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Sample records for fermi constrains dark

  1. Constraining decaying dark matter with Fermi LAT gamma-rays

    SciTech Connect

    Zhang, Le; Sigl, Günter; Weniger, Christoph; Maccione, Luca; Redondo, Javier E-mail: christoph.weniger@desy.de E-mail: redondo@mppmm.mpg.de

    2010-06-01

    High energy electrons and positrons from decaying dark matter can produce a significant flux of gamma rays by inverse Compton off low energy photons in the interstellar radiation field. This possibility is inevitably related with the dark matter interpretation of the observed PAMELA and FERMI excesses. The aim of this paper is providing a simple and universal method to constrain dark matter models which produce electrons and positrons in their decay by using the Fermi LAT gamma-ray observations in the energy range between 0.5 GeV and 300 GeV. We provide a set of universal response functions that, once convolved with a specific dark matter model produce the desired constraints. Our response functions contain all the astrophysical inputs such as the electron propagation in the galaxy, the dark matter profile, the gamma-ray fluxes of known origin, and the Fermi LAT data. We study the uncertainties in the determination of the response functions and apply them to place constraints on some specific dark matter decay models that can well fit the positron and electron fluxes observed by PAMELA and Fermi LAT. To this end we also take into account prompt radiation from the dark matter decay. We find that with the available data decaying dark matter cannot be excluded as source of the PAMELA positron excess.

  2. Constraining Inert Triplet dark matter by the LHC and FermiLAT

    SciTech Connect

    Ayazi, Seyed Yaser; Firouzabadi, S. Mahdi E-mail: smmfirouz@yahoo.com

    2014-11-01

    We study collider phenomenology of inert triplet scalar dark matter at the LHC. We discuss possible decay of Higgs boson to dark matter candidate and apply current experimental data for invisible Higgs decay and R{sub γγ} to constrain parameter space of our model. We also investigate constraints on dark matter coming from forthcoming measurement, R{sub Zγ} and mono-Higgs production. We analytically calculate the annihilation cross section of dark matter candidate into 2γ and Zγ and then use FermiLAT data to put constraints on parameter space of Inert Triplet Model. We found that this limit can be stronger than the constraints provided by LUX experiment for low mass DM.

  3. Constraining the dark fluid

    SciTech Connect

    Kunz, Martin; Liddle, Andrew R.; Parkinson, David; Gao Changjun

    2009-10-15

    Cosmological observations are normally fit under the assumption that the dark sector can be decomposed into dark matter and dark energy components. However, as long as the probes remain purely gravitational, there is no unique decomposition and observations can only constrain a single dark fluid; this is known as the dark degeneracy. We use observations to directly constrain this dark fluid in a model-independent way, demonstrating, in particular, that the data cannot be fit by a dark fluid with a single constant equation of state. Parametrizing the dark fluid equation of state by a variety of polynomials in the scale factor a, we use current kinematical data to constrain the parameters. While the simplest interpretation of the dark fluid remains that it is comprised of separate dark matter and cosmological constant contributions, our results cover other model types including unified dark energy/matter scenarios.

  4. Constraining dark matter models from a combined analysis of Milky Way satellites with the Fermi Large Area Telescope.

    PubMed

    Ackermann, M; Ajello, M; Albert, A; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Cañadas, B; Caraveo, P A; Casandjian, J M; Cecchi, C; Charles, E; Chekhtman, A; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; de Angelis, A; de Palma, F; Dermer, C D; Digel, S W; do Couto e Silva, E; Drell, P S; Drlica-Wagner, A; Falletti, L; Favuzzi, C; Fegan, S J; Ferrara, E C; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Guiriec, S; Gustafsson, M; Hadasch, D; Hayashida, M; Hays, E; Hughes, R E; Jeltema, T E; Jóhannesson, G; Johnson, R P; Johnson, A S; Kamae, T; Katagiri, H; Kataoka, J; Knödlseder, J; Kuss, M; Lande, J; Latronico, L; Lionetto, A M; Llena Garde, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Mazziotta, M N; McEnery, J E; Mehault, J; Michelson, P F; Mitthumsiri, W; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Naumann-Godo, M; Norris, J P; Nuss, E; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ormes, J F; Ozaki, M; Paneque, D; Parent, D; Pesce-Rollins, M; Pierbattista, M; Piron, F; Pivato, G; Porter, T A; Profumo, S; Rainò, S; Razzano, M; Reimer, A; Reimer, O; Ritz, S; Roth, M; Sadrozinski, H F-W; Sbarra, C; Scargle, J D; Schalk, T L; Sgrò, C; Siskind, E J; Spandre, G; Spinelli, P; Strigari, L; Suson, D J; Tajima, H; Takahashi, H; Tanaka, T; Thayer, J G; Thayer, J B; Thompson, D J; Tibaldo, L; Tinivella, M; Torres, D F; Troja, E; Uchiyama, Y; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Wood, M; Yang, Z; Zimmer, S; Kaplinghat, M; Martinez, G D

    2011-12-01

    Satellite galaxies of the Milky Way are among the most promising targets for dark matter searches in gamma rays. We present a search for dark matter consisting of weakly interacting massive particles, applying a joint likelihood analysis to 10 satellite galaxies with 24 months of data of the Fermi Large Area Telescope. No dark matter signal is detected. Including the uncertainty in the dark matter distribution, robust upper limits are placed on dark matter annihilation cross sections. The 95% confidence level upper limits range from about 10(-26)  cm3  s(-1) at 5 GeV to about 5×10(-23)   cm3  s(-1) at 1 TeV, depending on the dark matter annihilation final state. For the first time, using gamma rays, we are able to rule out models with the most generic cross section (∼3×10(-26)  cm3  s(-1) for a purely s-wave cross section), without assuming additional boost factors. PMID:22242987

  5. Constraining Dark Matter Models from a Combined Analysis of Milky Way Satellites with the Fermi Large Area Telescope

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bladford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Ferrara, E. C.; Gehrels, N.; Hays, E.; Scargle, J. D.; Thompson, D. J.; Troja, E.

    2011-01-01

    Satellite galaxies of the Milky Way are among the most promising targets for dark matter searches in gamma rays. We present a search for dark matter consisting of weakly interacting massive particles, applying a joint likelihood analysis to 10 satellite galaxies with 24 months of data of the Fermi Large Area Telescope. No dark matter signal is detected. Including the uncertainty in the dark matter distribution, robust upper limits are placed on dark matter annihilation cross sections. The 95% confidence level upper limits range from about 10(exp -26) cm(exp 3) / s at 5 GeV to about 5 X 10(exp -23) cm(exp 3)/ s at 1 TeV, depending on the dark matter annihilation final state. For the first time, using gamma rays, we are able to rule out models with the most generic cross section (approx 3 X 10(exp -26) cm(exp 3)/s for a purely s-wave cross section), without assuming additional boost factors.

  6. Constraining Dark Matter Models from a Combined Analysis of Milky Way Satellites with the Fermi Large Area Telescope

    SciTech Connect

    Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W.B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R.D.; Bloom, E.D.; Bonamente, E.; Borgland, A.W.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Burnett, T.H.; Buson, S.; /more authors..

    2012-09-14

    Satellite galaxies of the Milky Way are among the most promising targets for dark matter searches in gamma rays. We present a search for dark matter consisting of weakly interacting massive particles, applying a joint likelihood analysis to 10 satellite galaxies with 24 months of data of the Fermi Large Area Telescope. No dark matter signal is detected. Including the uncertainty in the dark matter distribution, robust upper limits are placed on dark matter annihilation cross sections. The 95% confidence level upper limits range from about 10{sup -26} cm{sup 3} s{sup -1} at 5 GeV to about 5 x 10{sup -23} cm{sup 3} s{sup -1} at 1 TeV, depending on the dark matter annihilation final state. For the first time, using gamma rays, we are able to rule out models with the most generic cross section ({approx}3 x 10{sup -26} cm{sup 3} s{sup -1} for a purely s-wave cross section), without assuming additional boost factors.

  7. Fermi/LAT observations of dwarf galaxies highly constrain a dark matter interpretation of excess positrons seen in AMS-02, HEAT, and PAMELA

    NASA Astrophysics Data System (ADS)

    López, Alejandro; Savage, Christopher; Spolyar, Douglas; Adams, Douglas Q.

    2016-03-01

    It is shown that a Weakly Interacting Massive dark matter Particle (WIMP) interpretation for the positron excess observed in a variety of experiments, HEAT, PAMELA, and AMS-02, is highly constrained by the Fermi/LAT observations of dwarf galaxies. In particular, this paper examines the annihilation channels that best fit the current AMS-02 data (Boudaud et al., 2014), specifically focusing on channels and parameter space not previously explored by the Fermi/LAT collaboration. The Fermi satellite has surveyed the γ-ray sky, and its observations of dwarf satellites are used to place strong bounds on the annihilation of WIMPs into a variety of channels. For the single channel case, we find that dark matter annihilation into {bbar b,e+e-, μ+μ-, τ+τ-,4-e or 4-τ } is ruled out as an explanation of the AMS positron excess (here b quarks are a proxy for all quarks, gauge and Higgs bosons). In addition, we find that the Fermi/LAT 2σ upper limits, assuming the best-fit AMS-02 branching ratios, exclude multichannel combinations into bbar b and leptons. The tension between the results might relax if the branching ratios are allowed to deviate from their best-fit values, though a substantial change would be required. Of all the channels we considered, the only viable channel that survives the Fermi/LAT constraint and produces a good fit to the AMS-02 data is annihilation (via a mediator) to 4-μ, or mainly to 4-μ in the case of multichannel combinations.

  8. Constraining Dark Energy

    NASA Astrophysics Data System (ADS)

    Abrahamse, Augusta

    2010-12-01

    Future advances in cosmology will depend on the next generation of cosmological observations and how they shape our theoretical understanding of the universe. Current theoretical ideas, however, have an important role to play in guiding the design of such observational programs. The work presented in this thesis concerns the intersection of observation and theory, particularly as it relates to advancing our understanding of the accelerated expansion of the universe (or the dark energy). Chapters 2 - 4 make use of the simulated data sets developed by the Dark Energy Task Force (DETF) for a number of cosmological observations currently in the experimental pipeline. We use these forecast data in the analysis of four quintessence models of dark energy: the PNGB, Exponential, Albrecht-Skordis and Inverse Power Law (IPL) models. Using Markov Chain Monte Carlo sampling techniques we examine the ability of each simulated data set to constrain the parameter space of these models. We examine the potential of the data for differentiating time-varying models from a pure cosmological constant. Additionally, we introduce an abstract parameter space to facilitate comparison between models and investigate the ability of future data to distinguish between these quintessence models. In Chapter 5 we present work towards understanding the effects of systematic errors associated with photometric redshift estimates. Due to the need to sample a vast number of deep and faint galaxies, photometric redshifts will be used in a wide range of future cosmological observations including gravitational weak lensing, baryon accoustic oscillations and type 1A supernovae observations. The uncertainty in the redshift distributions of galaxies has a significant potential impact on the cosmological parameter values inferred from such observations. We introduce a method for parameterizing uncertainties in modeling assumptions affecting photometric redshift calculations and for propagating these

  9. Traveling dark solitons in superfluid Fermi gases

    SciTech Connect

    Liao Renyuan; Brand, Joachim

    2011-04-15

    Families of dark solitons exist in superfluid Fermi gases. The energy-velocity dispersion and number of depleted particles completely determine the dynamics of dark solitons on a slowly varying background density. For the unitary Fermi gas, we determine these relations from general scaling arguments and conservation of local particle number. We find solitons to oscillate sinusoidally at the trap frequency reduced by a factor of 1/{radical}(3). Numerical integration of the time-dependent Bogoliubov-de Gennes equation determines spatial profiles and soliton-dispersion relations across the BEC-BCS crossover, and proves consistent with the scaling relations at unitarity.

  10. Detecting Dark Matter annihilation lines with Fermi

    SciTech Connect

    Ylinen, Tomi; Edmonds, Yvonne; Bloom, Elliott D.; Conrad, Jan; /Royal Inst. Tech., Stockholm /Kalmar U. /KIPAC, Menlo Park /SLAC /Stockholm U.

    2009-05-15

    Dark matter constitutes one of the most intriguing but so far unresolved issues in physics today. In many extensions of the Standard Model the existence of a stable Weakly Interacting Massive Particle (WIMP) is predicted. The WIMP is an excellent dark matter particle candidate and one of the most interesting scenarios include an annihilation of two WIMPs into two gamma-rays. If the WIMPs are assumed to be non-relativistic, the resulting photons will both have an energy equal to the mass of the WIMP and manifest themselves as a monochromatic spectral line in the energy spectrum. This type of signal would represent a 'smoking gun' for dark matter, since no other known astrophysical process should be able to produce it. In these proceedings we give an overview of the different approaches to a search for dark matter lines that the Fermi-LAT collaboration is pursuing and the various challenges involved.

  11. Dark Matter Searches with the Fermi Large Area Telescope

    SciTech Connect

    Meurer, Christine

    2008-12-24

    The Fermi Gamma-Ray Space Telescope, successfully launched on June 11th, 2008, is the next generation satellite experiment for high-energy gamma-ray astronomy. The main instrument, the Fermi Large Area Telescope (LAT), with a wide field of view (>2 sr), a large effective area (>8000 cm{sup 2} at 1 GeV), sub-arcminute source localization, a large energy range (20 MeV-300 GeV) and a good energy resolution (close to 8% at 1 GeV), has excellent potential to either discover or to constrain a Dark Matter signal. The Fermi LAT team pursues complementary searches for signatures of particle Dark Matter in different search regions such as the galactic center, galactic satellites and subhalos, the milky way halo, extragalactic regions as well as the search for spectral lines. In these proceedings we examine the potential of the LAT to detect gamma-rays coming from Weakly Interacting Massive Particle annihilations in these regions with special focus on the galactic center region.

  12. Constraining dark sectors with monojets and dijets

    NASA Astrophysics Data System (ADS)

    Chala, Mikael; Kahlhoefer, Felix; McCullough, Matthew; Nardini, Germano; Schmidt-Hoberg, Kai

    2015-07-01

    We consider dark sector particles (DSPs) that obtain sizeable interactions with Standard Model fermions from a new mediator. While these particles can avoid observation in direct detection experiments, they are strongly constrained by LHC measurements. We demonstrate that there is an important complementarity between searches for DSP production and searches for the mediator itself, in particular bounds on (broad) dijet resonances. This observation is crucial not only in the case where the DSP is all of the dark matter but whenever — precisely due to its sizeable interactions with the visible sector — the DSP annihilates away so efficiently that it only forms a dark matter subcomponent. To highlight the different roles of DSP direct detection and LHC monojet and dijet searches, as well as perturbativity constraints, we first analyse the exemplary case of an axial-vector mediator and then generalise our results. We find important implications for the interpretation of LHC dark matter searches in terms of simplified models.

  13. Constraining condensate dark matter in galaxy clusters

    NASA Astrophysics Data System (ADS)

    de Souza, J. C. C.; Ujevic, M.

    2015-09-01

    We constrain scattering length parameters in a Bose-Einstein condensate dark matter model by using galaxy clusters radii, with the implementation of a method previously applied to galaxies. At the present work, we use a sample of 114 clusters radii in order to obtain the scattering lengths associated with a dark matter particle mass in the range - eV. We obtain scattering lengths that are five orders of magnitude larger than the ones found in the galactic case, even when taking into account the cosmological expansion in the cluster scale by means of the introduction of a small cosmological constant. We also construct and compare curves for the orbital velocity of a test particle in the vicinity of a dark matter cluster in both the expanding and the non-expanding cases.

  14. Constraining dark matter through 21-cm observations

    NASA Astrophysics Data System (ADS)

    Valdés, M.; Ferrara, A.; Mapelli, M.; Ripamonti, E.

    2007-05-01

    Beyond reionization epoch cosmic hydrogen is neutral and can be directly observed through its 21-cm line signal. If dark matter (DM) decays or annihilates, the corresponding energy input affects the hydrogen kinetic temperature and ionized fraction, and contributes to the Lyα background. The changes induced by these processes on the 21-cm signal can then be used to constrain the proposed DM candidates, among which we select the three most popular ones: (i) 25-keV decaying sterile neutrinos, (ii) 10-MeV decaying light dark matter (LDM) and (iii) 10-MeV annihilating LDM. Although we find that the DM effects are considerably smaller than found by previous studies (due to a more physical description of the energy transfer from DM to the gas), we conclude that combined observations of the 21-cm background and of its gradient should be able to put constrains at least on LDM candidates. In fact, LDM decays (annihilations) induce differential brightness temperature variations with respect to the non-decaying/annihilating DM case up to ΔδTb = 8 (22) mK at about 50 (15) MHz. In principle, this signal could be detected both by current single-dish radio telescopes and future facilities as Low Frequency Array; however, this assumes that ionospheric, interference and foreground issues can be properly taken care of.

  15. Dark lump excitations in superfluid Fermi gases

    NASA Astrophysics Data System (ADS)

    Xu, Yan-Xia; Duan, Wen-Shan

    2012-11-01

    We study the linear and nonlinear properties of two-dimensional matter-wave pulses in disk-shaped superfluid Fermi gases. A Kadomtsev—Petviashvili I (KPI) solitary wave has been realized for superfluid Fermi gases in the limited cases of Bardeen—Cooper—Schrieffer (BCS) regime, Bose—Einstein condensate (BEC) regime, and unitarity regime. One-lump solution as well as one-line soliton solutions for the KPI equation are obtained, and two-line soliton solutions with the same amplitude are also studied in the limited cases. The dependence of the lump propagating velocity and the sound speed of two-dimensional superfluid Fermi gases on the interaction parameter are investigated for the limited cases of BEC and unitarity.

  16. Detecting superlight dark matter with Fermi-degenerate materials

    NASA Astrophysics Data System (ADS)

    Hochberg, Yonit; Pyle, Matt; Zhao, Yue; Zurek, Kathryn M.

    2016-08-01

    We examine in greater detail the recent proposal of using superconductors for detecting dark matter as light as the warm dark matter limit of O (keV). Detection of suc light dark matter is possible if the entire kinetic energy of the dark matter is extracted in the scattering, and if the experiment is sensitive to O (meV) energy depositions. This is the case for Fermi-degenerate materials in which the Fermi velocity exceeds the dark matter velocity dispersion in the Milky Way of ˜ 10-3. We focus on a concrete experimental proposal using a superconducting target with a transition edge sensor in order to detect the small energy deposits from the dark matter scatterings. Considering a wide variety of constraints, from dark matter self-interactions to the cosmic microwave background, we show that models consistent with cosmological/astrophysical and terrestrial constraints are observable with such detectors. A wider range of viable models with dark matter mass below an MeV is available if dark matter or mediator properties (such as couplings or masses) differ at BBN epoch or in stellar interiors from those in superconductors. We also show that metal targets pay a strong in-medium suppression for kinetically mixed mediators; this suppression is alleviated with insulating targets.

  17. Constraining Dark Matter and Dark Energy Models using Astrophysical Surveys

    NASA Astrophysics Data System (ADS)

    Cieplak, Agnieszka M.

    This thesis addresses astrophysical probes to constrain dark matter (DM) and dark energy models. Primordial black holes (PBHs) remain one of the few DM candidates within the Standard Model of Particle Physics. This thesis presents a new probe of this PBH DM, using the microlensing of the source stars monitored by the already existing Kepler satellite. With its photometric precision and the large projected cross section of the nearby stars, it is found that previous constraints on PBH DM could theoretically be extended by two orders of magnitude. Correcting a well-known microlensing formula, a limb-darkening analysis is included, and a new approximation is calculated for future star selection. A preliminary prediction is calculated for the planned Wide-Field Infrared Survey Telescope. A preliminary study of the first two years of publicly available Kepler data is presented. The investigation yields many new sources of background error not predicted in the theoretical calculations, such as stellar flares and comets in the field of view. Since no PBH candidates are detected, an efficiency of detection is therefore calculated by running a Monte Carlo with fake limb-darkened finite-source microlensing events. It is found that with just the first 8 quarters of data, a full order of magnitude of the PBH mass range can be already constrained. Finally, one of the astrophysical probes of dark energy is also addressed - specifically, the baryon acoustic oscillations (BAO) measurement in the gas distribution, as detected in quasar absorption lines. This unique measurement of dark energy at intermediate redshifts is being measured by current telescope surveys. The last part of this thesis therefore focuses on understanding the systematic effects in such a detection. Since the bias between the underlying dark matter distribution and the measured gas flux distribution is based on gas physics, hydrodynamic simulations are used to understand the evolution of neutral hydrogen over

  18. CONSTRAINING DARK ENERGY WITH GAMMA-RAY BURSTS

    SciTech Connect

    Samushia, Lado; Ratra, Bharat E-mail: ratra@phys.ksu.ed

    2010-05-10

    We use the measurement of gamma-ray burst (GRB) distances to constrain dark energy cosmological model parameters. We employ two methods for analyzing GRB data-fitting luminosity relation of GRBs in each cosmology and using distance measures computed from binned GRB data. Current GRB data alone cannot tightly constrain cosmological parameters and allow for a wide range of dark energy models.

  19. DARK MATTER DECAY AND ANNIHILATION IN THE LOCAL UNIVERSE: CLUES FROM FERMI

    SciTech Connect

    Cuesta, A. J.; Zandanel, F.; Prada, F.; Jeltema, T. E.; Yepes, G.; Klypin, A.; Hoffman, Y.; Gottloeber, S.; Sanchez-Conde, M. A.; Pfrommer, C. E-mail: fabio@iaa.es

    2011-01-01

    We present all-sky simulated Fermi maps of {gamma}-rays from dark matter (DM) decay and annihilation in the local universe. The DM distribution is obtained from a constrained cosmological simulation of the neighboring large-scale structure provided by the CLUES project. The DM fields of density and density squared are then taken as an input for the Fermi observation simulation tool to predict the {gamma}-ray photon counts that Fermi would detect in 5 years of an all-sky survey for given DM models. Signal-to-noise ratio (S/N) sky maps have also been obtained by adopting the current Galactic and isotropic diffuse background models released by the Fermi Collaboration. We point out the possibility for Fermi to detect a DM {gamma}-ray signal in local extragalactic structures. In particular, we conclude here that Fermi observations of nearby clusters (e.g., Virgo and Coma) and filaments are expected to give stronger constraints on decaying DM compared to previous studies. As an example, we find a significant S/N in DM models with a decay rate fitting the positron excess as measured by PAMELA. This is the first time that DM filaments are shown to be promising targets for indirect detection of DM. On the other hand, the prospects for detectability of annihilating DM in local extragalactic structures are less optimistic even with extreme cross-sections. We make the DM density and density squared maps publicly available online.

  20. New limits on the dark matter lifetime from dwarf spheroidal galaxies using Fermi-LAT

    NASA Astrophysics Data System (ADS)

    Baring, Matthew G.; Ghosh, Tathagata; Queiroz, Farinaldo S.; Sinha, Kuver

    2016-05-01

    Dwarf spheroidal galaxies (dSphs) are promising targets for the indirect detection of dark matter through gamma-ray emission due to their proximity, lack of astrophysical backgrounds and high dark matter density. They are often used to place restrictive bounds on the dark matter annihilation cross section. In this paper, we analyze six years of Fermi-LAT gamma-ray data from 19 dSphs that are satellites of the Milky Way, and derive from a stacked analysis of 15 dSphs, robust 95% confidence level lower limits on the dark matter lifetime for several decay channels and dark matter masses between ˜1 GeV and 10 TeV. Our findings are based on a bin-by-bin maximum likelihood analysis treating the J -factor as a nuisance parameter using the Pass 8 event class. Our constraints from this ensemble are among the most stringent and solid in the literature, and competitive with existing ones coming from the extragalactic gamma-ray background, galaxy clusters, AMS-02 cosmic ray data, Super-K and ICECUBE neutrino data, while rather insensitive to systematic uncertainties. In particular, among gamma-ray searches, we improve existing limits for dark matter decaying into b ¯b (μ+μ-) for dark matter masses below ˜30 (200 ) GeV , demonstrating that dSphs are compelling targets for constraining dark matter decay lifetimes.

  1. Dark matter annihilation and the PAMELA, FERMI, and ATIC anomalies

    SciTech Connect

    El Zant, A. A.; Okada, H.; Khalil, S.

    2010-06-15

    If dark matter annihilation accounts for the tantalizing excess of cosmic ray electron/positrons, as reported by the PAMELA, ATIC, HESS, and FERMI observatories, then the implied annihilation cross section must be relatively large. This results, in the context of standard cosmological models, in very small relic dark matter abundances that are incompatible with astrophysical observations. We explore possible resolutions to this apparent conflict in terms of nonstandard cosmological scenarios; plausibly allowing for large cross sections, while maintaining relic abundances in accord with current observations.

  2. Annihilation Lines from Dark Matter with the Fermi-LAT

    SciTech Connect

    Ylinen, Tomi

    2010-06-23

    Dark matter is today one of the most intriguing but so far unresolved issues in physics. Many extensions of the Standard Model of particle physics predict a stable Weakly Interacting Massive Particle (WIMP) that may annihilate directly into two gamma-rays. If the WIMPs are non-relativistic, the gamma-rays from this channel will have an energy equal to the mass of the WIMP. The signature caused by this annihilation is a spectral line, smeared out only by the energy resolution of the detector. The signal would be a ''smoking gun'' for dark matter, since no other astrophysical source should be able to produce it. We present here the preliminary results from the search for a dark matter line on a limited data set from the Fermi Large Area Telescope (LAT), the main instrument onboard the Fermi Gamma-ray Space Telescope, which was successfully launched on June 11, 2008. The Fermi-LAT is a pair-conversion detector for gamma-rays with an energy range from 20 MeV to 300 GeV and has an unprecedented resolution and sensitivity.

  3. Annihilation Lines from Dark Matter with the Fermi-LAT

    NASA Astrophysics Data System (ADS)

    Ylinen, Tomi

    2010-06-01

    Dark matter is today one of the most intriguing but so far unresolved issues in physics. Many extensions of the Standard Model of particle physics predict a stable Weakly Interacting Massive Particle (WIMP) that may annihilate directly into two gamma-rays. If the WIMPs are non-relativistic, the gamma-rays from this channel will have an energy equal to the mass of the WIMP. The signature caused by this annihilation is a spectral line, smeared out only by the energy resolution of the detector. The signal would be a ``smoking gun'' for dark matter, since no other astrophysical source should be able to produce it. We present here the preliminary results from the search for a dark matter line on a limited data set from the Fermi Large Area Telescope (LAT), the main instrument onboard the Fermi Gamma-ray Space Telescope, which was successfully launched on June 11, 2008. The Fermi-LAT is a pair-conversion detector for gamma-rays with an energy range from 20 MeV to 300 GeV and has an unprecedented resolution and sensitivity.

  4. Constraining dark energy fluctuations with supernova correlations

    SciTech Connect

    Blomqvist, Michael; Enander, Jonas; Mörtsell, Edvard E-mail: enander@fysik.su.se

    2010-10-01

    We investigate constraints on dark energy fluctuations using type Ia supernovae. If dark energy is not in the form of a cosmological constant, that is if the equation of state w≠−1, we expect not only temporal, but also spatial variations in the energy density. Such fluctuations would cause local variations in the universal expansion rate and directional dependences in the redshift-distance relation. We present a scheme for relating a power spectrum of dark energy fluctuations to an angular covariance function of standard candle magnitude fluctuations. The predictions for a phenomenological model of dark energy fluctuations are compared to observational data in the form of the measured angular covariance of Hubble diagram magnitude residuals for type Ia supernovae in the Union2 compilation. The observational result is consistent with zero dark energy fluctuations. However, due to the limitations in statistics, current data still allow for quite general dark energy fluctuations as long as they are in the linear regime.

  5. Probing gravitino dark matter with PAMELA and Fermi

    SciTech Connect

    Buchmüller, Wilfried; Takayama, Fumihiro; Ibarra, Alejandro; Tran, David; Shindou, Tetsuo E-mail: alejandro.ibarra@ph.tum.de E-mail: fumihiro.takayama@desy.de

    2009-09-01

    We analyse the cosmic-ray signatures of decaying gravitino dark matter in a model-independent way based on an operator analysis. Thermal leptogenesis and universal boundary conditions at the GUT scale restrict the gravitino mass to be below 600 GeV. Electron and positron fluxes from gravitino decays, together with the standard GALPROP background, cannot explain both the PAMELA positron fraction and the electron + positron flux recently measured by Fermi LAT. For gravitino dark matter, the observed fluxes require astrophysical sources. The measured antiproton flux allows for a sizable contribution of decaying gravitinos to the gamma-ray spectrum, in particular a line at an energy below 300 GeV. Future measurements of the gamma-ray flux will provide important constraints on possible signatures of decaying gravitino dark matter at the LHC.

  6. Search for Dark Matter Satellites Using the FERMI-LAT

    SciTech Connect

    Ackermann, M.; Albert, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Blandford, R.D.; Bloom, E.D.; Bonamente, E.; Borgland, A.W.; Bottacini, E.; Brandt, T.J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Burnett, T.H.; Caliandro, G.A.; Cameron, R.A.; /more authors..

    2012-08-16

    Numerical simulations based on the {Lambda}CDM model of cosmology predict a large number of as yet unobserved Galactic dark matter satellites. We report the results of a Large Area Telescope (LAT) search for these satellites via the {gamma}-ray emission expected from the annihilation of weakly interacting massive particle (WIMP) dark matter. Some dark matter satellites are expected to have hard {gamma}-ray spectra, finite angular extents, and a lack of counterparts at other wavelengths. We sought to identify LAT sources with these characteristics, focusing on {gamma}-ray spectra consistent with WIMP annihilation through the b{bar b} channel. We found no viable dark matter satellite candidates using one year of data, and we present a framework for interpreting this result in the context of numerical simulations to constrain the velocity-averaged annihilation cross section for a conventional 100 GeV WIMP annihilating through the b{bar b} channel.

  7. Search for Dark Matter Satellites Using the Fermi-Lat

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Albert, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Burnett, T. H.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; McEnery, J. E.; Troja, E.

    2012-01-01

    Numerical simulations based on the ACDM model of cosmology predict a large number of as yet unobserved Galactic dark matter satellites. We report the results of a Large Area Telescope (LAT) search for these satellites via the gamma-ray emission expected from the annihilation of weakly interacting massive particle (WIMP) dark matter. Some dark matter satellites are expected to have hard gamma-ray spectra, finite angular extents, and a lack of counterparts at other wavelengths. We sought to identify LAT sources with these characteristics, focusing on gamma-ray spectra consistent with WIMP annihilation through the bb(sup raised bar) channel. We found no viable dark matter satellite candidates using one year of data, and we present a framework for interpreting this result in the context of numerical simulations to constrain the velocity-averaged annihilation cross section for a conventional 100 Ge V WIMP annihilating through the bb(sup raised bar) channel.

  8. Constraining interacting dark energy models with latest cosmological observations

    NASA Astrophysics Data System (ADS)

    Xia, Dong-Mei; Wang, Sai

    2016-08-01

    The local measurement of H0 is in tension with the prediction of ΛCDM model based on the Planck data. This tension may imply that dark energy is strengthened in the late-time Universe. We employ the latest cosmological observations on CMB, BAO, LSS, SNe, H(z) and H0 to constrain several interacting dark energy models. Our results show no significant indications for the interaction between dark energy and dark matter. The H0 tension can be moderately alleviated, but not totally released.

  9. Constraining decaying dark matter with neutron stars

    NASA Astrophysics Data System (ADS)

    Pérez-García, M. Ángeles; Silk, Joseph

    2015-05-01

    The amount of decaying dark matter, accumulated in the central regions in neutron stars together with the energy deposition rate from decays, may set a limit on the neutron star survival rate against transitions to more compact objects provided nuclear matter is not the ultimate stable state of matter and that dark matter indeed is unstable. More generally, this limit sets constraints on the dark matter particle decay time, τχ. We find that in the range of uncertainties intrinsic to such a scenario, masses (mχ /TeV) ≳ 9 ×10-4 or (mχ /TeV) ≳ 5 ×10-2 and lifetimes τχ ≲1055 s and τχ ≲1053 s can be excluded in the bosonic or fermionic decay cases, respectively, in an optimistic estimate, while more conservatively, it decreases τχ by a factor ≳1020. We discuss the validity under which these results may improve with other current constraints.

  10. Gravity Resonance Spectroscopy Constrains Dark Energy and Dark Matter Scenarios

    NASA Astrophysics Data System (ADS)

    Jenke, T.; Cronenberg, G.; Burgdörfer, J.; Chizhova, L. A.; Geltenbort, P.; Ivanov, A. N.; Lauer, T.; Lins, T.; Rotter, S.; Saul, H.; Schmidt, U.; Abele, H.

    2014-04-01

    We report on precision resonance spectroscopy measurements of quantum states of ultracold neutrons confined above the surface of a horizontal mirror by the gravity potential of Earth. Resonant transitions between several of the lowest quantum states are observed for the first time. These measurements demonstrate that Newton's inverse square law of gravity is understood at micron distances on an energy scale of 10-14 eV. At this level of precision, we are able to provide constraints on any possible gravitylike interaction. In particular, a dark energy chameleon field is excluded for values of the coupling constant β >5.8×108 at 95% confidence level (C.L.), and an attractive (repulsive) dark matter axionlike spin-mass coupling is excluded for the coupling strength gsgp>3.7×10-16 (5.3×10-16) at a Yukawa length of λ =20 μm (95% C.L.).

  11. Gravity resonance spectroscopy constrains dark energy and dark matter scenarios.

    PubMed

    Jenke, T; Cronenberg, G; Burgdörfer, J; Chizhova, L A; Geltenbort, P; Ivanov, A N; Lauer, T; Lins, T; Rotter, S; Saul, H; Schmidt, U; Abele, H

    2014-04-18

    We report on precision resonance spectroscopy measurements of quantum states of ultracold neutrons confined above the surface of a horizontal mirror by the gravity potential of Earth. Resonant transitions between several of the lowest quantum states are observed for the first time. These measurements demonstrate that Newton's inverse square law of gravity is understood at micron distances on an energy scale of 10-14  eV. At this level of precision, we are able to provide constraints on any possible gravitylike interaction. In particular, a dark energy chameleon field is excluded for values of the coupling constant β>5.8×108 at 95% confidence level (C.L.), and an attractive (repulsive) dark matter axionlike spin-mass coupling is excluded for the coupling strength gsgp>3.7×10-16 (5.3×10-16) at a Yukawa length of λ=20  μm (95% C.L.). PMID:24785025

  12. Constraining dark energy through the stability of cosmic structures

    SciTech Connect

    Pavlidou, V.; Tetradis, N.; Tomaras, T.N. E-mail: ntetrad@phys.uoa.gr

    2014-05-01

    For a general dark-energy equation of state, we estimate the maximum possible radius of massive structures that are not destabilized by the acceleration of the cosmological expansion. A comparison with known stable structures constrains the equation of state. The robustness of the constraint can be enhanced through the accumulation of additional astrophysical data and a better understanding of the dynamics of bound cosmic structures.

  13. Constraining scalar fields with stellar kinematics and collisional dark matter

    SciTech Connect

    Amaro-Seoane, Pau; Barranco, Juan; Bernal, Argelia; Rezzolla, Luciano E-mail: jbarranc@aei.mpg.de E-mail: rezzolla@aei.mpg.de

    2010-11-01

    The existence and detection of scalar fields could provide solutions to long-standing puzzles about the nature of dark matter, the dark compact objects at the centre of most galaxies, and other phenomena. Yet, self-interacting scalar fields are very poorly constrained by astronomical observations, leading to great uncertainties in estimates of the mass m{sub φ} and the self-interacting coupling constant λ of these fields. To counter this, we have systematically employed available astronomical observations to develop new constraints, considerably restricting this parameter space. In particular, by exploiting precise observations of stellar dynamics at the centre of our Galaxy and assuming that these dynamics can be explained by a single boson star, we determine an upper limit for the boson star compactness and impose significant limits on the values of the properties of possible scalar fields. Requiring the scalar field particle to follow a collisional dark matter model further narrows these constraints. Most importantly, we find that if a scalar dark matter particle does exist, then it cannot account for both the dark-matter halos and the existence of dark compact objects in galactic nuclei.

  14. Constraining particle dark matter using local galaxy distribution

    NASA Astrophysics Data System (ADS)

    Ando, Shin'ichiro; Ishiwata, Koji

    2016-06-01

    It has been long discussed that cosmic rays may contain signals of dark matter. In the last couple of years an anomaly of cosmic-ray positrons has drawn a lot of attentions, and recently an excess in cosmic-ray anti-proton has been reported by AMS-02 collaboration. Both excesses may indicate towards decaying or annihilating dark matter with a mass of around 1–10 TeV . In this article we study the gamma rays from dark matter and constraints from cross correlations with distribution of galaxies, particularly in a local volume. We find that gamma rays due to inverse-Compton process have large intensity, and hence they give stringent constraints on dark matter scenarios in the TeV scale mass regime. Taking the recent developments in modeling astrophysical gamma-ray sources as well as comprehensive possibilities of the final state products of dark matter decay or annihilation into account, we show that the parameter regions of decaying dark matter that are suggested to explain the excesses are excluded. We also discuss the constrains on annihilating scenarios.

