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measurements of root-zone soil moisture across spatial scales of tens to thousands of meters have been a challenge for many decades. the mobile application of cosmic ray neutron sensing (crns) is a promising approach to measure field soil moisture noninvasively by surveying large regions with a ground-based vehicle. recently, concerns have been raised about a potentially biasing influence of local structures and roads. we employed neutron transport simulations and dedicated experiments to quantify the influence of different road types on the crns measurement. we found that roads introduce a substantial bias in the crns estimation of field soil moisture compared to off-road scenarios. however, this effect becomes insignificant at distances beyond a few meters from the road. neutron measurements on the road could overestimate the field value by up to 40 % depending on road material, width, and the surrounding field water content. the bias could be largely removed with an analytical correction function that accounts for these parameters. additionally, an empirical approach is proposed that can be used without prior knowledge of field soil moisture. tests at different study sites demonstrated good agreement between road-effect corrected measurements and field soil moisture observations. however, if knowledge about the road characteristics is missing, measurements on the road could substantially reduce the accuracy of this method. our results constitute a practical advancement of the mobile crns methodology, which is important for providing unbiased estimates of field-scale soil moisture to support applications in hydrology, remote sensing, and agriculture. | cosmic-ray neutron rover surveys of field soil moisture and the influence of roads |
we point out that current and planned telescopes have the potential of probing annihilating dark matter (dm) with a mass of o(100) tev and beyond. as a target for such searches, we propose models where dm annihilates into lighter mediators, themselves decaying into standard model (sm) particles. these models allow to reliably compute the energy spectra of the sm final states, and to naturally evade the unitarity bound on the dm mass. indeed, long-lived mediators may cause an early matter-dominated phase in the evolution of the universe and, upon decaying, dilute the density of preexisting relics thus allowing for very large dm masses. we compute this dilution in detail and provide results in a ready-to-use form. considering for concreteness a model of dark u(1) dm, we then study both dilution and the signals at various high energy telescopes observing γ rays, neutrinos and charged cosmic rays. this study enriches the physics case of these experiments, and opens a new observational window on heavy new physics sectors. | homeopathic dark matter, or how diluted heavy substances produce high energy cosmic rays |
the self-interacting neutrino hypothesis is well motivated for addressing the tension between the origin of sterile neutrino dark matter and indirect detection constraints. it can also result in a number of testable signals from the laboratories to the cosmos. we show that, in a broad class of models, where the sterile neutrino dark matter relic density is generated by a light neutrinophilic mediator, there must be a lower bound on the amount of extra radiation in early universe, in particular, δ neff>0.12 at the cosmic microwave background (cmb) epoch. this lower bound will be further strengthened with an improved x-ray search at the athena observatory. such an intimate relationship will be unambiguously tested by the upcoming cmb stage 4 project. | intimate relationship between sterile neutrino dark matter and δ neff |
the γ-ray emission of star-forming (sf) galaxies is attributed to hadronic interactions of cosmic ray (cr) protons with the interstellar gas and contributions from cr electrons via bremsstrahlung and inverse compton (ic) scattering. the relative importance of these processes in different galaxy types is still unclear. we model these processes in three-dimensional magnetohydrodynamical (mhd) simulations of the formation of isolated galactic discs using the moving-mesh code arepo, including dynamically coupled cr protons and adopting different cr transport models. we calculate steady-state cr spectra and also account for the emergence of secondary electrons and positrons. this allows us to produce detailed γ-ray maps, luminosities, and spectra of our simulated galaxies at different evolutionary stages. our simulations with anisotropic cr diffusion and a low cr injection efficiency at supernovae (sne; $\zeta_\mathrm{sn}=0.05$) can successfully reproduce the observed far-infrared (fir)-γ-ray relation. starburst galaxies are close to the calorimetric limit, where cr protons lose most of their energy due to hadronic interactions and hence, their γ-ray emission is dominated by neutral pion decay. however, in low sf galaxies, the increasing diffusive losses soften the cr proton spectra due to energy-dependent diffusion, and likewise steepen the pionic γ-ray spectra. in turn, ic emission hardens the total spectra and can contribute up to ~40 per cent of the total luminosity in low sf galaxies. furthermore, in order to match the observed γ-ray spectra of starburst galaxies, we require a weaker energy dependence of the cr diffusion coefficient, $d\propto e^{0.3}$, in comparison to milky way-like galaxies. | cosmic rays and non-thermal emission in simulated galaxies - ii. γ-ray maps, spectra, and the far-infrared-γ-ray relation |
the advent of new sub-millimetre (sub-mm) observational facilities has stimulated the desire to model the sub-mm line emission of galaxies within cosmological galaxy formation models. this is typically done by applying sub-resolution recipes to describe the properties of the unresolved interstellar medium (ism). while there is freedom in how one implements sub-resolution recipes, the impact of various choices has yet to be systematically explored. we combine a semi-analytic model of galaxy formation with chemical equilibrium networks and numerical radiative transfer models and explore how different choices for the sub-resolution modelling affect the predicted co, [c i], and [c ii] emission of galaxies. a key component for a successful model includes a molecular cloud mass-size relation and scaling for the ultraviolet and cosmic ray radiation field that depend on local ism properties. our most successful model adopts a plummer radial density profile for gas within molecular clouds. different assumptions for the clumping of gas within molecular clouds and changes in the molecular cloud mass distribution function hardly affect the co, [c i], and [c ii] luminosities of galaxies. at fixed star formation rate, the [c ii]-sfr ratio of galaxies scales inversely with the pressure acting on molecular clouds, increasing the molecular clouds density and hence decreasing the importance of [c ii] line cooling. we find that it is essential that a wide range of sub-mm emission lines arising in vastly different phases of the ism are used as model constraints in order to limit the freedom in sub-grid choices. | the art of modelling co, [c i], and [c ii] in cosmological galaxy formation models |
surface exposure dating using cosmic-ray-produced nuclides has been applied to determine the age of thousands of landforms produced by alpine glaciers in mountain areas worldwide. these data are potentially an extensive, easily accessible, and globally distributed paleoclimate record. in particular, exposure-dated glacier chronologies are commonly applied to study the dynamics of massive, abrupt climate changes characteristic of the transition between the last glacial maximum and the present interglacial climate. this article reviews developments in exposure dating from the perspective of whether this goal is achievable and concludes that (a) individual exposure-dated landforms cannot, in general, be associated with millennial-scale climate events at high confidence, but (b) dating uncertainties appear to be geographically and temporally unbiased, so the data set as a whole can be used to gain valuable insight into regional and global paleoclimate dynamics. future applications of exposure-age chronologies of glacier change should move away from reliance on individual dated landforms and toward synoptic analysis of the global data set. | glacier change and paleoclimate applications of cosmogenic-nuclide exposure dating |
the remnants of core-collapse supernovae (sne) have complex morphologies that may reflect asymmetries and structures developed during the progenitor sn explosion. here we investigate how the morphology of the supernova remnant cassiopeia a (cas a) reflects the characteristics of the progenitor sn with the aim of deriving the energies and masses of the post-explosion anisotropies responsible for the observed spatial distribution of fe and si/s. we model the evolution of cas a from the immediate aftermath of the progenitor sn to the three-dimensional interaction of the remnant with the surrounding medium. the post-explosion structure of the ejecta is described by small-scale clumping of material and larger-scale anisotropies. the hydrodynamic multi-species simulations consider an appropriate post-explosion isotopic composition of the ejecta. the observed average expansion rate and shock velocities can be well reproduced by models with ejecta mass m ej ≈ 4m ⊙ and explosion energy e sn ≈ 2.3 × 1051 erg. the post-explosion anisotropies (pistons) reproduce the observed distributions of fe and si/s if they had a total mass of ≈0.25 m ⊙ and a total kinetic energy of ≈1.5 × 1050 erg. the pistons produce a spatial inversion of ejecta layers at the epoch of cas a, leading to the si/s-rich ejecta physically interior to the fe-rich ejecta. the pistons are also responsible for the development of the bright rings of si/s-rich material which form at the intersection between the reverse shock and the material accumulated around the pistons during their propagation. our result supports the idea that the bulk of asymmetries observed in cas a are intrinsic to the explosion. | modeling snr cassiopeia a from the supernova explosion to its current age: the role of post-explosion anisotropies of ejecta |
the measurements of the hubble constant reveal a tension between high-redshift (cmb) and low-redshift (distance ladder) constraints. so far neither observational systematics nor new physics has been successfully implemented to explain away this tension. this paper presents a new solution to the hubble constant problem. the solution is based on the simsilun simulation (relativistic simulation of the large scale structure of the universe) with the ray-tracing algorithm implemented. the initial conditions for the simsilun simulation were set up as perturbations around the λ cdm model. however, unlike in the standard cosmological model (i.e., λ cdm model +perturbations ), within the simsilun simulation relativistic and nonlinear evolution of cosmic structures lead to the phenomenon of emerging spatial curvature, where the mean spatial curvature evolves from the spatial flatness of the early universe towards the slightly curved present-day universe. consequently, the present-day expansion rate is slightly faster compared to the spatially flat λ cdm model. the results of the ray-tracing analysis show that the universe which starts with initial conditions consistent with the planck constraints should have the hubble constant h0=72.5 ±2.1 km s-1 mpc-1 . when the simsilun simulation was rerun with no inhomogeneities imposed, the hubble constant inferred within such a homogeneous simulation was h0=68.1 ±2.0 km s-1 mpc-1 . thus, the inclusion of nonlinear relativistic evolution that leads to the emergence of the spatial curvature can explain why the low-redshift measurements favor higher values compared to the high-redshift constraints and alleviate the tension between the cmb and distance ladder measurements of the hubble constant. | emerging spatial curvature can resolve the tension between high-redshift cmb and low-redshift distance ladder measurements of the hubble constant |
the inference of physical parameters from measured distributions constitutes a core task in physics data analyses. among recent deep learning methods, so-called conditional invertible neural networks provide an elegant approach owing to their probability-preserving bijective mapping properties. they enable training the parameter-observation correspondence in one mapping direction and evaluating the parameter posterior distributions in the reverse direction. here, we study the inference of cosmic-ray source properties from cosmic-ray observations on earth using extensive astrophysical simulations. we compare the performance of conditional invertible neural networks (cinns) with the frequently used markov chain monte carlo (mcmc) method. while cinns are trained to directly predict the parameters' posterior distributions, the mcmc method extracts the posterior distributions through a likelihood function that matches simulations with observations. overall, we find good agreement between the physics parameters derived by the two different methods. as a result of its computational efficiency, the cinn method allows for a swift assessment of inference quality. | inference of cosmic-ray source properties by conditional invertible neural networks |
we show that the gravitomagnetic interaction of a kerr black hole (bh) with a surrounding magnetic field induces an electric field that accelerates charged particles to ultra-relativistic energies in the vicinity of the bh. along the bh rotation axis, these electrons/protons can reach energies of even thousands of petaelectronvolts, so stellar-mass bhs in long gamma-ray bursts (grbs) and supermassive bhs in active galactic nuclei can contribute to the ultrahigh-energy cosmic rays thorough this mechanism. at off-axis latitudes, the particles accelerate to energies of hundreds of gigaelectronvolts and emit synchrotron radiation at gigaelectronvolt energies. this process occurs within 60° around the bh rotation axis, and due to the equatorial symmetry, it forms a double-cone emission. we outline the theoretical framework describing these acceleration and radiation processes, how they extract the rotational energy of the kerr bh and the consequences for the astrophysics of grbs. | gravitomagnetic interaction of a kerr black hole with a magnetic field as the source of the jetted gev radiation of gamma-ray bursts |
the tibet asγ experiment just reported their measurement of sub-pev diffuse gamma-ray emission from the galactic disk, with the highest energy up to 957 tev. these diffuse gamma rays are most likely the hadronic origin by cosmic ray (cr) interaction with interstellar gas in the galaxy. this measurement provides direct evidence to the hypothesis that the galactic cosmic rays (gcrs) can be accelerated beyond pev energies. in this work, we try to explain the sub-pev diffuse gamma-ray spectrum with different cr propagation models. we find that there is a tension between the sub-pev diffuse gamma-ray and the local cr spectrum. to describe the sub-pev diffuse gamma-ray flux, it generally requires larger local cr flux than measurement in the knee region. we further calculate the pev neutrino flux from the cr propagation model. even all of these sub-pev diffuse gamma rays originate from the propagation, the galactic neutrinos (gns) only account for less than ∼ 15% of observed flux, most of which are still from extragalactic sources. | galactic cosmic ray propagation: sub-pev diffuse gamma-ray and neutrino emission |
owing to the complexity of turbulent magnetic fields, modelling the diffusion of cosmic rays is challenging. based on the current understanding of anisotropic magnetohydrodynamic (mhd) turbulence, we use test particles to examine the cosmic rays' superdiffusion in the direction perpendicular to the mean magnetic field. by changing alfvén mach number ma and sonic mach number ms of compressible mhd simulations, our study covers a wide range of astrophysical conditions including subsonic warm gas phase and supersonic cold molecular gas. we show that freely streaming cosmic rays' perpendicular displacement increases as 3/2 to the power of the time travelled along local magnetic field lines. this power-law index changes to 3/4 if the parallel propagation is diffusive. we find that the cosmic rays' parallel mean free path decreases in a power-law relation of $m_\mathrm{ a}^{-2}$ in supersonic turbulence. we investigate the energy fraction of slow, fast, and alfvénic modes and confirm the dominance of alfvénic modes in the perpendicular superdiffusion. in particular, the energy fraction of fast mode, which is the main agent for pitch-angle scattering, increases with ma, but is insensitive to ms ≥ 2. accordingly, our results suggest that the suppressed diffusion in supersonic molecular clouds arises primarily due to the variations of ma instead of ms. | superdiffusion of cosmic rays in compressible magnetized turbulence |
cosmic rays (crs) are an important component in the interstellar medium, but their effect on the dynamics of the disc-halo interface (<10 kpc from the disc) is still unclear. we study the influence of crs on the gas above the disc with high-resolution fire-2 cosmological simulations of late-type l⋆ galaxies at redshift z ~ 0. we compare runs with and without cr feedback (with constant anisotropic diffusion κ∥ ~ 3 × 1029 cm2 s-1 and streaming). our simulations capture the relevant disc-halo interactions, including outflows, inflows, and galactic fountains. extra-planar gas in all of the runs satisfies dynamical balance, where total pressure balances the weight of the overlying gas. while the kinetic pressure from non-uniform motion (≳1 kpc scale) dominates in the mid-plane, thermal and bulk pressures (or cr pressure if included) take over at large heights. we find that with cr feedback, (1) the warm (~104 k) gas is slowly accelerated by crs; (2) the hot (>5 × 105 k) gas scale height is suppressed; (3) the warm-hot (2 × 104-5 × 105 k) medium becomes the most volume-filling phase in the disc-halo interface. we develop a novel conceptual model of the near-disc gas dynamics in low-redshift l⋆ galaxies: with crs, the disc-halo interface is filled with cr-driven warm winds and hot superbubbles that are propagating into the circumgalactic medium with a small fraction falling back to the disc. without crs, most outflows from hot superbubbles are trapped by the existing hot halo and gravity, so typically they form galactic fountains. | the impact of cosmic rays on dynamical balance and disc-halo interaction in l⋆ disc galaxies |
