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detecting the thermal and non-thermal emission from the shocked cosmic gas surrounding large-scale structures represents a challenge for observations, as well as a unique window into the physics of the warm-hot intergalactic medium. in this work, we present synthetic radio and x-ray surveys of large cosmological simulations in order to assess the chances of jointly detecting the cosmic web in both frequency ranges. we then propose best observing strategies tailored for existing (lofar, mwa, and xmm) or future instruments (ska-low and ska-mid, athena, and erosita). we find that the most promising targets are the extreme peripheries of galaxy clusters in an early merging stage, where the merger causes the fast compression of warm-hot gas onto the virial region. by taking advantage of a detection in the radio band, future deep x-ray observations will probe this gas in emission, and help us to study plasma conditions in the dynamic warm-hot intergalactic medium with unprecedented detail. | detecting shocked intergalactic gas with x-ray and radio observations |
we perform general relativistic magnetohydrodynamic and relativistic magnetohydrodynamic simulations of weakly and highly magnetized gamma-ray burst (grb) jets propagating in binary neutron star (bns) merger ejecta. using the simulations, we first find that mixing between the jet and cocoon, which is present in all types of jets, inhibits the formation of subphotospheric collisionless shocks. however, we show that a mild magnetization may lead to the formation of collisionless subshocks, which allow efficient proton acceleration. we consider shear acceleration and diffusive shock acceleration at collimation shocks, internal shocks, shock breakout, and external shocks to provide the first estimate for neutrino and cosmic-ray (cr) signals from self-consistent simulations of grbs in bns mergers. we find that short grbs do not produce detectable neutrino signals with current-day facilities. shock breakout yields ~10 pev neutrinos at viewing angles ~20°, independent of the jet magnetization. however, a neutrino signal from shock breakout is well below the detection limits of current detectors. such a signal would allow a coincident neutrino-γ-ray detection, providing a testable prediction for shock breakout as a neutrino production site. using the numerical modeling that fits gw 170817 afterglow emission, we find that blast waves in bns mergers can account for 5%-10% of the galactic cr luminosity in the pev-eev energy range. based on these estimates, the observed level of cr anisotropy places a constraint on the distance of the latest galactic bns merger to ≲3 kpc. | the role of jet-cocoon mixing, magnetization, and shock breakout in neutrino and cosmic-ray emission from short gamma-ray bursts |
the wide field imager (wfi) is one of two focal plane instruments of the advanced telescope for high-energy astrophysics (athena), esa's next large x-ray observatory, planned for launch in the early 2030s. the current baseline halo orbit is around l2, and the second lagrangian point of the sun-earth system l1 is under consideration. for both potential halo orbits, the radiation environment, solar and cosmic protons, electrons, and he-ions will affect the performance of the instruments. a further critical contribution to the instrument background arises from the unfocused cosmic hard x-ray background. it is important to understand and estimate the expected instrumental background and to investigate measures, such as design modifications or analysis methods, which could improve the expected background level to achieve the challenging scientific requirement (<5 × 10 − 3 counts / cm2 / kev / s at 2 to 7 kev). previous wfi background simulations done in geant4 have been improved by taking into account new information about the proton flux at l2. in addition, the simulation model of the wfi instrument and its surroundings employed in geant4 simulations has been refined to follow the technological development of the wfi camera. | enhanced simulations on the athena/wide field imager instrumental background |
in 2021 august, the fermi large area telescope, h.e.s.s., and magic detected gev and tev γ-ray emission from an outburst of recurrent nova rs ophiuchi. this detection represents the first very high-energy γ-rays observed from a nova, and it opens a new window to study particle acceleration. both h.e.s.s. and magic described the observed γ-rays as arising from a single, external shock. in this paper, we perform detailed, multi-zone modeling of rs ophiuchi's 2021 outburst, including a self-consistent prescription for particle acceleration and magnetic field amplification. we demonstrate that, contrary to previous work, a single shock cannot simultaneously explain rs ophiuchi's gev and tev emission, in particular the spectral shape and distinct light-curve peaks. instead, we put forward a model involving multiple shocks that reproduces the observed γ-ray spectrum and temporal evolution. the simultaneous appearance of multiple distinct velocity components in the nova optical spectrum over the first several days of the outburst supports the presence of distinct shocks, which may arise either from the strong latitudinal dependence of the density of the external circumbinary medium (e.g., in the binary equatorial plane versus the poles) or due to internal collisions within the white dwarf ejecta (which power the γ-ray emission in classical novae). | evidence for multiple shocks from the γ-ray emission of rs ophiuchi |
turbulence is a predominant process for energizing electrons and ions in collisionless astrophysical plasmas, and thus is responsible for shaping their radiative signatures (luminosity, spectra, and variability). to better understand the kinetic properties of a collisionless radiative plasma subject to externally driven turbulence, we investigate particle-in-cell simulations of relativistic plasma turbulence with external inverse compton cooling acting on the electrons. we find that ions continuously heat up while electrons gradually cool down (due to the net effect of radiation), and hence the ion-to-electron temperature ratio ti/te grows in time. we show that ti/te is limited only by the size and duration of the simulations (reaching ${t}_{i}/{t}_{e}\sim {10}^{3}$ ), indicating that there are no efficient collisionless mechanisms of electron-ion thermal coupling. this result has implications for models of radiatively inefficient accretion flows, such as observed in the galactic center and in m87, for which so-called two-temperature plasmas with ${t}_{i}/{t}_{e}\gg 1$ have been invoked to explain their low luminosity. additionally, we find that electrons acquire a quasi-thermal distribution (dictated by the competition of turbulent particle energization and radiative cooling), while ions undergo efficient nonthermal acceleration (acquiring a harder distribution than in equivalent nonradiative simulations). there is a modest nonthermal population of high-energy electrons that are beamed intermittently in space, time, and direction; these beamed electrons may explain rapid flares in certain high-energy astrophysical systems (e.g., in the galactic center). these numerical results demonstrate that extreme two-temperature plasmas can be produced and maintained by relativistic radiative turbulence. | production and persistence of extreme two-temperature plasmas in radiative relativistic turbulence |
some seyfert galaxies are detected in high-energy gamma rays, but the mechanism and site of gamma-ray emission are unknown. also, the origins of the cosmic high-energy neutrino and mev gamma-ray backgrounds have been veiled in mystery since their discoveries. we propose emission from stellar-mass bhs (sbhs) embedded in disks of active galactic nuclei as their possible sources. these sbhs are predicted to launch jets due to the blandford-znajek mechanism, which can produce intense electromagnetic, neutrino, and cosmic-ray emissions. we investigate whether these emissions can be the sources of cosmic high-energy particles. we find that emission from internal shocks in the jets can explain gamma rays from nearby radio-quiet seyfert galaxies including ngc 1068, if the lorentz factor of the jets (γj) is high. on the other hand, for moderate γj, the emission can significantly contribute to the background gamma-ray and neutrino intensities in the ~mev and ≲pev bands, respectively. furthermore, for moderate γj with efficient amplification of the magnetic field and cosmic-ray acceleration, the neutrino emission from ngc 1068 and the ultrahigh-energy cosmic rays can be explained. these results suggest that the neutrino flux from ngc 1068 as well as the background intensities of mev gamma rays, neutrinos, and the ultrahigh-energy cosmic rays can be explained by a unified model. future mev gamma-ray satellites will test our scenario for neutrino emission. | high-energy electromagnetic, neutrino, and cosmic-ray emission by stellar-mass black holes in disks of active galactic nuclei |
the recent detection of high-energy neutrinos by icecube in the direction of the nearby seyfert/starburst galaxy ngc 1068 implies that radio-quiet active galactic nuclei can accelerate cosmic-ray ions. dedicated multimessenger analyses suggest that the interaction of these high-energy ions with ambient gas or photons happens in a region of the galaxy that is highly opaque for gev-tev gamma rays. otherwise, the gev-tev emission would violate existing constraints provided by the fermi large area telescope (lat) and the major atmospheric gamma imaging cherenkov. the conditions of high optical depth are realized near the central supermassive black hole (smbh). at the same time, the gev emission detected by the fermi lat is likely related to the galaxy's sustained star formation activity. in this work, we derive a 20 mev-1 tev spectrum of ngc 1068 using 14 yr of fermi lat observations. we find that the starburst hadronic component is responsible for ngc 1068's emission above ~500 mev. however, below this energy, an additional component is required. in the 20-500 mev range, the fermi lat data are consistent with hadronic emission initiated by non-thermal ions interacting with gas or photons in the vicinity of the central smbh. this highlights the importance of the mev band to discover hidden cosmic-ray accelerators. | disentangling the hadronic components in ngc 1068 |
the transport of high-energy particles in the presence of small-scale, turbulent magnetic fields is a long-standing issue in astrophysics. analytical theories disagree with numerical simulations at rigidities where the particles' gyroradii are slightly smaller than the correlation length of turbulence. at the same time, extending the numerical simulations to lower rigidities has proven computationally prohibitive. in this letter, we provide a solution to the problem of perpendicular transport in isotropic turbulence at both, high and low rigidities. we also clarify the relation between the perpendicular diffusion of particles and the transport of magnetic field lines. to this end, we have run a large suite of test particle simulations at unprecedentedly low rigidites, making extensive use of graphical processing units (gpus). we have also developed an analytical model, based on (1) initial particle transport along field lines, (2) the transport of field lines and (3) the eventual decorrelation of particles from field lines. our numerical results exhibit a non-standard rigidity-dependence for the perpendicular diffusion coefficient at intermediate rigidites. at the lowest rigidities, the standard rigidity-dependence is recovered. the simulated diffusion coefficients are nicely reproduced by our analytical model. we have traced the non-standard rigidity-dependence to a subdiffusive phase in the field line transport. our study has important implications for the transport of galactic cosmic rays, acceleration at perpendicular shocks and for high-energy particles in the heliosphere. | field line subdiffusion and cosmic ray perpendicular transport in isotropic turbulence |
we demonstrate that ionization of h2 by dark matter in dense molecular clouds can provide strong constraints on the scattering strength of dark matter with electrons. molecular clouds have high uv-optical attenuation, shielding them from ultraviolet and x-ray photons. their chemical and thermal evolution are governed by low-energy cosmic rays. dark matter with mass ≳4 mev can ionize h2 , contributing to the observed ionization rate. we require that the dark matter-induced ionization rate of h2 not exceed the observed cosmic-ray ionization rate ζh2, in diffuse molecular clouds as well as dense molecular clouds such as l1551 in the taurus cloud complex. this allows us to place strong constraints on the dark matter-electron cross section σ¯e that complement existing astrophysical constraints and probe the strongly interacting parameter space where terrestrial and underground direct-detection experiments lose sensitivity. we show that constraints from molecular clouds combined with planned balloon and satellite-based experiments would strongly constrain the fractional abundance of dark matter that interacts strongly with electrons. we comment on future modeling and observational efforts that may improve our bounds. | constraints on dark matter-electron scattering from molecular cloud ionization |
solar magnetic activity drives the dominant 11-year cyclic variability of different space environmental indices, but they can be delayed with respect to the original variations due to the different physical processes involved. here, we analyzed the pairwise time lags between three global solar and heliospheric indices: sunspot numbers (ssn), representing the solar surface magnetic activity, the open solar flux (osf), representing the heliospheric magnetic variability, and the galactic cosmic-ray (gcr) intensity near earth, using the standard cross-correlation and the more detailed wavelet-coherence methods. all the three indices appear highly coherent at a timescale longer than a few years with persistent high coherence at the timescale of the 11-year solar cycle. the gcr variability is delayed with respect to the inverted ssn by about eight 27-day bartels rotations on average, but the delay varies greatly with the 22-year cycle, being shorter or longer around positive a + or negative a − solar polarity epochs, respectively. the 22-year cyclicity of the time lag is determined by the global heliospheric drift effects, in agreement with theoretical models. the osf lags by about one year behind ssn, and is likely determined by a combination of the short lifetime of active regions and a longer (≈3 years) transport time of the surface magnetic field to the poles. gcrs covary nearly in antiphase with the osf, also depicting a strong 22-year cycle in the delay, confirming that the osf is a good index of the heliospheric modulation of gcrs. this provides an important observational constraint for solar and heliospheric physics. | time lag between cosmic-ray and solar variability: sunspot numbers and open solar magnetic flux |
tidal disruption events (tdes) by supermassive or intermediate mass black holes have been suggested as candidate sources of ultrahigh-energy cosmic rays (uhecrs) and high-energy neutrinos. motivated by the recent measurements from the pierre auger observatory, which indicates a metal-rich cosmic-ray composition at ultrahigh energies, we investigate the fate of uhecr nuclei loaded in tde jets. first, we consider the production and survival of uhecr nuclei at internal shocks, external forward and reverse shocks, and nonrelativistic winds. based on the observations of swift j 1644 +57 , we show that the uhecrs can survive for external reverse and forward shocks, and disk winds. on the other hand, uhecr nuclei are significantly disintegrated in internal shocks, although they could survive for low-luminosity tde jets. assuming that uhecr nuclei can survive, we consider implications of different composition models of tdes. we find that the tidal disruption of main sequence stars or carbon-oxygen white dwarfs does not successfully reproduce uhecr observations, namely the observed composition or spectrum. the observed mean depth of the shower maximum and its deviation could be explained by oxygen-neon-magnesium white dwarfs, although they may be too rare to be the sources of uhecrs. | high-energy cosmic ray nuclei from tidal disruption events: origin, survival, and implications |
a rare dataset of in-situ 10be from high-resolution depth profiles, soils, rock outcrops, and stream sediments is combined with geochemical analysis and modelling of regolith evolution to understand the variability of denudation rates in a mountain watershed (strengbach critical zone observatory). high-resolution depth profiles are key to detect the presence of mobile regolith and to highlight how it affects the critical zone evolution. the modelling of regolith evolution and 10be concentrations along depth profiles allow us to estimate both the cosmic ray exposure age (19 kyr) and the mean denudation rate (22 mm kyr−1) of the regolith without any steady-state assumption on 10be concentrations. comparison with maximum denudation rates inferred from topsoil samples collected from the surface of the depth profiles and calculated using the temporal steady-state assumption of 10be concentrations highlights an overestimation of denudation by a factor of two. maximum spatially averaged denudation rates determined from stream sediment samples also likely overestimate denudation rates by a factor of two. these biases are significant for investigating the geomorphological evolution and we propose a method to correct denudation rates using the inherited 10be concentrations and the cosmic ray exposure age deduced from the high-resolution depth profiles. a key result is also that a steady state of 10be concentrations and a steady state of regolith thickness are two different equilibrium states that do not necessarily coincide. the comparison between locally corrected and spatially averaged denudation rates indicates that the watershed geomorphology is not in a topographic steady state but is modulated by regressive fluvial erosion. nonetheless, our study demonstrates that even in a watershed where the steady-state assumption of 10be concentrations is not verified, the spatial variations of in-situ 10be concentrations in sediments still carry qualitatively relevant information on the geomorphological evolution of landscapes. | quantifying geomorphological evolution from 10 be denudation rates: insights from high-resolution depth profiles, topsoils, and stream sediments (strengbach czo, france) |
