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soil moisture dynamics reflect the complex interactions of meteorological conditions with soil, vegetation and terrain properties. in this study, intermediate-scale soil moisture estimates from the cosmic-ray neutron sensing (crns) method are evaluated for two semiarid ecosystems in the southwestern united states: a mesquite savanna at the santa rita experimental range (srer) and a mixed shrubland at the jornada experimental range (jer). evaluations of the crns method are performed for small watersheds instrumented with a distributed sensor network consisting of soil moisture sensor profiles, an eddy covariance tower, and runoff flumes used to close the water balance. we found a very good agreement between the crns method and the distributed sensor network (root mean square error (rmse) of 0.009 and 0.013 m3 m-3 at srer and jer, respectively) at the hourly timescale over the 19-month study period, primarily due to the inclusion of 5 cm observations of shallow soil moisture. good agreement was also obtained in soil moisture changes estimated from the crns and watershed water balance methods (rmse of 0.001 and 0.082 m3 m-3 at srer and jer, respectively), with deviations due to bypassing of the crns measurement depth during large rainfall events. once validated, the crns soil moisture estimates were used to investigate hydrological processes at the footprint scale at each site. through the computation of the water balance, we showed that drier-than-average conditions at srer promoted plant water uptake from deeper soil layers, while the wetter-than-average period at jer resulted in percolation towards deeper soils. the crns measurements were then used to quantify the link between evapotranspiration and soil moisture at a commensurate scale, finding similar predictive relations at both sites that are applicable to other semiarid ecosystems in the southwestern us. | closing the water balance with cosmic-ray soil moisture measurements and assessing their relation to evapotranspiration in two semiarid watersheds |
precise knowledge of the charge and rigidity dependence of the secondary cosmic ray fluxes and the secondary-to-primary flux ratios is essential in the understanding of cosmic ray propagation. we report the properties of heavy secondary cosmic ray fluorine f in the rigidity r range 2.15 gv to 2.9 tv based on 0.29 million events collected by the alpha magnetic spectrometer experiment on the international space station. the fluorine spectrum deviates from a single power law above 200 gv. the heavier secondary-to-primary f/si flux ratio rigidity dependence is distinctly different from the lighter b/o (or b/c) rigidity dependence. in particular, above 10 gv, the f//si b /o ratio can be described by a power law rδ with δ =0.052 ±0.007 . this shows that the propagation properties of heavy cosmic rays, from f to si, are different from those of light cosmic rays, from he to o, and that the secondary cosmic rays have two classes. | properties of heavy secondary fluorine cosmic rays: results from the alpha magnetic spectrometer |
we report the properties of sodium (na) and aluminum (al) cosmic rays in the rigidity range 2.15 gv to 3.0 tv based on 0.46 million sodium and 0.51 million aluminum nuclei collected by the alpha magnetic spectrometer experiment on the international space station. we found that na and al, together with nitrogen (n), belong to a distinct cosmic ray group. in this group, we observe that, similar to the n flux, both the na flux and al flux are well described by the sums of a primary cosmic ray component (proportional to the silicon flux) and a secondary cosmic ray component (proportional to the fluorine flux). the fraction of the primary component increases with rigidity for the n, na, and al fluxes and becomes dominant at the highest rigidities. the na /si and al /si abundance ratios at the source, 0.036 ±0.003 for na /si and 0.103 ±0.004 for al /si , are determined independent of cosmic ray propagation. | properties of a new group of cosmic nuclei: results from the alpha magnetic spectrometer on sodium, aluminum, and nitrogen |
germany's 2018-2020 consecutive drought events resulted in multiple sectors - including agriculture, forestry, water management, energy production, and transport - being impacted. high-resolution information systems are key to preparedness for such extreme drought events. this study evaluates the new setup of the one-kilometer german drought monitor (gdm), which is based on daily soil moisture (sm) simulations from the mesoscale hydrological model (mhm). the simulated sm is compared against a set of diverse observations from single profile measurements, spatially distributed sensor networks, cosmic-ray neutron stations, and lysimeters at 40 sites in germany. our results show that the agreement of simulated and observed sm dynamics in the upper soil (0-25 cm) are especially high in the vegetative active period (0.84 median correlation r) and lower in winter (0.59 median r). the lower agreement in winter results from methodological uncertainties in both simulations and observations. moderate but significant improvements between the coarser 4 km resolution setup and the ≈ 1.2 km resolution gdm in the agreement to observed sm dynamics is observed in autumn (+0.07 median r) and winter (+0.12 median r). both model setups display similar correlations to observations in the dry anomaly spectrum, with higher overall agreement of simulations to observations with a larger spatial footprint. the higher resolution of the second gdm version allows for a more detailed representation of the spatial variability of sm, which is particularly beneficial for local risk assessments. furthermore, the results underline that nationwide drought information systems depend both on appropriate simulations of the water cycle and a broad, high-quality, observational soil moisture database. | high-resolution drought simulations and comparison to soil moisture observations in germany |
radio relics in galaxy clusters are associated with powerful shocks that (re)accelerate relativistic electrons. it is widely believed that the acceleration proceeds via diffusive shock acceleration. in the framework of thermal leakage, the ratio of the energy in relativistic electrons to the energy in relativistic protons should be smaller than ke/p ∼ 10-2. the relativistic protons interact with the thermal gas to produce γ-rays in hadronic interactions. combining observations of radio relics with upper limits from γ-ray observatories can constrain the ratio ke/p. in this work, we selected 10 galaxy clusters that contain double radio relics, and derive new upper limits from the stacking of γ-ray observations by fermi. we modelled the propagation of shocks using a semi-analytical model, where we assumed a simple geometry for shocks and that cosmic ray protons are trapped in the intracluster medium. our analysis shows that diffusive shock acceleration has difficulties in matching simultaneously the observed radio emission and the constraints imposed by fermi, unless the magnetic field in relics is unrealistically large ( ≫ 10 μg). in all investigated cases (also including realistic variations of our basic model and the effect of re-acceleration), the mean emission of the sample is of the order of the stacking limit by fermi, or larger. these findings put tension on the commonly adopted model for the powering of radio relics, and imply that the relative acceleration efficiency of electrons and protons is at odds with predictions of diffusive shock acceleration, requiring ke/p ≥ 10 - 10-2. | electron and proton acceleration efficiency by merger shocks in galaxy clusters |
context. interplanetary coronal mass ejections (icmes) are the interplanetary manifestations of solar eruptions. the overtaken solar wind forms a sheath of compressed plasma at the front of icmes. magnetic clouds (mcs) are a subset of icmes with specific properties (e.g. the presence of a flux rope). when icmes pass near earth, ground observations indicate that the flux of galactic cosmic rays (gcrs) decreases.aims: the main aims of this paper are to find common plasma and magnetic properties of different icme sub-structures and which icme properties affect the flux of gcrs near earth.methods: we used a superposed epoch method applied to a large set of icmes observed in situ by the spacecraft ace, between 1998 and 2006. we also applied a superposed epoch analysis on gcrs time series observed with the mcmurdo neutron monitors.results: we find that slow mcs at 1 au have on average more massive sheaths. we conclude that this is because they are more effectively slowed down by drag during their travel from the sun. slow mcs also have a more symmetric magnetic field and sheaths expanding similarly as their following mc, while in contrast, fast mcs have an asymmetric magnetic profile and a sheath in compression. in all types of mcs, we find that the proton density and the temperature and the magnetic fluctuations can diffuse within the front of the mc due to 3d reconnection. finally, we derive a quantitative model that describes the decrease in cosmic rays as a function of the amount of magnetic fluctuations and field strength.conclusions: the obtained typical profiles of sheath, mc and gcr properties corresponding to slow, middle, and fast icmes, can be used for forecasting or modelling these events, and to better understand the transport of energetic particles in icmes. they are also useful for improving future operative space weather activities. | superposed epoch study of icme sub-structures near earth and their effects on galactic cosmic rays |
we present evidence that excesses in be in polluted white dwarfs (wds) are the result of accretion of icy exomoons that formed in the radiation belts of giant exoplanets. here we use excess be in the white dwarf galex j2339-0424 as an example. we constrain the parent body abundances of rock-forming elements in galex j2339-0424 and show that the overabundance of beryllium in this wd cannot be accounted for by differences in diffusive fluxes through the wd outer envelope nor by chemical fractionations during typical rock-forming processes. we argue instead that the be was produced by energetic proton irradiation of ice mixed with rock. we demonstrate that the mev proton fluence required to form the high be/o ratio in the accreted parent body is consistent with irradiation of ice in the rings of a giant planet within its radiation belt, followed by accretion of the ices to form a moon that is later accreted by the wd. the icy moons of saturn serve as useful analogs. our results provide an estimate of spallogenic nuclide excesses in icy moons formed by rings around giant planets in general, including those in the solar system. while excesses in be have been detected in two polluted wds to date, including the wd described here, we predict that excesses in the other spallogenic elements li and b, although more difficult to detect, should also be observed, and that such detections would also indicate pollution by icy exomoons formed in the ring systems of giant planets. | icy exomoons evidenced by spallogenic nuclides in polluted white dwarfs |
the new taiga-hiscore non-imaging cherenkov array aims to detect air showers induced by gamma rays above 30 tev and to study cosmic rays above 100 tev. taiga-hiscore is made of integrating air cherenkov detector stations with a wide field of view (0.6 sr), placed at a distance of about 100 m. they cover an area of initially ∼0.25 km2 (prototype array), and of ∼5 km2 at the final phase of the experiment. each station includes 4 pmts with 20 or 25 cm diameter, equipped with light guides shaped as winstone cones. we describe the design, specifications of the read-out, daq and control and monitoring systems of the array. the present 28 detector stations of the taiga-hiscore engineering setup are in operation since september 2015. | the wide-aperture gamma-ray telescope taiga-hiscore in the tunka valley: design, composition and commissioning |
the voyager 1 (v1) and voyager 2 (v2) spacecraft were launched in 1977 on a mission to explore the outer planets and reach the heliopause, the boundary between the hot solar plasma and the relatively cool interstellar plasma. v1 reached the heliopause on 2012 august 25, at 121.6 au, and v2 reached the heliopause on 2018 november 5, at 119.0 au. one of their remarkable discoveries was the detection of shocks propagating into the interstellar plasma from energetic solar events. these shocks are typically preceded by electron plasma oscillations excited by electron beams streaming along interstellar magnetic field lines ahead of the shocks. the frequencies of the plasma oscillations have now provided radial electron density profiles in the outer heliosphere and in the interstellar medium to radial distances of more than 145 au. the oscillations are typically preceded by bursts of high-energy ∼5-100 mev electrons. these electron bursts are interpreted as being due to the reflection (and acceleration) of cosmic-ray electrons by the shock at the time the shock first contacts the magnetic field line that passes through the spacecraft. relative timing between the cosmic rays reflected by the shock and the onset of the plasma oscillations allow us, for the first time, to estimate the energy, ∼20-100 ev, of the electron beams responsible for the plasma oscillations. these observations are combined into a self-consistent model called the foreshock model that describes the interaction of shocks of solar origin with the interstellar plasma. | a foreshock model for interstellar shocks of solar origin: voyager 1 and 2 observations |
we evaluate and characterize the directional response of the semiconductor pixel detector timepix to charged particles and secondary cosmic rays. the detector granularity and per-pixel spectrometric response enable to perform directional sensitive tracking of energetic charged particles in wide field-of-view. in the highly integrated minipix readout the detector serves as a miniaturized, low-power and easily deployable particle micro-tracker. angular measurements require normalization for the acceptance angle and geometric factor which are described and taken into account. the methodology and evaluation of directional response are developed for light charged particles and atmospheric secondary cosmic rays. tests and calibration of angular resolution were performed with electron and proton beams. resulting angular distributions are expressed in terms of elevation and azimuth angles in 14 bins and 36 bins, respectively, over the full 2 π acceptance range. for zenith angle β > 28° the angular distribution is fitted by ∼ cos n (β) with n = 2.0 ± 0.2 expected from secondary cosmic ray muon distribution. | directional detection of charged particles and cosmic rays with the miniaturized radiation camera minipix timepix |
we study the damping processes of both incompressible and compressible magnetohydrodynamic (mhd) turbulence in a partially ionized medium. we start from the linear analysis of mhd waves, applying both single-fluid and two-fluid treatments. the damping rates derived from the linear analysis are then used in determining the damping scales of mhd turbulence. the physical connection between the damping scale of mhd turbulence and the cutoff boundary of linear mhd waves is investigated. we find two branches of slow modes propagating in ions and neutrals, respectively, below the damping scale of slow mhd turbulence, and offer a thorough discussion of their propagation and dissipation behavior. our analytical results are shown to be applicable in a variety of partially ionized interstellar medium (ism) phases and the solar chromosphere. the importance of neutral viscosity in damping the alfvenic turbulence in the interstellar warm neutral medium and the solar chromosphere is demonstrated. as a significant astrophysical utility, we introduce damping effects to the propagation of cosmic rays in partially ionized ism. the important role of turbulence damping in both transit-time damping and gyroresonance is identified. | damping of magnetohydrodynamic turbulence in partially ionized plasma: implications for cosmic ray propagation |
it is widespread opinion that hydrogen reionization is mainly driven by primeval star-forming galaxies, with high-z active galactic nuclei (agns) having a minor role. recent observations, however, challenge this notion, indicating a number of issues related to a galaxy-driven reionization scenario. we provide here an updated assessment of the space density of relatively faint (m1450 ∼ -22.5) agns at zspec ∼ 5.5 in order to improve the estimate of the photoionization rate contribution from accreting supermassive black holes. exploiting deep uv rest-frame ground-based spectra collected at the very large telescope on the candels/goods-south field and deep chandra x-ray images in the candels/goods-north and egs areas, we find two relatively bright (m1450 ∼ -22.5) agns at zspec ∼ 5.5. we derive an agn space density of φ = 1.29 × 10-6 cmpc-3 at z ∼ 5.5 and m1450 ∼ -22.5 by simply dividing their observed number by the cosmological volume in the range 5.0 < z < 6.1. our estimate does not consider corrections for incompleteness; therefore, it represents a lower limit, although uncertainties due to cosmic variance can still be significant. this value supports a high space density of agns at z > 5, in contrast with previous claims mostly based on standard color selection, possibly affected by significant incompleteness. our estimate for the agn photoionization rate at z ∼ 5.5 is in agreement with the observed values at similar redshifts, which are needed to keep the intergalactic medium highly ionized. upcoming james webb space telescope and giant ground-based telescopes observations will improve the study of high-z agns and their contribution to the reionization of the universe. | on the agn nature of two uv-bright sources at zspec ∼ 5.5 in the candels fields: an update on the agn space density at m1450 ∼ -22.5 |