  15. A Robust Approach to Constraining Dark Matter from Gamma-Ray Data

    SciTech Connect

    Baxter, Eric J.; Dodelson, Scott; /Fermilab /Chicago U., Astron. Astrophys. Ctr. /Chicago U., KICP

    2011-03-01

    Photons produced in the annihilations of dark matter particles can be detected by gamma-ray telescopes; this technique of indirect detection serves as a cornerstone of the upcoming assault on the dark matter paradigm. The main obstacle to the extraction of information about dark matter from the annihilation photons is the presence of large and uncertain gamma-ray backgrounds. We present a new technique for using gamma-ray data to constrain the properties of dark matter that makes minimal assumptions about the dark matter and the backgrounds. The technique relies on two properties of the expected signal from annihilations of the smooth dark matter component in our Galaxy: (1) it is approximately rotationally symmetric around the axis connecting us to the Galactic center, and (2) variations from the mean signal are uncorrelated from one pixel to the next. We apply this technique to recent data from the Fermi telescope to generate constraints on the dark matter mass and cross section for a variety of annihilation channels. We quantify the uncertainty introduced into our constraints by uncertainties in the halo profile and by the possibility that the halo is triaxial. The resultant constraint, the flux F {le} 4.5 x 10{sup -6} cm{sup -2} s{sup -1} sr{sup -1} for energies between 1 and 100 GeV at an angle 15{sup o} away from the Galactic center, translates into an upper limit on the velocity-weighted annihilation cross section of order 10{sup -25} cm{sup 3} s{sup -1}, depending on the annihilation mode.

  16. CLUES on Fermi-LAT prospects for the extragalactic detection of μνSSM gravitino dark matter

    SciTech Connect

    Gómez-Vargas, G.A.; Muñoz, C.; Yepes, G.; Fornasa, M.; Zandanel, F.; Prada, F.; Cuesta, A.J. E-mail: mattia@iaa.es E-mail: antonio.cuesta@yale.edu E-mail: fprada@iaa.es

    2012-02-01

    The μνSSM is a supersymmetric model that has been proposed to solve the problems generated by other supersymmetric extensions of the standard model of particle physics. Given that R-parity is broken in the μνSSM, the gravitino is a natural candidate for decaying dark matter since its lifetime becomes much longer than the age of the Universe. In this model, gravitino dark matter could be detectable through the emission of a monochromatic gamma ray in a two-body decay. We study the prospects of the Fermi-LAT telescope to detect such monochromatic lines in 5 years of observations of the most massive nearby extragalactic objects. The dark matter halo around the Virgo galaxy cluster is selected as a reference case, since it is associated to a particularly high signal-to-noise ratio and is located in a region scarcely affected by the astrophysical diffuse emission from the galactic plane. The simulation of both signal and background gamma-ray events is carried out with the Fermi Science Tools, and the dark matter distribution around Virgo is taken from a N-body simulation of the nearby extragalactic Universe, with constrained initial conditions provided by the CLUES project. We find that a gravitino with a mass range of 0.6–2 GeV, and with a lifetime range of about 3 × 10{sup 27}–2 × 10{sup 28} s would be detectable by the Fermi-LAT with a signal-to-noise ratio larger than 3. We also obtain that gravitino masses larger than about 4 GeV are already excluded in the μνSSM by Fermi-LAT data of the galactic halo.

  17. Dark Matter Constraints from Observations of 25 Milky Way Satellite Galaxies with the Fermi Large Area Telescope

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Albert, A.; Anderson, B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Bloom, E. D.; Bonamente, E.; Bouvier, A.; Brandt, T. J.; Hays, E.; Perkins, J. S.

    2013-01-01

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in gamma rays, and we present gamma ray flux upper limits between 500MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the annihilation of dark matter particles with masses between 2 GeV and 10TeV into prototypical standard model channels. We find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse gamma ray background modeling, and assumed dark matter density profile.

  18. Dark Matter Annihilation in The Galactic Center As Seen by the Fermi Gamma Ray Space Telescope

    SciTech Connect

    Hooper, Dan; Goodenough, Lisa; /New York U.

    2010-10-01

    We analyze the first two years of data from the Fermi Gamma Ray Space Telescope from the direction of the inner 10{sup o} around the Galactic Center with the intention of constraining, or finding evidence of, annihilating dark matter. We find that the morphology and spectrum of the emission between 1.25{sup o} and 10{sup o} from the Galactic Center is well described by a the processes of decaying pions produced in cosmic ray collisions with gas, and the inverse Compton scattering of cosmic ray electrons in both the disk and bulge of the Inner Galaxy, along with gamma rays from known points sources in the region. The observed spectrum and morphology of the emission within approximately 1.25{sup o} ({approx}175 parsecs) of the Galactic Center, in contrast, cannot be accounted for by these processes or known sources. We find that an additional component of gamma ray emission is clearly present which is highly concentrated around the Galactic Center, but is not point-like in nature. The observed morphology of this component is consistent with that predicted from annihilating dark matter with a cusped (and possibly adiabatically contracted) halo distribution ({rho} {proportional_to} r{sup -1.34{+-}0.04}). The observed spectrum of this component, which peaks at energies between 2-4 GeV (in E{sup 2} units), is well fit by that predicted for a 7.3-9.2 GeV dark matter particle annihilating primarily to tau leptons with a cross section in the range of <{sigma}{nu}> = 3.3 x 10{sup -27} to 1.5 x 10{sup -26} cm{sup 3}/s, depending on how the dark matter distribution is normalized. We discuss other possible sources for this component, but argue that they are unlikely to account for the observed emission.

  19. Constraining Dark Matter Through the Study of Merging Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Dawson, William Anthony

    2013-03-01

    gravitational lensing observations to map and weigh the mass (i.e., dark matter which comprises ~85% of the mass) of the cluster, Sunyaev-Zel'dovich effect and X-ray observations to map and quantify the intracluster gas, and finally radio observations to search for associated radio relics, which had they been observed would have helped constrain the properties of the merger. Using this information in conjunction with a Monte Carlo analysis model I quantify the dynamic properties of the merger, necessary to properly interpret constraints on the SIDM cross-section. I compare the locations of the galaxies, dark matter and gas to constrain the SIDM cross-section. This dissertation presents this work. Findings: We find that the Musket Ball is a merger with total mass of 4.8+3.2-1.5x10 14Msun. However, the dynamic analysis shows that the Musket Ball is being observed 1.1+1.3-0.4 Gyr after first pass through and is much further progressed in its merger process than previously identified dissociative mergers (for example it is 3.4+3.8 -1.4 times further progressed that the Bullet Cluster). By observing that the dark matter is significantly offset from the gas we are able to place an upper limit on the dark matter cross-section of sigmaSIDMm -1DM < 8 cm2g-1. However, we find an that the galaxies appear to be leading the weak lensing (WL) mass distribution by 20.5" (129 kpc at z=0.53) in southern subcluster, which might be expected to occur if dark matter self-interacts. Contrary to this finding though the WL mass centroid appears to be leading the galaxy centroid by 7.4" (47 kpc at z=0.53) in the northern subcluster. Conclusion: The southern offset alone suggests that dark matter self-interacts with ~83% confidence. However, when we account for the observation that the galaxy centroid appears to trail the WL centroid in the north the confidence falls to ~55%. While the SIDM scenario is slightly preferred over the CDM scenario it is not significantly so. Perspectives: The galaxy-dark

  20. Conservative constraints on dark matter from the Fermi-LAT isotropic diffuse gamma-ray background spectrum

    SciTech Connect

    Abazajian, Kevork N.; Agrawal, Prateek; Chacko, Zackaria; Kilic, Can E-mail: apr@umd.edu E-mail: kilic@physics.rutgers.edu

    2010-11-01

    We examine the constraints on final state radiation from Weakly Interacting Massive Particle (WIMP) dark matter candidates annihilating into various standard model final states, as imposed by the measurement of the isotropic diffuse gamma-ray background by the Large Area Telescope aboard the Fermi Gamma-Ray Space Telescope. The expected isotropic diffuse signal from dark matter annihilation has contributions from the local Milky Way (MW) as well as from extragalactic dark matter. The signal from the MW is very insensitive to the adopted dark matter profile of the halos, and dominates the signal from extragalactic halos, which is sensitive to the low mass cut-off of the halo mass function. We adopt a conservative model for both the low halo mass survival cut-off and the substructure boost factor of the Galactic and extragalactic components, and only consider the primary final state radiation. This provides robust constraints which reach the thermal production cross-section for low mass WIMPs annihilating into hadronic modes. We also reanalyze limits from HESS observations of the Galactic Ridge region using a conservative model for the dark matter halo profile. When combined with the HESS constraint, the isotropic diffuse spectrum rules out all interpretations of the PAMELA positron excess based on dark matter annihilation into two lepton final states. Annihilation into four leptons through new intermediate states, although constrained by the data, is not excluded.

  1. Indirect searches for dark matter with the Fermi large area telescope

    DOE PAGESBeta

    Albert, Andrea

    2015-03-24

    There is overwhelming evidence that non-baryonic dark matter constitutes ~ 27% of the energy density of the Universe. Weakly Interacting Massive Particles (WIMPs) are promising dark matter candidates that may produce γ rays via annihilation or decay detectable by the Fermi Large Area Telescope (LAT). A detection of WIMPs would also indicate the existence of physics beyond the Standard Model. We present recent results from the two cleanest indirect WIMP searches by the Fermi-LAT Collaboration: searches for γ-ray spectral lines and γ-ray emission associated with Milky Way dwarf spheroidal satellite galaxies.

  2. Indirect searches for dark matter with the Fermi large area telescope

    SciTech Connect

    Albert, Andrea

    2015-03-24

    There is overwhelming evidence that non-baryonic dark matter constitutes ~ 27% of the energy density of the Universe. Weakly Interacting Massive Particles (WIMPs) are promising dark matter candidates that may produce γ rays via annihilation or decay detectable by the Fermi Large Area Telescope (LAT). A detection of WIMPs would also indicate the existence of physics beyond the Standard Model. We present recent results from the two cleanest indirect WIMP searches by the Fermi-LAT Collaboration: searches for γ-ray spectral lines and γ-ray emission associated with Milky Way dwarf spheroidal satellite galaxies.

  3. The Search for Dark Matter with the Fermi Gamma Ray Space Telescope

    SciTech Connect

    Bloom, Elliott

    2011-03-30

    The Fermi Gamma-Ray Space Telescope has been scanning the gamma ray sky since it was launched by NASA in June 2008 and has a mission lifetime goal of 10 years. Largely due to our particle physics heritage, one of the main physics topics being studied by the Fermi LAT Collaboration is the search for dark matter via indirect detection. My talk will review the progress of these studies, something on how the LAT detector enables them, and expectations for the future. I will discuss both gamma-ray and (electron + positron) searches for dark matter, and some resulting theoretical implications.

  4. Constraints on the annihilation cross section of dark matter particles from anisotropies in the diffuse gamma-ray background measured with Fermi-LAT

    NASA Astrophysics Data System (ADS)

    Ando, Shin'ichiro; Komatsu, Eiichiro

    2013-06-01

    Annihilation of dark matter particles in cosmological halos (including the halo of the Milky Way) contributes to the diffuse gamma-ray background (DGRB). As this contribution will appear anisotropic in the sky, one can use the angular power spectrum of anisotropies in the DGRB to constrain the properties of dark matter particles. By comparing the updated analytic model of the angular power spectrum of the DGRB from dark matter annihilation with the power spectrum recently measured from the 22-month data of the Fermi Large Area Telescope (LAT), we place upper limits on the annihilation cross section of dark matter particles as a function of dark matter masses. We find that the current data exclude ⟨σv⟩≳10-25cm3s-1 for annihilation into bb¯ at the dark matter mass of 10 GeV, which is a factor of 3 times larger than the canonical cross section. The limits are weaker for larger dark matter masses. The limits can be improved further with more Fermi-LAT data as well as by using the power spectrum at lower multipoles (ℓ≲150), which are currently not used due to a potential Galactic foreground contamination.

  5. Dark matter subhalos and unidentified sources in the Fermi 3FGL source catalog

    NASA Astrophysics Data System (ADS)

    Schoonenberg, Djoeke; Gaskins, Jennifer; Bertone, Gianfranco; Diemand, Jürg

    2016-05-01

    If dark matter consists of weakly interacting massive particles (WIMPs), dark matter subhalos in the Milky Way could be detectable as gamma-ray point sources due to WIMP annihilation. In this work, we perform an updated study of the detectability of dark matter subhalos as gamma-ray sources with the Fermi Large Area Telescope (Fermi LAT). We use the results of the Via Lactea II simulation, scaled to the Planck 2015 cosmological parameters, to predict the local dark matter subhalo distribution. Under optimistic assumptions for the WIMP parameters—a 40 GeV particle annihilating to bbar b with a thermal cross-section, as required to explain the Galactic center GeV excess—we predict that at most ~ 10 subhalos might be present in the third Fermi LAT source catalog (3FGL). This is a smaller number than has been predicted by prior studies, and we discuss the origin of this difference. We also compare our predictions for the detectability of subhalos with the number of subhalo candidate sources in 3FGL, and derive upper limits on the WIMP annihilation cross-section as a function of the particle mass. If a dark matter interpretation could be excluded for all 3FGL sources, our constraints would be competitive with those found by indirect searches using other targets, such as known Milky Way satellite galaxies.

  6. Constraints on decaying dark matter from Fermi observations of nearby galaxies and clusters

    SciTech Connect

    Dugger, Leanna; Profumo, Stefano; Jeltema, Tesla E. E-mail: tesla@ucolick.org

    2010-12-01

    We analyze the impact of Fermi gamma-ray observations (primarily non-detections) of selected nearby galaxies, including dwarf spheroidals, and of clusters of galaxies on decaying dark matter models. We show that the fact that galaxy clusters do not shine in gamma rays puts the most stringent limits available to-date on the lifetime of dark matter particles for a wide range of particle masses and decay final states. In particular, our results put strong constraints on the possibility of ascribing to decaying dark matter both the increasing positron fraction reported by PAMELA and the high-energy feature in the electron-positron spectrum measured by Fermi. Observations of nearby dwarf galaxies and of the Andromeda Galaxy (M31) do not provide as strong limits as those from galaxy clusters, while still improving on previous constraints in some cases.

  7. Secluded singlet fermionic dark matter driven by the Fermi gamma-ray excess

    NASA Astrophysics Data System (ADS)

    Kim, Yeong Gyun; Lee, Kang Young; Park, Chan Beom; Shin, Seodong

    2016-04-01

    We examine the possibility that the dark matter (DM) interpretation of the GeV scale Fermi gamma-ray excess at the Galactic center can be realized in a specific framework-secluded singlet fermionic dark matter model with small mixing between the dark and Standard Model sectors. Within this framework, it is shown that the DM annihilation into a bottom-quark pair, Higgs pair, and new scalar pair, shown to give good fits to the Fermi gamma-ray data in various model independent studies, can be successfully reproduced in our model. Moreover, unavoidable constraints from the antiproton ratio by PAMELA and AMS-02, the gamma-ray emission from the dwarf spheroidal galaxies by the Fermi-LAT, and the Higgs measurements by the LHC are also considered. Then, we find our best-fit parameters for the Fermi gamma-ray excess without conflicting other experimental and cosmological constraints if uncertainties on the DM density profile of the Milky Way Galaxy are taken into account. Successfully surviving parameters are benchmark points for future study on the collider signals.

  8. Constraints on the Galactic Halo Dark Matter from Fermi-LAT Diffuse Measurements

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Ajello, M.; Atwood, W. B.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Brandt, Theresa J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P A.; Casandjian, J. M.; Cecchi, C.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cuoco, A.; Guiriec, Sylvain Germain; McEnery, Julie E.; Scargle. J. D.; Troja, Eleonora

    2012-01-01

    We have performed an analysis of the diffuse gamma-ray emission with the Fermi Large Area Telescope (LAT) in the Milky Way halo region, searching for a signal from dark matter annihilation or decay. In the absence of a robust dark matter signal, constraints are presented. We consider both gamma rays produced directly in the dark matter annihilation/decay and produced by inverse Compton scattering of the e+/e- produced in the annihilation/decay. Conservative limits are derived requiring that the dark matter signal does not exceed the observed diffuse gamma-ray emission. A second set of more stringent limits is derived based on modeling the foreground astrophysical diffuse emission using the GALPROP code. Uncertainties in the height of the diffusive cosmic-ray halo, the distribution of the cosmic-ray sources in the Galaxy, the index of the injection cosmic-ray electron spectrum, and the column density of the interstellar gas are taken into account using a profile likelihood formalism, while the parameters governing the cosmic-ray propagation have been derived from fits to local cosmic-ray data. The resulting limits impact the range of particle masses over which dark matter thermal production in the early universe is possible, and challenge the interpretation of the PAMELA/Fermi-LAT cosmic ray anomalies as the annihilation of dark matter.

  9. Constraining dark matter annihilation with the isotropic γ-ray background: Updated limits and future potential

    NASA Astrophysics Data System (ADS)

    Bringmann, Torsten; Calore, Francesca; Di Mauro, Mattia; Donato, Fiorenza

    2014-01-01

    The nature of the isotropic γ-ray background (IGRB) measured by the Large Area Telescope (LAT) on the Fermi γ-ray space telescope (Fermi) remains partially unexplained. Non-negligible contributions may originate from extragalactic populations of unresolved sources such as blazars, star-forming galaxies or galactic millisecond pulsars. A recent prediction of the diffuse γ-ray emission from active galactic nuclei (AGN) with a large viewing angle with respect to the line of sight has demonstrated that this faint but numerous population is also expected to contribute significantly to the total IGRB intensity. A more exotic contribution to the IGRB invokes the pair annihilation of dark matter (DM) weakly interacting massive particles (WIMPs) into γ rays. In this work, we evaluate the room left for galactic DM at high latitudes (>10∘) by including photons from both prompt emission and inverse Compton scattering, emphasizing the impact of the newly discovered contribution from misaligned AGN (MAGN) for such an analysis. Summing up all significant galactic and extragalactic components of the IGRB, we find that an improved understanding of the associated astrophysical uncertainties is still mandatory to put stringent bounds on thermally produced DM. On the other hand, we also demonstrate that the IGRB has the potential to be one of the most competitive future ways to test the DM WIMP hypothesis, once the present uncertainties are even slightly reduced. In fact, if MAGN contribute even at 90% of the maximal level consistent with our current understanding, thermally produced WIMPs would be severely constrained as DM candidates for masses up to several TeV.

  10. Constraining properties of dark matter particles using astrophysical data

    NASA Astrophysics Data System (ADS)

    Iakubovskyi, Dmytro

    2013-02-01

    A microscopic origin of dark matter phenomenon is the most plausible hypothesis to explain the mystery of dark matter. The dark matter particle hypothesis necessarily implies an extension of the Standard Model. In this thesis, we undertook a systematic model-independent program of studying the properties of decaying dark matter. By analyzing the experimental data for dwarf spheroidal galaxies it was shown that the X-ray energy range is a preferred region when searching for radiatively decaying dark matter. By analyzing dark matter distributions in different types of galaxies and in galaxy clusters we show that the expected dark matter signal increases slowly with the mass of the object. Therefore, dwarf and spiral galaxies are the observational targets with the optimal signal-to-noise ratio. To probe the theoretically interesting regions of particle physics models we performed a combined analysis of a very large dataset of archival XMM-Newton observations of galaxies. Finally, we discussed an ultimate way to probe the whole parameter space of minimal models of decaying dark matter. We argue that a new X-ray telescope with the narrow energy resolution (comparable to internal width of the line) and large field-of-view is required.

  11. Constraining inflationary dark matter in the luminogenesis model

    SciTech Connect

    Hung, Pham Q.; Ludwick, Kevin J.

    2015-09-09

    Using renormalization-group flow and cosmological constraints on inflation models, we exploit a unique connection between cosmological inflation and the dynamical mass of dark matter particles in the luminogenesis model, a unification model with the gauge group SU(3){sub C}×SU(6)×U(1){sub Y}, which breaks to the Standard Model with an extra gauge group for dark matter when the inflaton rolls into the true vacuum. In this model, inflaton decay gives rise to dark matter, which in turn decays to luminous matter in the right proportion that agrees with cosmological data. Some attractive features of this model include self-interacting dark matter, which may resolve the problems of dwarf galaxy structures and dark matter cusps at the centers of galaxies.

  12. Decaying dark matter in light of the PAMELA and Fermi LAT data

    SciTech Connect

    Ibarra, Alejandro; Tran, David; Weniger, Christoph E-mail: david.tran@ph.tum.de

    2010-01-01

    A series of experiments measuring high-energy cosmic rays have recently reported strong indications for the existence of an excess of high-energy electrons and positrons. If interpreted in terms of the decay of dark matter particles, the PAMELA measurements of the positron fraction and the Fermi LAT measurements of the total electron-plus-positron flux restrict the possible decaying dark matter scenarios to a few cases. Analyzing different decay channels in a model-independent manner, and adopting a conventional diffusive reacceleration model for the background fluxes of electrons and positrons, we identify some promising scenarios of dark matter decay and calculate the predictions for the diffuse extragalactic gamma-ray flux, including the contributions from inverse Compton scattering with the interstellar radiation field.

  13. Dark soliton pair of ultracold Fermi gases for a generalized Gross-Pitaevskii equation model.

    PubMed

    Wang, Ying; Zhou, Yu; Zhou, Shuyu; Zhang, Yongsheng

    2016-07-01

    We present the theoretical investigation of dark soliton pair solutions for one-dimensional as well as three-dimensional generalized Gross-Pitaevskii equation (GGPE) which models the ultracold Fermi gas during Bardeen-Cooper-Schrieffer-Bose-Einstein condensates crossover. Without introducing any integrability constraint and via the self-similar approach, the three-dimensional solution of GGPE is derived based on the one-dimensional dark soliton pair solution, which is obtained through a modified F-expansion method combined with a coupled modulus-phase transformation technique. We discovered the oscillatory behavior of the dark soliton pair from the theoretical results obtained for the three-dimensional case. The calculated period agrees very well with the corresponding reported experimental result [Weller et al., Phys. Rev. Lett. 101, 130401 (2008)PRLTAO0031-900710.1103/PhysRevLett.101.130401], demonstrating the applicability of the theoretical treatment presented in this work. PMID:27575141

  14. Dark soliton pair of ultracold Fermi gases for a generalized Gross-Pitaevskii equation model

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Zhou, Yu; Zhou, Shuyu; Zhang, Yongsheng

    2016-07-01

    We present the theoretical investigation of dark soliton pair solutions for one-dimensional as well as three-dimensional generalized Gross-Pitaevskii equation (GGPE) which models the ultracold Fermi gas during Bardeen-Cooper-Schrieffer-Bose-Einstein condensates crossover. Without introducing any integrability constraint and via the self-similar approach, the three-dimensional solution of GGPE is derived based on the one-dimensional dark soliton pair solution, which is obtained through a modified F -expansion method combined with a coupled modulus-phase transformation technique. We discovered the oscillatory behavior of the dark soliton pair from the theoretical results obtained for the three-dimensional case. The calculated period agrees very well with the corresponding reported experimental result [Weller et al., Phys. Rev. Lett. 101, 130401 (2008), 10.1103/PhysRevLett.101.130401], demonstrating the applicability of the theoretical treatment presented in this work.

  15. Constraining warm dark matter with cosmic shear power spectra

    SciTech Connect

    Markovic, Katarina; Weller, Jochen; Bridle, Sarah; Slosar, Anže E-mail: sarah.bridle@ucl.ac.uk E-mail: jochen.weller@usm.lmu.de

    2011-01-01

    We investigate potential constraints from cosmic shear on the dark matter particle mass, assuming all dark matter is made up of light thermal relic particles. Given the theoretical uncertainties involved in making cosmological predictions in such warm dark matter scenarios we use analytical fits to linear warm dark matter power spectra and compare (i) the halo model using a mass function evaluated from these linear power spectra and (ii) an analytical fit to the non-linear evolution of the linear power spectra. We optimistically ignore the competing effect of baryons for this work. We find approach (ii) to be conservative compared to approach (i). We evaluate cosmological constraints using these methods, marginalising over four other cosmological parameters. Using the more conservative method we find that a Euclid-like weak lensing survey together with constraints from the Planck cosmic microwave background mission primary anisotropies could achieve a lower limit on the particle mass of 2.5 keV.

  16. Fermi-LAT constraints on dark matter annihilation cross section from observations of the Fornax cluster

    SciTech Connect

    Ando, Shin'ichiro; Nagai, Daisuke E-mail: daisuke.nagai@yale.edu

    2012-07-01

    We analyze 2.8-yr data of 1–100 GeV photons for clusters of galaxies, collected with the Large Area Telescope onboard the Fermi satellite. By analyzing 49 nearby massive clusters located at high Galactic latitudes, we find no excess gamma-ray emission towards directions of the galaxy clusters. Using flux upper limits, we show that the Fornax cluster provides the most stringent constraints on the dark matter annihilation cross section. Stacking a large sample of nearby clusters does not help improve the limit for most dark matter models. This suggests that a detailed modeling of the Fornax cluster is important for setting robust limits on the dark matter annihilation cross section based on clusters. We therefore perform the detailed mass modeling and predict the expected dark matter annihilation signals from the Fornax cluster, by taking into account effects of dark matter contraction and substructures. By modeling the mass distribution of baryons (stars and gas) around a central bright elliptical galaxy, NGC 1399, and using a modified contraction model motivated by numerical simulations, we show that the dark matter contraction boosts the annihilation signatures by a factor of 4. For dark matter masses around 10 GeV, the upper limit obtained on the annihilation cross section times relative velocity is (σν)∼<(2–3) × 10{sup −25} cm{sup 3} s{sup −1}, which is within a factor of 10 from the value required to explain the dark matter relic density. This effect is more robust than the annihilation boost due to substructure, and it is more important unless the mass of the smallest subhalos is much smaller than that of the Sun.

  17. Constraining Dark Matter Interactions with Pseudoscalar and Scalar Mediators Using Collider Searches for Multijets plus Missing Transverse Energy.

    PubMed

    Buchmueller, Oliver; Malik, Sarah A; McCabe, Christopher; Penning, Bjoern

    2015-10-30

    The monojet search, looking for events involving missing transverse energy (E_{T}) plus one or two jets, is the most prominent collider dark matter search. We show that multijet searches, which look for E_{T} plus two or more jets, are significantly more sensitive than the monojet search for pseudoscalar- and scalar-mediated interactions. We demonstrate this in the context of a simplified model with a pseudoscalar interaction that explains the excess in GeV energy gamma rays observed by the Fermi Large Area Telescope. We show that multijet searches already constrain a pseudoscalar interpretation of the excess in much of the parameter space where the mass of the mediator M_{A} is more than twice the dark matter mass m_{DM}. With the forthcoming run of the Large Hadron Collider at higher energies, the remaining regions of the parameter space where M_{A}>2m_{DM} will be fully explored. Furthermore, we highlight the importance of complementing the monojet final state with multijet final states to maximize the sensitivity of the search for the production of dark matter at colliders. PMID:26565458

  18. FERMI-LAT SENSITIVITY TO DARK MATTER ANNIHILATION IN VIA LACTEA II SUBSTRUCTURE

    SciTech Connect

    Anderson, Brandon; Johnson, Robert P.; Madau, Piero; Kuhlen, Michael; Diemand, Juerg E-mail: mqk@astro.berkeley.ed

    2010-08-01

    We present a study of the ability of the Fermi Gamma-ray Space Telescope to detect dark matter (DM) annihilation signals from the Galactic subhalos predicted by the Via Lactea II N-body simulation. We implement an improved formalism for estimating the boost factor needed to account for the effect of DM clumping on scales below the resolution of the simulation, and we incorporate a detailed Monte Carlo simulation of the response of the Fermi-LAT, including a simulation of its all-sky observing mode integrated over a 10 year mission. We find that for WIMP masses up to about 150 GeV c {sup -2} in standard supersymmetric models with ({sigma}v) = 3 x 10{sup -26} cm{sup 3} s{sup -1}, a few subhalos could be detectable with >5 standard deviation significance and would likely deviate significantly from the appearance of a point source.

  19. EVIDENCE FOR INDIRECT DETECTION OF DARK MATTER FROM GALAXY CLUSTERS IN FERMI {gamma}-RAY DATA

    SciTech Connect

    Hektor, A.; Raidal, M.; Tempel, E. E-mail: martti.raidal@cern.ch

    2013-01-10

    Using the Fermi Large Area Telescope (LAT) we search for spectral features in {gamma}-rays coming from regions corresponding to the 18 brightest nearby galaxy clusters determined by the magnitude of their signal line-of-sight integrals. We observe a double-peak-like excess over the diffuse power-law background at photon energies of 110 GeV and 130 GeV with a global statistical significance of up to 3.6{sigma}, independently confirming earlier claims of the same excess from the Galactic center. Interpreting this result as a signal of dark matter annihilations to two monochromatic photon channels in galaxy cluster halos, and fixing the annihilation cross-section from the Galactic center data, we determine the annihilation boost factor due to dark matter subhalos from the data. Our results contribute to a discrimination of the dark matter annihilations from astrophysical processes and from systematic detector effects, offering them as possible explanations for the Fermi-LAT excess.

  20. Hunting dark matter gamma-ray lines with the Fermi LAT

    NASA Astrophysics Data System (ADS)

    Vertongen, Gilles; Weniger, Christoph

    2011-05-01

    Monochromatic photons could be produced in the annihilation or decay of dark matter particles. At high energies, the search for such line features in the cosmic gamma-ray spectrum is essentially background free because plausible astrophysical processes are not expected to produce such a signal. The observation of a gamma-ray line would hence be a `smoking-gun' signature for dark matter, making the search for such signals particularly attractive. Among the different dark matter models predicting gamma-ray lines, the local supersymmetric extension of the standard model with small R-parity violation and gravitino LSP is of particular interest because it provides a framework where primordial nucleosynthesis, gravitino dark matter and thermal leptogenesis are naturally consistent. Using the two-years Fermi LAT data, we present a dedicated search for gamma-ray lines coming from dark matter annihilation or decay in the Galactic halo. Taking into account the full detector response, and using a binned profile likelihood method, we search for significant line features in the energy spectrum of the diffuse flux observed in different regions of the sky. No evidence for a line signal at the 5σ level is found for photon energies between 1 and 300 GeV, and conservative bounds on dark matter decay rates and annihilation cross sections are presented. Implications for gravitino dark matter in presence of small R-parity violation are discussed, as well as the impact of our results on the prospect for seeing long-lived neutralinos or staus at the LHC.

  1. Hunting dark matter gamma-ray lines with the Fermi LAT

    SciTech Connect

    Vertongen, Gilles; Weniger, Christoph E-mail: weniger@mppmu.mpg.de

    2011-05-01

    Monochromatic photons could be produced in the annihilation or decay of dark matter particles. At high energies, the search for such line features in the cosmic gamma-ray spectrum is essentially background free because plausible astrophysical processes are not expected to produce such a signal. The observation of a gamma-ray line would hence be a 'smoking-gun' signature for dark matter, making the search for such signals particularly attractive. Among the different dark matter models predicting gamma-ray lines, the local supersymmetric extension of the standard model with small R-parity violation and gravitino LSP is of particular interest because it provides a framework where primordial nucleosynthesis, gravitino dark matter and thermal leptogenesis are naturally consistent. Using the two-years Fermi LAT data, we present a dedicated search for gamma-ray lines coming from dark matter annihilation or decay in the Galactic halo. Taking into account the full detector response, and using a binned profile likelihood method, we search for significant line features in the energy spectrum of the diffuse flux observed in different regions of the sky. No evidence for a line signal at the 5σ level is found for photon energies between 1 and 300 GeV, and conservative bounds on dark matter decay rates and annihilation cross sections are presented. Implications for gravitino dark matter in presence of small R-parity violation are discussed, as well as the impact of our results on the prospect for seeing long-lived neutralinos or staus at the LHC.

  2. COnstrain Dark Energy with X-ray (CODEX) clusters

    NASA Astrophysics Data System (ADS)

    Finoguenov, Alexis; SDSS Team; Cfht Team; Carma Team

    2012-09-01

    We describe the construction and follow-up observations of the most massive clusters in the Universe, selected in the SDSS-III survey using RASS data down to an unprecedented flux limit of -13 dex. In application to the cosmology studies, we demonstrate that we will achieve a 3% constraint on the dark energy equation of state, and in a combination with BOSS BAO measurement reach a FoM of 160.

  3. Constraining competing models of dark energy with cosmological observations

    NASA Astrophysics Data System (ADS)

    Pavlov, Anatoly

    The last decade of the 20th century was marked by the discovery of the accelerated expansion of the universe. This discovery puzzles physicists and has yet to be fully understood. It contradicts the conventional theory of gravity, i.e. Einstein's General Relativity (GR). According to GR, a universe filled with dark matter and ordinary matter, i.e. baryons, leptons, and photons, can only expand with deceleration. Two approaches have been developed to study this phenomenon. One attempt is to assume that GR might not be the correct description of gravity, hence a modified theory of gravity has to be developed to account for the observed acceleration of the universe's expansion. This approach is known as the "Modified Gravity Theory". The other way is to assume that the energy budget of the universe has one more component which causes expansion of space with acceleration on large scales. Dark Energy (DE) was introduced as a hypothetical type of energy homogeneously filling the entire universe and very weakly or not at all interacting with ordinary and dark matter. Observational data suggest that if DE is assumed then its contribution to the energy budget of the universe at the current epoch should be about 70% of the total energy density of the universe. In the standard cosmological model a DE term is introduced into the Einstein GR equations through the cosmological constant, a constant in time and space, and proportional to the metric tensor gmunu. While this model so far fits most available observational data, it has some significant conceptual shortcomings. Hence there are a number of alternative cosmological models of DE in which the dark energy density is allowed to vary in time and space.

  4. Dark Matter Searches with the Fermi-LAT in the Direction of Dwarf Spheroidals

    SciTech Connect

    Wood, Matthew; Anderson, Brandon; Drlica-Wagner, Alex; Cohen-Tanugi, Johann; Conrad, Jan

    2015-07-13

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma-ray observations of Milky Way dwarf spheroidal satellite galaxies based on 6 years of Fermi Large Area Telescope data processed with the new Pass 8 reconstruction and event-level analysis. None of the dwarf galaxies are significantly detected in gamma rays, and we present upper limits on the dark matter annihilation cross section from a combined analysis of the 15 most promising dwarf galaxies. The constraints derived are among the strongest to date using gamma rays, and lie below the canonical thermal relic cross section for WIMPs of mass ≲ 100GeV annihilating via the bb-bar and τ⁺τ⁻ channels.

  5. UV completions of magnetic inelastic and Rayleigh dark matter for the Fermi Line(s)

    NASA Astrophysics Data System (ADS)

    Weiner, Neal; Yavin, Itay

    2013-01-01

    Models that seek to produce a line at ˜130GeV as possibly present in the Fermi data face a number of phenomenological hurdles, not the least of which is achieving the high cross section into γγ required. A simple explanation is a fermionic dark matter particle that couples to photons through loops of charged messengers. We study the size of the dimension-5 dipole (for a pseudo-Dirac state) and dimension-7 Rayleigh operators in such a model, including all higher order corrections in 1/Mmess. Such corrections tend to enhance the annihilation rates beyond the naive effective operators. We find that while freeze-out is generally dominated by the dipole, the present-day gamma-ray signatures are dominated by the Rayleigh operator, except at the most strongly coupled points, motivating a hybrid approach. With this, the magnetic inelastic dark matter scenario provides a successful explanation of the lines at only moderately strong coupling. We also consider the pure Majorana weakly interacting massive particle, where both freeze-out and the Fermi lines can be explained, but only at very strong coupling with light (˜200-300GeV) messengers. In both cases there is no conflict with nonobservation of continuum photons.