the geomagnetic dipole moment (gdm) modulates the production rates of cosmogenic radionuclides via the shielding of galactic cosmic rays. therefore, it is possible to use this linkage to reconstruct past changes in the gdm based on cosmogenic radionuclide records from natural archives such as ice cores. here we present a gdm reconstruction based on 10be and 36cl data from two greenland ice cores from 11.7 ka to 108 ka b2k (before a.d. 2000). we find that the cosmogenic radionuclide records reflect a mixture of climate and production effects that require separation to evaluate the changes in the gdm. to minimize climate-related variations on isotope data, we applied a multi-linear correction method by removing common variability between 10be and 36cl and climate parameters (accumulation rates, δ18o and ion data) from radionuclide records. the resulting "climate corrected" radionuclide data are converted to gdm using a theoretical production model. comparison of "climate corrected" radionuclides based gdm reconstructions with independent paleomagnetic-derived gdm records shows a good agreement. furthermore, the "climate correction" leads to an improved agreement with gdm reconstructions than simply using radionuclide fluxes, lending support to the validity of our correction method to isolate production rate changes from ice core radionuclide records. with this correction method, we can extend the gdm reconstructions based on the cosmogenic radionuclides in ice cores to a period when there is a strong climate signal in the data. | geomagnetic dipole moment variations for the last glacial period inferred from cosmogenic radionuclides in greenland ice cores via disentangling the climate and production signals |
k-euso (klypve-euso) is a planned orbital mission aimed at studying ultra-high energy cosmic rays (uhecrs) by detecting fluorescence and cherenkov light emitted by extensive air showers in the nocturnal atmosphere of earth in the ultraviolet (uv) range. the observatory is being developed within the jem-euso collaboration and is planned to be deployed on the international space station after 2025 and operated for at least two years. the telescope, consisting of ∼105 independent pixels, will allow a spatial resolution of ∼0.6 km on the ground, and, from a 400 km altitude, it will achieve a large and full sky exposure to sample the highest energy range of the uhecr spectrum. we provide a comprehensive review of the current status of the development of the k-euso experiment, paying special attention to its hardware parts and expected performance. we demonstrate how results of the k-euso mission can complement the achievements of the existing ground-based experiments and push forward the intriguing studies of ultra-high energy cosmic rays, as well as bring new knowledge about other phenomena manifesting themselves in the atmosphere in the uv range. | status of the k-euso orbital detector of ultra-high energy cosmic rays |
atmospheric neutrinos are one of the most relevant natural neutrino sources that can be exploited to infer properties about cosmic rays and neutrino oscillations. the jiangmen underground neutrino observatory (juno) experiment, a 20 kton liquid scintillator detector with excellent energy resolution is currently under construction in china. juno will be able to detect several atmospheric neutrinos per day given the large volume. a study on the juno detection and reconstruction capabilities of atmospheric νe and νμ fluxes is presented in this paper. in this study, a sample of atmospheric neutrino monte carlo events has been generated, starting from theoretical models, and then processed by the detector simulation. the excellent timing resolution of the 3" pmt light detection system of juno detector and the much higher light yield for scintillation over cherenkov allow to measure the time structure of the scintillation light with very high precision. since νe and νμ interactions produce a slightly different light pattern, the different time evolution of light allows to discriminate the flavor of primary neutrinos. a probabilistic unfolding method has been used, in order to infer the primary neutrino energy spectrum from the detector experimental observables. the simulated spectrum has been reconstructed between 100 mev and 10 gev, showing a great potential of the detector in the atmospheric low energy region. | juno sensitivity to low energy atmospheric neutrino spectra |
results of the search for ∼(1 016- 1 017.5) ev primary cosmic-ray photons with the data of the moscow state university (msu) extensive air shower (eas) array are reported. the full-scale reanalysis of the data with modern simulations of the installation does not confirm previous indications of the excess of gamma-ray candidate events. upper limits on the corresponding gamma-ray flux are presented. the limits are among the most stringent published ones at energies ∼1 017 ev . | constraints on the flux of ∼(1016- 1 017.5) ev cosmic photons from the eas-msu muon data |
we investigate the potential of type ii supernovae (sne) to constrain axionlike particles (alps) coupled simultaneously to nucleons and electrons. alps coupled to nucleons can be efficiently produced in the sn core via nucleon-nucleon bremsstrahlung and, for a wide range of parameters, leave the sn unhindered, producing a large alp flux. for masses exceeding 1 mev, these alps would decay into electron-positron pairs, generating a positron flux. in the case of galactic sne, the annihilation of the created positrons with the electrons present in the galaxy would contribute to the 511 kev annihilation line. using the spectrometer on integral observation of this line allows us to exclude a wide range of the axion-electron coupling, 10-19≲ga e≲10-11, for ga p∼10-9. additionally, alps from extra-galactic sne decaying into electron-positron pairs would yield a contribution to the cosmic x-ray background. in this case, we constrain the alp-electron coupling down to ga e∼10-20. | supernova bounds on axionlike particles coupled with nucleons and electrons |
x-ray spectroscopy is key to address the theme of "the hot universe", the still poorly understood astrophysical processes driving the cosmological evolution of the baryonic hot gas traceable through its electromagnetic radiation. two future x-ray observatories: the jaxa-led xrism (due to launch in the early 2020s), and the esa cosmic vision l-class mission athena (early 2030s) will provide breakthroughs in our understanding of how and when large-scale hot gas structures formed in the universe, and in tracking their evolution from the formation epoch to the present day. | the hot universe with xrism and athena |
the level of solar modulation at different times (related to the solar activity) is a central question of solar and galactic cosmic-ray physics. in the first paper of this series, we have established a correspondence between the uncertainties on ground-based detectors count rates and the parameter ϕ (modulation level in the force-field approximation) reconstructed from these count rates. in this second paper, we detail a procedure to obtain a reference ϕ time series from neutron monitor data. we show that we can have an unbiased and accurate ϕ reconstruction (δϕ / ϕ ≃ 10 %). we also discuss the potential of bonner spheres spectrometers and muon detectors to provide ϕ time series. two by-products of this calculation are updated ϕ values for the cosmic-ray database and a web interface to retrieve and plot ϕ from the 50's to today (http://lpsc.in2p3.fr/crdb). | neutron monitors and muon detectors for solar modulation studies: 2. ϕ time series |
this study presents a fabrication process for lithium-drifted silicon (si(li)) detectors that, compared to previous methods, allows for mass production at a higher yield, while providing a large sensitive area and low leakage currents at relatively high temperatures. this design, developed for the unique requirements of the general antiparticle spectrometer (gaps) experiment, has an overall diameter of 10 cm, with ∼9 cm of active area segmented into 8 readout strips, and an overall thickness of 2.5 mm, with ≳ 2 . 2 mm (≳ 90%) sensitive thickness. an energy resolution ≲ 4 kev full-width at half-maximum (fwhm) for 20 -100 kev x-rays is required at the operating temperature ∼ - 40 ° c , which is far above the liquid nitrogen temperatures conventionally used to achieve fine energy resolution. high-yield production is also required for gaps, which consists of ≳ 1000 detectors. our specially-developed si crystal and custom methods of li evaporation, diffusion and drifting allow for a thick, large-area and uniform sensitive layer. we find that retaining a thin undrifted layer on the p-side of the detector drastically reduces the leakage current, which is a dominant component of the energy resolution at these temperatures. a guard-ring structure and optimal etching of the detector surface are also confirmed to suppress the leakage current. we report on the mass production of these detectors that is ongoing now, and demonstrate it is capable of delivering a high yield of ∼ 90% . | developing a mass-production model of large-area si(li) detectors with high operating temperatures |
in this paper, we build from previous work and present simulations of recent (within the past gyr), magnetized, cosmic-ray driven outflows from the large magellanic cloud (lmc), including our first attempts to explicitly use the derived star formation history of the lmc to seed outflow generation. we run a parameter set of simulations for different lmc gas masses and cosmic-ray transport treatments, and we make preliminary comparisons to published outflow flux estimates, neutral and ionized hydrogen observations, and faraday rotation measure maps. we additionally report on the gas mass that becomes unbound from the lmc disk and swept by ram pressure into the trailing magellanic stream. we find that, even for our largest outburst, the mass contribution to the stream is still quite small, as much of the outflow-turned-halo gas is shielded on the lmcs far-side due to the lmcs primarily face-on infall through the milky way halo over the past gyr. on the lmc's near-side, past outflows have fought an uphill battle against ram pressure, with the near-side halo mass being at least a factor of a few smaller than that of the far-side. absorption-line studies probing only the lmc foreground, then, may be severely underestimating the total mass of the lmc halo formed by outflows. | cosmic-ray-driven outflows from the large magellanic cloud: contributions to the lmc filament |
the late devonian was a protracted period of low speciation resulting in biodiversity decline, culminating in extinction events near the devonian-carboniferous boundary. recent evidence indicates that the final extinction event may have coincided with a dramatic drop in stratospheric ozone, possibly due to a global temperature rise. here we study an alternative possible cause for the postulated ozone drop: a nearby supernova explosion that could inflict damage by accelerating cosmic rays that can deliver ionizing radiation for up to $\sim 100$ kyr. we therefore propose that the end-devonian extinctions were triggered by supernova explosions at $\sim 20$ pc, somewhat beyond the "kill distance" that would have precipitated a full mass extinction. such nearby supernovae are likely due to core-collapses of massive stars; these are concentrated in the thin galactic disk where the sun resides. detecting either of the long-lived radioisotopes sm-146 or pu-244 in one or more end-devonian extinction strata would confirm a supernova origin, point to the core-collapse explosion of a massive star, and probe supernova nucleosythesis. other possible tests of the supernova hypothesis are discussed. | supernova triggers for end-devonian extinctions |
we investigate a scenario where dark matter (dm) particles can be captured and accumulate in the sun, and subsequently annihilate into a pair of long-lived mediators. these mediators can decay further out in the sun or outside of the sun. compared to the standard scenario where dm particles annihilate directly into standard model particles close to the solar core, here we also obtain fluxes of gamma rays and charged cosmic rays. we simulate this scenario using a full three-dimensional model of the sun, and include interactions and neutrino oscillations. in particular, we perform a model-independent study of the complementarity between neutrino and gamma ray fluxes by comparing the recent searches from icecube, super-kamiokande, fermi-lat, argo and hawc. we find that the resulting neutrino fluxes are significantly higher at high energy when the mediators decay further out in the sun. we also find that gamma ray searches place stronger constraints than neutrino searches on these models even in cases where the mediators decay mainly inside the sun, except in the approximately inner 10% of the sun where neutrino searches are more powerful. we present our results in a model-independent manner and release a new version of the \textsf{wimpsim} code that can be used to simulate this scenario for arbitrary mediator models. | neutrinos and gamma rays from long-lived mediator decays in the sun |
core-collapse supernovae produce fast shocks which pervade the dense circumstellar medium (csm) of the stellar progenitor. cosmic rays (crs) if accelerated at these shocks can induce the growth of electromagnetic fluctuations in the foreshock medium. in this study, using a self-similar description of the shock evolution, we calculate the growth time-scales of cr-driven instabilities. we select a sample of nearby core-collapse radio supernova of type ii and ib/ic. from radio data, we infer the parameters which enter in the calculation of the instability growth times. we find that extended iib sne shocks can trigger fast intra-day instabilities, strong magnetic field amplification, and cr acceleration. in particular, the non-resonant streaming instability can contribute to about 50 per cent of the magnetic field intensity deduced from radio data. this results in the acceleration of crs in the range 1-10 pev within a few days after the shock breakout. in order to produce strong magnetic field amplification and cr acceleration, a fast shock pervading a dense csm is necessary. in that aspect, iin supernovæ are also good candidates. but a detailed modelling of the blast wave dynamics coupled with particle acceleration is mandatory for this class of object before providing any firm conclusions. finally, we find that the trans-relativistic object sn 2009bb even if it produces more modest magnetic field amplification can accelerate crs up to 2-3 pev within 20 d after the outburst. | core-collapse supernovae as cosmic ray sources |
the energy spectrum of cosmic neutrinos, which was recently reported by the icecube collaboration, shows a gap between 400 tev and 1 pev. an unknown neutrino interaction mediated by a field with a mass of the mev scale is one of the possible solutions to this gap. we examine whether the leptonic gauge interaction lμ-lτ can simultaneously explain the two phenomena in the lepton sector: the gap in the cosmic neutrino spectrum and the unsettled disagreement in the muon anomalous magnetic moment. we illustrate that there remain regions in the model parameter space which account for both of the problems. our results also provide a hint to the distance to the source of the high-energy cosmic neutrinos. | cosmic neutrino spectrum and the muon anomalous magnetic moment in the gauged lμ-lτ model |
the processes responsible for the effective longitudinal transport of solar energetic particles (seps) are still not completely understood. we address this issue by simulating sep electron propagation using a spatially 2d transport model that includes perpendicular diffusion. by implementing, as far as possible, the most reasonable estimates of the transport (diffusion) coefficients, we compare our results, in a qualitative manner, to recent observations at energies of 55-105 kev, focusing on the longitudinal distribution of the peak intensity, the maximum anisotropy, and the onset time. by using transport coefficients that are derived from first principles, we limit the number of free parameters in the model to (i) the probability of seps following diffusing magnetic field lines, quantified by a\in [0,1], and (ii) the broadness of the gaussian injection function. it is found that the model solutions are extremely sensitive to the magnitude of the perpendicular diffusion coefficient and relatively insensitive to the form of the injection function as long as a reasonable value of a = 0.2 is used. we illustrate the effects of perpendicular diffusion on the model solutions and discuss the viability of this process as a dominant mechanism by which seps are transported in longitude. lastly, we try to quantity the effectiveness of perpendicular diffusion as an interplay between the magnitude of the relevant diffusion coefficient and the sep intensity gradient driving the diffusion process. it follows that perpendicular diffusion is extremely effective early in an sep event when large intensity gradients are present, while the effectiveness quickly decreases with time thereafter. | perpendicular diffusion of solar energetic particles: model results and implications for electrons |
