Alignment of spiral galaxies in the local supercluster

Evidence is presented indicating the non-random alignment of spiral galaxies in the Local Supercluster. The form of this effect is such that the spin angular momentum vectors of intermediate-type spirals are coherently aligned in space. The results suggest the formation of galaxies in the Local Supercluster according to the fragmentation hypothesis.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Correlation properties of the galaxies in the Local Supercluster

The apparatus of a correlation gamma function is used to analyze the spatial clustering of galaxies in the Local Supercluster. In particular, we analyzed a sample corrected for the peculiar velocities of the Local Supercluster galaxies by using our original technique for separating groups of galaxies. It turned out that the peculiar velocities did not significantly distort the gamma function even for relatively small sample sizes. The distribution of the galaxies obeys a power-law decrease in density with an index of 0.6–0.7. We found evidence for a luminosity dependence of the degree of galaxy clustering within the volume under study.     

Cosmic rays from remnants of quasars?

Considerations of the collision losses for protons traversing the 2.7-K blackbody microwave radiation field have led to the conclusion that the highest energy cosmic rays, those observed at ≥10²⁰ eV, must come from sources within the present epoch. In light of this constraint, it is here suggested that these particles may be accelerated near the event horizons of spinning supermassive black holes associated with presently inactive quasar remnants. The required emf is generated by the black hole induced rotation of externally supplied magnetic field lines threading the horizon. Producing the observed flux of the highest energy cosmic rays would constitute a negligible drain on the black hole dynamo. Observations with upcoming air shower arrays and space missions may lead to the identification of candidate dormant galaxies that harbour such black holes. Although the highest energy events observed so far are accounted for within the context of this scenario, a spectral upper bound at ∼10²¹ eV is expected since the acceleration to higher energies appears to be precluded, on general grounds.     

Neutrino initiated cascades at mid and high altitudes in the atmosphere

High energy neutrinos play a very important role for the understanding of the origin and propagation of ultra high energy cosmic rays (UHECR). They can be produced as a consequence of the hadronic interactions suffered by the cosmic rays in the acceleration regions, as by products of the propagation of the UHECR in the radiation background and as a main product of the decay of super heavy relic particles. A new era of very large exposure space observatories, of which the JEM-EUSO mission is a prime example, is on the horizon which opens the possibility of neutrino detection in the highest energy region of the spectrum. In the present work we use a combination of the PYTHIA interaction code with the CONEX shower simulation package in order to produce fast one-dimensional simulations of neutrino initiated showers in air. We make a detail study of the structure of the corresponding longitudinal profiles, but focus our physical analysis mainly on the development of showers at mid and high altitudes, where they can be an interesting target for space fluorescence observatories.     

The extragalactic neutrino background radiations from blazars and cosmic rays

Blazar emission of gamma rays and cosmic ray production of gamma rays in gas-rich clusters have been proposed recently as alternative sources of the high energy extragalactic diffuse gamma ray background radiation. We show that these sources also produce very different high energy extragalactic diffuse neutrino background radiations. An extragalactic neutrino background radiation may be detected by the new generation of large neutrino telescopes under construction and may be used to trace the origin of the extragalactic gamma radiation.     

基于暗物质粒子探测卫星的宇宙线直接探测研究

高能宇宙线的起源、加速和传播是重大的前沿科学问题,回答该问题需要对宇宙线的能谱、各向异性以及各类高能天体电磁辐射进行精确观测.通过空间粒子探测器对宇宙线各成分能谱的直接测量是研究宇宙线物理问题的重要手段.中国于2015年底发射并持续运行至今的暗物质粒子探测卫星以其大接受度、高能量分辨率等特点,在宇宙线直接探测方面取得了系列重要成果,揭示出质子、氦核、硼碳和硼氧比例等宇宙线能谱的新结构,为理解宇宙线起源等科学问题提供了新的依据.介绍了暗物质粒子探测卫星的仪器设置、运行状况、科学成果及其物理意义.     

