The quiescent intracluster medium in the core of the Perseus cluster

Journal name:
Nature
Volume:
535,
Pages:
117–121
Date published:
DOI:
doi:10.1038/nature18627
Received
Accepted
Published online

Clusters of galaxies are the most massive gravitationally bound objects in the Universe and are still forming. They are thus important probes1 of cosmological parameters and many astrophysical processes. However, knowledge of the dynamics of the pervasive hot gas, the mass of which is much larger than the combined mass of all the stars in the cluster, is lacking. Such knowledge would enable insights into the injection of mechanical energy by the central supermassive black hole and the use of hydrostatic equilibrium for determining cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50-million-kelvin diffuse hot plasma filling its gravitational potential well. The active galactic nucleus of the central galaxy NGC 1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These bubbles probably induce motions in the intracluster medium and heat the inner gas, preventing runaway radiative cooling—a process known as active galactic nucleus feedback2, 3, 4, 5, 6. Here we report X-ray observations of the core of the Perseus cluster, which reveal a remarkably quiescent atmosphere in which the gas has a line-of-sight velocity dispersion of 164 ± 10 kilometres per second in the region 30–60 kiloparsecs from the central nucleus. A gradient in the line-of-sight velocity of 150 ± 70 kilometres per second is found across the 60-kiloparsec image of the cluster core. Turbulent pressure support in the gas is four per cent of the thermodynamic pressure, with large-scale shear at most doubling this estimate. We infer that a total cluster mass determined from hydrostatic equilibrium in a central region would require little correction for turbulent pressure.

At a glance

Figures

  1. Full array spectrum of the core of the Perseus cluster obtained by the Hitomi observatory.
    Figure 1: Full array spectrum of the core of the Perseus cluster obtained by the Hitomi observatory.

    The redshift of the Perseus cluster is z = 0.01756. The inset has a logarithmic scale, which allows the weaker lines to be better seen. The flux S is plotted against photon energy E.

  2. Spectra of Fe xxv Heα, Fe xxvi Lyα and Fe xxv Heβ from the outer region.
    Figure 2: Spectra of Fe xxv Heα, Fe xxvi Lyα and Fe xxv Heβ from the outer region.

    ac, Gaussians (red curves) were fitted to lines with energies (marked by short red lines) from laboratory measurements in the case of He-like Fe xxv (a, c) and from theory in the case of Fe xxvi Lyα (b; see Extended Data Table 1 for details) with the same velocity dispersion (σv = 164 km s−1), except for the Fe xxv Heα resonant line, which was allowed to have its own width. Instrumental broadening with (blue line) and without (black line) thermal broadening are indicated in a. The redshift (z = 0.01756) is the cluster value to which the data were self-calibrated using the Fe xxv Heα lines. The strongest resonance (‘w’), intercombination (‘x’, ‘y’) and forbidden (‘z’) lines are indicated. The error bars are 1 s.d.

  3. The region of the Perseus cluster observed by the SXS.
    Figure 3: The region of the Perseus cluster observed by the SXS.

    a, The field of view of the SXS overlaid on a Chandra image. The nucleus of NGC 1275 is seen as the white dot with inner bubbles to the north and south. A buoyant outer bubble lies northwest of the centre of the field. A swirling cold front coincides with the second-most-outer contour. The central and outer regions are marked. b, The bulk velocity field across the imaged region. Colours show the difference from the velocity of the central galaxy NGC 1275 (whose redshift is z = 0.01756); positive difference means gas receding faster than the galaxy. The 1-arcmin pixels of the map correspond approximately to the angular resolution, but are not entirely independent (see Extended Data Fig. 5). The calibration uncertainty on velocities in individual pixels and in the overall baseline is 50 km s−1z = 0.00017).

  4. SXS spectrum of the full field overlaid with a CCD spectrum of the same region.
    Extended Data Fig. 1: SXS spectrum of the full field overlaid with a CCD spectrum of the same region.

    The CCD is the Suzaku X-ray imaging spectrometer (XIS) (red line); the difference in the continuum slope is due to differences in the effective areas of the instruments.