  6. Examining the Fermi-LAT third source catalog in search of dark matter subhalos

    DOE PAGESBeta

    Bertoni, Bridget; Hooper, Dan; Linden, Tim

    2015-12-17

    Dark matter annihilations taking place in nearby subhalos could appear as gamma-ray sources without detectable counterparts at other wavelengths. In this study, we consider the collection of unassociated gamma-ray sources reported by the Fermi Collaboration in an effort to identify the most promising dark matter subhalo candidates. While we identify 24 bright, high-latitude, non-variable sources with spectra that are consistent with being generated by the annihilations of ~ 20–70 GeV dark matter particles (assuming annihilations to bbar b), it is not possible at this time to distinguish these sources from radio-faint gamma-ray pulsars. Deeper multi-wavelength observations will be essential tomore » clarify the nature of these sources. It is notable that we do not find any such sources that are well fit by dark matter particles heavier than ~100 GeV. We also study the angular distribution of the gamma-rays from this set of subhalo candidates, and find that the source 3FGL J2212.5+0703 prefers a spatially extended profile (of width ~ 0.15°) over that of a point source, with a significance of 4.2σ (3.6σ after trials factor). Although not yet definitive, this bright and high-latitude gamma-ray source is well fit as a nearby subhalo of mχ ≃ 20–50 GeV dark matter particles (annihilating to bb¯) and merits further multi-wavelength investigation. As a result, based on the subhalo distribution predicted by numerical simulations, we derive constraints on the dark matter annihilation cross section that are competitive to those resulting from gamma-ray observations of dwarf spheroidal galaxies, the Galactic Center, and the extragalactic gamma-ray background.« less

  7. Examining the Fermi-LAT third source catalog in search of dark matter subhalos

    SciTech Connect

    Bertoni, Bridget; Hooper, Dan; Linden, Tim

    2015-12-17

    Dark matter annihilations taking place in nearby subhalos could appear as gamma-ray sources without detectable counterparts at other wavelengths. In this study, we consider the collection of unassociated gamma-ray sources reported by the Fermi Collaboration in an effort to identify the most promising dark matter subhalo candidates. While we identify 24 bright, high-latitude, non-variable sources with spectra that are consistent with being generated by the annihilations of ~ 20–70 GeV dark matter particles (assuming annihilations to bbar b), it is not possible at this time to distinguish these sources from radio-faint gamma-ray pulsars. Deeper multi-wavelength observations will be essential to clarify the nature of these sources. It is notable that we do not find any such sources that are well fit by dark matter particles heavier than ~100 GeV. We also study the angular distribution of the gamma-rays from this set of subhalo candidates, and find that the source 3FGL J2212.5+0703 prefers a spatially extended profile (of width ~ 0.15°) over that of a point source, with a significance of 4.2σ (3.6σ after trials factor). Although not yet definitive, this bright and high-latitude gamma-ray source is well fit as a nearby subhalo of mχ ≃ 20–50 GeV dark matter particles (annihilating to bb¯) and merits further multi-wavelength investigation. As a result, based on the subhalo distribution predicted by numerical simulations, we derive constraints on the dark matter annihilation cross section that are competitive to those resulting from gamma-ray observations of dwarf spheroidal galaxies, the Galactic Center, and the extragalactic gamma-ray background.

  8. Sensitivity projections for dark matter searches with the Fermi large area telescope

    NASA Astrophysics Data System (ADS)

    Charles, E.; Sánchez-Conde, M.; Anderson, B.; Caputo, R.; Cuoco, A.; Di Mauro, M.; Drlica-Wagner, A.; Gomez-Vargas, G. A.; Meyer, M.; Tibaldo, L.; Wood, M.; Zaharijas, G.; Zimmer, S.; Ajello, M.; Albert, A.; Baldini, L.; Bechtol, K.; Bloom, E. D.; Ceraudo, F.; Cohen-Tanugi, J.; Digel, S. W.; Gaskins, J.; Gustafsson, M.; Mirabal, N.; Razzano, M.

    2016-06-01

    The nature of dark matter is a longstanding enigma of physics; it may consist of particles beyond the Standard Model that are still elusive to experiments. Among indirect search techniques, which look for stable products from the annihilation or decay of dark matter particles, or from axions coupling to high-energy photons, observations of the γ-ray sky have come to prominence over the last few years, because of the excellent sensitivity of the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope mission. The LAT energy range from 20 meV to above 300 GeV is particularly well suited for searching for products of the interactions of dark matter particles. In this report we describe methods used to search for evidence of dark matter with the LAT, and review the status of searches performed with up to six years of LAT data. We also discuss the factors that determine the sensitivities of these searches, including the magnitudes of the signals and the relevant backgrounds, considering both statistical and systematic uncertainties. We project the expected sensitivities of each search method for 10 and 15 years of LAT data taking. In particular, we find that the sensitivity of searches targeting dwarf galaxies, which provide the best limits currently, will improve faster than the square root of observing time. Current LAT limits for dwarf galaxies using six years of data reach the thermal relic level for masses up to 120 GeV for the b b ¯ annihilation channel for reasonable dark matter density profiles. With projected discoveries of additional dwarfs, these limits could extend to about 250 GeV. With as much as 15 years of LAT data these searches would be sensitive to dark matter annihilations at the thermal relic cross section for masses to greater than 400 GeV (200 GeV) in the b b ¯ (τ+τ-) annihilation channels.

  9. Constraining the Drag Coefficients of Meteors in Dark Flight

    NASA Technical Reports Server (NTRS)

    Carter, R. T.; Jandir, P. S.; Kress, M. E.

    2011-01-01

    Based on data in the aeronautics literature, we have derived functions for the drag coefficients of spheres and cubes as a function of Mach number. Experiments have shown that spheres and cubes exhibit an abrupt factor-of-two decrease in the drag coefficient as the object slows through the transonic regime. Irregularly shaped objects such as meteorites likely exhibit a similar trend. These functions are implemented in an otherwise simple projectile motion model, which is applicable to the non-ablative dark flight of meteors (speeds less than .+3 km/s). We demonstrate how these functions may be used as upper and lower limits on the drag coefficient of meteors whose shape is unknown. A Mach-dependent drag coefficient is potentially important in other planetary and astrophysical situations, for instance, in the core accretion scenario for giant planet formation.

  10. Constraining Dark Energy in Table-Top Quantum Experiments

    NASA Astrophysics Data System (ADS)

    Mueller, Holger

    If dark energy is a light scalar field, it might interact with normal matter. The interactions, however, are suppressed in the leading models, which are thus compatible with current cosmological observations as well as solar-system and laboratory studies. Such suppression typically relies on the scalar's interaction with macroscopic amounts of ordinary matter but can be bypassed by studying the interaction with individual particles. Using an atom interferometer, we have placed tight constraints on so-called chameleon models, ruling out interaction parameters smaller than 2 . 3 ×10-5 , while M ~ 1 or larger would lead to conflict with macroscopic experiments. In order to close this gap, we have already increased the sensitivity hundredfold and are expecting a new constraint soon. Purpose-built experiments in the lab or on the international space station will completely close the gap and rule out chameleons and other theories such as symmetrons or f (R) gravity.

  11. Constraining dark sector perturbations II: ISW and CMB lensing tomography

    NASA Astrophysics Data System (ADS)

    Soergel, B.; Giannantonio, T.; Weller, J.; Battye, R. A.

    2015-02-01

    Any Dark Energy (DE) or Modified Gravity (MG) model that deviates from a cosmological constant requires a consistent treatment of its perturbations, which can be described in terms of an effective entropy perturbation and an anisotropic stress. We have considered a recently proposed generic parameterisation of DE/MG perturbations and compared it to data from the Planck satellite and six galaxy catalogues, including temperature-galaxy (Tg), CMB lensing-galaxy (varphi g) and galaxy-galaxy (gg) correlations. Combining these observables of structure formation with tests of the background expansion allows us to investigate the properties of DE/MG both at the background and the perturbative level. Our constraints on DE/MG are mostly in agreement with the cosmological constant paradigm, while we also find that the constraint on the equation of state w (assumed to be constant) depends on the model assumed for the perturbation evolution. We obtain w=-0.92+0.20-0.16 (95% CL; CMB+gg+Tg) in the entropy perturbation scenario; in the anisotropic stress case the result is w=-0.86+0.17-0.16. Including the lensing correlations shifts the results towards higher values of w. If we include a prior on the expansion history from recent Baryon Acoustic Oscillations (BAO) measurements, we find that the constraints tighten closely around w=-1, making it impossible to measure any DE/MG perturbation evolution parameters. If, however, upcoming observations from surveys like DES, Euclid or LSST show indications for a deviation from a cosmological constant, our formalism will be a useful tool towards model selection in the dark sector.

  12. Fermi LAT search for internal bremsstrahlung signatures from dark matter annihilation

    NASA Astrophysics Data System (ADS)

    Bringmann, Torsten; Huang, Xiaoyuan; Ibarra, Alejandro; Vogl, Stefan; Weniger, Christoph

    2012-07-01

    A commonly encountered obstacle in indirect searches for galactic dark matter is how to disentangle possible signals from astrophysical backgrounds. Given that such signals are most likely subdominant, the search for pronounced spectral features plays a key role for indirect detection experiments; monochromatic gamma-ray lines or similar features related to internal bremsstrahlung, in particular, provide smoking gun signatures. We perform a dedicated search for the latter in the data taken by the Fermi gamma-ray space telescope during its first 43 months. To this end, we use a new adaptive procedure to select optimal target regions that takes into account both standard and contracted dark matter profiles. The behaviour of our statistical method is tested by a subsampling analysis of the full sky data and found to reproduce the theoretical expectations very well. The limits on the dark matter annihilation cross-section that we derive are stronger than what can be obtained from the observation of dwarf galaxies and, at least for the model considered here, collider searches. While these limits are still not quite strong enough to probe annihilation rates expected for thermally produced dark matter, future prospects to do so are very good. In fact, we already find a weak indication, with a significance of 3.1σ (4.3σ) when (not) taking into account the look-elsewhere effect, for an internal bremsstrahlung-like signal that would correspond to a dark matter mass of ~150 GeV; the same signal is also well fitted by a gamma-ray line at around 130 GeV. Although this would be a fascinating possibility, we caution that a much more dedicated analysis and additional data will be necessary to rule out or confirm this option.

  13. Fermi LAT search for internal bremsstrahlung signatures from dark matter annihilation

    SciTech Connect

    Bringmann, Torsten; Huang, Xiaoyuan; Ibarra, Alejandro; Vogl, Stefan; Weniger, Christoph E-mail: x_huang@bao.ac.cn E-mail: stefan.vogl@tum.de

    2012-07-01

    A commonly encountered obstacle in indirect searches for galactic dark matter is how to disentangle possible signals from astrophysical backgrounds. Given that such signals are most likely subdominant, the search for pronounced spectral features plays a key role for indirect detection experiments; monochromatic gamma-ray lines or similar features related to internal bremsstrahlung, in particular, provide smoking gun signatures. We perform a dedicated search for the latter in the data taken by the Fermi gamma-ray space telescope during its first 43 months. To this end, we use a new adaptive procedure to select optimal target regions that takes into account both standard and contracted dark matter profiles. The behaviour of our statistical method is tested by a subsampling analysis of the full sky data and found to reproduce the theoretical expectations very well. The limits on the dark matter annihilation cross-section that we derive are stronger than what can be obtained from the observation of dwarf galaxies and, at least for the model considered here, collider searches. While these limits are still not quite strong enough to probe annihilation rates expected for thermally produced dark matter, future prospects to do so are very good. In fact, we already find a weak indication, with a significance of 3.1σ (4.3σ) when (not) taking into account the look-elsewhere effect, for an internal bremsstrahlung-like signal that would correspond to a dark matter mass of ∼150 GeV; the same signal is also well fitted by a gamma-ray line at around 130 GeV. Although this would be a fascinating possibility, we caution that a much more dedicated analysis and additional data will be necessary to rule out or confirm this option.

  14. A tentative gamma-ray line from Dark Matter annihilation at the Fermi Large Area Telescope

    SciTech Connect

    Weniger, Christoph

    2012-08-01

    The observation of a gamma-ray line in the cosmic-ray fluxes would be a smoking-gun signature for dark matter annihilation or decay in the Universe. We present an improved search for such signatures in the data of the Fermi Large Area Telescope (LAT), concentrating on energies between 20 and 300 GeV. Besides updating to 43 months of data, we use a new data-driven technique to select optimized target regions depending on the profile of the Galactic dark matter halo. In regions close to the Galactic center, we find a 4.6σ indication for a gamma-ray line at E{sub γ} ≈ 130 GeV. When taking into account the look-elsewhere effect the significance of the observed excess is 3.2σ. If interpreted in terms of dark matter particles annihilating into a photon pair, the observations imply a dark matter mass of m{sub χ} = 129.8±2.4 {sup +7}{sub −13} GeV and a partial annihilation cross-section of (σv){sub χχ} {sub →} {sub γγ} = (1.27±0.32 {sup +0.18}{sub −0.28}) × 10{sup −27}cm{sup 3}s{sup −1} when using the Einasto dark matter profile. The evidence for the signal is based on about 50 photons; it will take a few years of additional data to clarify its existence.

  15. Observing two dark accelerators around the Galactic Centre with Fermi Large Area Telescope

    NASA Astrophysics Data System (ADS)

    Hui, C. Y.; Yeung, P. K. H.; Ng, C. W.; Lin, L. C. C.; Tam, P. H. T.; Cheng, K. S.; Kong, A. K. H.; Chernyshov, D. O.; Dogiel, V. A.

    2016-04-01

    We report the results from a detailed γ-ray investigation in the field of two `dark accelerators', HESS J1745-303 and HESS J1741-302, with 6.9 yr of data obtained by the Fermi Large Area Telescope. For HESS J1745-303, we found that its MeV-GeV emission is mainly originated from the `Region A' of the TeV feature. Its γ-ray spectrum can be modelled with a single power law with a photon index of Γ ˜ 2.5 from few hundreds MeV-TeV. Moreover, an elongated feature, which extends from `Region A' towards north-west for ˜1.3°, is discovered for the first time. The orientation of this feature is similar to that of a large-scale atomic/molecular gas distribution. For HESS J1741-302, our analysis does not yield any MeV-GeV counterpart for this unidentified TeV source. On the other hand, we have detected a new point source, Fermi J1740.1-3013, serendipitously. Its spectrum is apparently curved which resembles that of a γ-ray pulsar. This makes it possibly associated with PSR B1737-20 or PSR J1739-3023.

  16. THE FERMI GAMMA-RAY HAZE FROM DARK MATTER ANNIHILATIONS AND ANISOTROPIC DIFFUSION

    SciTech Connect

    Dobler, Gregory; Cholis, Ilias; Weiner, Neal E-mail: ilias.cholis@sissa.it

    2011-11-01

    Recent full-sky maps of the Galaxy from the Fermi Gamma-Ray Space Telescope have revealed a diffuse component of emission toward the Galactic center and extending up to roughly {+-}50{sup 0} in latitude. This Fermi 'haze' is the inverse Compton emission generated by the same electrons that generate the microwave synchrotron haze at Wilkinson Microwave Anisotropy Probe wavelengths. The gamma-ray haze has two distinct characteristics: the spectrum is significantly harder than emission elsewhere in the Galaxy and the morphology is elongated in latitude with respect to longitude with an axis ratio of {approx}2. If these electrons are generated through annihilations of dark matter (DM) particles in the Galactic halo, this morphology is difficult to realize with a standard spherical halo and isotropic cosmic-ray (CR) diffusion. However, we show that anisotropic diffusion along ordered magnetic field lines toward the center of the Galaxy coupled with a prolate DM halo can easily yield the required morphology without making unrealistic assumptions about diffusion parameters. Furthermore, a Sommerfeld enhancement to the self-annihilation cross-section of {approx}30 yields a good fit to the morphology, amplitude, and spectrum of both the gamma-ray and microwave haze. The model is also consistent with local CR measurements as well as cosmic microwave background constraints.

  17. Dark matter and pulsar model constraints from Galactic center Fermi/LAT γ-ray observations

    NASA Astrophysics Data System (ADS)

    Gordon, Chris; Macias, Oscar

    2014-05-01

    Employing Fermi/LAT γ-ray observations, several independent groups have found excess extended γ-ray emission at the Galactic center (GC). Both, annihilating dark matter (DM) or a population of ~ 103 unresolved millisecond pulsars (MSPs) are regarded as well motivated possible explanations. However, there is significant uncertainties in the diffuse Galactic background at the GC. We have performed a revaluation of these two models for the extended γ-ray source at the GC by accounting for the systematic uncertainties of the Galactic diffuse emission model. We also marginalize over point source and diffuse background parameters in the region of interest. We show that the excess emission is significantly more extended than a point source. We find that the DM (or pulsar population) signal is larger than the systematic errors and therefore proceed to determine the sectors of parameter space that provide an acceptable fit to the data. We found that a population of several thousand MSPs with parameters consistent with the average spectral shape of Fermi/LAT measured MSPs was able to fit the GC excess emission. For DM, we found that a pure τ+τ- annihilation channel is not a good fit to the data. But a mixture of τ+τ- and bb with a <σ v> of order the thermal relic value and a DM mass of around 20 to 60 GeV provides an adequate fit.

  18. Sensitivity projections for dark matter dearches with the Fermi large area telescope

    DOE PAGESBeta

    Charles, E.; M. Sanchez-Conde; Anderson, B.; Caputo, R.; Cuoco, A.; Di Mauro, M.; Drlica-Wagner, A.; Gomez-Vargas, G. A.; Meyer, M.; Tibaldo, L.; et al

    2016-05-20

    In this study, the nature of dark matter is a longstanding enigma of physics; it may consist of particles beyond the Standard Model that are still elusive to experiments. Among indirect search techniques, which look for stable products from the annihilation or decay of dark matter particles, or from axions coupling to high-energy photons, observations of themore » $$\\gamma$$-ray sky have come to prominence over the last few years, because of the excellent sensitivity of the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope mission. The LAT energy range from 20 MeV to above 300 GeV is particularly well suited for searching for products of the interactions of dark matter particles. In this report we describe methods used to search for evidence of dark matter with the LAT, and review the status of searches performed with up to six years of LAT data. We also discuss the factors that determine the sensitivities of these searches, including the magnitudes of the signals and the relevant backgrounds, considering both statistical and systematic uncertainties. We project the expected sensitivities of each search method for 10 and 15 years of LAT data taking. In particular, we find that the sensitivity of searches targeting dwarf galaxies, which provide the best limits currently, will improve faster than the square root of observing time. Current LAT limits for dwarf galaxies using six years of data reach the thermal relic level for masses up to 120 GeV for the $$b\\bar{b}$$ annihilation channel for reasonable dark matter density profiles. With projected discoveries of additional dwarfs, these limits could extend to about 250 GeV. With as much as 15 years of LAT data these searches would be sensitive to dark matter annihilations at the thermal relic cross section for masses to greater than 400 GeV (200 GeV) in the $$b\\bar{b}$$ ($$\\tau^+ \\tau^-$$) annihilation channels.« less

  19. Gamma rays from dark matter annihilations strongly constrain the substructure in halos.

    PubMed

    Pinzke, Anders; Pfrommer, Christoph; Bergström, Lars

    2009-10-30

    To fit recent data, e(+/-) from dark matter (DM) needs a boosted annihilation rate. This may imply an observable level of gamma rays from nearby galaxy clusters for the Fermi satellite. Using EGRET data, we limit the minimum mass of DM substructures to be about 5x10(3) times larger than for cold DM, meaning a cutoff similar to, e.g., warm DM. We numerically simulate clusters to reliably model the background. If we assume no anomalous boost factor, we find comparable levels of gamma-ray emission from DM and cosmic ray interactions, giving a chance with future data to characterize the DM. PMID:19905798

  20. Constraining sterile neutrino warm dark matter with Chandra observations of the Andromeda galaxy

    SciTech Connect

    Watson, Casey R.; Polley, Nicholas K.; Li, Zhiyuan E-mail: zyli@astro.ucla.edu

    2012-03-01

    We use the Chandra unresolved X-ray emission spectrum from a 12'–28' (2.8–6.4 kpc) annular region of the Andromeda galaxy to constrain the radiative decay of sterile neutrino warm dark matter. By excising the most baryon-dominated, central 2.8 kpc of the galaxy, we reduce the uncertainties in our estimate of the dark matter mass within the field of view and improve the signal-to-noise ratio of prospective sterile neutrino decay signatures relative to hot gas and unresolved stellar emission. Our findings impose the most stringent limit on the sterile neutrino mass to date in the context of the Dodelson-Widrow model, m{sub s} < 2.2 keV (95% C.L.). Our results also constrain alternative sterile neutrino production scenarios at very small active-sterile neutrino mixing angles.

  1. Searching for dwarf spheroidal galaxies and other galactic dark matter substructures with the Fermi large area telescope

    SciTech Connect

    Drlica-Wagner, Alex

    2013-08-01

    Over the past century, it has become clear that about a quarter of the known universe is composed of an invisible, massive component termed ''dark matter''. Some of the most popular theories of physics beyond the Standard Model suggest that dark matter may be a new fundamental particle that could self-annihilate to produce γ rays. Nearby over-densities in the dark matter halo of our Milky Way present some of the most promising targets for detecting the annihilation of dark matter. We used the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope to search for γ rays produced by dark matter annihilation in Galactic dark matter substructures. We searched for γ-ray emission coincident with Milky Way dwarf spheroidal satellite galaxies, which trace the most massive Galactic dark matter substructures. We also sought to identify nearby dark matter substructures that lack all astrophysical tracers and would be detectable only through γ-ray emission from dark matter annihilation. We found no conclusive evidence for γ-ray emission from dark matter annihilation, and we set stringent and robust constraints on the dark matter annihilation cross section. While γ-ray searches for dark matter substructure are currently the most sensitive and robust probes of dark matter annihilation, they are just beginning to intersect the theoretically preferred region of dark matter parameter space. Thus, we consider future prospects for increasing the sensitivity of γ-ray searches through improvements to the LAT instrument performance and through upcoming wide- field optical surveys.

  2. Constraining Self-Interacting Dark Matter: Insights from Equal Mass Mergers of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Yeonchi Kim, Stacy; Peter, Annika

    2016-01-01

    While the ΛCDM model has been wildly successful at explaining structure on large scales, it fails to do so on small scales---dark matter halos of scales comparable to that of galaxy clusters and smaller are more cored and less numerous than ΛCDM predicts. One potential solution challenges the canonical assumption that dark matter is collisionless and instead assumes that it is collisional, or self-interacting. The most stringent upper limits on the dark matter self-interaction cross section have come from observations of merging galaxy clusters. Self-interactions cause the merging dark matter halos to evolve differently from the galaxies, which are effectively collisionless. It has been hypothesized that this leads to an spatial offset between the peaks in the dark matter and galaxy distributions. We show that in equal mass mergers offsets do not develop except under a narrow range of merger conditions. Mergers with observable offsets have an infall velocity comparable to the escape velocity from a halo---promoting the explusion of significant mass and the formation of tails---and is head-on. We discuss other observable signatures of self-interactions that may better constrain the dark matter self-interaction cross-section in equal mass cluster mergers.

  3. Constrained Simulations of the Local Universe in Different Dark Matter Scenarios

    SciTech Connect

    Yepes, G.; Martinez-Vaquero, L. A.; Gottloeber, S.; Hoffman, Y.

    2009-04-17

    Constrained simulations of the Local Universe are an invaluable tool to investigate in detail the nature of dark matter particles. Thanks to them, we can simulate the formation of dark halos in environments pretty much like the one our Milky Way happened to live. A direct comparison with observations of our Local Universe can be made in this way, minimizing the effects of cosmic variance in the simulations. In this paper we present the results of a comparison of high-resolution simulated Local Group (LG) objects done in 3 different dark matter scenarios: The standard Cold Dark Matter and two Warm Dark Matter models with particles masses ranging from 3 to 1 keV, that are still compatible with high-redshift observations. We focus here on the study of substructures and mass profiles for the CDM and WDM LG objects and draw some conclusions about the limits on the mass of warm dark matter particles to be compatible with the most recently discovered Milky Way ultra-faint satellites.

  4. Encircling the dark: constraining dark energy via cosmic density in spheres

    NASA Astrophysics Data System (ADS)

    Codis, S.; Pichon, C.; Bernardeau, F.; Uhlemann, C.; Prunet, S.

    2016-08-01

    The recently published analytic probability density function for the mildly non-linear cosmic density field within spherical cells is used to build a simple but accurate maximum likelihood estimate for the redshift evolution of the variance of the density, which, as expected, is shown to have smaller relative error than the sample variance. This estimator provides a competitive probe for the equation of state of dark energy, reaching a few per cent accuracy on wp and wa for a Euclid-like survey. The corresponding likelihood function can take into account the configuration of the cells via their relative separations. A code to compute one-cell-density probability density functions for arbitrary initial power spectrum, top-hat smoothing and various spherical-collapse dynamics is made available online, so as to provide straightforward means of testing the effect of alternative dark energy models and initial power spectra on the low-redshift matter distribution.

  5. Encircling the dark: constraining dark energy via cosmic density in spheres

    NASA Astrophysics Data System (ADS)

    Codis, S.; Pichon, C.; Bernardeau, F.; Uhlemann, C.; Prunet, S.

    2016-05-01

    The recently published analytic probability density function for the mildly non-linear cosmic density field within spherical cells is used to build a simple but accurate maximum likelihood estimate for the redshift evolution of the variance of the density, which, as expected, is shown to have smaller relative error than the sample variance. This estimator provides a competitive probe for the equation of state of dark energy, reaching a few percent accuracy on wp and wa for a Euclid-like survey. The corresponding likelihood function can take into account the configuration of the cells via their relative separations. A code to compute one-cell density probability density functions for arbitrary initial power spectrum, top-hat smoothing and various spherical collapse dynamics is made available online so as to provide straightforward means of testing the effect of alternative dark energy models and initial power-spectra on the low-redshift matter distribution.

  6. Constraining minimal U(1)B-L model from dark matter observations

    NASA Astrophysics Data System (ADS)

    Basak, Tanushree; Mondal, Tanmoy

    2014-03-01

    We study the B-L gauge extension of the Standard Model which contains a singlet scalar and three right-handed neutrinos. The vacuum expectation value of the singlet scalar breaks the U(1)B-L symmetry. Here the third-generation right-handed neutrino is qualified as the dark matter candidate, as an artifact of Z2-charge assignment. Relic abundance of the dark matter is consistent with WMAP9 and PLANCK data, only near scalar resonances where dark matter mass is almost half of the scalar boson masses. Requiring correct relic abundance, we restrict the parameter space of the scalar mixing angle and mass of the heavy scalar boson of this model. Besides this, the maximum value of the spin-independent scattering cross section off nucleon is well below the Xenon100 and recent LUX exclusion limits and can be probed by future Xenon1T experiments. In addition, we compute the annihilation of the dark matter into a two-photon final state in detail and compare with the Fermi-LAT upper bound on ⟨σv⟩γγ for the NFW and Einasto profile.

  7. Search for gamma-ray emission from eight dwarf spheroidal galaxy candidates discovered in year two of Dark Energy Survey with Fermi-LAT data

    NASA Astrophysics Data System (ADS)

    Li, Shang; Liang, Yun-Feng; Duan, Kai-Kai; Shen, Zhao-Qiang; Huang, Xiaoyuan; Li, Xiang; Fan, Yi-Zhong; Liao, Neng-Hui; Feng, Lei; Chang, Jin

    2016-02-01

    Very recently the Dark Energy Survey (DES) Collaboration has released their second group of dwarf spheroidal (dSph) galaxy candidates. With the publicly available Pass 8 data of Fermi-LAT we search for γ -ray emissions from the directions of these eight newly discovered dSph galaxy candidates. No statistically significant γ -ray signal has been found in the combined analysis of these sources. With the empirically estimated J-factors of these sources, the constraint on the annihilation channel of χ χ →τ+τ- is comparable to the bound set by the joint analysis of fifteen previously known dSphs with kinematically constrained J-factors for the dark matter mass mχ>250 GeV . In the direction of Tucana III (DES J2356-5935), one of the nearest dSph galaxy candidates that is ˜25 kpc away, there is a weak γ -ray signal and its peak test statistic (TS) value for the dark matter annihilation channel χ χ →τ+τ-1 is ≈6.7 at mχ˜15 GeV . The significance of the possible signal likely increases with time. More data is highly needed to pin down the physical origin of such a GeV excess.

  8. Constraining dark matter sub-structure with the dynamics of astrophysical systems

    SciTech Connect

    González-Morales, Alma X.; Valenzuela, Octavio; Aguilar, Luis A. E-mail: octavio@astro.unam.mx

    2013-03-01

    The accuracy of the measurements of some astrophysical dynamical systems allows to constrain the existence of incredibly small gravitational perturbations. In particular, the internal Solar System dynamics (planets, Earth-Moon) opens up the possibility, for the first time, to prove the abundance, mass and size, of dark sub-structures at the Earth vicinity. We find that adopting the standard dark matter density, its local distribution can be composed by sub-solar mass halos with no currently measurable dynamical consequences, regardless of the mini-halo fraction. On the other hand, it is possible to exclude the presence of dark streams with linear mass densities higher than λ{sub st} > 10{sup −10}M{sub ☉}/AU (about the Earth mass spread along the diameter of the SS up to the Kuiper belt). In addition, we review the dynamics of wide binaries inside the dwarf spheroidal galaxies in the Milky Way. The dynamics of such kind of binaries seem to be compatible with the presence of a huge fraction of dark sub-structure, thus their existence is not a sharp discriminant of the dark matter hypothesis as been claimed before. However, there are regimes where the constraints from different astrophysical systems may reveal the sub-structure mass function cut-off scale.

  9. Fermi Large Area Telescope observation of high-energy solar flares: constraining emission scenarios

    NASA Astrophysics Data System (ADS)

    Omodei, Nicola; Pesce-Rollins, Melissa; Petrosian, Vahe; Liu, Wei; Rubio da Costa, Fatima

    2015-08-01

    The Fermi Large Area Telescope (LAT) is the most sensitive instrument ever deployed in space for observing gamma-ray emission >100 MeV. This has also been demonstrated by its detection of quiescent gamma-ray emission from pions produced by cosmic-ray protons interacting in the solar atmosphere, and from cosmic-ray electron interactions with solar optical photons. The Fermi LAT has also detected high-energy gamma-ray emission associated with GOES M-class and X-class X-ray flares, each accompanied by a coronal mass ejection and a solar energetic particle event increasing the number of detected solar flares by almost a factor of 10 with respect to previous space observations. During the impulsive phase, gamma rays with energies up to several hundreds of MeV have been recorded by the LAT. Emission up to GeV energies lasting several hours after the flare has also been recorded by the LAT. Of particular interest are the recent detections of two solar flares whose position behind the limb was confirmed by the STEREO-B satellite. While gamma-ray emission up to tens of MeV resulting from proton interactions has been detected before from occulted solar flares, the significance of these particular events lies in the fact that these are the first detections of >100 MeV gamma-ray emission from footpoint-occulted flares. We will present the Fermi-LAT, RHESSI and STEREO observations of these flares and discuss the various emission scenarios for these sources.

  10. 130 GeV dark matter and the Fermi gamma-ray line

    NASA Astrophysics Data System (ADS)

    Cline, James M.

    2012-07-01

    Based on tentative evidence for a peak in the Fermi gamma-ray spectrum originating from near the center of the galaxy, it has been suggested that dark matter of mass ˜130GeV is annihilating directly into photons with a cross section ˜24 times smaller than that needed for the thermal relic density. We propose a simple particle physics model in which the dark matter is a scalar X, with a coupling λXX2|S|2 to a scalar multiplet S carrying electric charge, which allows for XX→γγ at one loop due to the virtual S. We predict a second monochromatic photon peak at 114 GeV due to XX→γZ. The S is colored under a hidden sector SU(N) or QCD to help boost the XX→γγ cross section. The analogous coupling λhh2|S|2 to the Higgs boson can naturally increase the partial width for h→γγ by an amount comparable to its standard model value, as suggested by recent measurements from CMS. Due to the hidden sector SU(N) (or QCD), S binds to its antiparticle to form S mesons, which will be pair-produced in colliders and then decay predominantly to XX, hh, or to glueballs of the SU(N) which subsequently decay to photons. The cross section for X on nucleons is close to the Xenon100 upper limit, suggesting that it should be discovered soon by direct detection.

  11. Two Emission Mechanisms in the Fermi Bubbles: A Possible Signal of Annihilating Dark Matter

    SciTech Connect

    Hooper, Dan; Slatyer, Tracy R.

    2013-09-01

    We study the variation of the spectrum of the Fermi Bubbles with Galactic latitude. Far from the Galactic plane (|b| > 30 degrees), the observed gamma-ray emission is nearly invariant with latitude, and is consistent with arising from inverse Compton scattering of the interstellar radiation field by cosmic-ray electrons with an approximately power-law spectrum. The same electrons in the presence of microgauss-scale magnetic fields can also generate the the observed microwave "haze". At lower latitudes (b < 20 degrees), in contrast, the spectrum of the emission correlated with the Bubbles possesses a pronounced spectral feature peaking at 1-4 GeV (in E^2 dN/dE) which cannot be generated by any realistic spectrum of electrons. Instead, we conclude that a second (non-inverse-Compton) emission mechanism must be responsible for the bulk of the low-energy, low-latitude emission. This second component is spectrally similar to the excess GeV emission previously reported from the Galactic Center (GC), and also appears spatially consistent with a luminosity per volume falling approximately as r^-2.4, where r is the distance from the GC. We argue that the spectral feature visible in the low-latitude Bubbles is the extended counterpart of the GC excess, now detected out to at least 2-3 kpc from the GC. The spectrum and angular distribution of the signal is consistent with that predicted from ~10 GeV dark matter particles annihilating to leptons, or from ~50 GeV dark matter particles annihilating to quarks, following a distribution similar to the canonical Navarro-Frenk-White (NFW) profile. We also consider millisecond pulsars as a possible astrophysical explanation for the signal, as observed millisecond pulsars possess a spectral cutoff at approximately the required energy. Any such scenario would require a large population of unresolved millisecond pulsars extending at least 2-3 kpc from the GC.

  12. ATIC, PAMELA, HESS, and Fermi data and nearby dark matter subhalos

    SciTech Connect

    Kuhlen, Michael; Malyshev, Dmitry

    2009-06-15

    We study the local flux of electrons and positrons from annihilating dark matter (DM), and investigate how its spectrum depends on the choice of DM model and inhomogeneities in the DM distribution. Below a cutoff energy, the flux is expected to have a universal power-law form with an index n{approx_equal}-2. The cutoff energy and the behavior of the flux near the cutoff is model dependent. The dependence on the DM host halo profile may be significant at energies E<100 GeV and leads to softening of the flux n<-2. There may be additional features at high energies due to the presence of local clumps of DM, especially for models in which the Sommerfeld effect boosts subhalo luminosities. In general, the flux from a nearby clump gives rise to a harder spectrum of electrons and positrons, with an index n>-2. Using the Via Lactea II simulation, we estimate the probability of such subhalo effects in a generic Sommerfeld-enhanced model to be at least 4%, and possibly as high as 15% if subhalos below the simulation's resolution limit are accounted for. We discuss the consequences of these results for the interpretation of the ATIC, PAMELA, HESS, and Fermi data, as well as for future experiments.

  13. EXPLORING THE DARK ACCELERATOR HESS J1745-303 WITH THE FERMI LARGE AREA TELESCOPE

    SciTech Connect

    Hui, C. Y.; Wu, E. M. H.; Wu, J. H. K.; Cheng, K. S.; Huang, R. H. H.; Tam, P. H. T.; Kong, A. K. H.

    2011-07-10

    We present a detailed analysis of the {gamma}-ray emission from HESS J1745-303 with the data obtained by the Fermi Gamma-ray Space Telescope in its first {approx}29 month observation. The source can clearly be detected at the levels of {approx}18{sigma} and {approx}6{sigma} in 1-20 GeV and 10-20 GeV, respectively. We do not find any evidence of the variability seen in the results obtained by the Compton Gamma-ray Observatory. Most of the emission in 10-20 GeV is found to coincide with region C of HESS J1745-303. A simple power law is sufficient to describe the GeV spectrum with a photon index of {Gamma} {approx} 2.6. The power-law spectrum inferred in the GeV regime can be connected to that of a particular spatial component of HESS J1745-303 in 1-10 TeV without any spectral break. These properties impose independent constraints for understanding the nature of this 'dark particle accelerator'.

  14. Exploring the Dark Accelerator HESS J1745-303 with the Fermi Large Area Telescope

    NASA Astrophysics Data System (ADS)

    Hui, C. Y.; Wu, E. M. H.; Wu, J. H. K.; Huang, R. H. H.; Cheng, K. S.; Tam, P. H. T.; Kong, A. K. H.

    2011-07-01

    We present a detailed analysis of the γ-ray emission from HESS J1745-303 with the data obtained by the Fermi Gamma-ray Space Telescope in its first ~29 month observation. The source can clearly be detected at the levels of ~18σ and ~6σ in 1-20 GeV and 10-20 GeV, respectively. We do not find any evidence of the variability seen in the results obtained by the Compton Gamma-ray Observatory. Most of the emission in 10-20 GeV is found to coincide with region C of HESS J1745-303. A simple power law is sufficient to describe the GeV spectrum with a photon index of Γ ~ 2.6. The power-law spectrum inferred in the GeV regime can be connected to that of a particular spatial component of HESS J1745-303 in 1-10 TeV without any spectral break. These properties impose independent constraints for understanding the nature of this "dark particle accelerator."

