scholarly journals Contribution of pulsars to cosmic-ray positrons in light of recent observation of inverse-Compton halos

2020 ◽  
Vol 102 (2) ◽  
Author(s):  
Silvia Manconi ◽  
Mattia Di Mauro ◽  
Fiorenza Donato
Keyword(s):  
Recent Observation ◽  
Cosmic Ray ◽  
Inverse Compton

scholarly journals The role of radiolysis in the modelling of C2H4O2 isomers and dimethyl ether in cold dark clouds

2020 ◽  
Vol 500 (3) ◽  
pp. 3414-3424
Author(s):  
Alec Paulive ◽  
Christopher N Shingledecker ◽  
Eric Herbst
Keyword(s):  
Gas Phase ◽  
Dimethyl Ether ◽  
Recent Observation ◽  
Cosmic Ray ◽  
Thermal Method ◽  
Dark Clouds ◽  
Ice Surface ◽  
Dust Grain ◽  
Complex Organic

ABSTRACT Complex organic molecules (COMs) have been detected in a variety of interstellar sources. The abundances of these COMs in warming sources can be explained by syntheses linked to increasing temperatures and densities, allowing quasi-thermal chemical reactions to occur rapidly enough to produce observable amounts of COMs, both in the gas phase, and upon dust grain ice mantles. The COMs produced on grains then become gaseous as the temperature increases sufficiently to allow their thermal desorption. The recent observation of gaseous COMs in cold sources has not been fully explained by these gas-phase and dust grain production routes. Radiolysis chemistry is a possible non-thermal method of producing COMs in cold dark clouds. This new method greatly increases the modelled abundance of selected COMs upon the ice surface and within the ice mantle due to excitation and ionization events from cosmic ray bombardment. We examine the effect of radiolysis on three C2H4O2 isomers – methyl formate (HCOOCH3), glycolaldehyde (HCOCH2OH), and acetic acid (CH3COOH) – and a chemically similar molecule, dimethyl ether (CH3OCH3), in cold dark clouds. We then compare our modelled gaseous abundances with observed abundances in TMC-1, L1689B, and B1-b.

scholarly journals Recent Results from the CANGAROO Project

1996 ◽  
Vol 160 ◽  
pp. 363-364
Author(s):  
S.A. Dazeley ◽  
P.G. Edwards ◽  
J.R. Patterson ◽  
G.P. Rowell ◽  
M. Sinnott ◽  
...  
Keyword(s):  
Gamma Rays ◽  
South Australia ◽  
Cosmic Ray ◽  
High Energy ◽  
Relativistic Electrons ◽  
Large Numbers ◽  
Inverse Compton ◽  
Very High Energy ◽  
Large Telescopes ◽  
Very High

TheCollaboration ofAustralia andNippon for aGAmmaRayObservatory in theOutback operates two large telescopes at Woomera (South Australia), which detect the Čerenkov light images produced in the atmosphere by electronpositron cascades initiated by very high energy (~1 TeV or 1012eV) gamma rays. These gamma rays arise from a different mechanism than at EGRET energies: inverse Compton (IC) emission from relativistic electrons.The spoke-like images are recorded by a multi-pixel camera which facilitates the rejection of the large numbers of oblique and ragged cosmic ray images. A field of view ~3.5° is required. The Australian team operates a triple 4 m diameter mirror telescope, BIGRAT, with a 37 photomultiplier tube camera and energy threshold 600 GeV. The Japanese operate a single, highly accurate 3.8 m diameter f/1 telescope and high resolution 256 photomultipler tube camera. In 1998 a new 7 m telescope is planned for Woomera with a design threshold ~;200GeV.

scholarly journals A MODEL-INDEPENDENT METHOD TO STUDY DARK MATTER INDUCED LEPTONS AND GAMMA RAYS

2012 ◽  
Vol 27 (35) ◽  
pp. 1250206 ◽  
Author(s):  
MINGXING LUO ◽  
LIUCHENG WANG ◽  
GUOHUAI ZHU
Keyword(s):  
Dark Matter ◽  
Compton Scattering ◽  
Gamma Rays ◽  
Particle Physics ◽  
Cosmic Ray ◽  
Propagation Model ◽  
Strong Constraint ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Model Independent

By using recent data, we directly determine the dark matter (DM)-induced e± spectrum at the source from experimental measurements at the earth, without reference to specific particle physics models. The DM-induced gamma rays emitted via inverse Compton scattering are then obtained in a model-independent way. However, the results depend on the choice of the astrophysical e± background, which is not reliably known. Nevertheless, we calculate, as an illustration, the fluxes of gamma rays from the Fornax cluster in the decaying DM scenario with various astrophysical e± backgrounds. Without any assumptions on details of the DM model, the predictions turn out to be either in disagreement with or only marginally below the upper limits measured recently by the Fermi-LAT Collaboration. In addition, these DM-induced ICS gamma rays in the GeV range are shown to be almost independent of choices of cosmic ray propagation model and of DM density profile, when a given astrophysical e± background is assumed. This provides a strong constraint on decaying DM scenario as the gamma rays may be produced in other processes besides inverse Compton scattering, such as the bremsstrahlung and neutral pion decays.

