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we use an updated version of simprop, a monte carlo simulation scheme for the propagation of ultra-high energy cosmic rays, to compute cosmogenic neutrino fluxes expected on earth in various scenarios. these fluxes are compared with the newly detected icecube events at pev energies and with recent experimental limits at eev energies of the pierre auger observatory. this comparison allows us to draw some interesting conclusions about the source models for ultra-high energy cosmic rays. we will show how the available experimental observations are almost at the level of constraining such models, mainly in terms of the injected chemical composition and cosmological evolution of sources. the results presented here will also be important in the evaluation of the discovery capabilities of the future planned ultra-high energy cosmic ray and neutrino observatories. | cosmogenic neutrinos and ultra-high energy cosmic ray models |
in the statistical framework of model-independent gaussian processes (gp), we search for the evidence of dynamical dark energy (dde) using the "joint light-curve analysis" (jla) type ia supernovae (sne ia) sample, the 30 latest cosmic chronometer data points (h(z)), planck's shift parameter from cosmic microwave background (cmb) anisotropies, the 156 latest hii galaxy measurements and 79 calibrated gamma-ray bursts (grbs). we find that the joint constraint from jla + h(z) + cmb + hii + grb supports the global measurement of h_0 by planck collaboration very much in the low redshift range z\in [0, 0.76] at the 2σ confidence level (c.l.), gives a cosmological constant crossing (quintom-like) equation of state (eos) of de at the 2σ c.l. and implies that the evolution of the late-time universe may be actually dominated by the dde. | searching for the evidence of dynamical dark energy |
massive cosmic neutrinos change the structure formation history by suppressing perturbations on small scales. weak lensing data from galaxy surveys probe the structure evolution and thereby can be used to constrain the total mass of the three active neutrinos. however, much of the information is at small scales where the dynamics are nonlinear. traditional approaches with second-order statistics thus fail to fully extract the information in the lensing field. in this paper, we study constraints on the neutrino mass sum using lensing peak counts, a statistic which captures non-gaussian information beyond the second order. we use the ray-traced weak lensing mocks from the cosmological massive neutrino simulations (massivenus) and apply large synoptic survey telescope-like noise. we discuss the effects of redshift tomography, the multipole cutoff ℓmax for the power spectrum, the smoothing scale for the peak counts, and constraints from peaks of different heights. we find that combining peak counts with the traditional lensing power spectrum can improve the constraint on the neutrino mass sum, ωm, and as by 39%, 32%, and 60%, respectively, over that from the power spectrum alone. we note that observational systematics such as baryonic effects, intrinsic alignments, and photometric redshift errors are not studied in this work, but will be an important next step. | constraining neutrino mass with tomographic weak lensing peak counts |
since its launch, the alpha magnetic spectrometer—02 (ams-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (cr) species ( $\bar{p}$ , e±, and nuclei, 1h-8o, 10ne, 12mg, 14si) which resulted in a number of breakthroughs. one of the latest long-awaited surprises is the spectrum of 26fe just published by ams-02. because of the large fragmentation cross section and large ionization energy losses, most of cr iron at low energies is local and may harbor some features associated with relatively recent supernova (sn) activity in the solar neighborhood. our analysis of the new ams-02 results, together with voyager 1 and ace-cris data, reveals an unexpected bump in the iron spectrum and in the fe/he, fe/o, and fe/si ratios at 1-2 gv, while a similar feature in the spectra of he, o, and si and in their ratios is absent, hinting at a local source of low-energy crs. the found excess extends the recent discoveries of radioactive 60fe deposits in terrestrial and lunar samples and in crs. we provide an updated local interstellar spectrum (lis) of iron in the energy range from 1 mev nucleon-1 to ∼10 tev nucleon-1. our calculations employ the galprop-helmod framework, which has proved to be a reliable tool in deriving the lis of cr $\bar{p}$ , e-, and nuclei z ≤ 28. | the discovery of a low-energy excess in cosmic-ray iron: evidence of the past supernova activity in the local bubble |
rare event search experiments using liquid xenon as target and detection medium require ultra-low background levels to fully exploit their physics potential. cosmic ray induced activation of the detector components and, even more importantly, of the xenon itself during production, transportation and storage at the earth's surface, might result in the production of radioactive isotopes with long half-lives, with a possible impact on the expected background. we present the first dedicated study on the cosmogenic activation of xenon after 345 days of exposure to cosmic rays at the jungfraujoch research station at 3470 m above sea level, complemented by a study of copper which has been activated simultaneously. we have directly observed the production of ^7be, ^{101}rh, ^{125}sb, ^{126}i and ^{127}xe in xenon, out of which only ^{125}sb could potentially lead to background for a multi-ton scale dark matter search. the production rates for five out of eight studied radioactive isotopes in copper are in agreement with the only existing dedicated activation measurement, while we observe lower rates for the remaining ones. the specific saturation activities for both samples are also compared to predictions obtained with commonly used software packages, where we observe some underpredictions, especially for xenon activation. | cosmogenic activation of xenon and copper |
the majorana demonstrator is an array of point-contact ge detectors fabricated from ge isotopically enriched to 88% in 76 ge to search for neutrinoless double beta decay. the processing of ge for germanium detectors is a well-known technology. however, because of the high cost of ge enriched in 76 ge special procedures were required to maximize the yield of detector mass and to minimize exposure to cosmic rays. these procedures include careful accounting for the material; shielding it to reduce cosmogenic generation of radioactive isotopes; and development of special reprocessing techniques for contaminated solid germanium, shavings, grindings, acid etchant and cutting fluids from detector fabrication. processing procedures were developed that resulted in a total yield in detector mass of 70%. however, none of the acid-etch solution and only 50% of the cutting fluids from detector fabrication were reprocessed. had they been processed, the projections for the recovery yield would be between 80% and 85%. maximizing yield is critical to justify a possible future ton-scale experiment. a process for recovery of germanium from the acid-etch solution was developed with yield of about 90%. all material was shielded or stored underground whenever possible to minimize the formation of 68ge by cosmic rays, which contributes background in the double-beta decay region of interest and cannot be removed by zone refinement and crystal growth. formation of 68ge was reduced by a significant factor over that in natural abundance detectors not protected from cosmic rays. | the processing of enriched germanium for the majorana demonstrator and r&d for a next generation double-beta decay experiment |
the absence of large cooling flows in cool core clusters appears to require self-regulated energy feedback by active galactic nuclei but the exact heating mechanism has not yet been identified. here, we analyse whether a combination of cosmic ray (cr) heating and thermal conduction can offset radiative cooling. to this end, we compile a large sample of 39 cool core clusters and determine steady state solutions of the hydrodynamic equations that are coupled to the cr energy equation. we find solutions that match the observed density and temperature profiles for all our clusters well. radiative cooling is balanced by cr heating in the cluster centres and by thermal conduction on larger scales, thus demonstrating the relevance of both heating mechanisms. our mass deposition rates vary by three orders of magnitude and are linearly correlated to the observed star formation rates. clusters with large mass deposition rates show larger cooling radii and require a larger radial extent of the cr injection function. interestingly, our sample shows a continuous sequence in cooling properties: clusters hosting radio mini haloes are characterized by the largest cooling radii, star formation and mass deposition rates in our sample and thus signal the presence of a higher cooling activity. the steady state solutions support the structural differences between clusters hosting a radio mini halo and those that do not. | cosmic ray heating in cool core clusters - i. diversity of steady state solutions |
amino acids are fundamental to life as we know them as the monomers of proteins and enzymes. they are also readily synthesized under a variety of plausible prebiotic conditions and are common in carbon-rich meteorites. thus, they represent a reasonable class of organics to target in the search for prebiotic chemistry or chemical evidence of life on mars. however, regardless of their origin, amino acids and other organic molecules present in near-surface regolith and rocks on mars can be degraded by exposure to cosmic rays that can penetrate to a depth of a few meters. we exposed several pure amino acids in dry and hydrated silicate mixtures and in mixtures of silicates with perchlorate salts to gamma radiation at various temperatures and radiation doses representative of the martian near-subsurface. we found that irradiation of amino acids mixed with dry silica powder increased the rate of amino acid radiolysis, with the radiolysis constants of amino acids in silicate mixtures at least a factor of 10 larger compared with the radiolysis constants of amino acids alone. the addition of perchlorate salts to the silicate samples or hydration of silicate samples further accelerated the rate of amino acid destruction during irradiation and increased the radiolysis constants by a factor of ∼1.5. our results suggest that even low-molecular-weight amino acids could degrade in just ∼20 million years in the top 10 cm of the martian surface regolith and rock, and even faster if the material contains elevated abundances of hydrated silicate minerals or perchlorates. we did not detect evidence of amino acid racemization after gamma radiation exposure of the samples, which indicates that the chirality of some surviving amino acids may still be preserved. our experimental results suggest serious challenges for the search of ancient amino acids and other potential organic biosignatures in the top 2 m of the martian surface. | rapid radiolytic degradation of amino acids in the martian shallow subsurface: implications for the search for extinct life |
relativistic millicharged particles (χq) have been proposed in various extensions to the standard model of particle physics. we consider the scenarios where they are produced at nuclear reactor core and via interactions of cosmic rays with the earth's atmosphere. millicharged particles could also be candidates for dark matter and become relativistic through acceleration by supernova explosion shock waves. the atomic ionization cross section of χq with matter are derived with the equivalent photon approximation. smoking-gun signatures with significant enhancement in the differential cross section are identified. new limits on the mass and charge of χq are derived, using data taken with a point-contact germanium detector with 500 g mass functioning at an energy threshold of 300 ev at the kuo-sheng reactor neutrino laboratory. | constraints on millicharged particles with low-threshold germanium detectors at kuo-sheng reactor neutrino laboratory |
we present a search for the synchrotron emission from the synchrotron cosmic web by cross-correlating 180-mhz radio images from the murchison widefield array with tracers of large-scale structure (lss). we use two versions of the radio image covering 21.76° × 21.76° with point sources brighter than 0.05 jy subtracted, with and without filtering of galactic emission. as tracers of the lss, we use the two micron all-sky survey and the wide-field infrared explorer redshift catalogues to produce galaxy number density maps. the cross-correlation functions all show peak amplitudes at 0°, decreasing with varying slopes towards zero correlation over a range of 1°. the cross-correlation signals include components from point source, galactic, and extragalactic diffuse emission. we use models of the diffuse emission from smoothing the density maps with gaussians of sizes 1-4 mpc to find limits on the cosmic web components. from these models, we find surface brightness 99.7 per cent upper limits in the range of 0.09-2.20 mjy beam-1 (average beam size of 2.6 arcmin), corresponding to 0.01-0.30 mjy arcmin-2. assuming equipartition between energy densities of cosmic rays and the magnetic field, the flux density limits translate to magnetic field strength limits of 0.03-1.98 μg, depending heavily on the spectral index. we conclude that for a 3σ detection of 0.1 μg magnetic field strengths via cross-correlations, image depths of sub-mjy to sub-μjy are necessary. we include discussion on the treatment and effect of extragalactic point sources and galactic emission, and next steps for building on this work. | low-frequency radio constraints on the synchrotron cosmic web |
we discuss the phenomenology of an mev-scale dirac fermion coupled to the standard model through a dark photon with kinetic mixing with the electromagnetic field. we compute the dark matter relic density and explore the interplay of direct detection and accelerator searches for dark photons. we show that precise measurements of the temperature and polarization power spectra of the cosmic microwave background radiation lead to stringent constraints, leaving a small window for the thermal production of this mev dark matter candidate. the forthcoming mev gamma-ray telescope e-astrogam will offer important and complementary opportunities to discover dark matter particles with masses below ~ 10 mev . lastly, we discuss how a late-time inflation episode and freeze-in production could conspire to yield the correct relic density while being consistent with existing and future constraints. | mev dark matter complementarity and the dark photon portal |
we report the detection of the radio afterglow of a long gamma-ray burst (grb) 111005a at 5-345 ghz, including very long baseline interferometry observations with a positional error of 0.2 mas. the afterglow position is coincident with the disc of a galaxy eso 58049 at z = 0.01326 (∼1″ from its centre), which makes grb 111005a the second-closest grb known to date, after grb 980425. the radio afterglow of grb 111005a was an order of magnitude less luminous than those of local low-luminosity grbs, and obviously less luminous than those of cosmological grbs. the radio flux was approximately constant and then experienced an unusually rapid decay a month after the grb explosion. similarly to only two other grbs, we did not find the associated supernovae (sne), despite deep near- and mid-infrared observations 1-9 days after the grb explosion, reaching ∼20 times fainter than other sne associated with grbs. moreover, we measured a twice-solar metallicity for the grb location. the low y-ray and radio luminosities, rapid decay, lack of a sn, and super-solar metallicity suggest that grb 111005a represents a rare class of grb that is different from typical core-collapse events. we modelled the spectral energy distribution of the grb 111005a host finding that it is a moderately star-forming dwarf galaxy, similar to the host of grb 980425. the existence of two local grbs in such galaxies is still consistent with the hypothesis that the grb rate is proportional to the cosmic star formation rate (sfr) density, but suggests that the grb rate is biased towards low sfrs. using the far-infrared detection of eso 580-49, we conclude that the hosts of both grbs 111005a and 980425 exhibit lower dust content than what would be expected from their stellar masses and optical colors. | the second-closest gamma-ray burst: sub-luminous grb 111005a with no supernova in a super-solar metallicity environment |