  5. The iron line complexes from the outer region compared with best-fit models.
    Extended Data Fig. 2: The iron line complexes from the outer region compared with best-fit models.

    ac, These have been obtained from various emission-line databases typically used in the literature. The spectra were modelled as a single-temperature, optically thin plasma in collisional ionization equilibrium using either APEC/ATOMDB 3.0.3 (ref 16; red) or SPEX 3.0 (ref. 17; blue). We determined the best-fit model by fitting the Hitomi spectrum from the outer 23 pixels in the energy range 6.4–8 keV, excluding the Fe Heα resonance line and Ni Heα line complex. We obtain consistent best-fit parameters, with both APEC and SPEX predicting a temperature of 4.1 ± 0.1 keV. The iron-to-hydrogen abundances are 0.62 ± 0.02 from APEC and 0.74 ± 0.02 from SPEX, relative to solar values31. The line broadening obtained from APEC, 146 ± 7 km s−1, is smaller than the best-fit SPEX value of 171 ± 7 km s−1, although both values are consistent with the line broadening obtained by fitting a set of Gaussians (the result presented in the main body of the paper). Apart from the Fe Heα w line affected by resonance scattering (a), both emission line models presented here currently have difficulty reproducing the measured Fe Heα intercombination lines (a) as well as the exact position of the Fe Heβ line (c). This motivates the model-independent approach adopted in the manuscript for determining the line widths. Error bars are 1 s.d.

  6. The Fe He-α line complex from the central region around the AGN.
    Extended Data Fig. 3: The Fe He-α line complex from the central region around the AGN.

    The 5.0–8.5-keV spectrum was modelled with an isothermal, optically thin plasma in collisional ionization equilibrium using either APEC/ATOMDB 3.0.3 (red) or SPEX 3.0 (blue), with an additional power-law component accounting for emission from the central AGN. During the fit we excluded the Fe Heα resonance line because this can be affected by resonant scattering of photons by the intracluster gas in the line of sight. The two spectral codes provide similar results with an average temperature of 3.8 ± 0.1 keV and metallicity consistent with the solar value. We obtain a velocity broadening of 156 ± 12 km s−1 from APEC and 178 ± 9 km s−1 from SPEX. Both models suggest that the resonant line has been suppressed in the central region. Error bars are 1 s.d.

  7. Confidence contours for joint fits of redshift z and velocity broadening σv are compared.
    Extended Data Fig. 4: Confidence contours for joint fits of redshift z and velocity broadening σv are compared.

    The three line complexes have been fitted independently. The contours are plotted at (68%, two parameters) and (95%). The three fits give consistent redshifts (with the one to which the data were self-calibrated) and broadening.

  8. The spatial response of the SXS array.
    Extended Data Fig. 5: The spatial response of the SXS array.

    The total broadband counts (colour scale) seen across the detector array (left), Fe Heα line counts (centre) that come mostly from the diffuse cluster plasma, and a model response of a point source centred in the pixel coincident with the nucleus of NGC 1275 (right) are compared. Brightness is normalized to the same peak value.

  9. The line-of-sight gas velocities overlaid on a deep Chandra image.
    Extended Data Fig. 6: The line-of-sight gas velocities overlaid on a deep Chandra image.

    The Chandra image is from ref. 32. The contours increase by a factor of 1.5. The numbers in the larger font indicate the velocity in each region (see also the colour scale). The 90% errors in the figure (numbers in the smaller font) are statistical only; our estimate of the calibration uncertainty in individual pixels is 50 km s−1. Heliocentric correction has been applied. Velocities are shown relative to that of NGC 1275, whose redshift is z = 0.01756 (ref. 33).

  10. The SXS field overlaid on the cold gas nebulosity surrounding NGC 1275.
    Extended Data Fig. 7: The SXS field overlaid on the cold gas nebulosity surrounding NGC 1275.

