Bulletin of the American Physical Society
2023 APS April Meeting
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session C14: Dark Matter Astrophysics |
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Sponsoring Units: DAP Chair: Kevork Abazajian, University of California, Irvine Room: Marquette V - 2nd Floor |
Saturday, April 15, 2023 1:30PM - 1:42PM |
C14.00001: Constraining Dark Matter Annihilation in Early Matter Dominated Era Cosmologies Using the Global 21 cm Absorption Signal Hwan Bae, Sten Delos, Adrienne L Erickcek Although standard cosmology assumes that relativistic particles dominate the energy density of the Universe quickly after inflation, a variety of well-motivated scenarios predict an early matter dominated era (EMDE) before the onset of the radiation dominated era (RDE). Subhorizon dark matter (DM) density perturbations grow faster during an EMDE than during an RDE, leading to an increased abundance of microhalos that form far earlier than in standard models of strucuture formation. This enhancement of small-scale structure boosts the DM annihilation rate, and we discuss how to compute boost factors for cosmologies with EMDEs. Since the first halos form by direct collapse, we assign a halo to each local maxima that collapses in the dark matter density field following an EMDE, and we predict the halo's central density profile from the properties of the associated maximum. The boost factor due to EMDE cosmologies can be several orders of magnitude greater than in standard cosmology, and the additional energy injected from annihilating DM increases the temperature of the intergalactic medium, TK. During the Dark Ages the sky- averaged (global) 21 cm signal is highly sensitive to TK, and we use forecasts of the global 21 cm signal to present bounds on the DM annihilation cross section in cosmologies with EMDEs. |
Saturday, April 15, 2023 1:42PM - 1:54PM |
C14.00002: UltraLight Dark Matter Dynamics in the Language of Eigenstates Jovana Zagorac, Nikhil Padmanabhan, Richard Easther, Emily Kendall, Isabel S Sands Self-gravitating quantum matter may exist in a wide range of cosmological and astrophysical settings: from the very early universe through to present-day boson stars. Such quantum matter arises in UltraLight Dark Matter (ULDM): an exciting axion-like particle candidate which keeps the successes of CDM on large scales but alleviates tensions on small scales. This small-scale behavior is due to characteristic cores in ULDM called solitons, which also correspond to the ground state of the self-gravitating quantum system governing ULDM. We calculate the full spectrum of eigenstates and decompose simulations of ULDM into these states, allowing us to precisely track the evolution of the tell-tale soliton cores and the surrounding halo "skirt". Using this formalism, we investigate formation of halos through binary soliton collisions and the dependence of the final halo product on initial parameters, which allows us to comment on the core-halo mass relation of ULDM. We also link characteristic ULDM halo behavior—such as the soliton "breathing mode" and random walk of the center of mass—to the presence of certain modes. Finally, we comment on the relationship between eigenenergies and oscillatory timescales present in the system, as well as future directions for understanding ULDM through the language of its eigenstates. |
Saturday, April 15, 2023 1:54PM - 2:06PM |
C14.00003: Distribution Functions of Dark Matter Halos Axel Gross, Yong-Zhong Qian, Zhaozhou Li The spherical NFW profile provides a good approximation to the density distributions of dark matter halos. In dynamical equilibrium, this density profile should correspond to a stationary distribution function of dark matter in phase space. We derive this distribution function and show that it is a good match to those obtained from N-body simulations. Additionally, we demonstrate a simple scaling relationship between R(E), the inversion of the potential energy, and the distribution function, and we show how this scaling can be used to well approximate the distribution function. |
Saturday, April 15, 2023 2:06PM - 2:18PM |
C14.00004: Producing Mixed Sterile Neutrino Dark Matter Models Emma Horner, Chad Kishimoto, Francisco Munguia Wulftange An observed excess in stacked galaxy X-ray spectra at 3.55 keV can be interpreted as the decay of a 7.1 keV sterile neutrino dark matter particle. Here, we explore various scenarios for the lepton number-driven production of sterile neutrino dark matter in the early universe. We discuss these mixed sterile neutrino dark matter models (sterile neutrinos plus cold dark matter), properties of the sterile neutrino dark matter spectra formed, and how characteristics of these spectra – and the physics that form them – can constrain these models through the formation of small-scale structure. |
