Munch

Authors: Gianfranco Bertone (Fermilab), Andrew R. Zentner (KICP, UChicago), Joseph Silk (Oxford)
Categories: astro-ph hep-ph
Comments: 11 pages, 5 figures
Report-no: FERMILAB-PUB-05-408-A

We study the prospects for detecting gamma-rays from Dark Matter (DM) annihilations in enhancements of the DM density (mini-spikes) around intermediate-mass black holes with masses in the range $10^2 \lsim M / \msun \lsim 10^6$. Focusing on two different IMBH formation scenarios, we show that, for typical values of mass and cross section of common DM candidates, mini-spikes, produced by the adiabatic growth of DM around pregalactic IMBHs, would be bright sources of gamma-rays, which could be easily detected with large field-of-view gamma-ray experiments such as GLAST, and further studied with smaller field-of-view, larger-area experiments like Air Cherenkov Telescopes CANGAROO, HESS, MAGIC and VERITAS. The detection of many gamma-ray sources not associated with a luminous component of the Local Group, and with identical cut-offs in their energy spectra at the mass of the DM particle, would provide a potential smoking-gun signature of DM annihilations and shed new light on the nature of intermediate and supermassive Black Holes.

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Discovery and identification of the very high redshift afterglow of GRB 050904

Authors: J. Haislip, M. Nysewander, D. Reichart, A. Levan, N. Tanvir, S. Cenko, D. Fox, P. Price, A. Castro-Tirado, J. Gorosabel, C. Evans, E. Figueredo, C. MacLeod, J. Kirschbrown, M. Jelinek, S. Guziy, A. de Ugarte Postigo, E. Cypriano, A. LaCluyze, J. Graham, R. Priddey, R. Chapman, J. Rhoads, A. Fruchter, D. Lamb, C. Kouveliotou, R. Wijers, B. Schmidt, A. Soderberg, S. Kulkarni, F. Harrison, D. Moon, A. Gal-Yam, M. Kasliwal, R. Hudec, S. Vitek, P. Kubanek, J. Crain, A. Foster, M. Bayliss, J. Clemens, J. Bartelme, et al
Categories: astro-ph
Comments: Submitted to Nature, 11 pages, 3 figures, LaTeX

In 2000, Lamb and Reichart predicted that gamma-ray bursts (GRBs) and their afterglows occur in sufficient numbers and at sufficient brightnesses at very high redshifts (z > 5) to eventually replace quasars as the preferred probe of element formation and reionization in the early universe and to be used to characterize the star-formation history of the early universe, perhaps back to when the first stars formed. Here we report the discovery of the afterglow of GRB 050904 and the identification of GRB 050904 as the first very high redshift GRB. We measure its redshift to be 6.39(+0.11,-0.12), which is consistent with the reported spectroscopic redshift (6.29 +/- 0.01). Furthermore, just redward of Ly-alpha the flux is suppressed by a factor of three on the first night, but returns to expected levels by the fourth night. We propose that this is due to absorption by molecular hydrogen that was excited to rovibrational states by the GRB's prompt emission, but was then overtaken by the jet. Now that very high redshift GRBs have been shown to exist, and at least in this case the afterglow was very bright, observing programs that are designed to capitalize on this science will likely drive a new era of study of the early universe, using GRBs as probes.

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Measuring Dark Matter at Colliders

Authors: Andreas Birkedal
Categories: hep-ph
Comments: 8 pages, 8 figures; Plenary talk given at PASCOS 05, Gyeongju, Republic of Korea, June 2005
Report-no: SCIPP-05-08, UFIFT-HEP-05-25

We investigate the need and prospects for measuring dark matter properties at particle collider experiments. We discuss the connections between the inferred properties of particle dark matter and the physics that is expected to be uncovered by the Large Hadron Collider (LHC) and the International Linear Collider (ILC) and motivate the necessity of measuring detailed dark matter properties at a collider. We then investigate a model-independent signature of dark matter at a collider and discuss its observability. We next examine the prospects for making precise measurements of dark matter properties using two example points in minimal supergravity (mSUGRA) parameter space. One of the primary difficulties encountered in such measurements is lack of constraint on the masses of unobservable heavy states. We discuss a new method for experimentally deriving estimates for such heavy masses and then conclude.

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Dark Matter before the LHC in a Natural Supersymmetric Standard Model

Authors: Ryuichiro Kitano, Yasunori Nomura
Categories: hep-ph
Comments: 9 pages, 3 figures
Report-no: SLAC-PUB-11487, UCB-PTH-05/29, LBNL-58876

We show that the solid lower bound of about 10^{-44} cm^2 is obtained for the cross section between the supersymmetric dark matter and nucleon in a theory in which the supersymmetric fine-tuning problem is solved without extending the Higgs sector at the weak scale. This bound arises because of relatively small superparticle masses and a fortunate correlation that the two dominant diagrams for the dark matter detection always interfere constructively if the constraint from the b -> s \gamma measurements is obeyed. It is, therefore, quite promising in the present scenario that the supersymmetric dark matter is discovered before the LHC, assuming that the dark matter is the lightest supersymmetric particle.

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MOND and Cosmology

Authors: R.H. Sanders
Categories: astro-ph
Comments: 8 pages, LaTeX, 2 figures, to appear in proceedings of IAP05 in Paris: Mass Profiles and Shapes of Cosmological Structures, G. Mamon, F. Combes, C. Deffayet and B. Fort (eds), (EDP-Sciences 2005)

I review various ideas on MOND cosmology and structure formation beginning with non-relativistic models in analogy with Newtonian cosmology. I discuss relativistic MOND cosmology in the context of Bekenstein's theory and propose an alternative biscalar effective theory of MOND in which the acceleration parameter is identified with the cosmic time derivative of a matter coupling scalar field. Cosmic CDM appears in this theory as scalar field oscillations of the auxiliary "coupling strength" field.