cosmic rays (crs) are thought to play an important role in galaxy evolution. we study their effect when coupled to other important sources of feedback, namely supernovae (sne) and stellar radiation, by including cr anisotropic diffusion and radiative losses but neglecting cr streaming. using the ramses-rt code, we perform the first radiation-magnetohydrodynamics simulations of isolated disc galaxies with and without crs. we study galaxies embedded in dark matter haloes of 1010, 1011, and $10^{12}\, \rm m_{\odot }$ with a maximum resolution of $9 \, \rm pc$. we find that crs reduce the star formation (sf) rate in our two dwarf galaxies by a factor of 2, with decreasing efficiency with increasing galaxy mass. they increase significantly the outflow mass loading factor in all our galaxies and make the outflows colder. we study the impact of the cr diffusion coefficient, exploring values from κ = 1027 to $\rm 3\times 10^{29}\, cm^2\, s^{-1}$. with a lower κ, crs remain confined for longer on small scales and are consequently efficient in suppressing sf, whereas a higher diffusion coefficient reduces the effect on sf and increases the generation of cold outflows. finally, we compare cr feedback to a calibrated 'strong' sn feedback model known to sufficiently regulate sf in high-redshift cosmological simulations. we find that cr feedback is not sufficiently strong to replace this strong sn feedback. as they tend to smooth out the ism and fill it with denser gas, crs also lower the escape fraction of lyman continuum photons from galaxies. | radiation-magnetohydrodynamics simulations of cosmic ray feedback in disc galaxies |
the first electromagnetic signal observed in different types of cosmic explosions is released upon emergence of a shock created in the explosion from the opaque envelope enshrouding the central source. notable examples are the early emission from various types of supernovae and low luminosity grbs, the prompt photospheric emission in long grbs, and the gamma-ray emission that accompanied the gravitational wave signal in neutron star mergers. in all of these examples, the shock driven by the explosion is mediated by the radiation trapped inside it, and its velocity and structure, that depend on environmental conditions, dictate the characteristics of the observed electromagnetic emission at early times, and potentially also their neutrino emission. much efforts have been devoted in recent years to develop a detailed theory of radiation mediated shocks in an attempt to predict the properties of the early emission in the aforementioned systems. these efforts are timely in view of the anticipated detection rate of shock breakout candidates by upcoming transient factories, and the potential detection of a gamma-ray flash from shock breakout in neutron star mergers like gw170817. this review aims at providing a comprehensive overview of the theory and applications of radiation mediated shocks, starting from basic principles. the classification of shock solutions, which are governed by the conditions prevailing in each class of objects, and the methods used to solve the shock equations in different regimes will be described, with particular emphasis on the observational diagnostics. the applications to supernovae, low-luminosity grbs, long grbs, neutron star mergers, and neutrino emission will be highlighted. | physics of radiation mediated shocks and its applications to grbs, supernovae, and neutron star mergers |
we compute the production of cosmic rays (crs) in the dynamical superbubble (sb) produced by a cluster of massive stars. stellar winds, supernova remnants, and turbulence are found to accelerate particles so efficiently that the non-linear feedback of the particles must be taken into account in order to ensure that the energy balance is not violated. high-energy particles do not scatter efficiently on the turbulence and escape quickly after each supernova explosion, which makes both their intensity inside the bubble and injection in the interstellar medium intermittent. on the other hand, the stochastic acceleration of low-energy particles hardens the spectra at gev energies. because crs damp the turbulence cascade, this hardening is less pronounced when non-linearities are taken into account. nevertheless, spectra with hard components extending up to 1-10 gev and normalized to an energy density of 1-100 ev cm-3 are found to be typical signatures of crs produced in sbs. efficient shock reacceleration within compact clusters is further shown to produce hard, slightly concave spectra, while the presence of a magnetized shell is shown to enhance the confinement of crs in the bubble and therefore the collective plasma effects acting on them. we eventually estimate the overall contribution of sbs to the galactic cr content and show typical gamma-ray spectra expected from hadronic interactions in sb shells. in both cases, a qualitative agreement with observations is obtained. | cosmic ray production in superbubbles |
the enhanced star-forming activity, typical of starburst galaxies, powers strong galactic winds expanding on kiloparsec (kpc) scales and characterized by bubble structures. here we discuss the possibility that particle acceleration may take place at the termination shock of such winds. we calculate the spectrum of accelerated particles and their maximum energy, which turns out to range up to a few hundred petaelectronvolt (pev) for typical values of the parameters. cosmic rays accelerated at the termination shock are advected towards the edge of the bubble excavated by the wind and eventually escape into extragalactic space. we also calculate the flux of gamma-rays and neutrinos produced by hadronic interactions in the bubble, as well as the diffuse flux resulting from the superposition of the contribution of starburst galaxies on cosmological scales. finally, we compute the diffuse flux of cosmic rays from starburst bubbles and compare it with existing data. | particle acceleration and multimessenger emission from starburst-driven galactic winds |
in this study, we document deglaciation in a sector of the southern-central pyrenees (the panticosa massif and the upper gállego and ossau valleys) using cosmic-ray exposure (cre) dating methods, which were applied to samples from high altitude polished rock steps and rock glacier boulders. the obtained cre dates show a coherent spatial distribution and confirm results previously obtained in this study area, thus demonstrating the reliability and robustness of the method. the results of analyses based on two distinct isotopes (10be and 36cl) are consistent, although the error is higher for results based on the 36cl isotope. the study provides evidence for ice extent in the high gállego valley during the oldest dryas, with glacial advance until the bottom of the valleys, although the main glacier tongues remained disconnected from each other. during this period, the extent of glacier advance was directly related to the elevation of the associated summits. the younger dryas glaciers were constrained to cirques or very short ice tongues, and dating of the polished rock steps indicates that the ice masses were present until the first millennium of the holocene. the brazato rock glacier developed at the beginning of the holocene and remained active until the holocene thermal optimum, because of the protective effect of large masses of blocks and boulders. | deglaciation in the central pyrenees during the pleistocene-holocene transition: timing and geomorphological significance |
this review describes the development of the physics of hadronic cross sections up to recent lhc results and cosmic ray experiments. we present here a comprehensive review - written with a historical perspective - about total cross sections from medium to the highest energies explored experimentally and studied through a variety of methods and theoretical models for over 60 years. we begin by recalling the analytic properties of the elastic amplitude and the theorems about the asymptotic behavior of the total cross section. a discussion of how proton-proton cross sections are extracted from cosmic rays at higher than accelerator energies and help the study of these asymptotic limits, is presented. this is followed by a description of the advent of particle colliders, through which high energies and unmatched experimental precisions have been attained. thus the measured hadronic elastic and total cross sections have become crucial instruments to probe the so called soft part of qcd physics, where quarks and gluons are confined, and have led to test and refine regge behavior and a number of diffractive models. as the c.m. energy increases, the total cross section also probes the transition into hard scattering describable with perturbative qcd, the so-called mini-jet region. further tests are provided by cross section measurements of γ p, γ ^* p and γ ^* γ ^* for models based on vector meson dominance, scaling limits of virtual photons at high q^2 and the bfkl formalism. models interpolating from virtual to real photons are also tested. | introduction to the physics of the total cross section at lhc. a review of data and models |
context. galactic cosmic rays are particles presumably accelerated in supernova remnant shocks that propagate in the interstellar medium up to the densest parts of molecular clouds, losing energy and their ionisation efficiency because of the presence of magnetic fields and collisions with molecular hydrogen. recent observations hint at high levels of ionisation and at the presence of synchrotron emission in protostellar systems, which leads to an apparent contradiction.aims: we want to explain the origin of these cosmic rays accelerated within young protostars as suggested by observations.methods: our modelling consists of a set of conditions that has to be satisfied in order to have an efficient cosmic-ray acceleration through diffusive shock acceleration. we analyse three main acceleration sites (shocks in accretion flows, along the jets, and on protostellar surfaces), then we follow the propagation of these particles through the protostellar system up to the hot spot region.results: we find that jet shocks can be strong accelerators of cosmic-ray protons, which can be boosted up to relativistic energies. other promising acceleration sites are protostellar surfaces, where shocks caused by impacting material during the collapse phase are strong enough to accelerate cosmic-ray protons. in contrast, accretion flow shocks are too weak to efficiently accelerate cosmic rays. though cosmic-ray electrons are weakly accelerated, they can gain a strong boost to relativistic energies through re-acceleration in successive shocks.conclusions: we suggest a mechanism able to accelerate both cosmic-ray protons and electrons through the diffusive shock acceleration mechanism, which can be used to explain the high ionisation rate and the synchrotron emission observed towards protostellar sources. the existence of an internal source of energetic particles can have a strong and unforeseen impact on the ionisation of the protostellar disc, on the star and planet formation processes, and on the formation of pre-biotic molecules. | protostars: forges of cosmic rays? |
we test the assumption of hydrostatic equilibrium in an x-ray luminosity selected sample of 50 galaxy clusters at 0.15 < z < 0.3 from the local cluster substructure survey (locuss). our weak-lensing measurements of m500 control systematic biases to sub-4 per cent, and our hydrostatic measurements of the same achieve excellent agreement between xmm-newton and chandra. the mean ratio of x-ray to lensing mass for these 50 clusters is β_x= 0.95± 0.05, and for the 44 clusters also detected by planck, the mean ratio of planck mass estimate to locuss lensing mass is β_p= 0.95± 0.04. based on a careful like-for-like analysis, we find that locuss, the canadian cluster comparison project, and weighing the giants agree on β_p ≃ 0.9-0.95 at 0.15 < z < 0.3. this small level of hydrostatic bias disagrees at ∼5σ with the level required to reconcile planck cosmology results from the cosmic microwave background and galaxy cluster counts. | locuss: testing hydrostatic equilibrium in galaxy clusters |
cosmic-ray antideuterium and antihelium have long been suggested as probes of dark matter, as their secondary astrophysical production was thought extremely scarce. but how does one actually predict the secondary flux? antinuclei are dominantly produced in p p collisions, where laboratory cross section data are lacking. we make a new attempt at tackling this problem by appealing to a scaling law of nuclear coalescence with the physical volume of the hadronic emission region. the same volume is probed by hanbury brown-twiss (hbt) two-particle correlations. we demonstrate the consistency of the scaling law with systems ranging from central and off-axis a a collisions to p a collisions, spanning 3 orders of magnitude in coalescence yield. extending the volume scaling to the p p system, hbt data allow us to make a new estimate of coalescence that we test against preliminary alice p p data. for antihelium the resulting cross section is 1 or 2 orders of magnitude higher than most earlier estimates. the astrophysical secondary flux of antihelium could be within reach of a five-year exposure of ams02. | cosmic rays, antihelium, and an old navy spotlight |
if the unidentified emission line at ~3.55 kev previously found in spectra of nearby galaxies and galaxy clusters is due to radiatively decaying dark matter, one should detect the signal of comparable strength from many cosmic objects of different nature. by studying existing dark matter distributions in galaxy clusters we identified top-19 of them observed by xmm-newton x-ray cosmic mission, and analyzed the data for the presence of the new line. in 8 of them, we identified > 2 sigma positive line-like residuals with average position 3.52 +/- 0.08 kev in the emitter's frame. their observed properties are unlikely to be explained by statistical fluctuations or astrophysical emission lines; observed line position in m31 and galactic center makes an additional argument against general-type systematics. being interpreted as decaying dark matter line, the new detections correspond to radiative decay lifetime tau_dm ~ (3.5-6) x 10^27 s consistent with previous detections. | testing the origin of ~3.55 kev line in individual galaxy clusters observed with xmm-newton |
we present the first part of the observations made for the continuum halos in nearby galaxies, an evla survey (chang-es) project. the aim of the chang-es project is to study and characterize the nature of radio halos, their prevalence as well as their magnetic fields, and the cosmic rays illuminating these fields. this paper reports observations with the compact d configuration of the karl g. jansky very large array (vla) for the sample of 35 nearby edge-on galaxies of chang-es. with the new wide bandwidth capabilities of the vla, an unprecedented sensitivity was achieved for all polarization products. the beam resolution is an average of 9.″6 and 36″ with noise levels reaching approximately 6 and 30 μjy beam-1 for c- and l-bands, respectively (robust weighting). we present intensity maps in these two frequency bands (c and l), with different weightings, as well as spectral index maps, polarization maps, and new measurements of star formation rates (sfrs). the data products described herein are available to the public in the chang-es data release available at http://www.queensu.ca/changes. we also present evidence of a trend among galaxies with larger halos having higher sfr surface density, and we show, for the first time, a radio continuum image of the median galaxy, taking advantage of the collective signal-to-noise ratio of 30 of our galaxies. this image shows clearly that a “typical” spiral galaxy is surrounded by a halo of magnetic fields and cosmic rays. | chang-es. iv. radio continuum emission of 35 edge-on galaxies observed with the karl g. jansky very large array in d configuration—data release 1 |
we present the detection of multiple carbon monoxide co line transitions with alma in a few tens of infrared-selected galaxies on and above the main sequence at z = 1.1-1.7. we reliably detected the emission of co (5 - 4), co (2 - 1), and co (7 - 6)+[c i](3p2 - 3p1) in 50, 33, and 13 galaxies, respectively, and we complemented this information with available co (4 - 3) and [c i](3p1 - 3p0) fluxes for part of the sample, and by modeling of the optical-to-millimeter spectral energy distribution. we retrieve a quasi-linear relation between lir and co (5 - 4) or co (7 - 6) for main-sequence galaxies and starbursts, corroborating the hypothesis that these transitions can be used as star formation rate (sfr) tracers. we find the co excitation to steadily increase as a function of the star formation efficiency, the mean intensity of the radiation field warming the dust (⟨u⟩), the surface density of sfr (σsfr), and, less distinctly, with the distance from the main sequence (δms). this adds to the tentative evidence for higher excitation of the co+[c i] spectral line energy distribution (sled) of starburst galaxies relative to that for main-sequence objects, where the dust opacities play a minor role in shaping the high-j co transitions in our sample. however, the distinction between the average sled of upper main-sequence and starburst galaxies is blurred, driven by a wide variety of intrinsic shapes. large velocity gradient radiative transfer modeling demonstrates the existence of a highly excited component that elevates the co sled of high-redshift main-sequence and starbursting galaxies above the typical values observed in the disk of the milky way. this excited component is dense and it encloses ∼50% of the total molecular gas mass in main-sequence objects. we interpret the observed trends involving the co excitation as to be mainly determined by a combination of large sfrs and compact sizes, as a large σsfr is naturally connected with enhanced dense molecular gas fractions and higher dust and gas temperatures, due to increasing ultraviolet radiation fields, cosmic ray rates, as well as dust and gas coupling. we release the full data compilation and the ancillary information to the community. the data compilation described in table d.1 is 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/641/a155 | co emission in distant galaxies on and above the main sequence |