the precise observations of galactic cosmic ray fluxes of the secondary family, such as li, be, b, are expected to have significant implications on our understanding of the cosmic ray origin and propagation. here we employ the recent very precise measurements of those species by the alpha magnetic spectrometer on the international space station, together with their parent species (c and o), as well as the data collected by the voyager-1 spacecraft outside the heliosphere and the advanced composition explorer, to investigate the propagation of cosmic rays in the milky way. we consider the diffusion of cosmic rays plus reacceleration or convection effect during the propagation, and find that the reacceleration model can fit the data significantly better than the convection model. we further find that for the reacceleration model, the spectral hardenings of both the primary and secondary particles can be well described by the injection hardening without including additional propagation hardening. this is due to that the reacceleration effect results in a steeper secondary-to-primary ratio at low energies, and can thus naturally reproduce the fact that the secondary spectra harden more than the primary spectra found by ams-02. | secondary cosmic-ray nucleus spectra disfavor particle transport in the galaxy without reacceleration |
we study properties of magnetohydrodynamic (mhd) eigenmodes by decomposing the data of mhd simulations into linear mhd modes—namely, the alfvén, slow magnetosonic, and fast magnetosonic modes. we drive turbulence with a mixture of solenoidal and compressive driving while varying the alfvén mach number (ma), plasma β , and the sonic mach number from subsonic to transsonic. we find that the proportion of fast and slow modes in the mode mixture increases with increasing compressive forcing. this proportion of the magnetosonic modes can also become the dominant fraction in the mode mixture. the anisotropy of the modes is analyzed by means of their structure functions. the alfvén-mode anisotropy is consistent with the goldreich-sridhar theory. we find a transition from weak to strong alfvénic turbulence as we go from low to high ma. the slow-mode properties are similar to the alfvén mode. on the other hand, the isotropic nature of fast modes is verified in the cases where the fast mode is a significant fraction of the mode mixture. the fast-mode behavior does not show any transition in going from low to high ma. we find indications that there is some interaction between the different modes, and the properties of the dominant mode can affect the properties of the weaker modes. this work identifies the conditions under which magnetosonic modes can be a major fraction of turbulent astrophysical plasmas, including the regime of weak turbulence. important astrophysical implications for cosmic-ray transport and magnetic reconnection are discussed. | properties of magnetohydrodynamic modes in compressively driven plasma turbulence |
the gyro-resonant cosmic-ray (cr) streaming instability is believed to play a crucial role in cr transport, leading to the growth of alfvén waves at small scales that scatter crs, and impacts the interaction of crs with the interstellar medium (ism) on large scales. however, extreme scale separation (λ ≪ pc), low cr number density (n cr/n ism ∼ 10-9), and weak cr anisotropy (∼v a/c) pose strong challenges for proper numerical studies of this instability on a microphysical level. employing the recently developed magnetohydrodynamic particle-in-cell method, which has unique advantages to alleviate these issues, we conduct 1d simulations that quantitatively demonstrate the growth and saturation of the instability in the parameter regime consistent with realistic cr streaming in the large-scale ism. our implementation of the δf method dramatically reduces poisson noise and enables us to accurately capture wave growth over a broad spectrum equally shared between left- and right-handed alfvén modes. we are also able to accurately follow the quasi-linear diffusion of crs subsequent to wave growth, which is achieved by employing phase randomization across periodic boundaries. full isotropization of the crs in the wave frame requires the pitch angles of most crs to efficiently cross 90° and can be captured in simulations with relatively high wave amplitude and/or spatial resolution. we attribute this crossing to nonlinear wave-particle interaction (rather than mirror reflection) by investigating individual cr trajectories. we anticipate that our methodology will open up opportunities for future investigations that incorporate additional physics. | magnetohydrodynamic particle-in-cell simulations of the cosmic-ray streaming instability: linear growth and quasi-linear evolution |
we recently proposed that structured (spine-sheath) jets associated with bl lac objects could offer a suitable environment for the production of the extragalactic high-energy (e > 100 tev) neutrino recently revealed by icecube. our previous analysis was limited to low-power bl lac objects. we extend our preliminary study to the entire bl lac population, assuming that the entire diffuse emission is accounted for by these sources. the neutrino output from a single source depends on a relatively large number of parameters. however, for several of them we have constraints coming from observations and previous application of the structured jet model to blazar and radiogalaxy emission. the observed neutrino spectrum then fixes the remaining free parameters. we assume that the power of cosmic rays as well as the radiative luminosity of the sheath depends linearly on the jet power. in turn, we assume that the latter is well traced by the γ-ray luminosity. we exploit the bl lac γ-ray luminosity function and its cosmic evolution as recently inferred from fermi-lat data to derive the expected neutrino cumulative intensity from the entire bl lac population. when considering only the low-power bl lacs, a large cosmic ray power for each source is required to account for the neutrino flux. instead, if bl lacs of all powers produce neutrinos, the power demand decreases, and the required cosmic ray power becomes of the same order of the radiative jet power. in our scheme, the maximum energy of cosmic rays is constrained to be ≲ few pev by the lack of events above few pev. although such a value is obtained through a fine-tuning with the data, we show that it could be possibly related to the equilibrium between cooling and acceleration processes for high-energy cosmic rays. we also discuss the prospects for the direct association of icecube events with bl lacs, providing an estimate of the expected counts for the most promising sources. | high-energy cosmic neutrinos from spine-sheath bl lac jets |
the events recorded by argo-ybj in more than five years of data collection have been analyzed to determine the diffuse gamma-ray emission in the galactic plane at galactic longitudes 25° < l < 100° and galactic latitudes |b|\lt 5{}^\circ . the energy range covered by this analysis, from ∼350 gev to ∼2 tev, allows the connection of the region explored by fermi with the multi-tev measurements carried out by milagro. our analysis has been focused on two selected regions of the galactic plane, i.e., 40° < l < 100° and 65° < l < 85° (the cygnus region), where milagro observed an excess with respect to the predictions of current models. great care has been taken in order to mask the most intense gamma-ray sources, including the tev counterpart of the cygnus cocoon recently identified by argo-ybj, and to remove residual contributions. the argo-ybj results do not show any excess at sub-tev energies corresponding to the excess found by milagro, and are consistent with the predictions of the fermi model for the diffuse galactic emission. from the measured energy distribution we derive spectral indices and the differential flux at 1 tev of the diffuse gamma-ray emission in the sky regions investigated. | study of the diffuse gamma-ray emission from the galactic plane with argo-ybj |
weak shocks in the intracluster medium may accelerate cosmic-ray protons and cosmic-ray electrons differently depending on the angle between the upstream magnetic field and the shock normal. in this work, we investigate how shock obliquity affects the production of cosmic rays in high-resolution simulations of galaxy clusters. for this purpose, we performed a magnetohydrodynamical simulation of a galaxy cluster using the mesh refinement code enzo. we use lagrangian tracers to follow the properties of the thermal gas, the cosmic rays and the magnetic fields over time. we tested a number of different acceleration scenarios by varying the obliquity-dependent acceleration efficiencies of protons and electrons, and by examining the resulting hadronic γ-ray and radio emission. we find that the radio emission does not change significantly if only quasi-perpendicular shocks are able to accelerate cosmic-ray electrons. our analysis suggests that radio-emitting electrons found in relics have been typically shocked many times before z = 0. on the other hand, the hadronic γ-ray emission from clusters is found to decrease significantly if only quasi-parallel shocks are allowed to accelerate cosmic ray protons. this might reduce the tension with the low upper limits on γ-ray emission from clusters set by the fermi satellite. | testing cosmic ray acceleration with radio relics: a high-resolution study using mhd and tracers |
due to their late formation in cosmic history, clusters of galaxies are not fully in hydrostatic equilibrium and the gravitational pull of their mass at a given radius is expected not to be entirely balanced by the thermal gas pressure. turbulence may supply additional pressure, and recent (x-ray and sz) hydrostatic mass reconstructions claim a pressure support of ∼ 5-15 per cent of the total pressure at r200. in this work we show that, after carefully disentangling bulk from small-scale turbulent motions in high-resolution simulations of galaxy clusters, we can constrain which fraction of the gas kinetic energy effectively provides pressure support in the cluster's gravitational potential. while the ubiquitous presence of radial inflows in the cluster can lead to significant bias in the estimate of the non-thermal pressure support, we report that only a part of this energy effectively acts as a source of pressure, providing a support of the order of {∼ } 10{{ per cent}} of the total pressure at r200. | the turbulent pressure support in galaxy clusters revisited |
in the milky way (mw), cosmic rays (crs) are dynamically important in the interstellar medium (ism), contribute to hydrostatic balance, and may help regulate star formation. however, we know far less about the importance of crs in galaxies whose gas content or star formation rate (sfr) differ significantly from those of the mw. here, we construct self-consistent models for hadronic cr transport, losses, and contribution to pressure balance as a function of galaxy properties, covering a broad range of parameters from dwarfs to extreme starbursts. while the cr energy density increases from ~1 ev cm-3 to ~1 kev cm-3 over the range from sub-mw dwarfs to bright starbursts, strong hadronic losses render crs increasingly unimportant dynamically as the sfr surface density increases. in mw-like systems, cr pressure is typically comparable to turbulent gas and magnetic pressure at the galactic mid-plane, but the ratio of cr to gas pressure drops to ~10-3 in dense starbursts. galaxies also become increasingly cr calorimetric and gamma-ray bright in this limit. the degree of calorimetry at fixed galaxy properties is sensitive to the assumed model for cr transport, and in particular to the time crs spend interacting with neutral ism, where they undergo strong streaming losses. we also find that in some regimes of parameter space hydrostatic equilibrium discs cannot exist, and in paper ii of this series we use this result to derive a critical surface in the plane of star formation surface density and gas surface density beyond which crs may drive large-scale galactic winds. | cosmic rays across the star-forming galaxy sequence - i. cosmic ray pressures and calorimetry |
we present a study of the filamentary structure in the neutral atomic hydrogen (h i) emission at the 21 cm wavelength toward the galactic plane using the 16′.2-resolution observations in the h i 4π (hi4pi) survey. using the hessian matrix method across radial velocity channels, we identified the filamentary structures and quantified their orientations using circular statistics. we found that the regions of the milky way's disk beyond 10 kpc and up to roughly 18 kpc from the galactic center display h i filamentary structures predominantly parallel to the galactic plane. for regions at lower galactocentric radii, we found that the h i filaments are mostly perpendicular or do not have a preferred orientation with respect to the galactic plane. we interpret these results as the imprint of supernova feedback in the inner galaxy and galactic rotation and shear in the outer milky way. we found that the h i filamentary structures follow the galactic warp and flaring and that they highlight some of the variations interpreted as the effect of the gravitational interaction with satellite galaxies. in addition, the mean scale height of the filamentary structures is lower than that sampled by the bulk of the h i emission, thus indicating that the cold and warm atomic hydrogen phases have different scale heights in the outer galaxy. finally, we found that the fraction of the column density in h i filaments is almost constant up to approximately 18 kpc from the galactic center. this is possibly a result of the roughly constant ratio between the cold and warm atomic hydrogen phases inferred from the h i absorption studies. our results indicate that the h i filamentary structures provide insight into the dynamical processes shaping the galactic disk. their orientations record how and where the stellar energy input, the galactic fountain process, the cosmic ray diffusion, and the gas accretion have molded the diffuse interstellar medium in the galactic plane. | the galactic dynamics revealed by the filamentary structure in atomic hydrogen emission |
life most likely started during the hadean eon; however, the environmental conditions which contributed to the complexity of its chemistry are poorly known. a better understanding of various environmental conditions, including global (heliospheric) and local (atmospheric, surface, and oceanic), along with the internal dynamic conditions of the early earth, are required to understand the onset of abiogenesis. herein, we examine the contributions of galactic cosmic rays (gcrs) and solar energetic particles (seps) associated with superflares from the young sun to the formation of amino acids and carboxylic acids in weakly reduced gas mixtures representing the early earth's atmosphere. we also compare the products with those introduced by lightning events and solar ultraviolet light (uv). in a series of laboratory experiments, we detected and characterized the formation of amino acids and carboxylic acids via proton irradiation of a mixture of carbon dioxide, methane, nitrogen, and water in various mixing ratios. these experiments show the detection of amino acids after acid hydrolysis when 0.5% (v/v) of initial methane was introduced to the gas mixture. in the set of experiments with spark discharges (simulation of lightning flashes) performed for the same gas mixture, we found that at least 15% methane was required to detect the formation of amino acids, and no amino acids were detected in experiments via uv irradiation, even when 50% methane was used. carboxylic acids were formed in non-reducing gas mixtures (0% methane) by proton irradiation and spark discharges. hence, we suggest that gcrs and sep events from the young sun represent the most effective energy sources for the prebiotic formation of biologically important organic compounds from weakly reducing atmospheres. since the energy flux of space weather, which generated frequent seps from the young sun in the first 600 million years after the birth of the solar system, was expected to be much greater than that of gcrs, we conclude that sep-driven energetic protons are the most promising energy sources for the prebiotic production of bioorganic compounds in the atmosphere of the hadean earth. | formation of amino acids and carboxylic acids in weakly reducing planetary atmospheres by solar energetic particles from the young sun |
