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the cross section for prompt antiproton production in collisions of protons with an energy of 6.5 tev incident on helium nuclei at rest is measured with the lhcb experiment from a data set corresponding to an integrated luminosity of 0.5 nb-1. the target is provided by injecting helium gas into the lhc beam line at the lhcb interaction point. the reported results, covering antiproton momenta between 12 and 110 gev /c , represent the first direct determination of the antiproton production cross section in p -he collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments. | measurement of antiproton production in p -he collisions at √{snn }=110 gev |
the origin and composition of ultra-high-energy cosmic rays (uhecrs) remain a mystery. the proton dip model describes their spectral shape in the energy range above 109 gev by pair production and photohadronic interactions with the cosmic microwave background. the photohadronic interactions also produce cosmogenic neutrinos peaking around 109 gev. we test whether this model is still viable in light of recent uhecr spectrum measurements from the telescope array experiment and upper limits on the cosmogenic neutrino flux from icecube. while two-parameter fits have been already presented, we perform a full scan of the three main physical model parameters: source redshift evolution, injected proton maximal energy, and spectral index. we find qualitatively different conclusions compared to earlier two-parameter fits in the literature: a mild preference for a maximal energy cutoff at the sources instead of the greisen-zatsepin-kuzmin cutoff, hard injection spectra, and strong source evolution. the predicted cosmogenic neutrino flux exceeds the icecube limit for any parameter combination. as a result, the proton dip model is challenged at more than 95% c.l. this is strong evidence against this model independent of mass composition measurements. | cosmogenic neutrinos challenge the cosmic-ray proton dip model |
kascade and kascade-grande were multi-detector installations to measure individual air showers of cosmic rays at ultra-high energy. based on data sets measured by kascade and kascade-grande, 90% c.l. upper limits to the flux of gamma-rays in the primary cosmic ray flux are determined in an energy range of {10}14{--}{10}18 ev. the analysis is performed by selecting air showers with a low muon content as expected for gamma-ray-induced showers compared to air showers induced by energetic nuclei. the best upper limit of the fraction of gamma-rays to the total cosmic ray flux is obtained at 3.7× {10}15 ev with 1.1× {10}-5. translated to an absolute gamma-ray flux this sets constraints on some fundamental astrophysical models, such as the distance of sources for at least one of the icecube neutrino excess models. | kascade-grande limits on the isotropic diffuse gamma-ray flux between 100 tev and 1 eev |
the cosmic-ray flux of antiprotons is measured with high precision by the space-borne particle spectrometers ams-02. its interpretation requires a correct description of the dominant production process for antiprotons in our galaxy, namely, the interaction of cosmic-ray proton and helium with the interstellar medium. in light of new cross section measurements by the na61 experiment of p +p →p ¯+x and the first ever measurement of p +he →p ¯+x by the lhcb experiment, we update the parametrization of proton-proton and proton-nucleon cross sections. we find that the lhcb p he data constrain a shape for the cross section at high energies and show for the first time how well the rescaling from the p p channel applies to a helium target. by using p p , p he and p c data we estimate the uncertainty on the lorentz invariant cross section for p +he →p ¯+x . we use these new cross sections to compute the source term for all the production channels, considering also nuclei heavier than he both in cosmic rays and the interstellar medium. the uncertainties on the total source term are up to ±20 % and slightly increase below antiproton energies of 5 gev. this uncertainty is dominated by the p +p →p ¯+x cross section, which translates into all channels since we derive them using the p p cross sections. the cross sections to calculate the source spectra from all relevant cosmic-ray isotopes are provided in supplemental material. we finally quantify the necessity of new data on antiproton production cross sections, and pin down the kinematic parameter space which should be covered by future data. | production cross sections of cosmic antiprotons in the light of new data from the na61 and lhcb experiments |
we developed a radio interferometric technique for the observation of extensive air showers initiated by cosmic particles. in this proof-of-principle study we show that properties of extensive air showers can be derived with high accuracy in a straightforward manner. when time synchronisation below ∼1 ns between different receivers can be achieved, direction reconstruction resolution of <0 .2∘ and resolution on the depth of shower maximum of <10 g/cm2 are obtained over the full parameter range studied, with even higher accuracy for inclined incoming directions. in addition, by applying the developed method to dense arrays of radio antennas, the energy threshold for the radio detection of extensive air showers can be significantly lowered. the proposed method can be incorporated in operational and future cosmic particle observatories and with its high accuracy it has the potential to play a crucial role in unravelling the composition of the ultra-high-energy cosmic-particle flux. | radio interferometry applied to the observation of cosmic-ray induced extensive air showers |
this review covers the measurements related to the extragalactic background light (ebl) intensity from gamma-rays to radio in the electromagnetic spectrum over 20 decades in the wavelength. the cosmic microwave background (cmb) remains the best measured spectrum with an accuracy better than 1%. the measurements related to the cosmic optical background (cob), centered at 1 microns, are impacted by the large zodiacal light associated with interplanetary dust in the inner solar system. the best measurements of cob come from an indirect technique involving gamma-ray spectra of bright blazars with an absorption feature resulting from pair-production off of cob photons. the cosmic infrared background (cib) peaking at around 100 microns established an energetically important background with an intensity comparable to the optical background. this discovery paved the path for large aperture far-infrared and sub-millimeter observations resulting in the discovery of dusty, starbursting galaxies. their role in galaxy formation and evolution remains an active area of research in modern-day astrophysics. the extreme uv background remains mostly unexplored and will be a challenge to measure due to the high galactic background and absorption of extragalactic photons by the intergalactic medium at these euv/soft x-ray energies. we also summarize our understanding of the spatial anisotropies and angular power spectra of intensity fluctuations. we motivate a precise direct measurement of the cob between 0.1 to 5 microns using a small aperture telescope observing either from the outer solar system, at distances of 5 au or more, or out of the ecliptic plane. other future applications include improving our understanding of the background at tev energies and spectral distortions of cmb and cib. | extragalactic background light measurements and applications |
the extragalactic background light (ebl) can be probed via the absorption imprint it leaves in the spectra of gamma-ray sources (γ γ \to {e}-{e}+). we recently developed a dedicated technique to reconstruct the ebl, and its evolution with redshift, from γ-ray optical depth data using a large sample of blazars detected by the fermi large area telescope. here, we extend this data set to the tev regime using ground-based cherenkov observations of 38 blazars and report the first homogeneous measurement of the ebl spectral intensity covering the ultraviolet to infrared wavelengths (∼0.1-100 μm). a minimal ebl throughout the wavelength range with respect to integrated galaxy light is found, allowing little additional unresolved emission from faint or truly diffuse populations setting an upper limit of ≲4 nw m-2 sr-1 at 1.4 μm. in particular, the cosmic optical background at z = 0 is found to be {27.8}-2.0+2.1 {nw} {{{m}}}-2 {sr}}-1. this work lays the foundation for accurate gamma-ray measurements of the ebl across its whole spectral range using a combination of gev and tev data. | a gev-tev measurement of the extragalactic background light |
centrally located diffuse radio emission has been observed in both merging and non-merging galaxy clusters. depending on their morphology and size, we distinguish between giant radio haloes, which occur predominantly in merging clusters, and mini haloes, which are found in non-merging, cool-core clusters. in recent years, cluster-scale radio emission has also been observed in clusters with no sign of major mergers, showing that our knowledge of the mechanisms that lead to particle acceleration in the intra-cluster medium (icm) is still incomplete. low-frequency sensitive observations are required to assess whether the emission discovered in these few cases is common in galaxy clusters or not. with this aim, we carried out a campaign of observations with the low frequency aray (lofar) in the frequency range 120-168 mhz of nine massive clusters selected from the planck sz catalogue, which had no sign of major mergers. in this paper, we discuss the results of the observations that have led to the largest cluster sample studied within the lofar two-metre sky survey, and we present chandra x-ray data used to investigate the dynamical state of the clusters, verifying that the clusters are currently not undergoing major mergers, and to search for traces of minor or off-axis mergers. we discover large-scale steep-spectrum emission around mini haloes in the cool-core clusters psz1g139.61+24 and rxj1720.1+2638, which is not observed around the mini halo in the non-cool-core cluster a1413. we also discover a new 570 kpc-halo in the non-cool-core cluster rxcj0142.0+2131. we derived new upper limits to the radio power for clusters in which no diffuse radio emission was found, and we discuss the implication of our results to constrain the cosmic-ray energy budget in the icm. we conclude that radio emission in non-merging massive clusters is not common at the sensitivity level reached by our observations and that no clear connection with the cluster dynamical state is observed. our results might indicate that the sloshing of a dense cool core could trigger particle acceleration on larger scales and generate steep-spectrum radio emission. | a lofar study of non-merging massive galaxy clusters |
with the large progress in searches for dark matter (dm) particles with indirect and direct methods, we develop a numerical tool that enables fast calculations of the likelihoods of specified dm particle models given a number of observational data, such as charged cosmic rays from space-borne experiments (e.g., pamela, ams-02), γ-rays from the fermi space telescope, and underground direct detection experiments. the purpose of this tool - likedm, likelihood calculator for dark matter detection - is to bridge the gap between a particle model of dm and the observational data. the intermediate steps between these two, including the astrophysical backgrounds, the propagation of charged particles, the analysis of fermi γ-ray data, as well as the dm velocity distribution and the nuclear form factor, have been dealt with in the code. we release the first version (v1.0) focusing on the constraints from indirect detection of dm with charged cosmic and gamma rays. direct detection will be implemented in the next version. this manual describes the framework, usage, and related physics of the code. | likedm: likelihood calculator of dark matter detection |
the all-sky medium energy gamma-ray observatory (amego) is a probe-class mission concept that will provide essential contributions to multimessenger astrophysics in the next decade. amego operates both as a compton and pair telescope to achieve unprecedented sensitivity between 200 kev and >5 gev. the instrument consists of four subsystems. a double-sided strip silicon tracker gives a precise measure of the first compton scatter interaction and tracks of pair-conversion products. a novel cdznte low energy calorimeter with excellent position and energy resolution surrounds the bottom and sides of the tracker to detect the compton-scattered photons which enhances the polarization and narrow-line sensitivity. a thick csi high energy calorimeter contains the high-energy compton and pair events. the instrument is surrounded by a plastic anti-coincidence detector to veto the cosmic-ray background. we have performed detailed simulations to predict the telescope performance and are currently building a prototype instrument. the amego prototype, known as compair, will be tested at the high intensity gamma-ray source in 2021, followed by a balloon flight in fall of 2022. in this presentation we will give an overview of the science motivation, a description of the observatory, and an update of the prototype instrument development. | amego: exploring the extreme multimessenger universe |
in order to connect galaxy clusters to their progenitor protoclusters, we must constrain the star formation histories within their member galaxies and the timescale of virial collapse. in this paper we characterize the complex star-forming properties of a z = 2.5 protocluster in the cosmos field using alma dust continuum and new very large array co (1-0) observations of two filaments associated with the structure, sometimes referred to as the "hyperion" protocluster. we focus in particular on the protocluster "core," which has previously been suggested as the highest-redshift bona fide galaxy cluster traced by extended x-ray emission in a stacked chandra/xmm image. we reanalyze these data and refute these claims, finding that at least 40% ± 17% of extended x-ray sources of similar luminosity and size at this redshift arise instead from inverse compton scattering off recently extinguished radio galaxies rather than intracluster medium. using ancillary cosmos data, we also constrain the spectral energy distributions of the two filaments' eight constituent galaxies from the rest-frame uv to radio. we do not find evidence for enhanced star formation efficiency in the core and conclude that the constituent galaxies are already massive (m⋆ ≈ 1011 m⊙), with molecular gas reservoirs >1010 m⊙ that will be depleted within 200-400 myr. finally, we calculate the halo mass of the nested core at z = 2.5 and conclude that it will collapse into a cluster of (2-9) × 1014 m⊙, comparable to the size of the coma cluster at z = 0 and accounting for at least 50% of the total estimated halo mass of the extended "hyperion" structure. | comprehensive gas characterization of a z = 2.5 protocluster: a cluster core caught in the beginning of virialization? |
high-resolution radio observations of cluster radio relics often show complex spatial and spectral features. however, it is not clear what these features reveal about the underlying magnetic field properties. we performed three-dimensional magneto-hydrodynamical simulations of merger shock waves propagating through a magnetised, turbulent intracluster medium. our model includes the diffusive shock acceleration of cosmic-ray electrons, their spatial advection and energy losses at run-time. with this set-up we can investigate the relation between radio substructure and pre-shock plasma conditions in the host cluster. we find that upstream turbulence plays a major role in shaping the properties of radio relics produced downstream. within the assumption of diffusive shock acceleration, we can reproduce the observed discrepancy between the x-ray derived mach number of shocks, and the mach number inferred from radio spectra. our simulated spectral index maps and profiles across the radio relic also suggest that the standard deviation of the upstream magnetic field must be relatively small ($\sigma_b\leq 1 \, \mu$g) in order to reproduce observations and therefore, radio relics can potentially constrain the distribution of magnetic fields in galaxy clusters outskirts. | morphology of radio relics - i. what causes the substructure of synchrotron emission? |