Saturday, April 15, 2023 2:18PM - 2:30PM |
C14.00005: Small-Scale Structure Formation in Mixed Sterile Neutrino Dark Matter Models Francisco D Munguia Wulftange, Emma Horner, Chad Kishimoto An observed excess in stacked galaxy X-ray spectra at 3.55 keV can be interpreted as the decay of a 7.1 keV sterile neutrino dark matter particle. Here, we explore various scenarios for the lepton number-driven production of sterile neutrino dark matter in the early universe. We discuss these mixed sterile neutrino dark matter models (sterile neutrinos plus cold dark matter), properties of the sterile neutrino dark matter spectra formed, and how characteristics of these spectra – and the physics that form them – can constrain these models through the formation of small-scale structure. |
Saturday, April 15, 2023 2:30PM - 2:42PM |
C14.00006: The torsion of stellar streams due to a nonspherical dark matter halo Felipe José Llanes Estrada We have recently pointed out that flattening rotation curves v(r) are naturally explained by elongated (prolate) Dark Matter (DM) distributions, and provided competitive fits to the SPARC database. To further probe the geometry of the halo one needs out-of-plane observables. |
Saturday, April 15, 2023 2:42PM - 2:54PM |
C14.00007: Two-Point Correlation Function Studies for the Milky Way: Discovery of Spatial Clustering from Disk Excitations and Substructure Susan V Gardner, Austin Hinkel, Brian Yanny We introduce a two-particle correlation function (2PCF) for the Milky Way, constructed to probe spatial correlations in the orthogonal directions of the stellar disk in the Galactic cylindrical coordinates of R, Φ, and z. We use this new tool to probe the structure and dynamics of the Galaxy using the carefully selected set of solar neighborhood stars (d is less than 3 kpc) from Gaia Data Release 2 that we previously employed for studies of axial symmetry breaking in stellar number counts. We make additional, extensive tests, comparing to reference numerical simulations, to ensure our control over possibly confounding systematic effects. Supposing either axial or north–south symmetry, we divide this data set into two nominally symmetric sectors and construct the 2PCF, in the manner of the Landy–Szalay estimator, from the Gaia data. In so doing, we have discovered distinct symmetry-breaking patterns in the 2PCF in its orthogonal directions, thus establishing the existence of correlations in stellar number counts alone at subkiloparsec length scales for the very first time. In particular, we observe extensive wavelike structures of amplitude greatly in excess of what we would estimate if the system were in a steady state. We study the variations in these patterns across the Galactic disk, and with increasing |z|, and we show how our results complement other observations of non-steady-state effects near the Sun, such as vertical asymmetries in stellar number counts and the Gaia snail. |
Saturday, April 15, 2023 2:54PM - 3:06PM |
C14.00008: Light dark matter density distribution in the Sun Weizhen E Zhang, Kenny C. Y. Ng Weakly interacting massive particle (WIMP) is a popular dark matter candidate that can scatter with the nuclei of the Sun and lose energy. These WIMPs would then be captured and accumulate in the center of the Sun and annihilate to produce potentially detectable neutrino flux. This method, however, requires knowledge of the dark matter density distribution in the Sun after solar capture. In this case, we solve for the dark matter density distribution numerically taking into account evaporation, which has never been done before. The correct distribution is important for accurate inference in case of a detection from the Sun. In addition, a potential bound dark matter distribution outside the solar atmospheric, could allow for EM search of dark matter from the Sun. |
Saturday, April 15, 2023 3:06PM - 3:18PM |
C14.00009: Celestial Objects as Asymmetric Dark Matter Detectors Anupam Ray Non-annihilating dark matter particles, owing to their interactions with the ordinary baryonic matter, can efficiently accumulate inside celestial objects. For heavy dark matter, they gravitate towards the core of the celestial objects, thermalize in a small core region, and eventually form tiny black holes via core collapse, eventually transmuting the host objects to low mass black holes. We demonstrate that the existence of a variety of celestial objects provides stringent constraints on strongly-interacting heavy dark matter, a blind-spot for the terrestrial dark matter detectors as well as for the cosmological probes. Celestial objects with larger size and lower core temperature, such as Jupiter, are the most optimal detectors to probe strongly-interacting heavy asymmetric dark matter. We also show that such transmuted low mass black holes can be probed in the existing GW data. |
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