    The image shows Hα emission34. The radial velocity along the long northern filament measured from CO data21 decreases, south to north (within the SXS field of view), from about +50 km s−1 to −65 km s−1. This is similar to the trend seen in the SXS velocity map (Extended Data Fig. 6).

  11. In-flight spectral resolution of the SXS.
    Extended Data Fig. 8: In-flight spectral resolution of the SXS.

    a, The composite spectrum of all pixels (excluding the calibration pixel) when they were exposed to the 55Fe source on the filter wheel. The blue line shows the expected natural line shape and the red line shows the observed profile (error bars are 1 s.d.). b, A histogram of pixel resolution. N is the number of pixels sharing that resolution.

Tables

  1. Line energies used in the Gaussian fits
    Extended Data Table 1: Line energies used in the Gaussian fits

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Author information

Affiliations

  1. Astronomy and Astrophysics Section, Dublin Institute for Advanced Studies, Dublin 2, Ireland

    • Felix Aharonian &
    • Maria Chernyakova
  2. National Research Nuclear University (MEPHI), 115409 Moscow, Russia

    • Felix Aharonian
  3. SRON Netherlands Institute for Space Research, Utrecht, The Netherlands

    • Hiroki Akamatsu,
    • Elisa Costantini,
    • Jelle de Plaa,
    • Jan-Willem den Herder,
    • Margherita Giustini,
    • Liyi Gu,
    • Jelle Kaastra,
    • Missagh Mehdipour &
    • Cor de Vries
  4. Department of Physics, Nagoya University, Aichi 464-8602, Japan

    • Fumie Akimoto,
    • Akihiro Furuzawa,
    • Takayuki Hayashi,
    • Kazunori Ishibashi,
    • Hideyo Kunieda,
    • Ikuyuki Mitsuishi,
    • Takuya Miyazawa,
    • Keisuke Tamura,
    • Yuzuru Tawara &
    • Kazutaka Yamaoka
  5. Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, California 94305, USA

    • Steven W. Allen,
    • Roger Blandford,
    • Tuneyoshi Kamae,
    • Ashley King,
    • Grzegorz Madejski,
    • Norbert Werner &
    • Irina Zhuravleva
  6. Department of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, California 94305, USA

    • Steven W. Allen,
    • Roger Blandford,
    • Ashley King,
    • Norbert Werner &
    • Irina Zhuravleva
  7. SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA

    • Steven W. Allen,
    • Roger Blandford &
    • Grzegorz Madejski
  8. Department of Earth and Space Science, Osaka University, Osaka 560-0043, Japan

    • Naohisa Anabuki,
    • Kiyoshi Hayashida,
    • Ryo Nagino,
    • Hiroshi Nakajima &
    • Hiroshi Tsunemi
  9. NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

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    • Tahir Yaqoob
  10. Department of Astronomy, University of Maryland, College Park, Maryland 20742, USA

    • Keith Arnaud,
    • Erin Kara,
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    • Christopher Reynolds
  11. Université de Genève, 1211 Genève 4, Switzerland

    • Marc Audard,
    • Carlo Ferrigno,
    • Stephane Paltani &
    • Martin Pohl
  12. Department of Physics, Ehime University, Ehime 790-8577, Japan

    • Hisamitsu Awaki &
    • Yuichi Terashima
  13. Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397, Japan

    • Magnus Axelsson,
    • Yuichiro Ezoe,
    • Yoshitaka Ishisaki,
    • Takaya Ohashi,
    • Hiromi Seta &
    • Shinya Yamada
  14. Department of Physics, University of Tokyo, Tokyo 113-0033, Japan

    • Aya Bamba &
    • Kazuhiro Nakazawa
  15. Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

    • Marshall Bautz,
    • Esra Bulbul &
    • Eric Miller
  16. Smithsonian Astrophysical Observatory, 60 Garden Street, MS-4, Cambridge, Massachusetts 02138, USA

    • Laura Brenneman,
    • Adam Foster &
    • Randall Smith
  17. Lawrence Livermore National Laboratory, Livermore, California 94550, USA

    • Gregory V. Brown
  18. Institute of Astronomy, Cambridge University, Cambridge CB3 0HA, UK