cosmic rays generated by supernovae carry away a significant portion of the lifetime energy emission of their parent star, making them a plausible mechanism for heating the early universe intergalactic medium (igm). following a review of the existing literature on cosmic ray heating, we develop a flexible model of this heating mechanism for use in 3d seminumerical 21-cm signal simulations and conduct the first investigations of the signatures it imprints on the 21-cm power spectrum and tomographic maps. we find that cosmic ray heating of the igm is short-ranged, leading to heating clustered around star-forming sites, and a sharp contrast between heated regions of 21-cm emission and unheated regions of absorption. this contrast results in greater small-scale power for cosmic ray heated scenarios compared to what is found for x-ray heating, thus suggesting a way to test the nature of igm heating with future 21-cm observations. finally, we find an unexpectedly rich thermal history in models where cosmic rays can only escape efficiently from low-mass haloes, such as in scenarios where these energetic particles originate from population iii star supernovae remnants. the interplay of heating and the lyman-werner feedback in these models can produce a local peak in the igm kinetic temperature and, for a limited parameter range, a flattened absorption trough in the global 21-cm signal. | signatures of cosmic ray heating in 21-cm observables |
ultra-high-energy photons with energies exceeding $10^{17}$ ev offer a wealth of connections to different aspects of cosmic-ray astrophysics as well as to gamma-ray and neutrino astronomy. the recent observations of photons with energies in the $10^{15}$ ev range further motivate searches for even higher-energy photons. in this paper, we present a search for photons with energies exceeding $2{\times}10^{17}$ ev using about 5.5 years of hybrid data from the low-energy extensions of the pierre auger observatory. the upper limits on the integral photon flux derived here are the most stringent ones to date in the energy region between $10^{17}$ and $10^{18}$ ev. | a search for photons with energies above $2{\\times}10^{17}$ ev using hybrid data from the low-energy extensions of the pierre auger observatory |
we demonstrate that supernova remnant (snr) shocks embedded within massive star clusters can reproduce both the cosmic-ray proton and all-particle spectra measured in the vicinity of the earth up to hundreds of peta-electronvolts (pev). we model two classes of massive star clusters. the first population are 'loose clusters' that do not power a collective wind termination shock. snr shocks then expand in a low-density and weakly magnetized medium, and this population mainly contributes up to the 'knee' of the cr spectrum around 1 pev. the second population are young compact clusters, which are powerful and compact enough to sustain a collective wind outflow. snr shocks then expand from the cluster into the strongly magnetized wind and accelerate nuclei up to ultra-high energies. this population, representing only about 15 per cent of all galactic massive star clusters, nevertheless dominates the spectrum between ~1 and 100 pev. while these two components alone can reproduce the shape of the cr spectrum up to hundreds of pev, adding a light subankle extragalactic component motivated by composition and anisotropy measurements, allows to reproduce the spectrum up to the highest energies. fitting parameters are systematically linked to physical variables whose values are in line with theoretical expectations. | massive star cluster origin for the galactic cosmic ray population at very-high energies |
cosmic ray energy spectra exhibit power law distributions over many orders of magnitude that are very well described by the predictions of q-generalized statistical mechanics, based on a q-generalized hagedorn theory for transverse momentum spectra and hard qcd scattering processes. qcd at largest center of mass energies predicts the entropic index to be q =13/11 . here we show that the escort duality of the nonextensive thermodynamic formalism predicts an energy split of effective temperature given by δ k t =±1/10 k th≈±18 mev, where th is the hagedorn temperature. we carefully analyse the measured data of the ams-02 collaboration and provide evidence that the predicted temperature split is indeed observed, leading to a different energy dependence of the e+ and e- spectral indices. we also observe a distinguished energy scale e* ≈ 50 gev where the e+ and e- spectral indices differ the most. linear combinations of the escort and non-escort q-generalized canonical distributions yield excellent agreement with the measured ams-02 data in the entire energy range. | generalized statistical mechanics of cosmic rays: application to positron-electron spectral indices |
we give a brief review of the origin and acceleration of cosmic rays (crs), emphasizing the production of crs at different stages of supernova evolution by the first-order fermi shock acceleration mechanism. we suggest that supernovae with trans-relativistic outflows, despite being rather rare, may accelerate crs to energies above 10^{18} ev over the first year of their evolution. supernovae in young compact clusters of massive stars, and interaction powered superluminous supernovae, may accelerate crs well above the pev regime. we discuss the acceleration of the bulk of the galactic crs in isolated supernova remnants and re-acceleration of escaped crs by the multiple shocks present in superbubbles produced by associations of ob stars. the effects of magnetic field amplification by cr driven instabilities, as well as superdiffusive cr transport, are discussed for nonthermal radiation produced by nonlinear shocks of all speeds including trans-relativistic ones. | cosmic ray production in supernovae |
understanding the isotopic composition of cosmic rays (crs) observed near earth represents a milestone towards the identification of their origin. local fluxes contain all the known stable and long-lived isotopes, reflecting the complex history of primaries and secondaries as they traverse the interstellar medium. for that reason, a numerical code which aims at describing the cr transport in the galaxy must unavoidably rely on accurate modelling of the production of secondary particles. in this work we provide a detailed description of the nuclear cross sections and decay network as implemented in the forthcoming release of the galactic propagation code dragon2. we present the secondary production models implemented in the code and we apply the different prescriptions to compute quantities of interest to interpret local cr fluxes (e.g., nuclear fragmentation timescales, secondary and tertiary source terms). in particular, we develop a nuclear secondary production model aimed at accurately computing the light secondary fluxes (namely: li, be, b) above 1 gev/n. this result is achieved by fitting existing empirical or semi-empirical formalisms to a large sample of measurements in the energy range 100 mev/n to 100 gev/n and by considering the contribution of the most relevant decaying isotopes up to iron. concerning secondary antiparticles (positrons and antiprotons), we describe a collection of models taken from the literature, and provide a detailed quantitative comparison. | cosmic-ray propagation with dragon2: ii. nuclear interactions with the interstellar gas |
a pseudo-nambu-goldstone boson (pngb) is an attractive candidate for dark matter since the current severe limits of dark matter direct detection experiments are naturally evaded by its nature. we construct a model with pngb dark matter based on a gauged u (1)b-l symmetry, where no adhoc global symmetry is assumed. the model keeps natural suppression mechanism for the dark matter direct detection cross section. on the other hand, the pngb can decay through the new high scale suppressed operators. we show that the pngb has long enough lifetime to be a dark matter in the wide range of the parameter space of the model. the thermal relic abundance of pngb dark matter can be fit with the observed value against the constraints on the dark matter decays from the cosmic-ray observations. | pseudo-nambu-goldstone dark matter from gauged u(1)b-l symmetry |
we discuss the origin of the antihelium-3 and -4 events possibly detected by ams-02. using up-to-date semianalytical tools, we show that spallation from primary hydrogen and helium nuclei onto the ism predicts a 3he ¯ flux typically one to two orders of magnitude below the sensitivity of ams-02 after 5 years, and a 4he ¯ flux roughly 5 orders of magnitude below the ams-02 sensitivity. we argue that dark matter annihilations face similar difficulties in explaining this event. we then entertain the possibility that these events originate from antimatter-dominated regions in the form of anticlouds or antistars. in the case of anticlouds, we show how the isotopic ratio of antihelium nuclei might suggest that bbn has happened in an inhomogeneous manner, resulting in antiregions with a antibaryon-to-photon ratio η ¯ ≃10-3η . we discuss properties of these regions, as well as relevant constraints on the presence of anticlouds in our galaxy. we present constraints from the survival of anticlouds in the milky-way and in the early universe, as well as from cmb, gamma-ray and cosmic-ray observations. in particular, these require the anticlouds to be almost free of normal matter. we also discuss an alternative where antidomains are dominated by surviving antistars. we suggest that part of the unidentified sources in the 3fgl catalog can originate from anticlouds or antistars. ams-02 and gaps data could further probe this scenario. | where do the ams-02 antihelium events come from? |
we present solarprop, a tool to compute the influence of charge-sign dependent solar modulation for cosmic ray spectra. solarprop is able to use the output of popular tools like galprop or dragon and offers the possibility to embed new models for solar modulation. we present some examples for proton, antiproton and positron fluxes in the light of the recent pamela and ams-02 data. | solarprop: charge-sign dependent solar modulation for everyone |
we argue that ultrahigh-energy cosmic-ray collisions in earth's atmosphere can probe the strange quark density of the nucleon. these collisions have center-of-mass energies ≳1 04.6a gev , where a ≥14 is the nuclear baryon number. we hypothesize the formation of a deconfined thermal fireball which undergoes a sudden hadronization. at production the fireball has a very high matter density and consists of gluons and two flavors of light quarks (u , d ). because the fireball is formed in the baryon-rich projectile fragmentation region, the high baryochemical potential damps the production of u u ¯ and d d ¯ pairs, resulting in gluon fragmentation mainly into s s ¯. the strange quarks then become much more abundant and upon hadronization the relative density of strange hadrons is significantly enhanced over that resulting from a hadron gas. assuming the momentum distribution functions can be approximated by fermi-dirac and bose-einstein statistics, we estimate a kaon-to-pion ratio of about 3 and expect a similar (total) baryon-to-pion ratio. we show that, if this were the case, the excess of strange hadrons would suppress the fraction of energy which is transferred to decaying π0's by about 20%, yielding an ∼40 % enhancement of the muon content in atmospheric cascades, in agreement with recent data reported by the pierre auger collaboration. | strange fireball as an explanation of the muon excess in auger data |
we report the fermi large area telescope detection of extended γ-ray emission from the lobes of the radio galaxy fornax a using 6.1 years of pass 8 data. after centaurus a, this is now the second example of an extended γ-ray source attributed to a radio galaxy. both an extended flat disk morphology and a morphology following the extended radio lobes were preferred over a point-source description, and the core contribution was constrained to be < 14% of the total γ-ray flux. a preferred alignment of the γ-ray elongation with the radio lobes was demonstrated by rotating the radio lobes template. we found no significant evidence for variability on ∼0.5 year timescales. taken together, these results strongly suggest a lobe origin for the γ-rays. with the extended nature of the > 100 mev γ-ray emission established, we model the source broadband emission considering currently available total lobe radio and millimeter flux measurements, as well as x-ray detections attributed to inverse compton (ic) emission off the cosmic microwave background (cmb). unlike the centaurus a case, we find that a leptonic model involving ic scattering of cmb and extragalactic background light (ebl) photons underpredicts the γ-ray fluxes by factors of about ∼2-3, depending on the ebl model adopted. an additional γ-ray spectral component is thus required, and could be due to hadronic emission arising from proton-proton collisions of cosmic rays with thermal plasma within the radio lobes. | fermi large area telescope detection of extended gamma-ray emission from the radio galaxy fornax a |
the radio technique is a promising method for detection of cosmic-ray air showers of energies around 100pev and higher with an array of radio antennas. since the amplitude of the radio signal can be measured absolutely and increases with the shower energy, radio measurements can be used to determine the air-shower energy on an absolute scale. we show that calibrated measurements of radio detectors operated in coincidence with host experiments measuring air showers based on other techniques can be used for comparing the energy scales of these host experiments. using two approaches, first via direct amplitude measurements, and second via comparison of measurements with air shower simulations, we compare the energy scales of the air-shower experiments tunka-133 and kascade-grande, using their radio extensions, tunka-rex and lopes, respectively. due to the consistent amplitude calibration for tunka-rex and lopes achieved by using the same reference source, this comparison reaches an accuracy of approximately 10% - limited by some shortcomings of lopes, which was a prototype experiment for the digital radio technique for air showers. in particular we show that the energy scales of cosmic-ray measurements by the independently calibrated experiments kascade-grande and tunka-133 are consistent with each other on this level. | a comparison of the cosmic-ray energy scales of tunka-133 and kascade-grande via their radio extensions tunka-rex and lopes |
this paper summarizes the results obtained by the team "heliosheath processes and the structure of the heliopause: modeling energetic particles, cosmic rays, and magnetic fields" supported by the international space science institute (issi) in bern, switzerland. we focus on the physical processes occurring in the outer heliosphere, especially at its boundary called the heliopause, and in the local interstellar medium. the importance of magnetic field, charge exchange between neutral atoms and ions, and solar cycle on the heliopause topology and observed heliocentric distances to different heliospheric discontinuities are discussed. it is shown that time-dependent, data-driven boundary conditions are necessary to describe the heliospheric asymmetries detected by the voyager spacecraft. we also discuss the structure of the heliopause, especially due to its instability and magnetic reconnection. it is demonstrated that the rayleigh-taylor instability of the nose of the heliopause creates consecutive layers of the interstellar and heliospheric plasma which are magnetically connected to different sources. this may be a possible explanation of abrupt changes in the galactic and anomalous cosmic ray fluxes observed by voyager 1 when it was crossing the heliopause structure for a period of about one month in the summer of 2012. this paper also discusses the plausibility of fitting simulation results to a number of observational data sets obtained by in situ and remote measurements. the distribution of magnetic field in the vicinity of the heliopause is discussed in the context of voyager measurements. it is argued that a classical heliospheric current sheet formed due to the sun's rotation is not observed by in situ measurements and should not be expected to exist in numerical simulations extending to the boundary of the heliosphere. furthermore, we discuss the transport of energetic particles in the inner and outer heliosheath, concentrating on the anisotropic spatial diffusion diffusion tensor and the pitch-angle dependence of perpendicular diffusion and demonstrate that the latter can explain the observed pitch-angle anisotropies of both the anomalous and galactic cosmic rays in the outer heliosheath. | heliosheath processes and the structure of the heliopause: modeling energetic particles, cosmic rays, and magnetic fields |
