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Planes of satellites around Milky Way/M31-mass galaxies in the FIRE simulations and comparisons with the Local Group

Samuel, Jenna and Wetzel, Andrew and Chapman, Sierra and Tollerud, Erik and Hopkins, Philip F. and Boylan-Kolchin, Michael and Bailin, Jeremy and Faucher-Giguère, Claude-André (2021) Planes of satellites around Milky Way/M31-mass galaxies in the FIRE simulations and comparisons with the Local Group. Monthly Notices of the Royal Astronomical Society, 504 (1). pp. 1379-1397. ISSN 0035-8711. doi:10.1093/mnras/stab955.

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We examine the prevalence, longevity, and causes of planes of satellite dwarf galaxies, as observed in the Local Group. We use 14 Milky Way/Andromeda-(MW/M31) mass host galaxies from the Feedback In Realistic Environments-2 simulations. We select the 14 most massive satellites by stellar mass within d_(host) ≤ 300kpc of each host and correct for incompleteness from the foreground galactic disc when comparing to the MW. We find that MW-like planes as spatially thin and/or kinematically coherent as observed are uncommon, but they do exist in our simulations. Spatially thin planes occur in 1–2 per cent of snapshots during z = 0−0.2, and kinematically coherent planes occur in 5 per cent of snapshots. These planes are generally transient, surviving for <500 Myr. However, if we select hosts with a Large Magellanic Cloud-like satellite near first pericentre, the fraction of snapshots with MW-like planes increases dramatically to 7–16 per cent, with lifetimes of  0.7–1 Gyr, likely because of group accretion of satellites. We find that M31’s satellite distribution is much more common: M31’s satellites lie within ∼1σ of the simulation median for every plane metric we consider. We find no significant difference in average satellite planarity for isolated hosts versus hosts in LG-like pairs. Baryonic and dark matter-only simulations exhibit similar levels of planarity, even though baryonic subhaloes are less centrally concentrated within their host haloes. We conclude that planes of satellites are not a strong challenge to ΛCDM cosmology.

Item Type:Article
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URLURL TypeDescription Paper ItemSoftware Packages ItemSoftware Packages ItemSoftware Packages
Samuel, Jenna0000-0002-8429-4100
Wetzel, Andrew0000-0003-0603-8942
Tollerud, Erik0000-0002-9599-310X
Hopkins, Philip F.0000-0003-3729-1684
Boylan-Kolchin, Michael0000-0002-9604-343X
Faucher-Giguère, Claude-André0000-0002-4900-6628
Additional Information:© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 March 29. Received 2021 March 12; in original form 2020 October 14. Published: 08 April 2021. We thank Marcel Pawlowski for insightful comments and discussion that improved this manuscript. This research used ASTROPY,3 a community-developed core PYTHON package for Astronomy (Astropy Collaboration 2013, 2018), the IPYTHON package (Pérez & Granger 2007), NUMPY (Harris et al. 2020), SCIPY (Jones et al. 2001), NUMBA (Lam, Pitrou & Seibert 2015), and MATPLOTLIB, a PYTHON library for publication quality graphics (Hunter 2007). JS, AW, and SC received support from NASA through ATP grants 80NSSC18K1097 and 80NSSC20K0513; HST grants GO-14734, AR-15057, AR-15809, and GO-15902 from the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555; a Scialog Award from the Heising-Simons Foundation; and a Hellman Fellowship. We performed this work in part at the Aspen Center for Physics, supported by NSF grant PHY-1607611, and at the KITP, supported NSF grant PHY-1748958. PFH was provided by an Alfred P. Sloan Foundation Fellowship, NSF grant #1715847 and CAREER grant #1455342, and NASA grants NNX15AT06G, JPL 1589742, 17-ATP17-0214. MBK acknowledges support from NSF CAREER award AST-1752913, NSF grant AST-1910346, NASA grants NNX17AG29G, and HST-AR-15006, HST-AR-15809, HST-GO-15658, HST-GO-15901, and HST-GO-15902 from STScI. CAFG was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522, by NASA through grant 17-ATP17-0067, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. We ran simulations using the Extreme Science and Engineering Discovery Environment (XSEDE) supported by NSF grant ACI-1548562, Blue Waters via allocation PRAC NSF.1713353 supported by the NSF, and NASA’s HEC Program through the NAS Division at Ames Research Center. Data Availability: Full simulation snapshots at z = 0 are available for m12i, m12f, and m12m at The publicly available software packages used to analyse these data are available at,, and
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
NASA Hubble FellowshipGO-14734
NASA Hubble FellowshipAR-15057
NASA Hubble FellowshipAR-15809
NASA Hubble FellowshipGO-15902
Heising-Simons FoundationUNSPECIFIED
Hellman FellowshipUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
Subject Keywords:methods: numerical – galaxies: dwarf – galaxies: formation – Local Group
Issue or Number:1
Record Number:CaltechAUTHORS:20210630-162633099
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Official Citation:Jenna Samuel, Andrew Wetzel, Sierra Chapman, Erik Tollerud, Philip F Hopkins, Michael Boylan-Kolchin, Jeremy Bailin, Claude-André Faucher-Giguère, Planes of satellites around Milky Way/M31-mass galaxies in the FIRE simulations and comparisons with the Local Group, Monthly Notices of the Royal Astronomical Society, Volume 504, Issue 1, June 2021, Pages 1379–1397,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109673
Deposited By: Tony Diaz
Deposited On:30 Jun 2021 18:19
Last Modified:06 Jul 2021 19:42

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