Simulation Analysis using EAGLE

While I mainly conduct observational studies, analyzing cosmological simulations provide a different perspective of understanding the CGM.  In particular, there exists very few direct observations of gas accretion onto galaxies.  Mapping the CGM using quasar sightline observations is also challenging, because most observations only have one sightline per galaxy.

I analyzed the EAGLE cosmological simulations* to study galaxy gas accretion and the observational signatures of the gas kinematics (Ho, Martin & Turner 2019).  I also analyzed the circumgalactic Mg II gas around low-redshift galaxies in EAGLE; I focused on the Mg II morphological and rotation structures and their dependence on galaxy properties (Ho, Martin & Schaye 2020). 

* EAGLE (Evolution and Assembly of GaLaxies and their Environments):

  • is a suite of of cosmological, hydrodynamical simulations of a standard lambda cold dark matter universe,

  • was run using the smoothed particle hydrodynamics (SPH) code GADGET-3.

  • links: @ Leiden, @ Durham

Related publications in reverse chronological order (also see the abstracts and selected figures below):

  • Ho, S. H., Martin, C. L. & Schaye, J., Morphological and Rotation Structures of Circumgalactic Mg II Gas in the EAGLE Simulation and the Dependence on Galaxy Properties.  2020, ApJ, 904, 76. [ADS] [4-min result video]

  • Ho, S. H., Martin, C. L. & Turner, M. L., How Gas Accretion Feeds Galactic Disks.  2019, ApJ, 875, 54 [abstract/selected figures] [ADS]


How Gas Accretion Feeds Galactic Disks

Stephanie H. Ho, Crystal L. Martin and Monica L. Turner
Published 2019 April 16; The Astrophysical Journal, Volume 875, Issue 1, article id. 54, 19 pp.



Numerous observations indicate that galaxies need a continuous gas supply to fuel star formation and explain the star formation history.  However, direct observational evidence of gas accretion remains rare.  Using the EAGLE cosmological hydrodynamic simulation suite, we study cold gas accretion onto galaxies and the observational signatures of the cold gas kinematics.  For EAGLE galaxies at z = 0.27, we find that cold gas accretes onto galaxies anisotropically with typical inflow speeds between 20 and 60 km/s.  Most of these galaxies have comparable mass inflow rates and star formation rates, implying that the cold inflowing gas plausibly accounts for sustaining the star-forming activities of the galaxies.  As motivation for future work to compare the cold gas kinematics with measurements from quasar sightline observations, we select an EAGLE galaxy with an extended cold gas disk, and we probe the cold gas using mock quasar sightlines.  We demonstrate that by viewing the disk edge on, sightlines at azimuthal angles below 10\deg and impact parameters out to 60 pkpc can detect cold gas that corotates with the galaxy disk.  This example suggests that cold gas disks extending beyond the optical disks possibly explain the sightline observations that detect corotating cold gas near galaxy major axes.


© 2021 by Stephanie Ho. (Last update: January 31, 2021)

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