context. quantifying the fraction of active galactic nuclei (agn) in the faint radio population and understanding their relation with star-forming activity are fundamental to studies of galaxy evolution. very long baseline interferometry (vlbi) observations are able to identify agn above relatively low redshifts (z> 0.1) since they provide milli-arcsecond resolution.aims: we have created an agn catalogue from 2865 known radio sources observed in the cosmic evolution survey (cosmos) field, which has exceptional multi-wavelength coverage. with this catalogue we intend to study the faint radio sky with statistically relevant numbers and to analyse the agn - host galaxy co-evolution, making use of the large amount of ancillary data available in the field.methods: wide-field vlbi observations were made of all known radio sources in the cosmos field at 1.4 ghz to measure the agn fraction, in particular in the faint radio population. we describe in detail the observations, data calibration, source detection and flux density measurements, parts of which we have developed for this survey. the combination of number of sources, sensitivity, and area covered with this project are unprecedented.results: we have detected 468 radio sources, expected to be agn, with the very long baseline array (vlba). this is, to date, the largest sample assembled of vlbi detected sources in the sub-mjy regime. the input sample was taken from previous observations with the very large array (vla). we present the catalogue with additional optical, infrared and x-ray information.conclusions: we find a detection fraction of 20 ± 1%, considering only those sources from the input catalogue which were in principle detectable with the vlba (2361). as a function of the vla flux density, the detection fraction is higher for higher flux densities, since at high flux densities a source could be detected even if the vlbi core accounts for a small percentage of the total flux density. as a function of redshift, we see no evolution of the detection fraction over the redshift range 0.5 <z< 3. in addition, we find that faint radio sources typically have a greater fraction of their radio luminosity in a compact core - 70% of the sub-mjy sources detected with the vlba have more than half of their total radio luminosity in a vlbi-scale component, whereas this is true for only 30% of the sources that are brighter than 10 mjy. this suggests that fainter radio sources differ intrinsically from brighter ones. across our entire sample, we find the predominant morphological classification of the host galaxies of the vlba detected sources to be early type (57%), although this varies with redshift and at z> 1.5 we find that spiral galaxies become the most prevalent (48%). the number of detections is high enough to study the faint radio population with statistically significant numbers. we demonstrate that wide-field vlbi observations, together with new calibration methods such as multi-source self-calibration and mosaicing, result in information which is difficult or impossible to obtain otherwise. the full tables 2 and 3 are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/607/a132 | the faint radio sky: vlba observations of the cosmos field |
we have experimentally determined the production rate of 39ar and 37ar from cosmic ray neutron interactions in argon at sea level. understanding these production rates is important for argon-based dark matter experiments that plan to utilize argon extracted from deep underground because it is imperative to know what the ingrowth of 39ar will be during the production, transport, and storage of the underground argon. these measurements also allow for the prediction of 39ar and 37ar concentrations in the atmosphere which can be used to determine the presence of other sources of these isotopes. through controlled irradiation with a neutron beam that mimics the cosmic ray neutron spectrum, followed by direct counting of 39ar and 37ar decays with sensitive ultralow background proportional counters, we determined that the production rate from cosmic ray neutrons at sea level is expected to be (759 ±128 ) atoms /(kgarday ) for 39ar, and (51.0 ±7.4 ) atoms /(kgarday ) for 37ar. we also performed a survey of the alternate production mechanisms based on the state of knowledge of the associated cross sections to obtain a total sea-level cosmic ray production rate of (1048 ±133 ) atoms /(kgarday ) for 39ar, (56.7 ±7.5 ) atoms /(kgarday ) for 37ar in underground argon, and (92 ±13 ) atoms /(kgarday ) for 37ar in atmospheric argon. | cosmogenic production of 39ar and 37ar in argon |
context. dynamical motions in the intra-cluster medium (icm) can imprint distinctive features on x-ray images that map the thermal bremsstrahlung emission from galaxy clusters, such as sharp surface brightness discontinuities due to shocks and cold fronts. the gas dynamics during cluster mergers may also drive large-scale turbulence in the icm, which in turn generates extended (megaparsec-scale) synchrontron sources known as radio halos.aims: surface brightness edges have been found numerous times in the thermal gas of clusters based on x-ray observations. in contrast, edges in radio halos have only been observed in a handful of cases. our goal is to search for new radio surface brightness discontinuities in the icm.methods: we inspected the images of the bullet cluster and the other 25 radio halos reported in the meerkat galaxy cluster legacy survey. to aid the identification of surface brightness discontinuities, we applied a gradient-filtering edge-detection method to the radio images.results: we find that the adopted filtering technique is helpful in identifying surface brightness edges in radio images, allowing us to identify at least one gradient in half of the radio halos studied. for the bullet cluster, we find excellent agreement between the locations of the four radio discontinuities detected and the x-ray edges. this similarity informs us that there is substantial interplay between thermal and nonthermal components in galaxy clusters. this interplay is likely due to the frozen-in icm magnetic field, which mediates the advection of cosmic rays while being dragged by thermal gas flows.conclusions: we conclude that radio halos are shaped by dynamical motions in the icm and that they often display surface brightness discontinuities, which appear to be co-located with edges in the thermal gas emission. our results demonstrate that new and future generations of radio telescopes will provide an approach to efficiently detecting shocks and cold fronts in the icm that is complementary to x-rays. | surface brightness discontinuities in radio halos. insights from the meerkat galaxy cluster legacy survey |
recent measurements of the dipole anisotropy in the arrival directions of galactic cosmic rays (crs) indicate a strong energy dependence of the dipole amplitude and phase in the tev-pev range. we argue here that these observations can be well understood within standard diffusion theory as a combined effect of (i) one or more local sources at galactic longitude 12 0 ° ≲l ≲30 0 ° dominating the cr gradient below 0.1-0.3 pev, (ii) the presence of a strong ordered magnetic field in our local environment, (iii) the relative motion of the solar system, and (iv) the limited reconstruction capabilities of ground-based observatories. we show that an excellent candidate of the local cr source responsible for the dipole anisotropy at 1-100 tev is the vela supernova remnant. | deciphering the dipole anisotropy of galactic cosmic rays |
star-forming galaxies emit gev and tev gamma-rays that are thought to originate from hadronic interactions of cosmic-ray (cr) nuclei with the interstellar medium. to understand the emission, we have used the moving-mesh code arepo to perform magnetohydrodynamical galaxy formation simulations with self-consistent cr physics. our galaxy models exhibit a first burst of star formation that injects crs at supernovae. once crs have sufficiently accumulated in our milky way-like galaxy, their buoyancy force overcomes the magnetic tension of the toroidal disk field. as field lines open up, they enable anisotropically diffusing crs to escape into the halo and to accelerate a bubble-like, cr-dominated outflow. however, these bubbles are invisible in our simulated gamma-ray maps of hadronic pion-decay and secondary inverse-compton emission because of low gas density in the outflows. by adopting a phenomenological relation between star formation rate (sfr) and far-infrared emission and assuming that gamma-rays mainly originate from decaying pions, our simulated galaxies can reproduce the observed tight relation between far-infrared and gamma-ray emission, independent of whether we account for anisotropic cr diffusion. this demonstrates that uncertainties in modeling active cr transport processes only play a minor role in predicting gamma-ray emission from galaxies. we find that in starbursts, most of the cr energy is “calorimetrically” lost to hadronic interactions. in contrast, the gamma-ray emission deviates from this calorimetric property at low sfrs due to adiabatic losses, which cannot be identified in traditional one-zone models. | simulating gamma-ray emission in star-forming galaxies |
we present a new numerical algorithm to solve the recently derived equations of two-moment cosmic ray hydrodynamics (crhd). the algorithm is implemented as a module in the moving mesh arepo code. therein, the anisotropic transport of cosmic rays (crs) along magnetic field lines is discretized using a path-conservative finite volume method on the unstructured time-dependent voronoi mesh of arepo. the interaction of crs and gyroresonant alfvén waves is described by short time-scale source terms in the crhd equations. we employ a custom-made semi-implicit adaptive time stepping source term integrator to accurately integrate this interaction on the small light-crossing time of the anisotropic transport step. both the transport and the source term integration step are separated from the evolution of the magnetohydrodynamical equations using an operator split approach. the new algorithm is tested with a variety of test problems, including shock tubes, a perpendicular magnetized discontinuity, the hydrodynamic response to a cr overpressure, cr acceleration of a warm cloud, and a cr blast wave, which demonstrate that the coupling between cr and magnetohydrodynamics is robust and accurate. we demonstrate the numerical convergence of the presented scheme using new linear and non-linear analytic solutions. | a finite volume method for two-moment cosmic ray hydrodynamics on a moving mesh |
we present an update on crdb, the cosmic-ray database for charged species. crdb is based on mysql, queried and sorted by jquery and table-sorter libraries, and displayed via php web pages through the ajax protocol. we review the modifications made on the structure and outputs of the database since the first release (maurin et al., 2014). for this update, the most important feature is the inclusion of ultra-heavy nuclei (z>30), ultra-high energy nuclei (from 1015 to 1020 ev), and limits on antinuclei fluxes (z≤‑1 for a>1); more than 100 experiments, 350 publications, and 40,000 data points are now available in crdb. we also revisited and simplified how users can retrieve data and submit new ones. for questions and requests, please contact crdb@lpsc.in2p3.fr. | cosmic-ray database update: ultra-high energy, ultra-heavy, and antinuclei cosmic-ray data (crdb v4.0) |
the high-energy atmospheric neutrino flux is dominated by neutrinos from the decays of charmed hadrons produced in the forward direction by cosmic ray interactions with air nuclei. we evaluate the charm contributions to the prompt atmospheric neutrino flux as a function of the center-of-mass energy √{s } of the hadronic collision and of the center-of-mass rapidity y of the produced charm hadron. uncertainties associated with parton distribution functions are also evaluated as a function of y. we find that the y coverage of lhcb for forward heavy-flavour production, complemented by the angular coverage of present and future forward neutrino experiments at the lhc, bracket the most interesting y regions for the prompt atmospheric neutrino flux. at √{s } = 14 tev foreseen for the hl-lhc phase, nucleon collisions in air contribute to the prompt neutrino flux prominently below eν ~ 107 gev. measurements of forward charm and/or forward neutrinos produced in hadron collisions up to √{s } = 100 tev, which might become possible at the fcc, are relevant for the prompt atmospheric neutrino flux up to eν = 108 gev and beyond. | forward production of prompt neutrinos from charm in the atmosphere and at high energy colliders |
the simplest cosmologies motivate the consideration of dark matter subcomponents that interact significantly with normal matter. moreover, such strongly-coupled relics may have evaded detection to date if upon encountering the earth they rapidly thermalize down to terrestrial temperatures, $t_\oplus \sim 300 \ \text{k} \sim 25 \ \text{mev}$, well below the thresholds of most existing dark matter detectors. this shedding of kinetic energy implies a drastic enhancement to the local density, motivating the consideration of alternative detection techniques sensitive to a large density of slowly-moving dark matter particles. in this work, we provide a rigorous semi-analytic derivation of the terrestrial overdensities of strongly-coupled relics, with a particular focus on millicharged particles (mcps). we go beyond previous studies by incorporating improved estimates of the mcp-atomic scattering cross section, new contributions to the terrestrial density of sub-gev relics that are independent of earth's gravitational field, and local modifications that can arise due to the cryogenic environments of precision sensors. we also generalize our analysis in order to estimate the terrestrial density of thermalized mcps that are produced from the collisions of high-energy cosmic rays and become bound by earth's electric field. | the terrestrial density of strongly-coupled relics |
upcoming neutrino telescopes may discover ultra-high-energy (uhe) cosmic neutrinos, with energies beyond 100 pev, in the next 10-20 years. finding their sources would identify guaranteed sites of interaction of uhe cosmic rays, whose origin is unknown. we search for sources by looking for multiplets of uhe neutrinos arriving from similar directions. our forecasts are state-of-the-art, geared at neutrino radio-detection in icecube-gen2. they account for detector energy and angular response, and for critical, but uncertain backgrounds. sources at declination of -45° to 0° will be easiest to discover. discovering even one steady-state source in 10 years would imply that the source has an uhe neutrino luminosity at least larger than about 1043 erg/s (depending on the source redshift evolution). discovering no transient source would disfavor transient sources brighter than 1053 erg as dominant. our results aim to inform the design of upcoming detectors. | near-future discovery of point sources of ultra-high-energy neutrinos |
the heliotail is formed when the solar wind (sw) interacts with the local interstellar medium (lism) and is shaped by the interstellar magnetic field (ismf). while there are no spacecraft available to perform in situ measurements of the sw plasma and heliospheric magnetic field (hmf) in the heliotail, it is of importance for the interpretation of measurements of energetic neutral atom fluxes performed by interstellar boundary explorer. it has been shown recently that the orientation of the heliotail in space and distortions of the unperturbed lism caused by its presence may explain the anisotropy in the tev cosmic ray flux detected in air shower observations. the sw flow in the heliotail is a mystery itself because it is strongly affected by charge exchange between the sw ions and interstellar neutral atoms. if the angle between the sun’s magnetic and rotation axes is constant, the sw in the tail tends to be concentrated inside the hmf spirals deflected tailward. however, the twisted field soon becomes unstable and the reason for the sw collimation within a two-lobe structure vanishes. we demonstrate that kinetic treatment of the h atom transport becomes essential in this case for explaining the lobe absence further along the tail. we show that the heliotail flow is strongly affected by the solar cycle that eliminates artifacts, which is typical of solutions based on simplifying assumptions. the heliopause in the tail is subject to kelvin-helmholtz instability, while its orientation and shape are determined by the ismf direction and strength. | the heliotail |
one of the key questions in astrophysics concerns the issue of whether there exists an upper-mass limit to stars, and if so, what physical mechanism sets this limit? the answer to this question might also determine if the upper-mass limit is metallicity (z) dependent. we argue that mass loss by radiation-driven winds mediated by line opacity is one of the prime candidates setting the upper-mass limit. we present mass-loss predictions (ṁwind) from monte carlo radiative transfer models for relatively cool (teff = 15 kk) very inflated massive stars (vms) with large eddington γ factors in the mass range 102-103 m⊙ as a function of metallicity down to 1/100 z/z⊙. we employed a hydrodynamic version of our monte carlo method, allowing us to predict the rate of mass loss (ṁwind) and the terminal wind velocity (v∞) simultaneously. interestingly, we find wind terminal velocities (v∞) that are low (100-500 km s-1) over a wide z-range, and we propose that the slow winds from vms are an important source of self-enrichment in globular clusters. we also find mass-loss rates (ṁwind), exceeding the typical mass-accretion rate (ṁaccr) of 10-3 m⊙ yr-1 during massive-star formation. we have expressed our mass-loss predictions as a function of mass and z, finding log ṁ = -9.13 + 2.1 log(m/m⊙) + 0.74 log(z/z⊙) (m⊙/yr). even if stellar winds do not directly halt & reverse mass accretion during star formation, if the most massive stars form by stellar mergers, stellar wind mass loss may dominate over the rate at which stellar growth takes place. we therefore argue that the upper-mass limit is effectively z-dependent due to the nature of radiation-driven winds. this has dramatic consequences for the most luminous supernovae, gamma-ray bursts, and other black hole formation scenarios at different cosmic epochs. | very massive stars: a metallicity-dependent upper-mass limit, slow winds, and the self-enrichment of globular clusters |
we present the precision measurement of 2824 daily helium fluxes in cosmic rays from may 20, 2011 to october 29, 2019 in the rigidity interval from 1.71 to 100 gv based on 7.6 ×108 helium nuclei collected with the alpha magnetic spectrometer (ams) aboard the international space station. the helium flux and the helium to proton flux ratio exhibit variations on multiple timescales. in nearly all the time intervals from 2014 to 2018, we observed recurrent helium flux variations with a period of 27 days. shorter periods of 9 days and 13.5 days are observed in 2016. the strength of all three periodicities changes with time and rigidity. in the entire time period, we found that below ∼7 gv the helium flux exhibits larger time variations than the proton flux, and above ∼7 gv the helium to proton flux ratio is time independent. remarkably, below 2.4 gv a hysteresis between the helium to proton flux ratio and the helium flux was observed at greater than the 7 σ level. this shows that at low rigidity the modulation of the helium to proton flux ratio is different before and after the solar maximum in 2014. | properties of daily helium fluxes |
