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Constraining dynamical dark energy models through the abundance of high-redshift supermassive black holes

Authors

  • A. Lamastra,

    Corresponding author
    1. INAF – Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monteporzio, Italy
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  • N. Menci,

    1. INAF – Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monteporzio, Italy
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  • F. Fiore,

    1. INAF – Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monteporzio, Italy
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  • C. Di Porto,

    1. Dipartimento di Fisica E. Amaldi, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
    2. Institut für Theoretische Physik, Universität Heidelber, Philosophenweg 16, D-69120 Heidelberg, Germany
    3. INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, Bologna 40127, Italy
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  • L. Amendola

    1. Institut für Theoretische Physik, Universität Heidelber, Philosophenweg 16, D-69120 Heidelberg, Germany
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E-mail: lamastra@mporzio.astro.it

ABSTRACT

We compute the number density of massive black holes (BHs) at the centre of galaxies at z= 6 in different dynamical dark energy (DDE) cosmologies, and compare it with existing observational lower limits, to derive constraints on the evolution of the dark energy equation of state parameter w. Our approach only assumes the canonical scenario for structure formation from the collapse of overdense regions of the dark-matter-dominated primordial density field on progressively larger scales; the BH accretion and merging rate have been maximized in the computation so as to obtain robust constraints on w and on its look-back time derivative wa. Our results provide independent constraints complementary to those obtained by combining supernovae, cosmic microwave background and baryonic acoustic oscillations, while the latter concern combinations of w0 and wa leaving the time evolution of the state parameter wa highly unconstrained, the BH abundance mainly provide upper limits on wa, only weakly depending on w0. Combined with the existing constraints, our results significantly restrict the allowed region in DDE parameter space, ruling out DDE models not providing cosmic time and fast growth factor large enough to allow for the building up of the observed abundance of BHs; in particular, models with −1.2 ≤w0≤−1 and positive redshift evolution wa≳ 0.8 – completely consistent with previous constraints – are strongly disfavoured by our independent constraints from BH abundance. Such range of parameters corresponds to ‘quintom’ DDE models, with w crossing −1 starting from larger values.

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