CGM properties in VELA and NIHAO simulations; the OVI ionization mechanism

Dependence on redshift, halo mass, and radius

S. Roca-Fàbrega, A. Dekel, Y. Faerman, O. Gnat, C. Strawn, D. Ceverino, J. Primack, Andrea Maccio, A. A. Dutton, J. X. Prochaska, J. Stern

    Research output: Contribution to journalArticle

    Abstract

    We study the components of cool and warm/hot gas in the circumgalactic medium (CGM) of simulated galaxies and address the relative production of OVI by photoionization versus collisional ionization, as a function of halo mass, redshift, and distance from the galaxy halo centre. This is done utilizing two different suites of zoom-in hydro-cosmological simulations, VELA (6 haloes; z > 1) and NIHAO (18 haloes; to z = 0), which provide a broad theoretical basis because they use different codes and physical recipes for star formation and feedback. In all haloes studied in this work, we find that collisional ionization by thermal electrons dominates at high redshift, while photoionization of cool or warm gas by the metagalactic radiation takes over near z ∼ 2. In haloes of ∼1012 M and above, collisions become important again at z < 0.5, while photoionization remains significant down to z = 0 for less massive haloes. In haloes with Mv > 3 × 1011 M, at z ∼ 0 most of the photoionized OVI is in a warm, not cool, gas phase (T 3 × 105 K). We also find that collisions are dominant in the central regions of haloes, while photoionization is more significant at the outskirts, around Rv, even in massive haloes. This too may be explained by the presence of warm gas or, in lower mass haloes, by cool gas inflows.

    Original languageEnglish (US)
    Pages (from-to)3625-3645
    Number of pages21
    JournalMonthly Notices of the Royal Astronomical Society
    Volume484
    Issue number3
    DOIs
    StatePublished - Apr 11 2019

    Fingerprint

    halos
    ionization
    radii
    gas
    simulation
    collision
    photoionization
    gases
    inflow
    galaxies
    collisions
    electron
    high temperature gases
    star formation
    vapor phases
    radiation
    electrons

    Keywords

    • Galaxies: evolution
    • Galaxies: formation
    • Methods: numerical

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

    Cite this

    CGM properties in VELA and NIHAO simulations; the OVI ionization mechanism : Dependence on redshift, halo mass, and radius. / Roca-Fàbrega, S.; Dekel, A.; Faerman, Y.; Gnat, O.; Strawn, C.; Ceverino, D.; Primack, J.; Maccio, Andrea; Dutton, A. A.; Prochaska, J. X.; Stern, J.

    In: Monthly Notices of the Royal Astronomical Society, Vol. 484, No. 3, 11.04.2019, p. 3625-3645.

    Research output: Contribution to journalArticle

    Roca-Fàbrega, S, Dekel, A, Faerman, Y, Gnat, O, Strawn, C, Ceverino, D, Primack, J, Maccio, A, Dutton, AA, Prochaska, JX & Stern, J 2019, 'CGM properties in VELA and NIHAO simulations; the OVI ionization mechanism: Dependence on redshift, halo mass, and radius', Monthly Notices of the Royal Astronomical Society, vol. 484, no. 3, pp. 3625-3645. https://doi.org/10.1093/mnras/stz063
    Roca-Fàbrega, S. ; Dekel, A. ; Faerman, Y. ; Gnat, O. ; Strawn, C. ; Ceverino, D. ; Primack, J. ; Maccio, Andrea ; Dutton, A. A. ; Prochaska, J. X. ; Stern, J. / CGM properties in VELA and NIHAO simulations; the OVI ionization mechanism : Dependence on redshift, halo mass, and radius. In: Monthly Notices of the Royal Astronomical Society. 2019 ; Vol. 484, No. 3. pp. 3625-3645.
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    AU - Dekel, A.

    AU - Faerman, Y.

    AU - Gnat, O.

    AU - Strawn, C.

    AU - Ceverino, D.

    AU - Primack, J.

    AU - Maccio, Andrea

    AU - Dutton, A. A.

    AU - Prochaska, J. X.

    AU - Stern, J.

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    AB - We study the components of cool and warm/hot gas in the circumgalactic medium (CGM) of simulated galaxies and address the relative production of OVI by photoionization versus collisional ionization, as a function of halo mass, redshift, and distance from the galaxy halo centre. This is done utilizing two different suites of zoom-in hydro-cosmological simulations, VELA (6 haloes; z > 1) and NIHAO (18 haloes; to z = 0), which provide a broad theoretical basis because they use different codes and physical recipes for star formation and feedback. In all haloes studied in this work, we find that collisional ionization by thermal electrons dominates at high redshift, while photoionization of cool or warm gas by the metagalactic radiation takes over near z ∼ 2. In haloes of ∼1012 M and above, collisions become important again at z < 0.5, while photoionization remains significant down to z = 0 for less massive haloes. In haloes with Mv > 3 × 1011 M, at z ∼ 0 most of the photoionized OVI is in a warm, not cool, gas phase (T 3 × 105 K). We also find that collisions are dominant in the central regions of haloes, while photoionization is more significant at the outskirts, around Rv, even in massive haloes. This too may be explained by the presence of warm gas or, in lower mass haloes, by cool gas inflows.

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