context. supernova remnants are known to accelerate cosmic rays on account of their nonthermal emission of radio waves, x-rays, and gamma rays. although there are many models for the acceleration of cosmic rays in supernova remnants, the escape of cosmic rays from these sources has not yet been adequately studied.aims: we aim to use our time-dependent acceleration code ratpac to study the acceleration of cosmic rays and their escape in post-adiabatic supernova remnants and calculate the subsequent gamma-ray emission from inverse-compton scattering and pion decay.methods: we performed spherically symmetric 1d simulations in which we simultaneously solved the transport equations for cosmic rays, magnetic turbulence, and the hydrodynamical flow of the thermal plasma in a volume large enough to keep all cosmic rays in the simulation. the transport equations for cosmic rays and magnetic turbulence were coupled via the cosmic-ray gradient and the spatial diffusion coefficient of the cosmic rays, while the cosmic-ray feedback onto the shock structure can be ignored. our simulations span 100 000 years, thus covering the free-expansion, the sedov-taylor, and the beginning of the post-adiabatic phase of the remnant's evolution.results: at later stages of the evolution, cosmic rays over a wide range of energy can reside outside of the remnant, creating spectra that are softer than predicted by standard diffusive shock acceleration, and feature breaks in the 10 - 100 gev-range. the total spectrum of cosmic rays released into the interstellar medium has a spectral index of s ≈ 2.4 above roughly 10 gev which is close to that required by galactic propagation models. we further find the gamma-ray luminosity to peak around an age of 4000 years for inverse-compton-dominated high-energy emission. remnants expanding in low-density media generally emit more inverse-compton radiation, matching the fact that the brightest known supernova remnants - rcw86, vela jr., hess j1731-347 and rx j1713.7-3946 - are all expanding in low density environments. | cosmic-ray acceleration and escape from post-adiabatic supernova remnants |
the secondary-to-primary ratios are unique tools to investigate cosmic ray propagation mechanisms. in this work, we use the latest data of deuteron-to-helium 4 ratio and helium 3-to-helium 4 ratio measured by pamela combined with other z ≤ 2 primary fluxes measured by pamela and voyager-1, to constrain the cosmic ray acceleration and propagation models. the analysis is performed by interfacing statistical tools with the galprop propagation package. to better fit both the modulated and unmodulated low energy cosmic ray data, we find that a time-, charge- and rigidity-dependent solar modulation model is better than the force-field approximation. among all the studied cosmic ray propagation models, the diffusion-reacceleration-convection model is strongly supported by the derived bayesian evidence. the robustness of the estimated diffusion slope δ is cross-checked by another low-mass secondary-to-primary ratio, i.e. the antiproton-to-proton ratio. it is shown that the diffusion-reacceleration-convection model can reconcile well with the high energy antiproton-to-proton ratio. this indicates that the estimated value of δ is reliable. the well constraint δ from the "best" model is found to be close to 1/3, inferring a kolmogorov-type interstellar magnetic turbulence. | revisit cosmic ray propagation by using 1h, 2h, 3he and 4he |
the interpretation of data from indirect detection experiments searching for dark matter annihilations requires computationally expensive simulations of cosmic-ray propagation. in this work we present a new method based on recurrent neural networks that significantly accelerates simulations of secondary and dark matter galactic cosmic ray antiprotons while achieving excellent accuracy. this approach allows for an efficient profiling or marginalisation over the nuisance parameters of a cosmic ray propagation model in order to perform parameter scans for a wide range of dark matter models. we identify importance sampling as particularly suitable for ensuring that the network is only evaluated in well-trained parameter regions. we present resulting constraints using the most recent ams-02 antiproton data on several models of weakly interacting massive particles. the fully trained networks are released as darkraynet together with this work and achieve a speed-up of the runtime by at least two orders of magnitude compared to conventional approaches. | constraining dark matter annihilation with cosmic ray antiprotons using neural networks |
we extend the description of the isotropic and anisotropic random component of the small-scale magnetic field within the existing magnetic field model of the milky way from jansson & farrar, by including random realizations of the small-scale component. using a magnetic-field power spectrum with gaussian random fields, the ne2001 model for the thermal electrons and the galactic cosmic-ray electron distribution from the current galprop model we derive full-sky maps for the total and polarized synchrotron intensity as well as the faraday rotation-measure distribution. while previous work assumed that small-scale fluctuations average out along the line-of-sight or which only computed ensemble averages of random fields, we show that these fluctuations need to be carefully taken into account. comparing with observational data we obtain not only good agreement with 408 mhz total and wmap7 22 ghz polarized intensity emission maps, but also an improved agreement with galactic foreground rotation-measure maps and power spectra, whose amplitude and shape strongly depend on the parameters of the random field. we demonstrate that a correlation length of 0≈22 pc (05 pc being a 5σ lower limit) is needed to match the slope of the observed power spectrum of galactic foreground rotation-measure maps. using multiple realizations allows us also to infer errors on individual observables. we find that previously-used amplitudes for random and anisotropic random magnetic field components need to be rescaled by factors of ≈0.3 and 0.6 to account for the new small-scale contributions. our model predicts a rotation measure of -2.8±7.1 rad/m2 and 04.4±11. rad/m2 for the north and south galactic poles respectively, in good agreement with observations. applying our model to deflections of ultra-high-energy cosmic rays we infer a mean deflection of ≈3.5±1.1 degree for 60 eev protons arriving from cena. | new constraints on modelling the random magnetic field of the mw |
the results of simulations of extragalactic propagation of ultra-high energy cosmic rays (uhecrs) have intrinsic uncertainties due to poorly known physical quantities and approximations used in the codes. we quantify the uncertainties in the simulated uhecr spectrum and composition due to different models of extragalactic background light (ebl), different photodisintegration setups, approximations concerning photopion production and the use of different simulation codes. we discuss the results for several representative source scenarios with proton, nitrogen or iron at injection. for this purpose we used simprop and crpropa, two publicly available codes for monte carlo simulations of uhecr propagation. crpropa is a detailed and extensive simulation code, while simprop aims to achieve acceptable results using a simpler code. we show that especially the choices for the ebl model and the photodisintegration setup can have a considerable impact on the simulated uhecr spectrum and composition. | effects of uncertainties in simulations of extragalactic uhecr propagation, using crpropa and simprop |
observations of the sun’s corona during the space era have led to a picture of relatively constant, but cyclically varying solar output and structure. longer-term, more indirect measurements, such as from 10be, coupled by other albeit less reliable contemporaneous reports, however, suggest periods of significant departure from this standard. the maunder minimum was one such epoch where: (1) sunspots effectively disappeared for long intervals during a 70 yr period; (2) eclipse observations suggested the distinct lack of a visible k-corona but possible appearance of the f-corona; (3) reports of aurora were notably reduced; and (4) cosmic ray intensities at earth were inferred to be substantially higher. using a global thermodynamic mhd model, we have constructed a range of possible coronal configurations for the maunder minimum period and compared their predictions with these limited observational constraints. we conclude that the most likely state of the corona during—at least—the later portion of the maunder minimum was not merely that of the 2008/2009 solar minimum, as has been suggested recently, but rather a state devoid of any large-scale structure, driven by a photospheric field composed of only ephemeral regions, and likely substantially reduced in strength. moreover, we suggest that the sun evolved from a 2008/2009-like configuration at the start of the maunder minimum toward an ephemeral-only configuration by the end of it, supporting a prediction that we may be on the cusp of a new grand solar minimum. | inferring the structure of the solar corona and inner heliosphere during the maunder minimum using global thermodynamic magnetohydrodynamic simulations |
context. magnetic fields play an important role in the formation and stabilization of spiral structures in galaxies, but the interaction between interstellar gas and magnetic fields has not yet been understood. in particular, the phenomenon of "magnetic arms" located between material arms is a mystery.aims: the strength and structure of interstellar magnetic fields and their relation to spiral arms in gas and dust are investigated in the nearby and almost face-on spiral galaxy ic 342.methods: the total and polarized radio continuum emission of ic 342 was observed with high spatial resolution in four wavelength bands with the effelsberg and vla telescopes. at λ6.2 cm the data from both telescopes were combined. i separated thermal and nonthermal (synchrotron) emission components with the help of the spectral index distribution and derived maps of the magnetic field strength, degree of magnetic field order, magnetic pitch angle, faraday rotation measure, and faraday depolarization.results: ic 342 hosts a diffuse radio disk with an intensity that decreases exponentially with increasing radius. the frequency dependence of the scalelength of synchrotron emission indicates energy-dependent propagation of the cosmic-ray electrons, probably via the streaming instability. the equipartition strength of the total field in the main spiral arms is typically 15 μg, that of the ordered field about 5 μg. the total radio emission, observed with the vla's high resolution, closely follows the dust emission in the infrared at 8 μm (spitzer telescope) and 22 μm (wise telescope). the polarized emission is not diffuse, but concentrated in spiral arms of various types: (1) a narrow arm of about 300 pc width, displaced inwards with respect to the eastern arm by about 200 pc, indicating magnetic fields compressed by a density wave; (2) a broad arm of 300-500 pc width around the northern arm with systematic variations in polarized emission, polarization angles, and faraday rotation measures on a scale of about 2 kpc, indicative of a helically twisted flux tube generated by the parker instability; (3) a rudimentary magnetic arm in an interarm region in the north-west; (4) several broad spiral arms in the outer galaxy, related to spiral arms in the total neutral gas; (5) short features in the outer south-western galaxy, probably distorted by tidal interaction. faraday rotation of the polarization angles reveals an underlying regular field of only ≃0.5μg strength with a large-scale axisymmetric spiral pattern, probably a signature of a mean-field α - ω dynamo, and an about 10 × stronger field that fluctuates on scales of a few 100 pc. the magnetic field around the bar in the central region of ic 342 resembles that of large barred galaxies; it has a regular spiral pattern with a large pitch angle, is directed outwards, and is opposite to the large-scale regular field in the disk. polarized emission at λ20.1 cm is strongly affected by faraday depolarization in the western and northern parts of the galaxy. helical fields extending from disk to halo may account for this asymmetry.conclusions: interstellar magnetic fields interact with the gas and gas flows. density-wave compression generates polarized radio emission at the inner edge of some spiral arms. fast mhd density waves can generate coincident spiral arms in gas and magnetic fields in the outer parts of ic 342. magnetic armsar e offset from the spiral pattern in gas and dust; their generation and development by mean-field dynamo action probably need a spiral pattern that is stable over a few galactic rotation periods, which is probably the case for the galaxy ngc 6946. the mean-field dynamo in ic 342 is slow and weak, probably disturbed by the bar, tidal interaction, or a transient spiral pattern. based on observations with the vla of the nrao at socorro and the 100-m telescope of the max-planck-institut für radioastronomie at effelsberg.final polarization maps (fits format) are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/578/a93 | magnetic fields in the nearby spiral galaxy ic 342: a multi-frequency radio polarization study |
we reconstructed the energy and the position of the shower maximum of air showers with energies e ≳ 100 pev applying a method using radio measurements performed with tunka-rex. an event-to-event comparison to air-cherenkov measurements of the same air showers with the tunka-133 photomultiplier array confirms that the radio reconstruction works reliably. the tunka-rex reconstruction methods and absolute scales have been tuned on coreas simulations and yield energy and xmax values consistent with the tunka-133 measurements. the results of two independent measurement seasons agree within statistical uncertainties, which gives additional confidence in the radio reconstruction. the energy precision of tunka-rex is comparable to the tunka-133 precision of 15%, and exhibits a 20% uncertainty on the absolute scale dominated by the amplitude calibration of the antennas. for xmax, this is the first direct experimental correlation of radio measurements with a different, established method. at the moment, the xmax resolution of tunka-rex is approximately 40 g/cm2. this resolution can probably be improved by deploying additional antennas and by further development of the reconstruction methods, since the present analysis does not yet reveal any principle limitations. | radio measurements of the energy and the depth of the shower maximum of cosmic-ray air showers by tunka-rex |
the spectral shape of cosmic ray positrons and antiprotons has been accurately measured in the broad kinetic energy range 1-350 gev. in the higher part of this range (e ≳30 gev ), the e+ and p ¯ are both well described by power laws with spectral indices γe+≃2.77 ±0.02 and γp ¯≃2.78 ±0.04 that are approximately equal to each other and to the spectral index of protons. in the same energy range, the positron-antiproton flux ratio has the approximately constant value 2.04 ±0.04 , that is consistent with being equal to the ratio e+/p ¯ calculated for the conventional mechanism of production, where the antiparticles are created as secondaries in the inelastic interactions of primary cosmic rays with interstellar gas. the positron-antiproton ratio at lower energy is significantly higher (reaching a value e+/p ¯≈100 for e ≈1 gev ), but, in the entire energy range 1-350 gev, the flux ratio is consistent with being equal to the ratio of the production rates in the conventional mechanism, as the production of low-energy antiprotons is kinematically suppressed in collisions with a target at rest. these results strongly suggest that cosmic ray positrons and antiprotons have a common origin as secondaries in hadronic interactions. this conclusion has broad implications for the astrophysics of cosmic rays in the galaxy. | interpretation of the cosmic ray positron and antiproton fluxes |
based on recent proposal to associate icecube tev and pev neutrino events with gamma-ray bursts~(grbs) by considering the lorentz violation of neutrinos, we provide a new estimate on the grb neutrino flux and such result is much bigger than previous results by the icecube collaboration. among these 24 neutrino ``shower" events above 60~tev, 12 events are associated with grbs. such result is comparable with the prediction from grb fireball models. analysis of track events provide consistent result with the shower events to associate high energy cosmic neutrinos with grbs under the same lorentz violation features of neutrinos. we also make a background estimation and reveal grbs as a significant source for the ultra-high energy icecube neutrino events. our work supports the lorentz violation and $cpt$-violation of neutrinos, indicating new physics beyond relativity. | ultra-high energy cosmic neutrinos from gamma-ray bursts |
the origin of the extended x-ray emission in the large-scale jets of active galactic nuclei (agns) poses challenges to conventional models of acceleration and emission. although electron synchrotron radiation is considered the most feasible radiation mechanism, the formation of the continuous large-scale x-ray structure remains an open issue. as astrophysical jets are expected to exhibit some turbulence and shearing motion, we here investigate the potential of shearing flows to facilitate an extended acceleration of particles and evaluate its impact on the resultant particle distribution. our treatment incorporates systematic shear and stochastic second-order fermi effects. we show that for typical parameters applicable to large-scale agn jets, stochastic second-order fermi acceleration, which always accompanies shear particle acceleration, can play an important role in facilitating the whole process of particle energization. we study the time-dependent evolution of the resultant particle distribution in the presence of second-order fermi acceleration, shear acceleration, and synchrotron losses using a simple fokker-planck approach and provide illustrations for the possible emergence of a complex (multicomponent) particle energy distribution with different spectral branches. we present examples for typical parameters applicable to large-scale agn jets, indicating the relevance of the underlying processes for understanding the extended x-ray emission and the origin of ultrahigh-energy cosmic rays. | particle acceleration in mildly relativistic shearing flows: the interplay of systematic and stochastic effects, and the origin of the extended high-energy emission in agn jets |
dark matter could take the form of dark massive compact halo objects (dmachos); i.e., composite objects that are made up of dark-sector elementary particles, that could have a macroscopic mass from the planck scale to above the solar mass scale, and that also admit a wide range of energy densities and sizes. concentrating on the gravitational interaction of dmachos with visible matter, we map out the mass-radius parameter space that is consistent with gravitational lensing experiments, as well as anisotropies of the cosmic microwave background (cmb) based on the spherical accretion of matter onto a dmacho in the hydrostatic approximation. for dmachos with a uniform-density mass profile and total mass in the range of ~ 10-12-10 msolar, we find that a dmacho could explain 100% of the dark matter if its radius is above ≈ 3 times the einstein radius of the lensing system. for a larger mass above 10 msolar, a dmacho with radius above ~ 1 × 108 cm ×(m/100 msolar)9/2 is consistent with cmb observables. for a lighter dmacho with mass below ~ 10-12 msolar, there still is not a good experimental probe. finally, we point out that heavier dmachos with masses ~ 0.1 msolar may be observed by x-ray and optical telescopes if they reside at rest in a large molecular cloud, nearby to our solar system, and accrete ordinary matter to emit photons. | tests of dark machos: lensing, accretion, and glow |
