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Oscar Agertz. Profile photo.

Oscar Agertz

Associate Professor / Senior university lecturer / Wallenberg Academy Fellow

Oscar Agertz. Profile photo.

Column density profiles of multiphase gaseous haloes


  • Cameron J. Liang
  • Andrey V. Kravtsov
  • Oscar Agertz

Summary, in English

We analyse circumgalactic medium (CGM) in a suite of high-resolution cosmological re-simulations of a Milky Way size galaxy and show that CGM properties are quite sensitive to details of star formation-feedback loop modelling. The simulation that produces a realistic late-type galaxy, fails to reproduce existing observations of the CGM. In contrast, simulation that does not produce a realistic galaxy has the predicted CGM in better agreement with observations. This illustrates that properties of galaxies and properties of their CGM provide strong complementary constraints on the processes governing galaxy formation. Our simulations predict that column density profiles of ions are well described by an exponential function of projected distance d: N ∝r e-d/hs
. Simulations thus indicate that the sharp drop in absorber detections at larger distances in observations does not correspond to a 'boundary' of an ion, but reflects the underlying steep exponential column density profile. Furthermore, we find that ionization energy of ions is tightly correlated with the scaleheight hs: hs ∝ Eion
0.74. At z ≈ 0, warm gas traced by low-ionization species (e.g. Mg ii and C iv) has hs ≈ 0.03 - 0.07Rvir, while higher ionization species (O vi and Ne viii) have hs ≈ 0.32 - 0.45Rvir. Finally, the scaleheights of ions in our simulations evolve slower than the virial radius for z ≤ 2, but similarly to the halo scale radius, rs. Thus, we suggest that the column density profiles of galaxies at different redshifts should be scaled by rs rather than the halo virial radius.

Publishing year







Monthly Notices of the Royal Astronomical Society





Document type

Journal article


Oxford University Press


  • Cosmology: Theory
  • Galaxies: Evolution
  • Galaxies: Formation
  • Galaxies: Haloes




  • ISSN: 0035-8711