Status and Perspectives of Dark Matter Searches in China

In this paper, we give a review of direct detection searches reported by the DAMA (China as a Co-I), and indirect detection searches reported by the ATIC (China as a Co-I). We also outline the future plans of dark matter search in China.      

Astrophysical motivation for X-ray polarimetry

In this paper I will review the motivation for measuring polarization in the X-ray band from astrophysical sources. Emission models designed to reproduce X-ray spectra can be tested using polarization, and polarization detected in other wavelength bands makes clear predictions as to the X-ray polarization. Polarization is a powerful tool to infer geometrical properties of sources which are too small to be spatially resolved. At the same time, there has been recent progress in instrumentation which is likely to allow searches for X-ray polarization at levels significantly below what was possible for early detectors. This paper will review the history of X-ray polarimetry, discuss some experimental techniques and the scientific problems which can be addressed by future experiments.     

Antideuteron based dark matter search with GAPS: Current progress and future prospects

The General Antiparticle Spectrometer (GAPS) is a new approach to the indirect detection of dark matter. It relies on searching for primary antideuterons produced in the annihilation of dark matter in the galactic halo. Low energy antideuterons produced through Standard Model processes, such as collisions of cosmic-rays with interstellar baryons, are greatly suppressed compared to primary antideuterons. Thus a low energy antideuteron search provides a clean signature of dark matter. In GAPS antiparticles are slowed down and captured in target atoms. The resultant exotic atom deexcites with the emission of X-rays and annihilation pions, protons and other particles. A tracking geometry allows for the detection of the X-rays and particles, providing a unique signature to identify the mass of the antiparticle. A prototype detector was successfully tested at the KEK accelerator in 2005, and a prototype GAPS balloon flight is scheduled for 2011. This will be followed by a full scale experiment on a long duration balloon from Antarctica in 2014. We discuss the status and future plans for GAPS.     

Dark matter and dark matter candidates

The nature and identity of the dark matter of the Universe is one of the most challenging problems facing modern cosmology. Only 5% of the energy density of the Universe can be associated with known forms of matter. Problems for baryonic and neutrino dark matter imply the necessity to search beyond the standard model for dark matter candidates. Emphasis is placed on the prospects for supersymmetric dark matter.     

Antideuterons as an indirect dark matter signature: Si(Li) detector development and a GAPS balloon mission

The General AntiParticle Spectrometer (GAPS) is a novel approach for indirect dark matter searches that exploits cosmic antideuterons. GAPS complements existing and planned direct dark matter searches as well as other indirect techniques, probing a different and unique region of parameter space in a variety of proposed dark matter models. The GAPS method involves capturing antiparticles into a target material with the subsequent formation of an excited exotic atom. The exotic atom decays with the emission of atomic X-rays and pions from the nuclear annihilation, which uniquely identifies the captured antiparticle. This technique has been verified through the accelerator testing at KEK in 2004 and 2005. The prototype flight is scheduled from Hokkaido, Japan in 2011, preparatory for a long duration balloon flight from the Antarctic in 2014.     

Anomalous particle transport in the heliosphere

The transport of energetic particles in the presence of magnetic turbulence can exhibit a variety of regimes different from the standard quasilinear diffusion. Here we discuss a number of solar and space problems where nonquasilinear diffusion is found, and then we illustrate anomalous transport regimes, for which the mean square deviation grows nonlinearly with time. In particular, we concentrate on superdiffusive regimes, and show what is the theoretical framework which is to be used to describe superdiffusion. We discuss the results of numerical simulations which show that superdiffusive and subdiffusive regimes are possible, and describe data analyses which allow to single out the superdiffusive transport from the observation of energetic particle profiles upstream of interplanetary shocks. The implications of superdiffusion on the efficiency of wave particle interactions are also discussed.     

Velocity distribution of elliptical galaxies in the framework of Non-local Gravity model

We investigate the velocity distribution of elliptical galaxies in the framework of Non-local Gravity. According to this approach, it is possible to recover the fundamental plane of elliptical galaxies without the dark matter hypothesis. Specifically, we compare theoretical predictions for circular velocity in Non-local Gravity context with the corresponding values coming from a large sample of observed elliptical galaxies. We adopt the surface brightness, effective radius and velocity dispersion as structural parameters for the fundamental plane. As final result, it is possible to show that non-local gravity effects can reproduce the stellar dynamics in elliptical galaxies and fit consistently observational data.     

