.; Yamada, Shinya; Yamauchi, Shigeo; Yatsu, Yoichi; Zhuravleva, Irina; Takeda, Shin'ichiro; Uno, Shin'ichiro
Ireland, Netherlands, Japan, United States, Switzerland, Sweden, United Kingdom, Canada, France, Spain, Poland, Hungary, Czech Republic
Abstract
The origin of the narrow Fe-Kα fluorescence line at 6.4 keV from active galactic nuclei has long been under debate; some of the possible sites are the outer accretion disk, the broad line region, a molecular torus, or interstellar/intracluster media. In 2016 February-March, we performed the first X-ray microcalorimeter spectroscopy with the Soft X-ray Spectrometer (SXS) on board the Hitomi satellite of the Fanaroff-Riley type I radio galaxy NGC 1275 at the center of the Perseus cluster of galaxies. With the high-energy resolution of ∼5 eV at 6 keV achieved by Hitomi/SXS, we detected the Fe-Kα line with ∼5.4 σ significance. The velocity width is constrained to be 500-1600 km s-1 (FWHM for Gaussian models) at 90% confidence. The SXS also constrains the continuum level from the NGC 1275 nucleus up to ∼20 keV, giving an equivalent width of ∼20 eV for the 6.4 keV line. Because the velocity width is narrower than that of the broad Hα line of ∼2750 km s-1, we can exclude a large contribution to the line flux from the accretion disk and the broad line region. Furthermore, we performed pixel map analyses on the Hitomi/SXS data and image analyses on the Chandra archival data, and revealed that the Fe-Kα line comes from a region within ∼1.6 kpc of the NGC 1275 core, where an active galactic nucleus emission dominates, rather than that from intracluster media. Therefore, we suggest that the source of the Fe-Kα line from NGC 1275 is likely a low-covering-fraction molecular torus or a rotating molecular disk which probably extends from a parsec to hundreds of parsecs scale in the active galactic nucleus system.