Temperature structure in the Perseus cluster core observed with Hitomi

Hitomi Collaboration

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The present paper explains the temperature structure of X-ray emitting plasma in the core of the Perseus cluster based on 1.8-20.0 keV data obtained with the Soft X-ray Spectrometer (SXS) on board the Hitomi Observatory. A series of four observations was carried out, with a total effective exposure time of 338 ks that covered a central region of ∼7 in diameter. SXS was operated with an energy resolution of ∼5 eV (full width at half maximum) at 5.9 keV. Not only fine structures of K-shell lines in He-like ions, but also transitions from higher principal quantum numbers were clearly resolved from Si through Fe. That enabled us to perform temperature diagnostics using the line ratios of Si, S, Ar, Ca, and Fe, and to provide the first direct measurement of the excitation temperature and ionization temperature in the Perseus cluster. The observed spectrum is roughly reproduced by a single-temperature thermal plasma model in collisional ionization equilibrium, but detailed line-ratio diagnostics reveal slight deviations from this approximation. In particular, the data exhibit an apparent trend of increasing ionization temperature with the atomic mass, as well as small differences between the ionization and excitation temperatures for Fe, the only element for which both temperatures could be measured. The best-fit two-temperature models suggest a combination of 3 and 5 keV gas, which is consistent with the idea that the observed small deviations from a single-temperature approximation are due to the effects of projecting the known radial temperature gradient in the cluster core along the line of sight. A comparison with the Chandra/ACIS and the XMM-Newton/RGS results, on the other hand, suggests that additional lower-temperature components are present in the intracluster medium (ICM), but not detectable with Hitomi/SXS giving its 1.8-20 keV energy band.

Original languageEnglish
Article numberpsy004
JournalPublications of the Astronomical Society of Japan
Volume70
Issue number2
DOIs
Publication statusPublished - 2018 Mar 1

Fingerprint

temperature
ionization
spectrometer
spectrometers
x rays
deviation
plasma
atomic weights
thermal plasmas
XMM-Newton telescope
approximation
temperature gradient
newton
line of sight
quantum numbers
excitation
energy bands
energy
temperature gradients
observatories

Keywords

  • Galaxies: clusters: individual (Perseus)
  • Methods: observational
  • X-rays: galaxies: clusters

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Temperature structure in the Perseus cluster core observed with Hitomi. / Hitomi Collaboration.

In: Publications of the Astronomical Society of Japan, Vol. 70, No. 2, psy004, 01.03.2018.

Research output: Contribution to journalArticle

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title = "Temperature structure in the Perseus cluster core observed with Hitomi",
abstract = "The present paper explains the temperature structure of X-ray emitting plasma in the core of the Perseus cluster based on 1.8-20.0 keV data obtained with the Soft X-ray Spectrometer (SXS) on board the Hitomi Observatory. A series of four observations was carried out, with a total effective exposure time of 338 ks that covered a central region of ∼7 in diameter. SXS was operated with an energy resolution of ∼5 eV (full width at half maximum) at 5.9 keV. Not only fine structures of K-shell lines in He-like ions, but also transitions from higher principal quantum numbers were clearly resolved from Si through Fe. That enabled us to perform temperature diagnostics using the line ratios of Si, S, Ar, Ca, and Fe, and to provide the first direct measurement of the excitation temperature and ionization temperature in the Perseus cluster. The observed spectrum is roughly reproduced by a single-temperature thermal plasma model in collisional ionization equilibrium, but detailed line-ratio diagnostics reveal slight deviations from this approximation. In particular, the data exhibit an apparent trend of increasing ionization temperature with the atomic mass, as well as small differences between the ionization and excitation temperatures for Fe, the only element for which both temperatures could be measured. The best-fit two-temperature models suggest a combination of 3 and 5 keV gas, which is consistent with the idea that the observed small deviations from a single-temperature approximation are due to the effects of projecting the known radial temperature gradient in the cluster core along the line of sight. A comparison with the Chandra/ACIS and the XMM-Newton/RGS results, on the other hand, suggests that additional lower-temperature components are present in the intracluster medium (ICM), but not detectable with Hitomi/SXS giving its 1.8-20 keV energy band.",
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author = "{Hitomi Collaboration} and Felix Aharonian and Hiroki Akamatsu and Fumie Akimoto and Allen, {Steven W.} and Lorella Angelini and Marc Audard and Hisamitsu Awaki and Magnus Axelsson and Aya Bamba and Bautz, {Marshall W.} and Roger Blandford and Brenneman, {Laura W.} and Brown, {Gregory V.} and Esra Bulbul and Cackett, {Edward M.} and Maria Chernyakova and Chiao, {Meng P.} and Coppi, {Paolo S.} and Elisa Costantini and {De Plaa}, Jelle and {De Vries}, {Cor P.} and {Den Herder}, {Jan Willem} and Chris Done and Tadayasu Dotani and Ken Ebisawa and Eckart, {Megan E.} and Teruaki Enoto and Yuichiro Ezoe and Fabian, {Andrew C.} and Carlo Ferrigno and Foster, {Adam R.} and Ryuichi Fujimoto and Yasushi Fukazawa and Maki Furukawa and Akihiro Furuzawa and Massimiliano Galeazzi and Gallo, {Luigi C.} and Poshak Gandhi and Margherita Giustini and Andrea Goldwurm and Liyi Gu and Matteo Guainazzi and Yoshito Haba and Kouichi Hagino and Kenji Hamaguchi and Harrus, {Ilana M.} and Isamu Hatsukade and Katsuhiro Hayashi and Takayuki Hayashi and Aya Kubota",
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T1 - Temperature structure in the Perseus cluster core observed with Hitomi