Improving the angular resolution of EGRET and new limits on supersymmetric dark matter near the galactic center

Using the EGRET data and an improved point source analysis, including an energy-dependent point spread function and an unbinned maximum likelihood technique, we have been able to place considerably lower limits on the γ-ray flux from the galactic center region. We also test this method on known sources, the Crab and Vela pulsars. In both cases, we find that our method improves the angular precision of EGRET data over the 3EG catalog.This new limit on γ-rays from the galactic center can be used to test models of annihilating supersymmetric dark matter and galactic halo profiles. We find that the present EGRET data can limit many supersymmetric models if the density of the galactic dark matter halo is cuspy or spiked toward the galactic center. We also discuss the ability of GLAST to test these models.     

Detecting gravitational waves from accreting neutron stars

The gravitational waves emitted by neutron stars carry unique information about their structure and composition. Direct detection of these gravitational waves, however, is a formidable technical challenge. In a recent study we quantified the hurdles facing searches for gravitational waves from the known accreting neutron stars, given the level of uncertainty that exists regarding spin and orbital parameters. In this paper we reflect on our conclusions, and issue an open challenge to the theoretical community to consider how searches should be designed to yield the most astrophysically interesting upper limits. With this in mind we examine some more optimistic emission scenarios involving spin-down, and show that there are technically feasible searches, particularly for the accreting millisecond pulsars, that might place meaningful constraints on torque mechanisms. We finish with a brief discussion of prospects for indirect detection.     

The structure and dynamics of the Jovian energetic particle distribution

We review the recent progress made in unravelling the properties of the energetic particle population in the magnetosphere of Jupiter. The importance of the findings with respect to mechanisms driving the dynamics of the Jovian system is addressed. We concentrate on the implications of phase space density variations for particle loss and source mechanism. Systematic local time and radial dependencies observed in the characteristics of the energetic ion and electron distributions, specifically the particle pitch angle distributions and particle flow pattern are discussed. They possibly bear important information for disentangling those mechanisms responsible for driving the Jovian aurora and for identifying the magnetospheric source populations. Furthermore, we discuss transient particle events in the tail which point to the importance of reconnection for the tail dynamics.     

X-ray measurements of the dark matter distribution in clusters of galaxies with Chandra

We investigate the dark matter distributions in the central region of two clusters of galaxies (A1835 and MKW3S) using Chandra data. N-body simulations in the standard cold dark matter (CDM) model predict the dark matter distribution shows a cuspy dark matter profile: ρ(r) ∝ r, with in the range 1–2, while observations of dwarf and low surface brightness galaxies seem to favor the presence of a relatively flat core: 0 <  < 1. To investigate the dark matter distributions in the central region of clusters of galaxies, we analyze the Chandra data of A1835 and MKW3S with a deprojection method. We derive the mass profiles without the assumption of analytical models. We examine the inner slope of derived mass profiles assuming the dark matter profile is described with a power-law expression. The values of the slope are 0.95 ± 0.10 for A1835 and 1.33 ± 0.12 for MKW3S within the radius of 200 kpc. These are consistent with the result of the CDM simulations. However, within the radius of 100 kpc, the value of is less than unity for A1835 (0.47 ± 0.31). Our result implies that the central dark matter profile of some clusters cannot be described by CDM halos.     

Fault detection and isolation in GPS receiver autonomous integrity monitoring based on chaos particle swarm optimization-particle filter algorithm

The receiver autonomous integrity monitoring (RAIM) is one of the most important parts in an avionic navigation system. Two problems need to be addressed to improve this system, namely, the degeneracy phenomenon and lack of samples for the standard particle filter (PF). However, the number of samples cannot adequately express the real distribution of the probability density function (i.e., sample impoverishment). This study presents a GPS receiver autonomous integrity monitoring (RAIM) method based on a chaos particle swarm optimization particle filter (CPSO-PF) algorithm with a log likelihood ratio. The chaos sequence generates a set of chaotic variables, which are mapped to the interval of optimization variables to improve particle quality. This chaos perturbation overcomes the potential for the search to become trapped in a local optimum in the particle swarm optimization (PSO) algorithm. Test statistics are configured based on a likelihood ratio, and satellite fault detection is then conducted by checking the consistency between the state estimate of the main PF and those of the auxiliary PFs. Based on GPS data, the experimental results demonstrate that the proposed algorithm can effectively detect and isolate satellite faults under conditions of non-Gaussian measurement noise. Moreover, the performance of the proposed novel method is better than that of RAIM based on the PF or PSO-PF algorithm.     