cosmogenic radionuclide records from polar ice cores provide unique insights into past cosmic ray flux variations. they allow reconstructions of past solar activity, space weather, and geomagnetic field changes, and provide insights into past carbon cycle changes. however, all these applications rely on the proportionality of the ice core radionuclide records to the global mean production rate changes. this premise has been long debated from a model and data-perspective. here, we address this issue through atmospheric mixing model experiments and comparison to independent data. we find that all mixing scenarios, which do not assume complete tropospheric mixing, result in a polar bias. this bias is more prominent for geomagnetic field changes than solar modulation changes. the most likely scenario, supported by independent geomagnetic field records and marine 10be during the laschamps geomagnetic field minimum, results in a dampening of geomagnetic field induced changes by 23%-37% and an enhancement of solar-induced changes by 7%-8%. during the holocene, we do not find conclusive evidence for a polar bias. we propose a correction function that allows deconvolving the glacial ice core record in order to restore proportionality to the global mean signal. | on the polar bias in ice core 10be data |
the superconducting analyzer for multi-particles from radioisotope (samurai) pion-reconstruction and ion-tracker time projection chamber (sπrit tpc) was designed to enable measurements of heavy ion collisions with the samurai spectrometer at the riken radioactive isotope beam factory and provides constraints on the equation of state of neutron-rich nuclear matter. the sπrit tpc has a 50.5 cm drift length and an 86.4 × 134.4 cm2 pad plane with 12 096 pads that are equipped with the generic electronics for tpcs. the sπrit tpc allows for an excellent reconstruction of particles and provides isotopic resolution for pions and other light charged particles across a wide range of energy losses and momenta. the details of the sπrit tpc are presented, along with discussion of the tpc performance based on cosmic rays and charged particles emitted in heavy ion collisions. | the sπrit time projection chamber |
in many space, astrophysical, and laboratory plasmas the energy contained in the magnetic field or plasma flow exceeds the thermal energy. magnetic field ( ${\boldsymbol{b}}$ ) annihilation, often enabled by magnetic reconnection, transfers magnetic energy to particles. shocks transfer bulk flow energy to particles. if there is a sufficiently large energy transfer, strong turbulence (∣ $\delta {\boldsymbol{b}}$ ∣/∣ b∣ ∼ 1) develops, which, in turn, can result in nonthermal acceleration. in this article, we investigate acceleration in a finite-sized region of strong turbulence driven by magnetic reconnection with analytical modeling and test-particle simulations. this research is based on detailed observations in the earth's magnetotail. we find that the primary transfer of magnetic energy to particle energy is advanced by large-amplitude electric field structures ( ${\boldsymbol{e}}$ ) generated by the strong turbulence. to no surprise, ion energization is dominated by intense dc ${\boldsymbol{e}}$ , ${\boldsymbol{e}}$ near the ion cyclotron frequency (fci), and/or ${\boldsymbol{e}}$ variations at scales near the ion gyroradius. electron energization comes from higher-frequency ${\boldsymbol{e}}$ . the turbulent cascade continuously regenerates ${\boldsymbol{e}}$ near fci and higher frequencies. importantly, the turbulence also creates magnetic depletions that can trap particles and considerably increase their dwell time in regions of strong energization, which substantially enhances nonthermal acceleration. moreover, energization is primarily perpendicular to ${\boldsymbol{b}}$ , so particles have difficulty escaping regions of depleted ${\boldsymbol{b}}$ , which can lead to near runaway acceleration. we discuss how this process may be active in large-scale settings such as supernova shells and may contribute, at least in in part, to the development of the cosmic ray spectrum. | particle acceleration in strong turbulence in the earth's magnetotail |
we demonstrate that the shower-to-shower fluctuations of the muon content of extensive air showers correlate with the fluctuations of a variable of the first interaction of ultra high energy cosmic rays, which is computed from the fraction of energy carried by the hadrons that sustain the hadronic cascade. the influence of subsequent stages of the shower development is found to play a sub-dominant role. as a consequence, the shower-to-shower distribution of the muon content is a direct probe of the hadron energy spectrum of interactions beyond those reachable in human-made accelerators. | probing the energy spectrum of hadrons in proton air interactions at ultrahigh energies through the fluctuations of the muon content of extensive air showers |
on september 12, 2019 at 12:49:48 (ut) a bolide was observed by hundreds of eye-witnesses from the netherlands, germany, belgium, denmark and the uk. one day later a small meteorite stone was found by accident in flensburg. the presence of short-lived cosmogenic radionuclides with half-lives as short as 16 days proves the recent exposure of the found object to cosmic rays in space linking it clearly to the bolide event. an exceptionally short exposure time of ∼5000 years was determined. the 24.5 g stone has a fresh black fusion crust, a low density of <2 g/cm3, and a magnetic susceptibility of logχ = 4.35 (χ in 10-9 m3/kg). the rock consists of relict chondrules and clusters of sulfide and magnetite grains set in a fine-grained matrix. the most abundant phases are phyllosilicates. carbonates (∼3.9 vol.%) occur as calcites, dolomites, and a na-rich phase. the relict chondrules (often surrounded by sulfide laths) are free of anhydrous silicates and contain abundant serpentine. lithic clasts are also surrounded by similar sulfide laths partly intergrown with carbonates. 53mn-53cr ages of carbonates in flensburg indicate that brecciation and contemporaneous formation of the pyrrhotite-carbonate intergrowths by hydrothermal activities occurred no later than 4564.6 ± 1.0 ma (using the angrite d'orbigny as the mn-cr age anchor). this corresponds to 2.6 ± 1.0 or 3.4 ± 1.0 ma after formation of cais, depending on the exact absolute age of cais. this is the oldest dated evidence for brecciation and carbonate formation, which likely occurred during parent body growth and incipient heating due to decay of 26al. in the three oxygen isotope diagram, flensburg plots at the 16o-rich end of the cm chondrite field and in the transition field to cv-ck-cr chondrites. the mass-dependent te isotopic composition of flensburg is slightly different from mean cm chondrites and is most similar to those of the ungrouped c2 chondrite tagish lake. on the other hand, 50ti and 54cr isotope anomalies indicate that flensburg is similar to cm chondrites, as do the ∼10 wt.% h2o of the bulk material. yet, the bulk zn, cu, and pb concentrations are about 30% lower than those of mean cm chondrites. the he, ne, and ar isotopes of flensburg show no solar wind contribution; its trapped noble gas signature is similar to that of cms with a slightly lower concentration of 20netr. based on the bulk h, c, and n elemental abundances and isotopic compositions, flensburg is unique among chondrites, because it has the lightest bulk h and n isotopic compositions of any type 1 or 2 chondrite investigated so far. moreover, the number of soluble organic compounds in flensburg is even lower than that of the brecciated ci chondrite orgueil. the extraordinary significance of flensburg is evident from the observation that it represents the oldest chondrite sample in which the contemporaneous episodes of aqueous alteration and brecciation have been preserved. the characterization of a large variety of carbonaceous chondrites with different alteration histories is important for interpreting returned samples from the osiris-rex and hayabusa 2 missions. | the old, unique c1 chondrite flensburg - insight into the first processes of aqueous alteration, brecciation, and the diversity of water-bearing parent bodies and lithologies |
for a large liquid-argon time-projection chamber (lartpc) operating on or near the earth's surface to detect neutrino interactions, the rejection of cosmogenic background is a critical and challenging task because of the large cosmic-ray flux and the long drift time of the time-projection chamber. we introduce a superior cosmic background rejection procedure based on the wire-cell three-dimensional (3d) event reconstruction for lartpcs. from an initial 1:20 000 neutrino to cosmic-ray background ratio, we demonstrate these tools on data from the microboone experiment and create a high-performance generic neutrino event selection with a cosmic contamination of 14.9% (9.7%) for a visible energy region greater than o (200 ) mev. the neutrino interaction selection efficiency is 80.4% and 87.6% for inclusive νμ charged-current and νe charged-current interactions, respectively. this significantly improved performance compared with existing reconstruction algorithms marks a major milestone toward reaching the scientific goals of lartpc neutrino oscillation experiments operating near the earth's surface. | cosmic ray background rejection with wire-cell lartpc event reconstruction in the microboone detector |
the dark matter particle explorer (dampe) is a space-borne particle detector designed to probe electrons and gamma-rays in the few gev to 10 tev energy range, as well as cosmic-ray proton and nuclei components between 10 gev and 100 tev. the silicon-tungsten tracker-converter is a crucial component of dampe. it allows the direction of incoming photons converting into electron-positron pairs to be estimated, and the trajectory and charge (z) of cosmic-ray particles to be identified. it consists of 768 silicon micro-strip sensors assembled in 6 double layers with a total active area of 6.6 m2. silicon planes are interleaved with three layers of tungsten plates, resulting in about one radiation length of material in the tracker. internal alignment parameters of the tracker have been determined on orbit, with non-showering protons and helium nuclei. we describe the alignment procedure and present the position resolution and alignment stability measurements. | internal alignment and position resolution of the silicon tracker of dampe determined with orbit data |
accurate models of soil moisture are vital for solving core problems in meteorology, hydrology, agriculture and ecology. the capacity for soil moisture modelling is growing rapidly with the development of high-resolution, continent-scale gridded weather and soil data together with advances in modelling methods. in particular, the globalsoilmap.net initiative represents next-generation, depth-specific gridded soil products that may substantially increase soil moisture modelling capacity. here we present an implementation of campbell's infiltration and redistribution model within the nichemapr microclimate modelling package for the r environment, and use it to assess the predictive power provided by the globalsoilmap.net product soil and landscape grid of australia (slga, ∼100 m) as well as the coarser resolution global product soilgrids (sg, ∼250 m). predictions were tested in detail against 3 years of root-zone (3-75 cm) soil moisture observation data from 35 monitoring sites within the oznet project in australia, with additional tests of the finalised modelling approach against cosmic-ray neutron (cosmoz, 0-50 cm, 9 sites from 2011 to 2017) and satellite (ascat, 0-2 cm, continent-wide from 2007 to 2009) observations. the model was forced by daily 0.05° (∼5 km) gridded meteorological data. the nichemapr system predicted soil moisture to within experimental error for all data sets. using the slga or the sg soil database, the oznet soil moisture could be predicted with a root mean square error (rmse) of ∼0.075 m3 m-3 and a correlation coefficient (r) of 0.65 consistently through the soil profile without any parameter tuning. soil moisture predictions based on the slga and sg datasets were ≈ 17% closer to the observations than when using a chloropleth-derived soil data set (digital atlas of australian soils), with the greatest improvements occurring for deeper layers. the cosmoz observations were predicted with similar accuracy (r = 0.76 and rmse of ∼0.085 m3 m-3). comparisons at the continental scale to 0-2 cm satellite data (ascat) showed that the slga/sg datasets increased model fit over simulations using the daas soil properties (r ∼ 0.63 &rmse 15% vs. r 0.48 &rmse 18%, respectively). overall, our results demonstrate the advantages of using globalsoilmap.net products in combination with gridded weather data for modelling soil moisture at fine spatial and temporal resolution at the continental scale. | can next-generation soil data products improve soil moisture modelling at the continental scale? an assessment using a new microclimate package for the r programming environment |
we report new interferometric images of cyclopropenylidene, c-c3h2, toward the young protocluster omc-2 fir 4. the observations were performed at 82 and 85 ghz with the northern extended millimeter array (noema) as part of the project seeds of life in space (solis). in addition, iram-30 m data observations were used to investigate the physical structure of omc-2 fir 4. we find that the c-c3h2 gas emits from the same region where previous solis observations showed bright hc5n emission. from a non-lte analysis of the iram-30 m data, the c-c3h2 gas has an average temperature of ∼40 k, a h2 density of ∼3 × 105 cm-3, and a c-c3h2 abundance relative to h2 of (7 ± 1) × 10-12. in addition, the noema observations provide no sign of significant c-c3h2 excitation temperature gradients across the region (about 3-4 beams), with t ex in the range 8 ± 3 up to 16 ± 7 k. we thus infer that our observations are inconsistent with a physical interaction of the omc-2 fir 4 envelope with the outflow arising from omc-2 fir 3, as claimed by previous studies. the comparison of the measured c-c3h2 abundance with the predictions from an astrochemical pdr model indicates that omc-2 fir 4 is irradiated by an fuv field ∼1000 times larger than the interstellar one, and by a flux of ionizing particles ∼4000 times larger than the canonical value of 1 × 10-17 s-1 from the galaxy cosmic rays, which is consistent with our previous hc5n observations. this provides an important and independent confirmation of other studies that one, or more, source inside the omc-2 fir 4 region emits energetic (≥10 mev) particles. based on observations carried out under project number l15aa with the iram noema interferometer. iram is supported by insu/cnrs (france), mpg (germany) and ign (spain). | solis iv. hydrocarbons in the omc-2 fir4 region, a probe of energetic particle irradiation of the region |
understanding the cosmic-ray (cr) ionization rate is crucial in order to simulate the dynamics of molecular clouds, and interpret the chemical species observed in these objects. calculating the cr ionization rate requires both accurate knowledge of the spectrum of mev to gev protons at the edge of the cloud as well as a model for the propagation of crs into molecular clouds. some models for the propagation of crs in molecular clouds assume them to stream freely along magnetic field lines, while in others they propagate diffusively due to resonant scattering off of magnetic disturbances excited by mhd turbulence present in the medium. we discuss the conditions under which cr diffusion can operate in a molecular cloud, calculate the local cr spectrum and ionization rate in both a free-streaming and diffusive propagation model, and highlight the different results from the two models. we also apply these two models to the propagation through the ism to obtain the proton spectrum seen by voyager 1, and show that such a spectrum favors a diffusive propagation model. | diffusive versus free-streaming cosmic-ray transport in molecular clouds |
in light of the latest icecube data, we discuss the implications of the cosmic ray (cr) energy input from hypernovae (hne) and supernovae (sne) into the universe, and their propagation in the hosting galaxies and galaxy clusters or groups. the magnetic confinement of crs in these environments may lead to efficient neutrino production via pp collisions, resulting in a diffuse neutrino spectrum extending from pev down to 10 tev energies, with a spectrum and flux level compatible with that recently reported by icecube. if the diffuse 10 tev neutrino background largely comes from such cr reservoirs, the corresponding diffuse γ-ray background should be compatible with the recent fermi data. in this scenario, the cr energy input from hne should be dominant over that of sne, implying that the starburst scenario does not work if the sn energy budget is a factor of two larger than the hn energy budget. thus, this strong case scenario can be supported or ruled out in the near future. | extragalactic star-forming galaxies with hypernovae and supernovae as high-energy neutrino and gamma-ray sources: the case of the 10 tev neutrino data |
the first flight of the antarctic impulsive transient antenna (anita) experiment recorded 16 radio signals that were emitted by cosmic-ray induced air showers. the dominant contribution to the radiation comes from the deflection of positrons and electrons in the geomagnetic field, which is beamed in the direction of motion of the air shower. for 14 of these events, this radiation is reflected from the ice and subsequently detected by the anita experiment at a flight altitude of ∼36 km. in this paper, we estimate the energy of the 14 individual events and find that the mean energy of the cosmic-ray sample is 2.9 × 1018 ev, which is significantly lower than the previous estimate. by simulating the anita flight, we calculate its exposure for ultra-high energy cosmic rays. we estimate for the first time the cosmic-ray flux derived only from radio observations and find agreement with measurements performed at other observatories. in addition, we find that the anita data set is consistent with monte carlo simulations for the total number of observed events and with the properties of those events. | energy and flux measurements of ultra-high energy cosmic rays observed during the first anita flight |