we develop a detailed chemical network relevant to calculate the conditions that are characteristic of prestellar core collapse. we solve the system of time-dependent differential equations to calculate the equilibrium abundances of molecules and dust grains, with a size distribution given by size-bins for these latter. these abundances are used to compute the different non-ideal magneto-hydrodynamics resistivities (ambipolar, ohmic and hall), needed to carry out simulations of protostellar collapse. for the first time in this context, we take into account the evaporation of the grains, the thermal ionisation of potassium, sodium, and hydrogen at high temperature, and the thermionic emission of grains in the chemical network, and we explore the impact of various cosmic ray ionisation rates. all these processes significantly affect the non-ideal magneto-hydrodynamics resistivities, which will modify the dynamics of the collapse. ambipolar diffusion and hall effect dominate at low densities, up to nh = 1012 cm-3, after which ohmic diffusion takes over. we find that the time-scale needed to reach chemical equilibrium is always shorter than the typical dynamical (free fall) one. this allows us to build a large, multi-dimensional multi-species equilibrium abundance table over a large temperature, density and ionisation rate ranges. this table, which we make accessible to the community, is used during first and second prestellar core collapse calculations to compute the non-ideal magneto-hydrodynamics resistivities, yielding a consistent dynamical-chemical description of this process. the multi-dimensional multi-species equilibrium abundance table and a copy of the code are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/592/a18 | chemical solver to compute molecule and grain abundances and non-ideal mhd resistivities in prestellar core-collapse calculations |
context. under cold conditions in dense cores, gas-phase molecules and atoms are depleted from the gas-phase to the surface of interstellar grains. considering the time scales and physical conditions within these cores, a portion of these molecules has to be brought back into the gas-phase to explain their observation by milimeter telescopes.aims: we tested the respective efficiencies of the different mechanisms commonly included in the models (photo-desorption, chemical desorption, and cosmic-ray-induced whole-grain heating). we also tested the addition of sputtering of ice grain mantles via a collision with cosmic rays in the electronic stopping power regime, leading to a localized thermal spike desorption that was measured in the laboratory.methods: the ice sputtering induced by cosmic rays has been added to the nautilus gas-grain model while the other processes were already present. each of these processes were tested on a 1d physical structure determined by observations in tmc1 cold cores. we focused the discussion on the main ice components, simple molecules usually observed in cold cores (co, cn, cs, so, hcn, hc3n, and hco+), and complex organic molecules (coms such as ch3oh, ch3cho, ch3och3, and hcooch3). the resulting 1d chemical structure was also compared to methanol gas-phase abundances observed in these cores.results: we found that all species are not sensitive in the same way to the non-thermal desorption mechanisms, and the sensitivity also depends on the physical conditions. thus, it is mandatory to include all of them. chemical desorption seems to be essential in reproducing the observations for h densities smaller than 4 × 104 cm−3, whereas sputtering is essential above this density. the models are, however, systematically below the observed methanol abundances. a more efficient chemical desorption and a more efficient sputtering could better reproduce the observations.conclusions: in conclusion, the sputtering of ices by cosmic-rays collisions may be the most efficient desorption mechanism at high density (a few 104 cm−3 under the conditions studied here) in cold cores, whereas chemical desorption is still required at smaller densities. additional works are needed on both mechanisms to assess their efficiency with respect to the main ice composition. | efficiency of non-thermal desorptions in cold-core conditions. testing the sputtering of grain mantles induced by cosmic rays |
we present three-dimensional astrochemical simulations and synthetic observations of magnetized, turbulent, self-gravitating molecular clouds. we explore various galactic interstellar medium environments, including cosmic ray ionization rates in the range of ζcr = 10-17- $10^{-14}\, {\rm s}^{-1}$ , far-uv intensities in the range of g0 = 1-103 and metallicities in the range of z = 0.1- $2\, {\rm z}_{\odot }$ . the simulations also probe a range of densities and levels of turbulence, including cases where the gas has undergone recent compression due to cloud-cloud collisions. we examine: (i) the column densities of carbon species across the cycle of c ii, c i, and co, along with o i, in relation to the h i-to-h2 transition; (ii) the velocity-integrated emission of [c ii] 158 μm, [13c ii] 158 μm, [c i] 609 μm and 370 μm, [o i] 63 μm and 146 μm, and of the first ten 12co rotational transitions; (iii) the corresponding spectral line energy distributions; (iv) the usage of [c ii] and [o i] 63 μm to describe the dynamical state of the clouds; (v) the behaviour of the most commonly used ratios between transitions of co and [c i]; and (vi) the conversion factors for using co and c i as h2-gas tracers. we find that enhanced cosmic ray energy densities enhance all aforementioned line intensities. at low metallicities, the emission of [c ii] is well connected with the h2 column, making it a promising new h2 tracer in metal-poor environments. the conversion factors of xco and xc i depend on metallicity and the cosmic ray ionization rate, but not on fuv intensity. in the era of alma, sofia, and the forthcoming ccat-prime telescope, our results can be used to understand better the behaviour of systems in a wide range of galactic and extragalactic environments. | photodissociation region diagnostics across galactic environments |
hot jupiters provide valuable natural laboratories for studying potential contributions of high-energy radiation to pre-biotic synthesis in the atmospheres of exoplanets. in this fourth paper of the multiwavelength observations of an evaporating exoplanet and its star (moves) programme, we study the effect of different types of high-energy radiation on the production of organic and pre-biotic molecules in the atmosphere of the hot jupiter hd 189733b. our model combines x-ray and uv observations from the moves programme and 3d climate simulations from the 3d met office unified model to simulate the atmospheric composition and kinetic chemistry with the stand2019 network. also, the effects of galactic cosmic rays and stellar energetic particles are included. we find that the differences in the radiation field between the irradiated dayside and the shadowed nightside lead to stronger changes in the chemical abundances than the variability of the host star's xuv emission. we identify ammonium (nh4+) and oxonium (h3o+) as fingerprint ions for the ionization of the atmosphere by both galactic cosmic rays and stellar particles. all considered types of high-energy radiation have an enhancing effect on the abundance of key organic molecules such as hydrogen cyanide (hcn), formaldehyde (ch2o), and ethylene (c2h4). the latter two are intermediates in the production pathway of the amino acid glycine (c2h5no2) and abundant enough to be potentially detectable by jwst. | moves - iv. modelling the influence of stellar xuv-flux, cosmic rays, and stellar energetic particles on the atmospheric composition of the hot jupiter hd 189733b |
we consider a cosmological scenario in which the very early universe experienced a transient epoch of matter domination due to the formation of a large population of primordial black holes (pbhs) with masses m ≲ 109 g, that evaporate before big bang nucleosynthesis. in this context, hawking radiation would be a non-thermal mechanism to produce a cosmic background of axion-like particles (alps). we assume the minimal scenario in which these alps couple only with photons. in the case of ultralight alps (ma ≲ 10-9 ev) the cosmic magnetic fields might trigger alp-photon conversions, while for masses ma ≳ 10 ev spontaneous alp decay in photon pairs would be effective. we investigate the impact of these mechanisms on the cosmic x-ray background, on the excess in x-ray luminosity in galaxy clusters, and on the process of cosmic reionization. | axion-like particles from primordial black holes shining through the universe |
helmod is a monte carlo code developed to describe the transport of galactic cosmic rays (gcrs) through the heliosphere from the interstellar space to the earth. in the current helmod version 4 the modulation process, based on parker's equation, is applied to the propagation of gcrs in the inner and outer heliosphere, i.e., including the heliosheath. helmod was proved to reproduce protons, nuclei and electrons cosmic rays spectra observed during solar cycles 23-24 by several detectors, for instance, pamela, bess and ams-02. in particular, the unprecedented accuracy of ams-02 observations allowed one a better tuning of the description regarding the solar modulation mechanisms implemented in helmod. in addition, helmod demonstrated to be capable of reproducing the fluxes observed by the voyager probes in the inner and outer regions of heliosphere up to its border. | the helmod model in the works for inner and outer heliosphere: from ams to voyager probes observations |
we propose that the inner engine of a type i binary-driven hypernova (bdhn) is composed of kerr black hole (bh) in a non-stationary state, embedded in a uniform magnetic field b 0 aligned with the bh rotation axis and surrounded by an ionized plasma of extremely low density of 10-14 g cm-3. using grb 130427a as a prototype, we show that this inner engine acts in a sequence of elementary impulses. electrons accelerate to ultrarelativistic energy near the bh horizon, propagating along the polar axis, θ = 0, where they can reach energies of ∼1018 ev, partially contributing to ultrahigh-energy cosmic rays. when propagating with θ \ne 0 through the magnetic field b 0, they produce gev and tev radiation through synchroton emission. the mass of bh, m = 2.31m ⊙, its spin, α = 0.47, and the value of magnetic field b 0 = 3.48 × 1010 g, are determined self consistently to fulfill the energetic and the transparency requirement. the repetition time of each elementary impulse of energy { \mathcal e }∼ {10}37 erg is ∼10-14 s at the beginning of the process, then slowly increases with time evolution. in principle, this “inner engine” can operate in a gamma-ray burst (grb) for thousands of years. by scaling the bh mass and the magnetic field, the same inner engine can describe active galactic nuclei. | on the gev emission of the type i bdhn grb 130427a |
the kilometer square array (km2a) of the large high altitude air shower observatory (lhaaso) aims at surveying the northern γ -ray sky at energies above 10 tev with unprecedented sensitivity. γ -ray observations have long been one of the most powerful tools for dark matter searches, as, e.g., high-energy γ rays could be produced by the decays of heavy dark matter particles. in this letter, we present the first dark matter analysis with lhaaso-km2a, using the first 340 days of data from 1 /2 -km2a and 230 days of data from 3 /4 -km2a. several regions of interest are used to search for a signal and account for the residual cosmic-ray background after γ /hadron separation. we find no excess of dark matter signals, and thus place some of the strongest γ -ray constraints on the lifetime of heavy dark matter particles with mass between 105 and 109 gev . our results with lhaaso are robust, and have important implications for dark matter interpretations of the diffuse astrophysical high-energy neutrino emission. | constraints on heavy decaying dark matter from 570 days of lhaaso observations |
one of the curious observations from the voyagers is that the intensity of anomalous cosmic rays (acrs) did not peak at the heliospheric termination shock (hts) but instead a short distance (within ∼1 au) downstream of the hts. one possible explanation is that the interaction of the wavy heliospheric current sheet with the hts enhances magnetic reconnection and generates numerous small-scale magnetic flux ropes in the heliosheath immediately downstream of the hts. charged particles are accelerated in this region due to fermi acceleration and the reconnection electric field. in this work, we provide observational evidence of the presence of magnetic flux ropes in the heliosheath region just downstream of the hts using a wavelet analysis of the reduced magnetic helicity and grad-shafranov reconstruction techniques. the zank et al. kinetic transport theory for particles propagating through the magnetic islands region is employed to fit the observed energetic proton intensities in the post-hts region. our modeling results agree reasonably well with the observations, which suggests that stochastic acceleration via reconnection processes can explain the acr proton peak beyond the hts. | acr proton acceleration associated with reconnection processes beyond the heliospheric termination shock |
currently time-domain astronomy can scan the entire sky on a daily basis, discovering thousands of interesting transients every night. classifying the ever-increasing number of new transients is one of the main challenges for the astronomical community. one solution that addresses this issue is the robotically controlled spectral energy distribution machine (sedm) which supports the zwicky transient facility (ztf). sedm with its pipeline pysedm demonstrates that real-time robotic spectroscopic classification is feasible. in an effort to improve the quality of the current sedm data, we present here two new modules, byecr and contsep. the first removes contamination from cosmic rays, and the second removes contamination from non-target light. these new modules are part of the automated pysedm pipeline and fully integrated with the whole process. employing byecr and contsep modules together automatically extracts more spectra than the current pysedm pipeline. using snid classification results, the new modules show an improvement in the classification rate and accuracy of 2.8% and 1.7%, respectively, while the strength of the cross-correlation remains the same. improvements to the sedm astrometry would further boost the improvement of the contsep module. this kind of robotic follow-up with a fully automated pipeline has the potential to provide the spectroscopic classifications for the transients discovered by ztf and also by the rubin observatory's legacy survey of space and time. | new modules for the sedmachine to remove contaminations from cosmic rays and non-target light: byecr and contsep |
recently the dark matter particle explorer (dampe) has reported an excess in the electron-positron flux of the cosmic rays which is interpreted as a dark matter particle with the mass about 1.5 tev. we come up with a leptophilic z' scenario including a dirac fermion dark matter candidate which beside explaining the observed dampe excess, is able to pass various experimental/observational constraints including the relic density value from the wmap/planck, the invisible higgs decay bound at the lhc, the lep bounds in electron-positron scattering, the muon anomalous magnetic moment constraint, fermi-lat data, and finally the direct detection experiment limits from the xenon1t/lux. by computing the electron-positron flux produced from a dark matter with the mass about 1.5 tev we show that the model predicts the peak observed by the dampe. | dampe electron-positron excess in leptophilic z' model |
mini-euso (multiwavelength imaging new instrument for the extreme universe space observatory) is a telescope observing the earth from the international space station since 2019. the instrument employs a fresnel-lens optical system and a focal surface composed of 36 multi-anode photomultiplier tubes, 64 channels each, for a total of 2304 channels with single photon counting sensitivity. mini-euso also contains two ancillary cameras to complement measurements in the near infrared and visible ranges. the scientific objectives of the mission range from the search for extensive air showers generated by ultra-high energy cosmic rays (uhecrs) with energies above 10$^{21}$ ev, the search for nuclearites and strange quark matter (sqm), up to the study of atmospheric phenomena such as transient luminous events (tles), meteors and meteoroids. mini-euso can map the night-time earth in the near uv range (between 290-430 nm) with a spatial resolution of about 6.3 km (full field of view of 44°) and a maximum temporal resolution of 2.5 $\mu$s, observing our planet through a nadir-facing uv-transparent window in the russian zvezda module. the detector saves triggered transient phenomena with a sampling rate of 2.5 $\mu$s and 320 $\mu$s, as well as continuous acquisition at 40.96 ms scale. in this paper we discuss the detector response and the flat-fielding and calibration procedures. using the 40.96 ms data, we present $\simeq$6.3 km resolution night-time earth maps in the uv band, and report on various emissions of anthropogenic and natural origin. we measure ionospheric airglow emissions of dark moonless nights over the sea and ground, studying the effect of clouds, moonlight, and artificial (towns, boats) lights. in addition to paving the way forward for the study of long-term variations of natural and artificial light, we also estimate the observation live-time of future uhecr detectors. | observation of night-time emissions of the earth in the near uv range from the international space station with the mini-euso detector |