we present a range of unbroken power-law fits to the astrophysical-neutrino spectrum consistent with the most recent published icecube data at the 68% confidence level. assuming that the neutrinos originate in decays of π mesons, we estimate accompanying gamma-ray fluxes for various distributions of sources, taking propagation effects into account. we then briefly discuss existing experimental results constraining pev to eev diffuse gamma-ray flux and their systematic uncertainties. several scenarios are marginally consistent both with the kaskade and casa-mia upper limits at 10152-1016 ev and with the eas-msu tentative detection at ∼1017 ev, given large systematic errors of the measurements. future searches for the diffuse gamma-ray background at sub-pev to sub-eev energies just below present upper limits will give a crucial diagnostic tool for distinguishing between the galactic and extragalactic models of the origin of the icecube events. | icecube astrophysical neutrinos without a spectral cutoff and 1015-1017 ev cosmic gamma radiation |
a spherical-symmetric gamma-ray emission from {the inner region of the galaxy (at least up to roughly 10° in latitude and longitude)} has been recently identified in fermi-lat data, and initially associated to dark matter particle annihilations. guided by the evidence for a high gas density in the inner kpc of the galaxy correlated with a very large supernova rate, and hence with ongoing cosmic-ray acceleration, we investigate instead the possibility of addressing this excess in terms of ordinary cosmic-ray sources and standard steady-state diffusion. we {alter the source term, and consistently the correlated gamma-ray emissions, in the context of a template-fitting analysis. we focus on a region of interest (roi) defined as: |l| < 20°; 2° < |b| < 20°, with l and b the galactic longitude and latitude coordinates.} we analyze in detail the overall goodness of the fit of our framework, and perform a detailed direct comparison against data examining profiles in different directions. remarkably, the test statistic of the fit related to our scenario turns out to be as good as the dark matter one in the roi here considered. | towards a realistic astrophysical interpretation of the gamma-ray galactic center excess |
a muon scattering tomography system which uses extruded plastic scintillator bars for muon tracking and a dedicated muon spectrometer that measures scattering through steel slabs has been constructed and successfully tested. the atmospheric muon detection efficiency is measured to be 97% per plane on average and the average intrinsic hit resolution is 2.5 mm. in addition to creating a variety of three-dimensional images of objects of interest, a quantitative study has been carried out to investigate the impact of including muon momentum measurements when attempting to detect high-density, high-z material. as expected, the addition of momentum information improves the performance of the system. for a fixed data-taking time of 60 s and a fixed false positive fraction, the probability to detect a target increases when momentum information is used. this is the first demonstration of the use of muon momentum information from dedicated spectrometer measurements in muon scattering tomography. | a plastic scintillator-based muon tomography system with an integrated muon spectrometer |
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 $110\,\mathrm{gev/}c$, represent the first direct determination of the antiproton production cross-section in ${\rm p he}$ collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments. | measurement of antiproton production in ${\\rm p he}$ collisions at $\\sqrt{s_{nn}}=110$ gev |
motivated by the recently reported diphoton resonance at 750 gev, we study a new axion-like bosonic portal model of dark matter physics. when the resonance particle is identified as the pseudo-scalar mediator, via which the standard model sector would interact with the dark matter sector, the data from collider physics would provide profound implications to dark matter phenomenology. in this paper, we first identify the preferred parameter space of the suggested portal model from the results of the lhc run with √{ s } = 13 tev, and then we examine the dark matter signature taking into account the data from cosmic-ray experiments including fermi-lat dwarf galaxy γ-ray search, hess γ-line search, and future cta diffuse γ-ray and γ-line searches. | indirect signature of dark matter with the diphoton resonance at 750 gev |
we carry out a suite of simulations of the evolution of cosmic-ray (cr) driven, radiatively cooled cold clouds embedded in hot material, as found in galactic outflows. in such interactions, crs stream toward the cloud at the alfvén speed, which decreases dramatically at the cloud boundary, leading to a bottleneck in which pressure builds up in front of the cloud. at the same time, crs stream along the sides of the cloud, forming a boundary layer where large filaments develop. shear in this boundary layer is the primary mode of cloud destruction, which is relatively slow in all cases, but slowest in the cases with the lowest alfvén speeds. thus, the cr pressure in the bottleneck region has sufficient time to accelerate the cold clouds efficiently. furthermore, radiative cooling has relatively little impact on these interactions. our simulations are two-dimensional and limited by a simplified treatment of cr dynamics, the neglect of cr heating, and an idealized magnetic field geometry. nevertheless, our results suggest that crs, when acting as the primary source of momentum input, are capable of accelerating clouds to velocities comparable to those observed in galaxy outflows. | the launching of cold clouds by galaxy outflows. iv. cosmic-ray-driven acceleration |
observations of extended gamma-ray emission around galactic cosmic-ray (cr) sources can be used as novel probes of interstellar magnetic fields. using very high energy gamma-ray data from the hawc observatory, we place constraints on the properties of the magnetic turbulence within ≈25 pc from geminga. we inject and propagate individual cr electrons in 3d realizations of turbulent magnetic fields, calculate the resulting gamma-ray emission, and compare with hawc measurements of this region. we find that hawc data are compatible with expectations for kolmogorov or kraichnan turbulence and can be well fitted for reasonable coherence lengths and strengths of the turbulence, despite implying a cr diffusion coefficient significantly smaller than those suggested by galactic cr propagation codes. the best fit is found for a coherence length lc ≈ 1 pc and a magnetic field strength b_rms ≈ 3 μg, and the preferred value for lc increases with brms. moreover, the apparent lack of strong asymmetries in the observed emission allows us to constrain the coherence length to lc ≲ 5 pc in this region. | constraining the properties of the magnetic turbulence in the geminga region using hawc γ-ray data |
we use chandra x-ray data to measure the metallicity of the intracluster medium (icm) in 245 massive galaxy clusters selected from x-ray and sunyaev-zel'dovich (sz) effect surveys, spanning redshifts 0 < z < 1.2. metallicities were measured in three different radial ranges, spanning cluster cores through their outskirts. we explore trends in these measurements as a function of cluster redshift, temperature and surface brightness 'peakiness' (a proxy for gas cooling efficiency in cluster centres). the data at large radii (0.5-1 r500) are consistent with a constant metallicity, while at intermediate radii (0.1-0.5 r500) we see a late-time increase in enrichment, consistent with the expected production and mixing of metals in cluster cores. in cluster centres, there are strong trends of metallicity with temperature and peakiness, reflecting enhanced metal production in the lowest entropy gas. within the cool-core/sharply peaked cluster population, there is a large intrinsic scatter in central metallicity and no overall evolution, indicating significant astrophysical variations in the efficiency of enrichment. the central metallicity in clusters with flat surface brightness profiles is lower, with a smaller intrinsic scatter, but increases towards lower redshifts. our results are consistent with other recent measurements of icm metallicity as a function of redshift. they reinforce the picture implied by observations of uniform metal distributions in the outskirts of nearby clusters, in which most of the enrichment of the icm takes place before cluster formation, with significant later enrichment taking place only in cluster centres, as the stellar populations of the central galaxies evolve. | the metallicity of the intracluster medium over cosmic time: further evidence for early enrichment |
in the spring of 2017 an er-2 aircraft campaign was undertaken over continental united states to observe energetic radiation from thunderstorms and lightning. the payload consisted of a suite of instruments designed to detect optical signals, electric fields, and gamma rays from lightning. starting from georgia, usa, 16 flights were performed, for a total of about 70 flight hours at a cruise altitude of 20 km. of these, 45 flight hours were over thunderstorm regions. an analysis of two gamma ray glow events that were observed over colorado at 21:47 ut on 8 may 2017 is presented. we explore the charge structure of the cloud system, as well as possible mechanisms that can produce the gamma ray glows. the thundercloud system we passed during the gamma ray glow observation had strong convection in the core of the cloud system. electric field measurements combined with radar and radio measurements suggest an inverted charge structure, with an upper negative charge layer and a lower positive charge layer. based on modeling results, we were not able to unambiguously determine the production mechanism. possible mechanisms are either an enhancement of cosmic background locally (above or below 20 km) by an electric field below the local threshold or an enhancement of the cosmic background inside the cloud but then with normal polarity and an electric field well above the relativistic runaway electron avalanche threshold. | gamma ray glow observations at 20-km altitude |
concentration is one of the key dark matter halo properties that could drive the scatter in the stellar-to-halo mass relation of massive clusters. we derive robust photometric stellar masses for a sample of brightest central galaxies (bcgs) in sdss redmapper clusters at 0.17 < z < 0.3, and split the clusters into two equal-halo mass subsamples by their bcg stellar mass $m_*^{\mathrm{bcg}}$. the weak lensing profiles δς of the two cluster subsamples exhibit different slopes on scales below $1\, h^{-1}\, {\mathrm{mpc}}$. to interpret such discrepancy, we perform a comprehensive bayesian modelling of the two δς profiles by including different levels of miscentring effects between the two subsamples as informed by x-ray observations. we find that the two subsamples have the same average halo mass of $1.74\times 10^{14}\, h^{-1}\, \mathrm{m}_{\odot }$, but the concentration of the low-$m_*^{\mathrm{bcg}}$ clusters is $5.87_{-0.60}^{+0.77}$, ~1.5σ smaller than that of their high-$m_*^{\mathrm{bcg}}$ counterparts ($6.95_{-0.66}^{+0.78}$). furthermore, both cluster weak lensing and cluster-galaxy cross-correlations indicate that the large-scale bias of the low-$m_*^{\mathrm{bcg}}$, low-concentration clusters are ${\sim}10{{\ \rm per\ cent}}$ higher than that of the high-$m_*^{\mathrm{bcg}}$, high-concentration systems, hence possible evidence of the cluster assembly bias effect. our results reveal a remarkable physical connection between the stellar mass within $20{-}30\, h^{-1}\, {\mathrm{kpc}}$, the dark matter mass within ${\sim}200\, h^{-1}\, {\mathrm{kpc}}$, and the cosmic overdensity on scales above $10\, h^{-1}\, {\mathrm{mpc}}$, enabling a key observational test of theories of co-evolution between massive clusters and their central galaxies. | does concentration drive the scatter in the stellar-to-halo mass relation of galaxy clusters? |
cosmic-ray transport on galactic scales depends on the detailed properties of the magnetized, multiphase interstellar medium (ism). in this work, we postprocess a high-resolution tigress magnetohydrodynamic simulation modeling a local galactic disk patch with a two-moment fluid algorithm for cosmic-ray transport. we consider a variety of prescriptions for the cosmic rays, from a simple, purely diffusive formalism with constant scattering coefficient, to a physically motivated model in which the scattering coefficient is set by the critical balance between streaming-driven alfvén wave excitation and damping mediated by local gas properties. we separately focus on cosmic rays with kinetic energies of ~1 gev (high-energy) and ~30 mev (low energy), respectively important for ism dynamics and chemistry. we find that simultaneously accounting for advection, streaming, and diffusion of cosmic rays is crucial for properly modeling their transport. advection dominates in the high-velocity, low-density hot phase, while diffusion and streaming are more important in higher-density, cooler phases. our physically motivated model shows that there is no single diffusivity for cosmic-ray transport: the scattering coefficient varies by four or more orders of magnitude, maximal at density nh ~ 0.01 cm-3. the ion-neutral damping of alfvén waves results in strong diffusion and nearly uniform cosmic-ray pressure within most of the mass of the ism. however, cosmic rays are trapped near the disk midplane by the higher scattering rate in the surrounding lower-density, higher-ionization gas. the transport of high-energy cosmic rays differs from that of low-energy cosmic rays, with less effective diffusion and greater energy losses for the latter. | cosmic-ray transport in simulations of star-forming galactic disks |
recent cosmic-ray measurements are challenging our models of propagation in the galaxy. a good characterization of the secondary cosmic rays (b, be, li and sub-iron species) is crucial to constrain these models and exploit the precision of modern cr experiments. in this work, a markov chain monte carlo analysis has been implemented to fit the experimental flux ratios between b, be and li and their flux ratios to the primary cosmic-ray nuclei c and o. we have fitted the data using two different parametrizations for the spallation cross sections. the uncertainties in the evaluation of the spectra of these secondary cosmic rays, due to spallation cross sections, have been taken into account by introducing scale factors as nuisance parameters in the fits, assuming that this uncertainty is mostly due to the normalization of the cross sections parametrizations. we have also tested two different formulations for the diffusion coefficient, which differ in the origin of the high energy hardening (~ 200 gev/n) of cosmic rays. additionally, two different approaches are used to scale the cross sections, one based on a combined analysis of all the species ("combined" analysis) and the other reproducing the high energy spectra of the secondary-to-secondary flux ratios of be/b, li/b, li/be ("scaled" analysis). this allows us to make a better comparison between the propagation parameters inferred from the cross sections parametrizations tested in this work. this novel analysis has been successfully implemented using the numerical code dragon2 dedicated to cosmic-ray propagation to reproduce the cosmic-ray nuclei data up to z=14 from the ams-02 experiment. in general, it is found that the ratios of li favor a harder spectral index of the diffusion coefficient, but compatible with the other ratios inside the observed 2σ uncertainties. in addition, it is shown that, including these scale factors, the secondary-to-primary flux ratios can be simultaneously reproduced, obtaining that the scale factor associated to the cross sections of boron production is the lowest one, whereas that associated to li production is the largest one. | markov chain monte carlo analyses of the flux ratios of b, be and li with the dragon2 code |
