X-ray emission from hot gas in galaxy mergers

T. J. Cox, Tiziana Di Matteo, Lars Hernquist, Philip F. Hopkins, Brant Robertson, Volker Springel

Research output: Contribution to journalArticlepeer-review

82 Scopus citations


We examine X-ray emission produced from hot gas during collisions and mergers of disk galaxies. To study this process, we employ simulations that incorporate cosmologically motivated disk-galaxy models and include the effects of radiative cooling, star formation, supernova feedback, and accreting supermassive black holes. We find that during a merger, the colliding gas in the disks is shock heated to X-ray-emitting temperatures. The X-ray luminosity is spatially extended, rises during the initial stages of the merger, and peaks when the galactic centers coalesce. When a physical model for accreting black holes is included, the resulting feedback can drive powerful winds that contribute significantly to the amount and metallicity of hot gas, both of which increase the X-ray luminosity. In terms of their stellar kinematics and structural properties, the merger remnants in our simulations resemble elliptical galaxies. We find that the X-ray luminosities of the remnants with B-band luminosities in the range LB ∼ 1010-10 11 L are consistent with observations, while remnants with smaller or larger masses are under-luminous in X-rays. Moreover, because the majority of the merger remnants are broadly consistent with the observed scaling relations between temperature, B-band luminosity, and X-ray luminosity, we conclude that major mergers are a viable mechanism for producing the X-ray halos of large, luminous elliptical galaxies.

Original languageEnglish (US)
Pages (from-to)692-706
Number of pages15
JournalAstrophysical Journal
Issue number2 I
StatePublished - Jun 1 2006
Externally publishedYes


  • Galaxies: active
  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: interactions
  • Methods: n-body simulations
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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