i present the first public releases (v3.4 and v3.5) of the usine code for cosmic-ray propagation in the galaxy (https://lpsc.in2p3.fr/usine). it contains several semi-analytical propagation models previously used in the literature (leaky-box model, 2-zone 1d and 2d diffusion models) for the calculation of nuclei (z = 1 - 30), anti-protons, and anti-deuterons. for minimisations, the geometry, transport, and source parameters of all models can be enabled as free parameters, whereas nuisance parameters are enabled on solar modulation levels, cross sections (inelastic and production), and systematics of the cr data. with a single ascii initialisation file to configure runs, its many displays, and the speed associated to semi-analytical approaches, usine should be a useful tool for beginners, but also for experts to perform statistical analyses of high-precision cosmic-ray data. | usine: semi-analytical models for galactic cosmic-ray propagation |
protoplanetary disk evolution is strongly impacted by ionization from the central star and local environment, which collectively have been shown to drive chemical complexity and are expected to impact the transport of disk material. nonetheless, ionization remains a poorly constrained input to many detailed modeling efforts. we use new and archival alma observations of n2h+ 3-2 and h13co+ 3-2 to derive the first observationally motivated ionization model for the im lup protoplanetary disk. incorporating ionization from multiple internal and external sources, we model n2h+ and h13co+ abundances under varying ionization environments and compare these directly to the imaged alma observations by performing non-lte radiative transfer, visibility sampling, and imaging. we find that the observations are best reproduced using a radially increasing cosmic-ray (cr) gradient, with low cr ionization in the inner disk, high cr ionization in the outer disk, and a transition at ∼80-100 au. this location is approximately coincident with the edge of spiral structure identified in millimeter emission. we also find that im lup shows evidence for enhanced uv-driven formation of hco+, which we attribute to the disk's high flaring angle. in summary, im lup represents the first protoplanetary disk with observational evidence for a cr gradient, which may have important implications for im lup's ongoing evolution, especially given the disk's young age and large size. | evidence for a cosmic-ray gradient in the im lup protoplanetary disk |
at peak, long-duration gamma-ray bursts are the most luminous sources of electromagnetic radiation known. since their progenitors are massive stars, they provide a tracer of star formation and star-forming galaxies over the whole of cosmic history. their bright power-law afterglows provide ideal backlights for absorption studies of the interstellar and intergalactic medium back to the reionization era. the proposed theseus mission is designed to detect large samples of grbs at z > 6 in the 2030s, at a time when supporting observations with major next generation facilities will be possible, thus enabling a range of transformative science. theseus will allow us to explore the faint end of the luminosity function of galaxies and the star formation rate density to high redshifts; constrain the progress of re-ionisation beyond z ≳6 ; study in detail early chemical enrichment from stellar explosions, including signatures of population iii stars; and potentially characterize the dark energy equation of state at the highest redshifts. | exploration of the high-redshift universe enabled by theseus |
lorentz invariance violation (liv) is often described by dispersion relations of the form $e_i^2=m_i^2+p_i^2+\delta_{i,n} e^{2+n}$ with delta different based on particle type $i$, with energy $e$, momentum $p$ and rest mass $m$. kinematics and energy thresholds of interactions are modified once the liv terms become comparable to the squared masses of the particles involved. thus, the strongest constraints on the liv coefficients $\delta_{i,n}$ tend to come from the highest energies. at sufficiently high energies, photons produced by cosmic ray interactions as they propagate through the universe could be subluminal and unattenuated over cosmological distances. cosmic ray interactions can also be modified and lead to detectable fingerprints in the energy spectrum and mass composition observed on earth. the data collected at the pierre auger observatory are therefore possibly sensitive to both the electromagnetic and hadronic sectors of liv. in this article, we explore these two sectors by comparing the energy spectrum and the composition of cosmic rays and the upper limits on the photon flux from the pierre auger observatory with simulations including liv. constraints on liv parameters depend strongly on the mass composition of cosmic rays at the highest energies. for the electromagnetic sector, while no constraints can be obtained in the absence of protons beyond $10^{19}$ ev, we obtain $\delta_{\gamma,0} > -10^{-21}$, $\delta_{\gamma,1} > -10^{-40}$ ev$^{-1}$ and $\delta_{\gamma,2} > -10^{-58}$ ev$^{-2}$ in the case of a subdominant proton component up to $10^{20}$ ev. for the hadronic sector, we study the best description of the data as a function of liv coefficients and we derive constraints in the hadronic sector such as $\delta_{\mathrm{had},0} < 10^{-19}$, $\delta_{\mathrm{had},1} < 10^{-38}$ ev$^{-1}$ and $\delta_{\mathrm{had},2}< 10^{-57}$ ev$^{-2}$ at 5$\sigma$ cl. | testing effects of lorentz invariance violation in the propagation of astroparticles with the pierre auger observatory |
most accelerator-based space radiation experiments have been performed with single ion beams at fixed energies. however, the space radiation environment consists of a wide variety of ion species with a continuous range of energies. due to recent developments in beam switching technology implemented at the nasa space radiation laboratory (nsrl) at brookhaven national laboratory (bnl), it is now possible to rapidly switch ion species and energies, allowing for the possibility to more realistically simulate the actual radiation environment found in space. the present paper discusses a variety of issues related to implementation of galactic cosmic ray (gcr) simulation at nsrl, especially for experiments in radiobiology. advantages and disadvantages of different approaches to developing a gcr simulator are presented. in addition, issues common to both gcr simulation and single beam experiments are compared to issues unique to gcr simulation studies. a set of conclusions is presented as well as a discussion of the technical implementation of gcr simulation. | galactic cosmic ray simulation at the nasa space radiation laboratory |
the einstein equivalence principle (eep) can be probed with astrophysical sources emitting simultaneously different types of neutral particles, or particles with varying energies, by testing their time of flight through the same gravitational field. here we use the time delays between correlated photons from cosmological transients to constrain the accuracy of the eep. we take data from two gamma-ray bursts as an example and, as a lower limit to the theoretical time delays between different energies, we use delays arising from only the gravitational field of our own galaxy. we then show that the parameterized post-newtonian parameter γ is the same for photons over energy ranges between ev and mev and between mev and gev to a part in 10-7, which is at least one order of magnitude better than previous limits. combining this bound on the wavelength dependence of γ with the absolute bound | γ -1| \lt 0.3% from light-deflection measurements at optical (ev) wavelengths, we thus extend this absolute bound on γ to gev energies. | cosmic transients test einstein's equivalence principle out to gev energies |
molecular abundances are sensitive to the uv photon flux and cosmic-ray ionization rate. in starburst environments, the effects of high-energy photons and particles are expected to be stronger. we examine these astrochemical signatures through multiple transitions of hco+ and its metastable isomer hoc+ in the center of the starburst galaxy ngc 253 using data from the atacama large millimeter/submillimeter array large program alma comprehensive high-resolution extragalactic molecular inventory. the distribution of the hoc+(1-0) integrated intensity shows its association with "superbubbles," cavities created either by supernovae or expanding h ii regions. the observed hco+/hoc+ abundance ratios are ~10-150, and the fractional abundance of hoc+ relative to h2 is ~1.5 × 10-11-6 × 10-10, which implies that the hoc+ abundance in the center of ngc 253 is significantly higher than in quiescent spiral arm dark clouds in the galaxy and the galactic center clouds. comparison with chemical models implies either an interstellar radiation field of g 0 ≳ 103 if the maximum visual extinction is ≳5, or a cosmic-ray ionization rate of ζ ≳ 10-14 s-1 (3-4 orders of magnitude higher than that within clouds in the galactic spiral arms) to reproduce the observed results. from the difference in formation routes of hoc+, we propose that a low-excitation line of hoc+ traces cosmic-ray dominated regions, while high-excitation lines trace photodissociation regions. our results suggest that the interstellar medium in the center of ngc 253 is significantly affected by energy input from uv photons and cosmic rays, sources of energy feedback. | starburst energy feedback seen through hco+/hoc+ emission in ngc 253 from alchemi |
the last solar minimum activity period, and the consequent minimum modulation conditions for cosmic rays, was unusual. the highest levels of galactic protons were recorded at earth in late 2009 in contrast to expectations. a comprehensive model was used to study the proton modulation for the period from 2006 to 2009 in order to determine what basic processes were responsible for solar modulation during this period and why it differs from proton modulation during previous solar minimum modulation periods. this established model is now applied to studying the solar modulation of electron spectra as observed for 80 mev-30 gev by the pamela space detector from mid-2006 to the end of 2009. over this period the heliospheric magnetic field had decreased significantly until the end of 2009 while the waviness of the heliospheric current sheet decreased moderately and the observed electron spectra increased by a factor of ∼1.5 at 1.0 gev to ∼3.5 at 100 mev. in order to reproduce the modulation evident from seven consecutive semesters, the diffusion coefficients had to increase moderately while maintaining the basic rigidity dependence. it is confirmed that the main diffusion coefficients are independent of rigidity below ∼0.5 gv, while the drift coefficient had to be reduced below this value. the 2006-2009 solar minimum epoch indeed was different than previously observed minima, at least since the beginning of the space exploration era. this period could be called “diffusion-dominated” as was also found for the modulation of protons. | modulation of galactic electrons in the heliosphere during the unusual solar minimum of 2006-2009: a modeling approach |
high-energy x-ray and ultraviolet (uv) radiation from young stars impacts planetary atmospheric chemistry and mass loss. the active ~22 myr m dwarf au mic hosts two exoplanets orbiting interior to its debris disk. therefore, this system provides a unique opportunity to quantify the effects of stellar x-ray and uv irradiation on planetary atmospheres as a function of both age and orbital separation. in this paper, we present over 5 hr of far-uv (fuv) observations of au mic taken with the cosmic origins spectrograph (cos; 1070-1360 å) on the hubble space telescope (hst). we provide an itemization of 120 emission features in the hst/cos fuv spectrum and quantify the flux contributions from formation temperatures ranging from 104 to 107 k. we detect 13 flares in the fuv white-light curve with energies ranging from 1029 to 1031 erg s. the majority of the energy in each of these flares is released from the transition region between the chromosphere and the corona. there is a 100× increase in flux at continuum wavelengths λ < 1100 å in each flare, which may be caused by thermal bremsstrahlung emission. we calculate that the baseline atmospheric mass-loss rate for au mic b is ~108 g s-1, although this rate can be as high as ~1014 g s-1 during flares with ${l}_{\mathrm{flare}}\simeq {10}^{33}$ erg s-1. finally, we model the transmission spectra for au mic b and c with a new panchromatic spectrum of au mic and motivate future jwst observations of these planets. | au microscopii in the far-uv: observations in quiescence, during flares, and implications for au mic b and c |
the energy spectra of primary and secondary cosmic rays (crs) generally harden at several hundreds of gev, a finding which can be naturally interpreted by means of propagation effects. we adopt a spatially dependent cr propagation model to fit the spectral hardening, where a slow-diffusion disk (sdd) is assumed near the galactic plane. we aim to constrain the propagation parameters with a bayesian parameter estimation based on a markov chain monte carlo sampling algorithm. the latest precise measurements of carbon spectrum and b/c ratio are adopted in the bayesian analysis. the 10be / 9be and be/b ratios are also included to break parameter degeneracies. the fitting result shows that all the parameters are well constrained. especially, the thickness of the sdd is limited to 0.4-0.5 kpc above and below the galactic plane, which could be the best constraint for the slow-diffusion region among similar works. the p ¯/p ratio and the amplitude of cr anisotropy predicted by the sdd model are consistent with the observations, while the predicted high-energy electron and positron fluxes are slightly and significantly lower than the observations, respectively, indicating the necessity of extra sources. | constraints on the spatially dependent cosmic-ray propagation model from bayesian analysis |
when atoms are placed into liquids, their optical spectral lines corresponding to the electronic transitions are greatly broadened compared to those of single, isolated atoms. this linewidth increase can often reach a factor of more than a million, obscuring spectroscopic structures and preventing high-resolution spectroscopy, even when superfluid helium, which is the most transparent, cold and chemically inert liquid, is used as the host material1-6. here we show that when an exotic helium atom with a constituent antiproton7-9 is embedded into superfluid helium, its visible-wavelength spectral line retains a sub-gigahertz linewidth. an abrupt reduction in the linewidth of the antiprotonic laser resonance was observed when the liquid surrounding the atom transitioned into the superfluid phase. this resolved the hyperfine structure arising from the spin-spin interaction between the electron and antiproton with a relative spectral resolution of two parts in 106, even though the antiprotonic helium resided in a dense matrix of normal matter atoms. the electron shell of the antiprotonic atom retains a small radius of approximately 40 picometres during the laser excitation7. this implies that other helium atoms containing antinuclei, as well as negatively charged mesons and hyperons that include strange quarks formed in superfluid helium, may be studied by laser spectroscopy with a high spectral resolution, enabling the determination of the particle masses9. the sharp spectral lines may enable the detection of cosmic-ray antiprotons10,11 or searches for antideuterons12 that come to rest in liquid helium targets. | high-resolution laser resonances of antiprotonic helium in superfluid 4he |
in situ soil moisture sensors provide highly accurate but very local soil moisture measurements, while remotely sensed soil moisture is strongly affected by vegetation and surface roughness. in contrast, cosmic-ray neutron sensors (crnss) allow highly accurate soil moisture estimation on the field scale which could be valuable to improve land surface model predictions. in this study, the potential of a network of crnss installed in the 2354 km2 rur catchment (germany) for estimating soil hydraulic parameters and improving soil moisture states was tested. data measured by the crnss were assimilated with the local ensemble transform kalman filter in the community land model version 4.5. data of four, eight and nine crnss were assimilated for the years 2011 and 2012 (with and without soil hydraulic parameter estimation), followed by a verification year 2013 without data assimilation. this was done using (i) a regional high-resolution soil map, (ii) the fao soil map and (iii) an erroneous, biased soil map as input information for the simulations. for the regional soil map, soil moisture characterization was only improved in the assimilation period but not in the verification period. for the fao soil map and the biased soil map, soil moisture predictions improved strongly to a root mean square error of 0.03 cm3 cm-3 for the assimilation period and 0.05 cm3 cm-3 for the evaluation period. improvements were limited by the measurement error of crnss (0.03 cm3 cm-3). the positive results obtained with data assimilation of nine crnss were confirmed by the jackknife experiments with four and eight crnss used for assimilation. the results demonstrate that assimilated data of a crns network can improve the characterization of soil moisture content on the catchment scale by updating spatially distributed soil hydraulic parameters of a land surface model. | evaluation of a cosmic-ray neutron sensor network for improved land surface model prediction |