data from the voyager probes have provided us with the first measurement of cosmic ray intensities at mev energies, an energy range that had previously not been explored. simple extrapolations of models that fit data at gev energies, e.g., from ams-02, however, fail to reproduce the voyager data in that the predicted intensities are too high. oftentimes, this discrepancy is addressed by adding a break to the source spectrum or the diffusion coefficient in an ad hoc fashion, with a convincing physical explanation yet to be provided. here, we argue that the discrete nature of cosmic ray sources, which is usually ignored, is instead a more likely explanation. we model the distribution of intensities expected from a statistical model of discrete sources and show that its expectation value is not representative but has a spectral shape different from that for a typical configuration of sources. the voyager proton and electron data are however compatible with the median of the intensity distribution. | stochastic fluctuations of low-energy cosmic rays and the interpretation of voyager data |
alfvénic component of mhd turbulence damps alfvénic waves. the consequences of this effect are important for many processes, from cosmic ray (cr) propagation to launching outflows and winds in galaxies and other magnetized systems. we discuss the differences in the damping of the streaming instability by turbulence and the damping of a plane parallel wave. the former takes place in the system of reference aligned with the local direction of magnetic field along which crs stream. the latter is in the reference frame of the mean magnetic field and traditionally considered in plasma studies. we also compare the turbulent damping of streaming instability with ion-neutral collisional damping, which becomes the dominant damping effect at a sufficiently low ionization fraction. numerical testing and astrophysical implications are also discussed. | damping of alfvén waves in mhd turbulence and implications for cosmic ray streaming instability and galactic winds |
we measure a large set of observables in inclusive charged current muon neutrino scattering on argon with the microboone liquid argon time projection chamber operating at fermilab. we evaluate three neutrino interaction models based on the widely used genie event generator using these observables. the measurement uses a data set consisting of neutrino interactions with a final state muon candidate fully contained within the microboone detector. these data were collected in 2016 with the fermilab booster neutrino beam, which has an average neutrino energy of 800 mev , using an exposure corresponding to 5.0 ×1019 protons-on-target. the analysis employs fully automatic event selection and charged particle track reconstruction and uses a data-driven technique to separate neutrino interactions from cosmic ray background events. we find that genie models consistently describe the shapes of a large number of kinematic distributions for fixed observed multiplicity. | comparison of {\\varvec{ν }}_{\\varvec{μ }}-ar multiplicity distributions observed by microboone to genie model predictions |
thermal relic dark matter below $\sim 10 \ \text{gev}$ is excluded by cosmic microwave background data if its annihilation to visible particles is unsuppressed near the epoch of recombination. usual model-building measures to avoid this bound involve kinematically suppressing the annihilation rate in the low-velocity limit, thereby yielding dim prospects for indirect detection signatures at late times. in this work, we investigate a class of cosmologically-viable sub-gev thermal relics with late-time annihilation rates that are detectable with existing and proposed telescopes across a wide range of parameter space. we study a representative model of inelastic dark matter featuring a stable state $\chi_1$ and a slightly heavier excited state $\chi_2$ whose abundance is thermally depleted before recombination. since the kinetic energy of dark matter in the milky way is much larger than it is during recombination, $\chi_1 \chi_1 \to \chi_2 \chi_2$ upscattering can efficiently regenerate a cosmologically long-lived galactic population of $\chi_2$, whose subsequent coannihilations with $\chi_1$ give rise to observable gamma-rays in the $\sim 1 \ \text{mev} - 100 \ \text{mev}$ energy range. we find that proposed mev gamma-ray telescopes, such as e-astrogam, amego, and mast, would be sensitive to much of the thermal relic parameter space in this class of models and thereby enable both discovery and model discrimination in the event of a signal at accelerator or direct detection experiments. | reviving mev-gev indirect detection with inelastic dark matter |
acceleration of hadrons in relativistic shocks has been long expected and invoked to model grb high-energy photon and neutrino emissions. however, so far there has been no direct observational evidence of hadronic emission from grbs. the b.o.a.t. ("brightest of all time") gamma-ray burst (grb) 221009a had extreme energies (with an isotropic energy exceeding $10^{55}$ erg) and was detected in broad-band including the very-high-energy (vhe, $>100\,\rm gev$) band up to $>10$ tev. here we perform a comprehensive spectral analysis of the grb from kev to tev energy range and perform detailed spectral and light curve modelings considering both the traditional synchrotron self-compton process and the electromagnetic (em) cascade process initiated by hadronic interactions by accelerated cosmic rays in the external shock. we find that the leptonic scenario alone is not adequate to account for the observations, whereas the proposed scenario with the combination of hadronic and leptonic components can well reproduce the multi-wavelength spectra and the light curve. this result reveals the existence of the accelerated hadronic component in the early afterglow of this extreme burst. according to this scenario, the observed tev light curve should contain imprints of the prompt mev emission. | evidence of hadronic emission from the brightest-of-all-time grb 221009a |
an updated yield function for a standard nm64 neutron monitor (nm) is computed and extended to different atmospheric depths from sea level to 500 g/cm2 (∼5.7 km altitude) and is presented as lookup tables and a full parametrization. the yield function was validated using the cosmic ray spectra directly measured in space by the ams-02 experiment during the period may 2011 through may 2017 and confronted with count rates of all nm64-type nms being in operation during this period. using this approach, stability of all the selected nms was analyzed for the period 2011-2017. most of nms appear very stable and suitable for studies of long-term solar modulation of cosmic rays. however, some nms suffer from instabilities like trends, apparent jumps, or strong seasonal waves in the count rates. | updated neutron-monitor yield function: bridging between in situ and ground-based cosmic ray measurements |
cosmic rays are an important tool to study dark matter (dm) annihilation in our galaxy. recently, a possible hint for dark matter annihilation was found in the antiproton spectrum measured by ams-02, even though the result might be affected by theoretical uncertainties. a complementary way to test its dark matter interpretation would be the observation of low-energy antinuclei in cosmic rays. we determine the chances to observe antideuterons with gaps and ams-02 and the implications for the ongoing ams-02 antihelium searches. we find that the corresponding antideuteron signal is within the gaps and ams-02 detection potential. if, more conservatively, the putative signal was considered as an upper limit on dm annihilation, our results would indicate the highest possible fluxes for antideuterons and antihelium compatible with current antiproton data. | prospects to verify a possible dark matter hint in cosmic antiprotons with antideuterons and antihelium |
we have previously calculated the intergalactic background light (ibl) as a function of redshift from the lyman limit in the far-ultraviolet to a wavelength of 5 μm in the near-infrared range, based purely on data from deep galaxy surveys. here, we use similar methods to determine the mid- and far-infrared ibl from 5 to 850 μm. our approach enables us to constrain the range of photon densities by determining the uncertainties in observationally determined luminosity densities and spectral gradients. by also including the effect of the 2.7 k cosmic background photons, we determine upper and lower limits on the opacity of the universe to γ-rays up to pev energies within a 68% confidence band. our direct results on the ibl are consistent with those from complimentary γ-ray analyses using observations from the fermi γ-ray space telescope and the h.e.s.s. air čerenkov telescope. thus, we find no evidence of previously suggested processes for the modification of γ-ray spectra other than that of absorption by pair production alone. | an empirical determination of the intergalactic background light from uv to fir wavelengths using fir deep galaxy surveys and the gamma-ray opacity of the universe |
in stark contrast to their laboratory and terrestrial counterparts, cosmic jets appear to be very stable. they are able to penetrate vast spaces, which exceed by up to a billion times the size of their central engines. we propose that the reason behind this remarkable property is the loss of causal connectivity across these jets, caused by their rapid expansion in response to fast decline of external pressure with the distance from the `jet engine'. in atmospheres with power-law pressure distribution, pext ∝ z-κ, the total loss of causal connectivity occurs, when κ > 2 - the steepness which is expected to be quite common for many astrophysical environments. this conclusion does not seem to depend on the physical nature of jets - it applies both to relativistic and non-relativistic flows, both magnetically dominated and unmagnetized jets. in order to verify it, we have carried out numerical simulations of moderately magnetized and moderately relativistic jets. the results give strong support to our hypothesis and provide with valuable insights. in particular, we find that the z-pinched inner cores of magnetic jets expand slower than their envelopes and become susceptible to instabilities even when the whole jet is stable. this may result in local dissipation and emission without global disintegration of the flow. cosmic jets may become globally unstable when they enter flat sections of external atmospheres. we propose that the fanaroff-riley (fr) morphological division of extragalactic radio sources into two classes is related to this issue. in particular, we argue that the low power fr-i jets become reconfined, causally connected and globally unstable on the scale of galactic x-ray coronas, whereas more powerful fr-ii jets reconfine much further out, already on the scale of radio lobes and remain largely intact until they terminate at hotspots. using this idea, we derived the relationship between the critical jet power and the optical luminosity of the host galaxy, which is in a very good agreement with the observations. | causality and stability of cosmic jets |
we present constraints on both the kinetic temperature of the intergalactic medium (igm) at z = 8.4, and on models for heating the igm at high-redshift with x-ray emission from the first collapsed objects. these constraints are derived using a semi-analytic method to explore the new measurements of the 21 cm power spectrum from the donald c. backer precision array for probing the epoch of reionization (paper), which were presented in a companion paper, ali et al. twenty-one cm power spectra with amplitudes of hundreds of mk2 can be generically produced if the kinetic temperature of the igm is significantly below the temperature of the cosmic microwave background (cmb); as such, the new results from paper place lower limits on the igm temperature at z = 8.4. allowing for the unknown ionization state of the igm, our measurements find the igm temperature to be above ≈5 k for neutral fractions between 10% and 85%, above ≈7 k for neutral fractions between 15% and 80%, or above ≈10 k for neutral fractions between 30% and 70%. we also calculate the heating of the igm that would be provided by the observed high redshift galaxy population, and find that for most models, these galaxies are sufficient to bring the igm temperature above our lower limits. however, there are significant ranges of parameter space that could produce a signal ruled out by the paper measurements; models with a steep drop-off in the star formation rate density at high redshifts or with relatively low values for the x-ray to star formation rate efficiency of high redshift galaxies are generally disfavored. the paper measurements are consistent with (but do not constrain) a hydrogen spin temperature above the cmb temperature, a situation which we find to be generally predicted if galaxies fainter than the current detection limits of optical/nir surveys are included in calculations of x-ray heating. | paper-64 constraints on reionization. ii. the temperature of the z =8.4 intergalactic medium |
we present a new constraint on the hubble constant $h_0$ using the latest measurements of the electromagnetic counterpart to the gravitational wave (gw) event gw170817. we use the latest optical, x-ray and radio observations of the afterglow up to $\sim 3.5$ years after the gw detection, and properly take into account the impact of the host galaxy peculiar velocity. we find $75.46^{+5.34}_{-5.39}$ km s$^{-1}$ mpc$^{-1}$ (68\% credible interval), a $\sim7\%$ precision measurement, which is a significant improvement compared to the $14\%$ precision of the first standard siren measurement. our result is consistent within $1\sigma$ with the cepheid-anchored supernova and within $1.5 \sigma$ with the cosmic microwave background measurements of the hubble constant. we also explore the impact of the various assumptions made when fitting for the afterglow on the hubble constant estimate. | a standard siren measurement of the hubble constant using gw170817 and the latest observations of the electromagnetic counterpart afterglow |
whether it is at the fabrication stage or during the course of the quantum computation, e.g. because of high-energy events like cosmic rays, the qubits constituting an error correcting code may be rendered inoperable. such defects may correspond to individual qubits or to clusters and could potentially disrupt the code sufficiently to generate logical errors. in this paper, we explore a novel adaptive approach for surface code quantum error correction on a defective lattice. we show that combining an appropriate defect detection algorithm and a quarantine of the identified zone allows one to preserve the advantage of quantum error correction at finite code sizes, at the cost of a qubit overhead that scales with the size of the defect. our numerics indicate that the code's threshold need not be significantly affected; for example, for a certain scenario where small defects repeatedly arise in each logical qubit, the noise threshold is 2.7% (versus the defect-free case of 2.9%). these results pave the way to the experimental implementation of large-scale quantum computers where defects will be inevitable. | adaptive surface code for quantum error correction in the presence of temporary or permanent defects |
the icecube project transformed a cubic kilometer of transparent, natural antarctic ice into a cherenkov detector. it discovered neutrinos of tev-pev energy originating beyond our galaxy with an energy flux that exceeds the one of high-energy gamma rays of extragalactic origin. unlike at any other wavelength of light, extragalactic neutrinos outshine the nearby sources in our own milky way. updated measurements of the diffuse cosmic neutrino flux indicate that the high-energy gamma rays produced by the neutral pions that accompany cosmic neutrinos lose energy in the sources and are likely to be observed at mev energy, or below. after the reanalysis of 10 years of archival data with an improved data selection and enhanced data analysis methods, the active galaxy ngc 1068 emerged as the hottest spot in the neutrino sky map. it is also the most significant source in a search at the positions of 110 preselected high-energy gamma-ray sources. additionally, we find evidence for neutrino emission from the active galaxies pks 1424+240 and txs 0506+056. txs 0506+056 had already been identified as a neutrino source in a multimessenger campaign triggered by a neutrino of 290 tev energy and, by the independent observation of a neutrino burst in 2014 from this source in archival icecube data. the observations point to active galaxies as the sources of cosmic neutrinos, and cosmic rays, with the gamma-ray-obscured dense cores near the supermassive black holes at their center as the sites where neutrinos originate, typically within $10\sim100$ schwarzschild radii. | icecube: neutrinos from active galaxies |