the existence of a "knee" at energy ∼1 pev in the cosmic-ray spectrum suggests the presence of galactic pev proton accelerators called "pevatrons." supernova remnant (snr) g 106.3 +2.7 is a prime candidate for one of these. the recent detection of very high energy (0.1-100 tev) gamma rays from g 106.3 +2.7 may be explained either by the decay of neutral pions or inverse compton scattering by relativistic electrons. we report an analysis of 12 years of fermi-lat gamma-ray data that shows that the gev-tev gamma-ray spectrum is much harder and requires a different total electron energy than the radio and x-ray spectra, suggesting it has a distinct, hadronic origin. the nondetection of gamma rays below 10 gev implies additional constraints on the relativistic electron spectrum. a hadronic interpretation of the observed gamma rays is strongly supported. this observation confirms the long-sought connection between galactic pevatrons and snrs. moreover, it suggests that g 106.3 +2.7 could be the brightest member of a new population of snrs whose gamma-ray energy flux peaks at tev energies. such a population may contribute to the cosmic-ray knee and be revealed by future very high energy gamma-ray detectors. | evidence for pev proton acceleration from fermi-lat observations of snr g 106.3 +2.7 |
very recently, the fermi-lab reported the new experimental combined results on the magnetic momentum of muon with a 4.2σ discrepancy compared with the expectation of the standard model [1]. a new light gauge boson x in the lμ - lτ model provides a good explanation for the g - 2 anomaly. a dirac fermion dark matter with a large lμ - lτ charge can explain both the g - 2 anomaly and the dark matter relic density [2]. in this work, we focus on the case that the mass of the dark matter is larger than the mass of muon (i.e. m ψ > m μ) for which the channel ψψ ⟶ μ - μ + opens. although the cross section (σ v) μ - μ +is smaller by a factor of 1/q ψ 2 (q ψ represents the lμ - lτ charge of the dark matter) compared with the channel ψψ ⟶ x x ⟶ ννν̅ν̅, the resulting secondary electrons and positrons could imprint on their spectra above gev energies due to the reacceleration effect of cosmic ray propagation. we use the ams-02 measurements of electrons and positrons to constrain the annihilation cross section of the channel ψψ ⟶ μ - μ +, which rules out part of the parameter space of the large lμ - lτ charged dark matter model to account for the muon g - 2 anomaly. | constraining u(1) lμ- lτcharged dark matter model for muon g - 2 anomaly with ams-02 electron and positron data |
context. young massive stellar clusters are extreme environments and potentially provide the means for efficient particle acceleration. indeed, they are increasingly considered as being responsible for a significant fraction of cosmic rays (crs) that are accelerated within the milky way. westerlund 1, the most massive known young stellar cluster in our galaxy, is a prime candidate for studying this hypothesis. while the very-high-energy γ-ray source hess j1646−458 has been detected in the vicinity of westerlund 1 in the past, its association could not be firmly identified.aims: we aim to identify the physical processes responsible for the γ-ray emission around westerlund 1 and thus to understand the role of massive stellar clusters in the acceleration of galactic crs better.methods: using 164 h of data recorded with the high energy stereoscopic system (h.e.s.s.), we carried out a deep spectromorphological study of the γ-ray emission of hess j1646−458. we furthermore employed h i and co observations of the region to infer the presence of gas that could serve as target material for interactions of accelerated crs.results: we detected large-scale (∼2° diameter) γ-ray emission with a complex morphology, exhibiting a shell-like structure and showing no significant variation with γ-ray energy. the combined energy spectrum of the emission extends to several tens of tev, and it is uniform across the entire source region. we did not find a clear correlation of the γ-ray emission with gas clouds as identified through h i and co observations.conclusions: we conclude that, of the known objects within the region, only westerlund 1 can explain the majority of the γ-ray emission. several cr acceleration sites and mechanisms are conceivable and discussed in detail. while it seems clear that westerlund 1 acts as a powerful particle accelerator, no firm conclusions on the contribution of massive stellar clusters to the flux of galactic crs in general can be drawn at this point. | a deep spectromorphological study of the γ-ray emission surrounding the young massive stellar cluster westerlund 1 |
we revisit the signatures from collisions of cosmic rays on sub-gev dark matter (dm) in the milky way. in addition to the upscattered dm component that can be probed by existing dm and neutrino experiments widely discussed, we examine the associated signals in γ rays and neutrinos that span a wide energy range due to the inelastic scatterings. assuming a simple vector portal dm model for illustration, we compute both the upscattered dm flux by cosmic-ray protons and the resulting emission of secondary γ rays and high-energy neutrinos from proton excitation, hadronization, and the subsequent meson decay. we derive limits on coupling constants in the vector portal model using data from the γ -ray and high-energy neutrino telescopes including fermi, h.e.s.s., and icecube. these limits are compared to those obtained by considering the upscattered dm signals at the low-energy dm (neutrino) detectors xenon1t (miniboone) and icecube. for this particular model, the limits are set predominantly by nondetection of the upscattered dm events in xenon1t, for most of the dm mass range due to the large scattering cross section at low energies. nevertheless, our study demonstrates that the γ -ray and neutrino signals, traditionally considered as indirect probes for dm annihilation and decay, can also be directly used to constrain the dm-nucleon interaction in complementary to the direct search experiments. | elastic and inelastic scattering of cosmic rays on sub-gev dark matter |
pedotransfer functions are used to relate gridded databases of soil texture information to the soil hydraulic and thermal parameters of land surface models. the parameters within these pedotransfer functions are uncertain and calibrated through analyses of point soil samples. how these calibrations relate to the soil parameters at the spatial scale of modern land surface models is unclear because gridded databases of soil texture represent an area average. we present a novel approach for calibrating such pedotransfer functions to improve land surface model soil moisture prediction by using observations from the soil moisture active passive (smap) satellite mission within a data assimilation framework. unlike traditional calibration procedures, data assimilation always takes into account the relative uncertainties given to both model and observed estimates to find a maximum likelihood estimate. after performing the calibration procedure, we find improved estimates of soil moisture and heat flux for the joint uk land environment simulator (jules) land surface model (run at a 1 km resolution) when compared to estimates from a cosmic-ray soil moisture monitoring network (cosmos-uk) and three flux tower sites. the spatial resolution of the cosmos probes is much more representative of the 1 km model grid than traditional point-based soil moisture sensors. for 11 cosmic-ray neutron soil moisture probes located across the modelled domain, we find an average 22 % reduction in root mean squared error, a 16 % reduction in unbiased root mean squared error and a 16 % increase in correlation after using data assimilation techniques to retrieve new pedotransfer function parameters. | improving soil moisture prediction of a high-resolution land surface model by parameterising pedotransfer functions through assimilation of smap satellite data |
here we use newly available methods to examine the dynamical association between cosmic rays (cr) and global temperature (gt) in the 20th-century observational record. we find no measurable evidence of a causal effect linking cr to the overall 20th-century warming trend; however, on short interannual timescales, we find a significant, although modest, causal effect of cr on short-term, year-to-year variability in gt. thus, although cr clearly do not contribute measurably to the 20th-century global warming trend, they do appear as a nontraditional forcing in the climate system on short interannual timescales, providing another interesting piece of the puzzle in our understanding of factors influencing climate variability. | dynamical evidence for causality between galactic cosmic rays and interannual variation in global temperature |
about one-third of x-ray-luminous clusters show smooth, mpc-scale radio emission, known as giant radio haloes. one promising model for radio haloes is fermi-ii acceleration of seed relativistic electrons by compressible turbulence. the origin of these seed electrons has never been fully explored. here, we integrate the fokker-planck equation of the cosmic ray (cr) electron and proton distributions when post-processing cosmological simulations of cluster formation and confront them with radio surface brightness and spectral data of coma. for standard assumptions, structure formation shocks lead to a seed electron population that produces too centrally concentrated radio emission. matching observations requires modifying properties of the cr population (rapid streaming; enhanced cr electron acceleration at shocks) or turbulence (increasing turbulent-to-thermal energy density with radius), but at the expense of fine-tuning. in a parameter study, we find that radio properties are exponentially sensitive to the amplitude of turbulence, which is inconsistent with small scatter in scaling relations. this sensitivity is removed if we relate the acceleration time to the turbulent dissipation time. in this case, turbulence above a threshold value provides a fixed amount of amplification; observations could thus potentially constrain the unknown cr seed population. to obtain sufficient acceleration, the turbulent magneto-hydrodynamics cascade has to terminate by transit time damping on crs, i.e. thermal particles must be scattered by plasma instabilities. understanding the small scatter in radio halo scaling relations may provide a rich source of insight on plasma processes in clusters. | turbulence and particle acceleration in giant radio haloes: the origin of seed electrons |
inspired by the peak structure observed by recent dampe experiment in e^+e^- cosmic-ray spectrum, we consider a scalar dark matter (dm) model with gauged u(1)_{l_e-l_μ } symmetry, which is the most economical anomaly-free theory to potentially explain the peak by dm annihilation in nearby subhalo. we utilize the process χ χ → z^' z^' → l \bar{l} l^' \bar{l}^' , where χ , z^' , l^{(' )} denote the scalar dm, the new gauge boson and l^{(' )} =e, μ , respectively, to generate the e^+e^- spectrum. by fitting the predicted spectrum to the experimental data, we obtain the favored dm mass range m_χ ∼eq 3060^{+80}_{-100} gev and δ m ≡ m_χ - m_{z^' } ≲ 14 gev at 68% confidence level (c.l.). furthermore, we determine the parameter space of the model which can explain the peak and meanwhile satisfy the constraints from dm relic abundance, dm direct detection and the collider bounds. we conclude that the model we consider can account for the peak, although there exists a tension with the constraints from the lep-ii bound on m_{z^' } arising from the cross section measurement of e^+e^- → z^' *} → e^+ e^-. | explaining the dampe data with scalar dark matter and gauged u(1)_{l_e-l_μ } interaction |
ever since the discovery of cosmic rays (crs), significant advancements have been made in modelling their propagation in the galaxy and in the heliosphere. however, propagation models suffer from degeneracy of many parameters. to complicate the picture, the precision of recent data have started challenging existing models. to tackle these issues, we use available multifrequency observations of the interstellar emission from radio to gamma rays, together with direct cr measurements, to study local interstellar spectra (lis) and propagation models. as a result, the electron lis is characterized without any assumption on solar modulation, and favourite propagation models are put forwards. more precisely, our analysis leads to the following main conclusions: (1) the electron injection spectrum needs at least a break below a few gev; (2) even though consistent with direct cr measurements, propagation models producing a lis with large all-electron density from a few hundreds of mev to a few gev are disfavoured by both radio and gamma-ray observations; (3) the usual assumption that direct cr measurements, after accounting for solar modulation, are representative of the proton lis in our ∼1 kpc region is challenged by the observed local gamma-ray h i emissivity. we provide the resulting proton lis, all-electron lis, and propagation parameters based on synchrotron, gamma-ray, and direct cr data. a plain diffusion model and a tentative diffusive-reacceleration model are put forwards. the various models are investigated in the inner-galaxy region in x-rays and gamma rays. predictions of the interstellar emission for future gamma-ray instruments (e-astrogam and amego) are derived. | imprints of cosmic rays in multifrequency observations of the interstellar emission |
a large effort has been carried out to characterize the background of sodium iodide crystals within the annual modulation with nai scintillators (anais) project. in this paper, the background models developed for three 12.5 kg nai(tl) scintillators produced by alpha spectra inc. and operated at the canfranc underground laboratory are presented together with an evaluation of the background prospects for the full experiment. measured spectra from threshold to high energy in different conditions are well described by the models based on quantified activities. at the region of interest, crystal bulk contamination is the dominant background source. contributions from ^{210}pb, ^{40}k, ^{22}na and 3h are the most relevant. those from ^{40}k and ^{22}na could be efficiently suppressed thanks to anticoincidence operation in a crystals matrix or inside a liquid scintillator veto (lsv), while that from ^{210}pb has been reduced by improving crystal production methods and 3h production could be reduced by shielding against cosmic rays during production. assuming the activities of the last characterized detector, for nine crystals with a total mass of 112.5 kg the expected background rate is 2.5 counts/(kev kg day) in the region from 1 to 4 kev, which could be reduced at 1.4 counts/(kev kg day) by using a lsv. | assessment of backgrounds of the anais experiment for dark matter direct detection |
we investigate the feasibility of the indirect detection of dark matter in a simple model using the neutrino portal. the model is very economical, with right-handed neutrinos generating neutrino masses through the type-i seesaw mechanism and simultaneously mediating interactions with dark matter. given the small neutrino yukawa couplings expected in a type-i seesaw, direct detection and accelerator probes of dark matter in this scenario are challenging. however, dark matter can efficiently annihilate to right-handed neutrinos, which then decay via active-sterile mixing through the weak interactions, leading to a variety of indirect astronomical signatures. we derive the existing constraints on this scenario from planck cosmic microwave background measurements, fermi dwarf spheroidal galaxy and galactic center gamma-ray observations, and ams-02 antiproton observations, and we also discuss the future prospects of fermi and the cherenkov telescope array. thermal annihilation rates are already being probed for dark matter lighter than about 50 gev, and this can be extended to dark matter masses of 100 gev and beyond in the future. this scenario can also provide a dark matter interpretation of the fermi galactic center gamma-ray excess, and we confront this interpretation with other indirect constraints. finally we discuss some of the exciting implications of extensions of the minimal model with large neutrino yukawa couplings and higgs portal couplings. | indirect detection of neutrino portal dark matter |
lhaaso is expected to be the most sensitive project to face the open problems in galactic cosmic ray physics through a combined study of photon- and charged particle-induced extensive air showers in the energy range 1011 - 1018 ev. this new generation multi-component experiment will be able of continuously surveying the tev sky for steady and transient sources from 100 gev to 1 pev, thus opening for the first time the pev range to the direct observations of the high energy cosmic ray sources. in addition, the different observables (electronic, muonic and cherenkov/fluorescence components) that will be measured in lhaaso will allow to investigate origin, acceleration and propagation of the radiation through a measurement of energy spectrum, elemental composition and anisotropy with unprecedented resolution. the installation of experiment started at very high altitude in china (daocheng site, sichuan province, 4410 m a.s.l.). the commissioning of the first quarter of the layout is expected in 2018. the conclusion of installation in 2021. | the lhaaso experiment: from gamma-ray astronomy to cosmic rays |
we test the hypothesis of starburst galaxies as sources of ultrahigh energy cosmic rays and high energy neutrinos. the computation of interactions of ultrahigh energy cosmic rays in the starburst environment as well as in the propagation to earth is made using a modified version of the monte carlo code simprop, where hadronic processes in the environment of sources are implemented for the first time. taking into account a star-formation-rate distribution of sources, the fluxes of ultrahigh energy cosmic rays and high energy neutrinos are computed and compared with observations, and the explored parameter space for the source characteristics is discussed. we find that, depending on the density of the gas in the source environment, spallation reactions could exceed the outcome in neutrinos from photohadronic interactions in the source environment and in the extragalactic space. | testing hadronic and photohadronic interactions as responsible for ultrahigh energy cosmic rays and neutrino fluxes from starburst galaxies |