Broad-band non-thermal emission from molecular clouds illuminated by cosmic rays from nearby supernova remnants

Molecular clouds are expected to emit non-thermal radiation due to cosmic ray interactions in the dense magnetized gas. Such emission is amplified if a cloud is located close to an accelerator of cosmic rays and if energetic particles can leave the accelerator site and diffusively reach the cloud. We consider here a situation in which a molecular cloud is located in the proximity of a supernova remnant which is efficiently accelerating cosmic rays and gradually releasing them in the interstellar medium. We calculate the multiwavelength spectrum from radio to gamma rays which is emerging from the cloud as the result of cosmic ray interactions. The total energy output is dominated by the gamma-ray emission, which can exceed the emission in other bands by an order of magnitude or more. This suggests that some of the unidentified TeV sources detected so far, with no obvious or very weak counterparts in other wavelengths, might be in fact associated with clouds illuminated by cosmic rays coming from a nearby source. Moreover, under certain conditions, the gamma-ray spectrum exhibits a concave shape, being steep at low energies and hard at high energies. This fact might have important implications for the studies of the spectral compatibility of GeV and TeV gamma-ray sources.     

Propagation effects in the hydrogen-to-helium ratio in the solar cosmic rays

Taking as basis my dimensional solution of the propagation equation of solar cosmic rays in interplanetary space and using the equivalent diffusion coefficient found from observed data on solar protons, I discuss the effects of propagation on the hydrogen-to-hellum ratio Including its variation with the speed of the solar wind and with location in space. After eliminating the variations with solar distance and energy from the HEOS and PIONEER data collected by Perron et al., this ratio will be seen to increase with the magnetic longitude of the parent flare. The Initial value of the hydrogen-to-helium ratio at the Sun's surface, obtained after applying the corrections for propagation, is close to the value in the solar wind.     

Distribution of quasars on the sky

It is shown that high-redshift quasars of bright apparent magnitude are concentrated in the direction of the centre of the Local Group of galaxies. A number of them are distributed along a line originating from the Local Group companion galaxy, M 33. A similar, but shorter and fainter line of quasars is seen emanating from the spiral galaxy NGC 300 in the next nearest, Sculptor Group of galaxies. The concentration of bright quasars in the Local Group direction is supported by bright radio sources catalogued in high-frequency surveys. One of the consequences of this large-scale inhomogeneity is to explain the different gradient of radio source counts in the direction of the Local Supercluster, a result discovered in 1978 but never investigated further. Previously reported homogeneity and isotropy of radio-source counts over the sky would seem to be an effect of integrating nearby, large-scale groupings with more distant, smaller-scale groupings over different directions in the sky. More careful analyses as a function of flux strength and spectral index on various scales over the sky are now required. Previous conclusions about radio source and quasar luminosity and number evolution drawn from logN- logS counts would then need to be re-evaluated.     

Are gamma-ray bursts the sources of ultra-high energy cosmic rays?

We reconsider the possibility that gamma-ray bursts (GRBs) are the sources of the ultra-high energy cosmic rays (UHECRs) within the internal shock model, assuming a pure proton composition of the UHECRs. For the first time, we combine the information from gamma-rays, cosmic rays, prompt neutrinos, and cosmogenic neutrinos quantitatively in a joint cosmic ray production and propagation model, and we show that the information on the cosmic energy budget can be obtained as a consequence. In addition to the neutron model, we consider alternative scenarios for the cosmic ray escape from the GRBs, i.e., that cosmic rays can leak from the sources. We find that the dip model, which describes the ankle in UHECR observations by the pair production dip, is strongly disfavored in combination with the internal shock model because (a) unrealistically high baryonic loadings (energy in protons versus energy in electrons/gamma-rays) are needed for the individual GRBs and (b) the prompt neutrino flux easily overshoots the corresponding neutrino bound. On the other hand, GRBs may account for the UHECRs in the ankle transition model if cosmic rays leak out from the source at the highest energies. In that case, we demonstrate that future neutrino observations can efficiently test most of the parameter space – unless the baryonic loading is much larger than previously anticipated.     