we present a bayesian and frequentist analysis of the dampe charged cosmic ray spectrum. the spectrum, by eye, contained a spectral break at about 1tev and a monochromatic excess at about 1.4tev. the break was supported by a bayes factor of about 1010 and we argue that the statistical significance was resounding. we investigated whether we should attribute the excess to dark matter annihilation into electrons in a nearby subhalo. we found a local significance of about 3.6σ and a global significance of about 2.3σ, including a two-dimensional look-elsewhere effect by simulating 1000 pseudo-experiments. the bayes factor was sensitive to our choices of priors, but favoured the excess by about 2 for our choices. thus, whilst intriguing, the evidence for a signal is not currently compelling. | dampe squib? significance of the 1.4 tev dampe excess |
we present a new model of anisotropic cosmic ray propagation in the milky way, where cosmic rays are injected at discrete transient sources in the disc and propagated in the galactic magnetic field. in the framework of our model, we show that the cosmic ray spectrum is time-dependent and space-dependent around the energy of the knee. it has a major contribution of one or a few nearby recent sources at any given location in the galaxy, in particular at the position of the solar system. we find that the distribution of $\sim$ pev cosmic rays in our galaxy is significantly clumpy and inhomogeneous, and therefore substantially different from the smoother distribution of gev cosmic rays. our findings have important implications for the calculation and future interpretation of the diffuse galactic gamma-ray and neutrino fluxes at very high energies. | model of cosmic ray propagation in the milky way at the knee |
gravitational-wave observations of binary black hole (bbh) systems point to black hole spin magnitudes being relatively low. these measurements appear in tension with high spin measurements for high-mass x-ray binaries (hmxbs). we use grids of mesa simulations combined with the rapid population-synthesis code cosmic to examine the origin of these two binary populations. it has been suggested that case-a mass transfer while both stars are on the main sequence can form high-spin bhs in hmxbs. assuming this formation channel, we show that depending on the critical mass ratios for the stability of mass transfer, 48%-100% of these case-a hmxbs merge during the common-envelope phase and up to 42% result in binaries too wide to merge within a hubble time. both mesa and cosmic show that high-spin hmxbs formed through case-a mass transfer can only form merging bbhs within a small parameter space where mass transfer can lead to enough orbital shrinkage to merge within a hubble time. we find that only up to 11% of these case-a hmxbs result in bbh mergers, and at most 20% of bbh mergers came from case-a hmxbs. therefore, it is not surprising that these two spin distributions are observed to be different. | do high-spin high-mass x-ray binaries contribute to the population of merging binary black holes? |
sunyaev-zel'dovich (sz) measurements can dramatically improve our understanding of the intergalactic medium and the role of feedback processes in galaxy formation, allowing us to calibrate important astrophysical systematics in cosmological constraints from weak lensing galaxy clustering surveys. however, the signal is only measured in a two-dimensional projection, and its correct interpretation relies on understanding the connection between observable quantities and the underlying intrinsic properties of the gas, in addition to the relation between the gas and the underlying matter distribution. one way to address these challenges is through the use of hydrodynamical simulations such as the high-resolution, large-volume millenniumtng suite. we find that measurements of the optical depth, τ, and the compton-y parameter, y, receive large line-of-sight contributions that can be removed effectively by applying a compensated aperture photometry filter. in contrast with other τ probes (e.g. x-rays and fast radio bursts), the kinematic sz-inferred τ receives most of its signal from a confined cylindrical region around the halo due to the velocity decorrelation along the line of sight. additionally, we perform fits to the y-m and τ-m scaling relations and report best-fitting parameters adopting the smoothly broken power law formalism. we note that subgrid physics modelling can broaden the error bar on these by 30 per cent for intermediate-mass haloes (${\sim }10^{13} \, {\rm m}_{\odot }$). the scatter of the scaling relations can be captured by an intrinsic dependence on concentration and an extrinsic dependence on tidal shear. finally, we comment on the effect of using galaxies rather than haloes in observations, which can bias the inferred profiles by ~20 per cent for l* galaxies. | interpreting sunyaev-zel'dovich observations with millenniumtng: mass and environment scaling relations |
understanding the conditions conducive to particle acceleration at collisionless, nonrelativistic shocks is important for the origin of cosmic rays. we use hybrid (kinetic ions-fluid electrons) kinetic simulations to investigate particle acceleration and magnetic field amplification at nonrelativistic, weakly magnetized, quasiperpendicular shocks. so far, no self-consistent kinetic simulation has reported nonthermal tails at quasiperpendicular shocks. unlike 2d simulations, 3d runs show that protons develop a nonthermal tail spontaneously (i.e., from the thermal bath and without preexisting magnetic turbulence). they are rapidly accelerated via shock drift acceleration up to a maximum energy determined by their escape upstream. we discuss the implications of our results for the phenomenology of heliospheric shocks, supernova remnants, and radio supernovae. | fast particle acceleration in 3d hybrid simulations of quasiperpendicular shocks |
it is often stated that the observation of high-energy neutrinos from an astrophysical source would constitute indisputable proof for the acceleration of hadronic cosmic rays. here, we point out that there exists a purely leptonic mechanism to produce tev-scale neutrinos in astrophysical environments. in particular, very high-energy synchrotron photons can scatter with x rays, exceeding the threshold for muon-antimuon pair production. when these muons decay, they produce neutrinos without any cosmic-ray protons or nuclei being involved. in order for this mechanism to be efficient, the source in question must produce very high-energy photons which interact in an environment that is dominated by kev-scale radiation. we find that such a source could potentially generate an observable neutrino flux through muon pair production for reasonable choices of physical parameters. | leptonic model for neutrino emission from active galactic nuclei |
the ams-02 experiment has provided high-precision measurements of several cosmic-ray (cr) species. the achieved percent-level accuracy gives access to small spectral differences among the different species and, in turn, this allows scrutinizing the universality of cr acceleration, which is expected in the standard scenario of cr shock acceleration. while pre-ams-02 data already indicated a violation of the universality between protons and helium, it is still an open question if at least helium and heavier nuclei can be reconciled. to address this issue, we performed a joint analysis using the ams-02 cr measurements of antiprotons, protons, helium, helium 3, boron, carbon, nitrogen, and oxygen. we explore two competing propagation scenarios, one with a break in the diffusion coefficient at a few gvs and no reacceleration, and another one with reacceleration and with a break in the injection spectra of primaries. furthermore, we explicitly consider the impact of the uncertainties in the nuclear production cross sections of secondaries by including nuisance parameters in the fit. the resulting parameter space is explored with the help of monte carlo methods. we find that, contrary to the naive expectation, in the standard propagation scenarios cr universality is violated also for he, on the one hand, and c, n, and o, on the other hand, i.e., different injection slopes (at the level of δ ∼0.05 ) are required to explain the observed spectra. as an alternative, we explore further propagation scenarios, inspired by nonhomogeneous diffusion, which might save universality. finally, we also investigate the universality of cr propagation, i.e., we compare the propagation properties inferred using only light nuclei (p ¯, p, he, 3he ) with the ones inferred using only heavier nuclei (b, c, n, o). | testing the universality of cosmic-ray nuclei from protons to oxygen with ams-02 |
the x-ifu is the cryogenic spectrometer onboard the future athena x-ray observatory. it is based on a large array of tes microcalorimeters, which work in combination with a cryogenic anticoincidence detector (cryoac). this is necessary to reduce the particle background level thus enabling part of the mission science goals. here we present the first joint test of x-ifu tes array and cryoac demonstration models, performed in a fdm setup. we show that it is possible to operate properly both detectors, and we provide a preliminary demonstration of the anti-coincidence capability of the system achieved by the simultaneous detection of cosmic muons. | athena x-ifu demonstration model: first joint operation of the main tes array and its cryogenic anticoincidence detector (cryoac) |
we perform monte carlo simulations of transrelativistic shear acceleration dedicated to a jet-cocoon system of active galactic nuclei. a certain fraction of galactic cosmic rays in a halo is entrained, and sufficiently high-energy particles can be injected to the reacceleration process and further accelerated up to 100 eev. we show that the shear reacceleration mechanism leads to a hard spectrum of escaping cosmic rays, d le/d e ∝e-1-e0, distinct from a conventional e-2 spectrum. the supersolar abundance of ultrahigh-energy nuclei is achieved due to injections at tev-pev energies. as a result, we find that the highest-energy spectrum and mass composition can be reasonably explained by our model without contradictions with the anisotropy data. | ultrahigh-energy cosmic-ray nuclei from black hole jets: recycling galactic cosmic rays through shear acceleration |
context. the neutrino event icecube-170922a appears to originate from the bl lac object txs 0506+056. to understand the neutrino creation process and to localize the emission site, we studied the radio images of the jet at 15 ghz.aims: other bl lac objects show properties similar to those of txs 0506+056, such as multiwavelength variability or a curved jet. however, to date only txs 0506+056 has been identified as neutrino emitter. the aim of this paper is to determine what makes the parsec-scale jet of txs 0506+056 specific in this respect.methods: we reanalyzed and remodeled 16 vlba 15 ghz observations between 2009 and 2018. we thoroughly examined the jet kinematics and flux-density evolution of individual jet components during the time of enhanced neutrino activity between september 2014 and march 2015, and in particular before and after the neutrino event.results: our results suggest that the jet is very strongly curved and most likely observable under a special viewing angle of close to zero. we may observe the interaction between jet features that cross each other's paths. we find subsequent flux-density flaring of six components passing the likely collision site. in addition, we find a strong indication for precession of the inner jet, and model a precession period of about 10 yr via the lense-thirring effect. we discuss an alternative scenario, which is the interpretation of observing the signature of two jets within txs 0506+056, again hinting toward a collision of jetted material. we essentially suggest that the neutrino emission may result from the interaction of jetted material in combination with a special viewing angle and jet precession.conclusions: we propose that the enhanced neutrino activity during the neutrino flare in 2014-2015 and the single ehe neutrino icecube-170922a could have been generated by a cosmic collision within txs 0506+056. our findings seem capable of explaining the neutrino generation at the time of a low gamma-ray flux and also indicate that txs 0506+056 might be an atypical blazar. it seems to be the first time that a potential collision of two jets on parsec scales has been reported and that the detection of a cosmic neutrino might be traced back to a cosmic jet-collision. | a cosmic collider: was the icecube neutrino generated in a precessing jet-jet interaction in txs 0506+056? |
cosmic ray pressure gradients transfer energy and momentum to extraplanar gas in disk galaxies, potentially driving significant mass loss as galactic winds. this may be particularly important for launching high-velocity outflows of “cool” (t ≲ 104 k) gas. we study cosmic ray-driven disk winds using a simplified semi-analytic model assuming streamlines follow the large-scale gravitational potential gradient. we consider scaled milky way-like potentials including a disk, bulge, and halo with a range of halo velocities v h = 50-300 km s-1 and streamline footpoints with radii in the disk r 0 = 1-16 kpc at a height of 1 kpc. our solutions cover a wide range of footpoint gas velocity u 0, magnetic-to-cosmic ray pressure ratio, gas-to-cosmic ray pressure ratio, and angular momentum. cosmic ray streaming at the alfvén speed enables the effective sound speed c eff to increase from the footpoint to a critical point where c eff,c= uc∼ v h; this differs from thermal winds, in which c eff decreases outward. the critical point is typically at a height of 1-6 kpc from the disk, increasing with v h, and the asymptotic wind velocity exceeds the escape speed of the halo. mass-loss rates are insensitive to the footpoint values of the magnetic field and angular momentum. in addition to numerical parameter space exploration, we develop and compare to analytic scaling relations. we show that winds have mass-loss rates per unit area up to \dot{σ}∼ π0vh-5/3u02/3, where π0 is the footpoint cosmic ray pressure and u 0 is set by the upwelling of galactic fountains. the predicted wind mass-loss rate exceeds the star formation rate for v h ≲ 200 km s-1 and u 0 = 50 km s-1, a typical fountain velocity. | galactic disk winds driven by cosmic ray pressure |
aims: continuous measurements of ground-based neutron monitors (nms) form the main data source for studying high-energy high-intensity solar energetic particle (sep) events that are called ground-level enhancements (gles). all available data are collected in the international gle database (igled), which provides formal nm count-rate increases above the constant pre-increase level which is due to galactic cosmic rays (gcr). this data set is used to reconstruct the energy spectra of gle events. however, the assumption of a constant gcr background level throughout gle events is often invalid. here we thoroughly revise the igled and provide a data set of detrended nm count-rate increases that accounts for the variable gcr background.methods: the formal gle count-rate increases were corrected for the variable gcr background, which may vary significantly during gle events. the corresponding integral omnidirectional fluences of seps were reconstructed for all gles with sufficient strength from the detrended data using the effective rigidity method.results: the database of the detrended nm count rate is revised for gle events since 1956. integral omnidirectional fluences were estimated for 58 gle events and parametrised for 52 sufficiently strong events using the modified ellison-ramaty spectral shape.conclusions: the igled was revised to account for the variable gcr background. integral omnidirectional fluences reconstructed for most of gle events were added to igled. this forms the basis for more precise studies of parameters of sep events and thus for solar and space physics. the revised fluences are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/640/a17 | revised gle database: fluences of solar energetic particles as measured by the neutron-monitor network since 1956 |