as the first dark matter objects gravitationally condense, a density cusp forms immediately at every initial density maximum. numerical simulations and theoretical arguments suggest that these prompt cusps can survive until the present day. we show that if dark matter is a thermally produced weakly interacting massive particle, many thousands of prompt cusps with individual masses similar to that of the earth may be present in every solar mass of dark matter. this radically alters predictions for the amount and spatial distribution of dark matter annihilation radiation. the annihilation rate is boosted by at least an order of magnitude compared to previous predictions, both in the cosmological average and within galaxy-scale halos. moreover, the signal is predominantly boosted outside of the centers of galactic halos, so alternative targets become significantly more attractive for indirect-detection searches. for example, prompt cusps present new opportunities to test the dark matter interpretation of the galactic center γ-ray excess by searching for similar spectral signatures in the isotropic γ-ray background and large-scale cosmic structure. | prompt cusps and the dark matter annihilation signal |
the observation of the diffuse galactic gamma-ray flux is the most powerful tool to study cosmic rays in different regions of the galaxy, because the energy and angular distributions of the photons encode information about the density and spectral shape of relativistic particles in the entire milky way. an open problem of fundamental importance is whether cosmic rays in distant regions of the milky way have the same spectral shape observed at the earth or not. if the spectral shape of protons and nuclei is equal in all the galaxy, the dominant, hadronic component of the diffuse gamma-ray flux must have an angular distribution that, after correcting for absorption effects, is energy independent. to study experimentally the validity of this factorization of the energy and angular dependence of the diffuse flux it is necessary to compare observations in a very broad energy range. the extension of the observations to energies eγ≃0.1 - 10 pev is of great interest, because it allows the study of the cosmic ray spectra around the feature known as the "knee." the absorption probability for photons in this energy range is not negligible, and distorts the energy and angular distributions of the diffuse flux, therefore a precise calculation of the absorption effects is necessary for the interpretation of the data. in this work we present predictions of the diffuse gamma-ray flux at very high energy, constructed under different hypothesis for the space dependence of the cosmic ray energy spectra, and discuss the potential of the observations for present and future detectors. | diffuse galactic gamma-ray flux at very high energy |
observational studies reveal that complex organic molecules (coms) can be found in various objects associated with different star formation stages. the identification of coms in prestellar cores, i.e., cold environments in which thermally induced chemistry can be excluded and radiolysis is limited by cosmic rays and cosmic-ray-induced uv photons, is particularly important as this stage sets up the initial chemical composition from which ultimately stars and planets evolve. recent laboratory results demonstrate that molecules as complex as glycolaldehyde and ethylene glycol are efficiently formed on icy dust grains via nonenergetic atom addition reactions between accreting h atoms and co molecules, a process that dominates surface chemistry during the “co freeze-out stage” in dense cores. in the present study we demonstrate that a similar mechanism results in the formation of the biologically relevant molecule glycerol—hoch2ch(oh)ch2oh—a three-carbon-bearing sugar alcohol necessary for the formation of membranes of modern living cells and organelles. our experimental results are fully consistent with a suggested reaction scheme in which glycerol is formed along a chain of radical-radical and radical-molecule interactions between various reactive intermediates produced upon hydrogenation of co ice or its hydrogenation products. the tentative identification of the chemically related simple sugar glyceraldehyde—hoch2ch(oh)cho—is discussed as well. these new laboratory findings indicate that the proposed reaction mechanism holds much potential to form even more complex sugar alcohols and simple sugars. | formation of glycerol through hydrogenation of co ice under prestellar core conditions |
mini-euso is a telescope observing the earth in the ultraviolet band from the international space station. it is a part of the jem-euso program, paving the way to future larger missions, such as k-euso and poemma, devoted primarily to the observation of ultrahigh-energy cosmic rays from space. mini-euso is capable of observing extensive air showers generated by ultrahigh-energy cosmic rays with an energy above 1021 ev and to detect artificial showers generated with lasers from the ground. other main scientific objectives of the mission are the search for nuclearites and strange quark matter, the study of atmospheric phenomena such as transient luminous events, meteors, and meteoroids, the observation of sea bioluminescence and of artificial satellites and man-made space debris. mini-euso will map the nighttime earth in the uv range (290-430 nm), with a spatial resolution of about 6.3 km and a temporal resolution of 2.5 μs, through a nadir-facing uv-transparent window in the russian zvezda module. the instrument, launched on 2019 august 22, from the baikonur cosmodrome, is based on an optical system employing two fresnel lenses and a focal surface composed of 36 multianode photomultiplier tubes, 64 channels each, for a total of 2304 channels with single-photon counting sensitivity and an overall field of view of 44°. mini-euso also contains two ancillary cameras to complement measurements in the near-infrared and visible ranges. in this paper, we describe the detector and present the various phenomena observed in the first months of operations. | mini-euso mission to study earth uv emissions on board the iss |
continuum gamma-ray emission produced by interactions of cosmic rays with interstellar matter and radiation fields is a probe of non-thermal particle populations in galaxies. after decades of continuous improvements in experimental techniques and an ever-increasing sky and energy coverage, gamma-ray observations reveal in unprecedented detail the properties of galactic cosmic rays. a variety of scales and environments are now accessible to us, from the local interstellar medium near the sun and the vicinity of cosmic-ray accelerators, out to the milky way at large and beyond, with a growing number of gamma-ray emitting star-forming galaxies. gamma-ray observations have been pushing forward our understanding of the life cycle of cosmic rays in galaxies and, combined with advances in related domains, they have been challenging standard assumptions in the field and have spurred new developments in modelling approaches and data analysis methods. we provide a review of the status of the subject and discuss perspectives on future progress. | gamma rays as probes of cosmic-ray propagation and interactions in galaxies |
we analyze recent ams-02 comic-ray measurements of lithium, beryllium, boron, carbon, nitrogen, and oxygen. the emphasis of the analysis is on systematic uncertainties related to propagation and nuclear cross sections. to investigate the uncertainties in the propagation scenario, we consider five different frameworks, differing with respect to the inclusion of a diffusion break at a few gv, the presence of reacceleration, and the presence of a break in the injection spectra of primaries. for each framework we fit the diffusion equations of cosmic rays and explore the parameter space with monte carlo methods. at the same time, the impact of the uncertainties on the nuclear production cross sections of secondaries is explicitly considered and included in the fit through the use of nuisance parameters. we find that all of the considered frameworks are able to provide a good fit. in particular, two competing scenarios—one including a break in diffusion but no reacceleration and the other with reacceleration but no break in diffusion—are both allowed. the inclusion of cross-section uncertainties is, however, crucial to this result. thus, at the moment these uncertainties represent a fundamental systematic preventing a deeper understanding of the properties of cosmic-ray propagation. nonetheless, we find that the slope of diffusion at intermediate rigidities is robustly constrained in the range δ ≃0.45 - 0.5 in models without convection, or δ ≃0.4 - 0.5 if convection is included in the fit. furthermore, we find that the use of the ams-02 beryllium data provides a lower limit on the vertical size of the galactic propagation halo of zh≳3 kpc . | implications of lithium to oxygen ams-02 spectra on our understanding of cosmic-ray diffusion |
despite the uncovered association of a high-energy neutrino with the apparent flaring state of blazar txs 0506+056 in 2017, the mechanisms leading to astrophysical particle acceleration and neutrino production are still uncertain. recent studies found that when transparent to γ-rays, γ-flaring blazars do not have the opacity for protons to produce neutrinos. here we present observational evidence for an alternative explanation, in which γ-ray emission is suppressed during efficient neutrino production. a large proton and target photon density helps produce neutrinos while temporarily suppressing the observable γ-emission due to a large γγ opacity. we show that the fermi-lat γ-flux of blazar pks 1502+106 was at a local minimum when icecube recorded the coincident high-energy neutrino ic-190730a. using data from the ovro 40 m telescope, we find that radio emission from pks 1502+106 at the time period of the coincident neutrino ic-190730a was in a high state, in contrast to earlier time periods when radio and γ fluxes are correlated for both low and high states. this points to an active outflow that is γ-suppressed at the time of neutrino production. we find similar local γ-suppression in other blazars, including in magic's tev flux of txs 0506+056 and fermi-lat's flux of blazar pks b1424-418 at the time of coincident icecube neutrino detections. using temporary γ-suppression, neutrino-blazar coincidence searches could be substantially more sensitive than previously assumed, enabling the identification of the origin of icecube's diffuse neutrino flux possibly with already existing data. | cosmic neutrinos from temporarily gamma-suppressed blazars |
context. despite their vital importance to understanding galaxy evolution and our own galactic ecosystem, our knowledge of the physical properties of the hot x-ray emitting phase of the milky way is still inadequate. however, sensitive srg/erosita large area surveys are now providing us with the long-sought data needed to mend this state of affairs.aims: our aim is to constrain the properties of the milky way hot halo emission toward intermediate galactic latitudes close to the galactic anti-center.methods: we analyzed the spectral properties of the integrated soft x-ray emission observed by erosita in the relatively deep efeds field.results: we observe a flux of 12.6 and 5.1 × 10−12 erg cm−2 s−1 deg−2 in the total (0.3-2) and soft (0.3-0.6 kev) band. we measure the temperature and metal (oxygen) abundance of the hot circumgalactic medium (cgm) to be within ktcgm = 0.153-0.178 kev and zcgm = 0.052-0.072 z⊙, depending on the contribution of solar wind charge exchange (swcx). slightly higher cgm abundances zcgm = 0.05-0.10 z⊙ are possible, considering the uncertain extrapolation of the extragalactic cosmic x-ray background (cxb) emission below ~1 kev. to recover cgm abundances as high as zcgm = 0.3 z⊙, the presence of an additional component must be postulated, likely associated with the warm-hot intergalactic medium, providing ~15-20% of the flux in the soft x-ray band. we observe line widths of the cgm plasma smaller than δυ ≤ 500 km s−1. the emission in the soft band is dominated (~47%) by the circumgalactic medium (cgm), whose contribution reduces to ~30% if heliospheric swcx contributes at the level of ~15% also during solar minimum. the remaining flux is provided by the cxb (~33%) and the local hot bubble (~18%). moreover, the erosita data require the presence of an additional component associated with the elusive galactic corona plus a possible contribution from unresolved m dwarf stars. this component has a temperature of kt ~ 0.4- 0.7 kev, a considerable (~ kiloparsec) scale height, and might be out of thermal equilibrium. it contributes ~9% to the total emission in the 0.6—2 kev band, and is therefore a likely candidate to produce part of the unresolved cxb flux observed in x-ray ultra-deep fields. we also observe a significant contribution to the soft x-ray flux due to swcx, during periods characterized by stronger solar wind activity, and causing the largest uncertainty on the determination of the cgm temperature.conclusions: we constrain temperature, emission measure, abundances, thermal state, and spectral shape of the outer hot cgm of the milky way. | abundance and temperature of the outer hot circumgalactic medium. the srg/erosita view of the soft x-ray background in the efeds field |
the recent interpretation of cold dark matter as the sum of contributions of different mass primordial black hole (pbh) families [1] could explain a number of so far unsolved astrophysical mysteries. here i assume a realistic 10-8-1010 msolar pbh mass distribution providing the bulk of the dark matter, consistent with all observational constraints. i estimate the contribution of baryon accretion onto this pbh population to various cosmic background radiations, concentrating first on the cross-correlation signal between the cosmic x-ray and the cosmic infrared background fluctuations discovered in deep chandra and spitzer surveys. i assume bondi capture and advection dominated disk accretion with reasonable parameters like baryon density and effective relative velocity between baryons and pbh, as well as appropriate accretion and radiation efficiencies, and integrate these over the pbh mass spectrum and cosmic time. the prediction of the pbh contribution to the x-ray background is indeed consistent with the residual x-ray background signal and the x-ray/infrared fluctuations. the predicted flux peaks at redshifts z≈17-30, consistent with other constraints requiring the signal to come from such high redshifts. the pbh contribution to the 2-5 μm cosmic infrared background fluctuations is only about 1%, so that these likely come from star formation processes in regions associated with the pbh. i discuss a number of other phenomena, which could be significantly affected by the pbh accretion. magnetic fields are an essential ingredient in the bondi capture process, and i argue that the pbh can play an important role in amplifying magnetic seed fields in the early universe and maintaining them until the galactic dynamo processes set in. next i study the contribution of the assumed pbh population to the re-ionization history of the universe and find that they do not conflict with the stringent ionization limits set by the most recent planck measurements. x-ray heating from the pbh population can provide a contribution to the entropy floor observed in groups of galaxies. the tantalizing redshifted 21-cm absorption line feature observed by edges could well be connected to the radio emission contributed by pbh to the cosmic background radiation. finally, the number of intermediate-mass black holes and the diffuse x-ray emission in the galactic center region are not violated by the assumed pbh dark matter, on the contrary, some of the discrete sources resolved in the deepest {\em chandra} observations of the galactic ridge could indeed be accreting pbh. | illuminating the dark ages: cosmic backgrounds from accretion onto primordial black hole dark matter |
the locally observed cosmic ray spectrum has several puzzling features, such as the excess of positrons and antiprotons above ∼20 gev and the discrepancy in the slopes of the spectra of cosmic ray protons and heavier nuclei in the tev-pev energy range. we show that these features are consistently explained by a nearby source which was active approximately two million years ago and has injected (2 - 3 )×1 050 erg in cosmic rays. the transient nature of the source and its overall energy budget point to the supernova origin of this local cosmic ray source. the age of the supernova suggests that the local cosmic ray injection was produced by the same supernova that has deposited <mml:mmultiscripts>fe 60 </mml:mmultiscripts> isotopes in the deep ocean crust. | signatures of a two million year old supernova in the spectra of cosmic ray protons, antiprotons, and positrons |
we perform three-dimensional simulations of magnetorotational supernovae using a $39\, {\rm m}_{\odot }$ progenitor star with two different initial magnetic field strengths of 1010 and 1012 g in the core. both models rapidly undergo shock revival, and their explosion energies asymptote within a few hundred milliseconds to values of ≳2 × 1051 erg after conservatively correcting for the binding energy of the envelope. magnetically collimated, non-relativistic jets form in both models, though the jets are subject to non-axisymmetric instabilities. the jets do not appear crucial for driving the explosion, as they only emerge once the shock has already expanded considerably. our simulations predict moderate neutron star kicks of about 150 km s-1, no spin-kick alignment, and rapid early spin-down that would result in birth periods of about 20 ms, too slow to power an energetic gamma-ray burst jet. more than $0.2\, {\rm m}_\odot$ of iron-group material is ejected, but we estimate that the mass of ejected 56ni will be considerably smaller as the bulk of this material is neutron-rich. explosive burning does not contribute appreciable amounts of 56ni because the burned material originates from the slightly neutron-rich silicon shell. the iron-group ejecta also showed no pronounced bipolar geometry by the end of the simulations. the models thus do not immediately fit the characteristics of observed hypernovae, but may be representative of other transients with moderately high explosion energies. the gravitational-wave emission reaches high frequencies of up to 2000 hz and amplitudes of over 100 cm. the gravitational-wave emission is detectable out to distances of ~4 mpc in the planned cosmic explorer detector. | three dimensional magnetorotational core-collapse supernova explosions of a 39 solar mass progenitor star |