the cosmic formation rate of long gamma-ray bursts (lgrbs) encodes the evolution, across cosmic times, of the properties of their progenitors and of their environment. the lgrb formation rate and the luminosity function, with its redshift evolution, are derived by reproducing the largest sets of observations collected over the last four decades, namely the observer-frame prompt emission properties of the grb samples detected by the fermi and compton gamma ray observatory satellites and the redshift, luminosity, and energy distributions of the flux-limited, redshift-complete samples of grbs detected by swift. the model that best reproduces all these constraints consists of a grb formation rate increasing with redshift ∝(1 + z)3.2, i.e., steeper than the star formation rate, up to z ~ 3, followed by a decrease ∝(1 + z)-3. on top of this, our model also predicts a moderate evolution of the characteristic luminosity function break ∝(1 + z)0.6. models with only luminosity or rate evolution are excluded at >5σ significance. the cosmic rate evolution of lgrbs is interpreted as their preference for occurring in environments with metallicity $12+\mathrm{log}({\rm{o}}/{\rm{h}})\lt 8.6$ , consistent with theoretical models and host galaxy observations. the lgrb rate at z = 0, accounting for their collimation, is ${\rho }_{0}\,=\,{79}_{-33}^{+57}$ gpc-3 yr-1 (68% confidence interval). this corresponds to ~1% of broad-line type ibc supernovae producing a successful jet in the local universe. this fraction increases up to ~7% at z ≥ 3. finally, we estimate that at least ≈0.2-0.7 yr-1 of the swift- and fermi-detected bursts at z < 0.5 are jets observed slightly off-axis. | the cosmic history of long gamma-ray bursts |
deformed relativistic kinematics is a framework which captures effects, that are expected from particles and fields propagating on a quantum spacetime, effectively. they are formulated in terms of a modified dispersion relation and a modified momentum conservation equation. in this work we use finsler geometry to formulate deformed relativistic kinematics in terms of particle velocities. the relation between the finsler geometric velocity dependent formulation and the original momentum dependent formulation allows us to construct deformed lorentz transformations between arbitrary frames. moreover, we find the corresponding compatible momentum conservation equation to first order in the planck scale deformation of special relativity based on the κ-poincaré algebra in the bicrossproduct basis. we find that the deformed lorentz transformations, as well as the deformed time dilation factor, contain terms that scale with the energy of the particle under consideration to the fourth power. we derive how the distributions of decay products are affected when the deformed relativity principle is satisfied and find, for the case of a pion decaying into a neutrino and a muon, that the ratio of expected neutrinos to muons with a certain energy is just slightly modified when compared to the predictions based on special relativity. we also discuss the phenomenological consequences of this framework for cosmic-ray showers in the atmosphere. | two-body decays in deformed relativity |
cosmic gamma rays are a valid probe to search for fundamental physics. some of these exotic and exciting scenarios are the subject of this contribution to the book. all current imaging atmospheric cherenkov telescopes (iacts) have invested a great deal of time and resources in scouting these out. in this chapter, we focus on the case of indirect search for weakly interacting massive particles (sec. 8.1) and that of search for axion-like particles (sec. 8.2). we continue with less debated, yet interesting studies on the search for primordial black holes (sec. 8.3), tau-neutrinos (8.4), and magnetic monopoles (8.5). other scenarios of fundamental physics like the search for lorentz invariance violations are treated elsewhere in the book. we structured the contribution providing a self-contained (yet minimal) theoretical framework, as well as a complete report of all iacts' published contribution to the topics under consideration. our aim is to provide a reference review as well as take a photograph of the effort of the current generation of iacts and the challenges taken, in preparation of the next-generation instrument to come, the cherenkov telescope array. | fundamental physics searches with iacts |
molecular gas is believed to be the fuel for star formation and nuclear activity in seyfert galaxies. to explore the role of magnetic fields in funneling molecular gas into the nuclear region, measurements of the magnetic fields embedded in molecular gas are needed. by applying the new velocity gradient technique (vgt) to co isotopolog data from the atacama large millimeter/submillimeter array and the plateau de bure interferometer arcsecond whirlpool survey, we obtain the first detection of co-associated magnetic fields in several nearby seyfert galaxies and their unprecedented high-resolution magnetic field maps. the vgt-measured magnetic fields in molecular gas globally agree with those inferred from existing hawc+ dust polarization and very large array synchrotron polarization. an overall good alignment between the magnetic fields traced by vgt-co and by synchrotron polarization may support the correlation between star formation and cosmic-ray generation. we find that the magnetic fields traced by vgt-co have a significant radial component in the central regions of most seyferts in our sample, where efficient molecular gas inflows or outflow may occur. in particular, we find local misalignment between the magnetic fields traced by co and dust polarization within the nuclear ring of ngc 1097, and the former aligns with the central bar's orientation. this misalignment reveals different magnetic field configurations in different gas phases and may provide an observational diagnostic for the ongoing multiphase fueling of seyfert activity. | role of magnetic fields in fueling seyfert nuclei |
massive stars blow powerful winds and eventually explode as supernovae. by doing so, they inject energy and momentum in the circumstellar medium, which is pushed away from the star and piles up to form a dense and expanding shell of gas. the effect is larger when many massive stars are grouped together in bound clusters or associations. large cavities form around clusters as a result of the stellar feedback on the ambient medium. they are called superbubbles and are characterised by the presence of turbulent and supersonic gas motions. this makes star clusters ideal environments for particle acceleration, and potential contributors to the observed galactic cosmic ray intensity. the acceleration of particles at star clusters and in their surroundings may provide a major contribution to the observed cr flux. moreover, it may explain the fine structures observed in the chemical composition of these particles, and possibly provide a solution to the puzzle of the origin of cosmic rays of energies in the pev range and beyond. | star clusters as cosmic ray accelerators |
the fermi large area telescope (lat) discovery that classical novae produce ≳100 mev gamma-rays establishes that shocks and relativistic particle acceleration are key features of these events. these shocks are likely to be radiative due to the high densities of the nova ejecta at early times coincident with the gamma-ray emission. thermal x-rays radiated behind the shock are absorbed by neutral gas and reprocessed into optical emission, similar to type iin (interacting) supernovae. gamma-rays are produced by collisions between relativistic protons with the nova ejecta (hadronic scenario) or inverse compton/bremsstrahlung emission from relativistic electrons (leptonic scenario), where in both scenarios the efficiency for converting relativistic particle energy into lat gamma-rays is at most a few tens of per cent. the measured ratio of gamma-ray and optical luminosities, lγ/lopt, thus sets a lower limit on the fraction of the shock power used to accelerate relativistic particles, ɛnth. the measured value of lγ/lopt for two classical novae, v1324 sco and v339 del, constrains ɛnth ≳ 10-2 and ≳10-3, respectively. leptonic models for the gamma-ray emission are disfavoured given the low electron acceleration efficiency, ɛnth ∼ 10-4-10-3, inferred from observations of galactic cosmic rays and particle-in-cell numerical simulations. a fraction fsh ≳ 100(ɛnth/0.01)-1 and ≳10(ɛnth/0.01)-1 per cent of the optical luminosity is powered by shocks in v1324 sco and v339 del, respectively. such high fractions challenge standard models that instead attribute all nova optical emission to the direct outwards transport of thermal energy released near the white dwarf surface. we predict hard ∼10-100 kev x-ray emission coincident with the lat emission, which should be detectable by nustar or astro-h, even at times when softer ≲10 kev emission is absorbed by neutral gas ahead of the shocks. | gamma-ray novae as probes of relativistic particle acceleration at non-relativistic shocks |
we report a search for light dark matter produced through the cascading decay of η mesons, which are created as a result of inelastic collisions between cosmic rays and earth's atmosphere. we introduce a new and general framework, publicly accessible, designed to address boosted dark matter specifically, with which a full and dedicated simulation including both elastic and quasielastic processes of earth attenuation effect on the dark matter particles arriving at the detector is performed. in the pandax-4t commissioning data of 0.63 tonne .year exposure, no significant excess over background is observed. the first constraints on the interaction between light dark matter generated in the atmosphere and nucleus through a light scalar mediator are obtained. the lowest excluded cross section is set at 5.9 ×10-37 cm2 for a dark matter mass of 0.1 mev /c2 and mediator mass of 300 mev /c2 . the lowest upper limit of η to the dark matter decay branching ratio is 1.6 ×10-7. | search for light dark matter from the atmosphere in pandax-4t |
the origin and nature of extreme energy cosmic rays (eecrs), which have energies above the 5\cdot10^{19} ev—the greisen-zatsepin-kuzmin (gzk) energy limit, is one of the most interesting and complicated problems in modern cosmic-ray physics. existing ground-based detectors have helped to obtain remarkable results in studying cosmic rays before and after the gzk limit, but have also produced some contradictions in our understanding of cosmic ray mass composition. moreover, each of these detectors covers only a part of the celestial sphere, which poses problems for studying the arrival directions of eecrs and identifying their sources. as a new generation of eecr space detectors, tus (tracking ultraviolet set-up), klypve and jem-euso, are intended to study the most energetic cosmic-ray particles, providing larger, uniform exposures of the entire celestial sphere. the tus detector, launched on board the lomonosov satellite on april 28, 2016 from vostochny cosmodrome in russia, is the first of these. it employs a single-mirror optical system and a photomultiplier tube matrix as a photo-detector and will test the fluorescent method of measuring eecrs from space. utilizing the earth's atmosphere as a huge calorimeter, it is expected to detect eecrs with energies above 10^{20} ev. it will also be able to register slower atmospheric transient events: atmospheric fluorescence in electrical discharges of various types including precipitating electrons escaping the magnetosphere and from the radiation of meteors passing through the atmosphere. we describe the design of the tus detector and present results of different ground-based tests and simulations. | the tus detector of extreme energy cosmic rays on board the lomonosov satellite |
the hitomi x-ray satellite has provided the first direct measurements of the plasma velocity dispersion in a galaxy cluster. it finds a relatively “quiescent” gas with a line-of-sight velocity dispersion {σ }v,{los}≃ 160 {km} {{{s}}}-1, at 30-60 kpc from the cluster center. this is surprising given the presence of jets and x-ray cavities that indicates on-going activity and feedback from the active galactic nucleus (agn) at the cluster center. using a set of mock hitomi observations generated from a suite of state-of-the-art cosmological cluster simulations, and an isolated but higher resolution simulation of gas physics in the cluster core, including the effects of cooling and agn feedback, we examine the likelihood of hitomi detecting a cluster with the observed velocities. as long as the perseus has not experienced a major merger in the last few gigayears, and agn feedback is operating in a “‘gentle” mode, we reproduce the level of gas motions observed by hitomi. the frequent mechanical agn feedback generates net line-of-sight velocity dispersions ∼ 100{--}200 {km} {{{s}}}-1, bracketing the values measured in the perseus core. the large-scale velocity shear observed across the core, on the other hand, is generated mainly by cosmic accretion such as mergers. we discuss the implications of these results for agn feedback physics and cluster cosmology and progress that needs to be made in both simulations and observations, including a hitomi re-flight and calorimeter-based instruments with higher spatial resolution. | physical origins of gas motions in galaxy cluster cores: interpreting hitomi observations of the perseus cluster |
a flux of cosmic rays (crs) propagating through a diffuse ionized gas can excite mhd waves, thus generating magnetic disturbances. we propose a generic model of cr penetration into molecular clouds through their diffuse envelopes, and identify the leading physical processes controlling their transport on the way from a highly ionized interstellar medium to the dense interior of the cloud. the model allows us to describe a transition between a free streaming of crs and their diffusive propagation, determined by the scattering on the self-generated disturbances. a self-consistent set of equations, governing the diffusive transport regime in an envelope and the mhd turbulence generated by the modulated cr flux, is characterized by two dimensionless numbers. we demonstrate a remarkable mutual complementarity of different mechanisms leading to the onset of the diffusive regime, which results in a universal energy spectrum of the modulated crs. in conclusion, we briefly discuss implications of our results for several fundamental astrophysical problems, such as the spatial distribution of crs in the galaxy as well as the ionization, heating, and chemistry in dense molecular clouds. this paper is dedicated to the memory of prof. vadim tsytovich. | penetration of cosmic rays into dense molecular clouds: role of diffuse envelopes |
the cosine-100 dark matter search experiment has started taking physics data with the goal of performing an independent measurement of the annual modulation signal observed by dama/libra. a muon detector was constructed by using plastic scintillator panels in the outermost layer of the shield surrounding the cosine-100 detector. it detects cosmic ray muons in order to understand the impact of the muon annual modulation on dark matter analysis. assembly and initial performance tests of each module have been performed at a ground laboratory. the installation of the detector in the yangyang underground laboratory (y2l) was completed in the summer of 2016. using three months of data, the muon underground flux was measured to be 328 ± 1(stat.)± 10(syst.) muons/m2/day. in this report, the assembly of the muon detector and the results from the analysis are presented. | muon detector for the cosine-100 experiment |