  15. CONSTRAINING THE DARK ENERGY EQUATION OF STATE USING LISA OBSERVATIONS OF SPINNING MASSIVE BLACK HOLE BINARIES

    SciTech Connect

    Petiteau, Antoine; Babak, Stanislav; Sesana, Alberto

    2011-05-10

    Gravitational wave (GW) signals from coalescing massive black hole (MBH) binaries could be used as standard sirens to measure cosmological parameters. The future space-based GW observatory Laser Interferometer Space Antenna (LISA) will detect up to a hundred of those events, providing very accurate measurements of their luminosity distances. To constrain the cosmological parameters, we also need to measure the redshift of the galaxy (or cluster of galaxies) hosting the merger. This requires the identification of a distinctive electromagnetic event associated with the binary coalescence. However, putative electromagnetic signatures may be too weak to be observed. Instead, we study here the possibility of constraining the cosmological parameters by enforcing statistical consistency between all the possible hosts detected within the measurement error box of a few dozen of low-redshift (z < 3) events. We construct MBH populations using merger tree realizations of the dark matter hierarchy in a {Lambda}CDM universe, and we use data from the Millennium simulation to model the galaxy distribution in the LISA error box. We show that, assuming that all the other cosmological parameters are known, the parameter w describing the dark energy equation of state can be constrained to a 4%-8% level (2{sigma} error), competitive with current uncertainties obtained by type Ia supernovae measurements, providing an independent test of our cosmological model.

  16. Anisotropies in the diffuse gamma-ray background from dark matter with Fermi LAT: a closer look

    NASA Astrophysics Data System (ADS)

    Cuoco, A.; Sellerholm, A.; Conrad, J.; Hannestad, S.

    2011-07-01

    We perform a detailed study of the sensitivity to the anisotropies related to dark matter (DM) annihilation in the isotropic gamma-ray background (IGRB) as measured by the Fermi Large Area Telescope (Fermi LAT). For the first time, we take into account the effects of the Galactic foregrounds and use a realistic representation of the Fermi LAT. We implement an analysis pipeline which simulates Fermi LAT data sets starting from model maps of the Galactic foregrounds, the Fermi-resolved point sources, the extragalactic diffuse emission and the signal from DM annihilation. The effects of the detector are taken into account by convolving the model maps with the Fermi LAT instrumental response. We then use the angular power spectrum to characterize the anisotropy properties of the simulated data and to study the sensitivity to DM. We consider DM anisotropies of extragalactic origin and of Galactic origin (which can be generated through annihilation in the Milky Way substructures) as opposed to a background of anisotropies generated by sources of astrophysical origin, blazars for example. We find that with statistics from 5 yr of observation, Fermi is sensitive to a DM contribution at the level of 1-10 per cent of the measured IGRB depending on the DM mass mχ and annihilation mode. In terms of the thermally averaged cross-section <σAv>, this corresponds to ˜10-25 cm3 s-1, i.e. slightly above the typical expectations for a thermal relic, for low values of the DM mass mχ≲ 100 GeV. The anisotropy method for DM searches has a sensitivity comparable to the usual methods based only on the energy spectrum and thus constitutes an independent and complementary piece of information in the DM puzzle.

  17. Constraining the High-energy Emission from Gamma-Ray Bursts with Fermi

    NASA Astrophysics Data System (ADS)

    Fermi Large Area Telescope Team; Ackermann, M.; Ajello, M.; Baldini, L.; Barbiellini, G.; Baring, M. G.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bouvier, A.; Brigida, M.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cutini, S.; D'Ammando, F.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Granot, J.; Grenier, I. A.; Grove, J. E.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hays, E.; Horan, D.; Jóhannesson, G.; Kataoka, J.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; McEnery, J.; McGlynn, S.; Michelson, P. F.; Mitthumsiri, W.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Norris, J. P.; Nuss, E.; Nymark, T.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Racusin, J. L.; Rainò, S.; Rando, R.; Razzaque, S.; Reimer, A.; Reimer, O.; Ritz, S.; Ryde, F.; Sgrò, C.; Siskind, E. J.; Sonbas, E.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Stawarz, Łukasz; Suson, D. J.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Tosti, G.; Uehara, T.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Fermi Gamma-ray Burst Monitor Team; Connaughton, V.; Briggs, M. S.; Guirec, S.; Goldstein, A.; Burgess, J. M.; Bhat, P. N.; Bissaldi, E.; Camero-Arranz, A.; Fishman, J.; Fitzpatrick, G.; Foley, S.; Gruber, D.; Jenke, P.; Kippen, R. M.; Kouveliotou, C.; McBreen, S.; Meegan, C.; Paciesas, W. S.; Preece, R.; Rau, A.; Tierney, D.; van der Horst, A. J.; von Kienlin, A.; Wilson-Hodge, C.; Xiong, S.

    2012-08-01

    We examine 288 gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field of view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the νF ν spectra (E pk). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E pk than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cutoff in their high-energy spectra, which if assumed to be due to γγ attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

  18. CONSTRAINING THE HIGH-ENERGY EMISSION FROM GAMMA-RAY BURSTS WITH FERMI

    SciTech Connect

    Ackermann, M.; Ajello, M.; Bechtol, K.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bottacini, E.; Buehler, R.; Cameron, R. A.; Charles, E.; Baldini, L.; Bellazzini, R.; Barbiellini, G.; Baring, M. G.; Bonamente, E.; Cecchi, C.; Bouvier, A.; Brigida, M.; Buson, S.; Caliandro, G. A. E-mail: kocevski@slac.stanford.edu E-mail: connauv@uah.edu E-mail: michael.briggs@nasa.gov; Collaboration: Fermi Large Area Telescope Team; Fermi Gamma-ray Burst Monitor Team; and others

    2012-08-01

    We examine 288 gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field of view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the {nu}F{sub {nu}} spectra (E{sub pk}). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E{sub pk} than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cutoff in their high-energy spectra, which if assumed to be due to {gamma}{gamma} attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

  19. Constraining the High-Energy Emission from Gamma-Ray Bursts with Fermi

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil; Harding, A. K.; Hays, E.; Racusin, J. L.; Sonbas, E.; Stamatikos, M.; Guirec, S.

    2012-01-01

    We examine 288 GRBs detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field-of-view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the nuF(sub v) spectra (E(sub pk)). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E(sub pk) than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cut-off in their high-energy spectra, which if assumed to be due to gamma gamma attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

  20. Consequences of a dark disk for the Fermi and PAMELA signals in theories with a Sommerfeld enhancement

    SciTech Connect

    Cholis, Ilias; Goodenough, Lisa E-mail: lcg261@nyu.edu

    2010-09-01

    Much attention has been given to dark matter explanations of the PAMELA positron fraction and Fermi electronic excesses. For those theories with a TeV-scale WIMP annihilating through a light force-carrier, the associated Sommerfeld enhancement provides a natural explanation of the large boost factor needed to explain the signals, and the light force-carrier naturally gives rise to hard cosmic ray spectra without excess π{sup 0}-gamma rays or anti-protons. The Sommerfeld enhancement of the annihilation rate, which at low relative velocities v{sub rel} scales as 1/v{sub rel}, relies on the comparatively low velocity dispersion of the dark matter particles in the smooth halo. Dark matter substructures in which the velocity dispersion is smaller than in the smooth halo have even larger annihilation rates. N-body simulations containing only dark matter predict the existence of such structures, for example subhalos and caustics, and the effects of these substructures on dark matter indirect detection signals have been studied extensively. The addition of baryons into cosmological simulations of disk-dominated galaxies gives rise to an additional substructure component, a dark disk. The disk has a lower velocity dispersion than the spherical halo component by a factor ∼ 6, so the contributions to dark matter signals from the disk can be more significant in Sommerfeld models than for WIMPs without such low-velocity ehancements. We consider the consequences of a dark disk on the observed signals of e{sup +}e{sup −}, p p-bar and γ-rays as measured by Fermi and PAMELA in models where the WIMP annihilations are into a light boson. We find that both the PAMELA and Fermi results are easily accomodated by scenarios in which a disk signal is included with the standard spherical halo signal. If contributions from the dark disk are important, limits from extrapolations to the center of the galaxy contain significant uncertainties beyond those from the spherical halo profile

  1. Constraining the Dark Cusp in the Galactic Center by Long-period Binaries

    NASA Astrophysics Data System (ADS)

    Alexander, Tal; Pfuhl, Oliver

    2014-01-01

    Massive black holes (MBHs) in galactic nuclei are believed to be surrounded by a high-density stellar cluster, whose mass is mostly in hard-to-detect faint stars and compact remnants. Such dark cusps dominate the dynamics near the MBH: a dark cusp in the Galactic center (GC) of the Milky Way would strongly affect orbital tests of general relativity there; on cosmic scales, dark cusps set the rates of gravitational wave emission events from compact remnants that spiral into MBHs, and they modify the rates of tidal disruption events, to list only some implications. A recently discovered long-period massive young binary (with period P 12 <~ 1 yr, total mass M_{12}\\sim {\\cal O}(100\\, M_{\\odot }), and age T 12 ~ 6 × 106 yr), only ~0.1 pc from the Galactic MBH, sets a lower bound on the stellar two-body relaxation timescale there, min t rlxvprop(P 12/M 12)2/3 T 12 ~ 107 yr, and, correspondingly, an upper bound on the stellar number density, \\max n_{\\star }\\sim {few\\times }10^{8}/\\langle M_{\\star }^{2}\\rangle \\,{pc^{-3}} (\\langle M_{\\star }^{2}\\rangle ^{1/2} is the rms stellar mass), based on the binary's survival against evaporation by the dark cusp. However, a conservative dynamical estimate, the drain limit, implies t_{{rlx}} \\gt {\\cal O}({10^{8}}\\,{yr}). Such massive binaries are thus too short-lived and tightly bound to constrain a dense relaxed dark cusp. We explore here in detail the use of longer-period, less massive, and longer-lived binaries (P 12 ~ few yr, M 12 ~ 2-4 M ⊙, T 12 ~ 108-1010 yr), presently just below the detection threshold, for probing the dark cusp and develop the framework for translating their future detections among the giants in the GC into dynamical constraints.

  2. Constraints on Cosmic Rays, Magnetic Fields, and Dark Matter from Gamma-ray Observations of the Coma Cluster of Galaxies with VERITAS and FERMI

    NASA Technical Reports Server (NTRS)

    Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Cesarini, A.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickherber, R.; Dumm, J.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.; Galante, N.; Perkins, J. S.

    2012-01-01

    Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account of weak energy losses, can accumulate, suggesting that clusters may also be sources of very high energy (VHE; E greater than100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cerenkov telescopes, with complementing Fermi Large Area Telescope observations at GeV energies. No significant gamma-ray emission from the Coma Cluster was detected. Integral flux upper limits at the 99 confidence level were measured to be on the order of (2-5) x 10(sup -8) photons m(sup -2) s(sup -1) (VERITAS,greater than 220 GeV) and approximately 2 x 10(sup -6) photons m(sup -2) s(sup -1) (Fermi, 1-3 GeV), respectively. We use the gamma-ray upper limits to constrain cosmic rays (CRs) and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be less than 16% from VERITAS data and less than 1.7% from Fermi data (averaged within the virial radius). These upper limits are starting to constrain the CR physics in self-consistent cosmological cluster simulations and cap the maximum CR acceleration efficiency at structure formation shocks to be 50. Alternatively, this may argue for non-negligible CR transport processes such as CR streaming and diffusion into the outer cluster regions. Assuming that the radio-emitting electrons of the Coma halo result from hadronic CR interactions, the observations imply a lower limit on the central magnetic field in Coma of approximately (2-5.5)microG, depending on the radial magnetic field profile and on the gamma-ray spectral index. Since these values are below those inferred by Faraday rotation measurements in Coma (for most of the parameter space), this renders the hadronic model a very plausible explanation of the Coma radio halo. Finally, since galaxy clusters are dark

  3. CONSTRAINTS ON COSMIC RAYS, MAGNETIC FIELDS, AND DARK MATTER FROM GAMMA-RAY OBSERVATIONS OF THE COMA CLUSTER OF GALAXIES WITH VERITAS AND FERMI

    SciTech Connect

    Arlen, T.; Aune, T.; Bouvier, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Benbow, W.; Byrum, K.; Cannon, A.; Collins-Hughes, E.; Cesarini, A.; Connolly, M. P.; Ciupik, L.; Cui, W.; Feng, Q.; Finley, J. P.; Dumm, J.; Falcone, A.; Federici, S. E-mail: christoph.pfrommer@h-its.org; and others

    2012-10-01

    Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated and, on account of weak energy losses, can accumulate, suggesting that clusters may also be sources of very high energy (VHE; E > 100 GeV) gamma-ray emission. We report here on VHE gamma-ray observations of the Coma galaxy cluster with the VERITAS array of imaging Cerenkov telescopes, with complementing Fermi Large Area Telescope observations at GeV energies. No significant gamma-ray emission from the Coma Cluster was detected. Integral flux upper limits at the 99% confidence level were measured to be on the order of (2-5) Multiplication-Sign 10{sup -8} photons m {sup -2} s {sup -1} (VERITAS, >220 GeV) and {approx}2 Multiplication-Sign 10{sup -6} photons m {sup -2} s {sup -1} (Fermi, 1-3 GeV), respectively. We use the gamma-ray upper limits to constrain cosmic rays (CRs) and magnetic fields in Coma. Using an analytical approach, the CR-to-thermal pressure ratio is constrained to be <16% from VERITAS data and <1.7% from Fermi data (averaged within the virial radius). These upper limits are starting to constrain the CR physics in self-consistent cosmological cluster simulations and cap the maximum CR acceleration efficiency at structure formation shocks to be <50%. Alternatively, this may argue for non-negligible CR transport processes such as CR streaming and diffusion into the outer cluster regions. Assuming that the radio-emitting electrons of the Coma halo result from hadronic CR interactions, the observations imply a lower limit on the central magnetic field in Coma of {approx}(2-5.5) {mu}G, depending on the radial magnetic field profile and on the gamma-ray spectral index. Since these values are below those inferred by Faraday rotation measurements in Coma (for most of the parameter space), this renders the hadronic model a very plausible explanation of the Coma radio halo. Finally, since galaxy clusters are dark matter (DM

  4. Constraining sources of ultra high energy cosmic rays using high energy observations with the Fermi satellite

    SciTech Connect

    Pe'er, Asaf; Loeb, Abraham E-mail: aloeb@cfa.harvard.edu

    2012-03-01

    We analyze the conditions that enable acceleration of particles to ultra-high energies, ∼ 10{sup 20} eV (UHECRs). We show that broad band photon data recently provided by WMAP, ISOCAM, Swift and Fermi satellites, yield constraints on the ability of active galactic nuclei (AGN) to produce UHECRs. The high energy (MeV–GeV) photons are produced by Compton scattering of the emitted low energy photons and the cosmic microwave background or extra-galactic background light. The ratio of the luminosities at high and low photon energies can therefore be used as a probe of the physical conditions in the acceleration site. We find that existing data excludes core regions of nearby radio-loud AGN as possible acceleration sites of UHECR protons. However, we show that giant radio lobes are not excluded. We apply our method to Cen A, and show that acceleration of protons to ∼ 10{sup 20} eV can only occur at distances ∼>100 kpc from the core.

  5. Constraining Gamma-Ray Emission from Luminous Infrared Galaxies with Fermi-LAT; Tentative Detection of Arp 220

    NASA Astrophysics Data System (ADS)

    Griffin, Rhiannon D.; Dai, Xinyu; Thompson, Todd A.

    2016-05-01

    Star-forming galaxies produce gamma-rays primarily via pion production, resulting from inelastic collisions between cosmic-ray protons and the interstellar medium (ISM). The dense ISM and high star formation rates of luminous and ultra-luminous infrared galaxies (LIRGs and ULIRGs) imply that they should be strong gamma-ray emitters, but so far only two LIRGs have been detected. Theoretical models for their emission depend on the unknown fraction of cosmic-ray protons that escape these galaxies before interacting. We analyze Fermi-LAT data for 82 of the brightest Infrared Astronomical Satellite LIRGs and ULIRGs. We examine each system individually and carry out a stacking analysis to constrain their gamma-ray fluxes. We report the detection of the nearest ULIRG Arp 220 (˜4.6σ). We observe a gamma-ray flux (0.8–100 GeV) of 2.4 × 10‑10 phot cm‑2 s‑1 with a photon index of 2.23 (8.2 × 1041 erg s‑1 at 77 Mpc). We also derive upper limits (ULs) for the stacked LIRGs and ULIRGs. The gamma-ray luminosity of Arp 220 and the stacked ULs agree with calorimetric predictions for dense star-forming galaxies. With the detection of Arp 220, we extend the gamma-ray–IR luminosity correlation to the high-luminosity regime with {log}{L}0.1-100{GeV}=1.25× {log}{L}8-1000μ {{m}}+26.7 as well as the gamma-ray–radio continuum luminosity correlation with {log}{L}0.1-100{GeV}=1.22× {log}{L}1.4{GHz}+13.3. The current survey of Fermi-LAT is on the verge of detecting more LIRGs/ULIRGs in the local universe, and we expect even more detections with deeper Fermi-LAT observations or the next generation of gamma-ray detectors.

  6. Constraining Gamma-Ray Emission from Luminous Infrared Galaxies with Fermi-LAT; Tentative Detection of Arp 220

    NASA Astrophysics Data System (ADS)

    Griffin, Rhiannon D.; Dai, Xinyu; Thompson, Todd A.

    2016-05-01

    Star-forming galaxies produce gamma-rays primarily via pion production, resulting from inelastic collisions between cosmic-ray protons and the interstellar medium (ISM). The dense ISM and high star formation rates of luminous and ultra-luminous infrared galaxies (LIRGs and ULIRGs) imply that they should be strong gamma-ray emitters, but so far only two LIRGs have been detected. Theoretical models for their emission depend on the unknown fraction of cosmic-ray protons that escape these galaxies before interacting. We analyze Fermi-LAT data for 82 of the brightest Infrared Astronomical Satellite LIRGs and ULIRGs. We examine each system individually and carry out a stacking analysis to constrain their gamma-ray fluxes. We report the detection of the nearest ULIRG Arp 220 (∼4.6σ). We observe a gamma-ray flux (0.8–100 GeV) of 2.4 × 10‑10 phot cm‑2 s‑1 with a photon index of 2.23 (8.2 × 1041 erg s‑1 at 77 Mpc). We also derive upper limits (ULs) for the stacked LIRGs and ULIRGs. The gamma-ray luminosity of Arp 220 and the stacked ULs agree with calorimetric predictions for dense star-forming galaxies. With the detection of Arp 220, we extend the gamma-ray–IR luminosity correlation to the high-luminosity regime with {log}{L}0.1-100{GeV}=1.25× {log}{L}8-1000μ {{m}}+26.7 as well as the gamma-ray–radio continuum luminosity correlation with {log}{L}0.1-100{GeV}=1.22× {log}{L}1.4{GHz}+13.3. The current survey of Fermi-LAT is on the verge of detecting more LIRGs/ULIRGs in the local universe, and we expect even more detections with deeper Fermi-LAT observations or the next generation of gamma-ray detectors.

  7. Cosmic chronometers: constraining the equation of state of dark energy. I: H(z) measurements

    SciTech Connect

    Stern, Daniel; Jimenez, Raul; Verde, Licia; Kamionkowski, Marc; Stanford, S. Adam E-mail: raul@icc.ub.edu E-mail: kamion@tapir.caltech.edu

    2010-02-01

    We present new determinations of the cosmic expansion history from red-envelope galaxies. We have obtained for this purpose high-quality spectra with the Keck-LRIS spectrograph of red-envelope galaxies in 24 galaxy clusters in the redshift range 0.2 < z < 1.0. We complement these Keck spectra with high-quality, publicly available archival spectra from the SPICES and VVDS surveys. We improve over our previous expansion history measurements in Simon et al. (2005) by providing two new determinations of the expansion history: H(z) = 97±62 km sec{sup −1} Mpc{sup −1} at z ≅ 0.5 and H(z) = 90±40 km sec{sup −1} Mpc{sup −1} at z ≅ 0.9. We discuss the uncertainty in the expansion history determination that arises from uncertainties in the synthetic stellar-population models. We then use these new measurements in concert with cosmic-microwave-background (CMB) measurements to constrain cosmological parameters, with a special emphasis on dark-energy parameters and constraints to the curvature. In particular, we demonstrate the usefulness of direct H(z) measurements by constraining the dark-energy equation of state parameterized by w{sub 0} and w{sub a} and allowing for arbitrary curvature. Further, we also constrain, using only CMB and H(z) data, the number of relativistic degrees of freedom to be 4±0.5 and their total mass to be < 0.2 eV, both at 1σ.

  8. Constraining the mSUGRA (minimal supergravity) parameter space using the entropy of dark matter halos

    SciTech Connect

    Nunez, Dario; Zavala, Jesus; Nellen, Lukas; Sussman, Roberto A; Cabral-Rosetti, Luis G; Mondragon, Myriam E-mail: jzavala@nucleares.unam.mx E-mail: lukas@nucleares.unam.mx E-mail: lgcabral@ciidet.edu.mx; Collaboration: For the Instituto Avanzado de Cosmologia, IAC

    2008-05-15

    We derive an expression for the entropy of a dark matter halo described using a Navarro-Frenk-White model with a core. The comparison of this entropy with that of dark matter in the freeze-out era allows us to constrain the parameter space in mSUGRA models. Moreover, combining these constraints with the ones obtained from the usual abundance criterion and demanding that these criteria be consistent with the 2{sigma} bounds for the abundance of dark matter: 0.112{<=}{Omega}{sub DM}h{sup 2}{<=}0.122, we are able to clearly identify validity regions among the values of tan{beta}, which is one of the parameters of the mSUGRA model. We found that for the regions of the parameter space explored, small values of tan{beta} are not favored; only for tan {beta} Asymptotically-Equal-To 50 are the two criteria significantly consistent. In the region where the two criteria are consistent we also found a lower bound for the neutralino mass, m{sub {chi}}{>=}141 GeV.

  9. Constraining the dark cusp in the galactic center by long-period binaries

    SciTech Connect

    Alexander, Tal; Pfuhl, Oliver

    2014-01-10

    Massive black holes (MBHs) in galactic nuclei are believed to be surrounded by a high-density stellar cluster, whose mass is mostly in hard-to-detect faint stars and compact remnants. Such dark cusps dominate the dynamics near the MBH: a dark cusp in the Galactic center (GC) of the Milky Way would strongly affect orbital tests of general relativity there; on cosmic scales, dark cusps set the rates of gravitational wave emission events from compact remnants that spiral into MBHs, and they modify the rates of tidal disruption events, to list only some implications. A recently discovered long-period massive young binary (with period P {sub 12} ≲ 1 yr, total mass M{sub 12}∼O(100 M{sub ⊙}), and age T {sub 12} ∼ 6 × 10{sup 6} yr), only ∼0.1 pc from the Galactic MBH, sets a lower bound on the stellar two-body relaxation timescale there, min t {sub rlx}∝(P {sub 12}/M {sub 12}){sup 2/3} T {sub 12} ∼ 10{sup 7} yr, and, correspondingly, an upper bound on the stellar number density, maxn{sub ⋆}∼few×10{sup 8}/〈M{sub ⋆}{sup 2}〉 pc{sup −3} (〈M{sub ⋆}{sup 2}〉{sup 1/2} is the rms stellar mass), based on the binary's survival against evaporation by the dark cusp. However, a conservative dynamical estimate, the drain limit, implies t{sub rlx}>O(10{sup 8} yr). Such massive binaries are thus too short-lived and tightly bound to constrain a dense relaxed dark cusp. We explore here in detail the use of longer-period, less massive, and longer-lived binaries (P {sub 12} ∼ few yr, M {sub 12} ∼ 2-4 M {sub ☉}, T {sub 12} ∼ 10{sup 8}-10{sup 10} yr), presently just below the detection threshold, for probing the dark cusp and develop the framework for translating their future detections among the giants in the GC into dynamical constraints.

  10. Fermi large area telescope search for photon lines from 30 to 200 GeV and dark matter implications.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Berenji, B; Bloom, E D; Bonamente, E; Borgland, A W; Bouvier, A; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Carrigan, S; Casandjian, J M; Cecchi, C; Celik, O; Chekhtman, A; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; do Couto E Silva, E; Drell, P S; Drlica-Wagner, A; Dubois, R; Dumora, D; Edmonds, Y; Essig, R; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grove, J E; Guillemot, L; Guiriec, S; Gustafsson, M; Hadasch, D; Harding, A K; Horan, D; Hughes, R E; Jackson, M S; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kuss, M; Lande, J; Latronico, L; Llena Garde, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Makeev, A; Mazziotta, M N; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Ozaki, M; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Rainò, S; Rando, R; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ripken, J; Ritz, S; Rodriguez, A Y; Roth, M; Sadrozinski, H F-W; Sander, A; Parkinson, P M Saz; Scargle, J D; Schalk, T L; Sellerholm, A; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Strickman, M S; Suson, D J; Tajima, H; Takahashi, H; Tanaka, T; Thayer, J B; Thayer, J G; Tibaldo, L; Torres, D F; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

    2010-03-01

    Dark matter (DM) particle annihilation or decay can produce monochromatic gamma rays readily distinguishable from astrophysical sources. gamma-ray line limits from 30 to 200 GeV obtained from 11 months of Fermi Large Area Space Telescope data from 20-300 GeV are presented using a selection based on requirements for a gamma-ray line analysis, and integrated over most of the sky. We obtain gamma-ray line flux upper limits in the range 0.6-4.5x10{-9} cm{-2} s{-1}, and give corresponding DM annihilation cross-section and decay lifetime limits. Theoretical implications are briefly discussed. PMID:20366979

  11. Markov chain Monte Carlo analysis to constrain dark matter properties with directional detection

    SciTech Connect

    Billard, J.; Mayet, F.; Santos, D.

    2011-04-01

    Directional detection is a promising dark matter search strategy. Indeed, weakly interacting massive particle (WIMP)-induced recoils would present a direction dependence toward the Cygnus constellation, while background-induced recoils exhibit an isotropic distribution in the Galactic rest frame. Taking advantage of these characteristic features, and even in the presence of a sizeable background, it has recently been shown that data from forthcoming directional detectors could lead either to a competitive exclusion or to a conclusive discovery, depending on the value of the WIMP-nucleon cross section. However, it is possible to further exploit these upcoming data by using the strong dependence of the WIMP signal with: the WIMP mass and the local WIMP velocity distribution. Using a Markov chain Monte Carlo analysis of recoil events, we show for the first time the possibility to constrain the unknown WIMP parameters, both from particle physics (mass and cross section) and Galactic halo (velocity dispersion along the three axis), leading to an identification of non-baryonic dark matter.

  12. Systematic uncertainties in constraining dark matter annihilation from the cosmic microwave background

    NASA Astrophysics Data System (ADS)

    Galli, Silvia; Slatyer, Tracy R.; Valdes, Marcos; Iocco, Fabio

    2013-09-01

    Anisotropies of the cosmic microwave background (CMB) have proven to be a very powerful tool to constrain dark matter annihilation at the epoch of recombination. However, CMB constraints are currently derived using a number of reasonable but yet untested assumptions that could potentially lead to a misestimation of the true bounds (or any reconstructed signal). In this paper we examine the potential impact of these systematic effects. In particular, we separately study the propagation of the secondary particles produced by annihilation in two energy regimes: first following the shower from the initial particle energy to the keV scale, and then tracking the resulting secondary particles from this scale to the absorption of their energy as heat, ionization, or excitation of the medium. We improve both the high- and low-energy parts of the calculation, in particular finding that our more accurate treatment of losses to sub-10.2 eV photons produced by scattering of high-energy electrons weakens the constraints on particular dark matter annihilation models by up to a factor of 2. On the other hand, we find that the uncertainties we examine for the low-energy propagation do not significantly affect the results for current and upcoming CMB data. We include the evaluation of the precise amount of excitation energy, in the form of Lyman-α photons, produced by the propagation of the shower, and examine the effects of varying the helium fraction and helium ionization fraction. In the recent literature, simple approximations for the fraction of energy absorbed in different channels have often been used to derive CMB constraints: we assess the impact of using accurate vs approximate energy fractions. Finally we check that the choice of recombination code (between RECFAST v1.5 and COSMOREC), to calculate the evolution of the free electron fraction in the presence of dark matter annihilation, introduces negligible differences.

  13. Limits on dark matter annihilation signals from the Fermi LAT 4-year measurement of the isotropic gamma-ray background

    NASA Astrophysics Data System (ADS)

    The Fermi LAT Collaboration

    2015-09-01

    We search for evidence of dark matter (DM) annihilation in the isotropic gamma-ray background (IGRB) measured with 50 months of Fermi Large Area Telescope (LAT) observations. An improved theoretical description of the cosmological DM annihilation signal, based on two complementary techniques and assuming generic weakly interacting massive particle (WIMP) properties, renders more precise predictions compared to previous work. More specifically, we estimate the cosmologically-induced gamma-ray intensity to have an uncertainty of a factor ~ 20 in canonical setups. We consistently include both the Galactic and extragalactic signals under the same theoretical framework, and study the impact of the former on the IGRB spectrum derivation. We find no evidence for a DM signal and we set limits on the DM-induced isotropic gamma-ray signal. Our limits are competitive for DM particle masses up to tens of TeV and, indeed, are the strongest limits derived from Fermi LAT data at TeV energies. This is possible thanks to the new Fermi LAT IGRB measurement, which now extends up to an energy of 820 GeV. We quantify uncertainties in detail and show the potential this type of search offers for testing the WIMP paradigm with a complementary and truly cosmological probe of DM particle signals.

  14. Limits on dark matter annihilation signals from the Fermi LAT 4-year measurement of the isotropic gamma-ray background

    SciTech Connect

    Ackermann, M.

    2015-09-02

    We search for evidence of dark matter (DM) annihilation in the isotropic gamma-ray background (IGRB) measured with 50 months of Fermi Large Area Telescope (LAT) observations. An improved theoretical description of the cosmological DM annihilation signal, based on two complementary techniques and assuming generic weakly interacting massive particle (WIMP) properties, renders more precise predictions compared to previous work. More specifically, we estimate the cosmologically-induced gamma-ray intensity to have an uncertainty of a factor ~ 20 in canonical setups. We consistently include both the Galactic and extragalactic signals under the same theoretical framework, and study the impact of the former on the IGRB spectrum derivation. We find no evidence for a DM signal and we set limits on the DM-induced isotropic gamma-ray signal. Our limits are competitive for DM particle masses up to tens of TeV and, indeed, are the strongest limits derived from Fermi LAT data at TeV energies. This is possible thanks to the new Fermi LAT IGRB measurement, which now extends up to an energy of 820 GeV. As a result, we quantify uncertainties in detail and show the potential this type of search offers for testing the WIMP paradigm with a complementary and truly cosmological probe of DM particle signals.

  15. Limits on dark matter annihilation signals from the Fermi LAT 4-year measurement of the isotropic gamma-ray background

    DOE PAGESBeta

    Ackermann, M.

    2015-09-02

    We search for evidence of dark matter (DM) annihilation in the isotropic gamma-ray background (IGRB) measured with 50 months of Fermi Large Area Telescope (LAT) observations. An improved theoretical description of the cosmological DM annihilation signal, based on two complementary techniques and assuming generic weakly interacting massive particle (WIMP) properties, renders more precise predictions compared to previous work. More specifically, we estimate the cosmologically-induced gamma-ray intensity to have an uncertainty of a factor ~ 20 in canonical setups. We consistently include both the Galactic and extragalactic signals under the same theoretical framework, and study the impact of the former onmore » the IGRB spectrum derivation. We find no evidence for a DM signal and we set limits on the DM-induced isotropic gamma-ray signal. Our limits are competitive for DM particle masses up to tens of TeV and, indeed, are the strongest limits derived from Fermi LAT data at TeV energies. This is possible thanks to the new Fermi LAT IGRB measurement, which now extends up to an energy of 820 GeV. As a result, we quantify uncertainties in detail and show the potential this type of search offers for testing the WIMP paradigm with a complementary and truly cosmological probe of DM particle signals.« less

  16. Fits to the Fermi-LAT GeV excess with right-handed sneutrino dark matter: Implications for direct and indirect dark matter searches and the LHC

    NASA Astrophysics Data System (ADS)

    Cerdeño, D. G.; Peiró, M.; Robles, S.

    2015-06-01

    We show that the right-handed (RH) sneutrino in the next-to-minimal supersymmetric standard model can account for the observed excess in the Fermi-LAT spectrum of gamma rays from the Galactic center, while fulfilling all the current experimental constraints from the LHC as well as from direct and indirect dark matter searches. We have explored the parameter space of this scenario, computed the gamma-ray spectrum for each phenomenologically viable solution and then performed a χ2 fit to the excess. Unlike previous studies based on model-independent interpretations, we have taken into account the full annihilation spectrum, without assuming pure annihilation channels. Furthermore, we have incorporated limits from direct detection experiments, LHC bounds and also the constraints from Fermi-LAT on dwarf spheroidal galaxies and gamma-ray spectral lines. In addition, we have estimated the effect of the most recent Fermi-LAT reprocessed data (pass 8). In general, we obtain good fits to the Galactic center excess (GCE) when the RH sneutrino annihilates mainly into pairs of light singletlike scalar or pseudoscalar Higgs bosons that subsequently decay in flight, producing four-body final states and spectral features that improve the goodness of the fit at large energies. The best fit (χ2=20.8 ) corresponds to a RH sneutrino with a mass of 64 GeV which annihilates preferentially into a pair of light singletlike pseudoscalar Higgs bosons (with masses of order 60 GeV). Besides, we have analyzed other channels that also provide good fits to the excess. Finally, we discuss the implications for direct and indirect detection searches paying special attention to the possible appearance of gamma-ray spectral features in near future Fermi-LAT analyses, as well as deviations from the Standard Model-like Higgs properties at the LHC. Remarkably, many of the scenarios that fit the GCE can also be probed by these other complementary techniques.

  17. Dark Higgs channel for Fermi GeV γ-ray excess

    NASA Astrophysics Data System (ADS)

    Ko, P.; Tang, Yong

    2016-02-01

    Dark Higgs is very generic in dark matter models where DM is stabilized by some spontaneously broken dark gauge symmetries. Motivated by tentative GeV scale γ-ray excess from the galactic center (GC), we investigate a scenario where a pair of dark matter X annihilates into a pair of dark Higgs H2, which subsequently decays into standard model particles through its mixing with SM Higgs boson. Besides the two-body decay of H2, we also include multibody decay channels of the dark Higgs. We find that the best-fit point is around MX simeq 95.0 GeV, MH2 simeq 86.7 GeV, langleσ vrangle simeq 4.0 × 10-26cm3/s and gives a p-value simeq 0.40. Implication of this result is described in the context of dark matter models with dark gauge symmetries. Since such a dark Higgs boson is very difficult to produce at colliders, indirect DM detections of cosmic γ-rays could be an important probe of dark sectors, complementary to collider searches.

  18. Discussion on the energy content of the galactic dark matter Bose-Einstein condensate halo in the Thomas-Fermi approximation

    SciTech Connect

    De Souza, J.C.C.; Pires, M.O.C. E-mail: marcelo.pires@ufabc.edu.br

    2014-03-01

    We show that the galactic dark matter halo, considered composed of an axionlike particles Bose-Einstein condensate [6] trapped by a self-graviting potential [5], may be stable in the Thomas-Fermi approximation since appropriate choices for the dark matter particle mass and scattering length are made. The demonstration is performed by means of the calculation of the potential, kinetic and self-interaction energy terms of a galactic halo described by a Boehmer-Harko density profile. We discuss the validity of the Thomas-Fermi approximation for the halo system, and show that the kinetic energy contribution is indeed negligible.

  19. Updated search for spectral lines from Galactic dark matter interactions with pass 8 data from the Fermi Large Area Telescope

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; Albert, A.; Anderson, B.; Atwood, W. B.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caputo, R.; Caragiulo, M.; Caraveo, P. A.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cuoco, A.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Desiante, R.; Digel, S. W.; Di Venere, L.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fegan, S. J.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.; Godfrey, G.; Gomez-Vargas, G. A.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Gustafsson, M.; Hewitt, J. W.; Hill, A. B.; Horan, D.; Jóhannesson, G.; Johnson, R. P.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Malyshev, D.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monzani, M. E.; Morselli, A.; Murgia, S.; Nuss, E.; Ohsugi, T.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paneque, D.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reposeur, T.; Ritz, S.; Sánchez-Conde, M.; Schulz, A.; Sgrò, C.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Tajima, H.; Takahashi, H.; Thayer, J. B.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Troja, E.; Vianello, G.; Werner, M.; Winer, B. L.; Wood, K. S.; Wood, M.; Zaharijas, G.; Zimmer, S.

