Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session K15: Large Scale Structure - Theory |
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Sponsoring Units: DAP Chair: Michael Troxel, Ohio State University Room: B230-231 |
Sunday, April 15, 2018 3:30PM - 3:42PM |
K15.00001: Theoretical Systematics of Future Baryon Acoustic Oscillation Surveys Zhejie Ding, Hee-Jong Seo, Zvonimir Vlah, Yu Feng, Marcel Schmittfull, Florian Beutler Future Baryon Acoustic Oscillation surveys aim at observing galaxy clustering over a wide range of redshift and galaxy populations at great precision in order to detect any deviation of dark energy from the $\rm{\Lambda CDM}$ model. With the statistical error of such surveys reaching tenths of a percent, it is critical to control the BAO systematics below the level of $\sim 0.1\%$. We utilize a set of paired simulations that were designed to mitigate the sample variance effect on the BAO feature and evaluated the BAO systematics as precisely as $\sim 0.01\%$. We report anisotropic BAO scale shifts before and after density field reconstruction in the presence of redshift-space distortions over a wide range of redshift, galaxy/halo biases, and shot noise levels. We test different reconstruction schemes and different smoothing filter scales, and introduce physically-motivated BAO fitting models. We test these models from the perspective of robust BAO measurements and non-BAO information such as growth rate and nonlinear bias. We find that pre-reconstruction BAO scale has moderate fitting-model dependence at the level of $0.1\%-0.2\%$ for matter while the dependence is substantially reduced to less than $0.07\%$ for halos. We detail other systematics in the talk. [Preview Abstract] |
Sunday, April 15, 2018 3:42PM - 3:54PM |
K15.00002: Redshift-space streaming velocity effects on the baryon acoustic oscillation scale Jahmour Givans, Christopher Hirata Baryon acoustic oscillations (BAOs) have emerged as a leading probe of cosmic acceleration. If researchers wish to use the BAO scale as an accurate standard ruler, we must account for physical effects which can shift this scale. The streaming velocity effect is one such example first noted by Tseliakhovich \& Hirata (2010). Later works examined streaming velocity-induced BAO shifts in real space (Blazek et al. 2016) and in redshift-space (Beutler et al. 2016). I present results of our redshift-space streaming velocity effect analysis on galaxies. I will then discuss our present work related to performing a similar analysis using the Lyman-$\alpha$ forest as a tracer of structure growth. The latest preliminary results and future expectations will be included. [Preview Abstract] |
Sunday, April 15, 2018 3:54PM - 4:06PM |
K15.00003: Dark matter halos in the multicomponent model. Substructure and density profiles of galactic halos Keita Todoroki, Mikhail V. Medvedev Multicomponent dark matter with inter-conversions of mass eigenstates into one another is known to successfully and simultaneously resolve $\Lambda$CDM problems at galactic and sub-galactic scales. Here, we present $N$-body simulations of the simplest two-component (2cDM) model with large set of velocity-dependent cross-sections, $\sigma(v)\propto v^{a}$, and compare them with observational data. They show that the 2cDM paradigm with the self-interaction cross-sections $0.01\le \sigma_0/m\le 1$~cm$^2$g$^{-1}$ and the mass degeneracy $\Delta m/m\sim 10^{-7}-10^{-8}$ robustly resolves the substructure and too-big-to-fail problems by suppressing the substructure with $V_{\rm circ,max} \lesssim100$~km~s$^{-1}$. Furthermore, 2cDM robustly suppresses central cusps in dwarf halos with $M \sim 4-5 \times10^{11} M_{\odot}$, thus resolving the core-cusp problem as well. The core radii are controlled by $\sigma_0/m$ and the DM cross-section's velocity-dependent power-law indices $(a_s,a_c)$, but are largely insensitive to the species' mass degeneracy. Next, there is disagreement between the radial distribution of dwarfs in a host halo observed in the Local Group and simulated with CDM, which poses one more small-scale problem to CDM, which is alleviated by 2cDM. [Preview Abstract] |
Sunday, April 15, 2018 4:06PM - 4:18PM |
K15.00004: Astrophysical implications of Dark Matter interacting with baryons Digvijay Wadekar, Glennys Farrar It has recently been shown that a DM-baryon interaction cross-section around $\sim 10^{-25} \textup{cm}^2$ is compatible with direct detection limits for DM particles with a mass of $\sim$GeV. We report simple simulations of galaxies with a halo composed of such interacting DM particles. We study the implications of such interactions for the spatial and velocity distribution of the DM in our Galaxy. Simulations show that the extended DM halo is unaffected, but locally, the DM comes into quasi-co-rotation with the gas disk, potentially explaining correlated structure observed in gas and DM in rotation curves. DM-baryon collisions also heat the gas in galaxies and galaxy clusters, which can address long-standing astrophysical problems like star-formation quenching observed in galaxies and hot gas components observed in centers of galaxy clusters. [Preview Abstract] |
Sunday, April 15, 2018 4:18PM - 4:30PM |