during the late pleistocene, the main mountain ranges of the iberian peninsula were covered by small icefields and cirque and alpine glaciers. the deglaciation triggered paraglacial processes that generated landforms, mostly within the ice-free glacial cirques. in this research we analyse the deglaciation process in the muxivén cirque (42°15'n - 6°16'w), in the upper sil river basin, which includes some of the largest relict rock glaciers of the cantabrian mountains. we addressed this objective by means of accurate geomorphological reconstructions, sedimentological analysis, schmidt-hammer surface weathering measurements and a dataset of 10 10be cosmic-ray exposure ages. results reveal that after ~16 ka, glaciers retreated to the bottom of the cirques at the headwaters of the valley, leaving the walls free of ice and triggering rock avalanches onto the remnants of these glaciers. this paraglacial process supplied debris to a small glacier within muxivén cirque, which transformed in two rock glaciers. these debris isolated the ice inside the rock glaciers only for a very short period of time and ended up melting completely before the younger dryas. the lower sector of the largest one stabilized at 14.5 ± 1.5 ka, while the upper sector remained active until 13.5 ± 0.8 ka. previous to the stabilization of the lower sector of the northern rock glacier, at its margin a high-energy debris avalanche occurred at ~14.0 ± 0.9 ka. these data agree with previous research, corroborating the paraglacial origin of most iberian rock glaciers during the bølling-allerød interstadial. | the origin and collapse of rock glaciers during the bølling-allerød interstadial: a new study case from the cantabrian mountains (spain) |
noise and stability of current state of the art near-infrared (nir) array detectors are still substantially worse than optical science grade ccds used in astronomy. obtaining the maximum signal-to-noise ratio in flux image is important for many nir instruments, as is stable well understood data reduction and extraction. the habitable- zone planet finder (hpf) is a near-infrared ultra stable precision radial velocity (rv) spectrograph commissioned on 10-m hobby-eberly telescope (het), mcdonald observatory, texas, usa. hpf uses a teledyne h2rg array detector. in order to achieve the high-precision ( 1 m/s) rv measurements from the nir spectrum of hpf's science target stars, it is vital to maximize the signal-to-noise ratio and to accurately propagate the uncertainties. here we present the algorithms we have developed to significantly improve the quality of flux images calculated from the up-the-ramp readout mode of h2rg. the algorithms in the tool hxrgproc presented in this manuscript are used for hpf's bias noise removal, non-linearity correction, cosmic ray correction, slope/flux and variance image calculation. | the habitable-zone planet finder: improved flux image generation algorithms for h2rg up-the-ramp data |
the nena and the mgal cycles play a fundamental role in the nucleosynthesis of asymptotic giant branch stars undergoing hot bottom burning. the 23na (p , γ)24mg reaction links these two cycles and a precise determination of its rate is required to correctly estimate the contribution of these stars to the chemical evolution of various isotopes of na, mg and al. at temperatures of 50 ≲ t ≲ 110mk, narrow resonances at ep = 140 and 251kev are the main contributors to the reaction rate, in addition to the direct capture that dominates in the lower part of the temperature range. we present new measurements of the strengths of these resonances at the laboratory for underground nuclear astrophysics (luna). we have used two complementary detection approaches: high efficiency with a 4π bgo detector for the 140 kev resonance, and high resolution with a hpge detector for the 251 kev resonance. thanks to the reduced cosmic ray background of luna, we were able to determine the resonance strength of the 251 kev resonance as ωγ = 482 (82) μev and observed new gamma ray transitions for the decay of the corresponding state in 24mg at ex = 11931kev. with the highly efficient bgo detector, we observed a signal for the 140 kev resonance for the first time in a direct measurement, resulting in a strength of ωγ140 = 1.46-0.53+0.58 nev (68% cl). our measurement reduces the uncertainty of the 23na (p , γ)24mg reaction rate in the temperature range from 0.05 to 0.1 gk to at most -35%+50% at 0.07 gk. accordingly, our results imply a significant reduction of the uncertainties in the nucleosynthesis calculations. | direct measurements of low-energy resonance strengths of the 23na(p,γ)24mg reaction for astrophysics |
we make quantitative estimates of the power supplied to the galactic cosmic ray population by second-order fermi acceleration in the interstellar medium, or as it is usually termed in cosmic ray propagation studies, diffusive reacceleration. using recent results on the local interstellar spectrum, following voyager 1's crossing of the heliopause, we show that for parameter values, in particular the alfvén speed, typically used in propagation codes such as galprop to fit the b/c ratio, the power contributed by diffusive reacceleration is significant and can be of order 50% of the total galactic cosmic ray power. the implications for the damping of interstellar turbulence are briefly considered. | power requirements for cosmic ray propagation models involving diffusive reacceleration; estimates and implications for the damping of interstellar turbulence |
we have performed two-dimensional hybrid simulations of non-relativistic collisionless shocks in the presence of pre-existing energetic particles (`seeds') such a study applies, for instance, to the re-acceleration of galactic cosmic rays (crs) in supernova remnant (snr) shocks and solar wind energetic particles in heliospheric shocks. energetic particles can be effectively reflected and accelerated regardless of shock inclination via a process that we call diffusive shock re-acceleration. we find that re-accelerated seeds can drive the streaming instability in the shock upstream and produce effective magnetic field amplification. this can eventually trigger the injection of thermal protons even at oblique shocks that ordinarily cannot inject thermal particles. we characterize the current in reflected seeds, finding that it tends to a universal value j ≃ encrvsh, where encr is the seed charge density and vsh is the shock velocity. when applying our results to snrs, we find that the re-acceleration of galactic crs can excite the bell instability to nonlinear levels in less than ∼10 yr, thereby providing a minimum level of magnetic field amplification for any snr shock. finally, we discuss the relevance of diffusive shock re-acceleration also for other environments, such as heliospheric shocks, galactic superbubbles and clusters of galaxies. | diffusive shock re-acceleration |
galaxy clusters are the most massive virialized structures in the universe and are formed through the gravitational accretion of matter over cosmic time1. the discovery2 of an evolved galaxy cluster at redshift z = 2, corresponding to a look-back time of 10.4 billion years, provides an opportunity to study its properties. the galaxy cluster xlssc 122 was originally detected as a faint, extended x-ray source in the xmm large scale structure survey and was revealed to be coincident with a compact over-density of galaxies2 with photometric redshifts of 1.9 ± 0.2. subsequent observations3 at millimetre wavelengths detected a sunyaev-zel'dovich decrement along the line of sight to xlssc 122, thus confirming the existence of hot intracluster gas, while deep imaging spectroscopy from the european space agency's x-ray multi-mirror mission (xmm-newton) revealed4 an extended, x-ray-bright gaseous atmosphere with a virial temperature of 60 million kelvin, enriched with metals to the same extent as are local clusters. here we report optical spectroscopic observations of xlssc 122 and identify 37 member galaxies at a mean redshift of 1.98, corresponding to a look-back time of 10.4 billion years. we use photometry to determine a mean, dust-free stellar age of 2.98 billion years, indicating that star formation commenced in these galaxies at a mean redshift of 12, when the universe was only 370 million years old. the full range of inferred formation redshifts, including the effects of dust, covers the interval from 7 to 13. these observations confirm that xlssc 122 is a remarkably mature galaxy cluster with both evolved stellar populations in the member galaxies and a hot, metal-rich gas composing the intracluster medium. | spectroscopic confirmation of a mature galaxy cluster at a redshift of 2 |
the history of dark universe physics can be traced from processes in the very early universe to the modern dominance of dark matter and energy. here, we review the possible nontrivial role of strong interactions in cosmological effects of new physics. in the case of ordinary qcd interaction, the existence of new stable colored particles such as new stable quarks leads to new exotic forms of matter, some of which can be candidates for dark matter. new qcd-like strong interactions lead to new stable composite candidates bound by qcd-like confinement. we put special emphasis on the effects of interaction between new stable hadrons and ordinary matter, formation of anomalous forms of cosmic rays and exotic forms of matter, like stable fractionally charged particles. the possible correlation of these effects with high energy neutrino and cosmic ray signatures opens the way to study new physics of strong interactions by its indirect multi-messenger astrophysical probes. | new physics of strong interaction and dark universe |
aims: in the presence of a sufficient amount of target material, γ-rays can be used as a tracer in the search for sources of galactic cosmic rays (crs). here we present deep observations of the galactic center (gc) region with the magic telescopes and use them to infer the underlying cr distribution and to study the alleged pev proton accelerator at the center of our galaxy.methods: we used data from ≈100 h observations of the gc region conducted with the magic telescopes over five years (from 2012 to 2017). those were collected at high zenith angles (58-70 deg), leading to a larger energy threshold, but also an increased effective collection area compared to low zenith observations. using recently developed software tools, we derived the instrument response and background models required for extracting the diffuse emission in the region. we used existing measurements of the gas distribution in the gc region to derive the underlying distribution of crs. we present a discussion of the associated biases and limitations of such an approach.results: we obtain a significant detection for all four model components used to fit our data (sgr a*, "arc", g0.9+0.1, and an extended component for the galactic ridge). we observe no significant difference between the γ-ray spectra of the immediate gc surroundings, which we model as a point source (sgr a*) and the galactic ridge. the latter can be described as a power-law with index 2 and an exponential cut-off at around 20 tev with the significance of the cut-off being only 2σ. the derived cosmic-ray profile hints to a peak at the gc position and with a measured profile index of 1.2 ± 0.3 is consistent with the 1/r radial distance scaling law, which supports the hypothesis of a cr accelerator at the gc. we argue that the measurements of this profile are presently limited by our knowledge of the gas distribution in the gc vicinity. tables and sky maps are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/642/a190 | magic observations of the diffuse γ-ray emission in the vicinity of the galactic center |
the hypothesis of nonradiative neutrino decay is tested using the latest icecube data. the track-to-shower ratio expected in icecube is calculated in a complete decay scenario, taking into account the uncertainties in neutrino oscillation parameters and assuming only one stable neutrino. the subset of high-energy neutrino events observed by icecube above 60 tev, combined with the information provided by passing muons, actually disfavors the possibility of neutrinos decay at about a 2 σ level of significance for both the normal and inverted neutrino mass hierarchy. | testing nonradiative neutrino decay scenarios with icecube data |
context. the gas mass of protoplanetary disks and the gas-to-dust ratio are two key elements driving the evolution of these disks and the formation of planetary system.aims: we explore to what extent co (or its isotopologues) can be used as a tracer of gas mass.methods: we use a detailed gas-grain chemical model and study the evolution of the disk composition, starting from a dense prestellar core composition. we explore a range of disk temperature profiles, cosmic-ray ionization rates, and disk ages for a disk model representative of t tauri stars.results: at the high densities that prevail in disks, we find that because of fast reactions on grain surfaces, co can be converted to less volatile forms (principally s-co2, and to a lesser extent s-ch4) instead of being evaporated over a wide range of temperature. the canonical gas-phase abundance of 10-4 is only reached above about 30-35 k. the dominant carbon bearing entity depends on the temperature structure and age of the disk. the chemical evolution of co is also sensitive to the cosmic-ray ionization rate. larger gas phase co abundances are found in younger disks. initial conditions, such as parent cloud age and density, have a limited impact.conclusions: this study reveals that co gas-phase abundance is heavily dependent on grain surface processes, which remain very incompletely understood so far. the strong dependence on dust temperature profile makes co a poor tracer of the gas-phase content of disks. | chemistry in protoplanetary disks: the gas-phase co/h2 ratio and the carbon reservoir |
m-dwarf stars are generally considered favourable for rocky planet detection. however, such planets may be subject to extreme conditions due to possible high stellar activity. the goal of this work is to determine the potential effect of stellar cosmic rays on key atmospheric species of earth-like planets orbiting in the habitable zone of m-dwarf stars and show corresponding changes in the planetary spectra. we build upon the cosmic rays model scheme of previous works, who considered cosmic ray induced nox production, by adding further cosmic ray induced production mechanisms (e.g. for hox) and introducing primary protons of a wider energy range (16 mev-0.5 tev). previous studies suggested that planets in the habitable zone that are subject to strong flaring conditions have high atmospheric methane concentrations, while their ozone biosignature is completely destroyed. our current study shows, however, that adding cosmic ray induced hox production can cause a decrease in atmospheric methane abundance of up to 80%. furthermore, the cosmic ray induced hox molecules react with nox to produce hno3, which produces strong hno3 signals in the theoretical spectra and reduces nox-induced catalytic destruction of ozone so that more than 25% of the ozone column remains. hence, an ozone signal remains visible in the theoretical spectrum (albeit with a weaker intensity) when incorporating the new cosmic ray induced nox and hox schemes, even for a constantly flaring m-star case. we also find that hno3 levels may be high enough to be potentially detectable. since ozone concentrations, which act as the key shield against harmful uv radiation, are affected by cosmic rays via nox-induced catalytic destruction of ozone, the impact of stellar cosmic rays on surface uv fluxes is also studied. | atmospheric effects of stellar cosmic rays on earth-like exoplanets orbiting m-dwarfs |
we propose that ultra-high-energy (uhe) cosmic rays (crs) above 1018 ev are produced in relativistic jets of powerful active galactic nuclei via an original mechanism, which we dub “espresso” acceleration: “seed” galactic crs with energies ≲1017 ev that penetrate the jet sideways receive a “one-shot” boost of a factor of ∼γ2 in energy, where γ is the lorentz factor of the relativistic flow. for typical jet parameters, a few percent of the crs in the host galaxy can undergo this process, and powerful blazars with γ ≳ 30 may accelerate uhecrs up to more than 1020 ev. the chemical composition of espresso-accelerated uhecrs is determined by that at the galactic cr knee and is expected to be proton-dominated at 1018 ev and increasingly heavy at higher energies, in agreement with recent observations made at the pierre auger observatory. | "espresso" acceleration of ultra-high-energy cosmic rays |
the general antiparticle spectrometer (gaps) is a novel approach for indirect dark matter searches that exploits cosmic antiparticles, especially antideuterons. the gaps antideuteron measurement utilizes distinctive detection methods using atomic x-rays and charged particles from the decay of exotic atoms as well as the timing and stopping range of the incoming particle, which together provide excellent antideuteron identification. prior to the future balloon experiment, an accelerator test and a prototype flight were successfully conducted in 2005 and 2012 respectively, in order to verify the gaps detection concept. this paper describes how the sensitivity of gaps to antideuterons was estimated using a monte carlo simulation along with the atomic cascade model and the intra-nuclear cascade model. the sensitivity for the gaps antideuteron search obtained using this method is 2.0 ×10-6 [m-2s-1sr-1(gev/n)-1] for the proposed long duration balloon program (ldb, 35 days × 3 flights), indicating that gaps has a strong potential to probe a wide variety of dark matter annihilation and decay models through antideuteron measurements. gaps is proposed to fly from antarctica in the austral summer of 2019-2020. | antideuteron sensitivity for the gaps experiment |
neutrinos with energies in the pev to eev range produce upgoing extensive air showers when they interact underground close enough to the surface of the earth. we study the possibility for detection of such showers with a system of very wide field-of-view imaging atmospheric cherenkov telescopes, named chant (cherenkov from astrophysical neutrinos telescope), pointing down to a strip below the earth's horizon from space. we find that chant provides sufficient sensitivity for the study of the astrophysical neutrino flux in a wide energy range, from 10 pev to 10 eev. a space-based chant system can discover and study in detail the cosmogenic neutrino flux originating from interactions of ultra-high-energy cosmic rays in the intergalactic medium. | sensitivity of a proposed space-based cherenkov astrophysical-neutrino telescope |