precise measurements of spectra of cosmic ray electrons and positrons can effectively probe the nature of dark matter (dm) particles. in a class of models where dm particles initially annihilate into a pair of intermediate particles which then decay into standard model particles, box-shaped spectra can be generated. such spectra are distinct from astrophysical backgrounds and can probably be regarded as characteristic features of the dm annihilation. in this work, we search for such a feature in the total electron plus positron spectrum measured by ams-02 and dampe. no significant evidence for such a dm annihilation component has been found. the 95% confidence level upper limits of the velocity-weighted annihilation cross section are derived, which range from ∼10-26 cm3 s-1 for dm mass of 50 gev to ∼10-23 cm3 s-1 for dm mass of 10 tev. | constraints on the box-shaped cosmic ray electron feature from dark matter annihilation with the ams-02 and dampe data |
modern observations of the interstellar medium (ism) in galaxies detect a variety of atomic and molecular species. the goal is to connect these observations to the astrochemical properties of the ism. 3d hydro-chemical simulations attempt this but due to extreme computational cost, they have to rely on simplified chemical networks and are bound to individual case studies. we present an alternative approach which models the ism at larger scales by an ensemble of pre-calculated 1d thermo-chemical photodissociation region (pdr) calculations that determine the abundance and excitation of atomic and molecular species. we adopt lognormal distributions of column density (av-pdfs) for which each column density is linked to a volume density as derived by hydrodynamical simulations. we consider two lognormal av-pdfs: a diffuse, low-density medium with average visual extinction of \overline{a_ v}=0.75 mag and dispersion of σ = 0.5 and a denser giant molecular cloud with \overline{a_ v}=4 mag and σ = 0.8. we treat the uv radiation field, cosmic ray ionization rate, and metallicity as free parameters. we find that the low-density medium remains fully h i- and c ii-dominated under all explored conditions. the denser cloud remains almost always molecular (i.e. h2-dominated) while its carbon phase (co, c i, and c ii) is sensitive to the above free parameters, implying that existing methods of tracing h2-rich gas may require adjustments depending on environment. our numerical framework can be used to estimate the pdr properties of large ism regions and quantify trends with different environmental parameters as it is fast, covers wide parameter space, and is flexible for extensions. | simulating the atomic and molecular content of molecular clouds using probability distributions of physical parameters |
certain strongly interacting dark matter candidates could have evaded detection, and much work has been done on constraining their parameter space. recently, it was shown theoretically that the scattering cross section for mχ≳1 gev pointlike dark matter with a nucleus cannot be significantly larger than the geometric cross section of the nucleus. this realization closes the parameter space for pointlike strongly interacting dark matter. however, strongly interacting dark matter is still theoretically possible for composite particles, with much parameter space open. we set new, wide-ranging limits based on data from a novel detector at the university of chicago. backgrounds are greatly suppressed by requiring coincidence detection between two spatially separated liquid-scintillator modules. for dark matter (v ∼10-3 c ), the time of flight would be ∼2 μ s , whereas for cosmic rays, it would be ∼2 ns . we outline ways to greatly increase sensitivity at modest costs. | new experimental constraints in a new landscape for composite dark matter |
redshifted 21 cm signal is a promising tool to investigate the state of intergalactic medium (igm) in the cosmic dawn (cd) and epoch of reionization (eor). in our previous work, we studied the variance and skewness of the 21 cm fluctuations to give a clear interpretation of the 21 cm power spectrum and found that skewness is a good indicator of the epoch when x-ray heating becomes effective. thus, the non-gaussian feature of the spatial distribution of the 21 cm signal is expected to be useful to investigate the astrophysical effects in the cd and eor. in this paper, in order to investigate such a non-gaussian feature in more detail, we focus on the bispectrum of the 21 cm signal. it is expected that the 21 cm brightness temperature bispectrum is produced by non-gaussianity due to the various astrophysical effects such as the wouthuysen-field effect, x-ray heating and reionization. we study the various properties of 21 cm bispectrum such as scale dependence, shape dependence and redshift evolution. and also we study the contribution from each component of 21 cm bispectrum. we find that the contribution from each component has characteristic scale-dependent feature. in particular, we find that the bulk of the 21 cm bispectrum at z = 20 comes from the matter fluctuations, while in other epochs it is mainly determined by the spin and/or neutral fraction fluctuations and it is expected that we could obtain more detailed information on the igm in the cd and eor by using the 21 cm bispectrum in the future experiments, combined with the power spectrum and skewness. | 21 cm line bispectrum as a method to probe cosmic dawn and epoch of reionization |
the announcement by bicep2 of the detection of b-mode polarization consistent with primordial gravitational waves with a tensor-to-scalar ratio, r=0.2+0.07-0.05, challenged predictions from most inflationary models of a lower value for r. more recent results by planck on polarized dust emission show that the observed tensor modes signal is compatible with pure foreground emission. a more significant constraint on r was then obtained by a joint analysis of planck, bicep2 and keck array data showing an upper limit to the tensor to scalar ratio r≤ 0.12, excluding the case 0r= with low statistical significance. forthcoming measurements by bicep3, the keck array, and other cmb polarization experiments, open the possibility for making the fundamental measurement of r. here we discuss how r sets the scale for models where the dark matter is created at the inflationary epoch, the generically called super-heavy dark matter models. we also consider the constraints on such scenarios given by recent data from ultrahigh energy cosmic ray observatories which set the limit on super-heavy dark matter particles lifetime. we discuss how super-heavy dark matter can be discovered by a precise measurement of r combined with future observations of ultra high energy cosmic rays. | super heavy dark matter in light of bicep2, planck and ultra high energy cosmic rays observations |
the energy range between about 100 kev and 1 gev is of interest for a vast class of astrophysical topics. in particular, (1) it is the missing ingredient for understanding extreme processes in the multi-messenger era; (2) it allows localizing cosmic-ray interactions with background material and radiation in the universe, and spotting the reprocessing of these particles; (3) last but not least, gamma-ray emission lines trace the formation of elements in the galaxy and beyond. in addition, studying the still largely unexplored mev domain of astronomy would provide for a rich observatory science, including the study of compact objects, solar- and earth-science, as well as fundamental physics. the technological development of silicon microstrip detectors makes it possible now to detect mev photons in space with high efficiency and low background. during the last decade, a concept of detector ("astrogam") has been proposed to fulfil these goals, based on a silicon hodoscope, a 3d position-sensitive calorimeter, and an anticoincidence detector. in this paper we stress the importance of a medium size (m-class) space mission, dubbed "astromev", to fulfil these objectives. | gamma-ray astrophysics in the mev range |
the fermi bubbles are two giant bubbles in gamma-rays lying above and below the galactic center (gc). despite numerous studies on the bubbles, their origin and emission mechanism remain elusive. here we use a suite of hydrodynamic simulations to study the scenario where the cosmic rays (crs) in the bubbles are mainly accelerated at the forward shocks driven by a pair of opposing jets from sgr a*. we find that an active galactic nucleus (agn) jet event that happened 5-6 myr ago can naturally reproduce the bilobular morphology of the bubbles, and the postshock gas temperature in the bubbles is heated to ∼0.4 kev, consistent with recent x-ray observations. the forward shocks compress the hot halo gas, and at low latitudes, the compressed gas shows an x-shaped structure, naturally explaining the biconical x-ray structure in the rosat 1.5 kev map in both morphology and x-ray surface brightness. cr acceleration is most efficient in the head regions of the bubbles during the first 2 myr. the opposing jets release a total energy of ∼1055 erg with an eddington ratio of ∼10-3, which falls well in the range of the hot accretion flow mode for black holes. our simulations further show that the forward shocks driven by spherical winds at the gc typically produce bubbles with much wider bases than observed and could not reproduce the biconical x-ray structure at low latitudes. this suggests that starburst or agn winds are unlikely the origin of the bubbles in the shock scenario. | simulating the fermi bubbles as forward shocks driven by agn jets |
we investigate the possibilities for probing mev dark matter (dm) particles and primordial black holes (pbhs) (for masses ~ 1015-1017 g) at the upcoming radio telescope ska, using photon signals from the inverse compton (ic) effect within a galactic halo. pair-annihilation or decay of mev dm particles (into e+ e- pairs) or hawking radiation from a population of pbhs generates mildly relativistic e± which can lead to radio signals through the ic scattering on low energy cosmic microwave background (cmb) photons. we study the ability of ska to detect such signals coming from nearby ultra-faint dwarf galaxies segue i and ursa major ii as well as the globular cluster ω-cen and the coma cluster. we find that with ~ 100 hours of observation, the ska improves the planck constraints on the dm annihilation/decay rate and the pbh abundance for masses in the range ~ 1 to few tens of mev and above 1015 to 1017 g, respectively. importantly, the ska limits are independent of the assumed magnetic fields within the galaxies. previously allowed regions of diffusion parameters of mev electrons inside a dwarf galaxy that give rise to observable signals at the ska are also excluded. for objects like dwarf galaxies, predicted ska constraints depend on both the dm and diffusion parameters. independent observations in different frequency bands, e.g., radio and γ-ray frequencies, may break this degeneracy and thus enable one to constrain the combined parameter space of dm and diffusion. however, the constraints are independent of diffusion parameters for galaxy clusters such as coma. | constraints on mev dark matter and primordial black holes: inverse compton signals at the ska |
we study the problem of the escape and transport of cosmic rays (crs) from a source embedded in a fully ionized, hot phase of the interstellar medium (him). in particular, we model the cr escape and their propagation in the source vicinity taking into account excitation of alfvénic turbulence by cr streaming and mechanisms damping the self-excited turbulence itself. our estimates of escape radii and times result in large values (100 pc, 2 × 105 yr) for particle energies ≲ 20 gev and smaller values for particles with increasing energies (35 pc and 14 kyr at 1 tev). these escape times and radii, when used as initial conditions for the cr propagation outside the source, result in relevant suppression of the diffusion coefficient (by a factor 5-10) on time-scales comparable with their (energy dependent) escape time-scale. the damping mechanisms are fast enough that even on shorter time-scales, the alfvénic turbulence is efficiently damped, and the ratio between random and ordered component of the magnetic field is δb/b0 ≪ 1, justifying the use of quasi-linear theory. in spite of the suppressed diffusion coefficient, and then the increased residence time in the vicinity (≤200 pc) of their source, the grammage accumulated by crs after their escape is found to be negligible (at all energies) as compared to the one accumulated while diffusing in the whole galaxy, due to the low density of the him. | non-linear diffusion of cosmic rays escaping from supernova remnants - ii. hot ionized media |
context. ultra-low frequency observations (< 100 mhz) are particularly challenging because they are usually performed in a low signal-to-noise ratio regime due to the high sky temperature and because of ionospheric disturbances whose effects are inversely proportional to the observing frequency. nonetheless, these observations are crucial for studying the emission from low-energy populations of cosmic rays.aims: we aim to obtain the first thermal-noise limited (∼1.5 mjy beam-1) deep continuum radio map using the low frequency array's low band antenna (lofar lba) system. our demonstration observation targeted the galaxy cluster rx j0603.3+4214 (known as the toothbrush cluster). we used the resulting ultra-low frequency (39-78 mhz) image to study cosmic-ray acceleration and evolution in the post shock region considering the presence of a radio halo.methods: we describe the data reduction we used to calibrate lofar lba observations. the resulting image was combined with observations at higher frequencies (lofar 150 mhz and vla 1500 mhz) to extract spectral information.results: we obtained the first thermal-noise limited image from an observation carried out with the lofar lba system using all dutch stations at a central frequency of 58 mhz. with eight hours of data, we reached an rms noise of 1.3 mjy beam-1 at a resolution of 18″ × 11″.conclusions: the procedure we developed is an important step towards routine high-fidelity imaging with the lofar lba. the analysis of the radio spectra shows that the radio relic extends to distances of 800 kpc downstream from the shock front, larger than what is allowed by electron cooling time. furthermore, the shock wave started accelerating electrons already at a projected distance of < 300 kpc from the crossing point of the two clusters. these results may be explained by electrons being re-accelerated downstream by background turbulence, possibly combined with projection effects with respect to the radio halo. the reduced images 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/a85 | reaching thermal noise at ultra-low radio frequencies. toothbrush radio relic downstream of the shock front |
recent precise measurements of cosmic ray spectra revealed an anomalous hardening at ∼200 gv, observed by the atic, cream, pamela, and ams02 experiments. particularly, the latest observation of the \bar{p}/p ratio by ams02 demonstrated a flat distribution, which further validated the spectral anomalies of secondary particles. all those new phenomena indicated that the conventional propagation model of cosmic rays meets a challenge. in this work, the spatial-dependent diffusion coefficient d(r,z,p) is employed by tracing the source distribution under the physical picture of the two-halo model in the dragon package. under such a scenario, the model calculation will result in two-component spectra for primary nuclei. due to the smaller rigidity dependence of d(r,z,p) in the galactic disk, the ratios secondary-to-primary will inevitably be flatter and the expected anisotropy of cosmic rays will be much more attenuated than in the conventional model. as a result, we can reproduce the spectral hardening of protons, the flat ratios of \bar{p}/p and b/c, and consistent anisotropy from ∼100 gev to ∼100 tev by only adopting one set of spatial-dependent diffusion coefficients d(r,z,p) in a galactic disk. | spatial-dependent propagation of cosmic rays results in the spectrum of proton, ratios of p/p, and b/c, and anisotropy of nuclei |
broadband radio frequency (rf) interferometry was first introduced in 1996 for lightning studies. the technique has since been improved significantly and has been increasingly widely used in the lightning community. in addition to the interferometry, we now introduce a broadband polarization capability that simultaneously measures the full polarization state of the corresponding rf sources. polarization observation provides another level of understanding of the discharge processes. in this paper, we describe the new system and present example observations with such a system. initial observations of impulsive lightning rf pulses, a k-event leader, and the initiating process for an intracloud flash are presented. the impulsive pulses were often linearly polarized and are consistent with conventional breakdown processes, whereas some occasional pulses were elliptically polarized and are likely related to relativistic breakdown processes. the k-event was detected polarized along a section of its channel, and the orientation of the polarization was mostly orthogonal to the channel, apparently due to the preceding charge deposition along the channel. the intracloud flash in this paper was initiated with downward fast positive streamers, and the corresponding signals were linearly polarized, consistent with conventional breakdown processes. the orientations of the polarization were nearly uniformly aligned with the propagation direction of the streamers, indicating a near uniform electric field in the region of the initiating streamers. finally, an observation of a cosmic-ray shower is presented. | broadband rf interferometric mapping and polarization (bimap) observations of lightning discharges: revealing new physics insights into breakdown processes |
cancer risk is an important concern for galactic cosmic ray (gcr) exposures, which consist of a wide-energy range of protons, heavy ions and secondary radiation produced in shielding and tissues. relative biological effectiveness (rbe) factors for surrogate cancer endpoints in cell culture models and tumor induction in mice vary considerable, including significant variations for different tissues and mouse strains. many studies suggest non-targeted effects (nte) occur for low doses of high linear energy transfer (let) radiation, leading to deviation from the linear dose response model used in radiation protection. using the mouse harderian gland tumor experiment, the only extensive data-set for dose response modelling with a variety of particle types (>4), for the first-time a particle track structure model of tumor prevalence is used to investigate the effects of ntes in predictions of chronic gcr exposure risk. the nte model led to a predicted risk 2-fold higher compared to a targeted effects model. the scarcity of data with animal models for tissues that dominate human radiation cancer risk, including lung, colon, breast, liver, and stomach, suggest that studies of ntes in other tissues are urgently needed prior to long-term space missions outside the protection of the earth's geomagnetic sphere. | non-targeted effects models predict significantly higher mars mission cancer risk than targeted effects models |
