TY - JOUR
T1 - Hitomi observation of radio galaxy NGC 1275
T2 - The first X-ray microcalorimeter spectroscopy of Fe-Kα line emission from an active galactic nucleus
AU - Hitomi Collaboration
AU - Aharonian, Felix
AU - Akamatsu, Hiroki
AU - Akimoto, Fumie
AU - Allen, Steven W.
AU - Angelini, Lorella
AU - Audard, Marc
AU - Awaki, Hisamitsu
AU - Axelsson, Magnus
AU - Bamba, Aya
AU - Bautz, Marshall W.
AU - Blandford, Roger
AU - Brenneman, Laura W.
AU - Brown, Gregory V.
AU - Bulbul, Esra
AU - Cackett, Edward M.
AU - Chernyakova, Maria
AU - Chiao, Meng P.
AU - Coppi, Paolo S.
AU - Costantini, Elisa
AU - De Plaa, Jelle
AU - De Vries, Cor P.
AU - Den Herder, Jan Willem
AU - Done, Chris
AU - Dotani, Tadayasu
AU - Ebisawa, Ken
AU - Eckart, Megan E.
AU - Enoto, Teruaki
AU - Ezoe, Yuichiro
AU - Fabian, Andrew C.
AU - Ferrigno, Carlo
AU - Foster, Adam R.
AU - Fujimoto, Ryuichi
AU - Fukazawa, Yasushi
AU - Furuzawa, Akihiro
AU - Galeazzi, Massimiliano
AU - Gallo, Luigi C.
AU - Gandhi, Poshak
AU - Giustini, Margherita
AU - Goldwurm, Andrea
AU - Gu, Liyi
AU - Guainazzi, Matteo
AU - Haba, Yoshito
AU - Hagino, Kouichi
AU - Hamaguchi, Kenji
AU - Harrus, Ilana M.
AU - Hatsukade, Isamu
AU - Hayashi, Katsuhiro
AU - Hayashi, Takayuki
AU - Hayashida, Kiyoshi
AU - Kubota, Aya
N1 - Funding Information:
We acknowledge the support from the JSPS Core-to-Core Program, and all the JAXA members who have contributed to the ASTRO-H (Hitomi) project. All US members gratefully acknowledge support through the NASA Science Mission Directorate. Stanford and SLAC members acknowledge support via DoE contract to SLAC National Accelerator Laboratory DE-AC3-76SF00515. Part of this work was performed under the auspices of the US DoE by LLNL under Contract DE-AC52-07NA27344. Support from the European Space Agency is gratefully acknowledged. The French members acknowledge support from CNES, the Centre National d’Études Spatiales. SRON is supported by NWO, the Netherlands Organization for Scientific Research. The Swiss team acknowledges the support of the Swiss Secretariat for Education, Research and Innovation (SERI). The Canadian Space Agency is acknowledged for the support of Canadian members. We acknowledge support from JSPS/MEXT KAKENHI grant numbers 15J02737, 15H00773, 15H00785, 15H02090, 15H03639, 15H05438, 15K05107, 15K17610, 15K17657, 16J00548, 16J02333, 16H00949, 16H06342, 16K05295, 16K05296, 16K05300, 16K13787, 16K17672, 16K17673, 21659292, 23340055, 23340071, 23540280, 24105007, 24244014,
Funding Information:
24540232, 25105516, 25109004, 25247028, 25287042, 25400236, 25800119, 26109506, 26220703, 26400228, 26610047, 26800102, JP15H02070, JP15H03641, JP15H03642, JP15H06896, JP16H03983, JP16K05296, JP16K05309, JP16K17667, and JP16K05296. The following NASA grants are acknowledged: NNX15AC76G, NNX15AE16G, NNX15AK71G, NNX15AU54G, NNX15AW94G, and NNG15PP48P to Eureka Scientific. H. Akamatsu acknowledges the support of NWO via a Veni grant. C. Done acknowledges STFC funding under grant ST/L00075X/1. A. Fabian and C. Pinto acknowledge ERC Advanced Grant 340442. P. Gandhi acknowledges JAXA International Top Young Fellowship and UK Science and Technology Funding Council (STFC) grant ST/J003697/2. Y. Ichinohe, K. Nobukawa, and H. Seta are supported by the Research Fellow of JSPS for Young Scientists. N. Kawai is supported by the Grant-in-Aid for Scientific Research on Innovative Areas “New Developments in Astrophysics Through Multi-Messenger Observations of Gravitational Wave Sources.” S. Kitamoto is partially supported by the MEXT Supported Program for the Strategic Research Foundation at Private Universities, 2014– 2018. B. McNamara and S. Safi-Harb acknowledge support from NSERC. T. Dotani, T. Takahashi, T. Tamagawa, M. Tsujimoto, and Y. Uchiyama acknowledge support from the Grant-in-Aid for Scientific Research on Innovative Areas “Nuclear Matter in Neutron Stars Investigated by Experiments and Astronomical Observations.” N. Werner is supported by the Lendület LP2016-11 grant from the Hungarian Academy of Sciences. D. Wilkins is supported by NASA through Einstein Fellowship grant number PF6-170160, awarded by the Chandra X-ray Center, operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060.
Publisher Copyright:
© The Author(s) 2017. Published by Oxford University Press on behalf of the Astronomical Society of Japan.
PY - 2018/3/1
Y1 - 2018/3/1
N2 - 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.
AB - 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.
KW - Galaxies: active
KW - Galaxies: individual (NGC 1275)
KW - Galaxies: radio galaxy
KW - Methods: observational
KW - X-rays: galaxies
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U2 - 10.1093/pasj/psx147
DO - 10.1093/pasj/psx147
M3 - Article
AN - SCOPUS:85058321980
VL - 70
JO - Publication of the Astronomical Society of Japan
JF - Publication of the Astronomical Society of Japan
SN - 0004-6264
IS - 2
M1 - psx147
ER -