we present a measurement of the atmospheric νe spectrum at energies between 0.1 and 100 tev using data from the first year of the complete icecube detector. atmospheric νe originate mainly from the decays of kaons produced in cosmic-ray air showers. this analysis selects 1078 fully contained events in 332 days of live time, and then identifies those consistent with particle showers. a likelihood analysis with improved event selection extends our previous measurement of the conventional νe fluxes to higher energies. the data constrain the conventional νe flux to be 1. 3-0.3+0.4 times a baseline prediction from a honda's calculation, including the knee of the cosmic-ray spectrum. a fit to the kaon contribution (ξ ) to the neutrino flux finds a kaon component that is ξ =1. 3-0.4+0.5 times the baseline value. the fitted/measured prompt neutrino flux from charmed hadron decays strongly depends on the assumed astrophysical flux and shape. if the astrophysical component follows a power law, the result for the prompt flux is 0. 0-0.0+3.0 times a calculated flux based on the work by enberg, reno, and sarcevic. | measurement of the atmospheric νe spectrum with icecube |
we derive, adopting a direct method, the luminosity function and the formation rate of long gamma ray bursts through a complete, flux-limited, sample of swift bursts which has a high level of completeness in redshift z (~82%). we parametrise the redshift evolution of the grb luminosity as l = l0(1 + z)k and we derive k = 2.5, consistently with recent estimates. the de-evolved luminosity function φ(l0) of grbs can be represented by a broken power law with slopes a = -1.32 ± 0.21 and b = -1.84 ± 0.24 below and above, respectively, a break luminosity l0,b = 1051.45±0.15 erg/s. under the hypothesis of luminosity evolution we find that the grb formation rate increases with redshift up to z ~ 2, where it peaks, and then decreases in agreement with the shape of the cosmic star formation rate. we test the direct method through numerical simulations and we show that if it is applied to incomplete (both in redshift and/or flux) grb samples it can misleadingly result in an excess of the grb formation rate at low redshifts. | the rate and luminosity function of long gamma ray bursts |
nature is providing particles with energies exceeding 100 eev. their existence imposes immediate questions: are they ordinary particles, accelerated in extreme astrophysical environments, or are they annihilation or decay products of super-heavy dark matter or other exotic objects? if the particles are accelerated in extreme astrophysical environments, are their sources related to those of high-energy neutrinos, gamma rays, and/or gravitational waves, such as the recently observed mergers of compact objects? the particles can also be used to study physics processes at extreme energies; is lorentz invariance still valid? are the particles interacting according to the standard model or are there new physics processes? the particles can be used to study hadronic interactions (qcd) in the kinematic forward direction; what is the cross section of protons at center-of-mass energies $\sqrt{s} > 100$ tev? these questions are addressed at present by installations like the telescope array and the pierre auger observatory. after the year 2030, a next-generation observatory will be needed to study the physics and properties of the highest-energy particles in nature, building on the knowledge harvested from the existing observatories. it should have an aperture at least an order of magnitude bigger than the existing observatories. recently, more than 200 scientists from around the world came together to discuss the future of the field of multi-messenger astroparticle physics beyond the year 2030. ideas have been discussed towards the physics case and possible scenarios for detection concepts of the global cosmic ray observatory - gcos. a synopsis of the key results discussed during the brainstorming workshop will be presented. | gcos - the global cosmic ray observatory |
starburst galaxies are well-motivated astrophysical emitters of high-energy gamma rays. they are well-known cosmic-ray "reservoirs," thanks to their expected large magnetic field turbulence which confine high-energy protons for ∼105 years . over such long times, cosmic-ray transport can be significantly affected by scatterings with sub-gev dark matter. here we point out that this scattering distorts the cosmic-ray spectrum, and the distortion can be indirectly observed by measuring the gamma rays produced by cosmic rays via hadronic collisions. present gamma-ray data show no sign of such a distortion, leading to stringent bounds on the cross section between protons and dark matter. these are highly complementary with current bounds and have large room for improvement with the future gamma-ray measurements in the 0.1-10 tev range from the cherenkov telescope array, which can strengthen the limits by as much as 2 orders of magnitude. | starburst galactic nuclei as light dark matter laboratories |
using data obtained with neutron monitors and space-borne instruments, we analyzed the second ground-level enhancement (gle) of solar cycle 24, namely the event of 10 september 2017 (gle 72), and derived the spectral and angular characteristics of associated gle particles. we employed a new neutron-monitor yield function and a recently proposed model based on an optimization procedure. the method consists of simulating particle propagation in a model magnetosphere in order to derive the cutoff rigidity and neutron-monitor asymptotic directions. subsequently, the rigidity spectrum and anisotropy of gle particles are obtained in their dynamical evolution during the event on the basis of an inverse-problem solution. the derived angular distribution and spectra are discussed briefly. | first analysis of ground-level enhancement (gle) 72 on 10 september 2017: spectral and anisotropy characteristics |
gravitational waves (gws) from merging black holes and neutron stars directly measure the luminosity distance to the merger, which, when combined with an independent measurement of the source's redshift, provides a novel probe of cosmology. the proposed next generation of ground-based gw detectors, einstein telescope and cosmic explorer, will detect tens of thousands of binary neutron stars (bnss) out to cosmological distances (z >2 ), beyond the peak of the star formation rate (sfr), or "cosmic noon." at these distances, it will be challenging to measure the sources' redshifts by observing electromagnetic (em) counterparts or statistically marginalizing over a galaxy catalog. in the absence of an em counterpart or galaxy catalog, ding et al. [j. cosmol. astropart. phys. 04 (2019) 033], 10.1088/1475-7516/2019/04/033 showed that theoretical priors on the merger redshift distribution can be used to infer parameters in a w cdm (cold dark matter) cosmology. we argue that in the bns case, the redshift distribution will be measured by independent observations of short gamma ray bursts (grbs), kilonovae, and known bns host galaxies. in particular, the peak redshift will provide a clear feature to compare against the peak distance of the gw source distribution and reveal the underlying redshift-distance relation. we show that, in addition to measuring the background cosmology, this method can constrain the effects of dark energy on modified gw propagation. as a simple example, we consider the case in which the bns rate is a priori known to follow the sfr. if the sfr is perfectly known, o (10 ,000 ) events (to be expected within a year of observation with cosmic explorer) would yield a subtenth percent measurement of the combination h02.8ωm in a flat λ cdm model. meanwhile, fixing h0 and ωm to independently inferred values, this method may enable a 5% measurement of the dark energy equation of state parameter w in a w cdm model. fixing the background cosmology and instead probing modified gw propagation, the running of the planck mass parameter cm may be measured to ±0.02 . although realistically, the redshift evolution of the merger rate will be uncertain, prior knowledge of the peak redshift will provide valuable information for standard siren analyses. | cosmology with standard sirens at cosmic noon |
the nonresonant streaming instability (bell instability) plays a pivotal role in the acceleration and confinement of cosmic rays (crs); yet, the exact mechanism responsible for its saturation and the magnitude of the final amplified magnetic field have not been assessed from first-principles. using a survey of hybrid simulations (with kinetic ions and fluid electrons), we study the evolution of the bell instability as a function of the parameters of the cr population. we find that, at saturation, the magnetic pressure in the amplified field is comparable with the initial cr anisotropic pressure, rather than with the cr energy flux as previously argued. these results provide a predictive prescription for the total magnetic field amplification expected in the many astrophysical environments where the bell instability is important. | modeling the saturation of the bell instability using hybrid simulations |
we simulate the evolution of relativistic eletrons injected into the medium of a small galaxy cluster by a central radio galaxy, studying how the initial jet power affects the dispersal and the emission properties of radio plasma. by coupling passive tracer particles to adaptive-mesh cosmological magnetohydrodynamic (mhd) simulations, we study how cosmic-ray electrons are dispersed as a function of the input jet power. we also investigate how the latter affects the thermal and non-thermal properties of the intracluster medium, with differences discernible up to about one gyr after the start of the jet. we evolved the energy spectra of cosmic-ray electrons, subject to energy losses that are dominated by synchrotron and inverse compton emission as well as energy gains via re-acceleration by shock waves and turbulence. we find that in the absence of major mergers, the amount of re-acceleration experienced by cosmic-ray electrons is not enough to produce long-lived detectable radio emissions. however, for all simulations, the role of re-acceleration processes is crucial to maintaining a significant and volume-filling reservoir of fossil electrons (γ ∼ 103) for at least one gyr after the first injection by jets. this is important in attempting to establish plausible explanations of recent discoveries of cluster-wide emission and other radio phenomena in galaxy clusters. | life cycle of cosmic-ray electrons in the intracluster medium |
the origin of ultra-high-energy cosmic rays (uhecrs) remains elusive. gamma-ray bursts (grbs) are among the best candidates able to meet the stringent energy requirements needed for particle acceleration to such high energies. if uhecrs were accelerated by the central engine of grb 221009a, it might be possible to detect secondary photons and neutrinos as the uhecrs travel from the source to the earth. here, we attempt to interpret some of the early publicly available data connected to this burst. if the reported early gev-tev detection was produced by secondary emission from uhecrs, it probably indicates that uhecrs reached energies >1021 ev and that grb 221009a exploded inside a magnetic void with intergalactic magnetic field (igmf) strength b ≤ 3 × 10-16 g. in order to understand the entire energy deposition mechanism, we propose to search existing and future fermi-lat data for secondary emission arriving over larger spatial scales and longer time-scales. this strategy might help clarify the origin of uhecrs, constrain the igmf strength along this line of sight, and start to quantify the fraction of magnetic voids around grbs. | secondary gev-tev emission from ultra-high-energy cosmic rays accelerated by grb 221009a |
energetic non-thermal particles, or cosmic rays, are a major component of astrophysical plasmas next to magnetic fields, radiation, and thermal gas. cosmic rays are usually sub-dominant in density but carry as much pressure as the thermal plasma background. in some cases, cosmic rays drift at faster speeds with respect to the normal modes' phase speeds of the background plasma. because of this, cosmic rays are a strong source of free energy that causes new classes of kinetic or convective instabilities. recent years have seen the development of intense analytical and numerical efforts to analyze the onset of an instability produced by the motion of these particles at fast bulk speeds: this is the streaming instability. the streaming instability has been applied to different space plasmas and astrophysical contexts like strong shocks, jets, or in interstellar and intergalactic medium studies. streaming instabilities participate in the production of magnetic turbulence at scales corresponding to the gyroradius of the particles. by scattering off their self-generated waves, cosmic rays are coupled to the background thermal plasma. this mechanism is able to self-confine cosmic rays around sources and launch winds out of the disk of the galaxy, hence impacting galactic matter dynamics and ultimately the galactic star formation rate. we discuss a few science cases, which should be accessible in the near future for analytical calculations and numerical simulations. | the cosmic ray-driven streaming instability in astrophysical and space plasmas |
the alpha magnetic spectrometer (ams-02) experiment has ushered cosmic-ray physics into precision era. in an earlier paper [génolini et al., phys. rev. d 99, 123028 (2019), 10.1103/physrevd.99.123028], we designed an improved method to calibrate propagation models on the boron-to-carbon ratio data. here we provide a robust prediction of the p ¯ flux, accounting for several sources of uncertainties and their correlations. combined with a correlation matrix for the p ¯ data, we show that the latter are consistent with a secondary origin. this paper presents key elements relevant to the dark matter search in this channel, notably by pointing out the inherent difficulties in achieving predictions at the percent-level precision. | ams-02 antiprotons' consistency with a secondary astrophysical origin |
the hypothesis that high-energy cosmic neutrinos are power law distributed is critically analyzed. we propose a model with two components that better explains the observations. the extragalactic component of the high-energy neutrino flux has a canonical {e}ν -2 spectrum while the galactic component has a {e}ν -2.7 spectrum; both of them are significant. this model has several implications, which can be tested by icecube and antares over the next several years. moreover, the existence of a diffuse component, close to the galactic plane and that yields (20-30)% of icecube’s events, is interesting for the future km3 neutrino telescopes located in the northern hemisphere and for gamma-ray telescopes aiming to measure events up to a few 100 tev from the southern sky. | extragalactic plus galactic model for icecube neutrino events |
the `kascade cosmic ray data centre' is a web portal (https://kcdc.ikp.kit.eduhere the data of the astroparticle physics experiment kascade-grande are made available for the interested public. the kascade experiment was a large-area detector for the measurement of high-energy cosmic rays via the detection of extensive air showers. the multi-detector installations kascade and its extension kascade-grande stopped the active data acquisition in 2013 after more than 20 years of data taking. in several updates since our first release in 2013 with kcdc we provide the public measured and reconstructed parameters of more than 433 million air showers. in addition, kcdc provides meta data information and documentation to enable a user outside the community of experts to perform their own data analysis. simulation data from three different high energy interaction models have been made available as well as a compilation of measured and published spectra from various experiments. in addition, detailed educational examples shall encourage high-school students and early stage researchers to learn about astroparticle physics, cosmic radiation as well as the handling of big data and about the sustainable and public provision of scientific data. | the kascade cosmic-ray data centre kcdc: granting open access to astroparticle physics research data |