we estimate the intensity of interstellar pickup protons accelerated to ∼50 kev at various locations along the solar-wind termination shock, using two-dimensional hybrid simulations. parameters for the solar wind, interstellar pickup ions (puis), and magnetic field just upstream of the termination shock at one flank of the heliosphere, and at the location in the downwind (or tail-ward) direction are based on a solar-wind/pickup-ion/turbulence model. the parameters upstream of the shock where voyager 2 crossed are based on observations. the simulation is limited in size, and therefore cannot accurately model the distribution to energies much beyond ∼50 kev. this is sufficient to study the origin of the high-energy tail of the distribution, which is the low-energy portion of the anomalous cosmic-ray spectrum. we also extrapolate our results to other locations along the termination shock, such as the other flank, and the poles of the heliosphere. we find that the intensity of ∼10-50 kev accelerated pickup protons is remarkably similar at all three locations we simulated, suggesting that particles in this energy range are relatively uniformly distributed along the termination shock, and are likely quite uniform throughout the entire heliosheath. in addition, we find significant differences in the distribution in the 0.5-1 kev energy range for energetic neutral atoms coming from the tail region of the heliosphere compared to that at the nose or flank look directions. this is because the peak in the pui distribution is at a higher energy there. | hybrid simulations of interstellar pickup protons accelerated at the solar-wind termination shock at multiple locations |
the andromeda galaxy is the closest spiral galaxy to us and has been the subject of numerous studies. it harbors a massive dark matter halo, which may span up to ∼600 kpc across and comprises ∼90% of the galaxy’s total mass. this halo size translates into a large diameter of 42° on the sky, for an m31-milky way (mw) distance of 785 kpc, but its presumably low surface brightness makes it challenging to detect with γ-ray telescopes. using 7.6 yr of fermi large area telescope (fermi-lat) observations, we make a detailed study of the γ-ray emission between 1-100 gev toward m31's outer halo, with a total field radius of 60° centered at m31, and perform an in-depth analysis of the systematic uncertainties related to the observations. we use the cosmic-ray propagation code galprop to construct specialized interstellar emission models to characterize the foreground γ-ray emission from the mw, including a self-consistent determination of the isotropic component. we find evidence for an extended excess that appears to be distinct from the conventional mw foreground, having a total radial extension upward of ∼120-200 kpc from the center of m31. we discuss plausible interpretations of the excess emission, but emphasize that uncertainties in the mw foreground—and in particular, modeling of the h i-related components—have not been fully explored and may impact the results. | fermi-lat observations of γ-ray emission toward the outer halo of m31 |
we report the properties of primary cosmic-ray sulfur (s) in the rigidity range 2.15 gv to 3.0 tv based on 0.38 ×106 sulfur nuclei collected by the alpha magnetic spectrometer experiment (ams). we observed that above 90 gv the rigidity dependence of the s flux is identical to the rigidity dependence of ne-mg-si fluxes, which is different from the rigidity dependence of the he-c-o-fe fluxes. we found that, similar to n, na, and al cosmic rays, over the entire rigidity range, the traditional primary cosmic rays s, ne, mg, and c all have sizeable secondary components, and the s, ne, and mg fluxes are well described by the weighted sum of the primary silicon flux and the secondary fluorine flux, and the c flux is well described by the weighted sum of the primary oxygen flux and the secondary boron flux. the primary and secondary contributions of the traditional primary cosmic-ray fluxes of c, ne, mg, and s (even z elements) are distinctly different from the primary and secondary contributions of the n, na, and al (odd z elements) fluxes. the abundance ratio at the source for s /si is 0.167 ±0.006 , for ne /si is 0.833 ±0.025 , for mg /si is 0.994 ±0.029 , and for c /o is 0.836 ±0.025 . these values are determined independent of cosmic-ray propagation. | properties of cosmic-ray sulfur and determination of the composition of primary cosmic-ray carbon, neon, magnesium, and sulfur: ten-year results from the alpha magnetic spectrometer |
the study of rare fundamental physics phenomena, such as double-beta decay, rare nuclear decays and dark matter, requires very low levels of background radiation in order to observe a signal. to achieve the required background levels, experiments are located deep underground as these facilities provide significant rock overburden and commensurate reduction in the cosmic ray flux and cosmic ray-spallation induced products. an overview of the sources of these backgrounds will be presented. taking advantage of the deep underground laboratory spaces, there have been a growing number of underground measurements in other fields, including environmental monitoring, benchmarking of other physical techniques, life science studies in low background environments, and material selection. the exceptional sensitivity and high resolution of high-purity germanium detectors allows for very sensitive measurements using gamma-ray spectrometry. their use has been increasing as they allow for non-destructive measurements of experiment components, which can be directly used if they meet specified background requirements. this paper will discuss the current most sensitive ultra-low background germanium detectors in operation and explain how to achieve the best level of background reduction to attain the best sensitivities. in addition, an overview of several complementary low background measurement methods will be discussed. a proposed program to cross calibrate germanium detectors at several laboratories will be described and a searchable database used to store radioactivity measurements of experimental materials will be introduced. | low background radiation detection techniques and mitigation of radioactive backgrounds |
it is well known that the fraction of energy in a hadron collision going into electromagnetic particles (electrons and photons, including those from decays) has a large impact on the number of muons produced in air shower cascades. recent measurements at the lhc confirm features that can be linked to a mixture of different underlying particle production mechanisms such as a collective statistical hadronization (core) in addition to the expected string fragmentation (corona). since the two mechanisms have a different electromagnetic energy fraction, we present a possible connection between statistical hadronization in hadron collisions and muon production in air showers. using a novel approach, we demonstrate that the core-corona effect as observed at the lhc can have a significant impact and should be properly taken into account before trying to find a more exotic solution for the lack of muon production in simulations of high energy cosmic rays. | core-corona effect in hadron collisions and muon production in air showers |
features and peculiarities of the cosmic ray intensity (cri) and the geomagnetic activity, along with several solar plasma and interplanetary magnetic field, during the period 4-10 september 2017 are studied. the period was characterized by strong solar activity: several solar flares occurred; several halo coronal mass ejections (cmes) were ejected in space. in the near-earth interplanetary space, the cmes driving shock(s) and sheath(s) were identified. at the earth, strong forbush decreases in cri and geomagnetic storms were observed. several large solar flares, one of them of very high x-ray importance (x9.3) and three halo cmes were detected in the solar atmosphere. two shock-associated interplanetary cmes were observed during that interval in near-earth space; the latter and faster one arrived even as the ejecta of the earlier one was still crossing. variations in interplanetary plasma and field parameters during, before, and after the forbush decreases and geomagnetic storms that occurred during the considered period were examined. a detailed time-lagged correlation analysis using data at three different temporal resolutions (hourly, 5-min, and 1-min) was also performed. cross correlations of time series of cri with geomagnetic activity during the period 4-10 september 2017 are computed. this cross-correlation analysis between cri variability (defined as the difference of the cri count rate between the current and the previous time step) and the dst indicates a delay of dst by 3-4 hr. | forbush decreases and geomagnetic storms during a highly disturbed solar and interplanetary period, 4-10 september 2017 |
we determined interstellar cosmic ray exposure ages of 40 large presolar silicon carbide grains extracted from the murchison cm2 meteorite. our ages, based on cosmogenic ne-21, range from 3.9 ± 1.6 ma to ∼3 ± 2 ga before the start of the solar system ∼4.6 ga ago. a majority of the grains have interstellar lifetimes of <300 ma, which is shorter than theoretical estimates for large grains. these grains condensed in outflows of asymptotic giant branch stars <4.9 ga ago that possibly formed during an episode of enhanced star formation ∼7 ga ago. a minority of the grains have ages >1 ga. longer lifetimes are expected for large grains. we determined that at least 12 of the analyzed grains were parts of aggregates in the interstellar medium: the large difference in nuclear recoil loss of cosmic ray spallation products 3he and 21ne enabled us to estimate that the irradiated objects in the interstellar medium were up to 30 times larger than the analyzed grains. furthermore, we estimate that the majority of the grains acquired the bulk of their cosmogenic nuclides in the interstellar medium and not by exposure to an enhanced particle flux of the early active sun. | lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide |
cosmic-ray acceleration has been a long-standing mystery1,2 and, despite more than a century of study, we still do not have a complete census of acceleration mechanisms. the collision of strong stellar winds in massive binary systems creates powerful shocks that have been expected to produce high-energy cosmic rays through fermi acceleration at the shock interface. the accelerated particles should collide with stellar photons or ambient material, producing non-thermal emission observable in x-rays and γ-rays3,4. the supermassive binary star eta carinae (η car) drives the strongest colliding wind shock in the solar neighbourhood5,6. observations with non-focusing high-energy observatories indicate a high-energy source near η car, but have been unable to conclusively identify η car as the source because of their relatively poor angular resolution7-9. here we present direct focussing observations of the non-thermal source in the extremely hard x-ray band, which is found to be spatially coincident with the star within several arc-seconds. these observations show that the source of non-thermal x-rays varies with the orbital phase of the binary, and that the photon index of the emission is similar to that derived through analysis of the γ-ray spectrum. this is conclusive evidence that the high-energy emission indeed originates from non-thermal particles accelerated at colliding wind shocks. | non-thermal x-rays from colliding wind shock acceleration in the massive binary eta carinae |
context. the space based γ-ray observatory integral of the european space agency (esa) includes the spectrometer instrument "spi". this is a coded mask telescope featuring a 19-element germanium detector array for high-resolution γ-ray spectroscopy, encapsulated in a scintillation detector assembly that provides a veto for background from charged particles. in space, cosmic rays irradiate spacecraft and instruments, which, in spite of the vetoing detectors, results in a large instrumental background from activation of those materials, and leads to deterioration of the charge collection properties of the ge detectors. aim. we aim to determine the measurement characteristics of our detectors and their evolution with time, that is, their spectral response and instrumental background. these incur systematic variations in the spi signal from celestial photons, hence their determination from a broad empirical database enables a reduction of underlying systematics in data analysis. for this, we explore compromises balancing temporal and spectral resolution within statistical limitations. our goal is to enable modelling of background applicable to spectroscopic studies of the sky, accounting separately for changes of the spectral response and of instrumental background.methods: we use 13.5 years of integral/spi data, which consist of spectra for each detector and for each pointing of the satellite. spectral fits to each such spectrum, with independent but coherent treatment of continuum and line backgrounds, provides us with details about separated background components. from the strongest background lines, we first determine how the spectral response changes with time. applying symmetry and long-term stability tests, we eliminate degeneracies and reduce statistical fluctuations of background parameters, with the aim of providing a self-consistent description of the spectral response for each individual detector. accounting for this, we then determine how the instrumental background components change in intensities and other characteristics, most-importantly their relative distribution among detectors.results: spectral resolution of ge detectors in space degrades with time, up to 15% within half a year, consistently for all detectors, and across the spi energy range. semi-annual annealing operations recover these losses, yet there is a small long-term degradation. the intensity of instrumental background varies anti-correlated to solar activity, in general. there are significant differences among different lines and with respect to continuum. background lines are found to have a characteristic, well-defined and long-term consistent intensity ratio among detectors. we use this to categorise lines in groups of similar behaviour. the dataset of spectral-response and background parameters as fitted across the integral mission allows studies of spi spectral response and background behaviour in a broad perspective, and efficiently supports precision modelling of instrumental background. | integral/spi γ-ray line spectroscopy. response and background characteristics |
several starburst galaxies have been observed in the gev and tev bands. in these dense environments, gamma-ray emission should be dominated by cosmic ray (cr) interactions with the interstellar medium (pcrpism → π0 → γγ). indeed, starbursts may act as proton `calorimeters' where a substantial fraction of cr energy input is emitted in gamma-rays. here, we build a one-zone, `thick-target' model implementing calorimetry and placing a firm upper bound on gamma-ray emission from cr interactions. the model assumes that crs are accelerated by supernovae (sne), and all suffer nuclear interactions rather than escape. our model has only two free parameters: the cr proton acceleration energy per sn ɛcr, and the proton injection spectral index s. we calculate the pionic gamma-ray emission from 10 mev to 10 tev, and derive thick-target parameters for six galaxies with fermi, h.e.s.s., and/or veritas data. our model provides good fits for the m82 and ngc 253, and yields ɛcr and s values suggesting that sn cr acceleration is similar in starbursts and in our galaxy. we find that these starbursts are indeed nearly if not fully proton calorimeters. for ngc 4945 and ngc 1068, the models are consistent with calorimetry but are less well-constrained due to the lack of tev data. however, the circinus galaxy and the ultra-luminous infrared galaxy arp 220 exceed our pionic upper-limit; possible explanations are discussed. | are starburst galaxies proton calorimeters? |
the south pole, which hosts the icecube neutrino observatory, has a complete and around-the-clock exposure to the galactic center. hence, it is an ideal location to search for gamma rays of pev energy coming from the galactic center. however, it is hard to detect air showers initiated by these gamma rays using cosmic-ray particle detectors due to the low elevation of the galactic center. the use of antennas to measure the radio footprint of these air showers will help in this case, and would allow for a 24/7 operation time. so far, only air showers with energies well above 1016 ev have been detected with the radio technique. thus, the energy threshold has to be lowered for the detection of gamma-ray showers of pev energy. this can be achieved by optimizing the frequency band in order to obtain a higher level of signal-to-noise ratio. with such an approach, pev gamma-ray showers with high inclination can be measured at the south pole. | search for pevatrons at the galactic center using a radio air-shower array at the south pole |