    2015-06-01

    Dark matter in the Milky Way may annihilate directly into γ rays, producing a monoenergetic spectral line. Therefore, detecting such a signature would be strong evidence for dark matter annihilation or decay. We search for spectral lines in the Fermi Large Area Telescope observations of the Milky Way halo in the energy range 200 MeV-500 GeV using analysis methods from our most recent line searches. The main improvements relative to previous works are our use of 5.8 years of data reprocessed with the Pass 8 event-level analysis and the additional data resulting from the modified observing strategy designed to increase exposure of the Galactic center region. We search in five sky regions selected to optimize sensitivity to different theoretically motivated dark matter scenarios and find no significant detections. In addition to presenting the results from our search for lines, we also investigate the previously reported tentative detection of a line at 133 GeV using the new Pass 8 data.

  20. Searching for Dark Matter Annihilation from Milky Way Dwarf Spheroidal Galaxies with Six Years of Fermi Large Area Telescope Data.

    PubMed

    Ackermann, M; Albert, A; Anderson, B; Atwood, W B; Baldini, L; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Bissaldi, E; Blandford, R D; Bloom, E D; Bonino, R; Bottacini, E; Brandt, T J; Bregeon, J; Bruel, P; Buehler, R; Caliandro, G A; Cameron, R A; Caputo, R; Caragiulo, M; Caraveo, P A; Cecchi, C; Charles, E; Chekhtman, A; Chiang, J; Chiaro, G; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cuoco, A; Cutini, S; D'Ammando, F; de Angelis, A; de Palma, F; Desiante, R; Digel, S W; Di Venere, L; Drell, P S; Drlica-Wagner, A; Essig, R; Favuzzi, C; Fegan, S J; Ferrara, E C; Focke, W B; Franckowiak, A; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Gomez-Vargas, G A; Grenier, I A; Guiriec, S; Gustafsson, M; Hays, E; Hewitt, J W; Horan, D; Jogler, T; Jóhannesson, G; Kuss, M; Larsson, S; Latronico, L; Li, J; Li, L; Llena Garde, M; Longo, F; Loparco, F; Lubrano, P; Malyshev, D; Mayer, M; Mazziotta, M N; McEnery, J E; Meyer, M; Michelson, P F; Mizuno, T; Moiseev, A A; Monzani, M E; Morselli, A; Murgia, S; Nuss, E; Ohsugi, T; Orienti, M; Orlando, E; Ormes, J F; Paneque, D; Perkins, J S; Pesce-Rollins, M; Piron, F; Pivato, G; Porter, T A; Rainò, S; Rando, R; Razzano, M; Reimer, A; Reimer, O; Ritz, S; Sánchez-Conde, M; Schulz, A; Sehgal, N; Sgrò, C; Siskind, E J; Spada, F; Spandre, G; Spinelli, P; Strigari, L; Tajima, H; Takahashi, H; Thayer, J B; Tibaldo, L; Torres, D F; Troja, E; Vianello, G; Werner, M; Winer, B L; Wood, K S; Wood, M; Zaharijas, G; Zimmer, S

    2015-12-01

    The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some of the most dark matter (DM) dominated objects known. We report on γ-ray observations of Milky Way dSphs based on six years of Fermi Large Area Telescope data processed with the new Pass8 event-level analysis. None of the dSphs are significantly detected in γ rays, and we present upper limits on the DM annihilation cross section from a combined analysis of 15 dSphs. These constraints are among the strongest and most robust to date and lie below the canonical thermal relic cross section for DM of mass ≲100  GeV annihilating via quark and τ-lepton channels. PMID:26684107

  1. Constraint on the velocity dependent dark matter annihilation cross section from Fermi-LAT observations of dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Zhao, Yi; Bi, Xiao-Jun; Jia, Huan-Yu; Yin, Peng-Fei; Zhu, Feng-Rong

    2016-04-01

    The γ -ray observation of dwarf spheroidal satellites (dSph's) is an ideal approach for probing the dark matter (DM) annihilation signature. The latest Fermi-LAT dSph searches have set stringent constraints on the velocity independent annihilation cross section in the small DM mass range, which gives very strong constraints on the scenario to explain the AMS-02 positron excess by DM annihilation. However, the dSph constraints would change in the velocity dependent annihilation scenarios, because the velocity dispersion in the dSph's varies from that in the Milky Way. In this work, we use a likelihood map method to set constraints on the velocity dependent annihilation cross section from the Fermi-LAT observation of six dSph's. We consider three typical forms of the annihilation cross section, i.e. p-wave annihilation, Sommerfeld enhancement, and Breit-Wigner resonance. For the p-wave annihilation and Sommerfeld enhancement, the dSph limits would become much weaker and stronger compared with those for the velocity independent annihilation, respectively. For the Breit-Wigner annihilation, the dSph limits would vary depending on the model parameters. We show that the scenario to explain the AMS-02 positron excess by DM annihilation is still viable in the velocity dependent cases.

  2. The Fermi GeV excess: challenges for the dark matter interpretation

    NASA Astrophysics Data System (ADS)

    Calore, Francesca; Bozorgnia, Nassim; Lovell, Mark; Bertone, Gianfranco; Schaller, Matthieu; Frenk, Carlos S.; Crain, Robert A.; Schaye, Joop; Theuns, Tom; Trayford, James W.

    2016-05-01

    One of the most exciting recent results in the field of dark matter indirect searches has been the discovery of an excess emission in gamma rays from the Galactic centre above the standard astrophysical background. We show that current hydrodynamic simulations, namely simulated Milky Way-like galaxies within the “Evolution and Assembly of GaLaxies and their Environments” (EAGLE) project, challenge the possibility to interpret the GeV excess as due to annihilation of dark matter particles in the halo if the Milky Way.

  3. Constraining the unexplored period between the dark ages and reionization with observations of the global 21 cm signal

    SciTech Connect

    Pritchard, Jonathan R.; Loeb, Abraham

    2010-07-15

    Observations of the frequency dependence of the global brightness temperature of the redshifted 21 cm line of neutral hydrogen may be possible with single dipole experiments. In this paper, we develop a Fisher matrix formalism for calculating the sensitivity of such instruments to the 21 cm signal from reionization and the dark ages. We show that rapid reionization histories with duration {Delta}z < or approx. 2 can be constrained, provided that local foregrounds can be well modeled by low order polynomials. It is then shown that observations in the range {nu}=50-100 MHz can feasibly constrain the Ly{alpha} and x-ray emissivity of the first stars forming at z{approx}15-25, provided that systematic temperature residuals can be controlled to less than 1 mK. Finally, we demonstrate the difficulty of detecting the 21 cm signal from the dark ages before star formation.

  4. Improved limits on sterile neutrino dark matter using full-sky Fermi Gamma-ray Burst Monitor data

    NASA Astrophysics Data System (ADS)

    Ng, Kenny C. Y.; Horiuchi, Shunsaku; Gaskins, Jennifer M.; Smith, Miles; Preece, Robert

    2015-08-01

    A sterile neutrino of ˜keV mass is a well-motivated dark matter candidate. Its decay generates an x-ray line that offers a unique target for x-ray telescopes. For the first time, we use the Gamma-ray Burst Monitor (GBM) onboard the Fermi Gamma-Ray Space Telescope to search for sterile neutrino decay lines; our analysis covers the energy range 10-25 keV (sterile neutrino mass 20-50 keV), which is inaccessible to x-ray and gamma-ray satellites such as Chandra, Suzaku, XMM-Newton, and INTEGRAL. The extremely wide field of view of the GBM enables a large fraction of the Milky Way dark matter halo to be probed. After implementing careful data cuts, we obtain ˜53 days of full-sky observational data. We observe an excess of photons towards the Galactic center, as expected from astrophysical emission. We search for sterile neutrino decay lines in the energy spectrum, and find no significant signal. From this, we obtain upper limits on the sterile neutrino mixing angle as a function of mass. In the sterile neutrino mass range 25-40 keV, we improve upon previous upper limits by approximately an order of magnitude. Better understanding of detector and astrophysical backgrounds, as well as detector response, will further improve the sensitivity of a search with the GBM.

  5. Can Zee-Babu model implemented with scalar dark matter explain both Fermi-LAT 130 GeV γ-ray excess and neutrino physics?

    NASA Astrophysics Data System (ADS)

    Baek, Seungwon; Ko, P.; Okada, Hiroshi; Senaha, Eibun

    2014-09-01

    We extend the Zee-Babu model for the neutrino masses and mixings by first incorporating a scalar dark matter X with Z 2 symmetry and then X and a dark scalar φ with global U(1) symmetry. In the latter scenario the singly and doubly charged scalars that are new in the Zee-Babu model can explain the large annihilation cross section of a dark matter pair into two photons as hinted by the recent analysis of the Fermi γ-ray space telescope data. These new scalars can also enhance the B( H → γγ), as the recent LHC results may suggest. The dark matter relic density can be explained. The direct detection rate of the dark matter is predicted to be about one order of magnitude down from the current experimental bound in the first scenario.

  6. Confronting recent AMS-02 positron fraction and Fermi-LAT extragalactic γ-ray background measurements with gravitino dark matter

    NASA Astrophysics Data System (ADS)

    Carquín, Edson; Díaz, Marco A.; Gómez-Vargas, Germán A.; Panes, Boris; Viaux, Nicolás

    2016-03-01

    Recent positron flux fraction measurements in cosmic-rays (CR) made by the AMS-02 detector confirm and extend the evidence on the existence of a new (yet unknown) source of high energy electrons and positrons. We test the gravitino dark matter of bilinear R-parity violating supersymmetric models as this electrons/positrons source. Being a long lived weak-interacting and spin 3/2 particle, it offers several particularities which makes it an attractive dark matter candidate. We compute the electron, positron and γ-ray fluxes produced by each gravitino decay channel as it would be detected at the Earth's position. Combining the flux from the different decay modes we are able to reproduce AMS-02 measurements of the positron fraction, as well as the electron and positron fluxes, with a gravitino dark matter mass in the range 1-3 TeV and lifetime of ˜1.0-0.7×1026 s. The high statistics measurement of electron and positron fluxes, and the flattening in the behaviour of the positron fraction recently found by AMS-02 allow us to determine that the preferred gravitino decaying mode by the fit is W±τ∓, unlike previous analyses. Then we study the viability of these scenarios through their implication in γ-ray observations. For this we use the Extragalactic γ-ray Background recently reported by the Fermi-LAT Collaboration and a state-of-the-art model of its known contributors. Based on the γ-ray analysis we exclude the gravitino parameter space which provides an acceptable explanation of the AMS-02 data. Therefore, we conclude that the gravitino of bilinear R-parity violating models is ruled out as the unique primary source of electrons and positrons needed to explain the rise in the positron fraction.

  7. Decaying vs. annihilating dark matter in light of a tentative gamma-ray line

    SciTech Connect

    Buchmüller, Wilfried; Garny, Mathias E-mail: mathias.garny@desy.de

    2012-08-01

    Recently reported tentative evidence for a gamma-ray line in the Fermi-LAT data is of great potential interest for identifying the nature of dark matter. We compare the implications for decaying and annihilating dark matter taking the constraints from continuum gamma-rays, antiproton flux and morphology of the excess into account. We find that higgsino and wino dark matter are excluded, also for nonthermal production. Generically, the continuum gamma-ray flux severely constrains annihilating dark matter. Consistency of decaying dark matter with the spatial distribution of the Fermi-LAT excess would require an enhancement of the dark matter density near the Galactic center.

  8. Implications of the Fermi-LAT diffuse gamma-ray measurements on annihilating or decaying dark matter

    SciTech Connect

    Hütsi, Gert; Hektor, Andi; Raidal, Martti E-mail: andi.hektor@cern.ch

    2010-07-01

    We analyze the recently published Fermi-LAT diffuse gamma-ray measurements in the context of leptonically annihilating or decaying dark matter (DM) with the aim to explain simultaneously the isotropic diffuse gamma-ray and the PAMELA, Fermi and HESS (PFH) anomalous e{sup ±} data. Five different DM annihilation/decay channels 2e, 2μ, 2τ, 4e, or 4μ (the latter two via an intermediate light particle φ) are generated with PYTHIA. We calculate both the Galactic and extragalactic prompt and inverse Compton (IC) contributions to the resulting gamma-ray spectra. To find the Galactic IC spectra we use the interstellar radiation field model from the latest release of GALPROP. For the extragalactic signal we show that the amplitude of the prompt gamma-emission is very sensitive to the assumed model for the extragalactic background light. For our Galaxy we use the Einasto, NFW and cored isothermal DM density profiles and include the effects of DM substructure assuming a simple subhalo model. Our calculations show that for the annihilating DM the extragalactic gamma-ray signal can dominate only if rather extreme power-law concentration-mass relation C(M) is used, while more realistic C(M) relations make the extragalactic component comparable or subdominant to the Galactic signal. For the decaying DM the Galactic signal always exceeds the extragalactic one. In the case of annihilating DM the PFH favored parameters can be ruled out by gamma-ray constraints only if power-law C(M) relation is assumed. For DM decaying into 2μ or 4μ the PFH favored DM parameters are not in conflict with the gamma-ray data. We find that, due to the (almost) featureless Galactic IC spectrum and the DM halo substructure, annihilating DM may give a good simultaneous fit to the isotropic diffuse gamma-ray and to the PFH e{sup ±} data without being in clear conflict with the other Fermi-LAT gamma-ray measurements.

  9. The Prospects for Constraining Dark Energy withFuture X-ray Cluster Gas Mass Fraction Measurements

    SciTech Connect

    Rapetti, David; Allen, Steven W.

    2007-10-15

    We examine the ability of a future X-ray observatory, with capabilities similar to those planned for the Constellation-X mission, to constrain dark energy via measurements of the cluster X-ray gas mass fraction, fgas. We find that fgas measurements for a sample of {approx}500 hot (kT{approx}> 5keV), X-ray bright, dynamically relaxed clusters, to a precision of {approx}5 percent, can be used to constrain dark energy with a Dark Energy Task Force (DETF; Albrecht et al. 2006) figure of merit of 20-50. Such constraints are comparable to those predicted by the DETF for other leading, planned 'Stage IV' dark energy experiments. A future fgas experiment will be preceded by a large X-ray or SZ survey that will find hot, X-ray luminous clusters out to high redshifts. Short 'snapshot' observations with the new X-ray observatory should then be able to identify a sample of {approx}500 suitably relaxed systems. The redshift, temperature and X-ray luminosity range of interest has already been partially probed by existing X-ray cluster surveys which allow reasonable estimates of the fraction of clusters that will be suitably relaxed for fgas work to be made; these surveys also show that X-ray flux contamination from point sources is likely to be small for the majority of the targets of interest. Our analysis uses a Markov Chain Monte Carlo method which fully captures the relevant degeneracies between parameters and facilities the incorporation of priors and systematic uncertainties in the analysis. We explore the effects of such uncertainties, for scenarios ranging from optimistic to pessimistic. We conclude that the fgas experiment offers a competitive and complementary approach to the best other large, planned dark energy experiments. In particular, the fgas experiment will provide tight constraints on the mean matter and dark energy densities, with a peak sensitivity for dark energy work at redshifts midway between those of supernovae and baryon acoustic oscillation

  10. Slow-light probe of Fermi pairing through an atom-molecule dark state

    SciTech Connect

    Jing, H.; Deng, Y.; Meystre, P.

    2011-06-15

    We consider the two-color photoassociation of a quantum degenerate atomic gas into ground-state diatomic molecules via a molecular dark state. This process can be described in terms of a {Lambda} level scheme that is formally analogous to the situation in electromagnetically induced transparency in atomic systems and therefore can result in slow-light propagation. We show that the group velocity of the light field depends explicitly on whether the atoms are bosons or fermions, as well as on the existence or absence of a pairing gap in the case of fermions, so that the measurement of the group velocity realizes a nondestructive diagnosis of the atomic state and the pairing gap.

  11. A Tale of Tails. Dark Matter Interpretations of the Fermi GeV Excess in Light of Background Model Systematics

    SciTech Connect

    Calore, Francesca; Cholis, Ilias; McCabe, Christopher; Weniger, Christoph

    2015-03-10

    Several groups have identified an extended excess of gamma rays over the modeled foreground and background emissions towards the Galactic center (GC) based on observations with the Fermi Large Area Telescope. The excess emission is compatible in morphology and spectrum with a telltale sign from dark matter (DM) annihilation. Here, we present a critical reassessment of DM interpretations of the GC signal in light of the foreground and background uncertainties that some of us recently outlaid in Calore et al. (2014). We also find that a much larger number of DM models fits the gamma-ray data than previously noted. In particular: (1) In the case of DM annihilation into b¯b, we find that even large DM masses up to mχ≃74 GeV are allowed at p-value >0.05. (2) Surprisingly, annihilation into nonrelativistic hh gives a good fit to the data. (3) The inverse Compton emission from μ+μ- with mχ~60–70 GeV can also account for the excess at higher latitudes, |b|>2°, both in its spectrum and morphology. We also present novel constraints on a large number of mixed annihilation channels, including cascade annihilation involving hidden sector mediators. Finally, we show that the current limits from dwarf spheroidal observations are not in tension with a DM interpretation when uncertainties on the DM halo profile are accounted for.

  12. A Tale of Tails. Dark Matter Interpretations of the Fermi GeV Excess in Light of Background Model Systematics

    DOE PAGESBeta

    Calore, Francesca; Cholis, Ilias; McCabe, Christopher; Weniger, Christoph

    2015-03-10

    Several groups have identified an extended excess of gamma rays over the modeled foreground and background emissions towards the Galactic center (GC) based on observations with the Fermi Large Area Telescope. The excess emission is compatible in morphology and spectrum with a telltale sign from dark matter (DM) annihilation. Here, we present a critical reassessment of DM interpretations of the GC signal in light of the foreground and background uncertainties that some of us recently outlaid in Calore et al. (2014). We also find that a much larger number of DM models fits the gamma-ray data than previously noted. Inmore » particular: (1) In the case of DM annihilation into b¯b, we find that even large DM masses up to mχ≃74 GeV are allowed at p-value >0.05. (2) Surprisingly, annihilation into nonrelativistic hh gives a good fit to the data. (3) The inverse Compton emission from μ+μ- with mχ~60–70 GeV can also account for the excess at higher latitudes, |b|>2°, both in its spectrum and morphology. We also present novel constraints on a large number of mixed annihilation channels, including cascade annihilation involving hidden sector mediators. Finally, we show that the current limits from dwarf spheroidal observations are not in tension with a DM interpretation when uncertainties on the DM halo profile are accounted for.« less

  13. Limits to dark matter annihilation cross-section from a combined analysis of MAGIC and Fermi-LAT observations of dwarf satellite galaxies

    DOE PAGESBeta

    Ahnen, M. L.

    2016-02-16

    Here, we present the first joint analysis of gamma-ray data from the MAGIC Cherenkov telescopes and the Fermi Large Area Telescope (LAT) to search for gamma-ray signals from dark matter annihilation in dwarf satellite galaxies. We combine 158 hours of Segue 1 observations with MAGIC with 6-year observations of 15 dwarf satellite galaxies by the Fermi-LAT. We obtain limits on the annihilation cross-section for dark matter particle masses between 10 GeV and 100 TeV - the widest mass range ever explored by a single gamma-ray analysis. These limits improve on previously published Fermi-LAT and MAGIC results by up to amore » factor of two at certain masses. Our new inclusive analysis approach is completely generic and can be used to perform a global, sensitivity-optimized dark matter search by combining data from present and future gamma-ray and neutrino detectors.« less

  14. Search for gamma-ray emission from dark matter annihilation in the large magellanic cloud with the fermi large area telescope

    DOE PAGESBeta

    Buckley, Matthew R.; Charles, Eric; Gaskins, Jennifer M.; Brooks, Alyson M.; Drlica-Wagner, Alex; Martin, Pierrick; Zhao, Geng

    2015-05-05

    At a distance of 50 kpc and with a dark matter mass of ~1010 M⊙, the large magellanic cloud (LMC) is a natural target for indirect dark matter searches. We use five years of data from the Fermi Large Area Telescope (LAT) and updated models of the gamma-ray emission from standard astrophysical components to search for a dark matter annihilation signal from the LMC. We perform a rotation curve analysis to determine the dark matter distribution, setting a robust minimum on the amount of dark matter in the LMC, which we use to set conservative bounds on the annihilation cross section.more » The LMC emission is generally very well described by the standard astrophysical sources, with at most a 1–2σ excess identified near the kinematic center of the LMC once systematic uncertainties are taken into account. As a result, we place competitive bounds on the dark matter annihilation cross section as a function of dark matter particle mass and annihilation channel.« less

  15. Search for gamma-ray emission from dark matter annihilation in the large magellanic cloud with the fermi large area telescope

    SciTech Connect

    Buckley, Matthew R.; Charles, Eric; Gaskins, Jennifer M.; Brooks, Alyson M.; Drlica-Wagner, Alex; Martin, Pierrick; Zhao, Geng

    2015-05-05

    At a distance of 50 kpc and with a dark matter mass of ~1010 M, the large magellanic cloud (LMC) is a natural target for indirect dark matter searches. We use five years of data from the Fermi Large Area Telescope (LAT) and updated models of the gamma-ray emission from standard astrophysical components to search for a dark matter annihilation signal from the LMC. We perform a rotation curve analysis to determine the dark matter distribution, setting a robust minimum on the amount of dark matter in the LMC, which we use to set conservative bounds on the annihilation cross section. The LMC emission is generally very well described by the standard astrophysical sources, with at most a 1–2σ excess identified near the kinematic center of the LMC once systematic uncertainties are taken into account. As a result, we place competitive bounds on the dark matter annihilation cross section as a function of dark matter particle mass and annihilation channel.

  16. Effects of time-varying in SNLS3 on constraining interacting dark energy models

    NASA Astrophysics Data System (ADS)

    Wang, Shuang; Wang, Yong-Zhen; Geng, Jia-Jia; Zhang, Xin

    2014-11-01

    It has been found that, for the Supernova Legacy Survey three-year (SNLS3) data, there is strong evidence for the redshift evolution of the color-luminosity parameter . In this paper, adopting the -cold-dark-matter (CDM) model and considering its interacting extensions (with three kinds of interaction between dark sectors), we explore the evolution of and its effects on parameter estimation. In addition to the SNLS3 data, we also use the latest Planck distance priors data, the galaxy clustering data extracted from sloan digital sky survey data release 7 and baryon oscillation spectroscopic survey, as well as the direct measurement of Hubble constant from the Hubble Space Telescope observation. We find that, for all the interacting dark energy (IDE) models, adding a parameter of can reduce by 34, indicating that a constant is ruled out at 5.8 confidence level. Furthermore, it is found that varying can significantly change the fitting results of various cosmological parameters: for all the dark energy models considered in this paper, varying yields a larger fractional CDM densities and a larger equation of state ; on the other side, varying yields a smaller reduced Hubble constant for the CDM model, but it has no impact on for the three IDE models. This implies that there is a degeneracy between and coupling parameter . Our work shows that the evolution of is insensitive to the interaction between dark sectors, and then highlights the importance of considering 's evolution in the cosmology fits.

  17. Search for Gamma-ray Emission from Dark Matter Annihilation in the Small Magellanic Cloud with the Fermi Large Area Telescope

    NASA Astrophysics Data System (ADS)

    Caputo, Regina; Buckley, Matthew; Martin, Pierrick; Charles, Eric; Brooks, Alyson; Drlica-Wagner, Alex; Gaskins, Jennifer; Wood, Matthew

    2016-04-01

    The Small Magellanic Cloud (SMC) is the second-largest satellite galaxy of the Milky Way and is only 60 kpc away. As a nearby, massive, and dense object with relatively low astrophysical backgrounds, it is a natural target for dark matter indirect detection searches. In this analysis, we use six years of Pass 8 data from the Fermi Large Area Telescope to search for gamma-ray signals of dark matter annihilation in the SMC. Using data-driven fits to the gamma-ray backgrounds, and a combination of cosmological N-body simulations and direct measurements of rotation curves to estimate the SMC dark matter density profile, we found that the SMC was well described by standard astrophysical sources, and no signal from dark matter annihilation was detected. We set conservative upper limits on the dark matter annihilation cross section. These constraints are in agreement with stronger constraints set by searches in the Large Magellanic Cloud and approach the canonical thermal relic cross section at dark matter masses lower than 10 GeV in the bb and τ+τ- annihilation channels.

  18. Cold or warm? Constraining dark matter with primeval galaxies and cosmic reionization after Planck

    NASA Astrophysics Data System (ADS)

    Lapi, A.; Danese, L.

    2015-09-01

    Dark matter constitutes the great majority of the matter content in the Universe, but its microscopic nature remains an intriguing mystery, with profound implications for particle physics, astrophysics and cosmology. Here we shed light on the longstanding issue of whether the dark matter is warm or cold by combining the measurements of the galaxy luminosity functions out to high redshifts 0z~ 1 from the Hubble Space Telescope with the recent cosmological data on the reionization history of the Universe from the Planck mission. We derive robust and tight bounds on the mass of warm dark matter particle, finding that the current data require it to be in the narrow range between 2 and 3 keV . In addition, we show that a mass not exceeding 3 keV is also concurrently indicated by astrophysical constraints related to the local number of satellites in Milky Way-sized galaxies, though it is in marginal tension with analysis of the Lyman-α forest. For warm dark matter masses above 3 keV as well as for cold dark matter, to satisfy the Planck constraints on the optical depth and not to run into the satellite problem would require invoking astrophysical processes that inhibit galaxy formation in halos with mass MH lesssim few × 10 8 Msolar, corresponding to a limiting UV magnitude MUV≈ -11. Anyway, we predict a downturn of the galaxy luminosity function at z~ 8 faintward of MUV≈ -12, and stress that its detailed shape is extremely informative both on particle physics and on the astrophysics of galaxy formation in small halos. These expectations will be tested via the Hubble Frontier Fields and with the advent of the James Webb Space Telescope, which will enable probing the very faint end of the galaxy luminosity function out to z ~ 8-10.

  19. Complementarity of Galactic radio and collider data in constraining WIMP dark matter models

    SciTech Connect

    Mambrini, Yann; Tytgat, Michel H.G.; Zaharijas, Gabrijela; Zaldívar, Bryan E-mail: mtytgat@ulb.ac.be E-mail: bryan.zaldivar@uam.es

    2012-11-01

    In this work we confront dark matter models to constraints that may be derived from radio synchrotron radiation from the Galaxy, taking into account the astrophysical uncertainties and we compare these to bounds set by accelerator and complementary indirect dark matter searches. Specifically we apply our analysis to three popular particle physics models. First, a generic effective operator approach, in which case we set bounds on the corresponding mass scale, and then, two specific UV completions, the Z' and Higgs portals. We show that for many candidates, the radio synchrotron limits are competitive with the other searches, and could even give the strongest constraints (as of today) with some reasonable assumptions regarding the astrophysical uncertainties.

  20. Coarse dark patterning functionally constrains adaptive shifts from aposematism to crypsis in strawberry poison frogs.

    PubMed

    Qvarnström, Anna; Rudh, Andreas; Edström, Torkel; Ödeen, Anders; Løvlie, Hanne; Tullberg, Birgitta S

    2014-10-01

    Ecological specialization often requires tight coevolution of several traits, which may constrain future evolutionary pathways and make species more prone to extinction. Aposematism and crypsis represent two specialized adaptations to avoid predation. We tested whether the combined effects of color and pattern on prey conspicuousness functionally constrain or facilitate shifts between these two adaptations. We combined data from 17 natural populations of strawberry poison frogs, Oophaga pumilio with an experimental approach using digitalized images of frogs and chickens as predators. We show that bright coloration often co-occurs with coarse patterning among the natural populations. Dull green frogs with coarse patterning are rare in nature but in the experiment they were as easily detected as bright red frogs suggesting that this trait combination represents a transient evolutionary state toward aposematism. Hence, a gain of either bright color or coarse patterning leads to conspicuousness, but a transition back to crypsis would be functionally constrained in populations with both bright color and coarse patterning by requiring simultaneous changes in two traits. Thus, populations (or species) signaling aposematism by conspicuous color should be less likely to face an evolutionary dead end and more likely to radiate than populations with both conspicuous color and coarse patterning. PMID:24990085

  1. Constraining dark matter-neutrino interactions using the CMB and large-scale structure

    NASA Astrophysics Data System (ADS)

    Wilkinson, Ryan J.; Bœhm, Céline; Lesgourgues, Julien

    2014-05-01

    We present a new study on the elastic scattering cross section of dark matter (DM) and neutrinos using the latest cosmological data from Planck and large-scale structure experiments. We find that the strongest constraints are set by the Lyman-α forest, giving σDM-ν lesssim 10-33(mDM/GeV) cm2 if the cross section is constant and a present-day value of σDM-ν lesssim 10-45(mDM/GeV) cm2 if it scales as the temperature squared. These are the most robust limits on DM-neutrino interactions to date, demonstrating that one can use the distribution of matter in the Universe to probe dark (``invisible") interactions. Additionally, we show that scenarios involving thermal MeV DM and a constant elastic scattering cross section naturally predict (i) a cut-off in the matter power spectrum at the Lyman-α scale, (ii) Neff ~ 3.5 ± 0.4, (iii) H0 ~ 71 ± 3km s-1Mpc-1 and (iv) the possible generation of neutrino masses.

  2. Constraining dark matter-neutrino interactions using the CMB and large-scale structure

    SciTech Connect

    Wilkinson, Ryan J.; Boehm, Céline; Lesgourgues, Julien E-mail: julien.lesgourgues@cern.ch

    2014-05-01

    We present a new study on the elastic scattering cross section of dark matter (DM) and neutrinos using the latest cosmological data from Planck and large-scale structure experiments. We find that the strongest constraints are set by the Lyman-α forest, giving σ{sub DM−ν} ∼< 10{sup −33}(m{sub DM}/GeV) cm{sup 2} if the cross section is constant and a present-day value of σ{sub DM−ν} ∼< 10{sup −45}(m{sub DM}/GeV) cm{sup 2} if it scales as the temperature squared. These are the most robust limits on DM-neutrino interactions to date, demonstrating that one can use the distribution of matter in the Universe to probe dark (''invisible{sup )} interactions. Additionally, we show that scenarios involving thermal MeV DM and a constant elastic scattering cross section naturally predict (i) a cut-off in the matter power spectrum at the Lyman-α scale, (ii) N{sub eff} ∼ 3.5 ± 0.4, (iii) H{sub 0} ∼ 71 ± 3km s{sup −1}Mpc{sup −1} and (iv) the possible generation of neutrino masses.

  3. Dark matter or point sources? Utilizing the 1-pt PDF to understand the origin of the GeV excess seen by the Fermi LAT detector

    NASA Astrophysics Data System (ADS)

    Harrison, Natalie; Gaskins, Jennifer; Fermi LAT Collaboration

    2015-04-01

    An excess of gamma rays from the Inner Galaxy in the Fermi LAT data has been identified. This emission has been interpreted as a possible signature of the annihilation of dark matter particles, or as originating from a collection of unresolved point sources, such as gamma-ray millisecond pulsars. We explore the clustering properties of the diffuse emission arising from a population of gamma-ray point sources and from the annihilation of dark matter particles in the halo of the Galaxy using the 1-pt probability distribution function of counts in pixels (1pt-PDF, the number of pixels with a specified number of counts as a function of counts); this approach is also known as fluctuation analysis or P(D) analysis. We analyze the 1-pt PDF of the GeV excess within a +/- 5 degree box around the Galactic Center. For both dark matter and point sources we adopt the spatial distribution and spectrum to fit the GeV excess. We determine the contributions to the 1-pt PDF from the Galactic diffuse and isotropic diffuse emissions, dark matter, and point sources, and discuss the implications of this analysis for the origin of the GeV excess.

  4. Dark matter or point sources? Utilizing the 1-pt PDF to understand the origin of the GeV excess seen by the Fermi LAT detector

    NASA Astrophysics Data System (ADS)

    Harrison, Natalie; Siegal-Gaskins, Jennifer M.

    2015-01-01

    An excess of gamma rays from the Inner Galaxy in the Fermi LAT data has been identified. This emission has been interpreted as a possible signature of the annihilation of dark matter particles, or as originating from a collection of unresolved point sources, such as gamma-ray millisecond pulsars. We explore the clustering properties of the diffuse emission arising from a population of gamma-ray point sources and from the annihilation of dark matter particles in the halo of the Galaxy using the 1-pt probability distribution function of counts in pixels (1pt-PDF, the number of pixels with a specified number of counts as a function of counts); this approach is also known as fluctuation analysis or P(D) analysis. We analyze the 1-pt PDF of the GeV excess within a +/- 5 degree box around the Galactic Center. For both dark matter and point sources we adopt the spatial distribution and spectrum to fit the GeV excess. We determine the contributions to the 1-pt PDF from the Galactic diffuse and isotropic diffuse emission, dark matter, and point sources, and discuss the implications of this analysis for the origin of the GeV excess.

  5. The Fermi-LAT gamma-ray excess at the Galactic Center in the singlet-doublet fermion dark matter model

    NASA Astrophysics Data System (ADS)

    Horiuchi, Shunsaku; Macias, Oscar; Restrepo, Diego; Rivera, Andrés; Zapata, Oscar; Silverwood, Hamish

    2016-03-01

    The singlet-doublet fermion dark matter model (SDFDM) provides a good DM candidate as well as the possibility of generating neutrino masses radiatively. The search and identification of DM requires the combined effort of both indirect and direct DM detection experiments in addition to the LHC. Remarkably, an excess of GeV gamma rays from the Galactic Center (GCE) has been measured with the Fermi Large Area Telescope (LAT) which appears to be robust with respect to changes in the diffuse galactic background modeling. Although several astrophysical explanations have been proposed, DM remains a simple and well motivated alternative. In this work, we examine the sensitivities of dark matter searches in the SDFDM scenario using Fermi-LAT, CTA, IceCube/DeepCore, LUX, PICO and LHC with an emphasis on exploring the regions of the parameter space that can account for the GCE. We find that DM particles present in this model with masses close to ~ 99 GeV and ~ (173-190) GeV annihilating predominantly into the W+W- channel and tbar t channel respectively, provide an acceptable fit to the GCE while being consistent with different current experimental bounds. We also find that much of the obtained parameter space can be ruled out by future direct search experiments like LZ and XENON-1T, in case of null results by these detectors. Interestingly, we show that the most recent data by LUX is starting to probe the best fit region in the SDFDM model.

  6. Reconstructing WIMP properties through an interplay of signal measurements in direct detection, Fermi-LAT, and CTA searches for dark matter

    NASA Astrophysics Data System (ADS)

    Roszkowski, Leszek; Sessolo, Enrico Maria; Trojanowski, Sebastian; Williams, Andrew J.

    2016-08-01

    We examine the projected ability to reconstruct the mass, scattering, and annihilation cross section of dark matter in the new generation of large underground detectors, XENON-1T, SuperCDMS, and DarkSide-G2, in combination with diffuse gamma radiation from expected 15 years of data from Fermi-LAT observation of 46 local spiral dwarf galaxies and projected CTA sensitivity to a signal from the Galactic Center. To this end we consider several benchmark points spanning a wide range of WIMP mass, different annihilation final states, and large enough event rates to warrant detection in one or more experiments. As previously shown, below some 100 GeV only direct detection experiments will in principle be able to reconstruct WIMP mass well. This may, in case a signal at Fermi-LAT is also detected, additionally help restricting σv and the allowed decay branching rates. In the intermediate range between some 100 GeV and up a few hundred GeV, direct and indirect detection experiments can be used in complementarity to ameliorate the respective determinations, which in individual experiments can at best be rather poor, thus making the WIMP reconstruction in this mass range very challenging. At large WIMP mass, ~ 1 TeV, CTA will have the ability to reconstruct mass, annihilation cross section, and the allowed decay branching rates to very good precision for the τ+τ‑ or purely leptonic final state, good for the W+W‑ case, and rather poor for bbar b. A substantial improvement can potentially be achieved by reducing the systematic uncertainties, increasing exposure, or by an additional measurement at Fermi-LAT that would help reconstruct the annihilation cross section and the allowed branching fractions to different final states.