context. ngc 253 is one of only two starburst galaxies found to emit γ-rays from hundreds of mev to multi-tev energies. accurate measurements of the very-high-energy (vhe; e > 100 gev) and high-energy (he; e > 60 mev) spectra are crucial to study the underlying particle accelerators, probe the dominant emission mechanism(s) and to study cosmic-ray interaction and transport.aims: the measurement of the vhe γ-ray emission of ngc 253 published in 2012 by h.e.s.s. was limited by large systematic uncertainties. here, the most up to date measurement of the γ-ray spectrum of ngc 253 is investigated in both he and vhe γ-rays. assuming a hadronic origin of the γ-ray emission, the measurement uncertainties are propagated into the interpretation of the accelerated particle population.methods: the data of h.e.s.s. observations are reanalysed using an updated calibration and analysis chain. the improved fermi-lat analysis employs more than 8 yr of data processed using pass 8. the cosmic-ray particle population is evaluated from the combined he-vhe γ-ray spectrum using naima in the optically thin case.results: the vhe γ-ray energy spectrum is best fit by a power-law distribution with a flux normalisation of (1.34 ± 0.14stat ± 0.27sys) × 10-13 cm-2 s-1 tev1 at 1 tev - about 40% above, but compatible with the value obtained in abramowski et al. (2012). the spectral index γ = 2.39 ± 0.14stat ± 0.25sys is slightly softer than but consistent with the previous measurement within systematic errors. in the fermi energy range an integral flux of f(e > 60 mev) = (1.56 ± 0.28stat ± 0.15sys) × 10-8 cm-2 s-1 is obtained. at energies above ∼3 gev the he spectrum is consistent with a power-law ranging into the vhe part of the spectrum measured by h.e.s.s. with an overall spectral index γ = 2.22 ± 0.06stat.conclusions: two scenarios for the starburst nucleus are tested, in which the gas in the starburst nucleus acts as either a thin or a thick target for hadronic cosmic rays accelerated by the individual sources in the nucleus. in these two models, the level to which ngc 253 acts as a calorimeter is estimated to a range of fcal = 0.1 to 1 while accounting for the measurement uncertainties. the presented spectrum is likely to remain the most accurate measurements until the cherenkov telescope array (cta) has collected a substantial set of data towards ngc 253. | the starburst galaxy ngc 253 revisited by h.e.s.s. and fermi-lat |
context. a large fraction of cool-core clusters are known to host diffuse, steep-spectrum radio sources, called radio mini-halos, in their cores. mini-halos reveal the presence of relativistic particles on scales of hundreds of kiloparsecs, beyond the scales directly influenced by the central active galactic nucleus (agn), but the nature of the mechanism that produces such a population of radio-emitting, relativistic electrons is still debated. it is also unclear to what extent the agn plays a role in the formation of mini-halos by providing the seeds of the relativistic population.aims: in this work we explore the connection between thermal and non-thermal components of the intra-cluster medium in a sample of radio mini-halos and we study the implications within the framework of a hadronic model for the origin of the emitting electrons.methods: for the first time, we studied the thermal and non-thermal connection by carrying out a point-to-point comparison of the radio and the x-ray surface brightness in a sample of radio mini-halos. we extended the method generally applied to giant radio halos by considering the effects of a grid randomly generated through a monte carlo chain. then we used the radio and x-ray correlation to constrain the physical parameters of a hadronic model and we compared the model predictions with current observations.results: contrary to what is generally reported in the literature for giant radio halos, we find that the mini-halos in our sample have super-linear scaling between radio and x-rays, which suggests a peaked distribution of relativistic electrons and magnetic field. we explore the consequences of our findings on models of mini-halos. we use the four mini-halos in the sample that have a roundish brightness distribution to constrain model parameters in the case of a hadronic origin of the mini-halos. specifically, we focus on a model where cosmic rays are injected by the central agn and they generate secondaries in the intra-cluster medium, and we assume that the role of turbulent re-acceleration is negligible. this simple model allows us to constrain the agn cosmic ray luminosity in the range ∼1044-46 erg s-1 and the central magnetic field in the range 10-40 μg. the resulting γ-ray fluxes calculated assuming these model parameters do not violate the upper limits on γ-ray diffuse emission set by the fermi-lat telescope. further studies are now required to explore the consistency of these large magnetic fields with faraday rotation studies and to study the interplay between the secondary electrons and the intra-cluster medium turbulence. | radio and x-ray connection in radio mini-halos: implications for hadronic models |
3hsp j095507.9+355101 is an extreme blazar that has been possibly associated with a high-energy neutrino (icecube-200107a) detected 1 day before the blazar was found to undergo a hard x-ray flare. we perform a comprehensive study of the predicted multimessenger emission from 3hsp j095507.9+355101 during its recent x-ray flare, but also in the long term. we focus on one-zone leptohadronic models, but we also explore alternative scenarios: (i) a blazar-core model, which considers neutrino production in the inner jet, close to the supermassive black hole; (ii) a hidden external-photon model, which considers neutrino production in the jet through interactions with photons from a weak broad line region; (iii) a proton-synchrotron model, where high-energy protons in the jet produce γ-rays via synchrotron; and (iv) an intergalactic cascade scenario, where neutrinos are produced in the intergalactic medium by interactions of a high-energy cosmic-ray beam escaping the jet. the poisson probability to detect a single muon neutrino in 10 years from 3hsp j095507.9+355101 with the real-time icecube alert analysis is ∼1% (3%) for the most optimistic one-zone leptohadronic model (the multi-zone blazar-core model). meanwhile, detection of a single neutrino during the 44-day-long high x-ray flux-state period following the neutrino detection is 0.06%, according to our most optimistic leptohadronic model. the most promising scenarios for neutrino production also predict strong intrasource γ-ray attenuation above ∼100 gev. if the association is real, then icecube-gen2 and other future detectors should be able to provide additional evidence for neutrino production in 3hsp j095507.9+355101 and other extreme blazars. | comprehensive multimessenger modeling of the extreme blazar 3hsp j095507.9+355101 and predictions for icecube |
recent studies show that a universal relation between black hole (bh) growth and stellar mass (m⋆) or star formation rate (sfr) is an oversimplification of bh-galaxy coevolution, and that morphological and structural properties of host galaxies must also be considered. particularly, a possible connection between bh growth and host-galaxy compactness was identified among star-forming (sf) galaxies. utilizing ≈6300 massive galaxies with i814w < 24 at z < 1.2 in the cosmic evolution survey (cosmos) field, we perform systematic partial correlation analyses to investigate how sample-averaged bh accretion rate ($\rm \overline{bhar}$) depends on host-galaxy compactness among sf galaxies, when controlling for morphology and m⋆ (or sfr). the projected central surface mass density within 1 kpc, σ1, is utilized to represent host-galaxy compactness in our study. we find that the $\rm \overline{bhar}$-σ1 relation is stronger than either the $\rm \overline{bhar}$-m⋆ or $\rm \overline{bhar}$-sfr relation among sf galaxies, and this $\rm \overline{bhar}$-σ1 relation applies to both bulge-dominated galaxies and galaxies that are not dominated by bulges. this $\rm \overline{bhar}$-σ1 relation among sf galaxies suggests a link between bh growth and the central gas density of host galaxies on the kpc scale, which may further imply a common origin of the gas in the vicinity of the bh and in the central ~kpc of the galaxy. this $\rm \overline{bhar}$-σ1 relation can also be interpreted as the relation between bh growth and the central velocity dispersion of host galaxies at a given gas content (i.e. gas mass fraction), indicating the role of the host-galaxy potential well in regulating accretion on to the bh. | revealing the relation between black hole growth and host-galaxy compactness among star-forming galaxies |
nonthermal desorption of ices on interstellar grains is required to explain observations of molecules that are not synthesized efficiently in the gas phase in cold dense clouds. perhaps the most important nonthermal desorption mechanism is one induced by cosmic rays (crs), which, when passing through a grain, heat it transiently to a high temperature-the grain cools back to its original equilibrium temperature via the (partial) sublimation of the ice. current cosmic ray induced desorption (crd) models assume a fixed grain cooling time. in this work, we present a revised description of crd in which the desorption efficiency depends dynamically on the ice content. we apply the revised desorption scheme to two-phase and three-phase chemical models in physical conditions corresponding to starless and prestellar cores, and to molecular cloud envelopes. we find that, inside starless and prestellar cores, introducing dynamic crd can decrease gas-phase abundances by up to an order of magnitude in two-phase chemical models. in three-phase chemical models, our model produces results very similar to those of the static cooling scheme-when only one monolayer of ice is considered active. ice abundances are generally insensitive to variations in the grain cooling time. further improved crd models need to take into account additional effects in the transient heating of the grains-introduced, for example, by the adoption of a spectrum of cr energies. | a revised description of the cosmic ray induced desorption of interstellar ices |
radio relics in galaxy clusters are extended synchrotron sources produced by cosmic-ray electrons in the microgauss magnetic field. many relics are found in the cluster periphery and have a cluster-centric, narrow arc-like shape, which suggests that the electrons are accelerated or reaccelerated by merger shock fronts propagating outward in the intracluster plasma. in the x-ray, some relics do exhibit such shocks at the location of the relic, but many do not. we explore the possibility that radio relics trace not the shock fronts but the shape of the underlying distribution of seed relativistic electrons, lit up by a recent shock passage. we use magnetohydrodynamic simulations of cluster mergers and include bubbles of relativistic electrons injected by jets from the central active galactic nucleus or from an off-center radio galaxy. we show that the merger-driven gas motions (a) can advect the bubble cosmic rays to very large radii and (b) spread the relativistic seed electrons preferentially in the tangential direction-along the gravitational equipotential surfaces-producing extended, filamentary, or sheet-like regions of intracluster plasma enriched with aged cosmic rays, which resemble radio relics. once a shock front passes across such a region, the sharp radio emission edges would trace the sharp boundaries of these enriched regions rather than the front. we also show that these elongated cosmic-ray features are naturally associated with magnetic fields stretched tangentially along their long axis, which could help explain the high polarization of relics. | how merger-driven gas motions in galaxy clusters can turn agn bubbles into radio relics |
the evolution of cosmic structures, the formation and growth of the first black holes and the connection to their baryonic environment are key unsolved problems in astrophysics. the x-ray athena mission and the gravitational-wave laser interferometer space antenna (lisa) offer independent and complementary angles on these problems. we show that up to about 10 black hole binaries in the mass range of approximately 105 to 108 solar masses discovered by lisa at redshift below about 3.5 could be detected by athena in an exposure time up to 100 ks, if prompt x-ray emission of 1-10% of the eddington luminosity is present. likewise, if any lisa-detected extreme-mass-ratio inspirals occur in accretion disks, athena can detect associated electromagnetic emission out to a redshift of about 1. finally, warned by lisa, athena can point in advance and stare at stellar-mass binary black hole mergers at redshift less than about 0.1. these science opportunities emphasize the vast discovery space of simultaneous observations from the two observatories, which would be missed if they were operated in different epochs. | linking gravitational waves and x-ray phenomena with joint lisa and athena observations |
recent advances in the detection of cosmic-ray (cr) antiproton intensities at earth have the potential to provide valuable new insights in the search for dark matter. as such, a fuller understanding of the modulation of these particles due to the influence of the sun is of vital importance. valuable insights can be gained through the study of galactic cr protons, as the transport parameters for these particles are theoretically expected to be the same as those for antiprotons, barring drift effects. as such, the present study develops a data-driven, 3d time-dependent ab initio model for the modulation of galactic cr protons in the region of the heliosphere dominated by the supersonic solar wind, which yields results in good agreement with spacecraft observations over several solar cycles when an observationally motivated expression for the differential intensity spectrum of these particles at the heliospheric termination shock is employed. this model is then applied to the study of solar-cycle-dependent antiproton modulation using two current estimates for the local interstellar differential intensities of these particles. this approach yields estimates of antiproton intensities at the heliospheric termination shock that are considerably lower than the proposed interstellar spectra, with the implication that a significant amount of antiproton modulation is expected to occur in the heliosheath. | an ab initio approach to antiproton modulation in the inner heliosphere |
the galactic center (gc) region hosts a variety of powerful astronomical sources and rare astrophysical processes that emit a large flux of nonthermal radiation. the inner 375 pc × 600 pc region, called the central molecular zone, is home to the supermassive black hole sagittarius a*, massive cloud complexes, and particle accelerators such as supernova remnants (snrs). we present the results of our improved analysis of the very-high-energy gamma-ray emission above 2 tev from the gc using 125 hr of data taken with the very energetic radiation imaging telescope array system imaging-atmospheric cerenkov telescope between 2010 and 2018. the central source ver j1745-290, consistent with the position of sagittarius a*, is detected at a significance of 38 standard deviations above the background level (38σ), and we report its spectrum and light curve. its differential spectrum is consistent with a power law with exponential cutoff, with a spectral index of ${2.12}_{-0.17}^{+0.22}$ , a flux normalization at 5.3 tev of ${1.27}_{-0.23}^{+0.22}\times {10}^{-13}$ tev-1 cm-2 s-1, and cutoff energy of ${10.0}_{-2.0}^{+4.0}$ tev. we also present results on the diffuse emission near the gc, obtained by combining data from multiple regions along the gc ridge, which yield a cumulative significance of 9.5σ. the diffuse gc ridge spectrum is best fit by a power law with a hard index of 2.19 ± 0.20, showing no evidence of a cutoff up to 40 tev. this strengthens the evidence for a potential accelerator of pev cosmic rays being present in the gc. we also provide spectra of the other sources in our field of view with significant detections, composite snr g0.9+0.1, and hess j1746-285. | veritas observations of the galactic center region at multi-tev gamma-ray energies |