forthcoming astronomical imaging surveys will use weak gravitational lensing shear as a primary probe to study dark energy, with accuracy requirements at the 0.1% level. we present an implementation of the metadetection shear measurement algorithm for use with the vera c. rubin observatory legacy survey of space and time (lsst). this new code works with the data products produced by the lsst science pipelines, and uses the pipeline algorithms when possible. we tested the code using a new set of simulations designed to mimic lsst imaging data. the simulated images contained semi-realistic galaxies, stars with representative distributions of magnitudes and galactic spatial density, cosmic rays, bad ccd columns and spatially variable point spread functions. bright stars were saturated and simulated ``bleed trails'' were drawn. problem areas were interpolated, and the images were coadded into small cells, excluding images not fully covering the cell to guarantee a continuous point spread function. in all our tests the measured shear was accurate within the lsst requirements. | metadetection weak lensing for the vera c. rubin observatory |
a crucial process in galactic cosmic-ray (cr) transport is the spatial diffusion due to the interaction with the interstellar turbulent magnetic field. usually, cr diffusion is assumed to be uniform and isotropic all across the galaxy. however, this picture is clearly inaccurate: several data-driven and theoretical arguments, as well as dedicated numerical simulations, show that diffusion exhibits highly anisotropic properties with respect to the direction of a background (ordered) magnetic field (i.e., parallel or perpendicular to it). in this paper we focus on a recently discovered anomaly in the hadronic cr spectrum inferred by the fermi-lat gamma-ray data at different positions in the galaxy, i.e. the progressive hardening of the proton slope at low galactocentric radii. we propose the idea that this feature can be interpreted as a signature of anisotropic diffusion in the complex galactic magnetic field: in particular, the harder slope in the inner galaxy is due, in our scenario, to the parallel diffusive escape along the poloidal component of the large-scale, regular, magnetic field. we implement this idea in a numerical framework, based on the dragon code, and perform detailed numerical tests on the accuracy of our setup. we discuss how the effect proposed depends on the relevant free parameters involved. based on low-energy extrapolation of the few focused numerical simulations aimed at determining the scalings of the anisotropic diffusion coefficients, we finally present a set of plausible models that reproduce the behavior of the cr proton slopes inferred by gamma-ray data. | a signature of anisotropic cosmic-ray transport in the gamma-ray sky |
at any epoch, particle physics must be open to completely unexpected discoveries, and that is reason enough to extend the reach of searches for ultra-high energy (uhe) photons. the observation of a population of photons with energies e ≳ 100 eev would for example imply the existence of either a completely new physical phenomena, or particle acceleration mechanisms heretofore never seen or imagined. but as we outline in this letter of interest, there are also good arguments for super-heavy dark matter (shdm) in a parameter range such that it could be discovered via its decays to, in particular, uhe photons. only ultra-high energy cosmic ray observatories have capabilities to detect uhe photons. we first investigate how current and future observations can probe and constrain shdm models in important directions, and then outline some of the scenarios that motivate such searches. we also discuss connections between constraints on shdm and on the parameter values of cosmological models. | hunting super-heavy dark matter with ultra-high energy photons |
recent observations by the alpha magnetic spectrometer (ams-02) have tentatively detected a handful of cosmic-ray antihelium events. such events have long been considered as smoking-gun evidence for new physics, because astrophysical antihelium production is expected to be negligible. however, the dark-matter-induced antihelium flux is also expected to fall below current sensitivities, particularly in light of existing antiproton constraints. here, we demonstrate that a previously neglected standard model process—the production of antihelium through the displaced-vertex decay of λ¯b-baryons—can significantly boost the dark matter induced antihelium flux. this process can entirely dominate the production of high-energy antihelium nuclei, increasing the rate of detectable ams-02 events by 2 orders of magnitude. | dark matter annihilation can produce a detectable antihelium flux through λ¯b decays |
context. supernova remnants (snrs) are known to accelerate particles to relativistic energies, on account of their nonthermal emission. the observational progress from radio to gamma-ray observations reveals more and more morphological features that need to be accounted for when modeling the emission from those objects.aims: we use our time-dependent acceleration code ratpac to study the formation of extended gamma-ray halos around supernova remnants and the morphological implications that arise when the high-energetic particles start to escape from the remnant.methods: we performed spherically symmetric 1d simulations in which we simultaneously solved the transport equations for cosmic rays, magnetic turbulence, and the hydrodynamical flow of the thermal plasma in a volume large enough to keep all cosmic rays in the simulation. the transport equations for cosmic rays and magnetic turbulence were coupled via the cosmic-ray gradient and the spatial diffusion coefficient of the cosmic rays, while the cosmic-ray feedback onto the shock structure can be ignored. our simulations span 25 000 yr, thus covering the free-expansion and the sedov-taylor phase of the remnant's evolution.results: we find a strong difference in the morphology of the gamma-ray emission from supernova remnants at later stages dependent on the emission process. at early times, both the inverse-compton and the pion-decay morphology are shell-like. however, as soon as the maximum-energy of the freshly accelerated particles starts to fall, the inverse-compton morphology starts to become center-filled, whereas the pion-decay morphology keeps its shell-like structure. escaping high-energy electrons start to form an emission halo around the remnant at this time. there are good prospects for detecting this spectrally hard emission with the future cerenkov telescope array, as there are for detecting variations in the gamma-ray spectral index across the interior of the remnant. further, we find a constantly decreasing nonthermal x-ray flux that makes a detection of x-ray unlikely after the first few thousand years of the remnants' evolution. the radio flux is increasing throughout the snr's lifetime and changes from a shell-like to a more center-filled morphology later on. | morphology of supernova remnants and their halos |
clusters of galaxies can potentially produce cosmic rays (crs) up to very high energies via large-scale shocks and turbulent acceleration. due to their unique magnetic-field configuration, crs with energy ≤1017 ev can be trapped within these structures over cosmological time-scales, and generate secondary particles, including neutrinos and gamma rays, through interactions with the background gas and photons. in this work, we compute the contribution from clusters of galaxies to the diffuse neutrino background. we employ 3d cosmological magnetohydrodynamical simulations of structure formation to model the turbulent intergalactic medium. we use the distribution of clusters within this cosmological volume to extract the properties of this population, including mass, magnetic field, temperature, and density. we propagate crs in this environment using multidimensional monte carlo simulations across different redshifts (from z ~ 5 to z = 0), considering all relevant photohadronic, photonuclear, and hadronuclear interaction processes. we find that, for crs injected with a spectral index α = 1.5-2.7 and cutoff energy emax = 1016-5 × 1017 ev, clusters contribute to a sizeable fraction to the diffuse flux observed by the icecube neutrino observatory, but most of the contribution comes from clusters with m ≳ 1014 m⊙ and redshift z ≲ 0.3. if we include the cosmological evolution of the cr sources, this flux can be even higher. | high-energy neutrino production in clusters of galaxies |
apart from its anomalously large depth, the cosmological 21-cm absorption signal measured by the edges collaboration also has a shape that is distinctly different from theoretical predictions. models with non-traditional components such as super-adiabatic baryonic cooling or an excess radio background (erb) explain the depth of the observed profile, but still conspicuously fail to explain its shape. in this paper, we quantify the requirements imposed by the edges measurement on sources of ly α and x-ray photons in the presence of erb at cosmic dawn. in extreme cases, the ly α and x-ray emissivities require to be enhanced by up to an order of magnitude relative to traditional models. furthermore, this enhancement needs to be active only for a short duration. we find that under conventional assumptions for the cosmic star formation rate density (sfrd), standard stellar populations are incapable of meeting these conditions. only highly unusual models of massive metal-free stars seem to provide a possible mechanism. conversely, if the sources of ly α and x-ray photons are compelled to have standard properties, the edges measurement puts strong demands on the cosmic sfrd. this provides interesting falsifiable predictions for high-redshift galaxy surveys enabled by the james webb space telescope (jwst). we derive predictions for galaxy uv luminosity functions and number densities, and show that a deep jwst survey with a limiting uv magnitude of muv, lim = 32 would potentially be able to rule out the predictions enforced by the edges measurement. | implications of the cosmological 21-cm absorption profile for high-redshift star formation and deep jwst surveys |
the local cosmic ray (cr) energy spectrum exhibits a spectral softening at energies around 3 pev. sources which are capable of accelerating hadrons to such energies are called hadronic pevatrons. however, hadronic pevatrons have not yet been firmly identified within the galaxy. several source classes, including galactic supernova remnants (snrs), have been proposed as pevatron candidates. the potential to search for hadronic pevatrons with the cherenkov telescope array (cta) is assessed. the focus is on the usage of very high energy γ-ray spectral signatures for the identification of pevatrons. assuming that snrs can accelerate crs up to knee energies, the number of galactic snrs which can be identified as pevatrons with cta is estimated within a model for the evolution of snrs. additionally, the potential of a follow-up observation strategy under moonlight conditions for pevatron searches is investigated. statistical methods for the identification of pevatrons are introduced, and realistic monte-carlo simulations of the response of the cta observatory to the emission spectra from hadronic pevatrons are performed. based on simulations of a simplified model for the evolution for snrs, the detection of a γ-ray signal from in average 9 galactic pevatron snrs is expected to result from the scan of the galactic plane with cta after 10 h of exposure. cta is also shown to have excellent potential to confirm these sources as pevatrons in deep observations with o(100) hours of exposure per source. | sensitivity of the cherenkov telescope array to spectral signatures of hadronic pevatrons with application to galactic supernova remnants |
we examine the physical conditions, environments, and statistical properties of intergalactic ovi, ovii and oviii absorbers in the simba cosmological hydrodynamic simulation suite. the goal is to understand the nature of these high ionisation absorbers, and test simba's surprising prediction that $\sim 70\%$ of cosmic baryons at $z=0$ are in the warm-hot intergalactic medium (whim) driven by jet feedback from active galactic nuclei (agn). by comparing a full-physics simba run versus one with jets turned off, we find that jet feedback causes widespread heating that impacts the absorption morphology particularly of the higher ions. however, the distribution of the physical properties of detectable absorbers are not dramatically affected. higher ionisation absorbers probe hotter gas as expected, but in simba all ions arise at similar overdensities (typically $\delta\sim20-30$), similar environments (predominantly filaments), and similar nearest-halo distances (typically $\sim2-3r_{200c}$). simba matches the observed ovi column density distribution function (cddf) fairly well, but under-predicts the cddf preliminarily derived from two detected intergalactic ovii absorbers. predicted cddfs are very similar at $z=1$ with or without jets, but show differences by $z=0$ particularly at the high-column end. despite some discrepancies, simba reproduces available observations as well as or better than other comparable simulations, suggesting that simba's widespread jet heating cannot be ruled out by these data. these results offer hope that future x-ray and ultraviolet facilities could provide significant constraints on galactic feedback models from high-ionisation igm metal absorbers. | high-ionisation oxygen absorption from the warm-hot intergalactic medium in simba |
an estimate of the expected photon flux above 1017 ev from the interactions of ultra-high-energy cosmic rays with the matter in the galactic disk is presented. uncertainties arising from the distribution of the gas in the disk, the absolute level of the cosmic-ray flux, and the composition of the cosmic rays are taken into account. within these uncertainties, the integrated photon flux above 1017 ev is averaged out over galactic latitude less than 5°, between ≃3.2 × 10-2 km-2 yr-1 sr-1 and ≃8.7 × 10-2 km-2 yr-1 sr-1. the all-sky average value amounts to ≃1.1 ×10-2 km-2 yr-1 sr-1 above 1017 ev and decreases roughly as e -2, making this diffuse flux the dominant one from cosmic-ray interactions for energy thresholds between 1017 and 1018 ev. compared to the current sensitivities of detection techniques, a gain of between two and three orders of magnitude in exposure is required for a detection below ≃1018 ev. the implications for searches for photon fluxes from the galactic center that would be indicative of the decay of super-heavy dark matter particles are discussed, as the photon flux presented in this study can be considered as a floor below which other signals would be overwhelmed. | diffuse flux of ultra-high-energy photons from cosmic-ray interactions in the disk of the galaxy and implications for the search for decaying super-heavy dark matter |
we report the detection of diffuse radio emission which might be connected to a large-scale filament of the cosmic web covering a 8° × 8° area in the sky, likely associated with a z ≈ 0.1 overdensity traced by nine massive galaxy clusters. in this work, we present radio observations of this region taken with the sardinia radio telescope. two of the clusters in the field host a powerful radio halo sustained by violent ongoing mergers and provide direct proof of intracluster magnetic fields. in order to investigate the presence of large-scale diffuse radio synchrotron emission in and beyond the galaxy clusters in this complex system, we combined the data taken at 1.4 ghz with the sardinia radio telescope with higher resolution data taken with the nrao vla sky survey. we found 28 candidate new sources with a size larger and x-ray emission fainter than known diffuse large-scale synchrotron cluster sources for a given radio power. this new population is potentially the tip of the iceberg of a class of diffuse large-scale synchrotron sources associated with the filaments of the cosmic web. in addition, we found in the field a candidate new giant radio galaxy. | observations of a nearby filament of galaxy clusters with the sardinia radio telescope |
the telescope array (ta) experiment is the largest detector to observe ultra-high-energy cosmic rays in the northern hemisphere. the fluorescence detectors at two stations of ta are newly constructed and have now completed seven years of steady operation. one advantage of monocular analysis of the fluorescence detectors is a lower energy threshold for cosmic rays than that of other techniques like stereoscopic observations or coincidences with the surface detector array, allowing the measurement of an energy spectrum covering three orders of magnitude in energy. analyzing data collected during those seven years, we report the energy spectrum of cosmic rays covering a broad range of energies above 1017.2ev measured by the fluorescence detectors and a comparison with previously published results. | the energy spectrum of cosmic rays above 1017.2 ev measured by the fluorescence detectors of the telescope array experiment in seven years |
we examine limits to the energy to which cosmic rays can be accelerated by relativistic shocks, showing that acceleration of light ions as high as 100 eev is unlikely. the implication of our estimates is that if ultrahigh energy cosmic rays are accelerated by shocks, then those shocks are probably not relativistic. | cosmic-ray acceleration by relativistic shocks: limits and estimates |
the radiation environment in space has severely adverse effects on electronic systems. to evaluate radiation sensitivity, electronics are tested on earth with different types of irradiation sources. cosmic rays (cr) are the most difficult to simulate on earth, because cr can have energies up to 10e20 ev, with a flux maximum around 1 gev/nucleon. traditionally these single-event effects of these particles were simulated with heavy ions having energies of only a few mev/nucleon because for "large" devices only the energy loss (often referred to as let) had to be matched. heavy ions of such high energies can produce secondary particles through nuclear interactions which can induce additional ionization that leads to adverse effects. the need to investigate these effects has grown since electronic devices incorporate more and more heavier elements (e.g., cu, w) close to sensitive elements which can have significantly larger nuclear cross sections than in the 1 to 10 mev/nucleon energy regime. at the moment there is a large trend in the space community to increasingly use commercial of the shelf (cots) electronic devices. one of the reasons is that many challenging space applications can only be met with cots devices because there are simply no space qualified devices (often referred to as hirel) available with the necessary performance. another trend in the evolution of si-based microelectronic integrated circuits is to create 3-dimensional structures. there are already commercially available 3d nand-flash devices with several tens of active layers stacked on top of each other. these structures cannot be tested with low energy ions, due to the large depths of the sensitive volumes alone. for radiation tests ion beams are needed that provide constant let over the whole stack (> 128 layers). in addition, e.g. in systems in a package, you find several dies stacked on top of each in a single package. to investigate such afore mentioned device types, the beam has to be able to penetrate through all the dies. | investigating the effects of cosmic rays on space electronics |