  7. MilkyWay@home: Harnessing volunteer computers to constrain dark matter in the Milky Way

    NASA Astrophysics Data System (ADS)

    Newberg, Heidi Jo; Newby, Matthew; Desell, Travis; Magdon-Ismail, Malik; Szymanski, Boleslaw; Varela, Carlos

    2014-01-01

    MilkyWay@home is a volunteer computing project that allows people from every country in the world to volunteer their otherwise idle processors to Milky Way research. Currently, more than 25,000 people (150,000 since November 9, 2007) contribute about half a PetaFLOPS of computing power to our project. We currently run two types of applications: one application fits the spatial density profile of tidal streams using statistical photometric parallax, and the other application finds the N-body simulation parameters that produce tidal streams that best match the measured density profile of known tidal streams. The stream fitting application is well developed and is producing published results. The Sagittarius dwarf leading tidal tail has been fit, and the algorithm is currently running on the trailing tidal tail and bifurcated pieces. We will soon have a self-consistent model for the density of the smooth component of the stellar halo and the largest tidal streams. The N-body application has been implemented for fitting dwarf galaxy progenitor properties only, and is in the testing stages. We use an Earth-Mover Distance method to measure goodness-of-fit for density of stars along the tidal stream. We will add additional spatial dimensions as well as kinematic measures in a piecemeal fashion, with the eventual goal of fitting the orbit and parameters of the Milky Way potential (and thus the density distribution of dark matter) using multiple tidal streams.

  8. Constraining the dynamical dark energy parameters: Planck-2013 vs WMAP9

    SciTech Connect

    Novosyadlyj, B.; Sergijenko, O.; Durrer, R.; Pelykh, V. E-mail: olka@astro.franko.lviv.ua E-mail: pelykh@iapmm.lviv.ua

    2014-05-01

    We determine the best-fit values and confidence limits for dynamical dark energy parameters together with other cosmological parameters on the basis of different datasets which include WMAP9 or Planck-2013 results on CMB anisotropy, BAO distance ratios from recent galaxy surveys, magnitude-redshift relations for distant SNe Ia from SNLS3 and Union2.1 samples and the HST determination of the Hubble constant. We use a Markov Chain Monte Carlo routine to map out the likelihood in the multi-dimensional parameter space. We show that the most precise determination of cosmological parameters with the narrowest confidence limits is obtained for the Planck+HST+BAO+SNLS3 dataset. The best-fit values and 2σ confidence limits for cosmological parameters in this case are Ω{sub de} = 0.718±0.022, w{sub 0} = −1.15{sup +0.14}{sub −0.16}, c{sub a}{sup 2} = −1.15{sup +0.02}{sub −0.46}, Ω{sub b}h{sup 2} = 0.0220±0.0005, Ω{sub cdm}h{sup 2} = 0.121±0.004, h = 0.713±0.027, n{sub s} = 0.958{sup +0.014}{sub −0.010}, A{sub s} = (2.215{sup +0.093}{sub −0.101})⋅10{sup −9}, τ{sub rei} = 0.093{sup +0.022}{sub −0.028}. For this dataset, the ΛCDM model is just outside the 2σ confidence region, while for the dataset WMAP9+HST+BAO+SNLS3 the ΛCDM model is only 1σ away from the best fit. The tension in the determination of some cosmological parameters on the basis of two CMB datasets WMAP9 and Planck-2013 is highlighted.

  9. CONSTRAINING THE STAR FORMATION HISTORIES IN DARK MATTER HALOS. I. CENTRAL GALAXIES

    SciTech Connect

    Yang Xiaohu; Mo, H. J.; Lu Zhankui; Van den Bosch, Frank C.; Bonaca, Ana; Li Shijie; Lu Yi; Lu Yu

    2013-06-20

    Using the self-consistent modeling of the conditional stellar mass functions across cosmic time by Yang et al., we make model predictions for the star formation histories (SFHs) of central galaxies in halos of different masses. The model requires the following two key ingredients: (1) mass assembly histories of central and satellite galaxies and (2) local observational constraints of the star formation rates (SFRs) of central galaxies as a function of halo mass. We obtain a universal fitting formula that describes the (median) SFH of central galaxies as a function of halo mass, galaxy stellar mass, and redshift. We use this model to make predictions for various aspects of the SFRs of central galaxies across cosmic time. Our main findings are the following. (1) The specific star formation rate at high z increases rapidly with increasing redshift [{proportional_to}(1 + z){sup 2.5}] for halos of a given mass and only slowly with halo mass ({proportional_to}M{sub h}{sup 0.12}) at a given z, in almost perfect agreement with the specific mass accretion rate of dark matter halos. (2) The ratio between the SFR in the main branch progenitor and the final stellar mass of a galaxy peaks roughly at a constant value, {approx}10{sup -9.3} h {sup 2} yr{sup -1}, independent of the halo mass or the final stellar mass of the galaxy. However, the redshift at which the SFR peaks increases rapidly with halo mass. (3) More than half of the stars in the present-day universe were formed in halos with 10{sup 11.1} h {sup -1} M{sub Sun} < M{sub h} < 10{sup 12.3} h {sup -1} M{sub Sun} in the redshift range 0.4 < z < 1.9. (4) The star formation efficiencies (SFEs) of central galaxies reveal a ''downsizing'' behavior, in that the halo ''quenching'' mass, at which the SFE peaks, shifts from {approx}10{sup 12.5} h {sup -1} M{sub Sun} at z {approx}> 3.5 to {approx}10{sup 11.3} h {sup -1} M{sub Sun} at z = 0. (5) At redshift z {approx}> 2.5 more than 99% of the stars in the progenitors of massive

  10. Searching for dark matter annihilation from Milky Way dwarf spheroidal galaxies with six years of Fermi Large Area Telescope data

    DOE PAGESBeta

    Ackermann, M.

    2015-11-30

    The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some of the most dark matter (DM) dominated objects known. We report on γ-ray observations of Milky Way dSphs based on six years of Fermi Large Area Telescope data processed with the new Pass8 event-level analysis. None of the dSphs are significantly detected in γ rays, and we present upper limits on the DM annihilation cross section from a combined analysis of 15 dSphs. As a result, these constraints are among the strongest and most robust to date and lie below the canonical thermal relic cross section for DMmore » of mass ≲100 GeV annihilating via quark and τ-lepton channels.« less

  11. Searching for dark matter annihilation from Milky Way dwarf spheroidal galaxies with six years of Fermi Large Area Telescope data

    SciTech Connect

    Ackermann, M.

    2015-11-30

    The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some of the most dark matter (DM) dominated objects known. We report on γ-ray observations of Milky Way dSphs based on six years of Fermi Large Area Telescope data processed with the new Pass8 event-level analysis. None of the dSphs are significantly detected in γ rays, and we present upper limits on the DM annihilation cross section from a combined analysis of 15 dSphs. As a result, these constraints are among the strongest and most robust to date and lie below the canonical thermal relic cross section for DM of mass ≲100 GeV annihilating via quark and τ-lepton channels.

  12. A possible explanation of low energy γ-ray excess from galactic centre and Fermi bubble by a Dark Matter model with two real scalars

    SciTech Connect

    Modak, Kamakshya Prasad; Majumdar, Debasish

    2015-03-09

    We promote the idea of multi-component Dark Matter (DM) to explain results from both direct and indirect detection experiments. In these models as contribution of each DM candidate to relic abundance is summed up to meet WMAP/Planck measurements of Ω{sub DM}, these candidates have larger annihilation cross-sections compared to the single-component DM models. We illustrate this fact by introducing an extra scalar to the popular single real scalar DM model. We also present detailed calculations for the vacuum stability bounds, perturbative unitarity and triviality constraints on this model. As direct detection experimental results still show some conflict, we kept our options open, discussing different scenarios with different DM mass zones. In the framework of our model we make an interesting observation: the existing direct detection experiments like CDMS II, CoGeNT, CRESST II, XENON 100 or LUX together with the observation of excess low energy γ-ray from galactic centre and Fermi bubble by Fermi Gamma-ray Space Telescope (FGST) already have the capability to distinguish between different DM halo profiles.

  13. A possible explanation of low energy γ-ray excess from galactic centre and Fermi bubble by a Dark Matter model with two real scalars

    NASA Astrophysics Data System (ADS)

    Prasad Modak, Kamakshya; Majumdar, Debasish; Rakshit, Subhendu

    2015-03-01

    We promote the idea of multi-component Dark Matter (DM) to explain results from both direct and indirect detection experiments. In these models as contribution of each DM candidate to relic abundance is summed up to meet WMAP/Planck measurements of ΩDM, these candidates have larger annihilation cross-sections compared to the single-component DM models. We illustrate this fact by introducing an extra scalar to the popular single real scalar DM model. We also present detailed calculations for the vacuum stability bounds, perturbative unitarity and triviality constraints on this model. As direct detection experimental results still show some conflict, we kept our options open, discussing different scenarios with different DM mass zones. In the framework of our model we make an interesting observation: the existing direct detection experiments like CDMS II, CoGeNT, CRESST II, XENON 100 or LUX together with the observation of excess low energy γ-ray from galactic centre and Fermi bubble by Fermi Gamma-ray Space Telescope (FGST) already have the capability to distinguish between different DM halo profiles.

  14. The WiggleZ Dark Energy Survey: constraining the evolution of Newton's constant using the growth rate of structure

    SciTech Connect

    Nesseris, Savvas; Blake, Chris; Davis, Tamara; Parkinson, David E-mail: cblake@astro.swin.edu.au E-mail: d.parkinson@uq.edu.au

    2011-07-01

    We constrain the evolution of Newton's constant using the growth rate of large-scale structure measured by the WiggleZ Dark Energy Survey in the redshift range 0.1 < z < 0.9. We use this data in two ways. Firstly we constrain the matter density of the Universe, Ω{sub m} (assuming General Relativity), and use this to construct a diagnostic to detect the presence of an evolving Newton's constant. Secondly we directly measure the evolution of Newton's constant, G{sub eff}, that appears in Modified Gravity theories, without assuming General Relativity to be true. The novelty of these approaches are that, contrary to other methods, they do not require knowledge of the expansion history of the Universe, H(z), making them model independent tests. Our constraints for the second derivative of Newton's constant at the present day, assuming it is slowly evolving as suggested by Big Bang Nucleosynthesis constraints, using the WiggleZ data is G double-dot{sub eff}(t{sub 0}) = −1.19 ± 0.95·10{sup −20} h{sup 2} yr{sup −2}, where h is defined via H{sub 0} = 100 h km s{sup −1} Mpc{sup −1}, while using both the WiggleZ and the Sloan Digital Sky Survey Luminous Red Galaxy (SDSS LRG) data is G double-dot{sub eff}(t{sub 0}) = −3.6 ± 6.8·10{sup −21} h{sup 2} yr{sup −2}, both being consistent with General Relativity. Finally, our constraint for the rms mass fluctuation σ{sub 8} using the WiggleZ data is σ{sub 8} = 0.75 ± 0.08, while using both the WiggleZ and the SDSS LRG data σ{sub 8} = 0.77 ± 0.07, both in good agreement with the latest measurements from the Cosmic Microwave Background radiation.

  15. Constraining H{sub 0} in general dark energy models from Sunyaev-Zeldovich/X-ray technique and complementary probes

    SciTech Connect

    Holanda, R.F.L.; Lima, J.A.S.; Cunha, J.V.; Marassi, L. E-mail: jvcunha@ufpa.br E-mail: limajas@astro.iag.usp.br

    2012-02-01

    In accelerating dark energy models, the estimates of the Hubble constant, H{sub 0}, from Sunyaev-Zel'dovich effect (SZE) and X-ray surface brightness of galaxy clusters may depend on the matter content (Ω{sub M}), the curvature (Ω{sub K}) and the equation of state parameter (ω). In this article, by using a sample of 25 angular diameter distances of galaxy clusters described by the elliptical β model obtained through the SZE/X-ray technique, we constrain H{sub 0} in the framework of a general ΛCDM model (arbitrary curvature) and a flat XCDM model with a constant equation of state parameter ω = p{sub x}/ρ{sub x}. In order to avoid the use of priors in the cosmological parameters, we apply a joint analysis involving the baryon acoustic oscillations (BAO) and the CMB Shift Parameter signature. By taking into account the statistical and systematic errors of the SZE/X-ray technique we obtain for nonflat ΛCDM model H{sub 0} = 74{sup +5.0}{sub −4.0} km s{sup −1} Mpc{sup −1}(1σ) whereas for a flat universe with constant equation of state parameter we find H{sub 0} = 72{sup +5.5}{sub −4.0} km s{sup −1} Mpc{sup −1}(1σ). By assuming that galaxy clusters are described by a spherical β model these results change to H{sub 0} = 62{sup +8.0}{sub −7.0} and H{sub 0} = 59{sup +9.0}{sub −6.0} km s{sup −1} Mpc{sup −1}(1σ), respectively. The results from elliptical description are in good agreement with independent studies from the Hubble Space Telescope key project and recent estimates based on the Wilkinson Microwave Anisotropy Probe, thereby suggesting that the combination of these three independent phenomena provides an interesting method to constrain the Hubble constant. As an extra bonus, the adoption of the elliptical description is revealed to be a quite realistic assumption. Finally, by comparing these results with a recent determination for a flat ΛCDM model using only the SZE/X-ray technique and BAO, we see that the geometry has a very weak

  16. Constraining dark energy

    NASA Astrophysics Data System (ADS)

    Danielsson, Ulf H.

    2012-07-01

    In this paper we propose a mechanism that protects theories violating a holographic bound suggested in arXiv:1203.5476 from developing accelerated expansion. The mechanism builts on work on transplanckian physics, and a non-trivial choice of vacuum states. If correct, it lends further support for detectable signatures in the CMBR signalling new physics.

  17. Fitting the Fermi-LAT GeV excess: On the importance of including the propagation of electrons from dark matter

    NASA Astrophysics Data System (ADS)

    Lacroix, Thomas; BÅ`hm, Céline; Silk, Joseph

    2014-08-01

    An excess of gamma rays at GeV energies has been pointed out in the Fermi-LAT data. This signal comes from a narrow region centred around the Galactic center and has been interpreted as possible evidence for light dark matter particles annihilating either into a mixture of leptons-antileptons and bb ¯ or into bb ¯ only. Focusing on the prompt gamma-ray emission, previous works found that the best fit to the data corresponds to annihilations proceeding predominantly into bb ¯. However, here we show that omitting the photon emission originating from primary and secondary electrons produced in dark matter annihilations, and undergoing diffusion through the Galactic magnetic field, can actually lead to the wrong conclusion. Accounting for this emission, we find that not only are annihilations of ˜10 GeV particles into a purely leptonic final state allowed, but the democratic scenario actually provides a better fit to the spectrum of the excess than the pure bb ¯ channel. We conclude our work with a discussion on constraints on these leptophilic scenarios based on the AMS data and the morphology of the excess.

  18. Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. II. Dark and stellar mass concentrations for 13 nearby face-on galaxies

    SciTech Connect

    Seigar, Marc S.; Davis, Benjamin L.; Berrier, Joel; Kennefick, Daniel

    2014-11-01

    We investigate the use of spiral arm pitch angles as a probe of disk galaxy mass profiles. We confirm our previous result that spiral arm pitch angles (P) are well correlated with the rate of shear (S) in disk galaxy rotation curves. We use this correlation to argue that imaging data alone can provide a powerful probe of galactic mass distributions out to large look-back times. We then use a sample of 13 galaxies, with Spitzer 3.6 μm imaging data and observed Hα rotation curves, to demonstrate how an inferred shear rate coupled with a bulge-disk decomposition model and a Tully-Fisher-derived velocity normalization can be used to place constraints on a galaxy's baryon fraction and dark matter halo profile. Finally, we show that there appears to be a trend (albeit a weak correlation) between spiral arm pitch angle and halo concentration. We discuss implications for the suggested link between supermassive black hole (SMBH) mass and dark halo concentration, using pitch angle as a proxy for SMBH mass.

  19. Constraining Dark Matter Halo Profiles and Galaxy Formation Models Using Spiral Arm Morphology. II. Dark and Stellar Mass Concentrations for 13 Nearby Face-on Galaxies

    NASA Astrophysics Data System (ADS)

    Seigar, Marc S.; Davis, Benjamin L.; Berrier, Joel; Kennefick, Daniel

    2014-11-01

    We investigate the use of spiral arm pitch angles as a probe of disk galaxy mass profiles. We confirm our previous result that spiral arm pitch angles (P) are well correlated with the rate of shear (S) in disk galaxy rotation curves. We use this correlation to argue that imaging data alone can provide a powerful probe of galactic mass distributions out to large look-back times. We then use a sample of 13 galaxies, with Spitzer 3.6 μm imaging data and observed Hα rotation curves, to demonstrate how an inferred shear rate coupled with a bulge-disk decomposition model and a Tully-Fisher-derived velocity normalization can be used to place constraints on a galaxy's baryon fraction and dark matter halo profile. Finally, we show that there appears to be a trend (albeit a weak correlation) between spiral arm pitch angle and halo concentration. We discuss implications for the suggested link between supermassive black hole (SMBH) mass and dark halo concentration, using pitch angle as a proxy for SMBH mass.

  20. Indirect dark matter detection limits from the ultrafaint Milky Way satellite Segue 1

    SciTech Connect

    Essig, Rouven; Sehgal, Neelima; Strigari, Louis E.; Geha, Marla; Simon, Joshua D.

    2010-12-15

    We use new kinematic data from the ultrafaint Milky Way satellite Segue 1 to model its dark matter distribution and derive upper limits on the dark matter annihilation cross section. Using gamma-ray flux upper limits from the Fermi satellite and MAGIC, we determine cross section exclusion regions for dark matter annihilation into a variety of different particles including charged leptons. We show that these exclusion regions are beginning to probe the regions of interest for a dark matter interpretation of the electron and positron fluxes from PAMELA, Fermi, and HESS, and that future observations of Segue 1 have strong prospects for testing such an interpretation. We additionally discuss prospects for detecting annihilation with neutrinos using the IceCube detector, finding that in an optimistic scenario a few neutrino events may be detected. Finally, we use the kinematic data to model the Segue 1 dark matter velocity dispersion and constrain Sommerfeld enhanced models.

  1. Indirect Dark Matter Detection Limits from the Ultra-Faint Milky Way Satellite Segue 1

    SciTech Connect

    Essig, Rouven; Sehgal, Neelima; Strigari, Louis E.; Geha, Marla; Simon, Joshua D.; /Carnegie Inst. Observ.

    2011-08-11

    We use new kinematic data from the ultra-faint Milky Way satellite Segue 1 to model its dark matter distribution and derive upper limits on the dark matter annihilation cross-section. Using gamma-ray ux upper limits from the Fermi satellite and MAGIC, we determine cross-section exclusion regions for dark matter annihilation into a variety of different particles including charged leptons. We show that these exclusion regions are beginning to probe the regions of interest for a dark matter interpretation of the electron and positron uxes from PAMELA, Fermi, and HESS, and that future observations of Segue 1 have strong prospects for testing such an interpretation. We additionally discuss prospects for detecting annihilation with neutrinos using the IceCube detector, finding that in an optimistic scenario a few neutrino events may be detected. Finally we use the kinematic data to model the Segue 1 dark matter velocity dispersion and constrain Sommerfeld enhanced models.

  2. Wino dark matter under siege

    SciTech Connect

    Cohen, Timothy; Lisanti, Mariangela; Pierce, Aaron; Slatyer, Tracy R. E-mail: mlisanti@princeton.edu E-mail: tslatyer@mit.edu

    2013-10-01

    A fermion triplet of SU(2){sub L} — a wino — is a well-motivated dark matter candidate. This work shows that present-day wino annihilations are constrained by indirect detection experiments, with the strongest limits coming from H.E.S.S. and Fermi. The bounds on wino dark matter are presented as a function of mass for two scenarios: thermal (winos constitute a subdominant component of the dark matter for masses less than 3.1 TeV) and non-thermal (winos comprise all the dark matter). Assuming the NFW halo model, the H.E.S.S. search for gamma-ray lines excludes the 3.1 TeV thermal wino; the combined H.E.S.S. and Fermi results completely exclude the non-thermal scenario. Uncertainties in the exclusions are explored. Indirect detection may provide the only probe for models of anomaly plus gravity mediation where the wino is the lightest superpartner and scalars reside at the 100 TeV scale.

  3. Model-Independent Studies of Dark Matter

    NASA Astrophysics Data System (ADS)

    Chen, Chuan-Ren

    The excess in cosmic-ray positrons and electrons observed by PAMELA, ATIC, PPB-BET and Fermi can be explained by dark matter decay or annihilation. On the other hand, the negative results from CDMS II and XENON direct detections of dark matter put an upper limit on the elastic-scattering cross section between dark matter and nucleon. We adopted model-independent approaches to study dark matter in cosmic-ray electrons, gamma-ray, relic density, direct detection experiments and LHC. We studied the distribution of the cosmic-ray electron flux observed at the Earth and found that it can reflect the initial energy spectrum of electrons generated from dark matter decay or annihilation even after propagation. We also derive constraints on the decay rate of dark matter into various two-body final states using Fermi and HESS gamma-ray data. We found that the μ+μ- or τ+τ- final state is favored in order to simultaneously explain electron excess and meet all gamma-ray constraints. Finally, we examined various tree-level induced operators of dimension six and constrain them using the current experimental data, including the WMAP data of the relic abundance and CDMS II direct detection of the spin-independent scattering. The implication of LHC search is also explored.

  4. Constraining the Warm Dark Matter Particle Mass through Ultra-deep UV Luminosity Functions at z=2

    NASA Astrophysics Data System (ADS)

    Menci, N.; Sanchez, N. G.; Castellano, M.; Grazian, A.

    2016-02-01

    We compute the mass function of galactic dark matter halos for different values of the warm dark matter (WDM) particle mass mX and compare it with the number density of ultra-faint galaxies derived from the deepest UV luminosity function available so far at redshift z ≈ 2. The magnitude limit MUV = -13 reached by such observations allows us to probe the WDM mass functions down to scales close to or smaller than the half-mass mode mass scale ˜109 M⊙. This allowed for an efficient discrimination among predictions for different mX which turn out to be in practice independent of the star formation efficiency η adopted to associate the observed UV luminosities of galaxies to the corresponding dark matter halo masses. Adopting a conservative approach to take into account the existing theoretical uncertainties in the galaxy halo mass function, we obtain a robust limit mX ≥ 1.8 keV for the mass of thermal relic WDM particles when comparing with the measured abundance of the faintest galaxies, while mX ≥ 1.5 keV is obtained when we compare with the Schechter fit to the observed luminosity function. The corresponding lower limit for sterile neutrinos depends on the modeling of the production mechanism; for instance msterile ≳ 4 keV holds for the Shi-Fuller mechanism. We discuss the impact of observational uncertainties on the above bound on mX. In the cold dark matter (CDM) limit {m}X\\gg 1 {{keV}} we recover the generic CDM result that very inefficient star formation efficiency is required to match the observed galaxy abundances. As a baseline for comparison with forthcoming observational results from the Hubble Space Telescope Frontier Field project, we provide predictions for the number density of faint galaxies with MUV = -13 for different values of the WDM particle mass and of the star formation efficiency η, which are valid up to z ≈ 4.

  5. The 4850 cm^{-1} Spectral Region of CO_2: Constrained Multispectrum Nonlinear Least Squares Fitting Including Line Mixing, Speed Dependent Line Profiles and Fermi Resonance

    NASA Astrophysics Data System (ADS)

    Benner, D. Chris; Devi, V. Malathy; Nugent, Emily; Brown, Linda R.; Miller, Charles E.; Toth, Robert A.; Sung, Keeyoon

    2009-06-01

    Room temperature spectra of carbon dioxide were obtained with the Fourier transform spectrometers at the National Solar Observatory's McMath-Pierce telescope and at the Jet Propulsion Laboratory. The multispectrum nonlinear least squares fitting technique is being used to derive accurate spectral line parameters for the strongest CO_2 bands in the 4700-4930 cm^{-1} spectral region. Positions of the spectral lines were constrained to their quantum mechanical relationships, and the rovibrational constants were derived directly from the fit. Similarly, the intensities of the lines within each of the rovibrational bands were constrained to their quantum mechanical relationships, and the band strength and Herman-Wallis coefficients were derived directly from the fit. These constraints even include a pair of interacting bands with the interaction coefficient derived directly using both the positions and intensities of the spectral lines. Room temperature self and air Lorentz halfwidth and pressure induced line shift coefficients are measured for most lines. Constraints upon the positions improve measurement of pressure-induced shifts, and constraints on the intensities improve the measurement of the Lorentz halfwidths. Line mixing and speed dependent line shapes are also required and characterized. D. Chris Benner, C.P. Rinsland, V. Malathy Devi, M.A.H. Smith, and D. Atkins, J. Quant. Spectrosc. Radiat. Transfer 53, 705-721 (1995)

  6. Searches for New Physics, involving Top Quarks, Dark Matter and the Higgs Bosons, at the ATLAS, CDF and Fermi-LAT Particle Experiments, and a description of a new limit re-interpretation tool, Basis-Limits

    NASA Astrophysics Data System (ADS)

    Rao, Kanury Kanishka

    Searches for new physics are presented in the lepton + jets channel at the CDF and ATLAS experiments. At CDF, we search for exotic quarks that couple to dark matter, new particle resonances in top-quark pairs, a Z' boson decaying quarks, and a two-Higgs doublet model. At ATLAS, we search for fourth generation down-type quarks, new particle resonances in top-quark pairs, and a multi-Higgs boson cascade. A novel methodology, Basis-limits, which allows for re-interpretation of experimental limits is presented. Basis-limits is used to extend ATLAS limits on fourth generation quarks to set limits on a new vector-like quark for all its decay modes. Finally, a spatial analysis of the gamma-ray excess, seen by the Fermi-LAT experiment, is performed. We find the location of the excess to be consistent with a dark matter halo at the Galactic center as the source.

  7. Constraining the Cosmic Ray Electron Distribution and the Halo Dark Matter from the High Energy Gamma-Ray Background

    NASA Astrophysics Data System (ADS)

    Chary, R.; Wright, E. L.

    2000-10-01

    We present an independent estimate of the high latitude (|b|>20 deg) contribution to the E>30 MeV gamma-ray background from Galactic nucleon-nucleon, electron bremsstrahlung and inverse Compton processes. In particular, the inverse Compton contribution has been estimated for different cosmic ray electron distributions and after factoring in the anisotropy in the interstellar radiation field and the anisotropic Klein-Nishina scattering cross section. We find that the emission from the inverse Compton process when the anisotropy in the radiation field is included can be higher by up to 50% when compared to estimates that adopt an isotropic radiation field. Simulated inverse Compton maps with a cosmic ray electron distribution represented by a ``pill box'' extending up to a distance of 5 kpc above the Galactic plane provide better fits to the EGRET intensity maps suggesting that the cosmic ray halo may be larger than previously thought. Fitting for the Galactic components of gamma-ray emission confirms the existence of an isotropic component with an intensity that can be represented by the form 27.7*(E/MeV)-2.16 ph m-2 s-1 sr-1 MeV-1, in excellent agreement with previous estimates. The spectrum of the isotropic component further argues strongly in favor of unresolved gamma-ray blazars being the source of this emission. Introduction of an anisotropic component improves the quality of the fits. However, this component, which could potentially arise from the dark matter in the Galactic halo, is not well characterized by a single power law which might be associated with any single dark matter candidate. It has an intensity of about a third of the isotropic background above E > 100 MeV at the level of 3*10-2 ph m-2 s-1 sr-1. The best fit power law spectrum to this component has a photon index of -1.7. Based on the intensity and spectrum of the anisotropic component we derive upper limits of 109Msun for the mass of cold, baryonic gas within the solar circle and a primordial

  8. Two-portal dark matter

    NASA Astrophysics Data System (ADS)

    Ghorbani, Karim; Ghorbani, Hossein

    2015-06-01

    We propose a renormalizable dark matter model in which a fermionic dark matter (DM) candidate communicates with the standard model particles through two distinct portals: Higgs and vector portals. The dark sector is charged under a U (1 )' gauge symmetry while the standard model has a leptophobic interaction with the dark vector boson. The leading contribution of the DM-nucleon elastic scattering cross section begins at one-loop level. The model meets all the constraints imposed by direct detection experiments provided by LUX and XENON100, observed relic abundance according to WMAP and Planck, and the invisible Higgs decay width measured at the LHC. It turns out that the dark matter mass in the viable parameter space can take values from a few GeV up to 1 TeV. This is a new feature which is absent in the models with only one portal. In addition, we can find in the constrained regions of the parameter space a DM mass of ˜34 GeV annihilating into b quark pair, which explains the Fermi-LAT gamma-ray excess.

  9. New Results from Fermi-LAT and Their Implications for the Nature of Dark Matter and the Origin of Cosmic Rays

    NASA Technical Reports Server (NTRS)

    Moiseev, Alexander

    2009-01-01

    The measured spectrum is compatible with a power law within our current systematic errors. The spectral index (-3.04) is harder than expected from previous experiments and simple theoretical considerations. "Pre-Fermi" diffusive model requires a harder electron injection spectrum (by 0.12) to fit the Fermi data, but inconsistent with positron excess reported by Pamela if it extends to higher energy. Additional component of electron flux from local source(s) may solve the problem; its origin, astrophysical or exotic, is still unclear. Valuable contribution to the calculation of IC component of diffuse gamma radiation.

  10. Search for 100 MeV to 10 GeV γ-ray lines in the Fermi-LAT data and implications for gravitino dark matter in the μνSSM

    NASA Astrophysics Data System (ADS)

    Albert, Andrea; Gómez-Vargas, Germán A.; Grefe, Michael; Muñoz, Carlos; Weniger, Christoph; Bloom, Elliott D.; Charles, Eric; Mazziotta, Mario N.; Morselli, Aldo

    2014-10-01

    Dark matter decay or annihilation may produce monochromatic signals in the γ-ray energy range. In this work we argue that there are strong theoretical motivations for studying these signals in the framework of gravitino dark matter decay and we perform a search for γ-ray spectral lines from 100 MeV to 10 GeV with Fermi-LAT data. In contrast to previous line searches at higher energies, the sensitivity of the present search is dominated by systematic uncertainties across most of the energy range considered. We estimate the size of systematic effects by analysing the flux from a number of control regions, and include the systematic uncertainties consistently in our fitting procedure. We have not observed any significant signals and present model-independent limits on γ-ray line emission from decaying and annihilating dark matter. We apply the former limits to the case of the gravitino, a well-known dark matter candidate in supersymmetric scenarios. In particular, the R-parity violating ''μ from ν'' Supersymmetric Standard Model μνSSM) is an attractive scenario in which including right-handed neutrinos solves the μ problem of the Minimal Supersymmetric Standard Model while simultaneously explaining the origin of neutrino masses. At the same time, the violation of R-parity renders the gravitino unstable and subject to decay into a photon and a neutrino. As a consequence of the limits on line emission, μνSSM gravitinos with masses larger than about 5 GeV, or lifetimes smaller than about 1028 s, are excluded at 95% confidence level as dark matter candidates.

  11. Search for 100 MeV to 10 GeV γ-ray lines in the Fermi-LAT data and implications for gravitino dark matter in the μνSSM

    SciTech Connect

    Albert, Andrea; Bloom, Elliott D.; Charles, Eric; Gómez-Vargas, Germán A.; Grefe, Michael; Muñoz, Carlos; Mazziotta, Mario N.; Morselli, Aldo E-mail: ggomezv@uc.cl E-mail: carlos.munnoz@uam.es E-mail: elliott@slac.stanford.edu E-mail: marionicola.mazziotta@ba.infn.it

    2014-10-01

    Dark matter decay or annihilation may produce monochromatic signals in the γ-ray energy range. In this work we argue that there are strong theoretical motivations for studying these signals in the framework of gravitino dark matter decay and we perform a search for γ-ray spectral lines from 100 MeV to 10 GeV with Fermi-LAT data. In contrast to previous line searches at higher energies, the sensitivity of the present search is dominated by systematic uncertainties across most of the energy range considered. We estimate the size of systematic effects by analysing the flux from a number of control regions, and include the systematic uncertainties consistently in our fitting procedure. We have not observed any significant signals and present model-independent limits on γ-ray line emission from decaying and annihilating dark matter. We apply the former limits to the case of the gravitino, a well-known dark matter candidate in supersymmetric scenarios. In particular, the R-parity violating ''μ from ν'' Supersymmetric Standard Model μνSSM) is an attractive scenario in which including right-handed neutrinos solves the μ problem of the Minimal Supersymmetric Standard Model while simultaneously explaining the origin of neutrino masses. At the same time, the violation of R-parity renders the gravitino unstable and subject to decay into a photon and a neutrino. As a consequence of the limits on line emission, μνSSM gravitinos with masses larger than about 5 GeV, or lifetimes smaller than about 10{sup 28} s, are excluded at 95% confidence level as dark matter candidates.

  12. Remembering Fermi

    SciTech Connect

    Cronin, James

    2005-03-30

    A combination of the discovery of nuclear fission and the circumstances of the 2nd World War brought Enrico Fermi to Chicago, where he led the team that produced the first controlled, self-sustained nuclear chain reaction. Following the war in 1945 Chancellor Hutchins, William Zachariasen, and Walter Bartky convinced Fermi to accept a professorship at the University of Chicago, where the Institute for Nuclear Studies was established. Fermi served as the leading figure in surely the greatest collection of scientists the world has ever seen. Fermi's tenure at Chicago was cut short by his death in 1954. My talk will concentrate on the years 1945-54. Examples of his research notebooks, his speeches, his teaching, and his correspondence will be discussed.

  13. Dark Matter and Collider Physics in Split-UED

    SciTech Connect

    Chan Park, Seong; Shu Jing

    2010-02-10

    Kaluza-Klein dark matter is an attractive weakly interacting massive particle in universal extra dimension model. In the recent extension 'split-UED', annihilation of Kaluza-Klein dark matter with a mass range 600-1000 GeV provides excellent fits to the recently observed excesses in cosmic electron and positron fluxes of Pamela, ATIC and Fermi-LAT experiments. The cosmic gamma-ray flux in the same process can be significant around 300 GeV, thus can be observed or constrained by the forthcoming Fermi-LAT diffuse gamma-ray data. The collider signal at the LHC is the resonance in the dijets channels and the large missing energy in the missing energy plus jets.

  14. Dissecting the gamma-ray background in search of dark matter

    SciTech Connect

    Cholis, Ilias; Hooper, Dan; McDermott, Samuel D. E-mail: dhooper@fnal.gov

    2014-02-01

    Several classes of astrophysical sources contribute to the approximately isotropic gamma-ray background measured by the Fermi Gamma-Ray Space Telescope. In this paper, we use Fermi's catalog of gamma-ray sources (along with corresponding source catalogs at infrared and radio wavelengths) to build and constrain a model for the contributions to the extragalactic gamma-ray background from astrophysical sources, including radio galaxies, star-forming galaxies, and blazars. We then combine our model with Fermi's measurement of the gamma-ray background to derive constraints on the dark matter annihilation cross section, including contributions from both extragalactic and galactic halos and subhalos. The resulting constraints are competitive with the strongest current constraints from the Galactic Center and dwarf spheroidal galaxies. As Fermi continues to measure the gamma-ray emission from a greater number of astrophysical sources, it will become possible to more tightly constrain the astrophysical contributions to the extragalactic gamma-ray background. We project that with 10 years of data, Fermi's measurement of this background combined with the improved constraints on the astrophysical source contributions will yield a sensitivity to dark matter annihilations that exceeds the strongest current constraints by a factor of ∼ 5–10.

  15. Dissecting the Gamma-Ray Background in Search of Dark Matter

    SciTech Connect

    Cholis, Ilias; Hooper, Dan; McDermott, Samuel D.

    2014-02-01

    Several classes of astrophysical sources contribute to the approximately isotropic gamma-ray background measured by the Fermi Gamma-Ray Space Telescope. In this paper, we use Fermi's catalog of gamma-ray sources (along with corresponding source catalogs at infrared and radio wavelengths) to build and constrain a model for the contributions to the extragalactic gamma-ray background from astrophysical sources, including radio galaxies, star-forming galaxies, and blazars. We then combine our model with Fermi's measurement of the gamma-ray background to derive constraints on the dark matter annihilation cross section, including contributions from both extragalactic and galactic halos and subhalos. The resulting constraints are competitive with the strongest current constraints from the Galactic Center and dwarf spheroidal galaxies. As Fermi continues to measure the gamma-ray emission from a greater number of astrophysical sources, it will become possible to more tightly constrain the astrophysical contributions to the extragalactic gamma-ray background. We project that with 10 years of data, Fermi's measurement of this background combined with the improved constraints on the astrophysical source contributions will yield a sensitivity to dark matter annihilations that exceeds the strongest current constraints by a factor of ~ 5 - 10.

