395 research outputs found
Sloshing of Galaxy Cluster Core Plasma in the Presence of Self-Interacting Dark Matter
The "sloshing" of the cold gas in the cores of relaxed clusters of galaxies
is a widespread phenomenon, evidenced by the presence of spiral-shaped "cold
fronts" in X-ray observations of these systems. In simulations, these flows of
cold gas readily form by interactions of the cluster core with small
subclusters, due to a separation of the cold gas from the dark matter (DM), due
to their markedly different collisionalities. In this work, we use numerical
simulations to investigate the effects of increasing the DM collisionality on
sloshing cold fronts in a cool-core cluster. For clusters in isolation, the
formation of a flat DM core via self-interactions results in modest adiabatic
expansion and cooling of the core gas. In merger simulations, cold fronts form
in the same manner as in previous simulations, but the flattened potential in
the core region enables the gas to expand to larger radii in the initial
stages. Upon infall, the subcluster's DM mass decreases via collisions,
reducing its influence on the core. Thus, the sloshing gas moves slower,
inhibiting the growth of fluid instabilities relative to simulations where the
DM cross section is zero. This also inhibits turbulent mixing and the increase
in entropy that would otherwise result. For values of the cross section
, subclusters do not survive as self-gravitating structures for
more than two core passages. Additionally, separations between the peaks in the
X-ray emissivity and thermal Sunyaev-Zeldovich effect signals during sloshing
may place constraints on DM self-interactions.Comment: 20 pages, 14 figures, submitted to Ap
The structure and assembly history of cluster-size haloes in Self-Interacting Dark Matter
We perform dark-matter-only simulations of 28 relaxed massive cluster-sized
haloes for Cold Dark Matter (CDM) and Self-Interacting Dark Matter (SIDM)
models, to study structural differences between the models at large radii,
where the impact of baryonic physics is expected to be very limited. We find
that the distributions for the radial profiles of the density, ellipsoidal axis
ratios, and velocity anisotropies () of the haloes differ considerably
between the models (at the level), even at of the
virial radius, if the self-scattering cross section is cm
gr. Direct comparison with observationally inferred density profiles
disfavours SIDM for cm gr, but in an intermediate
radial range ( of the virial radius), where the impact of baryonic
physics is uncertain. At this level of the cross section, we find a narrower
distribution in SIDM, clearly skewed towards isotropic orbits, with no
SIDM (90\% of CDM) haloes having at of the virial radius. We
estimate that with an observational sample of (
M) relaxed clusters, can potentially be used to put competitive
constraints on SIDM, once observational uncertainties improve by a factor of a
few. We study the suppression of the memory of halo assembly history in SIDM
clusters. For cm gr, we find that this happens
only in the central halo regions ( of the scale radius of the halo),
and only for haloes that assembled their mass within this region earlier than a
formation redshift . Otherwise, the memory of assembly remains and is
reflected in ways similar to CDM, albeit with weaker trends.Comment: 15 pages, 15 figures. Submitted to MNRAS. Revisions: added new figure
with an observational comparison of density profiles, improvements and
corrections to the section on velocity anisotropie
Scattering, Damping, and Acoustic Oscillations: Simulating the Structure of Dark Matter Halos with Relativistic Force Carriers
We demonstrate that self-interacting dark matter models with interactions
mediated by light particles can have significant deviations in the matter
power-spectrum and detailed structure of galactic halos when compared to a
standard cold dark matter scenario. While these deviations can take the form of
suppression of small scale structure that are in some ways similar to that of
warm dark matter, the self-interacting models have a much wider range of
possible phenomenology. A long-range force in the dark matter can introduce
multiple scales to the initial power spectrum, in the form of dark acoustic
oscillations and an exponential cut-off in the power spectrum. Using
simulations we show that the impact of these scales can remain observationally
relevant up to the present day. Furthermore, the self-interaction can continue
to modify the small-scale structure of the dark matter halos, reducing their
central densities and creating a dark matter core. The resulting phenomenology
is unique to this type of models.Comment: 23 pages, 11 figure
Enhanced tidal stripping of satellites in the galactic halo from dark matter self-interactions
We investigate the effects of self-interacting dark matter (SIDM) on the
tidal stripping and evaporation of satellite galaxies in a Milky Way-like host.