Can Galactic γ-Ray Background be due to Superposition of γ-Rays from Millisecond Pulsars?

1998 ◽  
Vol 188 ◽  
pp. 273-274
Author(s):  
V.B. Bhatia ◽  
S. Mishra ◽  
N. Panchapakesan
Keyword(s):  
Cosmic Rays ◽  
Cosmic Ray ◽  
Diffuse Radiation ◽  
High Energy ◽  
Molecular Gas ◽  
Inverse Compton Scattering ◽  
High Energy Electrons ◽  
Inverse Compton ◽  
Γ Rays ◽  
Γ Ray

The SAS 2 and COS B observations have established the existence of diffuse γ-rays in our Galaxy in various energy ranges. The diffuse radiation is attributed to the interaction of cosmic ray nuclei and electrons with the particles of interstellar atomic and molecular gas (via the decay of pions and bremsstrahlung, respectively). Inverse Compton scattering of interstellar photons by the high energy electrons of cosmic rays may also be contributing to this background. In addition some contribution may come from discrete sources of γ-rays.

scholarly journals Pulsars and Bubble Dynamics

1997 ◽  
Vol 166 ◽  
pp. 223-226
Author(s):  
Ramen Kumar Parui
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Bubble Dynamics ◽  
Recent Observation ◽  
Cosmic Ray ◽  
Activity Period ◽  
Cycle Period ◽  
Cosmic Ray Intensity

AbstractBased on recent observation of the dominance of the flare generated solar wind streams over the co-rotating streams and a significant lowering in the cosmic ray intensity in the abnormal year of the solar activity period, I have predicted the occurrence of discernible changes in magnetic field strength and the thickness of the shell of the local bubble during high sunspots years of the solar cycle period. In order to observe the variation, both in the magnetic field strength and in the thickness of the compressed shell, a proposal of continuous monitor of these two parameters through the observation of Faraday Rotation Measure has been proposed with an emphasize to the observations in the period of next abnormal year of the solar cycle in near future.

scholarly journals High Energy Radiation Generated at Boundary Shear Layers of Relativistic Jets

2002 ◽  
Vol 19 (1) ◽  
pp. 22-25 ◽  
Author(s):  
Ł. Stawarz ◽  
M. Ostrowski
Keyword(s):  
Electron Distribution ◽  
Low Frequency ◽  
Cosmic Ray ◽  
High Energy ◽  
Particle Energy ◽  
Relativistic Electrons ◽  
Microwave Background ◽  
Boundary Shear ◽  
Inverse Compton ◽  
Energy Gains

AbstractA simple model of cosmic ray electron acceleration at the jet boundary yields a power law particle energy distribution of ultra-relativistic electrons with an energy cut-off growing with time, and, finally, a growing particle bump at the energy where energy gains equal radiation losses. For such electron distribution, in tens-of-kpc scale jets, we derived the observed time-varying spectra of synchrotron and inverse Compton radiation, including Comptonisation of synchrotron and cosmic microwave background photons. Slowly varying spectral index along the jet in the ‘low frequency’ spectral range is a natural consequence of boundary layer acceleration. Variations of the high energy bump of the electron distribution can give rise to anomalous behaviour in the X-ray band in comparison to the lower frequencies.

scholarly journals Fitting electron spectrum from AMS-02 by pulsar electrons

2021 ◽  
Vol 2145 (1) ◽  
pp. 012003
Author(s):  
Kritaporn Butsaracom ◽  
Brandon Khan Cantlay ◽  
Maneenate Wechakama
Keyword(s):  
Cosmic Ray ◽  
Total Spin ◽  
Short Length ◽  
Propagation Model ◽  
Background Model ◽  
Secondary Electrons ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Electron Propagation ◽  
The Magnetic Field