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 - Furukawa, Maki

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 - Kubota, Aya

PY - 2018/3/1

Y1 - 2018/3/1

N2 - The present paper explains the temperature structure of X-ray emitting plasma in the core of the Perseus cluster based on 1.8-20.0 keV data obtained with the Soft X-ray Spectrometer (SXS) on board the Hitomi Observatory. A series of four observations was carried out, with a total effective exposure time of 338 ks that covered a central region of ∼7 in diameter. SXS was operated with an energy resolution of ∼5 eV (full width at half maximum) at 5.9 keV. Not only fine structures of K-shell lines in He-like ions, but also transitions from higher principal quantum numbers were clearly resolved from Si through Fe. That enabled us to perform temperature diagnostics using the line ratios of Si, S, Ar, Ca, and Fe, and to provide the first direct measurement of the excitation temperature and ionization temperature in the Perseus cluster. The observed spectrum is roughly reproduced by a single-temperature thermal plasma model in collisional ionization equilibrium, but detailed line-ratio diagnostics reveal slight deviations from this approximation. In particular, the data exhibit an apparent trend of increasing ionization temperature with the atomic mass, as well as small differences between the ionization and excitation temperatures for Fe, the only element for which both temperatures could be measured. The best-fit two-temperature models suggest a combination of 3 and 5 keV gas, which is consistent with the idea that the observed small deviations from a single-temperature approximation are due to the effects of projecting the known radial temperature gradient in the cluster core along the line of sight. A comparison with the Chandra/ACIS and the XMM-Newton/RGS results, on the other hand, suggests that additional lower-temperature components are present in the intracluster medium (ICM), but not detectable with Hitomi/SXS giving its 1.8-20 keV energy band.

AB - The present paper explains the temperature structure of X-ray emitting plasma in the core of the Perseus cluster based on 1.8-20.0 keV data obtained with the Soft X-ray Spectrometer (SXS) on board the Hitomi Observatory. A series of four observations was carried out, with a total effective exposure time of 338 ks that covered a central region of ∼7 in diameter. SXS was operated with an energy resolution of ∼5 eV (full width at half maximum) at 5.9 keV. Not only fine structures of K-shell lines in He-like ions, but also transitions from higher principal quantum numbers were clearly resolved from Si through Fe. That enabled us to perform temperature diagnostics using the line ratios of Si, S, Ar, Ca, and Fe, and to provide the first direct measurement of the excitation temperature and ionization temperature in the Perseus cluster. The observed spectrum is roughly reproduced by a single-temperature thermal plasma model in collisional ionization equilibrium, but detailed line-ratio diagnostics reveal slight deviations from this approximation. In particular, the data exhibit an apparent trend of increasing ionization temperature with the atomic mass, as well as small differences between the ionization and excitation temperatures for Fe, the only element for which both temperatures could be measured. The best-fit two-temperature models suggest a combination of 3 and 5 keV gas, which is consistent with the idea that the observed small deviations from a single-temperature approximation are due to the effects of projecting the known radial temperature gradient in the cluster core along the line of sight. A comparison with the Chandra/ACIS and the XMM-Newton/RGS results, on the other hand, suggests that additional lower-temperature components are present in the intracluster medium (ICM), but not detectable with Hitomi/SXS giving its 1.8-20 keV energy band.

KW - Galaxies: clusters: individual (Perseus)

KW - Methods: observational

KW - X-rays: galaxies: clusters

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