in the last 40 years a wide range of molecules, including neutrals, cations and anions, containing up to 13 atoms—in addition to detections of {{\text{c}}60} and {{\text{c}}70} —have been found in the harsh environment of the interstellar medium. the exquisite sensitivity and very high spectral and, more recently, spatial resolution, of modern telescopes has enabled the physics of star formation to be probed through rotational line emission. in this article, i review the basic properties of interstellar clouds and the processes that initiate the chemistry and generate chemical complexity, particularly in regions of star and planet formation. our understanding of astrochemistry has evolved over the years. before 1990, the general consensus was that molecules were formed in binary, gas-phase, or volume, reactions, most importantly ion-neutral reactions despite the very low ionization in clouds. since then, observations have indicated unambiguously that there is also a contribution from surface processes, particularly on the icy mantles that form around refractory grain cores in cold, dense gas. the balance between these two processes depends on particular physical conditions and can vary during the life cycle of a particular volume of interstellar cloud. the complex chemistry that occurs in space is driven mostly through interaction of the gas with cosmic ray protons, a source of ionization that enables a rich ion-neutral chemistry. in addition, i show that the interaction between the gas and the dust in cold, dense regions also leads to additional chemical complexity through reactions that take place in ices at only a few tens of degrees above absolute zero. although densities are low compared to those in terrestrial environments, the extremely long life times of interstellar clouds and their enormous sizes, enable complex molecules to be synthesised and detected. i show that in some instances, particularly in reactions involving deuterium, the rotational populations of reactants, together with spin-selection rules, can determine the detailed abundances. although the review is mainly focused on regions associated with star formation, i also consider chemistry in other interesting astronomical regions—in the early universe and in the envelopes formed by mass loss during the final stages of stellar evolution. | astrochemistry |
a base board for photomultiplier tube (pmt) with multi-dynode readout has been developed for the bgo electromagnetic calorimeter (ecal) of the dark matter particle explorer (dampe). in order to cover a high dynamic range of energy measurements, the signals are read out from different sensitive dynodes 2, 5, and 8 (dy2, dy5 and dy8). the performance of this new type of base board is studied with a light-emitting diode (led) system and cosmic rays. a wide measuring range from 0.5 to 1.0×105 mips can be achieved using the va32 readout application specific integrated circuit (asic). | design of a high dynamic range photomultiplier base board for the bgo ecal of dampe |
we investigate a mechanism for accelerating cool (104 k) clouds in the circumgalactic medium (cgm) with cosmic rays (crs), possibly explaining some characteristics of observed high-velocity clouds (hvcs). enforcing crs to stream down their pressure gradient into a region of slow streaming speed results in significant build-up of cr pressure which can accelerate the cgm. we present the results of the first two-dimensional magnetohydrodynamic (mhd) simulations of such `cr bottlenecks,' expanding on simpler simulations in 1d. although much more investigation is required, we find two main results. first, radiative cooling in the interfaces of these clouds is sufficient to keep the cloud intact to cr wave heating. secondly, cloud acceleration depends almost linearly with the injected cr flux at low values (comparable to that expected from a milky way-like star formation rate), but scales sublinearly at higher cr fluxes in 1d simulations. 2d simulations show hints of sublinear dependence at high cr fluxes but are consistent with pure linear dependence up to the cr fluxes tested. it may therefore be plausible to accelerate cool clouds in the cgm to speeds of hundreds of km s-1. | cosmic ray acceleration of cool clouds in the circumgalactic medium |
starburst galaxies and star-forming active galactic nuclei are among the candidate sources thought to contribute appreciably to the extragalactic gamma-ray and neutrino backgrounds. ngc 1068 is the brightest of the star-forming galaxies found to emit gamma-rays from 0.1 to 50 gev. precise measurements of the high-energy spectrum are crucial to study the particle accelerators and probe the dominant emission mechanisms. we have carried out 125 hr of observations of ngc 1068 with the magic telescopes in order to search for gamma-ray emission in the very-high-energy band. we did not detect significant gamma-ray emission, and set upper limits at the 95% confidence level to the gamma-ray flux above 200 gev f < 5.1 × 10-13 cm-2 s-1. this limit improves previous constraints by about an order of magnitude and allows us to put tight constraints on the theoretical models for the gamma-ray emission. by combining the magic observations with the fermi-lat spectrum we limit the parameter space (spectral slope, maximum energy) of the cosmic ray protons predicted by hadronuclear models for the gamma-ray emission, while we find that a model postulating leptonic emission from a semi-relativistic jet is fully consistent with the limits. we provide predictions for icecube detection of the neutrino signal foreseen in the hadronic scenario. we predict a maximal icecube neutrino event rate of 0.07 yr-1. | constraints on gamma-ray and neutrino emission from ngc 1068 with the magic telescopes |
the spectrum and morphology of the diffuse galactic γ-ray emission carries valuable information on cosmic ray (cr) propagation. recent results obtained by analyzing fermi-lat data accumulated over 7 yr of observation show a substantial variation of the cr spectrum as a function of the distance from the galactic centre. the spatial distribution of the cr density in the outer galaxy appears to be weakly dependent upon the galactocentric distance, as found in previous studies as well, while the density in the central region of the galaxy was found to exceed the value measured in the outer galaxy. at the same time, fermi-lat data suggest a gradual spectral softening while moving outwards from the centre of the galaxy to its outskirts. these findings represent a challenge for standard calculations of cr propagation based on assuming a uniform diffusion coefficient within the galactic volume. here, we present a model of non-linear cr propagation in which transport is due to particle scattering and advection off self-generated turbulence. we find that for a realistic distribution of cr sources following the spatial distribution of supernova remnants and the space dependence of the magnetic field on galactocentric distance, both the spatial profile of cr density and the spectral softening can easily be accounted for. | on the radial distribution of galactic cosmic rays |
the distribution of chemical elements in the hot intracluster medium (icm) retains valuable information about the enrichment and star formation histories of galaxy clusters, and on the feedback and dynamical processes driving the evolution of the cosmic baryons. in the present study we review the progresses made so far in the modelling of the icm chemical enrichment in a cosmological context, focusing in particular on cosmological hydrodynamical simulations. we will review the key aspects of embedding chemical evolution models into hydrodynamical simulations, with special attention to the crucial assumptions on the initial stellar mass function, stellar lifetimes and metal yields, and to the numerical limitations of the modelling. at a second stage, we will overview the main simulation results obtained in the last decades and compare them to x-ray observations of the icm enrichment patterns. in particular, we will discuss how state-of-the-art simulations are able to reproduce the observed radial distribution of metals in the icm, from the core to the outskirts, the chemical diversity depending on cluster thermo-dynamical properties, the evolution of icm metallicity and its dependency on the system mass from group to cluster scales. finally, we will discuss the limitations still present in modern cosmological, chemical, hydrodynamical simulations and the perspectives for improving the theoretical modelling of the icm enrichment in galaxy clusters in the future. | enrichment of the hot intracluster medium: numerical simulations |
high-energy cosmic neutrino observations provide a sensitive test of lorentz invariance violation (liv), which may be a consequence of quantum gravity theories. we consider a class of nonrenormalizable, lorentz invariance violating operators that arise in an effective field theory (eft) description of lorentz invariance violation in the neutrino sector inspired by planck-scale physics and quantum gravity models. we assume a conservative generic scenario for the redshift distribution of extragalactic neutrino sources and employ monte carlo techniques to describe superluminal neutrino propagation, treating kinematically allowed energy losses of superluminal neutrinos caused by both vacuum pair emission (vpe) and neutrino splitting. we consider efts with both nonrenormalizable c p t -odd and nonrenormalizable c p t -even operator dominance. we then compare the spectra derived using our monte carlo calculations in both cases with the spectrum observed by icecube in order to determine the implications of our results regarding planck-scale physics. we find that if the dropoff in the neutrino flux above ∼2 pev is caused by planck-scale physics, rather than by a limiting energy in the source emission, a potentially significant pileup effect would be produced just below the dropoff energy in the case of c p t -even operator dominance. however, such a clear dropoff effect would not be observed if the c p t -odd, c p t -violating term dominates. | searching for traces of planck-scale physics with high energy neutrinos |
luminous infrared galaxies and submillimeter galaxies contribute significantly to stellar mass assembly and provide an important test of the connection between the gamma-ray burst (grb) rate and that of overall cosmic star formation. we present sensitive 3 ghz radio observations using the karl g. jansky very large array of 32 uniformly selected grb host galaxies spanning a redshift range from 0 < z < 2.5, providing the first fully dust- and sample-unbiased measurement of the fraction of grbs originating from the universe's most bolometrically luminous galaxies. four galaxies are detected, with inferred radio star formation rates (sfrs) ranging between 50 and 300 m ⊙ yr-1. three of the four detections correspond to events consistent with being optically obscured "dark" bursts. our overall detection fraction implies that between 9% and 23% of grbs between 0.5 < z < 2.5 occur in galaxies with s 3ghz > 10 μjy, corresponding to sfr > 50 m ⊙ yr-1 at z ~ 1 or >250 m ⊙ yr-1 at z ~ 2. similar galaxies contribute approximately 10%-30% of all cosmic star formation, so our results are consistent with a grb rate that is not strongly biased with respect to the total sfr of a galaxy. however, all four radio-detected hosts have stellar masses significantly lower than ir/submillimeter-selected field galaxies of similar luminosities. we suggest that the grb rate may be suppressed in metal-rich environments but independently enhanced in intense starbursts, producing a strong efficiency dependence on mass but little net dependence on bulk galaxy sfr. | connecting grbs and ulirgs: a sensitive, unbiased survey for radio emission from gamma-ray burst host galaxies at 0 < z < 2.5 |
cosmic rays interacting in the solar atmosphere produce showers that result in a flux of high-energy neutrinos from the sun. these form an irreducible background to indirect solar wimp self-annihilation searches, which look for heavy dark matter particles annihilating into final states containing neutrinos in the solar core. this background will eventually create a sensitivity floor for indirect wimp self-annihilation searches analogous to that imposed by low-energy solar neutrino interactions for direct dark matter detection experiments. we present a new calculation of the flux of solar atmospheric neutrinos with a detailed treatment of systematic uncertainties inherent in solar atmospheric shower evolution, and we use this to derive the sensitivity floor for indirect solar wimp annihilation analyses. we find that the floor lies less than one order of magnitude beyond the present experimental limits on spin-dependent wimp-proton cross sections for some mass points, and that the high-energy solar atmospheric neutrino flux may be observable with running and future neutrino telescopes. | solar atmospheric neutrinos and the sensitivity floor for solar dark matter annihilation searches |
atmospheric mass loss plays a major role in the evolution of exoplanets. this process is driven by the stellar high-energy irradiation, especially in the first hundreds of millions of years after dissipation of the proto-planetary disk. a major source of uncertainty in modeling atmospheric photoevaporation and photochemistry is due to the lack of direct measurements of the stellar flux at extreme-uv (euv) wavelengths. several empirical relationships have been proposed in the past to link euv fluxes to emission levels in x-rays, but the stellar samples employed for this aim are heterogeneous, and the available scaling laws provide significantly different predictions, especially for very active stars. we present new far-uv and x-ray observations of v1298 tau with hubble space telescope/cosmic origins spectrograph and xmm-newton, aimed to determine more accurately the high-energy emission of this solar-mass pre-main-sequence star, which hosts four exoplanets. spectroscopic data were employed to derive the plasma emission measure distribution versus temperature, from the chromosphere to the corona, and the possible variability of this irradiation on short and year-long timescales, due to magnetic activity. as a side result, we have also measured the chemical abundances of several elements in the outer atmosphere of v1298 tau. we employ our results as a new benchmark point for the calibration of the x-ray to euv scaling laws, and hence to predict the time evolution of the irradiation in the euv band, and its effect on the evaporation of exo-atmospheres. | x-ray and ultraviolet emission of the young planet-hosting star v1298 tau from coordinated observations with xmm-newton and hubble space telescope |
the telescope array collaboration has reported an evidence for existence of a source of ultrahigh-energy cosmic ray events in perseus-pisces supercluster. we show that the mere existence of such a source imposes an upper bound on the strength of intergalactic magnetic field (igmf) in the taurus void lying between the perseus-pisces supercluster and the milky way galaxy. this limit is at the level of 10-10 g for a field with correlation length larger than the distance of the supercluster (∼70 mpc ). this bound is an order-of-magnitude stronger that the previously known bound on igmf from radio faraday rotation measurements and it is the first upper bound on magnetic field in the voids of the large-scale tructure. our analysis indicates that the source has to be dominated by protons, because heavier nuclei are either photodisintegrated or are too strongly deflected by the galactic magnetic field. | limit on the intergalactic magnetic field from the ultrahigh-energy cosmic ray hotspot in the perseus-pisces region |
the distribution of the cosmic convergence field is modelled using a large deviation principle where all non-gaussian contributions are computed from first principles. the geometry of the past light-cone is accounted for by constructing the total weak-lensing signal from contributions of the matter density in thin disc slices. the prediction of this model is successfully tested against numerical simulation with ray-tracing, and found to be accurate within at least 5 per cent in the tails at redshift 1 and opening angle of 10 arcmin and even more so with increasing source redshift and opening angle. an accurate analytical approximation to the theory is also provided for practical implementation. the lensing kernel that mixes physical scales along the line of sight tends to reduce the domain of validity of this theoretical approach compared to the three-dimensional case of cosmic densities in spherical cells. this effect is shown to be avoidable if a nulling procedure is implemented in order to localize the lensing line-of-sight integrations in a tomographic analysis. accuracy in the tails is thus achieved within a per cent for source redshifts between 0.5 and 1.5 and an opening angle of 10 arcmin. applications to future weak-lensing surveys like euclid and the specific issue of shape noise are discussed. | a nulling strategy for modelling lensing convergence in cones with large deviation theory |
we argue that charged dust grains could significantly impact the confinement and transport of galactic cosmic rays. for sub-gev to ~103 gev cosmic rays, small-scale parallel alfvén waves, which isotropize cosmic rays through gyro-resonant interactions, are also gyro-resonant with charged grains. if the dust is nearly stationary, as in the bulk of the interstellar medium, alfvén waves are damped by dust. this will reduce the amplitude of alfvén waves produced by the cosmic rays through the streaming instability, thus enhancing cosmic ray transport. in well-ionized regions, the dust damping rate is larger by a factor of ~10 than other mechanisms that damp parallel alfvén waves at the scales relevant for ~gev cosmic rays, suggesting that dust could play a key role in regulating cosmic ray transport. in astrophysical situations in which the dust moves through the gas with super-alfvénic velocities, alfvén waves are rendered unstable, which could directly scatter cosmic rays. this interaction has the potential to create a strong feedback mechanism where dust, driven through the gas by radiation pressure, then strongly enhances the confinement of cosmic rays, increasing their capacity to drive outflows. this mechanism may act in the circumgalactic medium around star-forming galaxies and active galactic nuclei. | the impact of astrophysical dust grains on the confinement of cosmic rays |
we study the streaming instability of gev-100 gev cosmic rays (crs) and its damping in the turbulent interstellar medium (ism). we find that the damping of streaming instability is dominated by ion-neutral collisional damping in weakly ionized molecular clouds, turbulent damping in the highly ionized warm medium, and nonlinear landau damping in the galactic halo. only in the galactic halo is the streaming speed of crs close to the alfvén speed. alfvénic turbulence plays an important role in both suppressing the streaming instability and regulating the diffusion of streaming crs via magnetic field line tangling, with the effective mean free path of streaming crs in the observer frame determined by the alfvénic scale in super-alfvénic turbulence. the resulting diffusion coefficient is sensitive to alfvén mach number, which has a large range of values in the multiphase ism. super-alfvénic turbulence contributes to additional confinement of streaming crs, irrespective of the dominant damping mechanism. | cosmic ray streaming in the turbulent interstellar medium |