Chiral Property of Spiral and Barred Spiral Galaxies in the Local Supercluster

We present an analysis of the chiral property of 667 spiral and barred spiral galaxies in the Local Supercluster (radial velocity <3 000 km s⁻¹). The arms of a galaxy (spiral or barred spiral) can be distinguished according to their orientation (leading or trailing) relative to the direction of the rotation. We use environment of each galaxy as a subsample in order to study the chiral property of galaxies. In addition, equatorial position angle distributions of leading and trailing arm galaxies are studied. We classify our database according as their morphology, diameters, radial velocities, axial ratios and magnitudes. The distribution of trailing and leading arm galaxies in the Local Supercluster is found homogeneous. A significant dominance of either trailing or leading structures is noticed within the Virgo cluster region, suggesting that the aggregation of these structures might have already started there. The rotation axes of the galaxies in the Virgo cluster is found to lie in the equatorial plane. Chirality of galaxies is found strong for the subsamples that showed a random alignment in the equatorial position angle distribution. Possible explanations of the results will be presented.     

Design optimization and background modeling of the HEX experiment on Chandrayaan-I

Spacecraft and their subsystem components are subject to a very hazardous radiation environment in both near-Earth and deep space orbits. Knowledge of the effects of this high energy particle and electromagnetic radiation is essential in designing sensors, electronic circuits and living habitats for humans in near Earth orbit, en route to and on the Moon and Mars. This paper discusses the use of Monte Carlo simulations to optimize system design, radiation source modeling, and determination of background in sensors due to galactic cosmic rays and radiation from the Moon. The results demonstrate the use of Monte Carlo particle transport toolkits to predict secondary production, determine dose rates in space and design required shielding geometry.     

PeV gamma rays from interactions of ultra high energy cosmic rays in the Milky Way

The PeV gamma ray background produced in the interactions of ultra high energy cosmic rays with the ambient matter and radiations during their propagation in the Milky Way has been calculated in this paper. If the primary ultra high energy cosmic rays are produced from Galactic point sources then those point sources are also emitting PeV gamma rays. We discuss that the detection of galactocentric PeV gamma rays in the future would be a signature of the presence of EeV cosmic accelerators in the Milky Way.     

Galactic PeV neutrinos

The IceCube experiment has detected two neutrinos with energies between 1 and 10 PeV. They might have originated from Galactic or extragalactic sources of cosmic rays. In the present work we consider hadronic interactions of the diffuse very high energy cosmic rays with the interstellar matter within our Galaxy to explain the PeV neutrino events detected in IceCube. We also expect PeV gamma ray events along with the PeV neutrino events if the observed PeV neutrinos were produced within our Galaxy in hadronic interactions. PeV gamma rays are unlikely to reach us from sources outside our Galaxy due to pair production with cosmic background radiation fields. We suggest that in future with simultaneous detections of PeV gamma rays and neutrinos it would be possible to distinguish between Galactic and extragalactic origins of very high energy neutrinos.     

Acceleration of charged particles in the magnetosphere of a collapsing star and their nonthermal electromagnetic radiation

We investigate a transformation of a magnetic field and plasma in nonhomogeneous magnetospheres of collapsing stars with a dipole initial magnetic field and certain initial energy distributions of particles in the magnetosphere as the power low, relativistic Maxwell and Boltzmann. The betatron mechanism of the charged particles acceleration in a collapsing star’s magnetosphere is considered. When a magnetized star is compressed in the stage of the gravitational collapse, the magnetic field increases strongly. This variable magnetic field generates a vortical electric field. Our calculations show that this electric field will accelerate charged particles up to relativistic velocities. Thus, collapsing stars may be sources of high energy cosmic rays in our galaxy as in others. The acceleration of particles during the collapse happens mostly in polar regions of the magnetosphere that leads to polar relativistic streams (jets) formation. When moving in a magnetic field, these particles will generate nonthermal electromagnetic radiation in a broad electromagnetic wavelength band from radioto gamma rays. Thus, in the stage of the gravitational collapse, relativistic jets are formed in stellar magnetospheres. These jets are powerful sources of the nonthermal electromagnetic radiation.     

