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The effect of feedback on the emission properties of the warm–hot intergalactic medium

Authors

  • M. Roncarelli,

    Corresponding author
    1. Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, I-40127 Bologna, Italy
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  • N. Cappelluti,

    1. INAF – Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna, Italy
    2. University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
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  • S. Borgani,

    1. Università di Trieste, Dipartimento di Fisica, Sezione di Astronomia, Via Tiepolo 11, I-34143 Trieste, Italy
    2. INAF – Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34143 Trieste, Italy
    3. INFN, Sezione di Trieste, Via Valerio 2, I-34127 Trieste, Italy
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  • E. Branchini,

    1. Università degli Studi ‘Roma Tre’, Dipartimento di Fisica ‘E. Amaldi’, via della Vasca Navale 84, I-00146 Roma, Italy
    2. INFN, Sezione di ‘Roma Tre’, via della Vasca Navale 84, I-00146 Roma, Italy
    3. INAF, Osservatorio Astronomico di Brera, via Brera 28, I-20121 Milano, Italy
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  • L. Moscardini

    1. Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, I-40127 Bologna, Italy
    2. INAF – Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna, Italy
    3. INFN, Sezione di Bologna, viale Berti Pichat 6/2, I-40127 Bologna, Italy
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E-mail: mauro.roncarelli@unibo.it

ABSTRACT

At present, 30–40 per cent of the baryons in the local Universe is still undetected. According to theoretical predictions, this gas should reside in filaments filling the large-scale structure (LSS) in the form of a warm–hot intergalactic medium (WHIM), at temperatures 105–107 K, thus emitting in the soft X-ray energies via free–free interaction and line emission from heavy elements. In this work, we characterize the properties of the X-ray emission of the WHIM, and the LSS in general, focusing on the influence of different physical mechanisms, namely galactic winds (GWs), black hole feedback and star formation, and providing estimates of possible observational constraints. To this purpose, we use a set of cosmological hydrodynamical simulations that include a self-consistent treatment of star formation and chemical enrichment of the intergalactic medium, which allows us to follow the evolution of different metal species. We construct a set of simulated light cones to make predictions of the emission in the 0.3–10 keV energy range. We obtain that GWs increase the emission of both galaxy clusters and WHIM by a factor of 2. The amount of oxygen at average temperature and, consequently, the amount of expected bright O vii and O viii lines are increased by a factor of 3 due to GWs and by 20 per cent when assuming a top-heavy initial mass function. We compare our results with current observational constraints and find that the emission from faint groups and WHIM should account for half to all of the unresolved X-ray background in the 1–2 keV band.

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