K15.00005: There is No Missing Satellites Problem Stacy Kim, Annika Peter, Jonathan Hargis A critical challenge to the cold dark matter (CDM) paradigm is that there are fewer satellites observed around the Milky Way than found in simulations of dark matter substructure. We show that there is a match between the observed satellite counts corrected by the detection efficiency of the Sloan Digital Sky Survey (for luminosities $L \ge$ 340 L$_\odot$) and the number of luminous satellites predicted by CDM, assuming an empirical relation between stellar mass and halo mass. The ``missing satellites problem'', cast in terms of number counts, is thus solved, and implies that luminous satellites inhabit subhalos as small as 10$^7-$10$^8$ M$_\odot$. The total number of Milky Way satellites depends sensitively on the spatial distribution of satellites. We also show that warm dark matter (WDM) models with a thermal relic mass smaller than 4 keV are robustly ruled out, and that limits of $m_{\rm WDM} \ge$ 8 keV from the Milky Way are probable in the near future. Similarly stringent constraints can be placed on any dark matter model that leads to a suppression of the matter power spectrum on $\sim$10$^7$ M$_\odot$ scales. Measurements of completely dark halos below $10^8$ M$_\odot$, achievable with substructure lensing, are the next frontier for tests of CDM. [Preview Abstract] |
Sunday, April 15, 2018 4:30PM - 4:42PM |
K15.00006: The Morphology of Disk Galaxies in Galaxy Clusters with Dark Matter Self-Interactions Lucas Secco, Amanda Farah, Bhuvnesh Jain, Susmita Adhikari, Arka Banerjee, Neal Dalal We use numerical simulations to study the effect of self-interacting dark matter (SIDM) on the morphology of disk galaxies falling into galaxy clusters. An effective drag force on dark matter leads to offsets of the stellar disk with respect to the surrounding halo, causing distortions in the disk. For anisotropic scattering cross-sections of 0.5 and 1.0$\,$cm$^2\,$g$^{-1}$, we show that potentially observable warps, asymmetries, and thickening of the disk occur in simulations. With further analysis of the potential systematic uncertainties of these novel probes, galaxy morphologies could impose tight constraints on SIDM cross-sections with current and future observations. [Preview Abstract] |
Sunday, April 15, 2018 4:42PM - 4:54PM |
K15.00007: Galactic halo model selection using Bayesian inference under directional dark matter detection Louisa Ruixue Huang, James Battat Directional detection is a promising way to detect a potential dark matter candidate, Weakly Interacting Massive Particles (WIMPs). It does not only allow us to distinguish WIMP signals from potential backgrounds with only a small number of events, but also constrain the WIMP velocity distribution in the galaxy. Furthermore, by comparing the Bayesian evidence values resulting from applying different models to the same data, we are able to discriminate between different models of dark matter velocity distribution. We study the ability of directional detectors with different angular resolutions to distinguish between the truncated Standard Halo Model and the triaxial model. We find that with even modest angular resolution, a directional detector with 3D tracking and vector recoil sensitivity could correctly identify a triaxial halo with $\mathcal{O}(350)$ events. [Preview Abstract] |
Sunday, April 15, 2018 4:54PM - 5:06PM |
K15.00008: Self Interacting Dark Matter and the Galaxy Core-Cusp problem Quynh Lan Nguyen, Grant Mathews The core-cusp problem remains as one of the unresolved challenges between observation and simulations in the standard $\Lambda $ CDM model for the formation of galaxies. The problem is that $\Lambda $ CDM simulations predict that the center of galactic dark matter halos contains a steep power-law mass density profile. However, observations of dwarf galaxies in the Local Group reveal a density profile consistent with a nearly flat distribution of dark matter near the center. Many solutions to this dilemma have been proposed. We discuss the possibility that the dark matter particles themselves self-interact and scatter. The scattering of dark matter particles then can smooth out their profile in high-density regions. We also summarize a theoretical model as to how self- interacting dark matter may arise. We implement this form in simulations of self-interacting dark matter in models for galaxy formation and evolution. Constraints on properties of this form of self-interacting dark matter will be summarized. [Preview Abstract] |
Sunday, April 15, 2018 5:06PM - 5:18PM |
K15.00009: Adiabatic Dark Matter Spikes Around Kerr Black Holes Augusto Medeiros da Rosa, Francesc Ferrer, Clifford Will The growth of a massive black hole will steepen the cold dark matter density at the center of a galaxy into a dense spike, enhancing the prospects for indirect detection. We study the impact of black hole spin on the density profile using the exact Kerr geometry of the black whole in a fully relativistic adiabatic growth framework. We find that, despite the transfer of angular momentum from the hole to the halo, rotation increases significantly the dark matter density close to the black hole. The gravitational effects are still dominated by the black hole within its influence radius, but the larger dark matter annihilation fluxes might be relevant for indirect detection estimates [Preview Abstract] |
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