Review on latest progress on supergiant fast X-ray transients and future direction

In the recent years, the discovery of a new class of Galactic transients with fast and bright flaring X-ray activity, the supergiant fast X-ray transients, has completely changed our view and comprehension of massive X-ray binaries. These objects display X-ray outbursts which are difficult to be explained in the framework of standard theories for the accretion of matter onto compact objects, and could represent a dominant population of X-ray binaries. I will review their main observational properties (neutron star magnetic field, orbital and spin period, long term behavior, duty cycle, quiescence and outburst emission), which pose serious problems to the main mechanisms recently proposed to explain their X-ray behavior. I will discuss both present results and future perspectives with the next generation of X-ray telescopes.     

Current status and future plans for the general antiparticle spectrometer (GAPS)

We discuss current progress and future plans for the general antiparticle spectrometer experiment (GAPS). GAPS detects antideuterons through the X-rays and pions emitted during the deexcitation of exotic atoms formed when the antideuterons are slowed down and stopped in targets. GAPS provides an exceptionally sensitive means to detect cosmic-ray antideuterons. Cosmic-ray antideuterons can provide indirect evidence for the existence of dark matter in such form as neutralinos or Kaluza–Klein particles. We describe results of accelerator testing of GAPS prototypes, tentative design concepts for a flight GAPS detector, and near-term plans for flying a GAPS prototype on a balloon.     

Dark energy,co-evolution of massive black holes with galaxies,and ASTROD-GW

The detection of low frequency band (100 nHz–100 mHz) and very low frequency band (300 pHz–100 nHz) gravitational waves (GWs) is important for exploration of the equation of state of dark energy and the co-evolution of massive black holes (MBHs) with galaxies. Most galaxies are believed to have a massive black hole in the galactic core. In the formation of these black holes, merging and accretion are the two main processes. Merging of massive black holes generate GWs which could be detected by space GW detectors and Pulsar Timing Arrays (PTAs) to cosmological distances. LISA (Laser-Interferometric Space Antenna) is most sensitive to the frequency band 1 mHz–100 mHz, ASTROD-GW (ASTROD [Astrodynamical Space Test of Relativity using Optical Devices] optimized for Gravitational Wave detection) is most sensitive to the frequency band 100 nHz–1 mHz and PTAs are most sensitive to the frequency band 300 pHz–100 nHz. In this paper, we discuss the sensitivities and outlooks of detection of GWs from binary massive black holes in these frequency bands with an emphasis on ASTROD-GW. The GWs generated by the inspirals, merging and subsequent ringdowns of binary black holes are standard sirens to the cosmological distance. Using GW observations, we discuss the methods for determining the equation of state of dark energy and for testing the co-evolution models of massive black holes. ASTROD-GW is an optimization of ASTROD to focus on the goal of detection of GWs. The mission orbits of the 3 spacecraft forming a nearly equilateral triangular array are chosen to be near the Sun-Earth Lagrange points L3, L4 and L5. The 3 spacecraft range interferometrically with one another with arm length about 260 million kilometers. With 52 times longer in arm length compared to that of LISA, the strain detection sensitivity is 52 times better toward larger wavelength. The scientific aim is focused for gravitational wave detection at low frequency. The science goals include detection of GWs from MBHs, and Extreme-Mass-Ratio Black Hole Inspirals (EMRI), and using these observations to find the evolution of the equation of state of dark energy and to explore the co-evolution of massive black holes with galaxies.     

A census of high-energy observations of Galactic supernova remnants

We present the first public database of high-energy observations of all known Galactic supernova remnants (SNRs). In Section 1 we introduce the rationale for this work motivated primarily by studying particle acceleration in SNRs, and which aims at bridging the already existing census of Galactic SNRs (primarily made at radio wavelengths) with the ever-growing but diverse observations of these objects at high-energies (in the X-ray and γ$\gamma$-ray regimes). In Section 2 we show how users can browse the database using a dedicated web front–end (http://www.physics.umanitoba.ca/snr/SNRcat). In Section 3 we give some basic statistics about the records we have collected so far, which provides a summary of our current view of Galactic SNRs. Finally, in Section 4, we discuss some possible extensions of this work. We believe that this catalogue will be useful to both observers and theorists, and timely with the synergy in radio/high-energy SNR studies as well as the upcoming new high-energy missions. A feedback form provided on the website will allow users to provide comments or input, thus helping us keep the database up-to-date with the latest observations.     