  16. CONSTRAINING THE DISTRIBUTION OF DARK MATTER IN THE INNER GALAXY WITH AN INDIRECT DETECTION SIGNAL: THE CASE OF A TENTATIVE 130 GeV {gamma}-RAY LINE

    SciTech Connect

    Yang Ruizhi; Feng Lei; Li Xiang; Fan Yizhong

    2013-06-20

    Dark matter distribution in the very inner region of our Galaxy is still debated. In N-body simulations, a cuspy dark matter halo density profile is favored. Several dissipative baryonic processes, however, are found to be able to significantly flatten dark matter distribution, and a cored dark matter halo density profile is possible. Baryons dominate the gravitational potential in the inner Galaxy, hence a direct constraint on the abundance of dark matter particles is rather challenging. Recently, a few groups have identified a tentative 130 GeV line signal in the Galactic center, which could be interpreted as the signal of dark matter annihilation. Using current 130 GeV line data and adopting the generalized Navarro-Frenk-White profile of the dark matter halo-local dark matter density {rho}{sub 0} = 0.4 GeV cm{sup -3} and r{sub s} = 20 kpc-we obtain a 95% confidence level lower (upper) limit on the inner slope of dark matter density distribution, {alpha} = 1.06 (the cross section of dark matter annihilation into {gamma}-rays ({sigma}v){sub {chi}{chi}{sub {yields}{sub {gamma}{gamma}}}} = 1.3 Multiplication-Sign 10{sup -27} cm{sup 3} s{sup -1}). Such a slope is consistent with the results of some N-body simulations and, if the signal is due to dark matter, suggests that baryonic processes may be unimportant.

  17. Astrophysical Probes of Dark Matter Interactions

    NASA Astrophysics Data System (ADS)

    Reece, Matthew

    The majority of matter in the universe is dark matter, made up of some particle beyond those in the Standard Model of particle physics. So far we have very little information about what dark matter is and how it interacts, except through gravity. Constraints from halo shapes and the Bullet Cluster give upper bounds on the self-interaction strength of dark matter, but these bounds are very weak: roughly the same size as nuclear physics cross sections, which are very large by the standards of particle physics. Given how little we know about dark matter, it is important to search for it in as broad a context as possible. Existing direct and indirect detection analyses are typically motivated by simple particle physics models like WIMP dark matter. This research will aim to widen the scope of searches for dark matter by considering a more complete range of particle physics models, working out their implications for astrophysical data, and interpreting existing data in terms of these new models. New models of dark matter can affect searches in a variety of ways. Signals may show up in conventional indirect detection searches, e.g. in gamma rays detected by Fermi-LAT or in antiprotons detected by AMS-02. The new particle physics content of the models could be reflected in surprising spectral shapes or other features of such signals, or in gamma rays with a different profile on the sky than expected in typical models. The PI has worked, for example, on a model in which signals may arise from a dark disk, which is just one of many possibilities. Signals of new dark matter models might also arise in more subtle ways. Structure in the dark sector could influence the development of structure in the visible sector, indirectly. For instance, a dark matter disk or other dark structures could alter the orbits of stars in the galaxy and may be detectable through detailed studies of the kinematics of stellar populations. Dark accretion disks could exist around astrophysical objects

  18. Searching for Dwarf Spheroidal Galaxies with DES and the Fermi-LAT

    NASA Astrophysics Data System (ADS)

    Drlica-Wagner, Alex; DES Collaboration, Fermi-LAT Collaboration

    2016-01-01

    The population of Milky Way satellite galaxies includes the least luminous, least chemically evolved, and most dark matter dominated galaxies in the known universe. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are promising targets for the indirect detection of dark matter via gamma rays. Prior to 2015, roughly two dozen dwarf spheroidal galaxies were known to surround the Milky Way. From combined observations of these objects, the dark matter annihilation cross section has been constrained to be less than the generic thermal relic cross section for dark matter particles with mass < 100 GeV. Since the beginning of 2015, new optical imaging surveys have discovered over twenty new dwarf galaxy candidates, potentially doubling the population of Milky Way satellite galaxies in a single year. I will discuss recent optical searches for dwarf galaxies, focusing specifically on results from the Dark Energy Survey (DES) and the implications for gamma-ray searches for dark matter annihilation with the Fermi Large Area Telescope.

  19. Fermi questions

    NASA Astrophysics Data System (ADS)

    Bouffard, Karen

    1999-05-01

    This column contains problems and solutions for the general category of questions known as "Fermi" questions. Forcing the students to use their ability to estimate, giving answers in terms of order-of-magnitude, is not only a challenge for a competition, but a teaching strategy to use in the classroom to develop self-confidence and the ability to analyze answers as to whether or not they make sense, as opposed to relying on the "precision" of a calculator value.

  20. Dark compact planets

    NASA Astrophysics Data System (ADS)

    Tolos, Laura; Schaffner-Bielich, Jürgen

    2015-12-01

    We investigate compact objects formed by dark matter admixed with ordinary matter made of neutron-star matter and white-dwarf material. We consider non-self annihilating dark matter with an equation of state given by an interacting Fermi gas. We find new stable solutions, dark compact planets, with Earth-like masses and radii from a few Km to few hundred Km for weakly interacting dark matter which are stabilized by the mutual presence of dark matter and compact star matter. For the strongly interacting dark matter case, we obtain dark compact planets with Jupiter-like masses and radii of few hundred Km. These objects could be detected by observing exoplanets with unusually small radii. Moreover, we find that the recently observed 2 M⊙ pulsars set limits on the amount of dark matter inside neutron stars which is, at most, 1 0-6 M⊙ .

  1. Enrico Fermi

    NASA Astrophysics Data System (ADS)

    Yang, Chen Ning

    2013-05-01

    Enrico Fermi was, of all the great physicists of the 20th century, among the most respected and admired. He was respected and admired because of his contributions to both theoretical and experimental physics, because of his leadership in discovering for mankind a powerful new source of energy, and above all, because of his personal character. He was always reliable and trustworthy. He had both of his feet on the ground all the time. He had great strength, but never threw his weight around. He did not play to the gallery. He did not practise one-up-manship. He exemplified, I always believe, the perfect Confucian gentleman...

  2. Light dark matter and dark radiation

    NASA Astrophysics Data System (ADS)

    Heo, Jae Ho; Kim, C. S.

    2016-03-01

    Light ( M ≤ 20 MeV) dark-matter particles freeze out after neutrino decoupling. If the dark-matter particle couples to a neutrino or an electromagnetic plasma, the late time entropy production from dark-matter annihilation can change the neutrino-to-photon temperature ratio, and equally the effective number of neutrinos N eff. We study the non-equilibrium effects of dark-matter annihilation on the N eff and the effects by using a thermal equilibrium approximation. Both results are constrained with Planck observations. We demonstrate that the lower bounds of the dark-matter mass and the possibilities of the existence of additional radiation particles are more strongly constrained for dark-matter annihilation process in non-equilibrium.

  3. Observations of MilkyWay Dwarf Spheroidal galaxies with the Fermi-LAT detector and

    SciTech Connect

    Abdo, A.A.; Ackermann, M.; Ajello, M.; Atwood, W.B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E.D.; Bonamente, E.; Borgland, A.W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T.H.; Buson, S.; Caliandro, G.A.; /Naval Research Lab, Wash., D.C. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /SLAC /UC, Santa Cruz /INFN, Pisa /DAPNIA, Saclay /INFN, Trieste /Trieste U. /INFN, Padua /Padua U. /INFN, Perugia /Perugia U. /Bari Polytechnic /INFN, Bari /Ecole Polytechnique /Washington U., Seattle /IASF, Milan /George Mason U. /NASA, Goddard

    2010-05-26

    We report on the observations of 14 dwarf spheroidal galaxies with the Fermi Gamma-Ray Space Telescope taken during the first 11 months of survey mode operations. The Fermi telescope, which is conducting an all-sky {gamma}-ray survey in the 20 MeV to >300 GeV energy range, provides a new opportunity to test particle dark matter models through the expected {gamma}-ray emission produced by pair annihilation of weakly interacting massive particles (WIMPs). Local Group dwarf spheroidal galaxies, the largest galactic substructures predicted by the cold dark matter scenario, are attractive targets for such indirect searches for dark matter because they are nearby and among the most extreme dark matter dominated environments. No significant {gamma}-ray emission was detected above 100 MeV from the candidate dwarf galaxies. We determine upper limits to the {gamma}-ray flux assuming both power-law spectra and representative spectra from WIMP annihilation. The resulting integral flux above 100 MeV is constrained to be at a level below around 10{sup -9} photons cm{sup -2}s{sup -1}. Using recent stellar kinematic data, the {gamma}-ray flux limits are combined with improved determinations of the dark matter density profile in 8 of the 14 candidate dwarfs to place limits on the pair annihilation cross-section ofWIMPs in several widely studied extensions of the standard model, including its supersymmetric extension and other models that received recent attention. With the present data, we are able to rule out large parts of the parameter space where the thermal relic density is below the observed cosmological dark matter density and WIMPs (neutralinos here) are dominantly produced non-thermally, e.g. in models where supersymmetry breaking occurs via anomaly mediation. The {gamma}-ray limits presented here also constrain some WIMP models proposed to explain the Fermi and PAMELA e{sup +}e{sup -} data, including low-mass wino-like neutralinos and models with TeV masses pair

  4. Lights in the dark

    NASA Astrophysics Data System (ADS)

    Ubaldi, Lorenzo

    The nature of dark matter is still obscure. The gamma-ray large area telescope on board the Fermi satellite is playing a major role in searching for a signal from dark matter annihilation or decay ("indirect detection"). In this dissertation I discuss theoretical work on how to use recent observations from Fermi to probe dark matter properties. First, I study how searches for monochromatic gamma rays can be exploited to put constraints on the so-called singlet scalar dark matter model. This is one of the most minimal particle setups to include a dark matter candidate, and is obtained by adding a singlet real scalar field to the Standard Model and imposing a discrete symmetry to make this new particle stable. Second, I explore a non-standard, novel way to search for dark matter: looking at dark matter-cosmic ray scatterings in Active Galactic Nuclei. These objects are believed to be embedded in extremely large densities of dark matter, and are known to be sources of very powerful jets containing electrons and protons. I show how the scattering of the electrons in the jets off of the dark matter can produce photons with a very distinct spectral feature and with a flux that Fermi could potentially measure in the near future. Last, I investigate whether a possible detection of multiple gamma-ray lines could point to a scenario where the dark sector is richer than what usually assumed and contains more than one stable dark matter particle. To probe such a scenario more valuable information is actually gained from direct detection experiments and collider searches, as I discuss in detail.

  5. Fermionic dark matter with pseudo-scalar Yukawa interaction

    NASA Astrophysics Data System (ADS)

    Ghorbani, Karim

    2015-01-01

    We consider a renormalizable extension of the standard model whose fermionic dark matter (DM) candidate interacts with a real singlet pseudo-scalar via a pseudo-scalar Yukawa term while we assume that the full Lagrangian is CP-conserved in the classical level. When the pseudo-scalar boson develops a non-zero vacuum expectation value, spontaneous CP-violation occurs and this provides a CP-violated interaction of the dark sector with the SM particles through mixing between the Higgs-like boson and the SM-like Higgs boson. This scenario suggests a minimal number of free parameters. Focusing mainly on the indirect detection observables, we calculate the dark matter annihilation cross section and then compute the DM relic density in the range up to mDM = 300 GeV.We then find viable regions in the parameter space constrained by the observed DM relic abundance as well as invisible Higgs decay width in the light of 125 GeV Higgs discovery at the LHC. We find that within the constrained region of the parameter space, there exists a model with dark matter mass mDM ~ 38 GeV annihilating predominantly into b quarks, which can explain the Fermi-LAT galactic gamma-ray excess.

  6. Fermionic dark matter with pseudo-scalar Yukawa interaction

    SciTech Connect

    Ghorbani, Karim

    2015-01-01

    We consider a renormalizable extension of the standard model whose fermionic dark matter (DM) candidate interacts with a real singlet pseudo-scalar via a pseudo-scalar Yukawa term while we assume that the full Lagrangian is CP-conserved in the classical level. When the pseudo-scalar boson develops a non-zero vacuum expectation value, spontaneous CP-violation occurs and this provides a CP-violated interaction of the dark sector with the SM particles through mixing between the Higgs-like boson and the SM-like Higgs boson. This scenario suggests a minimal number of free parameters. Focusing mainly on the indirect detection observables, we calculate the dark matter annihilation cross section and then compute the DM relic density in the range up to m{sub DM} = 300 GeV.We then find viable regions in the parameter space constrained by the observed DM relic abundance as well as invisible Higgs decay width in the light of 125 GeV Higgs discovery at the LHC. We find that within the constrained region of the parameter space, there exists a model with dark matter mass m{sub DM} ∼ 38 GeV annihilating predominantly into b quarks, which can explain the Fermi-LAT galactic gamma-ray excess.

  7. The radial velocity dispersion profile of the Galactic halo: constraining the density profile of the dark halo of the Milky Way

    NASA Astrophysics Data System (ADS)

    Battaglia, Giuseppina; Helmi, Amina; Morrison, Heather; Harding, Paul; Olszewski, Edward W.; Mateo, Mario; Freeman, Kenneth C.; Norris, John; Shectman, Stephen A.

    2005-12-01

    We have compiled a new sample of 240 halo objects with accurate distance and radial velocity measurements, including globular clusters, satellite galaxies, field blue horizontal branch (FHB) stars and red giant stars from the Spaghetti survey. The new data lead to a significant increase in the number of known objects for Galactocentric radii beyond 50 kpc, which allows a reliable determination of the radial velocity dispersion profile out to very large distances. The radial velocity dispersion shows an almost constant value of 120 km s-1 out to 30 kpc and then continuously declines down to 50 km s-1 at about 120 kpc. This fall-off puts important constraints on the density profile and total mass of the dark matter halo of the Milky Way. For a constant velocity anisotropy, the isothermal profile is ruled out, while both a dark halo following a truncated flat (TF) model of mass 1.2+1.8-0.5× 1012Msolar and a Navarro, Frenk & White (NFW) profile of mass 0.8+1.2-0.2× 1012Msolar and c= 18 are consistent with the data. The significant increase in the number of tracers combined with the large extent of the region probed by these has allowed a more precise determination of the Milky Way mass in comparison to previous works. We also show how different assumptions for the velocity anisotropy affect the performance of the mass models.

  8. MC 2: Constraining the Dark Matter Distribution of the Violent Merging Galaxy Cluster CIZA J2242.8+5301 by Piercing through the Milky Way

    NASA Astrophysics Data System (ADS)

    Jee, M. James; Stroe, Andra; Dawson, William; Wittman, David; Hoekstra, Henk; Brüggen, Marcus; Röttgering, Huub; Sobral, David; van Weeren, Reinout J.

    2015-03-01

    The galaxy cluster CIZA J2242.8+5301 at z = 0.19 is a merging system with a prominent (~2 Mpc long) radio relic, which together with the morphology of the X-ray emission provides strong evidence for a violent collision along the north-south axis. We present our constraints on the dark matter distribution of this unusual system using Subaru and Canada-France-Hawaii Telescope imaging data. Measuring a high signal-to-noise ratio lensing signal from this cluster is potentially a challenging task because of its proximity to the Milky Way plane (|b| ~ 5°). We overcome this challenge with careful observation planning and systematics control, which enables us to successfully map the dark matter distribution of the cluster with high fidelity. The resulting mass map shows that the mass distribution of CIZA J2242.8+5301 is highly elongated along the north-south merger axis inferred from the orientation of the radio relics. Based on our mass reconstruction, we identify two sub-clusters, which coincide with the cluster galaxy distributions. We determine their masses using Markov Chain Monte Carlo analysis by simultaneously fitting two Navarro-Frenk-White halos without fixing their centroids. The resulting masses of the northern and southern systems are M200=11.0-3.2+3.7× 1014 M⊙ and 9.8-2.5+3.8× 1014 M⊙ , respectively, indicating that we are witnessing a post-collision of two giant systems of nearly equal mass. When the mass and galaxy centroids are compared in detail, we detect ~1' (~190 kpc) offsets in both northern and southern sub-clusters. After investigating the statistical significance of the offsets by bootstrapping both mass and galaxy centroids, we find that the galaxy luminosity-mass offset for the northern clump is statistically significant at the >~ 2σ level whereas the detection is only marginal for the southern sub-cluster in part because of a relatively large mass centroid error. We conclude that it is yet premature to uniquely attribute the galaxy

  9. Direct and Indirect Dark Matter Detection in Gauge Theories

    SciTech Connect

    Queiroz, Farinaldo

    2013-01-01

    The Dark matter (DM) problem constitutes a key question at the interface among Particle Physics, Astrophysics and Cosmology. The observational data which have been accumulated in the last years point to an existence of non baryonic amount of DM. Since the Standard Model (SM) does not provide any candidate for such non-baryonic DM, the evidence of DM is a major indication for new physics beyond the SM. We will study in this work one of the most popular DM candidates, the so called WIMPs (Weakly Interacting Massive Particles) from a direct and indirect detection perspective. In order to approach the direct and indirect dection of DM in the context of Particle Physics in a more pedagogic way, we will begin our discussion talking about a minimal extension of the SM. Later we will work on the subject in a 3-3-1 model. Next, we will study the role of WIMPs in the Big Bang Nucleosynthesis. Lastly, we will look for indirect DM signals in the center of our galaxy using the NASA Satellite, called Fermi-LAT. Through a comprehensive analysis of the data events observed by Fermi-LAT and some background models, we will constrain the dark matter annihilation cross section for several annihilation channels and dark matter halo profiles.

  10. Prospects For Identifying Dark Matter With CoGeNT

    SciTech Connect

    Kelso, Chris; Hooper, Dan

    2010-11-01

    It has previously been shown that the excess of events reported by the CoGeNT collaboration could be generated by elastically scattering dark matter particles with a mass of approximately 5-15 GeV. This mass range is very similar to that required to generate the annual modulation observed by DAMA/LIBRA and the gamma rays from the region surrounding the Galactic Center identified within the data of the Fermi Gamma Ray Space Telescope. To confidently conclude that CoGeNT's excess is the result of dark matter, however, further data will likely be needed. In this paper, we make projections for the first full year of CoGeNT data, and for its planned upgrade. Not only will this body of data more accurately constrain the spectrum of nuclear recoil events, and corresponding dark matter parameter space, but will also make it possible to identify seasonal variations in the rate. In particular, if the CoGeNT excess is the product of dark matter, then one year of CoGeNT data will likely reveal an annual modulation with a significance of 2-3{sigma}. The planned CoGeNT upgrade will not only detect such an annual modulation with high significance, but will be capable of measuring the energy spectrum of the modulation amplitude. These measurements will be essential to irrefutably confirming a dark matter origin of these events.

  11. Fermi Pulsar Analysis

    NASA Video Gallery

    This animation illustrates how analysis of Fermi data reveals new pulsars. Fermi's LAT records the precise arrival time and approximate direction of the gamma rays it detects, but to identify a pul...

  12. Model-independent indirect detection constraints on hidden sector dark matter

    NASA Astrophysics Data System (ADS)

    Elor, Gilly; Rodd, Nicholas L.; Slatyer, Tracy R.; Xue, Wei

    2016-06-01

    If dark matter inhabits an expanded ``hidden sector'', annihilations may proceed through sequential decays or multi-body final states. We map out the potential signals and current constraints on such a framework in indirect searches, using a model-independent setup based on multi-step hierarchical cascade decays. While remaining agnostic to the details of the hidden sector model, our framework captures the generic broadening of the spectrum of secondary particles (photons, neutrinos, e+e‑ and bar p p) relative to the case of direct annihilation to Standard Model particles. We explore how indirect constraints on dark matter annihilation limit the parameter space for such cascade/multi-particle decays. We investigate limits from the cosmic microwave background by Planck, the Fermi measurement of photons from the dwarf galaxies, and positron data from AMS-02. The presence of a hidden sector can change the constraints on the dark matter by up to an order of magnitude in either direction (although the effect can be much smaller). We find that generally the bound from the Fermi dwarfs is most constraining for annihilations to photon-rich final states, while AMS-02 is most constraining for electron and muon final states; however in certain instances the CMB bounds overtake both, due to their approximate independence on the details of the hidden sector cascade. We provide the full set of cascade spectra considered here as publicly available code with examples at http://web.mit.edu/lns/research/CascadeSpectra.html.

  13. Unveiling Unidentified Fermi Sources

    NASA Astrophysics Data System (ADS)

    Zhang, Lizhong; South Pole Telescope

    2016-01-01

    The Fermi γ-ray Space Telescope (Fermi) has surveyed the entire sky at the highest-energy band of the electromagnetic spectrum. The majority of Fermi sources have counterpart identifications from multi-wavelength large-area surveys, particularly in the radio and x-ray bands. However, around 35% of Fermi sources remain unidentified, a problem exasperated by the low resolution of the telescope. Understanding the nature of unidentified Fermi sources is one of the most pressing problems in γ-ray astronomy. The South Pole Telescope (SPT) has completed a survey covering a 2500 square degrees of the southern extragalactic sky with arcminute resolution at millimeter wavelengths. The mm wavelength is the most efficient means to identify blazars and unidentified Fermi sources. Our analysis shows that the SPT point source catalog provides candidate associations for 40% of the unidentified Fermi sources, showing them to be flat-spectrum radio quasars which are extraordinarily bright at millimeter (mm) wavelengths.

  14. Neutrinos and dark matter

    SciTech Connect

    Ibarra, Alejandro

    2015-07-15

    Neutrinos could be key particles to unravel the nature of the dark matter of the Universe. On the one hand, sterile neutrinos in minimal extensions of the Standard Model are excellent dark matter candidates, producing potentially observable signals in the form of a line in the X-ray sky. On the other hand, the annihilation or the decay of dark matter particles produces, in many plausible dark matter scenarios, a neutrino flux that could be detected at neutrino telescopes, thus providing non-gravitational evidence for dark matter. More conservatively, the non-observation of a significant excess in the neutrino fluxes with respect to the expected astrophysical backgrounds can be used to constrain dark matter properties, such as the self-annihilation cross section, the scattering cross section with nucleons and the lifetime.

  15. Indirect detection of dark matter with γ rays.

    PubMed

    Funk, Stefan

    2015-10-01

    The details of what constitutes the majority of the mass that makes up dark matter in the Universe remains one of the prime puzzles of cosmology and particle physics today-80 y after the first observational indications. Today, it is widely accepted that dark matter exists and that it is very likely composed of elementary particles, which are weakly interacting and massive [weakly interacting massive particles (WIMPs)]. As important as dark matter is in our understanding of cosmology, the detection of these particles has thus far been elusive. Their primary properties such as mass and interaction cross sections are still unknown. Indirect detection searches for the products of WIMP annihilation or decay. This is generally done through observations of γ-ray photons or cosmic rays. Instruments such as the Fermi large-area telescope, high-energy stereoscopic system, major atmospheric gamma-ray imaging Cherenkov, and very energetic radiation imaging telescope array, combined with the future Cherenkov telescope array, will provide important complementarity to other search techniques. Given the expected sensitivities of all search techniques, we are at a stage where the WIMP scenario is facing stringent tests, and it can be expected that WIMPs will be either be detected or the scenario will be so severely constrained that it will have to be rethought. In this sense, we are on the threshold of discovery. In this article, I will give a general overview of the current status and future expectations for indirect searches of dark matter (WIMP) particles. PMID:24821791

  16. Indirect detection of dark matter with γ rays

    PubMed Central

    Funk, Stefan

    2015-01-01

    The details of what constitutes the majority of the mass that makes up dark matter in the Universe remains one of the prime puzzles of cosmology and particle physics today—80 y after the first observational indications. Today, it is widely accepted that dark matter exists and that it is very likely composed of elementary particles, which are weakly interacting and massive [weakly interacting massive particles (WIMPs)]. As important as dark matter is in our understanding of cosmology, the detection of these particles has thus far been elusive. Their primary properties such as mass and interaction cross sections are still unknown. Indirect detection searches for the products of WIMP annihilation or decay. This is generally done through observations of γ-ray photons or cosmic rays. Instruments such as the Fermi large-area telescope, high-energy stereoscopic system, major atmospheric gamma-ray imaging Cherenkov, and very energetic radiation imaging telescope array, combined with the future Cherenkov telescope array, will provide important complementarity to other search techniques. Given the expected sensitivities of all search techniques, we are at a stage where the WIMP scenario is facing stringent tests, and it can be expected that WIMPs will be either be detected or the scenario will be so severely constrained that it will have to be rethought. In this sense, we are on the threshold of discovery. In this article, I will give a general overview of the current status and future expectations for indirect searches of dark matter (WIMP) particles. PMID:24821791

  17. Xenophobic dark matter

    NASA Astrophysics Data System (ADS)

    Feng, Jonathan L.; Kumar, Jason; Sanford, David

    2013-07-01

    We consider models of xenophobic dark matter, in which isospin-violating dark matter-nucleon interactions significantly degrade the response of xenon direct detection experiments. For models of near-maximal xenophobia, with neutron-to-proton coupling ratio fn/fp≈-0.64, and dark matter mass near 8 GeV, the regions of interest for CoGeNT and CDMS-Si and the region of interest identified by Collar and Fields in CDMS-Ge data can be brought into agreement. This model may be tested in future direct, indirect, and collider searches. Interestingly, because the natural isotope abundance of xenon implies that xenophobia has its limits, we find that this xenophobic model may be probed in the near future by xenon experiments. Near-future data from the LHC and Fermi-LAT may also provide interesting alternative probes of xenophobic dark matter.

  18. Composite millicharged dark matter

    NASA Astrophysics Data System (ADS)

    Kouvaris, Chris

    2013-07-01

    We study a composite millicharged dark matter model. The dark matter is in the form of pionlike objects emerging from a higher scale QCD-like theory. We present two distinct possibilities with interesting phenomenological consequences based on the choice of the parameters. In the first one, the dark matter is produced nonthermally, and it could potentially account for the 130 GeV Fermi photon line via decays of the “dark pions.” We estimate the self-interaction cross section, which might play an important role both in changing the dark matter halo profile at the center of the galaxy and in making the dark matter warmer. In the second version the dark matter is produced via the freeze-in mechanism. Finally we impose all possible astrophysical, cosmological and experimental constraints. We study in detail generic constraints on millicharged dark matter that can arise from anomalous isotope searches of different elements and we show why constraints based on direct searches from underground detectors are not generally valid.

  19. Dark matter constraints from box-shaped gamma-ray features

    SciTech Connect

    Ibarra, Alejandro; Gehler, Sergio López; Pato, Miguel E-mail: sergio.lopez@ph.tum.de

    2012-07-01

    The observation of a sharp spectral feature in the gamma-ray sky would be one of the cleanest ways to identify dark matter and pinpoint its properties. Over the years a lot of attention has been paid to two specific features, namely gamma-ray lines and internal bremsstrahlung. Here, we explore a third class of spectral signatures, box-shaped gamma-ray spectra, that naturally arise in dark matter cascade annihilations or decays into intermediate particles that in turn decay into photons. Using Fermi-LAT data, we derive constraints on the dark matter parameter space for both annihilating and decaying dark matter, and show explicitly that our limits are competitive to strategies employing standard spectral features. More importantly, we find robust limits even in the case of non-degenerate dark matter and intermediate particle masses. This result is particularly relevant in constraining dark matter frameworks with gamma-ray data. We conclude by illustrating the power of box-shaped gamma-ray constraints on concrete particle physics scenarios.

  20. The status of neutralino dark matter

    SciTech Connect

    Shakya, Bibhushan

    2014-06-24

    The lightest neutralino in supersymmetry is the most studied dark matter candidate. This writeup reviews the status of neutralino dark matter in minimal and nonminimal supersymmetric models in light of recent null results at the XENON100 experiment and the observation of a 130 GeV gamma ray signal from the Galactic Center by the Fermi LAT.

  1. Black Hole Window into p-Wave Dark Matter Annihilation.

    PubMed

    Shelton, Jessie; Shapiro, Stuart L; Fields, Brian D

    2015-12-01

    We present a new method to measure or constrain p-wave-suppressed cross sections for dark matter (DM) annihilations inside the steep density spikes induced by supermassive black holes. We demonstrate that the high DM densities, together with the increased velocity dispersion, within such spikes combine to make thermal p-wave annihilation cross sections potentially visible in γ-ray observations of the Galactic center (GC). The resulting DM signal is a bright central point source with emission originating from DM annihilations in the absence of a detectable spatially extended signal from the halo. We define two simple reference theories of DM with a thermal p-wave annihilation cross section and establish new limits on the combined particle and astrophysical parameter space of these models, demonstrating that Fermi Large Area Telescope is currently sensitive to thermal p-wave DM over a wide range of possible scenarios for the DM distribution in the GC. PMID:26684108

  2. Black Hole Window into p -Wave Dark Matter Annihilation

    NASA Astrophysics Data System (ADS)

    Shelton, Jessie; Shapiro, Stuart L.; Fields, Brian D.

    2015-12-01

    We present a new method to measure or constrain p -wave-suppressed cross sections for dark matter (DM) annihilations inside the steep density spikes induced by supermassive black holes. We demonstrate that the high DM densities, together with the increased velocity dispersion, within such spikes combine to make thermal p -wave annihilation cross sections potentially visible in γ -ray observations of the Galactic center (GC). The resulting DM signal is a bright central point source with emission originating from DM annihilations in the absence of a detectable spatially extended signal from the halo. We define two simple reference theories of DM with a thermal p -wave annihilation cross section and establish new limits on the combined particle and astrophysical parameter space of these models, demonstrating that Fermi Large Area Telescope is currently sensitive to thermal p -wave DM over a wide range of possible scenarios for the DM distribution in the GC.

  3. The Hamiltonian structure of Dirac's equation in tensor form and its Fermi quantization

    NASA Technical Reports Server (NTRS)

    Reifler, Frank; Morris, Randall

    1992-01-01

    Currently, there is some interest in studying the tensor forms of the Dirac equation to elucidate the possibility of the constrained tensor fields admitting Fermi quantization. We demonstrate that the bispinor and tensor Hamiltonian systems have equivalent Fermi quantizations. Although the tensor Hamiltonian system is noncanonical, representing the tensor Poisson brackets as commutators for the Heisenberg operators directly leads to Fermi quantization without the use of bispinors.

  4. Interacting warm dark matter

    SciTech Connect

    Cruz, Norman; Palma, Guillermo; Zambrano, David; Avelino, Arturo E-mail: guillermo.palma@usach.cl E-mail: avelino@fisica.ugto.mx

    2013-05-01

    We explore a cosmological model composed by a dark matter fluid interacting with a dark energy fluid. The interaction term has the non-linear λρ{sub m}{sup α}ρ{sub e}{sup β} form, where ρ{sub m} and ρ{sub e} are the energy densities of the dark matter and dark energy, respectively. The parameters α and β are in principle not constrained to take any particular values, and were estimated from observations. We perform an analytical study of the evolution equations, finding the fixed points and their stability properties in order to characterize suitable physical regions in the phase space of the dark matter and dark energy densities. The constants (λ,α,β) as well as w{sub m} and w{sub e} of the EoS of dark matter and dark energy respectively, were estimated using the cosmological observations of the type Ia supernovae and the Hubble expansion rate H(z) data sets. We find that the best estimated values for the free parameters of the model correspond to a warm dark matter interacting with a phantom dark energy component, with a well goodness-of-fit to data. However, using the Bayesian Information Criterion (BIC) we find that this model is overcame by a warm dark matter – phantom dark energy model without interaction, as well as by the ΛCDM model. We find also a large dispersion on the best estimated values of the (λ,α,β) parameters, so even if we are not able to set strong constraints on their values, given the goodness-of-fit to data of the model, we find that a large variety of theirs values are well compatible with the observational data used.

  5. Fermi at Six Months

    NASA Technical Reports Server (NTRS)

    Hays, Elizabeth

    2009-01-01

    An overview of the Fermi Gamma-ray Space Telescope's first 6 months in operation is provided. The Fermi Gamma-ray Space Telescope, formerly called GLAST, is a mission to measure the cosmic gamma-ray flux in the energy rage 20 MeV to more than 300 GeV, with supporting measurements for gamma-ray bursts from 8 keV to 30 MeV. It contains a Large Area Telescope capable of viewing the entire sky every 3 hours and a Gamma-ray Burst Monitor for viewing the entire unocculted sky. Since its launch on June 11, 2008 Fermi has provided information on pulsars, gamma ray bursts, relativistic jets, the active galactic nucleus, and a globular star cluster. This presentation describes Fermi's development, mission, instruments and recent findings.

  6. Fermi Galactic Center Zoom

    NASA Video Gallery

    This animation zooms into an image of the Milky Way, shown in visible light, and superimposes a gamma-ray map of the galactic center from NASA's Fermi. Raw data transitions to a view with all known...

  7. Fermi, Szilard and Trinity

    ERIC Educational Resources Information Center

    Anderson, Herbert L.

    1974-01-01

    The final installment of the author's recollections of his work with physicists Enrico Fermi, Leo Szilard and others in developing the first controlled nuclear chain reaction and in preparing the test explosion of the first atomic bomb. (GS)

  8. Inert doublet dark matter and mirror/extra families after Xenon100

    NASA Astrophysics Data System (ADS)

    Melfo, Alejandra; Nemevšek, Miha; Nesti, Fabrizio; Senjanović, Goran; Zhang, Yue

    2011-08-01

    It was shown recently that mirror fermions, naturally present in a number of directions for new physics, seem to require an inert scalar doublet in order to pass the electroweak precision tests. This provides a further motivation for considering the inert doublet as a dark matter candidate. Moreover, the presence of extra families enhances the standard model Higgs-nucleon coupling, which has crucial impact on the Higgs and dark matter searches. We study the limits on the inert dark matter mass in view of recent Xenon100 data. We find that the mass of the inert dark matter must lie in a very narrow window 75±1GeV while the Higgs boson must weigh more than 400 GeV. For the sake of completeness we discuss the cases with fewer extra families, where the possibility of a light Higgs boson opens up, enlarging the dark matter mass window to (1)/(2)mh-76GeV. We find that Xenon100 constrains the DM-Higgs interaction, which in turn implies a lower bound on the monochromatic gamma ray flux from DM annihilation in the galactic halo. For the mirror case, the predicted annihilation cross section lies a factor of 4-5 below the current limit set by Fermi LAT, thus providing a promising indirect detection signal.

  9. Limits on dark matter from AMS-02 antiproton and positron fraction data

    NASA Astrophysics Data System (ADS)

    Lu, Bo-Qiang; Zong, Hong-Shi

    2016-05-01

    Herein we derive limits on dark matter annihilation cross section and lifetime using measurements of the AMS-02 antiproton ratio and positron fraction data. In deriving the limits, we consider the scenario of secondary particles accelerated in supernova remnants (SNRs), which has been argued to be able to reasonably account for the AMS-02 high-energy positron/antiproton fraction/ratio data. We parametrize the contribution of secondary particles accelerated in SNRs and then fit the observational data within the conventional cosmic ray propagation model by adopting the galprop code. We use the likelihood ratio test to determine the 95% confidence level upper limits of possible dark matter (DM) contribution to the antiproton/positron fractions measured by AMS-02. Under the assumption taken in this work, we find that our limits are stronger than that set by the Fermi-LAT gamma ray Pass 8 data observation on the dwarf spheroidal satellite galaxies. We show that the solar modulation (cosmic ray propagation) parameters can play a non-negligible role in modifying the constraints on dark matter annihilation cross section and lifetime for mχ<100 GeV (mχ>100 GeV ), where mχ is the rest mass of dark matter particles. We also find that constrains on DM parameters from AMS-02 data would become more stringent when the solar modulation is weak. Using these results, we also put limits on the effective field theory of dark matter.

  10. On dark energy isocurvature perturbation

    SciTech Connect

    Liu, Jie; Zhang, Xinmin; Li, Mingzhe E-mail: limz@nju.edu.cn

    2011-06-01

    Determining the equation of state of dark energy with astronomical observations is crucially important to understand the nature of dark energy. In performing a likelihood analysis of the data, especially of the cosmic microwave background and large scale structure data the dark energy perturbations have to be taken into account both for theoretical consistency and for numerical accuracy. Usually, one assumes in the global fitting analysis that the dark energy perturbations are adiabatic. In this paper, we study the dark energy isocurvature perturbation analytically and discuss its implications for the cosmic microwave background radiation and large scale structure. Furthermore, with the current astronomical observational data and by employing Markov Chain Monte Carlo method, we perform a global analysis of cosmological parameters assuming general initial conditions for the dark energy perturbations. The results show that the dark energy isocurvature perturbations are very weakly constrained and that purely adiabatic initial conditions are consistent with the data.

  11. The search for dark matter

    NASA Astrophysics Data System (ADS)

    Cline, David B.

    2016-03-01

    We discuss the search for dark matter. We first review the data from LUX that excludes the low-mass WIMP region and slightly lowers the XENON100 limits. We provide a brief review of the problems with the claimed low-mass signals. We discuss the current expectations for SUSY-WIMP dark matter and show why very massive detectors like Darwin may be required. We discuss some theoretical predictions from the meeting. There was compelling evidence from events observed in the Galactic Center by Fermi-LAT of WIMP dark matter at the UCLA meeting. We recount the Richard Arnowitt Lectures at UCLA dark matter symposiums and his role in the development of the strategy to detect SUGRA dark matter. In Honor of Richard Arnowitt.