cosmic-ray muography uses high-energy particles for imaging applications that are produced by cosmic rays in particle showers in the earth's atmosphere. this technology has developed rapidly over the last 15 years, and it is currently branching out into many different applications and moving from academic research to commercial application. as in any new sub-field of research and technology, the nomenclature of the field itself is still developing and has not settled yet as new aspects of the field are appearing and with them the terms to describe them. this overview of the field of muography is not going to focus on the physics, on the reconstruction algorithms or on the involved detector technology. detailed papers on these aspects are included in this issue of philosophical transactions a and i will refer to them. instead, i will give an overview of the field as it is now, in 2018, and try to give an idea of the future directions in this field as i see them. this article is part of the theo murphy meeting issue `cosmic-ray muography'. | muography: overview and future directions |
for the last 30 years, muon experiments at isis pulsed neutron and muon facility at the rutherford appleton laboratory, oxfordshire have been making a significant contribution to a number of scientific fields. the muon facilities at isis consist of eight experimental areas. the european commission muon facility consists of three experimental areas with a fixed momentum (28 mev c-1). the riken-ral facility has a variable momentum (17-90 mev c-1) and a choice of negative or positive muons delivering muons to four experimental areas. there is also an area recently used for a muon ionization cooling experiment. in this paper, the isis pulsed muon facilities are reviewed, including the beam characteristics that could be useful for muography experiments. this article is part of the theo murphy meeting issue `cosmic-ray muography'. | muons at isis |
the problem of the impulsive heating of dust grains in cold, dense interstellar clouds is revisited theoretically with the aim of better understanding the leading mechanisms of the explosive desorption of icy mantles. we rigorously show that if the heating of a reactive medium occurs within a sufficiently localized spot (e.g., the heating of mantles by cosmic rays (crs)), then the subsequent thermal evolution is characterized by a single dimensionless number λ. this number identifies a bifurcation between two distinct regimes: when λ exceeds a critical value (threshold), the heat equation exhibits the explosive solution, i.e., the thermal (chemical) explosion is triggered. otherwise, thermal diffusion causes the deposited heat to spread over the entire grain—this regime is commonly known as whole-grain heating. the theory allows us to find a critical combination of physical parameters that govern the explosion of icy mantles due to impulsive spot heating. in particular, our calculations suggest that heavy cr species (e.g., iron ions) colliding with dust are able to trigger the explosion. based on recently calculated local cr spectra, we estimate the expected rate of explosive desorption. the efficiency of the desorption, which in principle affects all solid species independent of their binding energy, is shown to be comparable to other cr desorption mechanisms typically considered in the literature. also, the theory allows us to estimate the maximum abundances of reactive species that may be stored in the mantles, which provides important constraints on the available astrochemical models. | impulsive spot heating and thermal explosion of interstellar grains revisited |
the accuracy and precision of the cosmic-ray neutron sensor (crns) neutron count and soil moisture estimate are affected differently by distinct neutron moderating factors. moreover, whereas the accuracy can be improved by correcting for different hydrogen pools, the precision can only be improved by increasing the surface area of the crns sensors or by increasing the integration time. to date, the effects of different neutron moderating factors on crns accuracy and precision are not completely understood. we used data from three agricultural and low biomass sites located within a few kilometres distance from each other in south england. we developed an extended version of the cosmic-ray soil moisture interaction code (cosmic), which included the effects of relevant neutron moderating factors on the neutron counts. with sensitivity analysis, we found atmospheric pressure and soil moisture content to be most influential on neutron count accuracy and precision. these two factors were, respectively, seven and four times more important than soil bulk density, lattice water and soil organic matter. above ground biomass was substantially less influential compared to these variables. however, because the three sites had similar soil organic matter and meteorology, calibration results showed that differences between sites could be mostly explained by differences in above ground biomass and to a lesser extent intercepted water. the neutron count differences due to above ground biomass corresponded with substantial soil moisture estimate differences up to ; a significant effect on soil moisture accuracy. the precision of the soil moisture estimate was 10 times more sensitive to soil moisture than other factors and was therefore mostly a function of soil moisture content itself. the neutron count integration times required to obtain a soil moisture precision were typically less than a day. our results are indicative for other humid, temperate, agricultural sites. | accuracy and precision of the cosmic-ray neutron sensor for soil moisture estimation at humid environments |
from data recently reported from the icecube telescope, we derive new bounds on the monochromatic neutrino signal produced from dark matter particle decays. in the few tev to tens of tev energy range, these bounds turn out to be better than previous limits by more than an order of magnitude. as a result, intensity constraints on neutrino lines at energies above a few tev are now comparable to those on gamma-ray lines. from the same data sample, we also perform a detailed search for a neutrino line, showing that there is no significant hint for such a signal. | new search for monochromatic neutrinos from dark matter decay |
increased electron density in the ionosphere due to photoionization by radiation emitted during a solar x-ray flare impacts high-frequency (hf) radio wave propagation. shortwave fadeout (swf) due to the enhanced d region absorption that results is characterized by the level of cosmic radio noise attenuation derived from riometer measurements. swf impacts hf radio propagation and has been identified in the super dual auroral radar network (superdarn) data. an x2.1 solar x-ray flare that erupted on 11 march 2015 is examined to determine its effects on hf radio propagation. riometer data indicate a sharp enhancement in absorption, which falls off with increasing solar zenith angle. superdarn radars observed a suppression of both ground scatter and ionospheric echoes. ground scatter data indicated a rapid weakening of signal from far to near ranges followed by a 20-min interval of complete signal loss. recovery lasted 30 min and proceeded from near to far ranges. prior to the complete signal loss, an apparent sharp velocity impulse (doppler flash) lasting 1-2 min was observed in the ground scatter data. the peak of this flash preceded the onset of enhanced absorption. the onset of signal loss by superdarn preceded the onset of enhanced absorption observed by riometers. both data sets observed a positive correlation between increasing delay in onset and increasing solar zenith angle with onset progressing at an average rate of 16.7°/min (0.060 min/°). agreement between riometer and superdarn indicates the possibility of using a joint data set for improved monitoring of the space weather impact of solar x-ray flares. | examining the potential of the super dual auroral radar network for monitoring the space weather impact of solar x-ray flares |
the giant molecular clouds (mcs) found in the milky way and similar galaxies play a crucial role in the evolution of these systems. the supernova explosions that mark the death of massive stars in these regions often lead to interactions between the supernova remnants (snrs) and the clouds. these interactions have a profound effect on our understanding of snrs. shocks in snrs should be capable of accelerating particles to cosmic ray (cr) energies with efficiencies high enough to power galactic crs. x-ray and γ-ray studies have established the presence of relativistic electrons and protons in some snrs and provided strong evidence for diffusive shock acceleration as the primary acceleration mechanism, including strongly amplified magnetic fields, temperature and ionization effects on the shock-heated plasmas, and modifications to the dynamical evolution of some systems. because protons dominate the overall energetics of the crs, it is crucial to understand this hadronic component even though electrons are much more efficient radiators and it can be difficult to identify the hadronic component. however, near mcs the densities are sufficiently high to allow the γ-ray emission to be dominated by protons. thus, these interaction sites provide some of our best opportunities to constrain the overall energetics of these particle accelerators. here we summarize some key properties of interactions between snrs and mcs, with an emphasis on recent x-ray and γ-ray studies that are providing important constraints on our understanding of cosmic rays in our galaxy. | supernova remnants interacting with molecular clouds: x-ray and gamma-ray signatures |
axion-like particles (alps) are attracting increasing interest since, among other things, they are a prediction of many extensions of the standard model of elementary particles physics and in particular of superstrings and superbranes. alps are very light, neutral, pseudo-scalar bosons which are supposed to interact with two photons. for their mass ma ≪ 1 ev and two-photon coupling gγγa in a suitable range they can give rise to very interesting astrophysical effects taking place in the x- and γ-ray bands. specifically, throughout the present paper we are concerned with photon-alp oscillations in the very-high-energy band (vhe , 100 gev ≲ e ≲ 100 tev) and beyond, which ought to occur in the photon beam emitted by far-away blazars and are triggered by the domain-like random extragalactic magnetic field bext. because of the presence of the extragalactic background light (ebl) - which is the infrared/optical/ultraviolet radiation emitted by all galaxies during the cosmic evolution - when a vhe photon scatters off an ebl photon an e+e- pair can be created, which causes a rather strong dimming of the source. in the presence of photon-alp oscillation things are different, since a photon travels sometimes as a true photon and sometimes as an alp. since alps do not interact with the ebl, the effective optical depth is somewhat reduced. but - as a consequence - the photon survival probability gets strongly enhanced with respect to the prediction of conventional physics, thereby greatly increasing the photon transparency in the vhe band so that the corresponding horizon gets enlarged to a considerable extent. while all this is well known and already studied in detail (de angelis et al., 2011, 2013a), the new effect of photon dispersion on the cosmic microwave background (cmb) becomes very important at high enough energies. the aim of the present paper is to take it systematically into account. actually, two widely different energy scales are associated with it. one is eh = o (5 tev) , above which the effect in question starts to become dominant and makes the single random realizations of the beam propagation process - the only ones that are observable - to exhibit small energy oscillations: this is a crucial prediction of our model. the other energy scale is eeq above which the oscillation length becomes smaller than the coherence length of bext: typically eeq = o (40 tev) with a large uncertainty. thus, previously used domain-like models of bext would generally give wrong results above eeq and a more realistic model for bext becomes compelling, like the one very recently developed by the authors. remarkably, we have been able to derive the corresponding photon survival probability pγ→γalp (e0 , z)analytically and exactly up to observed energies e0 = 1000 tev and redshift up to z = 2, a fact that drastically shortens the computation time in the derivation of the results presented in this paper. specifically, for 7 simulated blazars we exhibit the plots of the pγ→γalp (e0 , z) along 1000 random realizations versus e0, for different values of z and four values of the model parameters. our predictions can be tested by the new generation of γ-ray observatories like cta, hawc, gamma-400, lhaaso, taiga-hiscore and herd. finally, for our guessed values of ma and gγγa our alp can be detected in the upgrade of alps ii at desy, the planned experiments iaxo, stax and abracadabra as well as with other techniques developed by avignone and collaborators. | extragalactic photon-axion-like particle oscillations up to 1000 tev |
answers to the metal production of the universe can be found in galaxy clusters, notably within their intra-cluster medium (icm). the x-ray integral field unit (x-ifu) on board the next-generation european x-ray observatory athena (2030s) will provide the necessary leap forward in spatially-resolved spectroscopy required to disentangle the intricate mechanisms responsible for this chemical enrichment. in this paper, we investigate the future capabilities of the x-ifu in probing the hot gas within galaxy clusters. from a test sample of four clusters extracted from cosmological hydrodynamical simulations, we present comprehensive synthetic observations of these clusters at different redshifts (up to z ≤ 2) and within the scaled radius r500 performed using the instrument simulator sixte. through 100 ks exposures, we demonstrate that the x-ifu will provide spatially resolved mapping of the icm physical properties with little to no biases (⪅5%) and well within statistical uncertainties. the detailed study of abundance profiles and abundance ratios within r500 also highlights the power of the x-ifu in providing constraints on the various enrichment models. from synthetic observations out to z = 2, we have also quantified its ability to track the chemical elements across cosmic time with excellent accuracy, and thereby to investigate the evolution of metal production mechanisms as well as the link to the stellar initial mass-function. our study demonstrates the unprecedented capabilities of the x-ifu of unveiling the properties of the icm but also stresses the data analysis challenges faced by future high-resolution x-ray missions such as athena. | athena x-ifu synthetic observations of galaxy clusters to probe the chemical enrichment of the universe |
cosmic-ray electrons and positrons (cres) at gev-tev energies are a unique probe of our local galactic neighborhood. cres lose energy rapidly via synchrotron radiation and inverse-compton scattering processes while propagating within the galaxy, and these losses limit their propagation distance. for electrons with tev energies, the limit is on the order of a kiloparsec. within that distance, there are only a few known astrophysical objects capable of accelerating electrons to such high energies. it is also possible that the cres are the products of the annihilation or decay of heavy dark matter (dm) particles. veritas, an array of imaging air cherenkov telescopes in southern arizona, is primarily utilized for gamma-ray astronomy but also simultaneously collects cres during all observations. we describe our methods of identifying cres in veritas data and present an energy spectrum, extending from 300 gev to 5 tev, obtained from approximately 300 hours of observations. a single power-law fit is ruled out in veritas data. we find that the spectrum of cres is consistent with a broken power law, with a break energy at 710 ±40stat±140syst gev . | measurement of cosmic-ray electrons at tev energies by veritas |
context. cosmic-ray electrons (cres) originating from the star-forming discs of spiral galaxies frequently form extended radio haloes that are best observable in edge-on galaxies, where their properties can be directly investigated as a function of vertical height above the disc.aims: for the present study, we selected two nearby edge-on galaxies from the continuum halos in nearby galaxies - an evla survey (chang-es), ngc 891 and 4565, which differ largely in their detectable halo extent and their star-formation rates (sfrs). our aim is to figure out how such differences are related to the (advective and/or diffusive) cre transport in the disc and in the halo.methods: we use wide-band 1.5 and 6 ghz very large array (vla) observations obtained in the b, c, and d configurations, and combine the 6 ghz images with effelsberg observations to correct for missing short spacings. after subtraction of the thermal emission, we investigate the spatially resolved synchrotron spectral index distribution in terms of cre spectral ageing. we further compute total magnetic field strengths assuming equipartition between the cosmic-ray (cr) energy density and the magnetic field, and measure synchrotron scale heights at both frequencies. based on the fitted vertical profiles of the synchrotron intensity and on the spectral index profile between 1.5 and 6 ghz, we create purely advective and purely diffusive cre transport models by numerically solving the 1d diffusion-loss equation. in particular, we investigate for the first time the radial dependence of synchrotron and magnetic field scale heights, advection speeds, and diffusion coefficients, whereas previous studies of these two galaxies only determined global values of these quantities.results: we find that the overall spectral index distribution of ngc 891 is mostly consistent with continuous cre injection. in ngc 4565, many of the local synchrotron spectra (even in the disc) feature a break between 1.5 and 6 ghz and are thus more in line with discrete-epoch cre injection (jaffe-perola (jp) or kardashev-pacholczyk (kp) models). this implies that cre injection time-scales are lower than the synchrotron cooling time-scales. the synchrotron scale height of ngc 891 increases with radius, indicating that synchrotron losses are significant. ngc 891 is probably dominated by advective cre transport at a velocity of ≳150 km s-1. in contrast, ngc 4565 is diffusion-dominated up to z = 1 kpc or higher, with a diffusion coefficient of ≥2 × 1028 cm2 s-1. reduced images (fits) are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/632/a12 based on observations with the 100-m telescope of the max-planck-institut für radioastronomie (mpifr) at effelsberg and the karl g. jansky very large array (vla) operated by the nrao. the nrao is a facility of the national science foundation operated under agreement by associated universities, inc. | chang-es. xvi. an in-depth view of the cosmic-ray transport in the edge-on spiral galaxies ngc 891 and ngc 4565 |