基于天基光学探测图像初析南大西洋异常区影响

文章针对目前在轨运行的高灵敏度探测类可见光遥感器经过南大西洋异常区（SouthAtlanticAnomaly,SAA）时出现的探测能力降低、目标无法识别等现象,通过卫星在轨获取的SAA天基探测图像研究图像中出现的异常现象机理;提出了基于CCD探测器固有暗像元区的图像特征变化开展SAA影响评估的方法,根据在轨图像暗像元区的均值和标准差、图像区的热像素及活像元等特征参数的统计分析,判断经过SAA过程中连续获取的图像中出现显著影响时的拐点,通过曲线拟合估算出该轨道高度的SAA空间分布特征和边界,依此进一步提出利用在轨天基探测图像给出测量影响该轨道高度卫星SAA区域边界的简单方法;最后,基于SAA对天基探测器件的影响分析结果和认识,给出了高灵敏度探测类卫星避免或消除SAA影响的改进措施和建议。文章采用的数据分析和评估方法为提升SAA对天基探测影响的认识,以及下一步有效开展空间碎片探测工作提供参考。     

Multiwavelength spectral models for SNR G347.3-0.5 from non-linear shock acceleration

The remnant G347.3-0.5 exhibits strong shell emission in the radio and X-ray bands, and has a purported detection in the TeV gamma-ray band by the CANGAROO-II telescope. The CANGAROO results were touted as evidence for the production of cosmic ray ions, a claim that has proven controversial due to constraining fluxes associated with a proximate unidentified EGRET source 3EG J1714-3857. HESS has now seen this source in the TeV band. The complex environment of the remnant renders modeling of its broadband spectrum sensitive to assumptions concerning the nature and parameters of the circumremnant medium. This paper explores a sampling of reasonable possibilities for multiwavelength spectral predictions from this source, using a non-linear model of diffusive particle acceleration at the shocked shell. The magnetic field strength, shell size and degree of particle cross-field diffusion act as variables to which the radio to X-ray to gamma-ray signal is sensitive. The modeling of the extant data constrains these variables, and the potential impact of the recent HESS detection on such parameters is addressed. Putative pion decay signals in hard gamma-rays resulting from hadronic interactions in dense molecular clouds are briefly discussed; the requisite suppression of the GeV component needed to accommodate the 3EG J1714-3857 EGRET data provides potential bounds on the diffusive distance from the shell to the proximate clouds.     

Clump-driven galaxy evolution and quasar activity

The collapse of a protogalaxy composed of dark matter and primordial gas has been investigated by numerical simulations and analytical multi-zone modelling in an attempt to examine the early evolution of disk galaxies. The importance of ample interstellar matter existing in young galactic disks has been highlighted. Confrontation of the theoretical results with the available observational data has led to a new picture for disk galaxy evolution, in which the bulge is the secondary object formed from disk matter. Occurrence of quasar activity is also discussed in relation to the dynamical evolution of the host galaxy.     

Cosmic-ray antiprotons in the galaxy

A key issue in fundamental physics is the nature of non-baryonic dark matter in the universe. Among the candidates proposed by the particle physics community are neutralinos whose annihilation in the Galactic halo can produce antiprotons with a characteristic spectrum. Several balloon and space borne experiments have been actively looking to detect the neutralino signature in cosmic antiprotons. This task is however hampered by the existence of a secondary “background” flux of antiprotons produced in the interactions of cosmic-ray particles in the interstellar medium. A notable difficulty is that a self-consistent and complete model of cosmic-ray propagation in the Galaxy has thus far been elusive. When subtracting the secondary background from the observed data, it is therefore critical that all viable models of secondary cosmic-ray antiproton propagation be thoroughly examined, and all uncertainties stemming from plurality of the models be duly considered. In this paper we concentrate on three particular models of Diffusion, Galactic Wind, and Distributed Stochastic Reacceleration, and discuss the predicted antiproton spectrum in each model.