the community coordinated modeling center has been leading community-wide space science and space weather model validation projects for many years. these efforts have been broadened and extended via the newly launched international forum for space weather modeling capabilities assessment (https://ccmc.gsfc.nasa.gov/assessment/). its objective is to track space weather models' progress and performance over time, a capability that is critically needed in space weather operations and different user communities in general. the space radiation and plasma effects working team of the aforementioned international forum works on one of the many focused evaluation topics and deals with five different subtopics (https://ccmc.gsfc.nasa.gov/assessment/topics/radiation-all.php) and varieties of particle populations: surface charging from tens of ev to 50-kev electrons and internal charging due to energetic electrons from hundreds kev to several mevs. single-event effects from solar energetic particles and galactic cosmic rays (several mev to tev), total dose due to accumulation of doses from electrons (>100 kev) and protons (>1 mev) in a broad energy range, and radiation effects from solar energetic particles and galactic cosmic rays at aviation altitudes. a unique aspect of the space radiation and plasma effects focus area is that it bridges the space environments, engineering, and user communities. the intent of the paper is to provide an overview of the current status and to suggest a guide for how to best validate space environment models for operational/engineering use, which includes selection of essential space environment and effect quantities and appropriate metrics. | space radiation and plasma effects on satellites and aviation: quantities and metrics for tracking performance of space weather environment models |
in this review, an overview of the recent history of stochastic differential equations (sdes) in application to particle transport problems in space physics and astrophysics is given. the aim is to present a helpful working guide to the literature and at the same time introduce key principles of the sde approach via "toy models". using these examples, we hope to provide an easy way for newcomers to the field to use such methods in their own research. aspects covered are the solar modulation of cosmic rays, diffusive shock acceleration, galactic cosmic ray propagation and solar energetic particle transport. we believe that the sde method, due to its simplicity and computational efficiency on modern computer architectures, will be of significant relevance in energetic particle studies in the years to come. | a hitch-hiker's guide to stochastic differential equations. solution methods for energetic particle transport in space physics and astrophysics |
the arianna hexagonal radio array (hra) is an experiment in its pilot phase designed to detect cosmogenic neutrinos of energies above 1016 ev. the most neutrino-like background stems from the radio emission of air showers. this article reports on dedicated efforts of simulating and detecting the signals of cosmic rays. a description of the fully radio self-triggered data-set, the properties of the detected air shower signals in the frequency range of 100-500 mhz and the consequences for neutrino detection are given. 38 air shower signals are identified by their distinct waveform characteristics, are in good agreement with simulations and their signals provide evidence that neutrino-induced radio signals will be distinguishable with high efficiency in arianna. the cosmic ray flux at a mean energy of 6.5-1.0+1.2 ×1017 ev is measured to be 1.1-0.7+1.0 ×10-16 ev-1 km-2 sr-1 yr-1 and one five-fold coincident event is used to illustrate the capabilities of the arianna detector to reconstruct arrival direction and energy of air showers. | radio detection of air showers with the arianna experiment on the ross ice shelf |
large-scale galactic winds driven by stellar feedback are one phenomenon that influences the dynamical and chemical evolution of a galaxy, redistributing material throughout the circumgalatic medium. non-thermal feedback from galactic cosmic rays (crs) - high-energy charged particles accelerated in supernovae and young stars - can impact the efficiency of wind driving. the streaming instability limits the speed at which they can escape. however, in the presence of turbulence, the streaming instability is subject to suppression that depends on the magnetization of turbulence given by its alfvén mach number. while previous simulations that relied on a simplified model of cr transport have shown that super-alfvénic streaming of crs enhances galactic winds, in this paper we take into account a realistic model of streaming suppression. we perform three-dimensional magnetohydrodynamic simulations of a section of a galactic disc and find that turbulent damping dependent on local magnetization of turbulent interstellar medium (ism) leads to more spatially extended gas and cr distributions compared to the earlier streaming calculations, and that scale heights of these distributions increase for stronger turbulence. our results indicate that the star formation rate increases with the level of turbulence in the ism. we also find that the instantaneous wind mass loading is sensitive to local streaming physics with the mass loading dropping significantly as the strength of turbulence increases. | role of cosmic-ray streaming and turbulent damping in driving galactic winds |
understanding the spectral and flavor composition of the astrophysical neutrino flux responsible for the recently observed ultrahigh-energy events at icecube is of great importance for both astrophysics and particle physics. we perform a statistical likelihood analysis to the three-year icecube data and derive the allowed range of the spectral index and flux normalization for various well-motivated physical flavor compositions at the source. while most of the existing analyses so far assume the flavor composition of the neutrinos at an astrophysical source to be (1:2:0), it seems rather unnatural to assume only one type of source, once we recognize the possibility of at least two physical sources. bearing this in mind, we entertain the possibility of a two-component source for the analysis of icecube data. it appears that our two-component hypothesis explains some key features of the data better than a single-component scenario; i.e. it addresses the apparent energy gap between 400 tev and about 1 pev and easily accommodates the observed track-to-shower ratio. given the extreme importance of the flavor composition for the correct interpretation of the underlying astrophysical processes as well as for the ramification for particle physics, this two-component flux should be tested as more data is accumulated. | two-component flux explanation for the high energy neutrino events at icecube |
icecube has measured a diffuse astrophysical flux of tev-pev neutrinos. the most plausible sources are unique high energy cosmic ray accelerators like hypernova remnants (hnrs) and remnants from gamma ray bursts in star-burst galaxies, which can produce primary cosmic rays with the required energies and abundance. in this case, however, ordinary supernova remnants (snrs), which are far more abundant than hnrs, produce a comparable or larger neutrino flux in the ranges up to 100-150 tev energies, implying a spectral break in the icecube signal around these energies. the snrs contribution in the diffuse flux up to these hundred tev energies provides a natural baseline and then constrains the expected pev flux. | diffuse neutrinos from extragalactic supernova remnants: dominating the 100 tev icecube flux |
we present the 3-8 kev and 8-24 kev number counts of active galactic nuclei (agns) identified in the nuclear spectroscopic telescope array (nustar) extragalactic surveys. nustar has now resolved 33%-39% of the x-ray background in the 8-24 kev band, directly identifying agns with obscuring columns up to ∼ {10}25 {{cm}}-2. in the softer 3-8 kev band the number counts are in general agreement with those measured by xmm-newton and chandra over the flux range 5× {10}-15 ≲ s(3-8 kev)/{erg} {{{s}}}-1 {{cm}}-2 ≲ {10}-12 probed by nustar. in the hard 8-24 kev band nustar probes fluxes over the range 2× {10}-14 ≲ s(8-24 kev)/{erg} {{{s}}}-1 {{cm}}-2 ≲ {10}-12, a factor ∼100 fainter than previous measurements. the 8-24 kev number counts match predictions from agn population synthesis models, directly confirming the existence of a population of obscured and/or hard x-ray sources inferred from the shape of the integrated cosmic x-ray background. the measured nustar counts lie significantly above simple extrapolation with a euclidian slope to low flux of the swift/bat 15-55 kev number counts measured at higher fluxes (s(15-55 kev) ≳ 10-11 {erg} {{{s}}}-1 {{cm}}-2), reflecting the evolution of the agn population between the swift/bat local (z\lt 0.1) sample and nustar’s z∼ 1 sample. cxb synthesis models, which account for agn evolution, lie above the swift/bat measurements, suggesting that they do not fully capture the evolution of obscured agns at low redshifts. | the nustar extragalactic surveys: the number counts of active galactic nuclei and the resolved fraction of the cosmic x-ray background |
we present a new reconstruction of the distribution of atomic hydrogen in the inner galaxy that is based on explicit radiation transport modeling of line and continuum emission and a gas-flow model in the barred galaxy that provides distance resolution for lines of sight toward the galactic center. the main benefits of the new gas model are (a) the ability to reproduce the negative line signals seen with the hi4pi survey and (b) the accounting for gas that primarily manifests itself through absorption. we apply the new model of galactic atomic hydrogen to an analysis of the diffuse gamma-ray emission from the inner galaxy, for which an excess at a few gev was reported that may be related to dark matter. we find with high significance an improved fit to the diffuse gamma-ray emission observed with the fermi-lat, if our new h i model is used to estimate the cosmic-ray induced diffuse gamma-ray emission. the fit still requires a nuclear bulge at high significance. once this is included there is no evidence of a dark-matter signal, be it cuspy or cored. but an additional so-called boxy bulge is still favored by the data. this finding is robust under the variation of various parameters, for example, the excitation temperature of atomic hydrogen, and a number of tests for systematic issues. | assessing the impact of hydrogen absorption on the characteristics of the galactic center excess |
we study the propagation of mildly relativistic cosmic rays (crs) in multiphase interstellar medium environments with conditions typical of nearby disk galaxies. we employ the techniques developed in armillotta et al. to postprocess three high-resolution tigress magnetohydrodynamic simulations modeling local patches of star-forming galactic disks. together, the three simulations cover a wide range of gas surface density, gravitational potential, and star formation rate (sfr). our prescription for cr propagation includes the effects of advection by the background gas, streaming along the magnetic field at the local ion alfvén speed, and diffusion relative to the alfvén waves, with the diffusion coefficient set by the balance between streaming-driven alfvén wave excitation and damping mediated by local gas properties. we find that the combined transport processes are more effective in environments with higher sfr. these environments are characterized by higher-velocity hot outflows (created by clustered supernovae) that rapidly advect crs away from the galactic plane. as a consequence, the ratio of midplane cr pressure to midplane gas pressures decreases with increasing sfr. we also use the postprocessed simulations to make predictions regarding the potential dynamical impacts of crs. the relatively flat cr pressure profiles near the midplane argue that they would not provide significant support against gravity for most of the ism mass. however, the cr pressure gradients are larger than the other pressure gradients in the extraplanar region (∣z∣ > 0.5 kpc), suggesting that crs may affect the dynamics of galactic fountains and/or winds. the degree of this impact is expected to increase in environments with lower sfr. | cosmic-ray transport in varying galactic environments |
we present a complete phenomenological model accounting for the evolution of the cosmic ray spectrum and composition with energy, based on the available data over the entire spectrum. we show that there is no need to postulate any additional component, other than one single galactic component depending on rigidity alone and one extragalactic component, the characteristics of which are similar to those derived from a study of particle acceleration at mildly relativistic shocks in a gamma-ray burst environment (globus et al., 2015). in particular, we show that the resulting cosmic ray spectrum and composition satisfy the various constraints derived from the current data in the galactic/extragalactic transition region, notably from the measurements of kascade grande and auger. finally, we derive some generic features that a working phenomenological scenario may exhibit to give a global account of the cosmic ray data with a minimum number of free parameters. | a complete model of the cosmic ray spectrum and composition across the galactic to extragalactic transition |
the ciber collaboration released their first observational data of the cosmic ir background (cib) radiation, which has significant excesses at around the wavelength ∼1 μ m compared to theoretically-inferred values. the amount of the cib radiation has a significant influence on the opaqueness of the universe for tev gamma-rays emitted from distant sources such as active galactic nuclei (agns). with the value of cib radiation reported by the ciber experiment, through the reaction of such tev gamma-rays with the cib photons, the tev gamma-rays should be significantly attenuated during propagation, which would lead to energy spectra in disagreement with current observations of tev gamma ray sources. in this article, we discuss a possible resolution of this tension between the tev gamma-ray observations and the cib data in terms of axion [or axion-like particles (alps)] that may increase the transparency of the universe by the anomaly-induced photon-axion mixing. we find a region in the parameter space of the axion mass, ma∼7 ×1 0-10- 5 ×1 0-8 ev , and the axion-photon coupling constant, 1.5 ×10-11 gev-1≲ga γ≲8.8 ×10-10 gev-1 that solves this problem. | axion-like particles and recent observations of the cosmic infrared background radiation |
we report on the analysis of the 10-1000 tev large-scale sidereal anisotropy of galactic cosmic rays (gcrs) with the data collected by the tibet air shower array from 1995 october to 2010 february. in this analysis, we improve the energy estimate and extend the decl. range down to -30°. we find that the anisotropy maps above 100 tev are distinct from that at a multi-tev band. the so-called tail-in and loss-cone features identified at low energies get less significant, and a new component appears at ∼100 tev. the spatial distribution of the gcr intensity with an excess (7.2σ pre-trial, 5.2σ post-trial) and a deficit (-5.8σ pre-trial) are observed in the 300 tev anisotropy map, in close agreement with icecube’s results at 400 tev. combining the tibet results in the northern sky with icecube’s results in the southern sky, we establish a full-sky picture of the anisotropy in hundreds of tev band. we further find that the amplitude of the first order anisotropy increases sharply above ∼100 tev, indicating a new component of the anisotropy. all these results may shed new light on understanding the origin and propagation of gcrs. | northern sky galactic cosmic ray anisotropy between 10 and 1000 tev with the tibet air shower array |
nonrelativistic dark matter (dm) can be accelerated by scattering on high-energy cosmic-ray (cr) electrons. this process leads to a subpopulation of relativistic or semirelativistic dm which extends the experimental reach for direct detection in the sub-gev mass regime. in this paper we examine the current and future potential of this mechanism for constraining models of light dark matter. in particular, we find that super-kamiokande and xenon1t data can already provide leading constraints on the flux of dark matter that has been accelerated to high energies from cosmic ray electrons. we also examine future projected sensitivities for dune and hyper-k, and contrary to previous findings, conclude that dune will be able supersede super-k bounds on cosmic-ray upscattered dm for a variety of dm models. | present and future status of light dark matter models from cosmic-ray electron upscattering |
we study the cutoff for the cosmic-ray neutrino, set by the scattering with cosmic background neutrinos into dark sector particles through a neutrino portal interaction. we find that a large interaction rate is still viable, when the dark sector particles are mainly coupled to the τ-neutrino, so that the neutrino mean free path can be reduced to be o(10) mpc over a wide energy range. if stable enough, the dark sector particle, into which most of the cosmic-ray neutrino energy is transferred, can travel across the universe and reach the earth. the dark sector particle can carry the energy as large as o(eev) if it originates from a cosmogenic neutrino. | highly-boosted dark matter and cutoff for cosmic-ray neutrinos through neutrino portal |