    • Edward Cackett,
    • Andrew C. Fabian,
    • Ciro Pinto &
    • Helen Russell
  19. Yale Center for Astronomy and Astrophysics, Yale University, New Haven, Connecticut 06520-8121, USA

    • Paolo Coppi,
    • Andrew Szymkowiak &
    • Meg Urry
  20. Department of Physics, University of Durham, Durham DH1 3LE, UK

    • Chris Done
  21. Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Kanagawa 252-5210, Japan

    • Tadayasu Dotani,
    • Ken Ebisawa,
    • Matteo Guainazzi,
    • Kouichi Hagino,
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    • Ryo Iizuka,
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  22. Department of Astronomy, Kyoto University, Kyoto 606-8502, Japan

    • Teruaki Enoto,
    • Shin Mineshige &
    • Yoshihiro Ueda
  23. The Hakubi Center for Advanced Research, Kyoto University, Kyoto 606-8302, Japan

    • Teruaki Enoto
  24. Faculty of Mathematics and Physics, Kanazawa University, Ishikawa 920-1192, Japan

    • Ryuichi Fujimoto,
    • Toshio Murakami &
    • Daisuke Yonetoku
  25. Department of Physical Science, Hiroshima University, Hiroshima 739-8526, Japan

    • Yasushi Fukazawa,
    • Junichiro Katsuta,
    • Takao Kitaguchi,
    • Tsunefumi Mizuno,
    • Masanori Ohno,
    • Hiromitsu Takahashi &
    • Yasuyuki Tanaka
  26. Physics Department, University of Miami, Miami, Florida 33124, USA

    • Massimiliano Galeazzi &
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  27. Department of Astronomy and Physics, Saint Mary’s University, Halifax, Nova Scotia B3H 3C3, Canada

    • Luigi Gallo &
    • Dan Wilkins
  28. Department of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK

    • Poshak Gandhi
  29. IRFU/Service d’Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France

    • Andrea Goldwurm,
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  30. European Space Agency (ESA), European Space Astronomy Centre (ESAC), Madrid, Spain

    • Matteo Guainazzi,
    • Peter Kretschmar &
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  31. Department of Physics and Astronomy, Aichi University of Education, Aichi 448-8543, Japan

    • Yoshito Haba
  32. Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA

    • Kenji Hamaguchi,
    • Ilana Harrus,
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  33. Department of Applied Physics and Electronic Engineering, University of Miyazaki, Miyazaki 889-2192, Japan

    • Isamu Hatsukade,
    • Koji Mori &
    • Makoto Yamauchi
  34. Department of Physics, School of Science and Technology, Kwansei Gakuin University, Hyogo 669-1337, Japan

    • Junko Hiraga
  35. Department of Physics, Rikkyo University, Tokyo 171-8501, Japan

    • Akio Hoshino,
    • Dmitry Khangulyan,
    • Shunji Kitamoto,
    • Shinya Saito &
    • Yasunobu Uchiyama
  36. Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854-8019, USA

    • John Hughes
  37. RIKEN Nishina Center, Saitama 351-0198, Japan

    • Kumi Ishikawa,
    • Toshio Nakano,
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    • Takayuki Yuasa
  38. Faculty of Human Development, Kobe University, Hyogo 657-8501, Japan

    • Masayuki Itoh
  39. Kyushu University, Fukuoka 819-0395, Japan

    • Naoko Iyomoto
  40. Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555, Japan

    • Jun Kataoka
  41. Department of Physics, Chuo University, Tokyo 112-8551, Japan

    • Satoru Katsuda,
    • Yasuharu Sugawara &
    • Yohko Tsuboi
  42. Tsukuba Space Center (TKSC), Japan Aerospace Exploration Agency (JAXA), Ibaraki 305-8505, Japan

    • Madoka Kawaharada
  43. Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan

    • Nobuyuki Kawai,
    • Satoshi Sugita &
    • Yoichi Yatsu
  44. Department of Physics, Toho University, Chiba 274-8510, Japan