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Evidence for a Non-Expanding Universe: Surface Brightness Data From HUDF

Authors: Eric J. Lerner (Lawrenceville Plasma Physics)
Categories: astro-ph
Comments: 16 pages, 9 figures, to be published in the Proceedings of the First Crisis in Cosmology Conference, AIP proceedings series

Surface brightness data can distinguish between a Friedman-Robertson-Walker expanding universe and a non-expanding universe. For surface brightness measured in AB magnitudes per angular area, all FRW models, regardless of cosmological parameters, predict that surface brightness declines with redshift as (z+1)^-3, while any non-expanding model predicts that surface brightness is constant with distance and thus with z. High-z UV surface brightness data for galaxies from the Hubble Ultra Deep Field and low-z data from GALEX are used to test the predictions of these two models up to z=6. A preliminary analysis presented here of samples observed at the same at-galaxy wavelengths in the UV shows that surface brightness is constant, mu=kz^0.026+-0.15, consistent with the non-expanding model. This relationship holds if distance is linearly proportional to z at all redshifts, but seems insensitive to the particular choice of d-z relationship. Attempts to reconcile the data with FRW predictions by assuming that high-z galaxies have intrinsically higher surface brightness than low-z galaxies appear to face insurmountable problems. The intrinsic FUV surface brightness required by the FRW models for high-z galaxies exceeds the maximum FUV surface brightness of any low-z galaxy by as much as a factor of 40. Dust absorption appears to make such extremely high intrinsic FUV surface brightness physically impossible. If confirmed by further analysis, the impossibility of such high-surface-brightness galaxies would rule out all FRW expanding universe (big bang) models.

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Cosmology from supernova magnification maps

Authors: Asantha Cooray, Daniel Holz, Dragan Huterer
Categories: astro-ph
Comments: 4 pages, 2 figures, ApJL submitted; "Signal" discussed here is the extra covariance in astro-ph/0509581

High-z Type Ia supernovae are expected to be gravitationally lensed by the foreground distribution of large-scale structure. The resulting magnification of supernovae is statistically measurable, and the angular correlation of the magnification pattern directly probes the integrated mass density along the line of sight. Measurements of cosmic magnification of supernovae therefore complements galaxy shear measurements in providing a direct measure of clustering of the dark matter. As the number of supernovae is typically much smaller than the number of sheared galaxies, the two-point correlation function of lensed Type Ia supernovae suffers from significantly increased shot noise. Neverthless, we find that the magnification map of a large sample of supernovae, such as that expected from next generation dedicated searches, will be easily measurable and provide an important cosmological tool. For example, a search over 20 sq. deg. over five years leading to a sample of ~ 10,000 supernovae would measure the angular power spectrum of cosmic magnification with a cumulative signal-to-noise ratio of ~20. This detection can be further improved once the supernova distance measurements are cross-correlated with measurements of the foreground galaxy distribution. The magnification maps made using supernovae can be used for important cross-checks with traditional lensing shear statistics obtained in the same fields, as well as help to control systematics. We discuss two applications of supernova magnification maps: the breaking of the mass-sheet degeneracy when estimating masses of shear-detected clusters, and constraining the second-order corrections to weak lensing observables.

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New Matter Effects and BBN Constraints for Mass Varying Neutrinos

Authors: Neal Weiner (CCPP, NYU), Kathryn Zurek (INT, UW)
Categories: hep-ph
Comments: 6 pages
Report-no: INT-PUB 05-21

The presence of light (m_a ~ 10^-6 ev) scalar fields in the early universe can modify the cosmology of neutrinos considerably by allowing their masses to vary on cosmological times. In this paper, we consider the effect of Planck-suppressed couplings of this scalar to electrons and show that such couplings can easily make new sterile states thermally inaccessible in the early universe, preserving the successes of big bang nucleosynthesis predictions. We consider the circumstances under which these effects give the proper initial conditions for recently considered models of neutrino dark energy, and consider limits from tests of the equivalence principle. The parameters which satisfy cosmological constraints naturally give rise to interesting signals in terrestrial neutrino oscillation experiments.

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Cluster Merger Variance and the Luminosity Gap Statistic

Authors: Milos Milosavljevic (Caltech), Christopher J. Miller (CTIO), Steven R. Furlanetto (Caltech), Asantha Cooray (UC Irvine)
Categories: astro-ph
Comments: 5 pages, 3 figures

The presence of multiple luminous galaxies in clusters can be explained by the finite time over which a galaxy sinks to the center of the cluster and merges with the the central galaxy. The simplest measurable statistic to quantify the dynamical age of a system of galaxies is the luminosity (magnitude) gap, which is the difference in photometric magnitude between the two most luminous galaxies. We present a simple analytical estimate of the luminosity gap distribution in groups and clusters as a function of dark matter halo mass. The luminosity gap is used to define "fossil" groups; we expect the fraction of fossil systems to exhibit a strong and model-independent trend with mass: ~1-3% of massive clusters and ~5-40% of groups should be fossil systems. We also show that, on cluster scales, the observed intrinsic scatter in the central galaxy luminosity-halo mass relation can be ascribed to dispersion in the merger histories of satellites within the cluster. We compare our predictions to the luminosity gap distribution in a sample of 730 clusters in the Sloan Digital Sky Survey C4 Catalog and find good agreement. This suggests that theoretical excursion set merger probabilities and the standard theory of dynamical segregation are valid on cluster scales.

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