the cherenkov telescope array (cta) is the major next-generation observatory for ground-based very-high-energy gamma-ray astronomy. it will improve the sensitivity of current ground-based instruments by a factor of five to twenty, depending on the energy, greatly improving both their angular and energy resolutions over four decades in energy (from 20 gev to 300 tev). this achievement will be possible by using tens of imaging cherenkov telescopes of three successive sizes. they will be arranged into two arrays, one per hemisphere, located on the la palma island (spain) and in paranal (chile). we present here the optimised and final telescope arrays for both cta sites, as well as their foreseen performance, resulting from the analysis of three different large-scale monte carlo productions. | monte carlo studies for the optimisation of the cherenkov telescope array layout |
we study high-energy neutrino emission from relativistic jets launched by a black hole (bh) spiraling-in inside the envelope of a red supergiant (rsg), and find that such common envelope jets supernovae (cejsne) are a potential source for the $\gtrsim 10^{15} ~\rm {ev}$ neutrinos detected by icecube. we first use the stellar evolution code mesa to mimic the effect of the jets on the rsg envelope, and find that the jets substantially inflate the envelope. we then study the propagation of jets inside the extended rsg envelope and find that in most cases the jets do not penetrate the envelope but are rather stalled. we show that such jets can accelerate cosmic rays to high enough energies to produce high-energy neutrinos. while the neutrinos stream out freely, the gamma-rays that accompany the neutrino production remain trapped inside the optically thick envelope. this explains the lack of observational association between high-energy neutrinos and gamma rays. we crudely estimate the diffuse neutrino spectrum from a cejsn and find that cejsne with bh companions might have a substantial contribution to the high-energy neutrinos flux detected by icecube. | common envelope jets supernovae with a black hole companion as possible high-energy neutrino sources |
neutron stars (nss) and black holes (bhs) are born when the final collapse of the stellar core terminates the lives of stars more massive than about 9 msun. this can trigger the powerful ejection of a large fraction of the star's material in a core-collapse supernova (ccsn), whose extreme luminosity is energized by the decay of radioactive isotopes such as 56ni and 56co. when evolving in close binary systems, the compact relics of such infernal catastrophes spiral towards each other on orbits gradually decaying by gravitational-wave emission. ultimately, the violent collision of the two components forms a more massive, rapidly spinning remnant, again accompanied by the ejection of considerable amounts of matter. these merger events can be observed by high-energy bursts of gamma rays with afterglows and electromagnetic transients called kilonovae, which radiate the energy released in radioactive decays of freshly assembled rapid neutron-capture elements. by means of their mass ejection and the nuclear and neutrino reactions taking place in the ejecta, both ccsne and compact object mergers (coms) are prominent sites of heavy-element nucleosynthesis and play a central role in the cosmic cycle of matter and the chemical enrichment history of galaxies. the nuclear equation of state (eos) of ns matter, from neutron-rich to proton-dominated conditions and with temperatures ranging from about zero to ~100 mev, is a crucial ingredient in these astrophysical phenomena. it determines their dynamical processes, their remnant properties even at the level of deciding between ns or bh, and the properties of the associated emission of neutrinos, whose interactions govern the thermodynamic conditions and the neutron-to-proton ratio for nucleosynthesis reactions in the innermost ejecta. this chapter discusses corresponding eos dependent effects of relevance in ccsne as well as coms. (slightly abridged) | dynamics and equation of state dependencies of relevance for nucleosynthesis in supernovae and neutron star mergers |
light halo dark matter (dm) particles upscattered by high-energy cosmic rays (crs) can be energetic, and become detectable by conventional direct detection experiments. the current constraints derived from space-based direct cr measurements can reach o (10-31) cm2 for a constant dm-nucleon scattering cross section. we show that if the cr energy spectrum follows a power law of type ∼e-3, the derived constraints on the scattering cross section will be highly insensitive to dm particle mass. this suggests that ultrahigh-energy crs (uhecrs) indirectly measured by ground-based detectors can be used to place constraints on ultralight dm particles, as e-3 is a very good approximation of the uhecr energy spectrum up to energy ∼1020 ev. using the recent uhecr flux data, we show that the current constraints derived from space-based cr measurements can in principle be extended to ultralight dm particles far below ev scale. | constraining light dark matter upscattered by ultrahigh-energy cosmic rays |
we study the thermal structure of the neutral atomic (h i) interstellar medium across a wide range of metallicities, from supersolar down to vanishing metallicity, and for varying uv intensities and cosmic-ray (cr) ionization rates. we calculate self-consistently the gas temperature and species abundances (with a special focus on the residual h2), assuming a thermal and chemical steady state. for solar metallicity, z‧ ≡ 1, we recover the known result that there exists a pressure range over which the gas is multiphased, with the warm (∼104 k, warm neutral medium (wnm)) and cold (∼100 k, cold neutral medium (cnm)) phases coexisting at the same pressure. at a metallicity z‧ ≈ 0.1, the cnm is colder (compared to z‧ = 1) due to the reduced efficiency of photoelectric heating. for z‧ ≲ 0.1, cr ionization becomes the dominant heating mechanism and the wnm-to-cnm transition shifts to ever-increasing pressure/density as the metallicity is reduced. for metallicities z‧ ≲ 0.01, h2 cooling becomes important, lowering the temperature of the wnm (down to ≈600 k), and smoothing out the multiphase phenomenon. at vanishing metallicities, h2 heating becomes effective and the multiphase phenomenon disappears entirely. we derive analytic expressions for the critical densities for the warm-to-cold phase transition in the different regimes, and the critical metallicities for h2 cooling and heating. we discuss potential implications on the star formation rates of galaxies and self-regulation theories. | thermal phases of the neutral atomic interstellar medium from solar metallicity to primordial gas |
we combine and extend the analyses of effective scalar, vector, majorana and dirac fermion higgs portal models of dark matter (dm), in which dm couples to the standard model (sm) higgs boson via an operator of the form odmh†h . for the fermion models, we take an admixture of scalar ψ ¯ψ and pseudoscalar ψ ¯ i γ5ψ interaction terms. for each model, we apply constraints on the parameter space based on the planck measured dm relic density and the lhc limits on the higgs invisible branching ratio. for the first time, we perform a consistent study of the indirect detection prospects for these models based on the wmap7/planck observations of the cosmic microwave background, a combined analysis of 15 dwarf spheroidal galaxies by fermi-lat and the upcoming cherenkov telescope array (cta). we also perform a correct treatment of the momentum-dependent direct search cross section that arises from the pseudoscalar interaction term in the fermionic dm theories. we find, in line with previous studies, that current and future direct search experiments such as lux and xenon1t can exclude much of the parameter space, and we demonstrate that a joint observation in both indirect and direct searches is possible for high mass weakly interacting massive particles. in the case of a pure pseudoscalar interaction of a fermionic dm candidate, future gamma-ray searches are the only class of experiment capable of probing the high mass range of the theory. | combined analysis of effective higgs portal dark matter models |
the presence of dark matter has been ascertained through a wealth of astrophysical and cosmological phenomena and its nature is a central puzzle in modern science. elementary particles stand as the most compelling explanation. they have been intensively searched for at underground laboratories looking for an energy recoil signal and at telescopes sifting for excess events in gamma-ray or cosmic-ray observations. in this work, we investigate a detection method based on spectroscopy measurements of neutron stars. we outline the luminosity and age of neutrons stars whose dark matter scattering off neutrons can heat neutron stars up to a measurable level. we show that in this case neutron star spectroscopy could constitute the best probe for dark matter particles over a wide masses and interactions strength. | detecting dark matter with neutron star spectroscopy |
hot gas pervades the universe: about half of the baryonic content in the universe is expected to be at t > 105 k, and there are as many baryons at t > 107 trapped in galaxy clusters as there are locked into stars. there is an intimate relation between this hot gas, which delineates the large-scale structure of the universe, and the most energetic phenomena occurring in the immediate vicinity of super-massive black holes, through a poorly known process called cosmic feedback. studying the hot and energetic universe requires x-ray observatories in space, whose capabilities greatly exceed those of the current workhorse observatories: nasa's chandra and esa's xmm- newton. athena has been selected by esa as the l2 mission (due for launch in 2028), to address the “hot and energetic universe” science theme. it will be a large x-ray observatory capable of addressing the above topics, and many other fundamental questions in contemporary astrophysics. here we present the athena science objectives, the mission concept and its payload, including the x-ray telescope and its two baseline instruments: a wide field imager (wfi) and an x-ray integral field unit (x-ifu). | athena: the x-ray observatory to study the hot and energetic universe |
galaxy clusters exhibit remarkable self-similar behavior which allows us to establish simple scaling relationships between observable quantities and cluster masses, making galaxy clusters useful cosmological probes. recent x-ray observations suggested that self-similarity may be broken in the outskirts of galaxy clusters. in this work, we analyze a mass-limited sample of massive galaxy clusters from the omega500 cosmological hydrodynamic simulation to investigate the self-similarity of the diffuse x-ray emitting intracluster medium (icm) in the outskirts of galaxy clusters. we find that the self-similarity of the outer icm profiles is better preserved if they are normalized with respect to the mean density of the universe, while the inner profiles are more self-similar when normalized using the critical density. however, the outer icm profiles as well as the location of accretion shock around clusters are sensitive to their mass accretion rate, which causes the apparent breaking of self-similarity in cluster outskirts. we also find that the collisional gas does not follow the distribution of collisionless dark matter (dm) perfectly in the infall regions of galaxy clusters, leading to 10% departures in the gas-to-dm density ratio from the cosmic mean value. our results have a number implications for interpreting observations of galaxy clusters in x-ray and through the sunyaev-zel’dovich effect, and their applications to cosmology. | mass accretion and its effects on the self-similarity of gas profiles in the outskirts of galaxy clusters |
x-ray and γ-ray observations by the swift satellite revealed that a fraction of tidal disruption events (tdes) have relativistic jets. jetted tdes have been considered to be potential sources of very-high-energy cosmic-rays and neutrinos. in this work, using semi-analytical methods, we calculate neutrino spectra of x-ray bright tdes with powerful jets and dark tdes with possible choked jets, respectively. we estimate their neutrino fluxes and find that non-detection would give us an upper limit on the baryon loading of the jet luminosity contained in cosmic-rays ξ cr ≲ 20-50 for sw j1644+57. we show that x-ray bright tdes make a sub-dominant (≲5%-10%) contribution to icecube’s diffuse neutrino flux, and study possible contributions of x-ray dark tdes given that particles are accelerated in choked jets or disk winds. we discuss future prospects for multi-messenger searches of the brightest tdes. | high-energy neutrino flares from x-ray bright and dark tidal disruption events |
in this letter, we report the first measurement of the inelastic cross section for antideuteron-nucleus interactions at low particle momenta, covering a range of 0.3 ≤p <4 gev /c . the measurement is carried out using p -pb collisions at a center-of-mass energy per nucleon-nucleon pair of √{snn }=5.02 tev , recorded with the alice detector at the cern lhc and utilizing the detector material as an absorber for antideuterons and antiprotons. the extracted raw primary antiparticle-to-particle ratios are compared to the results from detailed alice simulations based on the geant4 toolkit for the propagation of (anti)particles through the detector material. the analysis of the raw primary (anti)proton spectra serves as a benchmark for this study, since their hadronic interaction cross sections are well constrained experimentally. the first measurement of the inelastic cross section for antideuteron-nucleus interactions averaged over the alice detector material with atomic mass numbers ⟨a ⟩=17.4 and 31.8 is obtained. the measured inelastic cross section points to a possible excess with respect to the glauber model parametrization used in geant4 in the lowest momentum interval of 0.3 ≤p <0.47 gev /c up to a factor 2.1. this result is relevant for the understanding of antimatter propagation and the contributions to antinuclei production from cosmic ray interactions within the interstellar medium. in addition, the momentum range covered by this measurement is of particular importance to evaluate signal predictions for indirect dark-matter searches. | measurement of the low-energy antideuteron inelastic cross section |
the dark matter particle explorer (dampe) satellite detector announced its first result for measuring the cosmic-ray electron/positron (cre) energy spectrum up to 4.6 tev, including a tentative peak-like event excess at (1.3-1.5) tev. in this work, we uncover a significant hidden excess in the dampe cre spectrum over the energy range (0.6-1.1) tev, which has a non-peak-like structure. we propose a new mechanism to explain this excess by a set of 1.5 tev μ± events with subsequent decays into e± plus neutrinos. for explaining this new excess together with the peak excess around 1.4 tev, we demonstrate that the flavor structure of the original lepton final-state produced by dark matter (dm) annihilations (or other mechanism) should have a composition ratio ne : (nμ + 1/6 nτ) = 1 : y, with y ≃ 2.6- 10.8. for lepton portal dm models, this puts nontrivial constraint on the lepton-dm-mediator couplings λe : (λμ 4 + 1/6 λτ4)1/4 = 1 :y 1/4with a narrow range y 1/4≃ 1.3- 1.8. | flavor structure of the cosmic-ray electron/positron excesses at dampe |
we present here the cosmo-slics, a new suite of simulations specially designed for the analysis of current and upcoming weak lensing data beyond the standard two-point cosmic shear. we sampled the [ωm, σ8, h, w0] parameter space at 25 points organised in a latin hyper-cube, spanning a range that contains most of the 2σ posterior distribution from ongoing lensing surveys. at each of these nodes we evolved a pair of n-body simulations in which the sampling variance is highly suppressed, and ray-traced the volumes 800 times to further increase the effective sky coverage. we extracted a lensing covariance matrix from these pseudo-independent light-cones and show that it closely matches a brute-force construction based on an ensemble of 800 truly independent n-body runs. more precisely, a fisher analysis reveals that both methods yield marginalized two-dimensional constraints that vary by less than 6% in area, a result that holds under different survey specifications and that matches to within 15% the area obtained from an analytical covariance calculation. extending this comparison with our 25 wcdm models, we probed the cosmology dependence of the lensing covariance directly from numerical simulations, reproducing remarkably well the fisher results from the analytical models at most cosmologies. we demonstrate that varying the cosmology at which the covariance matrix is evaluated in the first place might have an order of magnitude greater impact on the parameter constraints than varying the choice of covariance estimation technique. we present a test case in which we generate fast predictions for both the lensing signal and its associated variance with a flexible gaussian process regression emulator, achieving an accuracy of a few percent on the former and 10% on the latter. | cosmic shear covariance matrix in wcdm: cosmology matters |
the pythia event generator is used in several contexts to study hadron and lepton interactions, notably p p and p p ¯ collisions. in this article we extend the hadronic modelling to encompass the collision of a wide range of hadrons h with either a proton or a neutron, or with a simplified model of nuclear matter. to this end we model h p total and partial cross sections as a function of energy, and introduce new parton distribution functions for a wide range of hadrons, as required for a proper modelling of multiparton interactions. the potential usefulness of the framework is illustrated by a simple study of the evolution of cosmic rays in the atmosphere, and by an even simpler one of shower evolution in a solid detector material. the new code will be made available for future applications. | hadron interactions for arbitrary energies and species, with applications to cosmic rays |