    • Tetsu Kitayama
  45. Department of Physics, Tokyo University of Science, Chiba 278-8510, Japan

    • Takayoshi Kohmura
  46. Department of Physics, Kyoto University, Kyoto 606-8502, Japan

    • Katsuji Koyama,
    • Takaaki Tanaka,
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    • Hiroyuki Uchida
  47. Universities Space Research Association, 7178 Columbia Gateway Drive, Columbia, Maryland 21046, USA

    • Hans Krimm
  48. Department of Electronic Information Systems, Shibaura Institute of Technology, Saitama 337-8570, Japan

    • Aya Kubota
  49. Space Telescope Science Institute, Baltimore, Maryland 21218, USA

    • Knox S. Long
  50. European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), 2200 AG Noordwijk, The Netherlands

    • David Lumb &
    • Arvind Parmar
  51. RIKEN, Saitama 351-0198, Japan

    • Kazuo Makishima &
    • Megumi Shidatsu
  52. Kobayashi-Maskawa Institute, Nagoya University, Aichi 464-8602, Japan

    • Hironori Matsumoto
  53. Department of Physics, Tokyo University of Science, Tokyo 162-8601, Japan

    • Kyoko Matsushita &
    • Kosuke Sato
  54. Department of Physics, University of Wisconsin, Madison, Wisconsin 53706, USA

    • Dan McCammon
  55. University of Waterloo, Waterloo, Ontario N2L 3G1, Canada

    • Brian McNamara
  56. Department of Astronomy, University of Michigan, Ann Arbor, Michigan 48109, USA

    • Jon Miller &
    • Abderahmen Zoghbi
  57. Department of Information Science, Faculty of Liberal Arts, Tohoku Gakuin University, Miyagi 981-3193, Japan

    • Hiroshi Murakami
  58. Department of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan

    • Takeshi Nakamori
  59. Department of Teacher Training and School Education, Nara University of Education, Takabatake-cho, Nara 630-8528, Japan

    • Masayoshi Nobukawa
  60. Research Center for Nuclear Physics (Toyonaka), Osaka University, 1-1 Machikaneyama-machi, Toyonaka, Osaka 560-0043, Japan

    • Masaharu Nomachi
  61. NASA/Marshall Space Flight Center, Huntsville, Alabama 35812, USA

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  62. Department of Physics, Faculty of Science, Nara Women’s University, Nara 630-8506, Japan

    • Naomi Ota &
    • Shigeo Yamauchi
  63. Department of Astronomy, Columbia University, New York, New York 10027, USA

    • Frits Paerels
  64. Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada

    • Samar Safi-Harb
  65. Department of Physics and Mathematics, Aoyama Gakuin University, Kanagawa 252-5258, Japan

    • Makoto Sawada &
    • Atsumasa Yoshida
  66. Astronomical Observatory, Jagiellonian University, 30-244 Kraków, Poland

    • Lukasz Stawarz
  67. Institute of Space-Earth Environmental Research, Nagoya University, Aichi 464-8601, Japan

    • Hiroyasu Tajima
  68. Advanced Medical Instrumentation Unit, Okinawa Institute of Science and Technology Graduate University (OIST), Okinawa 904-0495, Japan

    • Shin’ichiro Takeda
  69. Department of Physics, Saitama University, Saitama 338-8570, Japan

    • Makoto Tashiro &
    • Yukikatsu Terada
  70. Science Education, Faculty of Education, Shizuoka University, Shizuoka 422-8529, Japan

    • Hideki Uchiyama
  71. Faculty of Health Sciences, Nihon Fukushi University, Aichi 475-0012, Japan