we study the propagation of ultrahigh-energy cosmic rays in the magnetized cosmic web. we focus on the particular case of highly magnetized voids (b ∼ng ), using the upper bounds from the planck satellite. the cosmic web was obtained from purely magnetohydrodynamical cosmological simulations of structure formation considering different power spectra for the seed magnetic field in order to account for theoretical uncertainties. we investigate the impact of these uncertainties on the propagation of cosmic rays, showing that they can affect the measured spectrum and composition by up to ≃80 % and ≃5 %, respectively. in our scenarios, even if magnetic fields in voids are strong, deflections of 50 eev protons from sources closer than ∼50 mpc are less than 15° in approximately 10-50% of the sky, depending on the distribution of sources and magnetic power spectrum. therefore, uhecr astronomy might be possible in a significant portion of the sky depending on the primordial magnetic power spectrum, provided that protons constitute a sizeable fraction of the observed uhecr flux. | implications of strong intergalactic magnetic fields for ultrahigh-energy cosmic-ray astronomy |
the dark matter particle explorer (dampe) is a general purpose satellite-borne high energy γ - ray and cosmic ray detector. among the scientific objectives of dampe are the search for the origin of cosmic rays and an understanding of the dark matter particles. as one of the four detectors in dampe, the plastic scintillator detector (psd) plays an important role in the particle charge measurement and the photons/electrons discrimination. it can identify the atomic number z/charge states of relativistic ions from h to fe and the detection efficiency for z = 1 particles can reach 0.9999. the psd has been working reliably since the successfully launching of dampe on december 17, 2015. in this paper, the design, assembly, qualification tests of the psd and some of the performance measured on the ground are presented in detail. | the plastic scintillator detector for dampe |
in this paper, we report the production cross-section of forward photons in the pseudorapidity regions of η > 10.94 and 8.99 > η > 8.81, measured by the lhcf experiment with proton-proton collisions at √{ s } = 13tev. the results from the analysis of 0.191nb-1 of data obtained in june 2015 are compared to the predictions of several hadronic interaction models that are used in air-shower simulations for ultra-high-energy cosmic rays. although none of the models agree perfectly with the data, epos-lhc shows the best agreement with the experimental data among the models. | measurement of forward photon production cross-section in proton-proton collisions at √{ s } = 13tev with the lhcf detector |
we present molecular spectroscopy toward 50 galactic supernova remnants (snrs) taken at millimeter wavelengths in 12co j = 2 - 1. these observations are part of a systematic survey for broad molecular line (bml) regions indicative of interactions with molecular clouds (mcs). we detected bml regions toward 19 snrs, including 9 newly identified bml regions associated with snrs (g08.3-0.0, g09.9-0.8, g11.2-0.3, g12.2+0.3, g18.6-0.2, g23.6+0.3, 4c-04.71, g29.6+0.1, and g32.4+0.1). the remaining 10 snrs with bml regions confirm previous evidence for mc interaction in most cases (g16.7+0.1, kes 75, 3c 391, kes 79, 3c 396, 3c 397, w49b, cas a, and ic 443), although we confirm that the bml region toward hb 3 is associated with the w3(oh) h ii region, not the snr. based on the systemic velocity of each mc, molecular line diagnostics, and cloud morphology, we test whether these detections represent snr-mc interactions. one of the targets (g54.1+0.3) had previous indications of a bml region, but we did not detect broadened emission toward it. although broadened 12co j = 2 - 1 line emission should be detectable toward virtually all snr-mc interactions, we find relatively few examples; therefore, the number of interactions is low. this result favors mechanisms other than supernova feedback as the basic trigger for star formation. in addition, we find no significant association between tev gamma-ray sources and mc interactions, contrary to predictions that snr-mc interfaces are the primary venues for cosmic ray acceleration. | a systematic survey for broadened co emission toward galactic supernova remnants |
we present weak lensing and x-ray analysis of 12 low-mass clusters from the canada-france-hawaii telescope lensing survey and xmm-cfhtls surveys. we combine these systems with high-mass systems from canadian cluster comparison project and low-mass systems from cosmic evolution survey to obtain a sample of 70 systems, spanning over two orders of magnitude in mass. we measure core-excised lx-tx, m-lx and m-tx scaling relations and include corrections for observational biases. by providing fully bias-corrected relations, we give the current limitations for lx and tx as cluster mass proxies. we demonstrate that tx benefits from a significantly lower intrinsic scatter at fixed mass than lx. by studying the residuals of the bias-corrected relations, we show for the first time using weak lensing masses that galaxy groups seem more luminous and warmer for their mass than clusters. this implies a steepening of the m-lx and m-tx relations at low masses. we verify the inferred steepening using a different high-mass sample from the literature and show that variance between samples is the dominant effect leading to discrepant scaling relations. we divide our sample into subsamples of merging and relaxed systems, and find that mergers may have enhanced scatter in lensing measurements, most likely due to stronger triaxiality and more substructure. for the lx-tx relation, which is unaffected by lensing measurements, we find the opposite trend in scatter. we also explore the effects of x-ray cross-calibration and find that chandra calibration leads to flatter lx-tx and m-tx relations than xmm-newton. | cfhtlens: weak lensing calibrated scaling relations for low-mass clusters of galaxies |
context. barnard b1b has been revealed as one of the most interesting globules from the chemical and dynamical point of view. it presents a rich molecular chemistry characterized by large abundances of deuterated and complex molecules. furthermore, this globule hosts an extremely young class 0 object and one candidate for the first hydrostatic core (fhsc) proving the youth of this star-forming region.aims: our aim is to determine the cosmic ray ionization rate, ζh2, and the depletion factors in this extremely young star-forming region. these parameters determine the dynamical evolution of the core.methods: we carried out a spectral survey toward barnard 1b as part of the iram large program "iram chemical survey of sun-like star-forming regions" (asai) using the iram 30-m telescope at pico veleta (spain). this provided a very complete inventory of neutral and ionic c-, n-, and s- bearing species with, from our knowledge, the first secure detections of the deuterated ions dcs+ and doco+. we use a state-of-the-art pseudo-time-dependent gas-phase chemical model that includes the ortho and para forms of h2, h, d, h, h2d+, d2h+, d2, and d to determine the local value of the cosmic ray ionization rate and the depletion factors.results: our model assumes n(h2) = 105 cm-3 and tk = 12 k, as derived from our previous works. the observational data are well fitted with ζh2 between 3 × 10-17 s-1 and 10-16 s-1 and the elemental abundances o/h = 3 × 10-5, n/h = 6.4-8 × 10-5, c/h = 1.7 × 10-5, and s/h between 6.0 × 10-7 and 1.0 × 10-6. the large number of neutral/protonated species detected allows us to derive the elemental abundances and cosmic ray ionization rate simultaneously. elemental depletions are estimated to be ~10 for c and o, ~1 for n, and ~25 for s.conclusions: barnard b1b presents similar depletions of c and o as those measured in prestellar cores. the depletion of sulfur is higher than that of c and o, but not as extreme as in cold cores. in fact, it is similar to the values found in some bipolar outflows, hot cores, and photon-dominated regions. several scenarios are discussed to account for these peculiar abundances. we propose that it is the consequence of the initial conditions (important outflows and enhanced uv fields in the surroundings) and a rapid collapse (~0.1 myr) that allows most s- and n-bearing species to remain in the gas phase to great optical depths. the interaction of the compact outflow associated with b1b-s with the surrounding material could enhance the abundances of s-bearing molecules, as well. | ionization fraction and the enhanced sulfur chemistry in barnard 1 |
the origin of tiny neutrino mass is an unsolved puzzle leading to a variety of phenomenological aspects beyond the standard model (bsm). among several interesting attempts, $u(1)$ gauge extension of standard model (sm) is a simple and interesting set-up where the so-called seesaw mechanism is incarnated by the addition of three generations of right-handed neutrinos followed by the breaking of $u(1)$ and electroweak symmetries. such scenarios are anomaly free in nature appearing with a neutral bsm gauge boson ($z^\prime$). in addition to that, there comes another open question regarding the existence of a non-luminous, hitherto unidentified object called dark matter (dm) originating from the measurement of its relic density. to explore properties of $z^\prime$, we focus on chiral and flavored scenarios where $z^\prime-$neutrinos interaction could be probed in the context of cosmic explosions like gamma-ray burst (grb221009a, so far the highest energy), blazar (txs 0506+056) and active galaxy (ngc1068) respectively. the neutrino antineutrino annihilation produces electron-positron pair which could energize grb through energy deposition. taking the highest energy grb under consideration and estimating the energy deposition rates we constrain $z^\prime$ mass $(m_{z^\prime})$ and the additional $u(1)$ coupling $(g_x)$ for chiral and flavored scenarios in the schwarzchild, hartle-thorne and modified gravity frameworks. on the other hand, adding viable and alternative dm candidates in these models we study neutrino-dm scattering mediated by $z^\prime$ in the $t-$ channel and estimate constraints on $g_x-m_{z^\prime}$ plane using observed data of high energy neutrinos from cosmic blazar and active galaxy at the icecube experiment. we compare our results with bounds obtained from different scattering, beam-dump and $g-2$ experiments. | probing chiral and flavored $z^\\prime$ from cosmic bursts through neutrino interactions |
future dedicated radio interferometers, including hera and ska, are very promising tools that aim to study the epoch of reionization and beyond via measurements of the 21 cm signal from neutral hydrogen. dark matter (dm) annihilations into charged particles change the thermal history of the universe and, as a consequence, affect the 21 cm signal. accurately predicting the effect of dm strongly relies on the modeling of annihilations inside halos. in this work, we use up-to-date computations of the energy deposition rates by the products from dm annihilations, a proper treatment of the contribution from dm annihilations in halos, as well as values of the annihilation cross section allowed by the most recent cosmological measurements from the planck satellite. given current uncertainties on the description of the astrophysical processes driving the epochs of reionization, x-ray heating and lyman-α pumping, we find that disentangling dm signatures from purely astrophysical effects, related to early-time star formation processes or late-time galaxy x-ray emissions, will be a challenging task. we conclude that only annihilations of dm particles with masses of ~100 mev, could leave an unambiguous imprint on the 21 cm signal and, in particular, on the 21 cm power spectrum. this is in contrast to previous, more optimistic results in the literature, which have claimed that strong signatures might also be present even for much higher dm masses. additional measurements of the 21 cm signal at different cosmic epochs will be crucial in order to break the strong parameter degeneracies between dm annihilations and astrophysical effects and undoubtedly single out a dm imprint for masses different from ~100 mev. | the 21 cm signal and the interplay between dark matter annihilations and astrophysical processes |
we use a cosmology-independent method to calibrate gamma-ray burst (grb) from the observational hubble data (ohd) with the cosmic chronometer method. by using gaussian process to reconstruct ohd, we calibrate the amati relation (ep-eiso) to construct a grb hubble diagram with the a118 data set, and constrain dark energy models in a flat space with the markov chain monte carlo numerical method. with the cosmology-independent grbs at 1.4 < z ≤ 8.2 in the a118 data set and the pantheon sample of type ia supernovae at 0.01 < z ≤ 2.3, we obtained ωm = $0.379^{+0.033}_{-0.024}$, h = $0.701^{+0.0035}_{-0.0035}$, w = $-1.25^{+0.14}_{-0.12}$, and wa = $-0.84^{+0.81}_{-0.38}$ for the flat chevallier-polarski-linder model at the 1σ confidence level. we find no significant evidence supporting deviations from the standard lambda cold dark matter model. | testing dark energy models with gamma-ray bursts calibrated from the observational h(z) data through a gaussian process |
the world largest exposure to ultra-high energy cosmic rays accumulated by the pierre auger observatory led to major advances in our understanding of their properties, but the many unknowns about the nature and distribution of the sources, the primary composition and the underlying hadronic interactions prevent the emergence of a uniquely consistent picture. the new perspectives opened by the current results call for an upgrade of the observatory, whose main aim is the collection of new information about the primary mass of the highest energy cosmic rays on a shower-by-shower basis. the evaluation of the fraction of light primaries in the region of suppression of the flux will open the window to charged particle astronomy, allowing for compositionselected anisotropy searches. in addition, the properties of multiparticle production will be studied at energies not covered by man-made accelerators and new or unexpected changes of hadronic interactions will be searched for. after a discussion of the motivations for upgrading the pierre auger observatory, a description of the detector upgrade is provided. we then discuss the expected performances and the improved physics sensitivity of the upgraded detectors and present the first data collected with the already running engineering array. | augerprime: the pierre auger observatory upgrade |
we present a search for magnetically broadened gamma-ray emission around active galactic nuclei (agns), using veritas observations of seven hard-spectrum blazars. a cascade process occurs when multi-tev gamma-rays from an agn interact with extragalactic background light (ebl) photons to produce electron-positron pairs, which then interact with cosmic microwave background photons via inverse-compton scattering to produce gamma-rays. due to the deflection of the electron-positron pairs, a non-zero intergalactic magnetic field (igmf) would potentially produce detectable effects on the angular distribution of the cascade emission. in particular, an angular broadening compared to the unscattered emission could occur. through non-detection of angularly broadened emission from 1es 1218+304, the source with the largest predicted cascade fraction, we exclude a range of igmf strengths around 10-14 g at the 95% confidence level. the extent of the exclusion range varies with the assumptions made about the intrinsic spectrum of 1es 1218+304 and the ebl model used in the simulation of the cascade process. all of the sources are used to set limits on the flux due to extended emission. | search for magnetically broadened cascade emission from blazars with veritas |
an intensive reverberation mapping campaign on the seyfert 1 galaxy mrk817 using the cosmic origins spectrograph (cos) on the hubble space telescope (hst) revealed significant variations in the response of the broad uv emission lines to fluctuations in the continuum emission. the response of the prominent uv emission lines changes over a $\sim$60-day duration, resulting in distinctly different time lags in the various segments of the light curve over the 14 months observing campaign. one-dimensional echo-mapping models fit these variations if a slowly varying background is included for each emission line. these variations are more evident in the civ light curve, which is the line least affected by intrinsic absorption in mrk817 and least blended with neighboring emission lines. we identify five temporal windows with distinct emission line response, and measure their corresponding time delays, which range from 2 to 13 days. these temporal windows are plausibly linked to changes in the uv and x-ray obscuration occurring during these same intervals. the shortest time lags occur during periods with diminishing obscuration, whereas the longest lags occur during periods with rising obscuration. we propose that the obscuring outflow shields the ultraviolet broad lines from the ionizing continuum. the resulting change in the spectral energy distribution of the ionizing continuum, as seen by clouds at a range of distances from the nucleus, is responsible for the changes in the line response. | agn storm 2: v. anomalous behavior of the civ light curve in mrk 817 |
