39 research outputs found
An SIDM Solution to the Extreme Diversity of Low-mass Halo Properties
The properties of low-mass dark matter halos appear to be remarkably diverse
relative to predictions of cold, collisionless dark matter, even in the
presence of baryons. We show that self-interacting dark matter can
simultaneously explain two extreme measurements of halo diversity in different
directions -- namely, the rotation curves of low-concentration halos associated
with gas-rich ultra-diffuse galaxies in the field and the inner density profile
of the dense substructure perturbing the strong lens galaxy SDSSJ0946+1006. We
present the first cosmological zoom-in simulation featuring strong dark matter
self-interactions in a galaxy group environment centered on a
host halo. These interactions produce
kiloparsec-scale cores in low-concentration isolated halos, which could host
the ultra-diffuse galaxies, while most surviving subhalos of the group-mass
host are deeply core-collapsed, yielding excellent candidates for the observed
dense strong-lens perturber. Our scenario can be further tested with
observations of galactic systems over a wide mass range.Comment: 10 pages, 6 figure
Strong Dark Matter Self-interactions Diversify Halo Populations Within and Surrounding the Milky Way
We perform a high-resolution cosmological zoom-in simulation of a Milky Way
(MW)-like system, which includes a realistic Large Magellanic Cloud analog,
using a large differential elastic dark matter self-interaction cross section
that reaches at relative
velocities of , motivated by observational
features of dwarf galaxies within and surrounding the MW. We explore the
effects of dark matter self-interactions on satellite, splashback, and isolated
halos through their abundance, central densities, maximum circular velocities,
orbital parameters, and correlations between these variables. We use an
effective constant cross section model to analytically predict the stages of
our simulated halos' gravothermal evolution, demonstrating that deviations from
the collisionless -- relation can be used to select
deeply core-collapsed halos, where is a halo's maximum circular
velocity and is the radius at which it occurs. We predict that a
sizable fraction () of subhalos with masses down to are deeply core-collapsed in our SIDM model. Core-collapsed
systems form of the total isolated halo population down to the
same mass; these isolated, core-collapsed halos would host faint dwarf galaxies
in the field with extremely steep central density profiles reminiscent of the
Tucana dwarf galaxy. Finally, most halos with masses above are core-forming in our simulation. Our study thus demonstrates
how self-interactions diversify halo populations in an
environmentally-dependent fashion within and surrounding MW-mass hosts,
providing a compelling avenue to address the diverse dark matter distributions
of observed dwarf galaxies.Comment: 28 pages, 17 figure
Milky Way satellite census : II. Galaxy–halo connection constraints including the impact of the Large Magellanic Cloud
The population of Milky Way (MW) satellites contains the faintest known galaxies and thus provides essential insight into galaxy formation and dark matter microphysics. Here we combine a model of the galaxy–halo connection with newly derived observational selection functions based on searches for satellites in photometric surveys over nearly the entire high Galactic latitude sky. In particular, we use cosmological zoom-in simulations of MW-like halos that include realistic Large Magellanic Cloud (LMC) analogs to fit the position-dependent MW satellite luminosity function. We report decisive evidence for the statistical impact of the LMC on the MW satellite population due to an estimated 6 ± 2 observed LMC-associated satellites, consistent with the number of LMC satellites inferred from Gaia proper-motion measurements, confirming the predictions of cold dark matter models for the existence of satellites within satellite halos. Moreover, we infer that the LMC fell into the MW within the last 2 Gyr at high confidence. Based on our detailed full-sky modeling, we find that the faintest observed satellites inhabit halos with peak virial masses below 3.2x10 8 M at 95% confidence, and we place the first robust constraints on the fraction of halos that host galaxies in this regime. We predict that the faintest detectable satellites occupy halos with peak virial masses above 10 6 M, highlighting the potential for powerful galaxy formation and dark matter constraints from future dwarf galaxy searches
Modeling the Impact of Baryons on Subhalo Populations with Machine Learning
We identify subhalos in dark matter-only (DMO) zoom-in simulations that are
likely to be disrupted due to baryonic effects by using a random forest
classifier trained on two hydrodynamic simulations of Milky Way (MW)-mass host
halos from the Latte suite of the Feedback in Realistic Environments (FIRE)
project. We train our classifier using five properties of each disrupted and
surviving subhalo: pericentric distance and scale factor at first pericentric
passage after accretion, and scale factor, virial mass, and maximum circular
velocity at accretion. Our five-property classifier identifies disrupted
subhalos in the FIRE simulations with an out-of-bag classification
score. We predict surviving subhalo populations in DMO simulations of the FIRE
host halos, finding excellent agreement with the hydrodynamic results; in
particular, our classifier outperforms DMO zoom-in simulations that include the
gravitational potential of the central galactic disk in each hydrodynamic
simulation, indicating that it captures both the dynamical effects of a central
disk and additional baryonic physics. We also predict surviving subhalo
populations for a suite of DMO zoom-in simulations of MW-mass host halos,
finding that baryons impact each system consistently and that the predicted
amount of subhalo disruption is larger than the host-to-host scatter among the
subhalo populations. Although the small size and specific baryonic physics
prescription of our training set limits the generality of our results, our work
suggests that machine-learning classification algorithms trained on
hydrodynamic zoom-in simulations can efficiently predict realistic subhalo
populations.Comment: 20 pages, 14 figures. Updated to published version. Code available at
https://github.com/ollienad/subhalo_randomfores
Can Neutrino Self-interactions Save Sterile Neutrino Dark Matter?
Sterile neutrinos only interact with the Standard Model through the neutrino
sector, and thus represent a simple dark matter (DM) candidate with many
potential astrophysical and cosmological signatures. Recently, sterile
neutrinos produced through self-interactions of active neutrinos have received
attention as a particle candidate that can yield the entire observed DM relic
abundance without violating the most stringent constraints from X-ray
observations. We examine consistency of this production mechanism with the
abundance of small-scale structure in the universe, as captured by the
population of ultra-faint dwarf galaxies orbiting the Milky Way, and derive a
lower bound on the sterile-neutrino particle mass of keV. Combining
these results with previous limits from particle physics and astrophysics
excludes sterile neutrino DM produced by strong neutrino self-coupling,
mediated by a heavy () scalar particle; however, data
permits sterile-neutrino DM production via a light mediator.Comment: 9 pages, 5 figures, comments are welcom
A Parametric Model for Self-Interacting Dark Matter Halos
We propose a parametric model for studying self-interacting dark matter
(SIDM) halos. The model uses an analytical density profile, calibrated using a
controlled N-body SIDM simulation that covers the entire gravothermal
evolution, including core-forming and -collapsing phases. By normalizing the
calibrated density profile, we obtain a universal description for SIDM halos at
any evolution phase. The model allows us to infer properties of SIDM halos
based on their cold dark matter (CDM) counterparts. As a basic application, we
only require two characteristic parameters of an isolated CDM halo at . We
then extend the model to incorporate effects induced by halo mass changes, such
as major mergers or tidal stripping, making it applicable to both isolated
halos and subhalos. The parametric model is tested and validated using
cosmological zoom-in SIDM simulations available in the literature.Comment: 22 pages, 14 figures, typos fixed, add an appendix for the model
based on the CORE-NFW ("Read") profile; example scripts provided through a
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