Astrophysical Interplay in Dark Matter Searches

I discuss recent progress in dark matter searches, focusing in particular on how rigorous modeling the dark matter distribution in the Galaxy and in its satellite galaxies improves our interpretation of the limits on the annihilation and elastic scattering cross sections. Looking forward to indirect and direct searches that will operate during the next decade, I review methods for extracting the properties of the dark matter in these experiments in the presence of unknown Galactic model parameters.Comment: Contribution to proceedings of CETUP* workshop in Lead, South Dakota, July 10 - August 1, 201

Kinematics of Milky Way Satellites: Mass Estimates, Rotation Limits, and Proper Motions

In the past several years high resolution kinematic data sets from Milky Way satellite galaxies have confirmed earlier indications that these systems are dark matter dominated objects. Further understanding of what these galaxies reveal about cosmology and the small scale structure of dark matter relies in large part on a more detailed interpretation of their internal kinematics. This article discusses a likelihood formalism that extracts important quantities from the kinematic data, including the amplitude of rotation, proper motion, and the mass distribution. In the simplest model the projected error on the rotational amplitude is shown to be $\sim 0.5$ km s$^{-1}$ with $\sim 10^3$ stars from either classical or ultra-faint satellites. The galaxy Sculptor is analyzed for the presence of a rotational signal; no significant detection of rotation is found, and given this result limits are derived on the Sculptor proper motion. A criteria for model selection is discussed that determines the parameters required to describe the dark matter halo density profiles and the stellar velocity anisotropy. Applied to four data sets with a wide range of velocities, the likelihood is found to be more sensitive to variations in the slope of the dark matter density profile than variations in the velocity anisotropy. Models with variable radial velocity anisotropy are shown to be preferred relative to those in which this quantity is constant at all radii in the galaxy.Comment: 20 pages. To appear in Advances in Astronomy, Dwarf-Galaxy Cosmology issu

The Cosmic Abundance of Classical Milky Way Satellites

We study the abundance of satellites akin to the brightest, classical dwarf spheroidals around galaxies similar in magnitude and isolation to the Milky Way and M31 in the Sloan Digital Sky Survey. From a combination of photometric and spectroscopic redshifts, we bound the mean and the intrinsic scatter in the number of satellites down to ten magnitudes fainter than the Milky Way. Restricting to magnitudes brighter than Sagittarius, we show that the Milky Way is not a significant statistical outlier in its population of classical dwarf spheroidals. At fainter magnitudes, we find an upper limit of 13 on the mean number of satellites brighter than the Fornax dwarf spheroidal. Methods to improve these limits that utilize full photometric redshift distributions hold promise, but are currently limited by incompleteness at the very lowest redshifts. Theoretical models are left to explain why the majority of dark matter subhalos that orbit Milky Way-like galaxies are inefficient at making galaxies at the luminosity scale of the brightest dwarf spheroidals, or why these subhalos predicted by Lambda-CDM do not exist.Comment: 8 pages, 2 figure

New Constraints on Isospin-Violating Dark Matter

We derive bounds on the dark matter annihilation cross-section for low-mass (5-20 GeV) dark matter annihilating primarily to up or down quarks, using the Fermi-LAT bound on gamma-rays from Milky Way satellites. For models in which dark matter-Standard Model interactions are mediated by particular contact operators, we show that these bounds can be directly translated into bounds on the dark matter-proton scattering cross-section. For isospin-violating dark matter, these constraints are tight enough to begin to constrain the parameter-space consistent with experimental signals of low-mass dark matter. We discuss possible models that can evade these bounds.Comment: 6 pages, 2 figures, LaTeX, some clarifications and minor errors corrected, citations adde

WIMP searches with gamma rays in the Fermi era: challenges, methods and results

The launch of the gamma-ray telescope Fermi Large Area Telescope (Fermi-LAT) started a pivotal period in indirect detection of dark matter. By outperforming expectations, for the first time a robust and stringent test of the paradigm of weakly interacting massive particles (WIMPs) is within reach. In this paper, we discuss astrophysical targets for WIMP detection and the challenges they present, review the analysis tools which have been employed to tackle these challenges, and summarize the status of constraints on and the claimed detections in the WIMP parameter space. Methods and results will be discussed in comparison to Imaging Air Cherenkov Telescopes. We also provide an outlook on short term and longer term developments.Comment: 72 pages, 7 figures, Invited review for Journal of Experimental and Theoretical Physics,v3: added a few references, addressed referee comment

Galactic Searches for Dark Matter

For nearly a century, more mass has been measured in galaxies than is contained in the luminous stars and gas. Through continual advances in observations and theory, it has become clear that the dark matter in galaxies is not comprised of known astronomical objects or baryonic matter, and that identification of it is certain to reveal a profound connection between astrophysics, cosmology, and fundamental physics. The best explanation for dark matter is that it is in the form of a yet undiscovered particle of nature, with experiments now gaining sensitivity to the most well-motivated particle dark matter candidates. In this article, I review measurements of dark matter in the Milky Way and its satellite galaxies and the status of Galactic searches for particle dark matter using a combination of terrestrial and space-based astroparticle detectors, and large scale astronomical surveys. I review the limits on the dark matter annihilation and scattering cross sections that can be extracted from both astroparticle experiments and astronomical observations, and explore the theoretical implications of these limits. I discuss methods to measure the properties of particle dark matter using future experiments, and conclude by highlighting the exciting potential for dark matter searches during the next decade, and beyond.Comment: Invited review to be submitted to Physics Reports. 116 pages of text and figures, 26 figures, 144 pages tota

Non-standard interactions of solar neutrinos in dark matter experiments

Non-standard neutrino interactions (NSI) affect both their propagation through matter and their detection, with bounds on NSI parameters coming from various astrophysical and terrestrial neutrino experiments. In this paper, we show that NSI can be probed in future direct dark matter detection experiments through both elastic neutrino-electron scattering and coherent neutrino-nucleus scattering, and that these channels provide complementary probes of NSI. We show NSI can increase the event rate due to solar neutrinos, with a sharp increase for lower nuclear recoil energy thresholds that are within reach for upcoming detectors. We also identify an interference range of NSI parameters for which the rate is reduced by approximately 40\%. Finally, we show that the "dark side" solution for the solar neutrino mixing angle may be discovered at forthcoming direct detection experiments.Comment: 12 pages, 5 figure