the classical model of massive-star mechanical feedback is based on effects at solar metallicity (z ⊙), yet feedback parameters are very different at low metallicity. metal-poor stellar winds are much weaker, and more massive supernova progenitors likely collapse directly to black holes without exploding. thus, for ~0.4 z ⊙ we find reductions in the total integrated mechanical energy and momentum of ~40% and 75%, respectively, compared to values classically expected at solar metallicity. but in particular, these changes effectively delay the onset of mechanical feedback until ages of ~10 myr. feedback from high-mass x-ray binaries could slightly increase mechanical luminosity between ages 5 and 10 myr, but it is stochastic and unlikely to be significant on this timescale. stellar dynamical mechanisms remove most massive stars from clusters well before 10 myr, which would further promote this effect; this process is exacerbated by gas retention implied by weak feedback. delayed mechanical feedback implies that radiation feedback therefore dominates at early ages, which is consistent with the observed absence of superwinds in some extreme starbursts. this scenario may lead to higher star formation efficiencies, multiple stellar populations in clusters, and higher lyman continuum escape. this could explain the giant star-forming complexes in metal-poor galaxies and the small sizes of ob superbubble shells relative to their inferred ages. it could also drive modest effects on galactic chemical evolution, including on oxygen abundances. thus, delayed low-metallicity mechanical feedback may have broad implications, including for early cosmic epochs. | delayed massive-star mechanical feedback at low metallicity |
a major uncertainty in understanding the transport and feedback of cosmic rays (crs) within and beyond our galaxy lies in the unknown cr scattering rates, which are primarily determined by wave-particle interaction at microscopic gyroresonant scales. the source of the waves for the bulk cr population is believed to be self-driven by the cr streaming instability (crsi), resulting from the streaming of crs downward a cr pressure gradient. while a balance between driving by the crsi and wave damping is expected to determine wave amplitudes and hence the cr scattering rates, the problem involves significant scale separation with substantial ambiguities based on quasi-linear theory (qlt). here we propose a novel "streaming box" framework to study the crsi with an imposed cr pressure gradient, enabling first-principles measurement of the cr scattering rates as a function of environmental parameters. by employing the magnetohydrodynamic particle-in-cell method with ion-neutral damping, we conduct a series of simulations with different resolutions and cr pressure gradients and precisely measure the resulting cr scattering rates in steady state. the measured rates show scalings consistent with qlt, but with a normalization smaller by a factor of several than typical estimates based on the single-fluid treatment of crs. a momentum-by-momentum treatment provides better estimates when integrated over momentum but is also subject to substantial deviations, especially at small momentum. our framework thus opens up the path toward providing comprehensive subgrid physics for macroscopic studies of cr transport and feedback in broad astrophysical contexts. | toward first-principles characterization of cosmic-ray transport coefficients from multiscale kinetic simulations |
recently, cosmic rays (crs) have emerged as a leading candidate for driving galactic winds. small-scale processes can dramatically affect global wind properties. we run two-moment simulations of cr streaming to study how sound waves are driven unstable by phase-shifted cr forces and cr heating. we verify linear theory growth rates. as the sound waves grow non-linear, they steepen into a quasi-periodic series of propagating shocks; the density jumps at shocks create cr bottlenecks. the depth of a propagating bottleneck depends on both the density jump and its velocity; δpc is smaller for rapidly moving bottlenecks. a series of bottlenecks creates a cr staircase structure, which can be understood from a convex hull construction. the system reaches a steady state between growth of new perturbations, and stair mergers. crs are decoupled at plateaus, but exert intense forces and heating at stair jumps. the absence of cr heating at plateaus leads to cooling, strong gas pressure gradients and further shocks. if bottlenecks are stationary, they can drastically modify global flows; if their propagation times are comparable to dynamical times, their effects on global momentum and energy transfer are modest. the cr acoustic instability is likely relevant in thermal interfaces between cold and hot gas, as well as galactic winds. similar to increased opacity in radiative flows, the build-up of cr pressure due to bottlenecks can significantly increase mass outflow rates, by up to an order of magnitude. it seeds unusual forms of thermal instability, and the shocks could have distinct observational signatures, on ~kpc scales. | the cosmic-ray staircase: the outcome of the cosmic-ray acoustic instability |
context. clusters of galaxies reside at the nodes of the cosmic web, interconnected by filamentary structures that contain tenuous diffuse gas, especially in the warm-hot phase. galaxy clusters grow by mergers of smaller objects and gas that are mainly accreted through these large-scale filaments. for the first time, the large-scale cosmic structure and a long gas-emission filament have been captured by erosita on board the spectrum-roentgen-gamma mission in a direct x-ray observation of the a3391/95 field.aims: we investigate the assembly history of an a3391/95-like system of clusters and the thermo-chemical properties of the diffuse gas in it by connecting simulation predictions to the erosita observations with the aim to constrain the origin and nature of the gas in the pair-interconnecting bridge.methods: we analysed the properties of a system resembling a3391/95, extracted from the (352 h−1 cmpc)3 volume of the magneticum pathfinder cosmological simulations at z = 0.07. we tracked the main progenitors of the pair clusters and of surrounding groups back in time to study the assembly history of the system and its evolution.results: similarly to the observed a3391/95 system, the simulated cluster pair is embedded in a complex network of gas filaments, with structures aligned over more than 20 projected mpc, and the whole region collapses towards the central overdense node. the spheres of influence (3 × r200) of the two main clusters already overlap at z = 0.07, but their virial boundaries are still physically separated. the diffuse gas located in the interconnecting bridge closely reflects the warm-hot intergalactic medium, with a typical temperature of ~1 kev and an overdensity δ ~ 100 with respect to the mean baryon density of the universe, and a lower enrichment level compared to the intra-cluster medium in clusters. we find that most of the bridge gas collapsed from directions roughly orthogonal to the intra-cluster gas accretion directions, and its origin is mostly unrelated to the two cluster progenitors. we find clear signatures in the surrounding groups of infall motion towards the pair, such as significant radial velocities and a slowdown of gas compared to dark matter. these findings further support the hypothesis that the northern clump (mcxc j0621.7-5242) cluster infalls along a cosmic gas filament towards abell 3391 and might be merging with it.conclusions: we conclude that in this configuration, the pair clusters of the a3391/95-like system are in a pre-merger phase and have not yet interacted. the diffuse gas in the interconnecting bridge is mostly warm filament gas and not tidally stripped cluster gas. | the erosita view of the abell 3391/95 field: case study from the magneticum cosmological simulation |
aims: we investigate the damping of alfvén waves generated by the cosmic-ray resonant streaming instability in the context of cosmic-ray escape and propagation in the proximity of supernova remnants. we study in particular whether the self-confinement of cosmic rays in the vicinity of sources can appreciably affect the grammage.methods: we considered ion-neutral damping, turbulent damping, and nonlinear landau damping in the warm ionized and warm neutral phases of the interstellar medium. for the ion-neutral damping, the most recent damping coefficients were used.results: we show that ion-neutral damping and turbulent damping effectively limit the residence time of cosmic rays in the proximity of the source, so that the grammage that is accumulated near sources is found to be negligible. in contrast to previous results, this also occurs in the most extreme scenario in which ion-neutral damping is less effective, namely in a medium consisting only of neutral helium and fully ionized hydrogen. the standard picture, in which cosmic-ray secondaries are produced during the whole time that cosmic rays spend in the galactic disk therefore do not need to be revised substantially. | grammage of cosmic rays in the proximity of supernova remnants embedded in a partially ionized medium |
context. stellar photometric variability and instrumental effects, such as cosmic ray hits, data discontinuities, data leaks, instrument aging, and so on, lead to difficulties in the characterisation of exoplanets. therefore, they can impact the accuracy and precision of the modelling and the detectability of their transits, occultations, and phase curves.aims: this paper is aimed at improving the transit, occultation, and phase-curve modelling in the presence of strong stellar variability and instrumental noise. to this end, we invoke the wavelet formulation.methods: we explored the capabilities of the software package transit and light curve modeller (tlcm). it is able to perform (1) a joint radial-velocity and light-curve fit or (2) a light curve-only fit. it models the transit, occultation, beaming, ellipsoidal, and reflection effects in the light curves (including the gravity-darkening effect). here, the red noise, stellar variability, and instrumental effects were modelled via wavelets. the wavelet fit was constrained by prescribing that the final white noise level must be equal to the average of the uncertainties of the photometric data points. this helps to avoid overfitting and regularises the noise model. the approach was tested by injecting synthetic light curves into short-cadence kepler data and modelling them.results: the method performs well over a certain signal-to-noise (s/n) ratio. we provide limits in terms of the s/n for every studied system parameter that is needed for accurate parameter retrieval. the wavelet approach is able to manage and remove the impact of data discontinuities, cosmic ray events, and long-term stellar variability and instrument ageing, as well as short-term stellar variability, pulsation, and flares (among others).conclusions: we conclude that precise light-curve models combined with the wavelet method and with well-prescribed constraints on the white noise are able to retrieve the planetary system parameters, even in the presence of strong stellar variability and instrumental noise, including data discontinuities. | power of wavelets in analyses of transit and phase curves in the presence of stellar variability and instrumental noise. i. method and validation |
we discuss in detail the possibility that the "type-ii majoron"—that is, the pseudo-nambu-goldstone boson that arises in the context of the type-ii seesaw mechanism if the lepton number is spontaneously broken by an additional singlet scalar—account for the dark matter (dm) observed in the universe. we study the requirements the model's parameters have to fulfill in order to reproduce the measured dm relic abundance through two possible production mechanisms in the early universe, freeze-in and misalignment, both during a standard radiation-dominated era and early matter domination. we then study possible signals of type-ii majoron dm and the present and expected constraints on the parameter space that can be obtained from cosmological observations, direct detection experiments, and present and future searches for decaying dm at neutrino telescopes and cosmic-ray experiments. we find that—depending on the majoron mass, the production mechanism, and the vacuum expectation value of the type-ii triplet—all of the three decay modes (photons, electrons, neutrinos) of majoron dm particles can yield observable signals at future indirect searches for dm. furthermore, in a corner of the parameter space, detection of majoron dm is possible through electron recoil at running and future direct detection experiments. | majoron dark matter from a type ii seesaw model |
in this paper we describe revisions to the nasa space cancer risk (nscr) model focusing on updates to probability distribution functions (pdf) representing the uncertainties in the radiation quality factor (qf) model parameters and the dose and dose-rate reduction effectiveness factor (ddref). we integrate recent heavy ion data on liver, colorectal, intestinal, lung, and harderian gland tumors with other data from fission neutron experiments into the model analysis. in an earlier work we introduced distinct qfs for leukemia and solid cancer risk predictions, and here we consider liver cancer risks separately because of the higher rbe's reported in mouse experiments compared to other tumors types, and distinct risk factors for liver cancer for astronauts compared to the u.s. population. the revised model is used to make predictions of fatal cancer and circulatory disease risks for 1-year deep space and international space station (iss) missions, and a 940 day mars mission. we analyzed the contribution of the various model parameter uncertainties to the overall uncertainty, which shows that the uncertainties in relative biological effectiveness (rbe) factors at high let due to statistical uncertainties and differences across tissue types and mouse strains are the dominant uncertainty. nasa's exposure limits are approached or exceeded for each mission scenario considered. two main conclusions are made: 1) reducing the current estimate of about a 3-fold uncertainty to a 2-fold or lower uncertainty will require much more expansive animal carcinogenesis studies in order to reduce statistical uncertainties and understand tissue, sex and genetic variations. 2) alternative model assumptions such as non-targeted effects, increased tumor lethality and decreased latency at high let, and non-cancer mortality risks from circulatory diseases could significantly increase risk estimates to several times higher than the nasa limits. | predictions of space radiation fatality risk for exploration missions |
we review recent observations and modeling developments on the subject of galactic cosmic rays through the heliosphere and in the very local interstellar medium, emphasizing knowledge that has accumulated over the past decade. we begin by highlighting key measurements of cosmic-ray spectra by voyager, pamela, and ams and discuss advances in global models of solar modulation. next, we survey recent works related to large-scale, long-term spatial and temporal variations of cosmic rays in different regimes of the solar wind. then we highlight new discoveries from beyond the heliopause and link these to the short-term evolution of transients caused by solar activity. lastly, we visit new results that yield interesting insights from a broader astrophysical perspective. | galactic cosmic rays throughout the heliosphere and in the very local interstellar medium |
context. phosphorus (p) is a crucial element for life given its central role in several biomolecules. p-bearing molecules have been discovered in different regions of the milky way, but not yet towards an extragalactic environment.aims: we searched for p-bearing molecules outside the milky way towards the nearby starburst galaxy ngc 253.methods: using observations from the alma comprehensive high-resolution extragalactic molecular inventory (alchemi) project, we used the madrid data cube analysis package to model the emission of p-bearing molecules assuming local thermodynamic equilibrium (lte) conditions. we also performed a non-lte analysis using spectralradex.results: we report the detection of a p-bearing molecule, phosphorus nitride (pn), for the first time in an extragalactic environment, towards two giant molecular clouds (gmcs) of ngc 253. the lte analysis yields total pn beam-averaged column densities n = (1.20 ± 0.09) × 1013 cm−2 and n = (6.5 ± 1.6) × 1012 cm−2, which translate into abundances with respect to h2 of χ = (8.0 ± 1.0) × 10−12 and χ = (4.4 ± 1.2) × 10−12. we derived a low excitation temperature of tex = (4.4 ± 1.3) k towards the gmc with the brightest pn emission, which indicates that pn is sub-thermally excited. the non-lte analysis results in column densities consistent with the lte values. we also searched for other p-bearing molecules (po, ph3, cp, and ccp), and upper limits were derived. the derived po/pn ratios are < 1.3 and < 1.7. the abundance ratio between pn and the shock-tracer sio derived towards ngc 253 follows the same trend previously found towards galactic sources.conclusions: comparison of the observations with chemical models indicates that the derived molecular abundances of pn in ngc 253 can be explained by shock-driven chemistry followed by cosmic-ray-driven photochemistry. | first extragalactic detection of a phosphorus-bearing molecule with alchemi: phosphorus nitride (pn) |
we critically assess limits on the maximum energy of protons accelerated within superbubbles around massive stellar clusters, considering a number of different scenarios. in particular, we derive under which circumstances acceleration of protons above peta-electronvolt (pev) energies can be expected. while the external forward shock of the superbubble may account for acceleration of particles up to 100 tev, internal primary shocks such as supernova remnants expanding in the low density medium or the collective wind termination shock which forms around a young compact cluster provide more favourable channels to accelerate protons up to 1 pev, and possibly beyond. under reasonable conditions, clustered supernovae launching powerful shocks into the magnetized wind of a young and compact massive star cluster are found to be the most promising systems to accelerate protons above 10 pev. on the other hand, stochastic re-acceleration in the strongly turbulent plasma is found to be much less effective than claimed in previous works, with a maximum proton energy of at most a few hundred tev. | can superbubbles accelerate ultrahigh energy protons? |
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