    • Shin’ichiro Uno
  72. Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA

    • Daniel Wik

Consortia

  1. Hitomi Collaboration

    • Felix Aharonian,
    • Hiroki Akamatsu,
    • Fumie Akimoto,
    • Steven W. Allen,
    • Naohisa Anabuki,
    • Lorella Angelini,
    • Keith Arnaud,
    • Marc Audard,
    • Hisamitsu Awaki,
    • Magnus Axelsson,
    • Aya Bamba,
    • Marshall Bautz,
    • Roger Blandford,
    • Laura Brenneman,
    • Gregory V. Brown,
    • Esra Bulbul,
    • Edward Cackett,
    • Maria Chernyakova,
    • Meng Chiao,
    • Paolo Coppi,
    • Elisa Costantini,
    • Jelle de Plaa,
    • Jan-Willem den Herder,
    • Chris Done,
    • Tadayasu Dotani,
    • Ken Ebisawa,
    • Megan Eckart,
    • Teruaki Enoto,
    • Yuichiro Ezoe,
    • Andrew C. Fabian,
    • Carlo Ferrigno,
    • Adam Foster,
    • Ryuichi Fujimoto,
    • Yasushi Fukazawa,
    • Akihiro Furuzawa,
    • Massimiliano Galeazzi,
    • Luigi Gallo,
    • Poshak Gandhi,
    • Margherita Giustini,
    • Andrea Goldwurm,
    • Liyi Gu,
    • Matteo Guainazzi,
    • Yoshito Haba,
    • Kouichi Hagino,
    • Kenji Hamaguchi,
    • Ilana Harrus,
    • Isamu Hatsukade,
    • Katsuhiro Hayashi,
    • Takayuki Hayashi,
    • Kiyoshi Hayashida,
    • Junko Hiraga,
    • Ann Hornschemeier,
    • Akio Hoshino,
    • John Hughes,
    • Ryo Iizuka,
    • Hajime Inoue,
    • Yoshiyuki Inoue,
    • Kazunori Ishibashi,
    • Manabu Ishida,
    • Kumi Ishikawa,
    • Yoshitaka Ishisaki,
    • Masayuki Itoh,
    • Naoko Iyomoto,
    • Jelle Kaastra,
    • Timothy Kallman,
    • Tuneyoshi Kamae,
    • Erin Kara,
    • Jun Kataoka,
    • Satoru Katsuda,
    • Junichiro Katsuta,
    • Madoka Kawaharada,
    • Nobuyuki Kawai,
    • Richard Kelley,
    • Dmitry Khangulyan,
    • Caroline Kilbourne,
    • Ashley King,
    • Takao Kitaguchi,
    • Shunji Kitamoto,
    • Tetsu Kitayama,
    • Takayoshi Kohmura,
    • Motohide Kokubun,
    • Shu Koyama,
    • Katsuji Koyama,
    • Peter Kretschmar,
    • Hans Krimm,
    • Aya Kubota,
    • Hideyo Kunieda,
    • Philippe Laurent,
    • François Lebrun,
    • Shiu-Hang Lee,
    • Maurice Leutenegger,
    • Olivier Limousin,
    • Michael Loewenstein,
    • Knox S. Long,
    • David Lumb,
    • Grzegorz Madejski,
    • Yoshitomo Maeda,
    • Daniel Maier,
    • Kazuo Makishima,
    • Maxim Markevitch,
    • Hironori Matsumoto,
    • Kyoko Matsushita,
    • Dan McCammon,
    • Brian McNamara,
