Angular momentum evolution of bulge stars in disc galaxies in NIHAO

Liang Wang, Danail Obreschkow, Claudia Del P. Lagos, Sarah M. Sweet, Deanne Fisher, Karl Glazebrook, Andrea Maccio, Aaron A. Dutton, Xi Kang

    Research output: Contribution to journalArticle

    Abstract

    We study the origin of bulge stars and their angular momentum (AM) evolution in 10 spiral galaxies with baryonic masses above 1010 M in the Numerical Investigation of a Hundred Astrophysical Objects galaxy formation simulations. The simulated galaxies are in good agreement with observations of the relation between the specific AM and mass of the baryonic component and the stellar bulge-to-total ratio (B/T). We divide the star particles at z = 0 into disc and bulge components using a hybrid photometric/kinematic decomposition method that identifies all the central mass above an exponential disc profile as the ‘bulge’. By tracking the bulge star particles back in time, we find that on average 95 per cent of the bulge stars formed in situ, 3 per cent formed ex situ in satellites of the same halo, and only 2 per cent formed ex situ in external galaxies. The evolution of the AM distribution of the bulge stars paints an interesting picture: The higher the final B/T, the more the specific AM remains preserved during the bulge formation. In all cases, bulge stars migrate significantly towards the central region, reducing their average galactocentric radius by roughly a factor 2, independently of the final B/T value. However, in the higher B/T ( 0.2) objects, the velocity of the bulge stars increases and the AM of the bulge is almost conserved, whereas at lower B/T values, the velocity of the bulge stars decreases and the AM of the bulge reduces. The correlation between the evolution of the AM and B/T suggests that bulge formation and disc formation are closely linked and cannot be treated as independent processes.

    Original languageEnglish (US)
    Pages (from-to)5477-5491
    Number of pages15
    JournalMonthly Notices of the Royal Astronomical Society
    Volume482
    Issue number4
    DOIs
    StatePublished - Feb 1 2019

    Fingerprint

    disk galaxies
    angular momentum
    stars
    galaxies
    paints
    galactic evolution
    spiral galaxies
    kinematics
    halos
    astrophysics
    decomposition
    radii
    profiles
    simulation
    in situ

    Keywords

    • Galaxies: bulges
    • Galaxies: evolution
    • Galaxies: formation
    • Galaxies: kinematics and dynamics
    • Galaxies: spiral
    • Methods: numerical

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

    Cite this

    Wang, L., Obreschkow, D., Lagos, C. D. P., Sweet, S. M., Fisher, D., Glazebrook, K., ... Kang, X. (2019). Angular momentum evolution of bulge stars in disc galaxies in NIHAO. Monthly Notices of the Royal Astronomical Society, 482(4), 5477-5491. https://doi.org/10.1093/mnras/sty3010

    Angular momentum evolution of bulge stars in disc galaxies in NIHAO. / Wang, Liang; Obreschkow, Danail; Lagos, Claudia Del P.; Sweet, Sarah M.; Fisher, Deanne; Glazebrook, Karl; Maccio, Andrea; Dutton, Aaron A.; Kang, Xi.

    In: Monthly Notices of the Royal Astronomical Society, Vol. 482, No. 4, 01.02.2019, p. 5477-5491.

    Research output: Contribution to journalArticle

    Wang, L, Obreschkow, D, Lagos, CDP, Sweet, SM, Fisher, D, Glazebrook, K, Maccio, A, Dutton, AA & Kang, X 2019, 'Angular momentum evolution of bulge stars in disc galaxies in NIHAO', Monthly Notices of the Royal Astronomical Society, vol. 482, no. 4, pp. 5477-5491. https://doi.org/10.1093/mnras/sty3010
    Wang L, Obreschkow D, Lagos CDP, Sweet SM, Fisher D, Glazebrook K et al. Angular momentum evolution of bulge stars in disc galaxies in NIHAO. Monthly Notices of the Royal Astronomical Society. 2019 Feb 1;482(4):5477-5491. https://doi.org/10.1093/mnras/sty3010
    Wang, Liang ; Obreschkow, Danail ; Lagos, Claudia Del P. ; Sweet, Sarah M. ; Fisher, Deanne ; Glazebrook, Karl ; Maccio, Andrea ; Dutton, Aaron A. ; Kang, Xi. / Angular momentum evolution of bulge stars in disc galaxies in NIHAO. In: Monthly Notices of the Royal Astronomical Society. 2019 ; Vol. 482, No. 4. pp. 5477-5491.
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    AU - Obreschkow, Danail

    AU - Lagos, Claudia Del P.

    AU - Sweet, Sarah M.

    AU - Fisher, Deanne

    AU - Glazebrook, Karl

    AU - Maccio, Andrea

    AU - Dutton, Aaron A.

    AU - Kang, Xi

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    N2 - We study the origin of bulge stars and their angular momentum (AM) evolution in 10 spiral galaxies with baryonic masses above 1010 M in the Numerical Investigation of a Hundred Astrophysical Objects galaxy formation simulations. The simulated galaxies are in good agreement with observations of the relation between the specific AM and mass of the baryonic component and the stellar bulge-to-total ratio (B/T). We divide the star particles at z = 0 into disc and bulge components using a hybrid photometric/kinematic decomposition method that identifies all the central mass above an exponential disc profile as the ‘bulge’. By tracking the bulge star particles back in time, we find that on average 95 per cent of the bulge stars formed in situ, 3 per cent formed ex situ in satellites of the same halo, and only 2 per cent formed ex situ in external galaxies. The evolution of the AM distribution of the bulge stars paints an interesting picture: The higher the final B/T, the more the specific AM remains preserved during the bulge formation. In all cases, bulge stars migrate significantly towards the central region, reducing their average galactocentric radius by roughly a factor 2, independently of the final B/T value. However, in the higher B/T ( 0.2) objects, the velocity of the bulge stars increases and the AM of the bulge is almost conserved, whereas at lower B/T values, the velocity of the bulge stars decreases and the AM of the bulge reduces. The correlation between the evolution of the AM and B/T suggests that bulge formation and disc formation are closely linked and cannot be treated as independent processes.

    AB - We study the origin of bulge stars and their angular momentum (AM) evolution in 10 spiral galaxies with baryonic masses above 1010 M in the Numerical Investigation of a Hundred Astrophysical Objects galaxy formation simulations. The simulated galaxies are in good agreement with observations of the relation between the specific AM and mass of the baryonic component and the stellar bulge-to-total ratio (B/T). We divide the star particles at z = 0 into disc and bulge components using a hybrid photometric/kinematic decomposition method that identifies all the central mass above an exponential disc profile as the ‘bulge’. By tracking the bulge star particles back in time, we find that on average 95 per cent of the bulge stars formed in situ, 3 per cent formed ex situ in satellites of the same halo, and only 2 per cent formed ex situ in external galaxies. The evolution of the AM distribution of the bulge stars paints an interesting picture: The higher the final B/T, the more the specific AM remains preserved during the bulge formation. In all cases, bulge stars migrate significantly towards the central region, reducing their average galactocentric radius by roughly a factor 2, independently of the final B/T value. However, in the higher B/T ( 0.2) objects, the velocity of the bulge stars increases and the AM of the bulge is almost conserved, whereas at lower B/T values, the velocity of the bulge stars decreases and the AM of the bulge reduces. The correlation between the evolution of the AM and B/T suggests that bulge formation and disc formation are closely linked and cannot be treated as independent processes.

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