Abstract In this work, we aim to explain the latest data of cosmic-ray electrons from AMS-02 by an electron background model and pulsar electrons. We consider an electron background model which includes primary and secondary electrons. We assume that pulsars are major sources of the electron excess. Since electrons easily lose their energy through the interstellar radiation field and the magnetic field via inverse Compton scattering and synchrotron radiation, respectively, they propagate in a short length. We adopt nearby pulsar data in the distance of 1 kpc from the Australia Telescope National Facility (ATNF) pulsar catalogue. By using a Green’s function of an electron propagation model, we then fit pulsar parameters (i.e. the spectral index, the fraction of the total spin-down energy and the cutoff energy) for several cases of a single pulsar. With a combination of the electron background model, several cases of pulsar spectrum are able to explain the electron excess.

scholarly journals Calibrating the relation of low-frequency radio continuum to star formation rate at 1 kpc scale with LOFAR

2019 ◽  
Vol 622 ◽  
pp. A8 ◽  
Author(s):  
V. Heesen ◽  
E. Buie II ◽  
C. J. Huff ◽  
L. A. Perez ◽  
J. G. Woolsey ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Low Frequency ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Gaussian Kernel ◽  
Spatially Resolved ◽  
Sky Survey ◽  
Inverse Compton ◽  
Far Ultraviolet

Context. Radio continuum (RC) emission in galaxies allows us to measure star formation rates (SFRs) unaffected by extinction due to dust, of which the low-frequency part is uncontaminated from thermal (free–free) emission. Aims. We calibrate the conversion from the spatially resolved 140 MHz RC emission to the SFR surface density (ΣSFR) at 1 kpc scale. Radio spectral indices give us, by means of spectral ageing, a handle on the transport of cosmic rays using the electrons as a proxy for GeV nuclei. Methods. We used recent observations of three galaxies (NGC 3184, 4736, and 5055) from the LOFAR Two-metre Sky Survey (LoTSS), and archival LOw-Frequency ARray (LOFAR) data of NGC 5194. Maps were created with the facet calibration technique and converted to radio ΣSFR maps using the Condon relation. We compared these maps with hybrid ΣSFR maps from a combination of GALEX far-ultraviolet and Spitzer 24 μm data using plots tracing the relation at the highest angular resolution allowed by our data at 1.2 × 1.2 kpc2 resolution. Results. The RC emission is smoothed with respect to the hybrid ΣSFR owing to the transport of cosmic-ray electrons (CREs) away from star formation sites. This results in a sublinear relation (ΣSFR)RC ∝ [(ΣSFR)hyb]a, where a = 0.59 ± 0.13 (140 MHz) and a = 0.75 ± 0.10 (1365 MHz). Both relations have a scatter of σ = 0.3 dex. If we restrict ourselves to areas of young CREs (α >  −0.65; Iν ∝ να), the relation becomes almost linear at both frequencies with a ≈ 0.9 and a reduced scatter of σ = 0.2 dex. We then simulate the effect of CRE transport by convolving the hybrid ΣSFR maps with a Gaussian kernel until the RC–SFR relation is linearised; CRE transport lengths are l = 1–5 kpc. Solving the CRE diffusion equation, assuming dominance of the synchrotron and inverse-Compton losses, we find diffusion coefficients of D = (0.13–1.5)  × 1028 cm2 s−1 at 1 GeV. Conclusions. A RC–SFR relation at 1.4 GHz can be exploited to measure SFRs at redshift z ≈ 10 using 140 MHz observations.

Distribution and lifetime of cosmic-ray electrons in the galaxy

1968 ◽  
Vol 46 (10) ◽  
pp. S536-S538 ◽  
Author(s):  
Y. Tanaka
Keyword(s):  
Storage Time ◽  
Loss Rate ◽  
Cosmic Ray ◽  
Critical Energy ◽  
Compton Effect ◽  
Source Spectrum ◽  
Inverse Compton Effect ◽  
Inverse Compton ◽  
The Galaxy ◽  
Equilibrium Spectrum

When the source spectrum of cosmic-ray electrons has the form E−γ, the equilibrium spectrum is expected to approach E−γ−1 above a critical energy Ec, where Ec is a function of the storage time and the energy loss rate due to synchrotron radiation and the inverse Compton effect. The observed electron spectrum, which is a combination of the latest results of the Minnesota group, Chicago group, Bombay group, and Leiden group, can be well expressed by a single power law (~E−2.5) for 3 < E < 100 GeV. A knee observed at about 3 GeV might also be due to a solar effect.Thus the possibilities are either [Formula: see text] or Ec > 50 GeV. These two cases lead to largely different models with respect to the source spectrum, the acceleration, the storage time, and the distribution of cosmic-ray electrons in the galaxy. The radio observations are compatible with the hypothesis based on [Formula: see text].

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