galactic charged cosmic rays (notably electrons, positrons, antiprotons, and light antinuclei) are powerful probes of dark matter annihilation or decay, in particular, for candidates heavier than a few mev or tiny evaporating primordial black holes. recent measurements by pamela, ams-02, or voyager on positrons and antiprotons already translate into constraints on several models over a large mass range. however, these constraints depend on galactic transport models, in particular, the diffusive halo size, subject to theoretical and statistical uncertainties. we update the so-called min-med-max benchmark transport parameters that yield generic minimal, median, and maximal dark-matter-induced fluxes; this reduces the uncertainties on fluxes by a factor of about 2 for positrons and 6 for antiprotons, with respect to their former version. we also provide handy fitting formulas for the associated predicted secondary antiproton and positron background fluxes. finally, for more refined analyses, we provide the full details of the model parameters and covariance matrices of uncertainties. | new minimal, median, and maximal propagation models for dark matter searches with galactic cosmic rays |
we perform a global fit within the pseudo-nambu-goldstone dark matter (dm) model emerging from an additional complex scalar singlet with a softly broken global u (1) symmetry. leading to a momentum-suppressed dm-nucleon cross section at tree level, the model provides a natural explanation for the null results from direct detection experiments. our global fit combines constraints from perturbative unitarity, dm relic abundance, higgs invisible decay, electroweak precision observables and latest higgs searches at colliders. the results are presented in both frequentist and bayesian statisical frameworks. furthermore, post-processing our samples, we include the likelihood from gamma-ray observations of fermi -lat dwarf spheroidal galaxies and compute the one-loop dm-nucleon cross section. we find two favoured regions characterised by their dominant annihilation channel: the higgs funnel and annihilation into higgs pairs. both are compatible with current fermi -lat observations, and furthermore, can fit the slight excess observed in four dwarfs in a mass range between about 30-300 gev. while the former region is hard to probe experimentally, the latter can partly be tested by current observations of cosmic-ray antiprotons as well as future gamma-ray observations. | global fit of pseudo-nambu-goldstone dark matter |
stratiform clouds constitute ∼40% of global cloud cover and play a key role in determining the planetary radiation budget. electrification remains one of the least understood effects on their microphysical processes. droplet charging at the top and bottom edges of stratiform clouds arises from vertical current flow through clouds driven by the global atmospheric electric circuit. in-cloud charge data are central in assessing the role of charge in droplet growth processes, which influence droplet size distributions and associated cloud radiative properties and precipitation. this study presents the first high vertical resolution electrical measurements made in multiple layer clouds. of the 22 clouds sampled, all were charged at their edges, demonstrating unequivocally that all stratiform clouds can be expected to contain charge at their upper and lower boundaries to varying extent. cloud base and cloud top are shown to charge asymmetrically, with mean cloud-top space charge +32 pc m−3 and base space charge −24 pc m−3. the larger cloud-top charges are associated with strong temperature inversions and large vertical electrical conductivity gradients at the upper cloud boundary. greater charging was observed in low altitude (<2 km) clouds (20.2 pc m−3), compared to higher altitude (>2 km) cloud layers (7.0 pc m−3), consistent with the smaller air conductivity at lower altitudes associated with reduced cosmic ray ionisation. taken together, these measurements show that the greatest cloud droplet charges in extensive stratiform clouds occur at cloud tops for low altitude (<2 km) clouds, when vertical mixing is suppressed by appreciable temperature inversions, confirming theoretical expectations. the influence of cloud dynamics on layer cloud edge charging reported here should inform modelling studies of cloud droplet charging effects on cloud microphysics. | stratiform cloud electrification: comparison of theory with multiple in-cloud measurements |
we present a search for a neutrino signal from dark matter self-annihilations in the milky way using the icecube neutrino observatory (icecube). in 1005 days of data we found no significant excess of neutrinos over the background of neutrinos produced in atmospheric air showers from cosmic ray interactions. we derive upper limits on the velocity averaged product of the dark matter self-annihilation cross section and the relative velocity of the dark matter particles $\langle\sigma_{\text{a}}v\rangle$. upper limits are set for dark matter particle candidate masses ranging from 10 gev up to 1 tev while considering annihilation through multiple channels. this work sets the most stringent limit on a neutrino signal from dark matter with mass between 10 gev and 100 gev, with a limit of $1.18\cdot10^{-23}\text{cm}^3\text{s}^{-1}$ for 100 gev dark matter particles self-annihilating via $\tau^+\tau^-$ to neutrinos (assuming the navarro-frenk-white dark matter halo profile). | search for neutrinos from dark matter self-annihilations in the center of the milky way with 3 years of icecube/deepcore |
if dark matter particles have an electric charge, as in models of millicharged dark matter, such particles should be accelerated in the same astrophysical accelerators that produce ordinary cosmic rays, and their spectra should have a predictable rigidity dependence. depending on the charge, the resulting ;dark cosmic rays; can be detected as muon-like or neutrino-like events in super-kamiokande, icecube, and other detectors. we present new limits and propose several new analyses, in particular, for the super-kamiokande experiment, which can probe a previously unexplored portion of the millicharged dark matter parameter space. most of our results are fairly general and apply to a broad class of dark matter models. | dark cosmic rays |
snow water equivalent (swe) measurements of seasonal snowpack are crucial in many research fields. yet accurate measurements at a high temporal resolution are difficult to obtain in high mountain regions. with a cosmic ray sensor (crs), swe can be inferred from neutron counts. we present the analyses of temporally continuous swe measurements by a crs on an alpine glacier in switzerland (glacier de la plaine morte) over two winter seasons (2016/17 and 2017/18), which differed markedly in the amount and timing of snow accumulation. by combining swe with snow depth measurements, we calculate the daily mean density of the snowpack. compared to manual field observations from snow pits, the autonomous measurements overestimate swe by +2 % ± 13 %. snow depth and the bulk snow density deviate from the manual measurements by ±6 % and ±9 %, respectively. the crs measured with high reliability over two winter seasons and is thus considered a promising method to observe swe at remote alpine sites. we use the daily observations to classify winter season days into those dominated by accumulation (solid precipitation, snow drift), ablation (snow drift, snowmelt) or snow densification. for each of these process-dominated days the prevailing meteorological conditions are distinct. the continuous swe measurements were also used to define a scaling factor for precipitation amounts from nearby meteorological stations. with this analysis, we show that a best-possible constant scaling factor results in cumulative precipitation amounts that differ by a mean absolute error of less than 80 mm w.e. from snow accumulation at this site. | continuous and autonomous snow water equivalent measurements by a cosmic ray sensor on an alpine glacier |
for precision cosmological studies it is important to know the local properties of the reference point from which we observe the universe. particularly for the determination of the hubble constant with low-redshift distance indicators, the values observed depend on the average matter density within the distance range covered. in this study we used the spatial distribution of galaxy clusters to map the matter density distribution in the local universe. the study is based on our classix galaxy cluster survey, which is highly complete and well characterised, where galaxy clusters are detected by their x-ray emission. in total, 1653 galaxy clusters outside the "zone of avoidance" fulfil the selection criteria and are involved in this study. we find a local underdensity in the cluster distribution of about 30-60% which extends about 85 mpc to the north and ∼170 mpc to the south. we study the density distribution as a function of redshift in detail in several regions in the sky. for three regions for which the galaxy density distribution has previously been studied, we find good agreement between the density distribution of clusters and galaxies. correcting for the bias in the cluster distribution we infer an underdensity in the matter distribution of about -30 ± 15% (-20 ± 10%) in a region with a radius of about 100 (∼140) mpc. calculating the probability of finding such an underdensity through structure formation theory in a λcdm universe with concordance cosmological parameters, we find a probability characterised by σ-values of 1.3 - 3.7. this indicates low probabilities, but with values of around 10% at the lower uncertainty limit, the existence of an underdensity cannot be ruled out. inside this underdensity, the observed hubble parameter will be larger by about 5.5 +2.1-2.8%, which explains part of the discrepancy between the locally measured value of h0 compared to the value of the hubble parameter inferred from the planck observations of cosmic microwave background anisotropies. if distance indicators outside the local underdensity are included, as in many modern analyses, this effect is diluted. based on observations at the european southern observatory la silla, chile and the german-spanish observatory at calar alto. | observational evidence for a local underdensity in the universe and its effect on the measurement of the hubble constant |
since lorentz invariance plays an important role in modern physics, it is of interest to test the possible lorentz invariance violation (liv). the time-lag (the arrival time delay between light curves in different energy bands) of gamma-ray bursts (grbs) has been extensively used to this end. however, to our best knowledge, one or more particular cosmological models were assumed a priori in (almost) all of the relevant works in the literature. so, this makes the results on liv in those works model-dependent and hence not so robust in fact. in the present work, we try to avoid this problem by using a model-independent approach. we calculate the time delay induced by liv with the cosmic expansion history given in terms of cosmography, without assuming any particular cosmological model. then, we constrain the possible liv with the observational data, and find weak hints for liv. | model-independent constraints on lorentz invariance violation via the cosmographic approach |
it is very well known that the fraction of energy in a hadron collision going into electromagnetic particles (electrons and photons, including those from decays) has a large impact on the number of muons produced in air shower cascades. recent measurements at the lhc confirm features that can be linked to a mixture of different underlying particle production mechanisms such as a collective statistical hadronization (core) in addition to the expected string fragmentation (corona). since the two mechanisms have a different electromagnetic energy fraction, we present a possible connection between statistical hadronization in hadron collisions and muon production in air showers. using a novel approach, we demonstrate that the core-corona effect as observed at the lhc could be part of the solution for the lack of muon production in simulations of high energy cosmic rays. to probe this hypothesis, we study hadronization in high energy hadron collisions using calorimetric information over a large range of pseudorapidity in combination with the multiplicity of central tracks. as an experimental observable, we propose the production of energy in electromagnetic particles versus hadrons, as a function of pseudorapidity and central charged particle multiplicity. | core-corona effect in hadron collisions and muon production in air showers |
we study interactions of cosmological relics, x, of mass m and electric charge qe in the galaxy, including thermalization with the interstellar medium, diffusion through inhomogeneous magnetic fields and fermi acceleration by supernova shock waves. we find that for m lesssim 1010 q gev, there is a large flux of accelerated x in the disk today, with a momentum distribution propto 1/p2.5 extending to (β p)max ~ 5 ×104 q gev. even though acceleration in supernova shocks is efficient, ejecting x from the galaxy, x are continually replenished by diffusion into the disk from the halo or confinement region. for m gtrsim 1010 q gev, x cannot be accelerated above the escape velocity within the lifetime of the shock. the accelerated x form a component of cosmic rays that can easily reach underground detectors, as well as deposit energies above thresholds, enhancing signals in various experiments. we find that nuclear/electron recoil experiments place very stringent bounds on x at low q; for example, x as dark matter is excluded for q > 10-9 and m < 105 gev. for larger q or m, stringent bounds on the fraction of dark matter that can be x are set by cherenkov and ionization detectors. nevertheless, very small q is highly motivated by the kinetic mixing portal, and we identify regions of (m,q) that can be probed by future experiments. | champ cosmic rays |
we investigate the role of supermassive black holes in the global context of galaxy evolution by measuring the host galaxy stellar mass function (hgmf) and the specific accretion rate, that is, λsar, the distribution function (sardf), up to z ~ 2.5 with ~1000 x-ray selected agn from xmm-cosmos. using a maximum likelihood approach, we jointly fit the stellar mass function and specific accretion rate distribution function, with the x-ray luminosity function as an additional constraint. our best-fit model characterizes the sardf as a double power-law with mass-dependent but redshift-independent break, whose low λsar slope flattens with increasing redshift while the normalization increases. this implies that for a given stellar mass, higher λsar objects have a peak in their space density at earlier epoch than the lower λsar objects, following and mimicking the well-known agn cosmic downsizing as observed in the agn luminosity function. the mass function of active galaxies is described by a schechter function with an almost constant m∗⋆ and a low-mass slope α that flattens with redshift. compared to the stellar mass function, we find that the hgmf has a similar shape and that up to log (m⋆/m⊙) ~ 11.5, the ratio of agn host galaxies to star-forming galaxies is basically constant (~10%). finally, the comparison of the agn hgmf for different luminosity and specific accretion rate subclasses with a previously published phenomenological model prediction for the "transient" population, which are galaxies in the process of being mass-quenched, reveals that low-luminosity agn do not appear to be able to contribute significantly to the quenching and that at least at high masses, that is, m⋆ > 1010.7 m⊙, feedback from luminous agn (log lbol ≳ 46 [erg/s]) may be responsible for the quenching of star formation in the host galaxy. | agn host galaxy mass function in cosmos. is agn feedback responsible for the mass-quenching of galaxies? |
we present an underground cosmic ray muon tomographic experiment imaging 3d density of overburden, part of a joint study with differential gravity. muon data were acquired at four locations within a tunnel beneath los alamos, new mexico, and used in a 3d tomographic inversion to recover the spatial variation in the overlying rock-air interface, and compared with a priori knowledge of the topography. densities obtained exhibit good agreement with preliminary results of the gravity modeling, which will be presented elsewhere, and are compatible with values reported in the literature. the modeled rock-air interface matches that obtained from lidar within 4 m, our resolution, over much of the model volume. this experiment demonstrates the power of cosmic ray muons to image shallow geological targets using underground detectors, whose development as borehole devices will be an important new direction of passive geophysical imaging. | 3d cosmic ray muon tomography from an underground tunnel |