the current work focuses on the process of vacuum cherenkov radiation for lorentz-violating fermions that are described by the minimal standard-model extension (sme). to date, most considerations of this important hypothetical process have been restricted to lorentz-violating photons, as the necessary theoretical tools for the sme fermion sector have not been available. with their development in a very recent paper, we are now in a position to compute the decay rates based on a modified dirac theory. two realizations of the cherenkov process are studied. in the first scenario, the spin projection of the incoming fermion is assumed to be conserved, and in the second, the spin projection is allowed to flip. the first type of process is shown to be still forbidden for the dimensionful a and b coefficients where there are strong indications that it is energetically disallowed for the h coefficients, as well. however, it is rendered possible for the dimensionless c , d , e , f , and g coefficients. for large initial fermion energies, the decay rates for the c and d coefficients were found to grow linearly with momentum and to be linearly suppressed by the smallness of the lorentz-violating coefficient where for the e , f , and g coefficients this suppression is even quadratic. the decay rates vanish in the vicinity of the threshold, as expected. the decay including a fermion spin-flip plays a role for the spin-nondegenerate operators and it was found to occur for the dimensionful b and h coefficients as well as for the dimensionless d and g . the characteristics of this process differ much from the properties of the spin-conserving one, e.g., there is no threshold. based on experimental data of ultra-high-energy cosmic rays, new constraints on lorentz violation in the quark sector are obtained from the thresholds. however, it does not seem to be possible to derive bounds from the spin-flip decays. this work reveals the usefulness of the quantum field theoretic methods recently developed to study the phenomenology of high-energy fermions within the framework of the sme. | vacuum cherenkov radiation for lorentz-violating fermions |
measuring soil moisture with cosmic-ray neutrons is a promising technique for intermediate spatial scales. to convert neutron counts to average volumetric soil water content a simple calibration function can be used (the n0-calibration of desilets et al., 2010). the calibration is based on soil water content derived directly from soil samples taken within the footprint of the sensor. we installed a cosmic-ray neutron sensor (crs) in a mixed forest in the lowlands of north-eastern germany and calibrated it 10 times throughout one calendar year. each calibration with the n0-calibration function resulted in a different crs soil moisture time series, with deviations of up to 0.1 m3 m-3 (24 % of the total range) for individual values of soil water content. also, many of the calibration efforts resulted in time series that could not be matched with independent in situ measurements of soil water content. we therefore suggest a modified calibration function with a different shape that can vary from one location to another. a two-point calibration was found to effectively define the shape of the modified calibration function if the calibration points were taken during both dry and wet conditions spanning at least half of the total range of soil moisture. the best results were obtained when the soil samples used for calibration were linearly weighted as a function of depth in the soil profile and nonlinearly weighted as a function of distance from the crs, and when the depth-specific amount of soil organic matter and lattice water content was explicitly considered. the annual cycle of tree foliation was found to be a negligible factor for calibration because the variable hydrogen mass in the leaves was small compared to the hydrogen mass changes by soil moisture variations. as a final point, we provide a calibration guide for a crs in forested environments. | use of cosmic-ray neutron sensors for soil moisture monitoring in forests |
muography (or muon radiography) is a technique that exploits the penetration capability of muons, elementary particles similar to electrons but with a mass about 200 times larger. high energy muons are naturally produced in the interactions of cosmic rays with the earth atmosphere. the measurement of their absorption in matter allows the imaging of the inner structure of large bodies. the technological developments in the detection of elementary particles have opened the way to its application in various fields, such as archaeology, studies of geological structures, civil engineering and security issues. we have developed a new approach to the three-dimensional muography of underground structures, capable of directly localising hidden cavities and of reconstructing their shape in space. our measurements at mt. echia, the site of the earliest settlement of the city of naples in the 8th century bc, have led us to the discovery of a hidden underground cavity, whose existence was not evident with the usual two-dimensional muography graphs. we demonstrate here that our original approach definitely enhances muography discovery potential, especially in case of complex underground systems. | 3d muography for the search of hidden cavities |
a full energy and flavor-dependent analysis of the three-year high-energy icecube neutrino events is presented. by means of multidimensional fits, we derive the current preferred values of the high-energy neutrino flavor ratios, the normalization and spectral index of the astrophysical fluxes, and the expected atmospheric background events, including a prompt component. a crucial assumption resides on the choice of the energy interval used for the analyses, which significantly biases the results. when restricting ourselves to the ∼30 tev - 3 pev energy range, which contains all the observed icecube events, we find that the inclusion of the spectral information improves the fit to the canonical flavor composition at earth, (1 ∶1 ∶1 )⊕ , with respect to a single-energy bin analysis. increasing both the minimum and the maximum deposited energies has dramatic effects on the reconstructed flavor ratios as well as on the spectral index. imposing a higher threshold of 60 tev yields a slightly harder spectrum by allowing a larger muon neutrino component, since above this energy most atmospheric tracklike events are effectively removed. extending the high-energy cutoff to fully cover the glashow resonance region leads to a softer spectrum and a preference for tau neutrino dominance, as none of the expected electron (anti)neutrino induced showers have been observed so far. the lack of showers at energies above 2 pev may point to a broken power-law neutrino spectrum. future data may confirm or falsify whether the recently discovered high-energy neutrino fluxes and the long-standing detected cosmic rays have a common origin. | spectral analysis of the high-energy icecube neutrinos |
distant bl lacertae objects emit γ-rays that interact with the extragalactic background light (ebl), creating electron-positron pairs, and reducing the flux measured by ground-based imaging atmospheric cherenkov telescopes (iacts) at very-high energies (vhe). these pairs can compton-scatter the cosmic microwave background, creating a γ-ray signature at slightly lower energies that is observable by the fermi large area telescope (lat). this signal is strongly dependent on the intergalactic magnetic field (igmf) strength (b) and its coherence length (lb). we use iact spectra taken from the literature for 5 vhe-detected bl lac objects and combine them with lat spectra for these sources to constrain these igmf parameters. low b values can be ruled out by the constraint that the cascade flux cannot exceed that observed by the lat. high values of b can be ruled out from the constraint that the ebl-deabsorbed iact spectrum cannot be greater than the lat spectrum extrapolated into the vhe band, unless the cascade spectrum contributes a sizable fraction of the lat flux. we rule out low b values (b ≲ 10-19 g for lb ≥ 1 mpc) at >5σ in all trials with different ebl models and data selection, except when using >1 gev spectra and the lowest ebl models. we were not able to constrain high values of b. | constraints on the intergalactic magnetic field with gamma-ray observations of blazars |
it has been suggested that the weak magnetic field hosted by the intergalactic medium in cosmic voids could be a relic from the early universe. however, accepted models of turbulent magnetohydrodynamic decay predict that the present-day strength of fields originally generated at the electroweak phase transition (ewpt) without parity violation would be too low to explain the observed scattering of γ-rays from tev blazars. here, we propose that the decay is mediated by magnetic reconnection and conserves the mean square fluctuation level of magnetic helicity. we find that the relic fields would be stronger by several orders of magnitude under this theory than was indicated by previous treatments, which restores the consistency of the ewpt-relic hypothesis with the observational constraints. moreover, efficient ewpt magnetogenesis would produce relics at the strength required to resolve the hubble tension via magnetic effects at recombination and seed galaxy-cluster fields close to their present-day strength. | cosmic-void observations reconciled with primordial magnetogenesis |
with several proposed mev gamma-ray telescopes on the horizon, it is of paramount importance to perform accurate calculations of gamma-ray spectra expected from sub-gev dark matter annihilation and decay. we present hamza, a python package for reliably computing these spectra, determining the resulting constraints from existing gamma-ray data, and prospects for upcoming telescopes. for high-level analyses, hamza comes with several built-in dark matter models where the interactions between dark matter and hadrons have been determined in detail using chiral perturbation theory. additionally, hamza provides tools for computing spectra from individual final states with arbitrary numbers of light leptons and mesons, and for analyzing custom dark matter models. hamza can also produce electron and positron spectra from dark matter annihilation, enabling precise derivation of constraints from the cosmic microwave background. | hazma: a python toolkit for studying indirect detection of sub-gev dark matter |
we set conservative constraints on decaying dark matter particles with masses spanning a very wide range (104-1016 gev). for this we use multimessenger observations of cosmic-ray (cr) protons/antiprotons, electrons/positrons, neutrinos/antineutrinos and gamma rays. focusing on decays into the bar bb channel, we simulate the spectra of dark matter yields by using the dokshitzer-gribov-lipatov-altarelli-parisi equations and the pythia package. we then propagate the crs of dark matter origin till earth by using the state-of-the-art numerical frameworks crpropa, galprop and helmod for the solution of the cr transport equation in the extragalactic, galactic region and the heliosphere, respectively. conservative limits are obtained by requiring that the predicted dark matter spectra at earth be less than the observed cr spectra. overall, we exclude dark matter lifetimes of 1028 s or shorter for all the masses investigated in this work. the most stringent constraints reach 1030 s for very heavy dark matter particles with masses in the range 1011-1014 gev. | probing heavy dark matter decays with multi-messenger astrophysical data |
we report the first detection of the phosphorus monoxide ion (po+) in the interstellar medium. our unbiased and very sensitive spectral survey toward the g+0.693–0.027 molecular cloud covers four different rotational transitions of this molecule, two of which (j = 1–0 and j = 2–1) appear free of contamination from other species. the fit performed, assuming local thermodynamic equilibrium conditions, yields a column density of n=(6.0 ± 0.7) × 1011 cm−2. the resulting molecular abundance with respect to molecular hydrogen is 4.5 × 10–12. the column density of po+ normalized by the cosmic abundance of p is larger than those of no+ and so+, normalized by n and s, by factors of 3.6 and 2.3, respectively. the n(po+)/n(po) ratio is 0.12 ± 0.03, more than one order of magnitude higher than that of n(so+)/n(so) and n(no+)/n(no). these results indicate that p is more efficiently ionized than n and s in the ism. we have performed new chemical models that confirm that the po+ abundance is strongly enhanced in shocked regions with high values of cosmic-ray ionization rates (10–15 − 10–14 s−1), as occurring in the g+0.693–0.027 molecular cloud. the shocks sputter the interstellar icy grain mantles, releasing into the gas phase most of their p content, mainly in the form of ph3, which is converted into atomic p, and then ionized efficiently by cosmic rays, forming p+. further reactions with o2 and oh produces po+. the cosmic-ray ionization of po might also contribute significantly, which would explain the high n(po+)/n(po) ratio observed. the relatively high gas-phase abundance of po+ with respect to other p-bearing species stresses the relevance of this species in the interstellar chemistry of p. | ionize hard: interstellar po+ detection |
the sources of the majority of the high-energy astrophysical neutrinos observed with the icecube neutrino telescope at the south pole are unknown. so far, only a flaring gamma-ray blazar was compellingly associated with the emission of high-energy neutrinos. however, several studies suggest that the neutrino emission from the gamma-ray blazar population only accounts for a small fraction of the total astrophysical neutrino flux. in this work we probe the production of high-energy neutrinos in the cores of active galactic nuclei (agn), induced by accelerated cosmic rays in the accretion disk region. we present a likelihood analysis based on eight years of icecube data, searching for a cumulative neutrino signal from three agn samples created for this work. the neutrino emission is assumed to be proportional to the accretion disk luminosity estimated from the soft x-ray flux. next to the observed soft x-ray flux, the objects for the three samples have been selected based on their radio emission and infrared color properties. for the largest sample in this search, an excess of high-energy neutrino events with respect to an isotropic background of atmospheric and astrophysical neutrinos is found, corresponding to a post-trial significance of 2.60 σ . if interpreted as a genuine signal with the assumptions of a proportionality of x-ray and neutrino fluxes and a model for the subthreshold flux distribution, then this observation implies that at 100 tev, 27%-100% of the observed neutrinos arise from particle acceleration in the core of agn at 1 σ confidence interval. | search for neutrino emission from cores of active galactic nuclei |
we systematically investigate new physics scenarios that can modify the interactions between neutrinos and matter at upcoming tau neutrino telescopes, which will test neutrino-proton collisions with energies ≳ 45 tev, and can provide unique insights to the elusive tau neutrino. at such high energy scales, the impact of parton distribution functions of second and third generations of quarks (usually suppressed) can be comparable to the contribution of first generation with small momentum fraction, hence making tau neutrino telescopes an excellent facility to probe new physics associated with second and third families. among an inclusive set of particle physics models, we identify new physics scenarios at tree level that can give competitive contributions to the neutrino cross sections while staying within laboratory constraints: charged/neutral higgs and leptoquarks. our analysis is close to the actual experimental configurations of the telescopes, and we perform a χ2-analysis on the energy and angular distributions of the tau events. by numerically solving the propagation equations of neutrino and tau fluxes in matter, we obtain the sensitivities of representative upcoming tau neutrino telescopes, grand, poemma and trinity, to the charged higgs and leptoquark models. while each of the experiments can achieve a sensitivity better than the current collider reaches for certain models, their combination is remarkably complementary in probing the new physics. in particular, the new physics will affect the energy and angular distributions in different ways at those telescopes. | probing new physics at future tau neutrino telescopes |
feedback mediated by cosmic rays (crs) is an important process in galaxy formation. because crs are long-lived and because they are transported along magnetic field lines independently of any gas flow, they can efficiently distribute their feedback energy within the galaxy. we present an in-depth investigation of (i) how crs launch galactic winds from a disc that is forming in a $10^{11} \mathrm{m}_\odot$ halo and (ii) how cr transport affects the dynamics in a galactic outflow. to this end, we use the arepo moving-mesh code and model cr transport with the two-moment description of cr hydrodynamics. this model includes the cr interaction with gyroresonant alfvén waves that enables us to self-consistently calculate the cr diffusion coefficient and cr transport speeds based on coarse-grained models for plasma physical effects. this delivers insight into key questions such as whether the effective cr transport is streaming-like or diffusive-like, how the cr diffusion coefficient and transport speed change inside the circumgalactic medium (cgm), and to what degree the two-moment approximation is needed to faithfully capture these effects. we find that the cr-diffusion coefficient reaches a steady-state in most environments with the notable exception of our newly discovered alfvén-wave dark regions where the toroidal wind magnetic field is nearly perpendicular to the cr pressure gradient so that crs are unable to excite gyroresonant alfvén waves. however, cr transport itself cannot reach a steady-state and is not well described by either the cr streaming paradigm, the cr diffusion paradigm or a combination of both. | cosmic ray-driven galactic winds: transport modes of cosmic rays and alfvén-wave dark regions |