    • Missagh Mehdipour,
    • Eric Miller,
    • Jon Miller,
    • Shin Mineshige,
    • Kazuhisa Mitsuda,
    • Ikuyuki Mitsuishi,
    • Takuya Miyazawa,
    • Tsunefumi Mizuno,
    • Hideyuki Mori,
    • Koji Mori,
    • Harvey Moseley,
    • Koji Mukai,
    • Hiroshi Murakami,
    • Toshio Murakami,
    • Richard Mushotzky,
    • Ryo Nagino,
    • Takao Nakagawa,
    • Hiroshi Nakajima,
    • Takeshi Nakamori,
    • Toshio Nakano,
    • Shinya Nakashima,
    • Kazuhiro Nakazawa,
    • Masayoshi Nobukawa,
    • Hirofumi Noda,
    • Masaharu Nomachi,
    • Steve O’Dell,
    • Hirokazu Odaka,
    • Takaya Ohashi,
    • Masanori Ohno,
    • Takashi Okajima,
    • Naomi Ota,
    • Masanobu Ozaki,
    • Frits Paerels,
    • Stephane Paltani,
    • Arvind Parmar,
    • Robert Petre,
    • Ciro Pinto,
    • Martin Pohl,
    • F. Scott Porter,
    • Katja Pottschmidt,
    • Brian Ramsey,
    • Christopher Reynolds,
    • Helen Russell,
    • Samar Safi-Harb,
    • Shinya Saito,
    • Kazuhiro Sakai,
    • Hiroaki Sameshima,
    • Goro Sato,
    • Kosuke Sato,
    • Rie Sato,
    • Makoto Sawada,
    • Norbert Schartel,
    • Peter Serlemitsos,
    • Hiromi Seta,
    • Megumi Shidatsu,
    • Aurora Simionescu,
    • Randall Smith,
    • Yang Soong,
    • Lukasz Stawarz,
    • Yasuharu Sugawara,
    • Satoshi Sugita,
    • Andrew Szymkowiak,
    • Hiroyasu Tajima,
    • Hiromitsu Takahashi,
    • Tadayuki Takahashi,
    • Shin’ichiro Takeda,
    • Yoh Takei,
    • Toru Tamagawa,
    • Keisuke Tamura,
    • Takayuki Tamura,
    • Takaaki Tanaka,
    • Yasuo Tanaka,
    • Yasuyuki Tanaka,
    • Makoto Tashiro,
    • Yuzuru Tawara,
    • Yukikatsu Terada,
    • Yuichi Terashima,
    • Francesco Tombesi,
    • Hiroshi Tomida,
    • Yohko Tsuboi,
    • Masahiro Tsujimoto,
    • Hiroshi Tsunemi,
    • Takeshi Tsuru,
    • Hiroyuki Uchida,
    • Hideki Uchiyama,
    • Yasunobu Uchiyama,
    • Shutaro Ueda,
    • Yoshihiro Ueda,
    • Shiro Ueno,
    • Shin’ichiro Uno,
    • Meg Urry,
    • Eugenio Ursino,
    • Cor de Vries,
    • Shin Watanabe,
    • Norbert Werner,
    • Daniel Wik,
    • Dan Wilkins,
    • Brian Williams,
    • Shinya Yamada,
    • Hiroya Yamaguchi,
    • Kazutaka Yamaoka,
    • Noriko Y. Yamasaki,
    • Makoto Yamauchi,
    • Shigeo Yamauchi,
    • Tahir Yaqoob,
    • Yoichi Yatsu,
    • Daisuke Yonetoku,
    • Atsumasa Yoshida,
    • Takayuki Yuasa,
    • Irina Zhuravleva &
    • Abderahmen Zoghbi