we present simulations of cosmic reionization and reheating from z = 18 to z = 5, investigating the role of stars (emitting soft uv-photons), nuclear black holes (bhs, with power-law spectra), x-ray binaries (xrbs, with hard x-ray dominated spectra), and the supernova-associated thermal bremsstrahlung of the diffuse interstellar medium (ism, with soft x-ray spectra). we post-process the hydrodynamical simulation massiveblack-ii (mbii) with multifrequency ionizing radiative transfer. the source properties are directly derived from the physical environment of mbii, and our only real free parameter is the ionizing escape fraction fesc. we find that, among the models explored here, the one with an escape fraction that decreases with decreasing redshift yields results most in line with observations, such as of the neutral hydrogen fraction and the thomson scattering optical depth. stars are the main driver of hydrogen reionization and consequently of the thermal history of the intergalactic medium (igm). we obtain <xh ii> = 0.99998 at z = 6 for all source types, with volume-averaged temperatures $\langle \, t \rangle \sim 20\,000$ k. bhs are rare and negligible to hydrogen reionization, but conversely they are the only sources that can fully ionize helium, increasing local temperatures by ∼104 k. the thermal and ionization state of the neutral and lowly ionized hydrogen differs significantly with different source combinations, with ism and (to a lesser extent) xrbs, playing a significant role and, as a consequence, determining the transition from absorption to emission of the 21-cm signal from neutral hydrogen. | large-scale simulations of h and he reionization and heating driven by stars and more energetic sources |
dark matter particles gravitationally bound to our galaxy should exhibit a characteristic speed distribution limited by their escape velocity at the position of earth (vesc≃550 km /s ). an ongoing search for anomalous cosmic rays at earth, kinematically similar to cold dark matter, is described. the technique can discriminate between these and known slow-moving particles such as neutrons, would be sensitive to telltale signatures from presently unexplored candidates, and offers the possibility of identifying the mediating type of interaction (nuclear vs electron recoils). studies of background identification and abatement in a shallow underground site are presented. the expected reach of the method is discussed, and illustrated by obtaining the first limits for dark matter particles lighter than 100 mev /c2 interacting via nuclear recoils. | search for a nonrelativistic component in the spectrum of cosmic rays at earth |
a possible hint of dark matter annihilation has been found in cuoco, korsmeier and krämer (2017) from an analysis of recent cosmic-ray antiproton data from ams-02 and taking into account cosmic-ray propagation uncertainties by fitting at the same time dark matter and propagation parameters. here, we extend this analysis to a wider class of annihilation channels. we find consistent hints of a dark matter signal with an annihilation cross-section close to the thermal value and with masses in range between 40 and 130 gev depending on the annihilation channel. furthermore, we investigate in how far the possible signal is compatible with the galactic center gamma-ray excess and recent observation of dwarf satellite galaxies by performing a joint global fit including uncertainties in the dark matter density profile. as an example, we interpret our results in the framework of the higgs portal model. | probing dark matter annihilation in the galaxy with antiprotons and gamma rays |
precise measurements of the energy spectra of cosmic rays (crs) show various kinds of features deviating from single power-laws, which give very interesting and important implications on their origin and propagation. previous measurements from a few balloon and space experiments indicate the existence of spectral softenings around 10 tv for protons (and probably also for helium nuclei). very recently, the dark matter particle explorer (dampe) measurement about the proton spectrum clearly reveals such a softening with a high significance. here we study the implications of these new measurements, as well as the groundbased indirect measurements, on the origin of crs. we find that a single component of crs fails to fit the spectral softening and the air shower experiment data simultaneously. in the framework of multiple components, we discuss two possible scenarios, the multiple source population scenario and the background plus nearby source scenario. both scenarios give reasonable fits to the wide-band data from tev to 100 pev energies. considering the anisotropy observations, the nearby source model is favored. | implications on the origin of cosmic rays in light of 10 tv spectral softenings |
context. cosmic rays and magnetic fields are key ingredients in galaxy evolution, regulating both stellar feedback and star formation. their properties can be studied with low-frequency radio continuum observations that are free from thermal contamination.aims: we define a sample of 76 nearby (< 30 mpc) galaxies with rich ancillary data in the radio continuum and infrared from the chang-es and kingfish surveys, which will be observed with the lofar two-metre sky survey (lotss) at 144 mhz.methods: we present maps for 45 of them as part of the lotss data release 2 (lotss-dr2), where we measure integrated flux densities and study integrated and spatially resolved radio spectral indices. we investigate the radio-star formation rate (sfr) relation using sfrs derived from total infrared and hα + 24-μm emission.results: the radio-sfr relation at 144 mhz is clearly super-linear with l144 mhz ∝ sfr1.4−1.5. the mean integrated radio spectral index between 144 and ≈1400 mhz is ⟨α⟩= − 0.56 ± 0.14, in agreement with the injection spectral index for cosmic ray electrons (cres). however, the radio spectral index maps show variation of spectral indices with flatter spectra associated with star-forming regions and steeper spectra in galaxy outskirts and, in particular, in extra-planar regions. we found that galaxies with high sfrs have steeper radio spectra; we find similar correlations with galaxy size, mass, and rotation speed.conclusions: galaxies that are larger and more massive are better electron calorimeters, meaning that the cre lose a higher fraction of their energy within the galaxies. this explains the super-linear radio-sfr relation, with more massive, star-forming galaxies being radio bright. we propose a semi-calorimetric radio-sfr relation that employs the galaxy mass as a proxy for the calorimetric efficiency. tables and fits maps are only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/664/a83 | nearby galaxies in the lofar two-metre sky survey. i. insights into the non-linearity of the radio-sfr relation |
we demonstrate that the ultra-high-energy cosmic rays (uhecrs) produced in the nuclear cascade in the jets of low-luminosity gamma-ray bursts (ll-grbs) can describe the uhecr spectrum and composition, and at the same time, the diffuse neutrino flux at the highest energies. the radiation density in the source simultaneously controls the neutrino production and the development of the nuclear cascade, leading to a flux of nucleons and light nuclei describing even the cosmic-ray ankle at 5 · 1018 ev. the derived source parameters are consistent with population studies, indicating a baryonic loading factor of about 10. our results motivate the continued experimental search of ll-grbs as a unique grb population. | on the common origin of cosmic rays across the ankle and diffuse neutrinos at the highest energies from low-luminosity gamma-ray bursts |
galactic cosmic rays (crs) inside the heliosphere are affected by solar modulation. to investigate this phenomenon and its underlying physical mechanisms, we have performed a data-driven analysis of the temporal dependence of the cr proton flux over the solar cycle. the modulation effect was modeled by means of stochastic simulations of cosmic particles in the heliosphere. the model was constrained using measurements of cr protons made by ams-02 and pamela experiments on a monthly basis from 2006 to 2017. with a global statistical analysis of these data, we have determined the key model parameters governing cr diffusion, its dependence on the particle rigidity, and its evolution over the solar cycle. our results span over epochs of solar minimum and solar maximum, as well as epochs with magnetic reversal and opposite polarities. along with the evolution of the cr transport parameters, we study their relationship with solar activity proxies and interplanetary parameters. we find that the rigidity dependence of the parallel mean free path of cr diffusion shows a remarkable time dependence, indicating a long-term variability in the interplanetary turbulence that interchanges across different regimes over the solar cycle. the evolution of the diffusion parameters shows a delayed correlation with solar activity proxies, reflecting the dynamics of the heliospheric plasma, and distinct dependencies for opposite states of magnetic polarity, reflecting the influence of charge-sign-dependent drift in the cr modulation. | numerical modeling of cosmic rays in the heliosphere: analysis of proton data from ams-02 and pamela |
we present an uncertainty analysis on correlation-based time delay estimate, the basis for broadband lightning interferometry. a normal interferometry would yield much higher uncertainties than the theoretically predicted lower bound due to finite correlation window lengths. however, if the signals are aligned in time, the uncertainties approach the lower bound and can be used to indicate the interferometric uncertainties. based on this, we introduce a beam steering interferometry technique. it first estimates a direction centroid for the lightning sources with a normal interferometry and computes the time delays among the signals. it then shifts the raw data with the time delays to align the signals roughly in time and reprocess the aligned signals. it finally pushes the reprocessed results to their correct positions, based on the time delays estimated in the first step. we apply this technique on a fast positive breakdown (fpb) process that started a normal intracloud lightning. the fpb process is shown to have a much more complex structure and development than a normal interferometry would provide. more importantly, from both interferometric and polarization analyses, the fpb appears to be ignited by a cosmic ray shower (crs). we estimate the radio frequency strength and frequency content related to a presumed crs in a thunderstorm electric field and find that they are in agreement with the observations. we examine the electric field effect of the crs front and find that it could raise the field above the threshold for positive breakdown and is capable of igniting the fpb (and the lightning). | lightning interferometry uncertainty, beam steering interferometry, and evidence of lightning being ignited by a cosmic ray shower |
the conventional definition of ground-level enhancement (gle) events requires a detection of solar energetic particles (sep) by at least two differently located neutron monitors. some places are exceptionally well suitable for ground-based detection of sep - high-elevation polar regions with negligible geomagnetic and reduced atmospheric energy/rigidity cutoffs. at present, there are two neutron-monitor stations in such locations on the antarctic plateau: sopo/sopb (at amundsen-scott station, 2835 m elevation), and domc/domb (at concordia station, 3233 m elevation). since 2015, when the domc/domb station started continuous operation, a relatively weak sep event that was not detected by sea-level neutron-monitor stations was registered by both sopo/sopb and domc/domb, and it was accordingly classified as a gle. this would lead to a distortion of the homogeneity of the historic gle list and the corresponding statistics. to address this issue, we propose to modify the gle definition so that it maintains the homogeneity: a gle event is registered when there are near-time coincident and statistically significant enhancements of the count rates of at least two differently located neutron monitors, including at least one neutron monitor near sea level and a corresponding enhancement in the proton flux measured by a space-borne instrument(s). relatively weak sep events registered only by high-altitude polar neutron monitors, but with no response from cosmic-ray stations at sea level, can be classified as sub-gles. | gle and sub-gle redefinition in the light of high-altitude polar neutron monitors |
we report on the measurement of the all-particle cosmic ray energy spectrum with the high altitude water cherenkov (hawc) observatory in the energy range 10 to 500 tev. hawc is a ground-based air-shower array deployed on the slopes of volcan sierra negra in the state of puebla, mexico, and is sensitive to gamma rays and cosmic rays at tev energies. the data used in this work were taken over 234 days between june 2016 and february 2017. the primary cosmic-ray energy is determined with a maximum likelihood approach using the particle density as a function of distance to the shower core. introducing quality cuts to isolate events with shower cores landing on the array, the reconstructed energy distribution is unfolded iteratively. the measured all-particle spectrum is consistent with a broken power law with an index of -2.49 ±0.01 prior to a break at (45.7 ±0.1 ) tev , followed by an index of -2.71 ±0.01 . the spectrum also represents a single measurement that spans the energy range between direct detection and ground-based experiments. as a verification of the detector response, the energy scale and angular resolution are validated by observation of the cosmic ray moon shadow's dependence on energy. | all-particle cosmic ray energy spectrum measured by the hawc experiment from 10 to 500 tev |
the experimental study of nuclear reactions of astrophysical interest is greatly facilitated by a low-background, high-luminosity setup. the laboratory for underground nuclear astrophysics (luna) 400kv accelerator offers ultra-low cosmic-ray induced background due to its location deep underground in the gran sasso national laboratory (infn-lngs), italy, and high intensity, 250-500μa, proton and α ion beams. in order to fully exploit these features, a high-purity, recirculating gas target system for isotopically enriched gases is coupled to a high-efficiency, six-fold optically segmented bismuth germanate (bgo) γ-ray detector. the beam intensity is measured with a beam calorimeter with constant temperature gradient. pressure and temperature measurements have been carried out at several positions along the beam path, and the resultant gas density profile has been determined. calibrated γ-intensity standards and the well-known ep = 278 kev 14n(p,γ)15o resonance were used to determine the γ-ray detection efficiency and to validate the simulation of the target and detector setup. as an example, the recently measured resonance at ep = 189.5 kev in the 22ne(p,γ)23na reaction has been investigated with high statistics, and the γ-decay branching ratios of the resonance have been determined. | a high-efficiency gas target setup for underground experiments, and redetermination of the branching ratio of the 189.5 kev 22ne(p,γ)23na resonance |
stars are the main factories of element production in the universe through a suite of complex and intertwined physical processes. such stellar alchemy is driven by multiple nuclear interactions that through eons have transformed the pristine, metal-poor ashes leftover by the big bang into a cosmos with 100 distinct chemical species. the products of stellar nucleosynthesis frequently get mixed inside stars by convective transport or through hydrodynamic instabilities, and a fraction of them is eventually ejected into the interstellar medium, thus polluting the cosmos with gas and dust. the study of the physics of the stars and their role as nucleosynthesis factories owes much to cross-fertilization of different, somehow disconnected fields, ranging from observational astronomy, computational astrophysics, and cosmochemistry to experimental and theoretical nuclear physics. few books have simultaneously addressed the multidisciplinary nature of this field in an engaging way suitable for students and young scientists. providing the required multidisciplinary background in a coherent way has been the driving force for stellar explosions: hydrodynamics and nucleosynthesis. written by a specialist in stellar astrophysics, this book presents a rigorous but accessible treatment of the physics of stellar explosions from a multidisciplinary perspective at the crossroads of computational astrophysics, observational astronomy, cosmochemistry, and nuclear physics. basic concepts from all these different fields are applied to the study of classical and recurrent novae, type i and ii supernovae, x-ray bursts and superbursts, and stellar mergers. the book shows how a multidisciplinary approach has been instrumental in our understanding of nucleosynthesis in stars, particularly during explosive events. | stellar explosions: hydrodynamics and nucleosynthesis |
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