light sub-gev dark matter (dm) constitutes an underexplored target, beyond the optimized sensitivity of typical direct dm detection experiments. we comprehensively investigate hadrophilic light dm produced from cosmic-ray collisions with the atmosphere. the resulting relativistic dm, originating from meson decays, can be efficiently observed in variety of experiments, such as xenon1t. we include for the first time decays of η, η' and k+ mesons, leading to improved limits for dm masses above few hundred mev. we incorporate an exact treatment of the dm attenuation in earth and demonstrate that nuclear form factor effects can significantly impact the resulting testable dm parameter space. further, we establish projections for upcoming experiments, such as darwin, over a wide range of dm masses below the gev scale. | hadrophilic light dark matter from the atmosphere |
we formulate a magnetohydrodynamic-particle-in-cell (mhd-pic) method for describing the interaction between collisionless cosmic ray (cr) particles and a thermal plasma. the thermal plasma is treated as a fluid, obeying equations of ideal mhd, while crs are treated as relativistic lagrangian particles subject to the lorentz force. backreaction from crs to the gas is included in the form of momentum and energy feedback. in addition, we include the electromagnetic feedback due to cr-induced hall effect that becomes important when the electron-ion drift velocity of the background plasma induced by crs approaches the alfvén velocity. our method is applicable on scales much larger than the ion inertial length, bypassing the microscopic scales that must be resolved in conventional pic methods, while retaining the full kinetic nature of the crs. we have implemented and tested this method in the athena mhd code, where the overall scheme is second-order accurate and fully conservative. as a first application, we describe a numerical experiment to study particle acceleration in non-relativistic shocks. using a simplified prescription for ion injection, we reproduce the shock structure and the cr energy spectra obtained with more self-consistent hybrid-pic simulations, but at substantially reduced computational cost. we also show that the cr-induced hall effect reduces the growth rate of the bell instability and affects the gas dynamics in the vicinity of the shock front. as a step forward, we are able to capture the transition of particle acceleration from non relativistic to relativistic regimes, with momentum spectrum $f(p)\sim p^{-4}$ connecting smoothly through the transition, as expected from the theory of fermi acceleration. | magnetohydrodynamic-particle-in-cell method for coupling cosmic rays with a thermal plasma: application to non-relativistic shocks |
the detection of an astrophysical flux of neutrinos in the tev-pev energy range by the icecube neutrino observatory has opened new possibilities for the study of extreme cosmic accelerators. the apparent isotropy of the neutrino arrival directions favors an extragalactic origin for this flux, potentially created by a large population of distant sources. recent evidence for the detection of neutrino emission from extragalactic sources includes the active galaxies txs 0506+056 and ngc 1068. we here review the current status of the search for the sources of the high-energy neutrino flux, concentrating on its extragalactic contribution. we discuss the implications of these observations for multimessenger studies of cosmic sources and present an outlook for how additional observations by current and future instruments will help address fundamental questions in the emerging field of high-energy neutrino astronomy. | high-energy extragalactic neutrino astrophysics |
galactic winds regulate star formation in disc galaxies and help to enrich the circum-galactic medium. they are therefore crucial for galaxy formation, but their driving mechanism is still poorly understood. recent studies have demonstrated that cosmic rays (crs) can drive outflows if active cr transport is taken into account. using hydrodynamical simulations of isolated galaxies with virial masses between 1010 and 1013 m⊙, we study how the properties of cr-driven winds depend on halo mass. crs are treated in a two-fluid approximation and their transport is modelled through isotropic or anisotropic diffusion. we find that crs are only able to drive mass-loaded winds beyond the virial radius in haloes with masses below 1012 m⊙. for our lowest examined halo mass, the wind is roughly spherical and has velocities of ∼20 km s-1. with increasing halo mass, the wind becomes biconical and can reach 10 times higher velocities. the mass loading factor drops rapidly with virial mass, a dependence that approximately follows a power law with a slope between -1 and -2. this scaling is slightly steeper than observational inferences, and also steeper than commonly used prescriptions for wind feedback in cosmological simulations. the slope is quite robust to variations of the cr injection efficiency or the cr diffusion coefficient. in contrast to the mass loading, the energy loading shows no significant dependence on halo mass. while these scalings are close to successful heuristic models of wind feedback, the cr-driven winds in our present models are not yet powerful enough to fully account for the required feedback strength. | the dependence of cosmic ray-driven galactic winds on halo mass |
we present a measurement of the volumetric rate of superluminous supernovae (slsne) at z ∼ 1.0, measured using archival data from the first four years of the canada-france-hawaii telescope supernova legacy survey (snls). we develop a method for the photometric classification of slsne to construct our sample. our sample includes two previously spectroscopically identified objects, and a further new candidate selected using our classification technique. we use the point-source recovery efficiencies from perrett et al. and a monte carlo approach to calculate the rate based on our slsn sample. we find that the three identified slsne from snls give a rate of 91^{+76}_{-36} sne yr-1 gpc-3 at a volume-weighted redshift of z = 1.13. this is equivalent to 2.2^{+1.8}_{-0.9}× 10^{-4} of the volumetric core-collapse supernova rate at the same redshift. when combined with other rate measurements from the literature, we show that the rate of slsne increases with redshift in a manner consistent with that of the cosmic star formation history. we also estimate the rate of ultra-long gamma-ray bursts based on the events discovered by the swift satellite, and show that it is comparable to the rate of slsne, providing further evidence of a possible connection between these two classes of events. we also examine the host galaxies of the slsne discovered in snls, and find them to be consistent with the stellar-mass distribution of other published samples of slsne. | the volumetric rate of superluminous supernovae at z ∼ 1 |
multi-messenger astrophysics is a fast-growing, interdisciplinary field that combines data, which vary in volume and speed of data processing, from many different instruments that probe the universe using different cosmic messengers: electromagnetic waves, cosmic rays, gravitational waves and neutrinos. in this expert recommendation, we review the key challenges of real-time observations of gravitational wave sources and their electromagnetic and astroparticle counterparts, and make a number of recommendations to maximize their potential for scientific discovery. these recommendations refer to the design of scalable and computationally efficient machine learning algorithms; the cyber-infrastructure to numerically simulate astrophysical sources, and to process and interpret multi-messenger astrophysics data; the management of gravitational wave detections to trigger real-time alerts for electromagnetic and astroparticle follow-ups; a vision to harness future developments of machine learning and cyber-infrastructure resources to cope with the big-data requirements; and the need to build a community of experts to realize the goals of multi-messenger astrophysics. | enabling real-time multi-messenger astrophysics discoveries with deep learning |
context. snowlines in protoplanetary disks play an important role in planet formation and composition. since the co snowline is difficult to observe directly with co emission, its location has been inferred in several disks from spatially resolved alma observations of dco+ and n2h+.aims: n2h+ is considered to be a good tracer of the co snowline based on astrochemical considerations predicting an anti-correlation between n2h+ and gas-phase co. in this work, the robustness of n2h+ as a tracer of the co snowline is investigated.methods: a simple chemical network was used in combination with the radiative transfer code lime to model the n2h+ distribution and corresponding emission in the disk around tw hya. the assumed co and n2 abundances, corresponding binding energies, cosmic ray ionization rate, and degree of large-grain settling were varied to determine the effects on the n2h+ emission and its relation to the co snowline.results: for the adopted physical structure of the tw hya disk and molecular binding energies for pure ices, the balance between freeze-out and thermal desorption predicts a co snowline at 19 au, corresponding to a co midplane freeze-out temperature of 20 k. the n2h+ column density, however, peaks 5-30 au outside the snowline for all conditions tested. in addition to the expected n2h+ layer just below the co snow surface, models with an n2/co ratio ≳0.2 predict an n2h+ layer higher up in the disk due to a slightly lower photodissociation rate for n2 as compared to co. the influence of this n2h+ surface layer on the position of the emission peak depends on the total co and n2 abundances and the disk physical structure, but the emission peak generally does not trace the column density peak. a model with a total (gas plus ice) co abundance of 3 × 10-6 with respect to h2 fits the position of the emission peak previously observed for the tw hya disk.conclusions: the relationship between n2h+ and the co snowline is more complicated than generally assumed: for the investigated parameters, the n2h+ column density peaks at least 5 au outside the co snowline. moreover, the n2h+ emission can peak much further out, as far as 50 au beyond the snowline. hence, chemical modeling, as performed here, is necessary to derive a co snowline location from n2h+ observations. | robustness of n2h+ as tracer of the co snowline |
the sources of ultra-high energy (uhe) cosmic rays, which can have energies up to 1020 ev, remain a mystery. uhe neutrinos may provide important clues to understanding the nature of cosmic-ray sources. arianna aims to detect uhe neutrinos via radio (askaryan) emission from particle showers when a neutrino interacts with ice, which is an efficient method for neutrinos with energies between 1016 ev and 1020 ev. the arianna radio detectors are located in antarctic ice just beneath the surface. neutrino observation requires that radio pulses propagate to the antennas at the surface with minimum distortion by the ice and firn medium. using the residual hole from the south pole ice core project, radio pulses were emitted from a transmitter located up to 1.7 km below the snow surface. by measuring these signals with an arianna surface station, the angular and polarization reconstruction abilities are quantified, which are required to measure the direction of the neutrino. after deconvolving the raw signals for the detector response and attenuation from propagation through the ice, the signal pulses show no significant distortion and agree with a reference measurement of the emitter made in an anechoic chamber. furthermore, the signal pulses reveal no significant birefringence for our tested geometry of mostly vertical ice propagation. the origin of the transmitted radio pulse was measured with an angular resolution of 0.37o indicating that the neutrino direction can be determined with good precision if the polarization of the radio-pulse can be well determined. in the present study we obtained a resolution of the polarization vector of 2.7o. neither measurement show a significant offset relative to expectation. | probing the angular and polarization reconstruction of the arianna detector at the south pole |
majorons are (pseudo-)nambu-goldstone bosons associated with lepton number symmetry breaking due to the majorana mass term of neutrinos introduced in the seesaw mechanism. they are good dark matter candidates since their lifetime is suppressed by the lepton number breaking scale. we update constraints and discuss future prospects on majoron dark matter in the singlet majoron models based on neutrino, gamma-ray, and cosmic-ray telescopes in the mass region of mev-10 tev. | updated constraints and future prospects on majoron dark matter |
cosmic rays (crs) are a dynamically important component of the interstellar medium (ism) of galaxies. the ~gev crs that carry most cr energy and pressure are likely confined by self-generated turbulence, leading them to stream along magnetic field lines at the ion alfvén speed. however, the consequences of self-confinement for cr propagation on galaxy scales remain highly uncertain. in this paper, we use a large ensemble of magnetohydrodynamical turbulence simulations to quantify how the basic parameters describing ism turbulence - the sonic mach number, $\mathcal {m}$ (plasma compressibility), alfvén mach number, $\mathcal {m}_{\text{a0}}$ (strength of the large-scale field with respect to the turbulence), and ionization fraction by mass, χ - affect the transport of streaming crs. we show that the large-scale transport of crs whose small-scale motion consists of streaming along field lines is well described as a combination of streaming along the mean field and superdiffusion both along (parallel to) and across (perpendicular to) it; $\mathcal {m}_{\text{a0}}$ drives the level of anisotropy between parallel and perpendicular diffusion and χ modulates the magnitude of the diffusion coefficients, while in our choice of units, $\mathcal {m}$ is unimportant except in the sub-alfvénic ($\mathcal {m}_{\text{a0}}\lesssim 0.5$) regime. our finding that superdiffusion is ubiquitous potentially explains the apparent discrepancy between cr diffusion coefficients inferred from measurements close to individual sources compared to those measured on larger, galactic scales. finally, we present empirical fits for the diffusion coefficients as a function of plasma parameters that may be used as subgrid recipes for global ism, galaxy, or cosmological simulations. | turbulent diffusion of streaming cosmic rays in compressible, partially ionized plasma |
over the last decade, observations have shown that the mean mass of ultra-high-energy cosmic rays (uhecrs) increases progressively toward the highest energies. however, the precise composition is still unknown, and several theoretical studies hint at the existence of a subdominant proton component up to the highest energies. motivated by the exciting prospect of performing charged-particle astronomy with ultra-high-energy (uhe) protons we quantify the level of uhe-proton flux that is compatible with present multimessenger observations and the associated fluxes of neutral messengers produced in the interactions of the protons. we study this scenario with numerical simulations of two independent populations of extragalactic sources and perform a fit to the combined uhecr energy spectrum and composition observables, constrained by diffuse gamma-ray and neutrino observations. we find that up to of order $10\%$ of the cosmic rays at the highest energies can be uhe protons, although the result depends critically on the selected hadronic interaction model for the air showers. depending on the maximum proton energy ($e_\text{max}^\text{p}$) and the redshift evolution of sources, the associated flux of cosmogenic neutrinos and uhe gamma rays can significantly exceed the multimessenger signal of the mixed-mass cosmic rays. moreover, if $e_\text{max}^\text{p}$ is above the gzk limit, we predict a large flux of uhe neutrinos above eev energies that is absent in alternate scenarios for the origin of uhecrs. we present the implications and opportunities afforded by these uhe proton, neutrino and photon fluxes for future multimessenger observations. | constraints on the proton fraction of cosmic rays at the highest energies and the consequences for cosmogenic neutrinos and photons |
we present the results of a direct measurement of the cosmic-ray helium spectrum with the calet instrument in operation on the international space station since 2015. the observation period covered by this analysis spans from october 13, 2015, to april 30, 2022 (2392 days). the very wide dynamic range of calet allowed for the collection of helium data over a large energy interval, from ∼40 gev to ∼250 tev , for the first time with a single instrument in low earth orbit. the measured spectrum shows evidence of a deviation of the flux from a single power law by more than 8 σ with a progressive spectral hardening from a few hundred gev to a few tens of tev. this result is consistent with the data reported by space instruments including pamela, ams-02, and dampe and balloon instruments including cream. at higher energy we report the onset of a softening of the helium spectrum around 30 tev (total kinetic energy). though affected by large uncertainties in the highest energy bins, the observation of a flux reduction turns out to be consistent with the most recent results of dampe. a double broken power law is found to fit simultaneously both spectral features: the hardening (at lower energy) and the softening (at higher energy). a measurement of the proton to helium flux ratio in the energy range from 60 gev /n to about 60 tev /n is also presented, using the calet proton flux recently updated with higher statistics. | direct measurement of the cosmic-ray helium spectrum from 40 gev to 250 tev with the calorimetric electron telescope on the international space station |