we determine the time-evolution of the dust particle size distribution during the collapse of a cloud core, accounting for both dust coagulation and dust fragmentation, to investigate the influence of dust growth on non-ideal magnetohydrodynamic (mhd) effects. the density evolution of the collapsing core is given by a one-zone model. we assume two types of dust model: dust composed only of silicate (silicate dust) and dust with a surface covered by h2o ice (h2o ice dust). when only considering collisional coagulation, the non-ideal mhd effects are not effective in the high-density region for both the silicate and h2o ice dust cases. this is because dust coagulation reduces the abundance of small dust particles, resulting in less efficient adsorption of charged particles on the dust surface. for the silicate dust case, when collisional fragmentation is included, the non-ideal mhd effects do apply at a high density of nh > 1012 cm-3 because of the abundant production of small dust particles. on the other hand, for the h2o ice dust case, the production of small dust particles due to fragmentation is not efficient. therefore, for the h2o ice dust case, non-ideal magnetohydrodynamic effects apply only in the range nh ≳ 1014 cm-3, even when collisional fragmentation is considered. our results suggest that it is necessary to consider both dust collisional coagulation and fragmentation to activate non-ideal magnetohydrodynamic effects, which should play a significant role in the star and disc formation processes. | dust coagulation and fragmentation in a collapsing cloud core and their influence on non-ideal magnetohydrodynamic effects |
observations of the cosmic 21-cm power spectrum (ps) are starting to enable precision bayesian inference of galaxy properties and physical cosmology, during the first billion years of our universe. here we investigate the impact of common approximations about the likelihood used in such inferences, including: (i) assuming a gaussian functional form; (ii) estimating the mean from a single realization; and (iii) estimating the (co)variance at a single point in parameter space. we compare 'classical' inference that uses an explicit likelihood with simulation-based inference (sbi) that estimates the likelihood from a training set. our forward models include: (i) realizations of the cosmic 21-cm signal computed with 21cmfast by varying ultraviolet (uv) and x-ray galaxy parameters together with the initial conditions; (ii) realizations of the telescope noise corresponding to a $1000 \, \mathrm{h}$ integration with the low-frequency component of the square kilometre array (ska1-low); and (iii) the excision of fourier modes corresponding to a foreground-dominated horizon 'wedge'. we find that the 1d ps likelihood is well described by a gaussian accounting for covariances between wave modes and redshift bins (higher order correlations are small). however, common approaches of estimating the forward-modelled mean and (co)variance from a random realization or at a single point in parameter space result in biased and overconstrained posteriors. our best results come from using sbi to fit a non-gaussian likelihood with a gaussian mixture neural density estimator. such sbi can be performed with up to an order of magnitude fewer simulations than classical, explicit likelihood inference. thus sbi provides accurate posteriors at a comparably low computational cost. | exploring the likelihood of the 21-cm power spectrum with simulation-based inference |
radio galaxies are intensively discussed as the sources of cosmic rays observed above about 3 × 1018 ev, called ultra-high energy cosmic rays (uhecrs). we present a first, systematic approach that takes the individual characteristics of these sources into account, as well as the impact of the extragalactic magnetic-field structures up to a distance of 120 mpc. we use a mixed simulation setup, based on 3d simulations of uhecrs ejected by observed, individual radio galaxies taken out to a distance of 120 mpc, and on 1d simulations over a continuous source distribution contributing from beyond 120 mpc. additionally, we include the ultra-luminous radio galaxy cygnus a at a distance of about 250 mpc, as its contribution is so strong that it must be considered as an individual point source. the implementation of the uhecr ejection in our simulation setup, both that of individual radio galaxies and the continuous source function, is based on a detailed consideration of the physics of radio jets and standard first-order fermi acceleration. this allows to derive the spectrum of ejected uhecr as a function of radio luminosity, and at the same time provides an absolute normalization of the problem involving only a small set of parameters adjustable within narrow constraints. we show that the average contribution of radio galaxies taken over a very large volume cannot explain the observed features of uhecrs measured at earth. however, we obtain excellent agreement with the spectrum, composition, and arrival-direction distribution of uhecrs measured by the pierre auger observatory, if we assume that most uhecrs observed arise from only two sources: the ultra-luminous radio galaxy cygnus a, providing a mostly light composition of nuclear species dominating up to about 6 × 1019 ev, and the nearest radio galaxy centaurus a, providing a heavy composition dominating above 6 × 1019 ev . here we have to assume that extragalactic magnetic fields out to 250 mpc, which we did not include in the simulation, are able to isotropize the uhecr events {at about 8 eev} arriving from cygnus a. even in this case, significant anisotropy correlated with cygnus a and centaurus a could be present at higher energies, and thus allow for differences in uhecr spectrum and composition between the northern and southern hemispheres. if this scenario can be confirmed, it would also imply that the uhecr flux in our local cosmic environment is significantly above the average throughout the universe. | ultra-high-energy cosmic rays from radio galaxies |
irrigation increases soil moisture, which in turn controls water and energy fluxes from the land surface to the planetary boundary layer and determines plant stress and productivity. therefore, developing a realistic representation of irrigation is critical to understanding land-atmosphere interactions in agricultural areas. irrigation parameterizations are becoming more common in land surface models and are growing in sophistication, but there is difficulty in assessing the realism of these schemes, due to limited observations (e.g., soil moisture, evapotranspiration) and scant reporting of irrigation timing and quantity. this study uses the noah land surface model run at high resolution within nasa's land information system to assess the physics of a sprinkler irrigation simulation scheme and model sensitivity to choice of irrigation intensity and greenness fraction datasets over a small, high-resolution domain in nebraska. differences between experiments are small at the interannual scale but become more apparent at seasonal and daily timescales. in addition, this study uses point and gridded soil moisture observations from fixed and roving cosmic-ray neutron probes and co-located human-practice data to evaluate the realism of irrigation amounts and soil moisture impacts simulated by the model. results show that field-scale heterogeneity resulting from the individual actions of farmers is not captured by the model and the amount of irrigation applied by the model exceeds that applied at the two irrigated fields. however, the seasonal timing of irrigation and soil moisture contrasts between irrigated and non-irrigated areas are simulated well by the model. overall, the results underscore the necessity of both high-quality meteorological forcing data and proper representation of irrigation for accurate simulation of water and energy states and fluxes over cropland. | assessment of irrigation physics in a land surface modeling framework using non-traditional and human-practice datasets |
the last glacial termination led to major changes in ice sheet coverage that disrupted global patterns of atmosphere and ocean circulation. paleoclimate records from iberia suggest that westerly episodes played a key role in driving heterogeneous climate in the north atlantic region. we used 10be cosmic ray exposure (cre) dating to explore the glacier response of small mountain glaciers (ca. 5 km2) that developed on the northern slope of the cantabrian mountains (iberian peninsula), an area directly under the influence of the atlantic westerly winds. we analyzed twenty boulders from three moraines and one rock glacier arranged as a recessional sequence preserved between 1150 and 1540 m above sea level (a.s.l.) in the monasterio valley (redes natural park). results complement previous chronologic data based on radiocarbon and optically stimulated luminescence from the monasterio valley, which suggest a local glacial maximum (local gm) prior to 33 ka bp and a long-standing glacier advance at 24 ka coeval to the global last glacial maximum (lgm). resultant 10be cre ages suggest a progressive retreat and thinning of the monasterio glacier over the time interval 18.1-16.7 ka. this response is coeval with the heinrich stadial 1, an extremely cold and dry climate episode initiated by a weakening of the atlantic meridional overturning circulation (amoc). glacier recession continued through the bølling/allerød period as indicate the minimum exposure ages obtained from a cirque moraine and a rock glacier nested within this moraine, which yielded ages of 14.0 and 13.0 ka, respectively. together, they suggest that the monasterio glacier experienced a gradual transition from glacier to rock glacier activity as the amoc started to strengthen again. glacial evidence ascribable to the younger dryas cooling was not dated in the monasterio valley, but might have occurred at higher elevations than evidence dated in this work. the evolution of former glaciers documented in the monasterio valley seems consistent with previous 10be chronologies reported in other mountain ranges of the iberian peninsula, which have been recalculated according to a common production rate and scaling scheme. however, the re-evaluation of published 10be chronologies has highlighted the fact that glacial evidence previously ascribed to the younger dryas might be more limited than previously thought and the need for additional studies to characterized the extent of glaciers during the younger dryas cooling. | timing of last deglaciation in the cantabrian mountains (iberian peninsula; north atlantic region) based on in situ-produced 10be exposure dating |
the sample of neutron stars with a measured mass is growing quickly. with the latest sample, we adopt both a flexible gaussian mixture model and a gaussian plus cauchy-lorentz component model to infer the mass distribution of neutron stars and use the bayesian model selection to explore evidence for multimodality and a sharp cutoff in the mass distribution. the two models yield rather similar results. consistent with previous studies, we find evidence for a bimodal distribution together with a cutoff at a mass of mmax=2.2 6-0.05+0.12 m⊙ (68% credible interval, for the gaussian mixture model). if such a cutoff is interpreted as the maximum gravitational mass of nonrotating cold neutron stars, the prospect of forming supramassive remnants is found to be quite promising for the double neutron star mergers with a total gravitational mass less than or equal to 2.7 m⊙ unless the thermal pions could substantially soften the equation of state for the very hot neutron star matter. these supramassive remnants have a typical kinetic rotational energy of approximately 1 -2 ×1053 ergs . together with a high neutron star merger rate approximately 103 gpc-3 yr-3 , the neutron star mergers are expected to be significant sources of eev (1 018 ev) cosmic-ray protons. | maximum mass cutoff in the neutron star mass distribution and the prospect of forming supramassive objects in the double neutron star mergers |
here we report the relative degrees of thermal metamorphism for five antarctic ornans-like carbonaceous (co) chondrites, including dominion range (dom) 08006, as determined from the cr-content of their feo-rich (ferroan) olivine. these five co3 chondrites complete the previously poorly-defined co3.00 to 3.2 chondrite metamorphic trend. dom 08006 appears to be a highly primitive co chondrite of petrologic type 3.00. we report the detailed mineralogy and petrography of dom 08006 using a coordinated, multi-technique approach. the interchondrule matrix in dom 08006 consists of unequilibrated mixtures of silicate, metal, and sulfide minerals and lacks fe-rich rims on silicates indicating that dom 08006 has only experienced minimal, if any, thermal metamorphism. this is also reflected by the co/ni ratios of ni-rich and ni-poor metal, a sensitive indicator of thermal metamorphism, and the presence of euhedral chrome-spinel grains, which typically become subhedral to anhedral during progressive metamorphism. dom 08006 matrix shows minor evidence for aqueous alteration and while the presence of magnetite surrounding metal in chondrules indicates that there has been some interaction with fluid, much metal remains and none of the sulfides analyzed show evidence of being formed by aqueous alteration. furthermore, the plagioclase of ∼50% of chondrules analyzed show resolvable excess silica indicating that these chondrules have experienced minimal, if any, reprocessing in the co parent body. noble gas data for dom 08006 show that it contains the highest concentrations of trapped 36ar and 132xe of all co chondrites analyzed to date, further indicating that dom 08006 is the most primitive co chondrite known. the cosmic ray exposure age of dom 08006 is estimated to be ∼19 ma. the minimally altered nature of dom 08006 demonstrates that it is an extremely important sample for providing valuable insight into early solar system conditions. at a total weight of 667 g, a significant amount of material is available for a wide array of future studies. | mineralogy and petrology of dominion range 08006: a very primitive co3 carbonaceous chondrite |
we present the results of laboratory measurements of the ion-ion recombination coefficient at different temperatures, relative humidities and concentrations of ozone and sulfur dioxide. the experiments were carried out using the cosmics leaving outdoor droplets (cloud) chamber at cern, the walls of which are made of conductive material, making it possible to measure small ions. we produced ions in the chamber using a 3.5 gev c-1 beam of positively charged pions (π+) generated by the cern proton synchrotron (ps). when the ps was switched off, galactic cosmic rays were the only ionization source in the chamber. the range of the ion production rate varied from 2 to 100 cm-3 s-1, covering the typical range of ionization throughout the troposphere. the temperature ranged from -55 to 20 °c, the relative humidity (rh) from 0 to 70 %, the so2 concentration from 0 to 40 ppb, and the ozone concentration from 200 to 700 ppb. the best agreement of the retrieved ion-ion recombination coefficient with the commonly used literature value of 1.6 × 10-6 cm3 s-1 was found at a temperature of 5 °c and a rh of 40 % (1.5 ± 0.6) × 10-6 cm3 s-1. at 20 °c and 40 % rh, the retrieved ion-ion recombination coefficient was instead (2.3 ± 0.7) × 10-6 cm3 s-1. we observed no dependency of the ion-ion recombination coefficient on ozone concentration and a weak variation with sulfur dioxide concentration. however, we observed a more than fourfold increase in the ion-ion recombination coefficient with decreasing temperature. we compared our results with three different models and found an overall agreement for temperatures above 0 °c, but a disagreement at lower temperatures. we observed a strong increase in the recombination coefficient for decreasing relative humidities, which has not been reported previously. | experimental investigation of ion-ion recombination under atmospheric conditions |
