Hooks & Bends in the radial acceleration relation: discriminatory tests for dark matter and MOND

Francisco J. Mercado; James S. Bullock; Jorge Moreno; Michael Boylan-Kolchin; Philip F. Hopkins; Andrew Wetzel; Claude André Faucher-Giguère; Jenna Samuel

doi:10.1093/mnras/stae819

Hooks & Bends in the radial acceleration relation: discriminatory tests for dark matter and MOND

Francisco J. Mercado^*, James S. Bullock, Jorge Moreno, Michael Boylan-Kolchin, Philip F. Hopkins, Andrew Wetzel, Claude André Faucher-Giguère, Jenna Samuel

^*Corresponding author for this work

Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

2 Scopus citations

Abstract

The radial acceleration relation (RAR) connects the total gravitational acceleration of a galaxy at a given radius, a_tot(r), with that accounted for by baryons at the same radius, a_bar(r). The shape and tightness of the RAR for rotationally-supported galaxies have characteristics in line with MOdified Newtonian Dynamics (MOND) and can also arise within the cosmological constant + cold dark matter (ΛCDM) paradigm. We use zoom simulations of 20 galaxies with stellar masses of M_∗ ≃ 10^7-11 M_⊙ to study the RAR in the FIRE-2 simulations. We highlight the existence of simulated galaxies with non-monotonic RAR tracks that 'hook' down from the average relation. These hooks are challenging to explain in Modified Inertia theories of MOND, but naturally arise in all of our ΛCDM-simulated galaxies that are dark-matter dominated at small radii and have feedback-induced cores in their dark matter haloes. We show, analytically and numerically, that downward hooks are expected in such cored haloes because they have non-monotonic acceleration profiles. We also extend the relation to accelerations below those traced by disc galaxy rotation curves. In this regime, our simulations exhibit 'bends' off of the MOND-inspired extrapolation of the RAR, which, at large radii, approach a_tot ≈ a_bar/f_b, where f_b is the cosmic baryon fraction. Future efforts to search for these hooks and bends in real galaxies will provide interesting tests for MOND and ΛCDM.

Original language	English (US)
Pages (from-to)	1349-1362
Number of pages	14
Journal	Monthly Notices of the Royal Astronomical Society
Volume	530
Issue number	2
DOIs	https://doi.org/10.1093/mnras/stae819
State	Published - May 1 2024

Funding

FJM is funded by the National Science Foundation (NSF) MSP-Ascend Award AST-2316748. FJM and JSB were supported by NSF grant AST-1910965 and NASA grant 80NSSC22K0827. JM is supported by the Hirsch Foundation. CAFG was supported by NSF through grants AST-2108230 and CAREER award AST-1652522; by NASA through grants 17-ATP17-0067 and 21-ATP21-0036; by STScI through grant HST-GO-16730.016-A; and by CXO through grant TM2-23005X. MBK acknowledges support from NSF CAREER award AST-1752913, NSF grants AST-1910346, and AST-2108962, NASA grant 80NSSC22K0827, and HST-AR-15809, HST-GO-15658, HST-GO-15901, HST-GO-15902, HST-AR-16159, HST-GO-16226, HST-GO-16686, HST-AR-17028, and HST-AR-17043 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. Support for PFH was provided by NSF Research Grants 1911233, 20009234, 2108318, NSF CAREER grant 1455342, NASA grants 80NSSC18K0562, HST-AR-15800. JS is supported by the NSF Astronomy and Astrophysics Postdoctoral Fellowship.

Keywords

cosmology: theory
galaxies: formation

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1093/mnras/stae819

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title = "Hooks & Bends in the radial acceleration relation: discriminatory tests for dark matter and MOND",

abstract = "The radial acceleration relation (RAR) connects the total gravitational acceleration of a galaxy at a given radius, atot(r), with that accounted for by baryons at the same radius, abar(r). The shape and tightness of the RAR for rotationally-supported galaxies have characteristics in line with MOdified Newtonian Dynamics (MOND) and can also arise within the cosmological constant + cold dark matter (ΛCDM) paradigm. We use zoom simulations of 20 galaxies with stellar masses of M∗ ≃ 107-11 M⊙ to study the RAR in the FIRE-2 simulations. We highlight the existence of simulated galaxies with non-monotonic RAR tracks that 'hook' down from the average relation. These hooks are challenging to explain in Modified Inertia theories of MOND, but naturally arise in all of our ΛCDM-simulated galaxies that are dark-matter dominated at small radii and have feedback-induced cores in their dark matter haloes. We show, analytically and numerically, that downward hooks are expected in such cored haloes because they have non-monotonic acceleration profiles. We also extend the relation to accelerations below those traced by disc galaxy rotation curves. In this regime, our simulations exhibit 'bends' off of the MOND-inspired extrapolation of the RAR, which, at large radii, approach atot ≈ abar/fb, where fb is the cosmic baryon fraction. Future efforts to search for these hooks and bends in real galaxies will provide interesting tests for MOND and ΛCDM.",

keywords = "cosmology: theory, galaxies: formation",

author = "Mercado, {Francisco J.} and Bullock, {James S.} and Jorge Moreno and Michael Boylan-Kolchin and Hopkins, {Philip F.} and Andrew Wetzel and Faucher-Gigu{\`e}re, {Claude Andr{\'e}} and Jenna Samuel",

note = "Publisher Copyright: {\textcopyright} 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.",

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month = may,

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doi = "10.1093/mnras/stae819",

language = "English (US)",

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T2 - discriminatory tests for dark matter and MOND

AU - Mercado, Francisco J.

AU - Bullock, James S.

AU - Moreno, Jorge

AU - Boylan-Kolchin, Michael

AU - Hopkins, Philip F.

AU - Wetzel, Andrew

AU - Faucher-Giguère, Claude André

AU - Samuel, Jenna

PY - 2024/5/1

Y1 - 2024/5/1

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AB - The radial acceleration relation (RAR) connects the total gravitational acceleration of a galaxy at a given radius, atot(r), with that accounted for by baryons at the same radius, abar(r). The shape and tightness of the RAR for rotationally-supported galaxies have characteristics in line with MOdified Newtonian Dynamics (MOND) and can also arise within the cosmological constant + cold dark matter (ΛCDM) paradigm. We use zoom simulations of 20 galaxies with stellar masses of M∗ ≃ 107-11 M⊙ to study the RAR in the FIRE-2 simulations. We highlight the existence of simulated galaxies with non-monotonic RAR tracks that 'hook' down from the average relation. These hooks are challenging to explain in Modified Inertia theories of MOND, but naturally arise in all of our ΛCDM-simulated galaxies that are dark-matter dominated at small radii and have feedback-induced cores in their dark matter haloes. We show, analytically and numerically, that downward hooks are expected in such cored haloes because they have non-monotonic acceleration profiles. We also extend the relation to accelerations below those traced by disc galaxy rotation curves. In this regime, our simulations exhibit 'bends' off of the MOND-inspired extrapolation of the RAR, which, at large radii, approach atot ≈ abar/fb, where fb is the cosmic baryon fraction. Future efforts to search for these hooks and bends in real galaxies will provide interesting tests for MOND and ΛCDM.

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Hooks & Bends in the radial acceleration relation: discriminatory tests for dark matter and MOND

Abstract

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