Introduction to Large High Altitude Air Shower Observatory (LHAASO)

Since the century discovery of cosmic ray, the origin of cosmic ray is always a mystery. The study on the origin of high-energy cosmic ray is in an interdiscipline between the very high-energy (VHE) gamma-ray astronomy and the cosmic ray physics. The Large High Altitude Air Shower Observatory (LHAASO) is a unique and new generation cosmic-ray station with the advantages of high altitude, all-weather, and large-scale. It takes the function of hybrid technology to detect cosmic rays and to upgrade greatly the resolving power between gamma rays and cosmic rays. The LHAASO is expected to make the full-sky survey to find new gamma-ray sources, to obtain the highest sensitivity of gamma-ray detection at the high energy band of > 30 TeV, and to make the very high precision measurement on the component energy spectra of cosmic rays in a broad energy range of 5 orders of magnitude, in order to provide the evidence for revealing the mystery of the origin of cosmic ray. This paper describes the detector structure, performance superiority and scientific motivation of the LHAASO.     

AGN Detection Ranges of MACE and TACTIC Imaging Gamma-Ray Telescopes

Two high-sensitivity imaging gamma-ray telescopes, MACE and TACTIC, are being set up at Mt. Abu, India, for making detailed spectral and temporal investigations of galactic and extragalactic gamma-ray sources in the photon energy bands. E 20–200 GeV and 0.5–5TeV respectively. Here, we estimate the effective red-shift ranges of these telescopes for detecting gamma-ray signals from the EGRET-detected AGN's and identify the most likely candidate-sources for detection by the MACE and the TACTIC, under the assumption that the EGRET-inferred power-law spectra for these AGN's extend into the GeV-TeV range without any change in shape. Extremum bounds of the relevant intergalactic background radiation fields, suggested by various observational and theoretical considerations, have been used to estimate the attenuation of VHE gamma-ray fluxes due to photon-photon pair-production process, leading to the desired z-ranges for these instruments.     

The Cherenkov Telescope Array potential for the study of young supernova remnants

Supernova remnants (SNRs) are among the most important targets for γ-ray observatories. Being prominent non-thermal sources, they are very likely responsible for the acceleration of the bulk of Galactic cosmic rays (CRs). To firmly establish the SNR paradigm for the origin of cosmic rays, it should be confirmed that protons are indeed accelerated in, and released from, SNRs with the appropriate flux and spectrum. This can be done by detailed theoretical models which account for microphysics of acceleration and various radiation processes of hadrons and leptons. The current generation of Cherenkov telescopes has insufficient sensitivity to constrain theoretical models. A new facility, the Cherenkov Telescope Array (CTA), will have superior capabilities and may finally resolve this long standing issue of high-energy astrophysics. We want to assess the capabilities of CTA to reveal the physics of various types of SNRs in the initial 2000 years of their evolution. During this time, the efficiency to accelerate cosmic rays is highest. We perform time-dependent simulations of the hydrodynamics, the magnetic fields, the cosmic-ray acceleration, and the non-thermal emission for type Ia, Ic and IIP SNRs. We calculate the CTA response to the γ-ray emission from these SNRs for various ages and distances, and we perform a realistic analysis of the simulated data. We derive distance limits for the detectability and resolvability of these SNR types at several ages. We test the ability of CTA to reconstruct their morphological and spectral parameters as a function of their distance. Finally, we estimate how well CTA data will constrain the theoretical models.     

The Converter Mechanism of Particle Acceleration and Its Applications to the Unidentified Egret Sources

We discuss the properties of gamma-ray radiation accompanying the acceleration of cosmic rays via the converter mechanism. The mechanism exploits multiple photon-induced conversions of high-energy particles from charged into neutral state (namely, protons to neutrons and electrons to photons) and back. Because a particle in the neutral state can freely cross the magnetic field lines, this allows to avoid both particle losses downstream and reduction in the energy gain factor, which normally takes place due to highly collimated distribution of accelerated particles. The converter mechanism efficiently operates in relativistic outflows under the conditions typical for Active Galactic Nuclei, Gamma-Ray Bursts, and microquasars, where it outperforms the standard diffusive shock acceleration. The accompanying radiation has a number of distinctive features, such as an increase of the maximum energy of synchrotron photons and peculiar radiation beam-pattern, whose opening angle is much wider at larger photon energies. This provides an opportunity to observe off-axis relativistic jets in GeV–TeV energy range. One of the implications is the possibility to explain high-latitude unidentified EGRET sources as off-axis but otherwise typical relativistic-jet sources, such as blazars.