We use a suite of five zoom-in, dark-matter-only simulations, two with
velocity-independent SIDM cross sections, two with velocity-dependent SIDM
cross sections, and one cold dark matter simulation for comparison. After
carefully assigning stellar mass to satellites at infall, we find that stars
are stripped at a higher rate in SIDM than in CDM. In contrast, the total bound
dark matter mass loss rate is minimally affected, with subhalo evaporation
having negligible effects on satellites for viable SIDM models. Centrally
located stars in SIDM haloes disperse out to larger radii as cores grow.
Consequently, the half-light radius of satellites increases, stars become more
vulnerable to tidal stripping, and the stellar mass function is suppressed. We
find that the ratio of core radius to tidal radius accurately predicts the
relative strength of enhanced SIDM stellar stripping. Velocity-independent SIDM
models show a modest increase in the stellar stripping effect with satellite
mass, whereas velocity-dependent SIDM models show a large increase in this
effect towards lower masses, making observations of ultra-faint dwarfs prime
targets for distinguishing between and constraining SIDM models. Due to small
cores in the largest satellites of velocity-dependent SIDM, no identifiable
imprint is left on the all-sky properties of the stellar halo. While our
results focus on SIDM, the main physical mechanism of enhanced tidal stripping
of stars apply similarly to satellites with cores formed via other means.Comment: 19 pages, 18 figures, Accepted by MNRA
Gravitational Lensing and the Power Spectrum of Dark Matter Substructure: Insights from the ETHOS N-body Simulations
Strong gravitational lensing has been identified as a promising astrophysical
probe to study the particle nature of dark matter. In this paper we present a
detailed study of the power spectrum of the projected mass density
(convergence) field of substructure in a Milky Way-sized halo. This power
spectrum has been suggested as a key observable that can be extracted from
strongly lensed images and yield important clues about the matter distribution
within the lens galaxy. We use two different -body simulations from the
ETHOS framework: one with cold dark matter and another with self-interacting
dark matter and a cutoff in the initial power spectrum. Despite earlier works
that identified kpc as the most promising scales to
learn about the particle nature of dark matter we find that even at lower
wavenumbers - which are actually within reach of observations in the near
future - we can gain important information about dark matter. Comparing the
amplitude and slope of the power spectrum on scales kpc from lenses at different redshifts can help us distinguish between
cold dark matter and other exotic dark matter scenarios that alter the
abundance and central densities of subhalos. Furthermore, by considering the
contribution of different mass bins to the power spectrum we find that subhalos
in the mass range M are on average the largest
contributors to the power spectrum signal on scales kpc, despite the numerous subhalos with masses M in
a typical lens galaxy. Finally, by comparing the power spectra obtained from
the subhalo catalogs to those from the particle data in the simulation
snapshots we find that the seemingly-too-simple halo model is in fact a fairly
good approximation to the much more complex array of substructure in the lens.Comment: 13 pages + appendices, 7 figure
Sustainability at UAM-Azcapotzalco for academic programs with virtual classroom methodologies
Abstract. The post-pandemic educational processes due to Covid-19 have generated an interest in structuring new learning trends. The Autonomous Metropolitan University (UAM) Azcapotzalco identified the use of methodologies with digital tools known as virtual classrooms during the pandemic to continue academic activities. These digital tools are still being used in different academic programs, including undergraduate and postgraduate programs to promote the professionalism of the university community. This paper provides a general breakdown of the virtual classroom format as a methodology in the teaching-learning processes to improve the educational environment at a higher level and ensure educational sustainability through the innovation of new technologies and digital tools that can be applied at a national and international level. The expected results from this methodology are part of an improvement process aimed at generating academic programs in virtual environments to enrich the educational models at higher and postgraduate levels and creating collaborative groups within each teaching department that can be extrapolated to a unit or campus level.Keyword:Sustainable Academic, Educational Methodology, Educational Process, Virtual Classroom
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