Contributions

The science goals of Hitomi (known as ASTRO-H before launch) were discussed and developed over more than 10 years by the ASTRO-H Science Working Group (SWG), all members of which are authors of this manuscript. All the instruments were prepared by joint efforts of the team. Calibration of the Perseus dataset was carried out by members of the SXS team. Data analysis and manuscript preparation were carried out by a small subgroup of authors appointed by the SWG, on the basis of the extensive discussion made in the white paper produced by all SWG members. The manuscript was subject to an internal collaboration-wide review process. All authors reviewed and approved the final version of the manuscript.

Corresponding author

Correspondence to:

Author details

    Extended data figures and tables

    Extended Data Figures

    1. Extended Data Figure 1: SXS spectrum of the full field overlaid with a CCD spectrum of the same region. (84 KB)

      The CCD is the Suzaku X-ray imaging spectrometer (XIS) (red line); the difference in the continuum slope is due to differences in the effective areas of the instruments.

    2. Extended Data Figure 2: The iron line complexes from the outer region compared with best-fit models. (257 KB)

      ac, These have been obtained from various emission-line databases typically used in the literature. The spectra were modelled as a single-temperature, optically thin plasma in collisional ionization equilibrium using either APEC/ATOMDB 3.0.3 (ref 16; red) or SPEX 3.0 (ref. 17; blue). We determined the best-fit model by fitting the Hitomi spectrum from the outer 23 pixels in the energy range 6.4–8 keV, excluding the Fe Heα resonance line and Ni Heα line complex. We obtain consistent best-fit parameters, with both APEC and SPEX predicting a temperature of 4.1 ± 0.1 keV. The iron-to-hydrogen abundances are 0.62 ± 0.02 from APEC and 0.74 ± 0.02 from SPEX, relative to solar values31. The line broadening obtained from APEC, 146 ± 7 km s−1, is smaller than the best-fit SPEX value of 171 ± 7 km s−1, although both values are consistent with the line broadening obtained by fitting a set of Gaussians (the result presented in the main body of the paper). Apart from the Fe Heα w line affected by resonance scattering (a), both emission line models presented here currently have difficulty reproducing the measured Fe Heα intercombination lines (a) as well as the exact position of the Fe Heβ line (c). This motivates the model-independent approach adopted in the manuscript for determining the line widths. Error bars are 1 s.d.

    3. Extended Data Figure 3: The Fe He-α line complex from the central region around the AGN. (116 KB)

      The 5.0–8.5-keV spectrum was modelled with an isothermal, optically thin plasma in collisional ionization equilibrium using either APEC/ATOMDB 3.0.3 (red) or SPEX 3.0 (blue), with an additional power-law component accounting for emission from the central AGN. During the fit we excluded the Fe Heα resonance line because this can be affected by resonant scattering of photons by the intracluster gas in the line of sight. The two spectral codes provide similar results with an average temperature of 3.8 ± 0.1 keV and metallicity consistent with the solar value. We obtain a velocity broadening of 156 ± 12 km s−1 from APEC and 178 ± 9 km s−1 from SPEX. Both models suggest that the resonant line has been suppressed in the central region. Error bars are 1 s.d.

    4. Extended Data Figure 4: Confidence contours for joint fits of redshift z and velocity broadening σv are compared. (182 KB)

      The three line complexes have been fitted independently. The contours are plotted at (68%, two parameters) and (95%). The three fits give consistent redshifts (with the one to which the data were self-calibrated) and broadening.

    5. Extended Data Figure 5: The spatial response of the SXS array. (114 KB)

      The total broadband counts (colour scale) seen across the detector array (left), Fe Heα line counts (centre) that come mostly from the diffuse cluster plasma, and a model response of a point source centred in the pixel coincident with the nucleus of NGC 1275 (right) are compared. Brightness is normalized to the same peak value.

    6. Extended Data Figure 6: The line-of-sight gas velocities overlaid on a deep Chandra image. (321 KB)

      The Chandra image is from ref. 32. The contours increase by a factor of 1.5. The numbers in the larger font indicate the velocity in each region (see also the colour scale). The 90% errors in the figure (numbers in the smaller font) are statistical only; our estimate of the calibration uncertainty in individual pixels is 50 km s−1. Heliocentric correction has been applied. Velocities are shown relative to that of NGC 1275, whose redshift is z = 0.01756 (ref. 33).

    7. Extended Data Figure 7: The SXS field overlaid on the cold gas nebulosity surrounding NGC 1275. (1,199 KB)

      The image shows Hα emission34. The radial velocity along the long northern filament measured from CO data21 decreases, south to north (within the SXS field of view), from about +50 km s−1 to −65 km s−1. This is similar to the trend seen in the SXS velocity map (Extended Data Fig. 6).

    8. Extended Data Figure 8: In-flight spectral resolution of the SXS. (94 KB)

      a, The composite spectrum of all pixels (excluding the calibration pixel) when they were exposed to the 55Fe source on the filter wheel. The blue line shows the expected natural line shape and the red line shows the observed profile (error bars are 1 s.d.). b, A histogram of pixel resolution. N is the number of pixels sharing that resolution.

    Extended Data Tables

    1. Extended Data Table 1: Line energies used in the Gaussian fits (241 KB)

    Additional data