the origin of ultrahigh energy cosmic rays (uhecrs) has been an open question for decades. here, we use a combination of hydrodynamic simulations and general physical arguments to demonstrate that uhecrs can in principle be produced by diffusive shock acceleration (dsa) in shocks in the backflowing material of radio galaxy lobes. these shocks occur after the jet material has passed through the relativistic termination shock. recently, several authors have demonstrated that highly relativistic shocks are not effective in accelerating uhecrs. the shocks in our proposed model have a range of non-relativistic or mildly relativistic shock velocities more conducive to uhecr acceleration, with shock sizes in the range 1-10 kpc. approximately 10 per cent of jet's energy flux is focused through a shock in the backflow of m > 3. although the shock velocities can be low enough that acceleration to high energy via dsa is still efficient, they are also high enough for the hillas energy to approach 1019-20 ev, particularly for heavier cr composition and in cases where fluid elements pass through multiple shocks. we discuss some of the more general considerations for acceleration of particles to ultrahigh energy with reference to giant-lobed radio galaxies such as centaurus a and fornax a, a class of sources which may be responsible for the observed anisotropies from uhecr observatories. | ultrahigh energy cosmic rays from shocks in the lobes of powerful radio galaxies |
over the past few decades, a consensus picture has emerged in which roughly a quarter of the universe consists of dark matter. i begin with a review of the observational evidence for the existence of dark matter: rotation curves of galaxies, gravitational lensing measurements, hot gas in clusters, galaxy formation, primordial nucleosynthesis and cosmic microwave background (cmb) observations. then, i discuss a number of anomalous signals in a variety of data sets that may point to discovery, though all of them are controversial. the annual modulation in the dama detector and/or the gamma-ray excess seen in the fermi gamma ray space telescope from the galactic center could be due to wimps; a 3.5 kev x-ray line from multiple sources could be due to sterile neutrinos; or the 511 kev line in integral data could be due to mev dark matter. all of these would require further confirmation in other experiments or data sets to be proven correct. in addition, a new line of research on dark stars is presented, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion: the observational possibility of discovering dark matter in this way is discussed. | status of dark matter in the universe |
the icecube neutrino observatory accumulated a total of 318 billion cosmic-ray-induced muon events between 2009 may and 2015 may. this data set was used for a detailed analysis of the sidereal anisotropy in the arrival directions of cosmic rays in the tev to pev energy range. the observed global sidereal anisotropy features large regions of relative excess and deficit, with amplitudes of the order of 10-3 up to about 100 tev. a decomposition of the arrival direction distribution into spherical harmonics shows that most of the power is contained in the low-multipole (ℓ ≤ 4) moments. however, higher multipole components are found to be statistically significant down to an angular scale of less than 10°, approaching the angular resolution of the detector. above 100 tev, a change in the morphology of the arrival direction distribution is observed, and the anisotropy is characterized by a wide relative deficit whose amplitude increases with primary energy up to at least 5 pev, the highest energies currently accessible to icecube. no time dependence of the large- and small-scale structures is observed in the period of six years covered by this analysis. the high-statistics data set reveals more details of the properties of the anisotropy and is potentially able to shed light on the various physical processes that are responsible for the complex angular structure and energy evolution. | anisotropy in cosmic-ray arrival directions in the southern hemisphere based on six years of data from the icecube detector |
thin synchrotron-emitting filaments are increasingly seen in the intracluster medium (icm). we present the first example of a direct interaction between a magnetic filament, a radio jet, and a dense icm clump in the poor cluster a194. this enables the first exploration of the dynamics and possible histories of magnetic fields and cosmic rays in such filaments. our observations are from the meerkat galaxy cluster legacy survey and the lofar two-meter sky survey. prominent 220 kpc long filaments extend east of radio galaxy 3c40b, with very faint extensions to 300 kpc, and show signs of interaction with its northern jet. they curve around a bend in the jet and intersect the jet in faraday depth space. the x-ray surface brightness drops across the filaments; this suggests that the relativistic particles and fields contribute significantly to the pressure balance and evacuate the thermal plasma in a ~35 kpc cylinder. we explore whether the relativistic electrons could have streamed along the filaments from 3c40b, and present a plausible alternative whereby magnetized filaments are (a) generated by shear motions in the large-scale, post-merger icm flow, (b) stretched by interactions with the jet and flows in the icm, amplifying the embedded magnetic fields, and (c) perfused by re-energized relativistic electrons through betatron-type acceleration or diffusion of turbulently accelerated icm cosmic-ray electrons. we use the faraday depth measurements to reconstruct some of the 3d structures of the filamegnts and of 3c40a and b. | intracluster magnetic filaments and an encounter with a radio jet |
the quenching 'maintenance' and 'cooling flow' problems are important from the milky way through massive cluster elliptical galaxies. previous work has shown that some source of energy beyond that from stars and pure magnetohydrodynamic processes is required, perhaps from active galactic nuclei, but even the qualitative form of this energetic input remains uncertain. different scenarios include thermal 'heating', direct wind or momentum injection, cosmic ray heating or pressure support, or turbulent 'stirring' of the intracluster medium (icm). we investigate these in 10^{12}-10^{14} m_{⊙ } haloes using high-resolution non-cosmological simulations with the fire-2 (feedback in realistic environments) stellar feedback model, including simplified toy energy injection models, where we arbitrarily vary the strength, injection scale, and physical form of the energy. we explore which scenarios can quench without violating observational constraints on energetics or icm gas. we show that turbulent stirring in the central ∼ 100 kpc, or cosmic ray injection, can both maintain a stable low-star formation rate halo for >gyr time-scales with modest energy input, by providing a non-thermal pressure that stably lowers the core density and cooling rates. in both cases, associated thermal-heating processes are negligible. turbulent stirring preserves cool-core features while mixing condensed core gas into the hotter halo and is by far the most energy efficient model. pure thermal heating or nuclear isotropic momentum injection require vastly larger energy, are less efficient in lower mass haloes, easily overheat cores, and require fine tuning to avoid driving unphysical temperature gradients or gas expulsion from the halo centre. | cosmic rays or turbulence can suppress cooling flows (where thermal heating or momentum injection fail) |
the icecube collaboration reported an ∼3.5σ excess of 13 ± 5 neutrino events in the direction of the blazar txs 0506+056 during an ∼6 month period in 2014-2015, as well as the (∼3σ) detection of a high-energy muon neutrino during an electromagnetic flare in 2017. we explore the possibility that the 2014-2015 neutrino excess and the 2017 multimessenger flare are both explained in a common physical framework that relies on the emergence of a relativistic neutral beam in the blazar jet due to interactions of accelerated cosmic rays (crs) with photons. we demonstrate that the neutral beam model provides an explanation for the 2014-2015 neutrino excess without violating x-ray and γ-ray constraints and yields results consistent with the detection of one high-energy neutrino during the 2017 flare. if both neutrino associations with txs 05065+056 are real, our model requires that (i) the composition of accelerated crs is light, with a ratio of helium nuclei to protons ≳5; (ii) a luminous external photon field (∼1046 erg s-1) variable (on yearlong timescales) is present; and (iii) the cr injection luminosity, as well as the properties of the dissipation region (i.e., lorentz factor, magnetic field, and size), vary on yearlong timescales. | a neutral beam model for high-energy neutrino emission from the blazar txs 0506+056 |
the merging of two neutron stars (mns) is thought to be the source of short gamma-ray bursts (sgrb) and gravitational wave transients, as well as the main production site of r-process elements like eu. we have derived a new delay time distribution (dtd) for mns from theoretical considerations and we have tested it against (i) the sgrb redshift distribution and (ii) the galactic evolution of eu and fe, in particular the [eu/fe] versus [fe/h] relation. for comparison, we also tested other dtds, as proposed in the literature. to address the first item, we have convolved the dtd with the cosmic star formation rate, while for the second we have employed a detailed chemical evolution model of the milky way. we have also varied the dtd of type ia sne (the main fe producers), the contribution to eu production from core-collapse sne, as well as explored the effect of a dependence on the metallicity of the occurrence probability of mns. our main results can be summarized as follows: (i) the sgrb redshift distribution can be fitted using dtds for mns that produce average time-scales of 300-500 myr; (ii) if the mns are the sole producers of the galactic eu and the occurrence probability of mns is constant the eu production time-scale must be on the order of ≲30 myr; (iii) allowing for the eu production in core-collapse sne or adopting a metallicity-dependent occurrence probability, allow us to reproduce both observational constraints, but many uncertainties are still present in both assumptions. | a new delay time distribution for merging neutron stars tested against galactic and cosmic data |
the large high altitude air shower observatory (lhaaso) is one of the most sensitive gamma-ray detector arrays currently operating at tev and pev energies. recently the lhaaso experiment detected ultra-high-energy (uhe; eγ≳100 tev ) photon emissions up to 1.4 pev from twelve astrophysical gamma-ray sources. we point out that the detection of cosmic photons at such energies can constrain the photon self-decay motivated by superluminal lorentz symmetry violation (lv) to a higher level, thus can put strong constraints to certain lv frameworks. meanwhile, we suggest that the current observation of the pev-scale photon with lhaaso may provide hints to permit a subluminal type of lorentz violation in the proximity of the planckian regime, and may be compatible with the light speed variation at the scale of 3.6 ×1017 gev recently suggested from gamma-ray burst (grb) time delays. we further propose detecting pev photons coming from extragalactic sources with future experiments, based on lv-induced threshold anomalies of e+e- pair-production, as a crucial test of subluminal lorentz violation. we comment that these observations are consistent with a d-brane/string-inspired quantum-gravity framework, the space-time foam model. | ultrahigh-energy photons from lhaaso as probes of lorentz symmetry violations |
the 21 cm brightness temperature δtb fluctuations from reionization promise to provide information on the physical processes during that epoch. we present a formalism for generating the δtb distribution using dark matter simulations and a 1d radiative transfer code. our analysis is able to account for the spin temperature ts fluctuations arising from inhomogeneous x-ray heating and lyα coupling during cosmic dawn. the δtb power spectrum amplitude at large scales (k ∼ 0.1 mpc-1) is maximum when ∼10 per cent of the gas (by volume) is heated above the cosmic microwave background temperature. the power spectrum shows a `bump'-like feature during cosmic dawn and its location measures the typical sizes of heated regions. we find that the effect of peculiar velocities on the power spectrum is negligible at large scales for most part of the reionization history. during early stages (when the volume averaged ionization fraction ≲ 0.2) this is because the signal is dominated by fluctuations in ts. for reionization models that are solely driven by stars within high-mass (≳ 109 m⊙) haloes, the peculiar velocity effects are prominent only at smaller scales (k ≳ 0.4 mpc-1) where patchiness in the neutral hydrogen density dominates the signal. the conclusions are unaffected by changes in the amplitude or steepness in the x-ray spectra of the sources. | 21 cm signal from cosmic dawn: imprints of spin temperature fluctuations and peculiar velocities |
an improved amati correlation was constructed in apj 931 (2022) 50 by us recently. in this paper, we further study constraints on the λcdm and wcdm models from the gamma-ray bursts (grbs) standardized with the standard and improved amati correlations, respectively. by using the pantheon type ia supernova sample to calibrate the latest a220 grb data set, the grb hubble diagram is obtained model-independently. we find that at the high-redshift region (z > 1.4) the grb distance modulus from the improved amati correlation is larger apparently than that from the standard amati one. the grb data from the standard amati correlation only give a lower bound limit on the present matter density parameter ωm0, while the grbs from the improved amati correlation constrain the ωm0 with the 68% confidence level to be ${0.308}_{-0.230}^{+0.066}$ and ${0.307}_{-0.290}^{+0.057}$ in the λcdm and wcdm models, respectively, which are very consistent with those given by other current popular observational data including baryon acoustic oscillation, cosmic microwave background (cmb) radiation, and so on. once the h(z) data are added in our analysis, the constraint on the hubble constant h 0 can be achieved. we find that two different correlations provide slightly different h 0 results but the marginalized mean values seem to be close to that from the planck 2018 cmb radiation observations. | gamma-ray burst constraints on cosmological models from the improved amati correlation |
due to shielding, direct detection experiments are in some cases insensitive to dark matter candidates with very large scattering cross sections with nucleons. in this paper, we revisit this class of models and derive a simple analytic criterion for conservative but robust direct detection limits. while large spin-independent cross sections seem to be ruled out, we identify potentially viable parameter space for dark matter with a spin-dependent cross section with nucleons in the range of 10-27 cm2≲σdm -p≲10-24 cm2 . with these parameters, cosmic-ray scattering with dark matter in the extended halo of the milky way could generate a novel and distinctive gamma-ray signal at high galactic latitudes. such a signal could be observable by fermi or future space-based gamma-ray telescopes. | robust constraints and novel gamma-ray signatures of dark matter that interacts strongly with nucleons |
precise measurements of the time-dependent intensity of the low-energy (<50 gev) galactic cosmic rays (gcrs) are fundamental to test and improve the models that describe their propagation inside the heliosphere. in particular, data spanning different solar activity periods, i.e., from minimum to maximum, are needed to achieve comprehensive understanding of such physical phenomena. the minimum phase between solar cycles 23 and 24 was peculiarly long, extending up to the beginning of 2010 and followed by the maximum phase, reached during early 2014. in this letter, we present proton differential spectra measured from 2010 january to 2014 february by the pamela experiment. for the first time the gcr proton intensity was studied over a wide energy range (0.08-50 gev) by a single apparatus from a minimum to a maximum period of solar activity. the large statistics allowed the time variation to be investigated on a nearly monthly basis. data were compared and interpreted in the context of a state-of-the-art three-dimensional model describing the gcrs propagation through the heliosphere. | proton fluxes measured by the pamela experiment from the minimum to the maximum solar activity for solar cycle 24 |
galactic cosmic rays (gcrs) are thought to be accelerated in strong shocks induced by massive star winds and supernova explosions sweeping across the interstellar medium. but the phase of the interstellar medium from which the crs are extracted has remained elusive until now. here, we study in detail the gcr source composition deduced from recent measurements by the ams-02, voyager 1, and supertiger experiments to obtain information on the composition, ionization state, and dust content of the gcr source reservoirs. we show that the volatile elements of the cr material are mainly accelerated from a plasma of temperature ≳ 2 mk, which is typical of the hot medium found in galactic superbubbles energized by the activity of massive star winds and supernova explosions. another gcr component, which is responsible for the overabundance of 22ne, most likely arises from acceleration of massive star winds in their termination shocks. from the cr-related gamma-ray luminosity of the milky way, we estimate that the ion acceleration efficiency in both supernova shocks and wind termination shocks is of the order of 10-5. the gcr source composition also shows evidence for a preferential acceleration of refractory elements contained in interstellar dust. we suggest that the gcr refractories are also produced in superbubbles, from shock acceleration and subsequent sputtering of dust grains continuously incorporated into the hot plasma through thermal evaporation of embedded molecular clouds. our model explains well the measured abundances of all primary and mostly primary crs from h to zr, including the overabundance of 22ne. | the origin of galactic cosmic rays as revealed by their composition |
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