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Probing the CGM of low-redshift dwarf galaxies using FIRE simulations

Li, Fei and Rahman, Mubdi and Murray, Norman and Hafen, Zachary and Faucher-Giguère, Claude-André and Stern, Jonathan and Hummels, Cameron B. and Hopkins, Philip F. and El-Badry, Kareem and Kereš, Dušan (2021) Probing the CGM of low-redshift dwarf galaxies using FIRE simulations. Monthly Notices of the Royal Astronomical Society, 500 (1). pp. 1038-1053. ISSN 0035-8711.

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Observations of ultraviolet (UV) metal absorption lines have provided insight into the structure and composition of the circumgalactic medium (CGM) around galaxies. We compare these observations with the low-redshift (z ≤ 0.3) CGM around dwarf galaxies in high-resolution cosmological zoom-in runs in the FIRE-2 (Feedback In Realistic Environments) simulation suite. We select simulated galaxies that match the halo mass, stellar mass, and redshift of the observed samples. We produce absorption measurements using TRIDENT for UV transitions of C IV, O VI, Mg II, and Si III. The FIRE equivalent width (EW) distributions and covering fractions for the C IV ion are broadly consistent with observations inside 0.5R_(vir), but are underpredicted for O VI, Mg II, and Si III. The absorption strengths of the ions in the CGM are moderately correlated with the masses and star formation activity of the galaxies. The correlation strengths increase with the ionization potential of the ions. The structure and composition of the gas from the simulations exhibit three zones around dwarf galaxies characterized by distinct ion column densities: the discy interstellar medium, the inner CGM (the wind-dominated regime), and the outer CGM (the IGM accretion-dominated regime). We find that the outer CGM in the simulations is nearly but not quite supported by thermal pressure, so it is not in hydrostatic equilibrium, resulting in halo-scale bulk inflow and outflow motions. The net gas inflow rates are comparable to the star formation rate of the galaxy, but the bulk inflow and outflow rates are greater by an order of magnitude, with velocities comparable to the virial velocity of the halo. These roughly virial velocities (⁠∼100 km s⁻¹⁠) produce large EWs in the simulations. This supports a picture for dwarf galaxies in which the dynamics of the CGM at large scales are coupled to the small-scale star formation activity near the centre of their haloes.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemGIZMO Code ItemAdditional Data
Rahman, Mubdi0000-0003-1842-6096
Hafen, Zachary0000-0001-7326-1736
Faucher-Giguère, Claude-André0000-0002-4900-6628
Stern, Jonathan0000-0002-7541-9565
Hummels, Cameron B.0000-0002-3817-8133
Hopkins, Philip F.0000-0003-3729-1684
El-Badry, Kareem0000-0002-6871-1752
Kereš, Dušan0000-0002-1666-7067
Additional Information:© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 October 13. Received 2020 September 26; in original form 2020 June 10. We thank Lauren Corlies for her help in using TRIDENT. FL thanks Gunjan Lakhlani for sharing the routines to calculate the dynamical time. We benefitted from discussions with Bili Dong and Maan H. Hani. The analysis on the FIRE simulation data were run on XSEDE computational resources (allocations TG-AST120025 and TG-AST120023) and on the CITA compute cluster Sunnyvale. This research was enabled in part by support provided by SciNet ( and Compute Canada =" Computations were performed on the Niagara supercomputer (Ponce et al. 2019; Loken et al. 2010) at the SciNet HPC Consortium. SciNet is funded by: the Canada Foundation for Innovation; the Government of Ontario; Ontario Research Fund - Research Excellence; and the University of Toronto. The data used in this work were, in part, hosted on facilities supported by the Scientific Computing Core at the Flatiron Institute, a division of the Simons Foundation. This work was performed in part at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611. CAFG was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522, by NASA through grant 17-ATP17-0067, by STScI through grants HST-GO-14681.011, HST-GO-14268.022-A, and HST-AR-14293.001-A, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. Software: SCIPY,3 NUMPY4 (van der Walt, Colbert & Varoquaux 2011), MATPLOTLIB5 (Hunter 2007), MPI4PY6 (Dalcín, Paz & Storti 2005), TRIDENT7 (Hummels et al. 2017), and YT8 (Turk et al. 2011). DATA AVAILABILITY. The data supporting the plots within this article are available on reasonable request to the corresponding author. A public version of the GIZMO code is available at Additional data including simulation snapshots, initial conditions, and derived data products are available at
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Canadian Institute for Theoretical AstrophysicsUNSPECIFIED
Canada Foundation for InnovationUNSPECIFIED
Government of OntarioUNSPECIFIED
Ontario Research Fund-Research ExcellenceUNSPECIFIED
University of TorontoUNSPECIFIED
Simons FoundationUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
Subject Keywords:galaxies: dwarf, galaxies: evolution, quasars: absorption lines
Issue or Number:1
Record Number:CaltechAUTHORS:20210114-164620520
Persistent URL:
Official Citation:Fei Li, Mubdi Rahman, Norman Murray, Zachary Hafen, Claude-André Faucher-Giguère, Jonathan Stern, Cameron B Hummels, Philip F Hopkins, Kareem El-Badry, Dušan Kereš, Probing the CGM of low-redshift dwarf galaxies using FIRE simulations, Monthly Notices of the Royal Astronomical Society, Volume 500, Issue 1, January 2021, Pages 1038–1053,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107501
Deposited By: George Porter
Deposited On:15 Jan 2021 18:16
Last Modified:15 Jan 2021 18:16

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