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.",
    keywords = "Galaxies: clusters: individual (Perseus), Methods: observational, X-rays: galaxies: clusters",
    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 Jun Kataoka",
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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 - Kataoka, Jun

    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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