we use the full-sky ray-tracing weak lensing simulations to generate 2268 mock catalogues for the subaru hyper suprime-cam (hsc) survey first-year shear catalogue. our mock catalogues take into account various effects as in the real data: the survey footprints, inhomogeneous angular distribution of source galaxies, statistical uncertainties in photometric redshift (photo-z) estimate, variations in the lensing weight, and the statistical noise in galaxy shape measurements including both intrinsic shapes and the measurement errors. we then utilize our mock catalogues to evaluate statistical uncertainties expected in measurements of cosmic shear two-point correlations ξ± with tomographic redshift information for the hsc survey. we develop a quasi-analytical formula for the gaussian sample variance properly taking into account the number of source pairs in the survey footprints. the standard gaussian formula significantly overestimates or underestimates the mock results by 50 per cent level. we also show that different photo-z catalogues or the six disconnected fields, rather than a consecutive geometry, cause variations in the covariance by {∼ } 5{{ per cent}}. the mock catalogues enable us to study the chi-square distribution for ξ±. we find the wider distribution than that naively expected for the distribution with the degrees of freedom of data vector used. finally, we propose a method to include non-zero multiplicative bias in mock shape catalogue and show that the non-zero multiplicative bias can change the effective shape noise in cosmic shear analyses. our results suggest an importance of estimating an accurate form of the likelihood function (and therefore the covariance) for robust cosmological parameter inference from the precise measurements. | mock galaxy shape catalogues in the subaru hyper suprime-cam survey |
recently, a diffuse emission of 1-100 gev γ-rays has been detected from the direction of m31, extending up to 200 kpc from its center. the interpretation of the extended γ-ray emission by the escape of cosmic rays produced in the galactic disk or in the galactic center is problematic. in this paper, we argue that a cosmic-ray origin (either leptonic or hadronic) of the γ-ray emission is possible in the framework of nonstandard cosmic-ray propagation scenarios or is caused by in situ particle acceleration in the galaxy's halo. correspondingly, the halo is powered by the galaxy's nuclear activity or by the accretion of intergalactic gas. if the formation of cosmic-ray halos around galaxies is a common phenomenon, the interactions of cosmic-ray protons and nuclei with the circumgalactic gas surrounding the milky way could be responsible for the isotropic diffuse flux of neutrinos observed by icecube. | giant cosmic-ray halos around m31 and the milky way |
we consider the production of a "fast flux" of hypothetical millicharged particles (mcps) in the interstellar medium. we consider two possible sources induced by cosmic rays: (a) p p →(meson )→(mcp ) , which adds to atmospheric production of mcps, and (b) cosmic-ray upscattering on a millicharged component of dark matter. we notice that the galactic magnetic fields retain mcps for a long time, leading to an enhancement of the fast flux by many orders of magnitude. in both scenarios, we calculate the expected signal for direct dark matter detection aimed at electron recoil. we observe that in scenario (a) neutrino detectors (argoneut and super-kamiokande) still provide superior sensitivity compared to dark matter detectors (xenon1t). however, in scenarios with a boosted dark matter component, the dark matter detectors perform better, given the enhancement of the upscattered flux at low velocities. given the uncertainties, both in the flux generation model and in the actual atomic physics leading to electron recoil, it is still possible that the xenon1t-reported excess may come from a fast mcp flux, which will be decisively tested with future experiments. | millicharged cosmic rays and low recoil detectors |
context. radio active galactic nuclei (agn) are traditionally separated into two fanaroff-riley (fr) type classes, edge-brightened frii sources or edge-darkened fri sources. with the discovery of a plethora of radio agn of different radio shapes, this dichotomy is becoming too simplistic in linking the radio structure to the physical properties of radio agn, their hosts, and their environment.aims: we probe the physical properties and large-scale environment of radio agn in the faintest fr population to date, and link them to their radio structure. we use the vla-cosmos large project at 3 ghz (3 ghz vla-cosmos), with a resolution and sensitivity of 0.″75 and 2.3 μjy beam−1 to explore the fr dichotomy down to μjy levels.methods: we classified objects as fris, friis, or hybrid fri/frii based on the surface-brightness distribution along their radio structure. our control sample was the jet-less/compact radio agn objects (com agn), which show excess radio emission at 3 ghz vla-cosmos exceeding what is coming from star-formation alone; this sample excludes frs. the largest angular projected sizes of fr objects were measured by a machine-learning algorithm and also by hand, following a parametric approach to the fr classification. eddington ratios were calculated using scaling relations from the x-rays, and we included the jet power by using radio luminosity as a probe. furthermore, we investigated their host properties (star-formation ratio, stellar mass, morphology), and we explore their incidence within x-ray galaxy groups in cosmos, and in the density fields and cosmic-web probes in cosmos.results: our sample is composed of 59 friis, 32 fri/friis, 39 fris, and 1818 com agn at 0.03 ≤ z ≤ 6. on average, fr objects have similar radio luminosities (l3 ghz ∼ 1023 w hz−1 sr−1), spanning a range of 1021−26 w hz−1 sr−1, and they lie at a median redshift of z ∼ 1. the median linear projected size of friis is 106.636.9238.2 kpc, larger than that of fri/friis and fris by a factor of 2−3. the com agn have sizes smaller than 30 kpc, with a median value of 1.71.54.7 kpc. the median eddington ratio of friis is 0.0060.0050.007, a factor of 2.5 less than in fris and a factor of 2 higher than in fri/frii. when the jet power is included, the median eddington ratios of frii and fri/frii increase by a factor of 12 and 15, respectively. frs reside in their majority in massive quenched hosts (m* > 1010.5 m⊙), with older episodes of star-formation linked to lower x-ray galaxy group temperatures, suggesting radio-mode agn quenching. regardless of their radio structure, frs and com agn are found in all types and density environments (group or cluster, filaments, field).conclusions: by relating the radio structure to radio luminosity, size, eddington ratio, and large-scale environment, we find a broad distribution and overlap of fr and com agn populations. we discuss the need for a different classification scheme, that expands the classic fr classification by taking into consideration the physical properties of the objects rather than their projected radio structure which is frequency-, sensitivity- and resolution-dependent. this point is crucial in the advent of current and future all-sky radio surveys. tables a.1, c.1-c.4 are only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/648/a102 | fr-type radio sources at 3 ghz vla-cosmos: relation to physical properties and large-scale environment |
we argue that impact velocities between dust grains with sizes of less than ∼0.1 μm in molecular cloud cores are dominated by drift arising from ambipolar diffusion. this effect is due to the size dependence of the dust coupling to the magnetic field and the neutral gas. assuming perfect sticking in collisions up to ≈50 m s-1, we show that this effect causes rapid depletion of small grains, consistent with starlight extinction and ir and microwave emission measurements, both in the core center (n ∼ 106 cm-3) and envelope (n ∼ 104 cm-3). the upper end of the size distribution does not change significantly if only velocities arising from this effect are considered. we consider the impact of an evolved grain-size distribution on the gas temperature, and argue that if the depletion of small dust grains occurs as expected from our model, then the cosmic ray ionization rate must be well below 10-16 s-1 at a number density of 105 cm-3. | rapid elimination of small dust grains in molecular clouds |
we report the direct detection of the kinetic sunyaev-zel'dovich (ksz) effect in galaxy clusters with a 3.5σ significance level. the measurement was performed by stacking the planck map at 217 ghz at the positions of galaxy clusters from the wen-han-liu (whl) catalog. to avoid the cancelation of positive and negative ksz signals, we used the large-scale distribution of the sloan digital sky survey (sdss) galaxies to estimate the peculiar velocities of the galaxy clusters along the line of sight and incorporated the sign in the velocity-weighted stacking of the ksz signals. using this technique, we were able to measure the ksz signal around galaxy clusters beyond 3 × r500. assuming a standard β-model, we also found that the gas fraction within r500 is fgas, 500 = 0.12 ± 0.04 for the clusters with the mass of m500 ∼ 1.0 × 1014 h-1 m⊙. we compared this result to predictions from the magneticum cosmological hydrodynamic simulations as well as other ksz and x-ray measurements, most of which show a lower gas fraction than the universal baryon fraction for the same mass of clusters. our value is statistically consistent with results from the measurements and simulations and also with the universal value within our measurement uncertainty. | direct detection of the kinetic sunyaev-zel'dovich effect in galaxy clusters |
the majority of the ordinary matter in the local universe has been heated by strong structure formation shocks and resides in a largely unexplored hot, diffuse, x-ray emitting plasma that permeates the halos of galaxies, galaxy groups and clusters, and the cosmic web. we propose a next-generation "cosmic web explorer" that will permit a complete and exhaustive understanding of these unseen baryons. this will be the first mission capable to reach the accretion shocks located several times farther than the virial radii of galaxy clusters, and reveal the out-of-equilibrium parts of the intra-cluster medium which are live witnesses to the physics of cosmic accretion. it will also enable a view of the thermodynamics, kinematics, and chemical composition of the circumgalactic medium in galaxies with masses similar to the milky way, at the same level of detail that athena will unravel for the virialized regions of massive galaxy clusters, delivering a transformative understanding of the evolution of those galaxies in which most of the stars and metals in the universe were formed. finally, the proposed x-ray satellite will connect the dots of the large-scale structure by mapping, at high spectral resolution, as much as 100% of the diffuse gas hotter than 106 k that fills the filaments of the cosmic web at low redshifts, down to an over-density of 1, both in emission and in absorption against the ubiquitous cosmic x-ray background, surveying at least 1600 square degrees over 5 years in orbit. this requires a large effective area (∼10 m2 at 1 kev) over a large field of view (∼1 deg2), a megapixel cryogenic microcalorimeter array providing integral field spectroscopy with a resolving power e/δe = 2000 at 0.6 kev and a spatial resolution of 5'' in the soft x-ray band, and a low and stable instrumental background ensuring high sensitivity to faint, extended emission. | voyage through the hidden physics of the cosmic web |
the calorimetric electron telescope (calet), in operation on the international space station since 2015, collected a large sample of cosmic-ray iron over a wide energy interval. in this letter a measurement of the iron spectrum is presented in the range of kinetic energy per nucleon from 10 gev /n to 2.0 tev /n allowing the inclusion of iron in the list of elements studied with unprecedented precision by space-borne instruments. the measurement is based on observations carried out from january 2016 to may 2020. the calet instrument can identify individual nuclear species via a measurement of their electric charge with a dynamic range extending far beyond iron (up to atomic number z =40 ). the energy is measured by a homogeneous calorimeter with a total equivalent thickness of 1.2 proton interaction lengths preceded by a thin (3 radiation lengths) imaging section providing tracking and energy sampling. the analysis of the data and the detailed assessment of systematic uncertainties are described and results are compared with the findings of previous experiments. the observed differential spectrum is consistent within the errors with previous experiments. in the region from 50 gev /n to 2 tev /n our present data are compatible with a single power law with spectral index -2.60 ±0.03 . | measurement of the iron spectrum in cosmic rays from 10 gev /n to 2.0 tev /n with the calorimetric electron telescope on the international space station |
from a theoretical perspective, matter accretion processes around compact objects are highly relevant as they serve as a natural laboratory to test general relativity in the strong field regime. this enables us to validate fundamental concepts such as the no-hair theorem, the cosmic censorship hypothesis, and the existence of alternative solutions to einstein's equations that mimic the effects of black holes. in this study, we analyze the emission spectra of geometrically thick accretion disks, referred to as polish doughnuts, around naked singularities described by the q-metric. to begin, we revisit the construction of equilibrium configurations of magnetized tori in this spacetime and evaluate the role of the deformation parameter over these configurations. once we have systematically studied the disks in this spacetime, we use the osiris code to perform a backward ray-tracing method, resulting in the first simulations of the intensity map and emission profiles of magnetized tori within this metric. furthermore, we validate the effect of both the quadrupole moment and the angular momentum on observable quantities such as flux and intensity for optically thin and thick disks, since for values of q < 0, which correspond to objects with prolate deformation, and which in turn, are constructed with higher values of angular momentum, the emission spectrum exhibits higher intensity than that obtained for schwarzschild's spacetime. hence, we find a first differential feature that distinguishes tori formed around naked singularities from those around static black holes. | synchrotron emitting komissarov torus around naked singularities |
using the publicly available erosita final equatorial depth survey (efeds) data, we detected the stacked x-ray emissions at the position of 463 filaments at a significance of 3.8σ based on the combination of all energy bands. in parallel, we found that the probability of the measurement under the null hypothesis is ∼0.0017. the filaments were identified with galaxies in the sloan digital sky survey survey, ranging from 30 mpc to 100 mpc in length at 0.2 < z < 0.6. the stacking of the filaments was performed with the efeds x-ray count-rate maps in the energy range between 0.4 and 2.3 kev after masking the resolved galaxy groups and clusters and the identified x-ray point sources from the rosat, chandra, xmm-newton, and erosita observations. in addition, diffuse x-ray foreground and background emissions or any residual contribution were removed by subtracting the signal in the region between 10 and 20 mpc from the filament spines. for the stacked signal, we performed an x-ray spectral analysis, which indicated that the signal is associated with a thermal emission. according to a model with the astrophysical plasma emission code for the plasma emission and with a β-model gas distribution with β = 2/3, the detected x-ray signal can be interpreted as emission from hot gas in the filaments with an average gas temperature of 1.0−0.2+0.3 kev and a gas overdensity of 21 ± 5 at the center of the filaments. | x-ray emission from cosmic web filaments in srg/erosita data |
the oscillating light axion field is known as wave dark matter. we propose an lc (inductor-capacitor)-resonance enhanced detection of the narrow band electric signals induced by the axion dark matter using a solenoid magnet facility. we provide full 3d electromagnetic simulation results for the signal electric field. the electric signal is enhanced by the high q -factor of a resonant lc circuit and then amplified and detected by the state-of-the-art cryogenic electrical transport measurement technique. the cryogenic amplifier noise is the dominant noise source in the proposed detection system. we estimate that the detection system can have a promising sensitivity to axion dark matter with mass below 10-6 ev . the projected sensitivities improve with the size of the magnetic field, and the electric signal measurement can be potentially sensitive to the quantum chromodynamics (qcd) axion with ga γ∼10-16 gev-1 around ma∼10-8 ev , with a multimeter scale magnetized region. this limit is around five orders of magnitude below the current constraint from the cosmic rays. | resonant electric probe to axionic dark matter |
in this paper, we investigate the viability of cosmological models featuring a type ii singularity that occurs during the past evolution of the universe. we construct a scenario in which the singularity arises and then constrain the model parameters using observational data from type ia supernovae, cosmic chronometers, and gamma ray bursts. we find that the resulting cosmological models based on scenarios with the past type ii singularity cannot be excluded by kinematical tests using current observations. | are we survivors of the sudden past singularity? |
using a meerkat observation of the galaxy cluster a3562 (a member of the shapley supercluster), we have discovered a narrow, long and straight, very faint radio filament, which branches out at a straight angle from the tail of a radio galaxy located in projection near the core of the cluster. the radio filament spans 200 kpc and aligns with a sloshing cold front seen in the x-rays, staying inside the front in projection. the radio spectral index along the filament appears uniform (within large uncertainties) at α ≃ -1.5. we propose that the radio galaxy is located outside the cold front but dips its tail under the front. the tangential wind that blows there may stretch the radio plasma from the radio galaxy into a filamentary structure. some reacceleration is needed in this scenario to keep the radio spectrum uniform. alternatively, the cosmic-ray electrons from that spot in the tail can spread along the cluster magnetic field lines, straightened by that same tangential flow, via anomalously fast diffusion. our radio filament can provide constraints on this process. we also uncover a compact radio source at the brightest cluster galaxy that is 2-3 orders of magnitude less luminous than those in typical cluster central galaxies-probably an example of a brightest cluster galaxy starved of accretion fuel by gas sloshing. | a candle in the wind: a radio filament in the core of the a3562 galaxy cluster |
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