  12. AMS-02 positron excess: New bounds on dark matter models and hint for primary electron spectrum hardening

    NASA Astrophysics Data System (ADS)

    Feng, Lei; Yang, Rui-Zhi; He, Hao-Ning; Dong, Tie-Kuang; Fan, Yi-Zhong; Chang, Jin

    2014-01-01

    The data collected by ATIC, CREAM and PAMELA all display remarkable cosmic ray nuclei spectrum hardening above the magnetic rigidity ∼240 GV. One natural speculation is that the primary electron spectrum also gets hardened (possibly at ∼80 GV) and the hardening partly accounts for the electron/positron total spectrum excess discovered by ATIC, HESS and Fermi-LAT. If it is the case, the increasing behavior of the subsequent positron-to-electron ratio will get flattened and the spectrum hardening should be taken into account in the joint fit of the electron/positron data otherwise the inferred parameters will be biased. Our joint fits of the latest AMS-02 positron fraction data together with the PAMELA/Fermi-LAT electron/positron spectrum data suggest that the primary electron spectrum hardening is needed in most though not all modelings. The bounds on dark matter models have also been investigated. In the presence of spectrum hardening of primary electrons, the amount of dark-matter-originated electron/positron pairs needed in the modeling is smaller. Even with such a modification, the annihilation channel χχ→μ+μ- has been tightly constrained by the Fermi-LAT Galactic diffuse emission data. The decay channel χ→μ+μ- is found to be viable.

  13. Astrophysical constraints on dark energy

    NASA Astrophysics Data System (ADS)

    Ho, Chiu Man; Hsu, Stephen D. H.

    2016-02-01

    Dark energy (i.e., a cosmological constant) leads, in the Newtonian approximation, to a repulsive force which grows linearly with distance and which can have astrophysical consequences. For example, the dark energy force overcomes the gravitational attraction from an isolated object (e.g., dwarf galaxy) of mass 107M⊙ at a distance of 23 kpc. Observable velocities of bound satellites (rotation curves) could be significantly affected, and therefore used to measure or constrain the dark energy density. Here, isolated means that the gravitational effect of large nearby galaxies (specifically, of their dark matter halos) is negligible; examples of isolated dwarf galaxies include Antlia or DDO 190.

  14. Looking for the Northern Fermi Bubble with HAWC

    NASA Astrophysics Data System (ADS)

    Ayala, Hugo; Zhou, Hao; Huentemeyer, Petra; HAWC Collaboration

    2016-03-01

    The Fermi Bubbles were discovered in the GeV gamma-ray data from the Fermi Telescope in 2010. They extend up to 55° above and below the Galactic Center forming two large and homogeneous regions of spectrally hard gamma-ray emission. Understanding the mechanisms which produce the observed hard spectrum will help understand the origin of the Fermi Bubbles. Both hadronic and leptonic models can describe the spectrum of the bubbles, though the leptonic model can explain similar structures observed in microwave data from the WMAP and Planck satellites. Recent publications show that the spectrum of the Fermi Bubbles is well described by a power law with an exponential cutoff between 100MeV to 500GeV. Observing the Fermi Bubbles at higher gamma-ray energies will help constrain their spectrum. A steeper cutoff will favor a leptonic model. The High Altitude Water Cherenkov (HAWC) Observatory, located 4100m above sea level in Mexico, is designed to measure high-energy gamma rays between 100GeV to 100TeV. With a large field of view and good sensitivity to spatially extended sources, HAWC is the ground-based observatory best suited to detect extended regions like the Fermi Bubbles. We present a search for emission from the Fermi Bubble visible to HAWC.

  15. Cosmic X-ray and gamma-ray background from dark matter annihilation

    NASA Astrophysics Data System (ADS)

    Zavala, Jesús; Vogelsberger, Mark; Slatyer, Tracy R.; Loeb, Abraham; Springel, Volker

    2011-06-01

    The extragalactic background light (EBL) observed at multiple wavelengths is a promising tool to probe the nature of dark matter. This radiation might contain a significant contribution from gamma-rays produced promptly by dark matter particle annihilation in the many halos and subhalos within our past-light cone. Additionally, the electrons and positrons produced in the annihilation give energy to the cosmic microwave photons to populate the EBL with X-rays and gamma-rays. To study these signals, we create full-sky maps of the expected radiation from both of these contributions using the high-resolution Millennium-II simulation of cosmic structure formation. Our method also accounts for a possible enhancement of the annihilation rate by a Sommerfeld mechanism due to a Yukawa interaction between the dark matter particles prior to annihilation. We use upper limits on the contributions of unknown sources to the EBL to constrain the intrinsic properties of dark matter using a model-independent approach that can be employed as a template to test different particle physics models. These upper limits are based on observational measurements spanning 8 orders of magnitude in energy (from soft X-rays measured by the CHANDRA satellite to gamma-rays measured by the Fermi satellite), and on expectations for the contributions from nonblazar active galactic nuclei, blazars and star-forming galaxies. To exemplify this approach, we analyze a set of benchmark Sommerfeld-enhanced models that give the correct abundance of dark matter, satisfy constraints from the cosmic microwave background, and fit the cosmic ray spectra measured by PAMELA and Fermi without any contribution from local substructure. We find that these models are in conflict with the EBL constraints unless the contribution of unresolved substructure is small and the dark matter annihilation signal dominates the EBL. We conclude that provided the collisionless cold dark matter paradigm is accurate, even for

  16. FermiGrid

    SciTech Connect

    Yocum, D.R.; Berman, E.; Canal, P.; Chadwick, K.; Hesselroth, T.; Garzoglio, G.; Levshina, T.; Sergeev, V.; Sfiligoi, I.; Sharma, N.; Timm, S.; /Fermilab

    2007-05-01

    As one of the founding members of the Open Science Grid Consortium (OSG), Fermilab enables coherent access to its production resources through the Grid infrastructure system called FermiGrid. This system successfully provides for centrally managed grid services, opportunistic resource access, development of OSG Interfaces for Fermilab, and an interface to the Fermilab dCache system. FermiGrid supports virtual organizations (VOs) including high energy physics experiments (USCMS, MINOS, D0, CDF, ILC), astrophysics experiments (SDSS, Auger, DES), biology experiments (GADU, Nanohub) and educational activities.

  17. The Gamma-ray Sky with Fermi

    NASA Technical Reports Server (NTRS)

    Thompson, David

    2012-01-01

    Gamma rays reveal extreme, nonthermal conditions in the Universe. The Fermi Gamma-ray Space Telescope has been exploring the gamma-ray sky for more than four years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

  18. The Gamma-ray Universe through Fermi

    NASA Technical Reports Server (NTRS)

    Thompson, David J.

    2012-01-01

    Gamma rays, the most powerful form of light, reveal extreme conditions in the Universe. The Fermi Gamma-ray Space Telescope and its smaller cousin AGILE have been exploring the gamma-ray sky for several years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge ga.nuna-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

  19. Alternatives to dark matter and dark energy

    NASA Astrophysics Data System (ADS)

    Mannheim, Philip D.

    2006-04-01

    We review the underpinnings of the standard Newton Einstein theory of gravity, and identify where it could possibly go wrong. In particular, we discuss the logical independence from each other of the general covariance principle, the equivalence principle and the Einstein equations, and discuss how to constrain the matter energy momentum tensor which serves as the source of gravity. We identify the a priori assumption of the validity of standard gravity on all distance scales as the root cause of the dark matter and dark energy problems, and discuss how the freedom currently present in gravitational theory can enable us to construct candidate alternatives to the standard theory in which the dark matter and dark energy problems could then be resolved. We identify three generic aspects of these alternate approaches: that it is a universal acceleration scale which determines when a luminous Newtonian expectation is to fail to fit data, that there is a global cosmological effect on local galactic motions which can replace galactic dark matter, and that to solve the cosmological constant problem it is not necessary to quench the cosmological constant itself, but only the amount by which it gravitates.

  20. Gravitino Dark Matter

    SciTech Connect

    Buchmueller, Wilfried

    2010-02-10

    Gravitino dark matter, together with thermal leptogenesis, implies an upper bound on the masses of superparticles. In the case of broken R-parity the constraints from primordial nucleosynthesis are naturally satisfied and decaying gravitinos lead to characteristic signatures in high energy cosmic rays. Electron and positron fluxes from gravitino decays cannot explain both, the PAMELA positron fraction and the electron+positron flux recently measured by Fermi LAT. The observed fluxes require astrophysical sources. The measured antiproton flux allows for a sizable contribution of decaying gravitinos to the gamma-ray spectrum, in particular a line at an energy below 300 GeV.

  1. More Fermi questions

    NASA Astrophysics Data System (ADS)

    Bouffard, Karen

    1999-09-01

    "Fermi" questions are a popular component of most Physics Olympics meets. Asking students to make a reasonable assumption about a problem and give answers in terms of order of magnitude is not only a great challenge for a competition, but is also a valued teaching strategy in the classroom.

  2. Fermi TGF detection map

    NASA Video Gallery

    Fermi’s Gamma-ray Burst Monitor detected 130 TGFs from August 2008 to the end of 2010. Thanks to instrument tweaks, the team has been able to improve the detection rate to several TGFs per week. ...

  3. Interaction quenches of Fermi gases

    SciTech Connect

    Uhrig, Goetz S.

    2009-12-15

    It is shown that the jump in the momentum distribution of Fermi gases evolves smoothly for small and intermediate times once an interaction between the fermions is suddenly switched on. The jump does not vanish abruptly. The loci in momentum space where the jumps occur are those of the noninteracting Fermi sea. No relaxation of the Fermi surface geometry takes place.

  4. Correlation between dark matter and dark radiation in string compactifications

    NASA Astrophysics Data System (ADS)

    Allahverdi, Rouzbeh; Cicoli, Michele; Dutta, Bhaskar; Sinha, Kuver

    2014-10-01

    Reheating in string compactifications is generically driven by the decay of the lightest modulus which produces Standard Model particles, dark matter and light hidden sector degrees of freedom that behave as dark radiation. This common origin allows us to find an interesting correlation between dark matter and dark radiation. By combining present upper bounds on the effective number of neutrino species Neff with lower bounds on the reheating temperature as a function of the dark matter mass mDM from Fermi data, we obtain strong constraints on the (Neff, mDM)-plane. Most of the allowed region in this plane corresponds to non-thermal scenarios with Higgsino-like dark matter. Thermal dark matter can be allowed only if Neff tends to its Standard Model value. We show that the above situation is realised in models with perturbative moduli stabilisation where the production of dark radiation is unavoidable since bulk closed string axions remain light and do not get eaten up by anomalous U(1)s.

  5. Correlation between dark matter and dark radiation in string compactifications

    SciTech Connect

    Allahverdi, Rouzbeh; Cicoli, Michele; Dutta, Bhaskar; Sinha, Kuver E-mail: mcicoli@ictp.it E-mail: kusinha@syr.edu

    2014-10-01

    Reheating in string compactifications is generically driven by the decay of the lightest modulus which produces Standard Model particles, dark matter and light hidden sector degrees of freedom that behave as dark radiation. This common origin allows us to find an interesting correlation between dark matter and dark radiation. By combining present upper bounds on the effective number of neutrino species N{sub eff} with lower bounds on the reheating temperature as a function of the dark matter mass m{sub DM} from Fermi data, we obtain strong constraints on the (N{sub eff}, m{sub DM})-plane. Most of the allowed region in this plane corresponds to non-thermal scenarios with Higgsino-like dark matter. Thermal dark matter can be allowed only if N{sub eff} tends to its Standard Model value. We show that the above situation is realised in models with perturbative moduli stabilisation where the production of dark radiation is unavoidable since bulk closed string axions remain light and do not get eaten up by anomalous U(1)s.

  6. Direct reconstruction of dark energy.

    PubMed

    Clarkson, Chris; Zunckel, Caroline

    2010-05-28

    An important issue in cosmology is reconstructing the effective dark energy equation of state directly from observations. With so few physically motivated models, future dark energy studies cannot only be based on constraining a dark energy parameter space. We present a new nonparametric method which can accurately reconstruct a wide variety of dark energy behavior with no prior assumptions about it. It is simple, quick and relatively accurate, and involves no expensive explorations of parameter space. The technique uses principal component analysis and a combination of information criteria to identify real features in the data, and tailors the fitting functions to pick up trends and smooth over noise. We find that we can constrain a large variety of w(z) models to within 10%-20% at redshifts z≲1 using just SNAP-quality data. PMID:20867085

  7. Galactic-centre gamma rays in CMSSM dark matter scenarios

    SciTech Connect

    Ellis, John; Olive, Keith A.; Spanos, Vassilis C. E-mail: olive@physics.umn.edu

    2011-10-01

    We study the production of γ rays via LSP annihilations in the core of the Galaxy as a possible experimental signature of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which supersymmetry-breaking parameters are assumed to be universal at the GUT scale, assuming also that the LSP is the lightest neutralino χ. The part of the CMSSM parameter space that is compatible with the measured astrophysical density of cold dark matter is known to include a (τ-tilde {sub 1})−χ coannihilation strip, a focus-point strip where χ has an enhanced Higgsino component, and a funnel at large tan β where the annihilation rate is enhanced by the poles of nearby heavy MSSM Higgs bosons, A/H. We calculate the total annihilation rates, the fractions of annihilations into different Standard Model final states and the resulting fluxes of γ rays for CMSSM scenarios along these strips. We observe that typical annihilation rates are much smaller in the coannihilation strip for tan β = 10 than along the focus-point strip or for tan β = 55, and that the annihilation branching ratios differ greatly between the different dark matter strips. Whereas the current Fermi-LAT data are not sensitive to any of the CMSSM scenarios studied, and the calculated γ-ray fluxes are probably unobservably low along the coannihilation strip for tan β = 10, we find that substantial portions of the focus-point strips and rapid-annihilation funnel regions could be pressured by several more years of Fermi-LAT data, if understanding of the astrophysical background and/or systematic uncertainties can be improved in parallel.

  8. Constraining extended gamma-ray emission from galaxy clusters

    NASA Astrophysics Data System (ADS)

    Han, Jiaxin; Frenk, Carlos S.; Eke, Vincent R.; Gao, Liang; White, Simon D. M.; Boyarsky, Alexey; Malyshev, Denys; Ruchayskiy, Oleg

    2012-12-01

    Cold dark matter models predict the existence of a large number of substructures within dark matter haloes. If the cold dark matter consists of weakly interacting massive particles, their annihilation within these substructures could lead to diffuse GeV emission that would dominate the annihilation signal of the host halo. In this work we search for GeV emission from three nearby galaxy clusters: Coma, Virgo and Fornax. We first remove known extragalactic and galactic diffuse gamma-ray backgrounds and point sources from the Fermi 2-yr catalogue and find a significant residual diffuse emission in all three clusters. We then investigate whether this emission is due to (i) unresolved point sources, (ii) dark matter annihilation or (iii) cosmic rays (CR). Using 45 months of Fermi-Large Area Telescope (Fermi-LAT) data we detect several new point sources (not present in the Fermi 2-yr point source catalogue) which contaminate the signal previously analysed by Han et al. Including these and accounting for the effects of undetected point sources, we find no significant detection of extended emission from the three clusters studied. Instead, we determine upper limits on emission due to dark matter annihilation and CR. For Fornax and Virgo, the limits on CR emission are consistent with theoretical models, but for Coma the upper limit is a factor of 2 below the theoretical expectation. Allowing for systematic uncertainties associated with the treatment of CR, the upper limits on the cross-section for dark matter annihilation from our clusters are more stringent than those from analyses of dwarf galaxies in the Milky Way. Adopting a boost factor of ˜103 from subhaloes on cluster luminosity as suggested by recent theoretical models, we rule out the thermal cross-section for supersymmetric dark matter particles for masses as large as 100 GeV (depending on the annihilation channel).

  9. Large Extra Dimension and Dark Matter Detection

    SciTech Connect

    Qin Bo; Starkman, Glenn D.; Silk, Joseph

    2008-01-03

    If our space has the large extra dimensions as proposed by Arkani-Hamed, Dimopoulos and Dvali (ADD), then gravity would start to deviate from Newtonian gravity and be greatly enhanced in sub-millimeter scales. Here we show that in the ADD scenario, gravity could play an important role (compared to the weak interaction) in the interactions between dark matter particles and the electron. We find that for typical WIMP dark matter, such dark matter-electron 'gravitational' scattering cross section may be much larger than the dark matter-nucleon cross section constrained by current dark matter experiments.

  10. Large Extra Dimension and Dark Matter Detection

    NASA Astrophysics Data System (ADS)

    Qin, Bo; Starkman, Glenn D.; Silk, Joseph

    2008-01-01

    If our space has the large extra dimensions as proposed by Arkani-Hamed, Dimopoulos and Dvali (ADD), then gravity would start to deviate from Newtonian gravity and be greatly enhanced in sub-millimeter scales. Here we show that in the ADD scenario, gravity could play an important role (compared to the weak interaction) in the interactions between dark matter particles and the electron. We find that for typical WIMP dark matter, such dark matter-electron ``gravitational'' scattering cross section may be much larger than the dark matter-nucleon cross section constrained by current dark matter experiments.

  11. Understanding the Fundamental Properties of Dark Matter & Dark Energy in Structure formation and Cosmology

    SciTech Connect

    Ellis, Richard, S.

    2008-02-01

    This program is concerned with developing and verifying the validityof observational methods for constraining the properties of dark matter and dark energy in the universe. Excellent progress has been made in comparing observational projects involving weak gravitational lensing using both ground and space-based instruments, in further constraining the nature of dark matter via precise measures of its distribution in clusters of galaxies using strong gravitational lensing, in demonstrating the possible limitations of using distant supernovae in future dark energy missions, and in investigating the requirement for ground-based surveys of baryonic acoustic oscillations.

  12. Reionization and dark matter decay

    NASA Astrophysics Data System (ADS)

    Oldengott, Isabel M.; Boriero, Daniel; Schwarz, Dominik J.

    2016-08-01

    Cosmic reionization and dark matter decay can impact observations of the cosmic microwave sky in a similar way. A simultaneous study of both effects is required to constrain unstable dark matter from cosmic microwave background observations. We compare two reionization models with and without dark matter decay. We find that a reionization model that fits also data from quasars and star forming galaxies results in tighter constraints on the reionization optical depth τreio, but weaker constraints on the spectral index ns than the conventional parametrization. We use the Planck 2015 data to constrain the effective decay rate of dark matter to Γeff < 2.9 × 10‑25/s at 95% C.L. This limit is robust and model independent. It holds for any type of decaying dark matter and it depends only weakly on the chosen parametrization of astrophysical reionization. For light dark matter particles that decay exclusively into electromagnetic components this implies a limit of Γ < 5.3 × 10‑26/s at 95% C.L. Specifying the decay channels, we apply our result to the case of keV-mass sterile neutrinos as dark matter candidates and obtain constraints on their mixing angle and mass, which are comparable to the ones from the diffuse X-ray background.

  13. Dark Matters

    ScienceCinema

    Joseph Silk

    2010-01-08

    One of the greatest mysteries in the cosmos is that it is mostly dark.  Astronomers and particle physicists today are seeking to unravel the nature of this mysterious, but pervasive dark matter which has profoundly influenced the formation of structure in the universe.  I will describe the complex interplay between galaxy formation and dark matter detectability and review recent attempts to measure particle dark matter by direct and indirect means.

  14. Dark Matters

    SciTech Connect

    Joseph Silk

    2009-09-23

    One of the greatest mysteries in the cosmos is that it is mostly dark.  Astronomers and particle physicists today are seeking to unravel the nature of this mysterious, but pervasive dark matter which has profoundly influenced the formation of structure in the universe.  I will describe the complex interplay between galaxy formation and dark matter detectability and review recent attempts to measure particle dark matter by direct and indirect means.

  15. Light thoughts on dark energy

    SciTech Connect

    Linder, Eric V.

    2004-04-01

    The physical process leading to the acceleration of the expansion of the universe is unknown. It may involve new high energy physics or extensions to gravitation. Calling this generically dark energy, we examine the consistencies and relations between these two approaches, showing that an effective equation of state function w(z) is broadly useful in describing the properties of the dark energy. A variety of cosmological observations can provide important information on the dynamics of dark energy and the future looks bright for constraining dark energy, though both the measurements and the interpretation will be challenging. We also discuss a more direct relation between the spacetime geometry and acceleration, via ''geometric dark energy'' from the Ricci scalar, and superacceleration or phantom energy where the fate of the universe may be more gentle than the Big Rip.

  16. Multi-component dark matter in the light of new AMS-02 data

    NASA Astrophysics Data System (ADS)

    Lai, Chang; Huang, Da; Geng, Chao-Qiang

    2015-10-01

    We study the possible positron/electron excesses within the multi-component leptonically decaying dark matter (DM) scenario by fitting the most recent AMS-02 data on the positron fraction and total e+ + e- flux. We show that both the single- and two-component DM models are able to fit the two AMS-02 datasets. However, the single-component DM model favors the e+/e- energy cutoff from the DM decay less than 1 TeV through the τ-channel, which is already well constrained by the diffuse γ-ray spectrum measured by Fermi-LAT. For the two-component case with closing the τ-mode for the heavy DM particle, we find that the new AMS-02 data allows the heavy DM cutoff larger than 1 TeV, providing a good description of the high-energy behavior of the total e+ + e- flux and satisfying the diffuse γ-ray constraint.

  17. Processing GPS Receiver Data for Improved Fermi GLAST Navigation

    NASA Technical Reports Server (NTRS)

    Woodard, Mark A.

    2008-01-01

    Fermi GLAST s 5-year mission objectives: a) Explore the most extreme environments in the Universe. b) Search for signs of new laws of physics and what composes the mysterious Dark Matter. c) Explain how black holes accelerate immense jets of material to nearly light speed. d) Help crack the mysteries of gamma-ray bursts. e) Answer long-standing questions across a broad range of topics, including solar flares, pulsars and the origin of cosmic rays.

  18. Gravity-mediated (or composite) Dark Matter confronts astrophysical data

    NASA Astrophysics Data System (ADS)

    Lee, Hyun Min; Park, Myeonghun; Sanz, Verónica

    2014-05-01

    We consider the astrophysical bounds on a new form of dark matter, the so called Gravity-mediated Dark Matter. In this scenario, dark matter communicates with us through a mediator sector composed of gravitational resonances, namely a new scalar (radion) and a massive spin-two resonance (massive graviton). We consider specific models motivated by natural electroweak symmetry breaking or weak-scale dark matter in the context of models in warped extra-dimensions and their composite duals. The main Dark Matter annihilation mechanism is due to the interactions of KK gravitons to gauge bosons that propagate in bulk. We impose the bounds on monochromatic or continuum photons from Fermi-LAT and HESS. We also explore scenarios in which the Fermi gamma-ray line could be a manifestation of Gravity-mediated Dark Matter.

  19. GRB Studies with Fermi

    NASA Technical Reports Server (NTRS)

    Meegan, Charles A.

    2008-01-01

    This slide presentation reviews the studies of Gamma Ray Bursts (GRB) with the Fermi Gamma Ray Space Telescope. Included are pictures of the observatory, with illustrations of the Large Area Telescope (LAT), and the Gamma-ray Burst Monitor (GBM) including information about both their capabilities. Graphs showing the GBM count rate over time after the GBM trigger for three GRBs, preliminary charts showing the multiple detector light curves the spectroscopy of the main LAT peak and the spectral evolution of GRB 080916C Burst Temporally-extended LAT emission.

  20. Dark matters

    NASA Astrophysics Data System (ADS)

    Steigman, Gary

    The observational evidence for dark matter in the universe is reviewed. Constraints on the baryon density from primordial nucleosynthesis are presented and compared to the dynamical estimates of the mass on various scales. Baryons can account for the observed luminous mass as well as some, perhaps most, of the 'observed' dark mass. However if, as inflation/naturalness suggest, the total density of the universe is equal to the critical density, then nonbaryonic dark matter is required. The assets and liabilities of, as well as the candidates for, hot and cold dark matter are outlined. At present, there is no completely satisfactory candidate for nonbaryonic dark matter.

  1. Dark matter in NGC 4472

    NASA Technical Reports Server (NTRS)

    Loewenstein, Michael

    1992-01-01

    An attempt is made to constrain the total mass distribution of the giant elliptical galaxy NGC 4472 by constructing simultaneous equilibrium models for the gas and stars. Emphasis is given to reconciling the value of the emission-weighted average value of kT derived from the Ginga spectrum with the amount of dark matter needed to account for velocity dispersion observations.

  2. Search for Gamma-Ray Emission from DES Dwarf Spheroidal Galaxy Candidates with Fermi-LAT Data

    SciTech Connect

    Drlica-Wagner, A.; et al.

    2015-08-04

    Due to their proximity, high dark-matter (DM) content, and apparent absence of non-thermal processes, Milky Way dwarf spheroidal satellite galaxies (dSphs) are excellent targets for the indirect detection of DM. Recently, eight new dSph candidates were discovered using the first year of data from the Dark Energy Survey (DES). We searched for gamma-ray emission coincident with the positions of these new objects in six years of Fermi Large Area Telescope data. We found no significant excesses of gamma-ray emission. Under the assumption that the DES candidates are dSphs with DM halo properties similar to the known dSphs, we computed individual and combined limits on the velocity-averaged DM annihilation cross section for these new targets. If the estimated DM content of these dSph candidates is confirmed, they will constrain the annihilation cross section to lie below the thermal relic cross section for DM particles with masses $\\lesssim 20\\,\\mathrm{GeV}$ annihilating via the $b\\bar{b}$ or τ(+)τ(-) channels.

  3. Search for Gamma-Ray Emission from DES Dwarf Spheroidal Galaxy Candidates with Fermi-LAT Data

    NASA Astrophysics Data System (ADS)

    Drlica-Wagner, A.; Albert, A.; Bechtol, K.; Wood, M.; Strigari, L.; Sánchez-Conde, M.; Baldini, L.; Essig, R.; Cohen-Tanugi, J.; Anderson, B.; Bellazzini, R.; Bloom, E. D.; Caputo, R.; Cecchi, C.; Charles, E.; Chiang, J.; de Angelis, A.; Funk, S.; Fusco, P.; Gargano, F.; Giglietto, N.; Giordano, F.; Guiriec, S.; Gustafsson, M.; Kuss, M.; Loparco, F.; Lubrano, P.; Mirabal, N.; Mizuno, T.; Morselli, A.; Ohsugi, T.; Orlando, E.; Persic, M.; Rainò, S.; Sehgal, N.; Spada, F.; Suson, D. J.; Zaharijas, G.; Zimmer, S.; Fermi-LAT Collaboration; Abbott, T.; Allam, S.; Balbinot, E.; Bauer, A. H.; Benoit-Lévy, A.; Bernstein, R. A.; Bernstein, G. M.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Carnero Rosell, A.; Castander, F. J.; Covarrubias, R.; D'Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Cunha, C. E.; Eifler, T. F.; Estrada, J.; Evrard, A. E.; Fausti Neto, A.; Fernandez, E.; Finley, D. A.; Flaugher, B.; Frieman, J.; Gaztanaga, E.; Gerdes, D.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; Jain, B.; James, D.; Jeltema, T.; Kent, S.; Kron, R.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Luque, E.; Maia, M. A. G.; Makler, M.; March, M.; Marshall, J.; Martini, P.; Merritt, K. W.; Miller, C.; Miquel, R.; Mohr, J.; Neilsen, E.; Nord, B.; Ogando, R.; Peoples, J.; Petravick, D.; Pieres, A.; Plazas, A. A.; Queiroz, A.; Romer, A. K.; Roodman, A.; Rykoff, E. S.; Sako, M.; Sanchez, E.; Santiago, B.; Scarpine, V.; Schubnell, M.; Sevilla, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thaler, J.; Thomas, D.; Tucker, D.; Walker, A. R.; Wechsler, R. H.; Wester, W.; Williams, P.; Yanny, B.; Zuntz, J.; DES Collaboration

    2015-08-01

    Due to their proximity, high dark-matter (DM) content, and apparent absence of non-thermal processes, Milky Way dwarf spheroidal satellite galaxies (dSphs) are excellent targets for the indirect detection of DM. Recently, eight new dSph candidates were discovered using the first year of data from the Dark Energy Survey (DES). We searched for gamma-ray emission coincident with the positions of these new objects in six years of Fermi Large Area Telescope data. We found no significant excesses of gamma-ray emission. Under the assumption that the DES candidates are dSphs with DM halo properties similar to the known dSphs, we computed individual and combined limits on the velocity-averaged DM annihilation cross section for these new targets. If the estimated DM content of these dSph candidates is confirmed, they will constrain the annihilation cross section to lie below the thermal relic cross section for DM particles with masses ≲ 20 {GeV} annihilating via the b\\bar{b} or τ+τ- channels.

  4. Cosmic Ray Spectra in Nambu-Goldstone Dark Matter Models

    SciTech Connect

    Ibe, Masahiro; Murayama, Hitoshi; Shirai, Satoshi; Yanagida, Tsutomu T.; ,

    2010-06-11

    We discuss the cosmic ray spectra in annihilating/decaying Nambu-Goldstone dark matter models. The recent observed positron/electron excesses at PAMELA and Fermi experiments are well fitted by the dark matter with a mass of 3TeV for the annihilating model, while with a mass of 6TeV for the decaying model. We also show that the Nambu-Goldstone dark matter models predict a distinctive gamma-ray spectrum in a certain parameter space.

  5. Decaying hidden dark matter in warped compactification

    SciTech Connect

    Chen, Xingang

    2009-09-01

    The recent PAMELA and ATIC/Fermi/HESS experiments have observed an excess of electrons and positrons, but not anti-protons, in the high energy cosmic rays. To explain this result, we construct a decaying hidden dark matter model in string theory compactification that incorporates the following two ingredients, the hidden dark matter scenario in warped compactification and the phenomenological proposal of hidden light particles that decay to the Standard Model. In this model, on higher dimensional warped branes, various warped Kaluza-Klein particles and the zero-mode of gauge field play roles of the hidden dark matter or mediators to the Standard Model.

  6. Explorations in dark energy

    NASA Astrophysics Data System (ADS)

    Bozek, Brandon

    This dissertation describes three research projects on the topic of dark energy. The first project is an analysis of a scalar field model of dark energy with an exponential potential using the Dark Energy Task Force (DETF) simulated data models. Using Markov Chain Monte Carlo sampling techniques we examine the ability of each simulated data set to constrain the parameter space of the exponential potential for data sets based on a cosmological constant and a specific exponential scalar field model. We compare our results with the constraining power calculated by the DETF using their "w 0--wa" parameterization of the dark energy. We find that respective increases in constraining power from one stage to the next produced by our analysis give results consistent with DETF results. To further investigate the potential impact of future experiments, we also generate simulated data for an exponential model background cosmology which can not be distinguished from a cosmological constant at DETF Stage 2, and show that for this cosmology good DETF Stage 4 data would exclude a cosmological constant by better than 3sigma. The second project details this analysis on a Inverse Power Law (IPL) or "Ratra-Peebles" (RP) model. This model is a member of a popular subset of scalar field quintessence models that exhibit "tracking" behavior that make this model particularly theoretically interesting. We find that the relative increase in constraining power on the parameter space of this model is consistent to what was found in the first project and the DETF report. We also show, using a background cosmology based on an IPL scalar field model that is consistent with a cosmological constant with Stage 2 data, that good DETF Stage 4 data would exclude a cosmological constant by better than 3sigma. The third project extends the Causal Entropic Principle to predict the preferred curvature within the "multiverse". The Causal Entropic Principle (Bousso, et al.) provides an alternative approach

  7. The Characterization of the Gamma-Ray Signal from the Central Milky Way: A Compelling Case for Annihilating Dark Matter

    SciTech Connect

    Daylan, Tansu; Finkbeiner, Douglas P.; Hooper, Dan; Linden, Tim; Portillo, Stephen K. N.; Rodd, Nicholas L.; Slatyer, Tracy R.

    2014-02-26

    Past studies have identified a spatially extended excess of ~1-3 GeV gamma rays from the region surrounding the Galactic Center, consistent with the emission expected from annihilating dark matter. We revisit and scrutinize this signal with the intention of further constraining its characteristics and origin. By applying cuts to the Fermi event parameter CTBCORE, we suppress the tails of the point spread function and generate high resolution gamma-ray maps, enabling us to more easily separate the various gamma-ray components. Within these maps, we find the GeV excess to be robust and highly statistically significant, with a spectrum, angular distribution, and overall normalization that is in good agreement with that predicted by simple annihilating dark matter models. For example, the signal is very well fit by a 31-40 GeV dark matter particle annihilating to b quarks with an annihilation cross section of sigma v = (1.4-2.0) x 10^-26 cm^3/s (normalized to a local dark matter density of 0.3 GeV/cm^3). Furthermore, we confirm that the angular distribution of the excess is approximately spherically symmetric and centered around the dynamical center of the Milky Way (within ~0.05 degrees of Sgr A*), showing no sign of elongation along or perpendicular to the Galactic Plane. The signal is observed to extend to at least 10 degrees from the Galactic Center, disfavoring the possibility that this emission originates from millisecond pulsars.

  8. Double-Disk Dark Matter

    NASA Astrophysics Data System (ADS)

    Fan, JiJi; Katz, Andrey; Randall, Lisa; Reece, Matthew

    2013-09-01

    Based on observational tests of large scale structure and constraints on halo structure, dark matter is generally taken to be cold and essentially collisionless. On the other hand, given the large number of particles and forces in the visible world, a more complex dark sector could be a reasonable or even likely possibility. This hypothesis leads to testable consequences, perhaps portending the discovery of a rich hidden world neighboring our own. We consider a scenario that readily satisfies current bounds that we call Partially Interacting Dark Matter (PIDM). This scenario contains self-interacting dark matter, but it is not the dominant component. Even if PIDM contains only a fraction of the net dark matter density, comparable to the baryonic fraction, the subdominant component’s interactions can lead to interesting and potentially observable consequences. Our primary focus will be the special case of Double-Disk Dark Matter (DDDM), in which self-interactions allow the dark matter to lose enough energy to lead to dynamics similar to those in the baryonic sector. We explore a simple model in which DDDM can cool efficiently and form a disk within galaxies, and we evaluate some of the possible observational signatures. The most prominent signal of such a scenario could be an enhanced indirect detection signature with a distinctive spatial distribution. Even though subdominant, the enhanced density at the center of the galaxy and possibly throughout the plane of the galaxy (depending on precise alignment) can lead to large boost factors, and could even explain a signature as large as the 130 GeV Fermi line. Such scenarios also predict additional dark radiation degrees of freedom that could soon be detectable and would influence the interpretation of future data, such as that from Planck and from the Gaia satellite. We consider this to be the first step toward exploring a rich array of new possibilities for dark matter dynamics.

  9. Propagation of Light through Composite Dark Matter

    NASA Astrophysics Data System (ADS)

    Kvam, Audrey; Latimer, David

    2013-10-01

    A concordance of observations indicates that around 80% of the matter in the universe is some unknown dark matter. This dark matter could be comprised of a single structureless particle, but much richer theories exist. Signals from the DAMA, CoGeNT, and CDMS-II dark matter detectors along with the non-observation of dark matter by other detectors motivate theories of composite dark matter along with a ``dark'' electromagnetic sector. The composite models propose baryon-like or atom-like dark matter. If photons kinetically mix with the ``dark'' photons, then light traveling through dark matter will experience dispersion. We expect the dispersion to be approximated by the Drude-Lorentz model where the model parameters are particular to a given dark matter candidate. As light travels through the dispersive medium, it can accrue to a frequency-dependent time lag. Measurement of such a time lag can yield clues as to the nature of the dark matter. As a first application, we model hydrogenic dark atoms and use astrophysical data to constrain the mass, binding energy, and the fractional electric charge of the dark atoms.

  10. Fermi (nee GLAST) at Six Months

    NASA Technical Reports Server (NTRS)

    Ritz, Steve

    2009-01-01

    The Fermi Gamma-ray Space Telescope, formerly called GLAST, is a mission to measure the cosmic gamma-ray flux in the energy range 20 MeV to >300 GeV, with supporting measurements for gamma-ray bursts from 8 keV to 30 MeV. In addition to breakthrough capabilities in energy coverage and localization, the very large field of view enables observations of 20% of the sky at any instant, and the entire sky on a timescale of a few hours. With its recent launch on 11 June 2008, Fermi now opens a new and important window on a wide variety of phenomena, including pulsars, black holes and active galactic nuclei, gamma-ray bursts, the origin of cosmic rays and supernova remnants, and searches for hypothetical new phenomena such as supersymmetric dark matter annihilations. In addition to early results and the science opportunities, this talk includes a description of the instruments and the mission status and plans.