our heliosphere—the bubble in the local interstellar medium produced by the sun’s outflowing solar wind—has finally responded to a large increase in solar wind output and pressure in the second half of 2014. nasa’s interstellar boundary explorer (ibex) mission remotely monitors the outer heliosphere by observing energetic neutral atoms (enas) returning from the heliosheath, the region between the termination shock and heliopause. ibex observed a significant enhancement in higher energy enas starting in late 2016. while ibex observations over the previous decade reflected a general reduction of ena intensities, indicative of a deflating heliosphere, new observations show that the large (∼50%), persistent increase in the solar wind dynamic pressure has modified the heliosheath, producing enhanced ena emissions. the combination of these new observations with simulation results indicate that this pressure is re-expanding our heliosphere, with the termination shock and heliopause already driven outward in the locations closest to the sun. the timing between the ibex observations, a large transient pressure enhancement seen by voyager 2, and the simulations indicates that the pressure increase propagated through the heliosheath, reflected off the heliopause, and the enhanced density of the solar wind filled the heliosheath behind it before generating significantly enhanced ena emissions. the coming years should see significant changes in anomalous cosmic rays, galactic cosmic radiation, and the filtration of interstellar neutral atoms into the inner heliosphere. | heliosphere responds to a large solar wind intensification: decisive observations from ibex |
we developed a chemical network for modelling the chemistry and non-ideal magnetohydrodynamic (mhd) effects from the collapsing dense molecular clouds to protostellar discs. first, we reformulated the cosmic-ray desorption rate by considering the variations of desorption rate over the grain size distribution. we find that the differential desorption of volatile species is amplified by the grains larger than 0.1 μm, because larger grains are heated to a lower temperature by cosmic-rays and hence more sensitive to the variations in binding energies. as a result, atomic nitrogen, n, is ∼ two orders of magnitude more abundant than co; n2h+ also becomes a few times more abundant than hco+ due to the increased gas-phase n2. however, the changes in ionization fraction due to freeze-out and desorption only have minor effects on the non-ideal mhd diffusivities. our chemical network confirms that the very small grains (below a few 100 å) weakens the efficiency of both ambipolar diffusion and hall effect. in collapsing dense cores, a maximum ambipolar diffusion is achieved when truncating the mathis-rumpl-nordsieck size distribution at 0.1 μm, and for a maximum hall effect, the truncation occurs at 0.04 μm. we conclude that the grain size distribution is crucial to the differential depletion between co- and n2- related molecules as well as to the non-ideal mhd diffusivities in dense cores. | effect of grain size on differential desorption of volatile species and on non-ideal mhd diffusivity |
shell-type supernova remnants (snrs) are considered prime candidates for the acceleration of galactic cosmic rays (crs) up to the knee of the cr spectrum at e ≈ 3 × 1015 ev. our milky way galaxy hosts more than 350 snrs discovered at radio wavelengths and at high energies, of which 220 fall into the h.e.s.s. galactic plane survey (hgps) region. of those, only 50 snrs are coincident with a h.e.s.s source and in 8 cases the very high-energy (vhe) emission is firmly identified as an snr. the h.e.s.s. gps provides us with a legacy for snr population study in vhe γ-rays and we use this rich data set to extract vhe flux upper limits from all undetected snrs. overall, the derived flux upper limits are not in contradiction with the canonical cr paradigm. assuming this paradigm holds true, we can constrain typical ambient density values around shell-type snrs to n ≤ 7 cm-3 and electron-to-proton energy fractions above 10 tev to ɛep ≤ 5 × 10-3. furthermore, comparisons of vhe with radio luminosities in non-interacting snrs reveal a behaviour that is in agreement with the theory of magnetic field amplification at shell-type snrs. | population study of galactic supernova remnants at very high γ-ray energies with h.e.s.s. |
the cosmic-ray neutron sensor (crns), which estimates field scale soil water content, bridges the gap between point measurement and remote sensing. the accuracy of crns measurements, however, is affected by additional hydrogen pools (e.g., vegetation, snow, and rainfall interception). the objectives of this study are to: (i) evaluate the accuracy of crns estimates in a farmland system using depth and horizontal weighted point measurements, (ii) introduce a novel method for estimating the amounts of hydrogen from biomass and snow cover in crns data, and (iii) propose a simple approach for correcting the influences of aboveground hydrogen pool (expressed as aboveground water equivalent, awe) on crns measurements. a field experiment was conducted in northeast china to compare soil water content results from crns to in-situ data with time domain reflectometry (tdr) and neutron probe (np) in the 0-40 cm soil layers. the biomass water equivalent (bwe) and snow water equivalent (swe) were observed to have separate linear relationships with the thermal/fast neutron ratio, and the dynamics of bwe and swe were estimated correctly in the crop seasons and snow-covered seasons, respectively. a simple approach, which considered the awe, awe at calibration, and the effective measurement depth of crns, was introduced to correct the errors caused by bwe and swe. after correction, the correlation coefficients between soil water contents determined by crns and tdr were 0.79 and 0.77 during the 2014 and 2015 crop seasons, respectively, and crns measurements had rmses of 0.028, 0.030, and 0.039 m3 m-3 in the 2014 and 2015 crop seasons and the snow-covered seasons, respectively. the experimental results also indicated that the accuracies of crns estimated bwe and swe were affected by the distributions of aboveground hydrogen pools, which were related to the height of the crns device above ground surface. | soil water content determination with cosmic-ray neutron sensor: correcting aboveground hydrogen effects with thermal/fast neutron ratio |
we searched for an optical counterpart to the first gravitational-wave source discovered by ligo (gw150914), using a combination of the pan-starrs1 wide-field telescope and the public eso spectroscopic survey of transient objects (pessto) spectroscopic follow-up programme. as the final ligo sky maps changed during analysis, the total probability of the source being spatially coincident with our fields was finally only 4.2 per cent. therefore, we discuss our results primarily as a demonstration of the survey capability of pan-starrs and spectroscopic capability of pessto. we mapped out 442 deg2 of the northern sky region of the initial map. we discovered 56 astrophysical transients over a period of 41 d from the discovery of the source. of these, 19 were spectroscopically classified and a further 13 have host galaxy redshifts. all transients appear to be fairly normal supernovae (sne) and agn variability and none is obviously linked with gw150914. we illustrate the sensitivity of our survey by defining parametrized light curves with time-scales of 4, 20 and 40 d and use the sensitivity of the pan-starrs1 images to set limits on the luminosities of possible sources. the pan-starrs1 images reach limiting magnitudes of ip1 = 19.2, 20.0 and 20.8, respectively, for the three time-scales. for long time-scale parametrized light curves (with full width half-maximum ≃40 d), we set upper limits of m_i ≤ -17.2^{-0.9}_{+1.4} if the distance to gw150914 is dl = 400 ± 200 mpc. the number of type ia sn we find in the survey is similar to that expected from the cosmic sn rate, indicating a reasonably complete efficiency in recovering sn like transients out to dl = 400 ± 200 mpc. | pan-starrs and pessto search for an optical counterpart to the ligo gravitational-wave source gw150914 |
cosmic ray interactions that produce high-energy neutrinos also inevitably generate high-energy gamma rays, which finally contribute to the diffuse high-energy gamma-ray background after they escape the sources. it was recently found that the high flux of neutrinos at ∼30 tev detected by icecube lead to a cumulative gamma-ray flux exceeding the fermi isotropic gamma-ray background at 10-100 gev, implying that the neutrinos are produced by hidden sources of cosmic rays, where gev-tev gamma rays are not transparent. here we suggest that relativistic jets in tidal disruption events (tdes) of supermassive black holes are such hidden sources. we consider the jet propagation in an extended, optically thick envelope around the black hole, which results from the ejected material during the disruption. while powerful jets can break free from the envelope, less powerful jets would be choked inside the envelope. the jets accelerate cosmic rays through internal shocks or reverse shocks and further produce neutrinos via interaction with the surrounding dense photons. all three tde jets discovered so far are not detected by fermi/lat, suggesting that gev-tev gamma rays are absorbed in these jets. the cumulative neutrino flux from tde jets can account for the neutrino flux observed by icecube at pev energies and may also account for the higher flux at ∼30 tev if less powerful, choked jets are present in the majority of tdes. | tidal disruption jets of supermassive black holes as hidden sources of cosmic rays: explaining the icecube tev-pev neutrinos |
we present radio continuum maps of 12 nearby (d ≤ 27 mpc), edge-on (i ≥ 76°), late-type spiral galaxies mostly at 1.4 and 5 ghz, observed with the australia telescope compact array, very large array, westerbork synthesis radio telescope, effelsberg 100-m, and parkes 64-m telescopes. all galaxies show clear evidence of radio haloes, including the first detection in the magellanic-type galaxy ngc 55. in 11 galaxies, we find a thin and a thick disc that can be better fitted by exponential rather than gaussian functions. we fit our spinnaker (spectral index numerical analysis of k(c)osmic-ray electron radio-emission) 1d cosmic ray transport models to the vertical model profiles of the non-thermal intensity and to the non-thermal radio spectral index in the halo. we simultaneously fit for the advection speed (or diffusion coefficient) and magnetic field scale height. in the thick disc, the magnetic field scale heights range from 2 to 8 kpc with an average across the sample of 3.0 ± 1.7 kpc; they show no correlation with either star formation rate (sfr), sfr surface density (σsfr), or rotation speed (vrot). the advection speeds range from 100 to 700 km s - 1 and display correlations of v∝sfr0.36 ± 0.06 and v∝ σ _sfr^{0.39± 0.09}; they agree remarkably well with the escape velocities (0.5 ≤ v/vesc ≤ 2), which can be explained by cosmic ray-driven winds. radio haloes show the presence of disc winds in galaxies with σsfr > 10 - 3 m⊙ yr - 1 kpc - 2 that extend over several kpc and are driven by processes related to the distributed star formation in the disc. | radio haloes in nearby galaxies modelled with 1d cosmic ray transport using spinnaker |
it has long been suspected that powerful radio sources may lower the efficiency with which stars form from the molecular gas in their host galaxy, however so far, alternative mechanisms, in particular related to the stellar mass distribution in the massive bulges of their host galaxies, have not been ruled out. we present new, arcsecond-resolution atacama large millimeter array (alma) co(1−0) interferometry, which probes the spatially resolved, cold molecular gas in the nearby (z = 0.08), massive (mstellar = 4 × 1011 m⊙), isolated, late-type spiral galaxy 2massx j23453269−044925, which is outstanding for having two pairs of powerful, giant radio jets, and a bright x-ray halo of hot circumgalactic gas. the molecular gas is in a massive (mgas = 2.0 × 1010 m⊙), 24 kpc wide, rapidly rotating ring, which is associated with the inner stellar disk. broad (fwhm = 70−180 km s−1) emission lines with complex profiles associated with the radio source are seen over large regions in the ring, indicating gas velocities that are high enough to keep the otherwise marginally toomre-stable gas from fragmenting into gravitationally bound, star-forming clouds. about 1−2% of the jet kinetic energy is required to power these motions. resolved star-formation rate surface densities derived from galaxy evolution explorer and wide-field infrared survey explorer fall by factors of 30−70 short of expectations from the standard kennicutt-schmidt law of star-forming galaxies, and near gas-rich early-type galaxies with signatures of star formation that are lowered by jet feedback. we argue that radio active galactic nucleus (agn) feedback is the only plausible mechanism to explain the low star-formation rates in this galaxy. previous authors have already noted that the x-ray halo of j2345−0449 implies a baryon fraction that is close to the cosmic average, which is very high for a galaxy. we contrast this finding with other, equally massive, and equally baryon-rich spiral galaxies without prominent radio sources. most of the baryons in these galaxies are in stars, not in the halos. we also discuss the implications of our results for our general understanding of agn feedback in massive galaxies. based on data obtained with alma through program 2019.1.01492.s and with iram through program 080-19. | jet-driven agn feedback on molecular gas and low star-formation efficiency in a massive local spiral galaxy with a bright x-ray halo |
for 50 years, cosmic-ray air showers have been detected by their radio emission. we present the first laboratory measurements that validate electrodynamics simulations used in air shower modeling. an experiment at slac provides a beam test of radio-frequency (rf) radiation from charged particle cascades in the presence of a magnetic field, a model system of a cosmic-ray air shower. this experiment provides a suite of controlled laboratory measurements to compare to particle-level simulations of rf emission, which are relied upon in ultrahigh-energy cosmic-ray air shower detection. we compare simulations to data for intensity, linearity with magnetic field, angular distribution, polarization, and spectral content. in particular, we confirm modern predictions that the magnetically induced emission in a dielectric forms a cone that peaks at the cherenkov angle and show that the simulations reproduce the data within systematic uncertainties. | accelerator measurements of magnetically induced radio emission from particle cascades with applications to cosmic-ray air showers |
recently the ams-02 experiment reported an excess of cosmic ray antiprotons over the expected astrophysical background. we interpret the excess as a signal from annihilating or decaying dark matter and find that the observed spectrum is well fitted by adding contributions from the annihilation or decay of dark matter with mass of o (tev) or larger. interestingly, wino dark matter with mass of around 3 tev, whose thermal relic abundance is consistent with present dark matter abundance, can explain the antiproton excess. we also discuss the implications for the decaying gravitino dark matter with r-parity violation. | ams-02 antiprotons from annihilating or decaying dark matter |
a dramatic increase in the accuracy and statistics of space-borne cosmic ray (cr) measurements has yielded several breakthroughs over the last several years. the most puzzling is the rise in the positron fraction above ∼10 gev over the predictions of the propagation models assuming pure secondary production. the accuracy of the antiproton production cross section is critical for astrophysical applications and searches for new physics since antiprotons in crs seem to hold the keys to many puzzles including the origin of those excess positrons. however, model calculations of antiproton production in cr interactions with interstellar gas are often employing parameterizations that are out of date or are using outdated physical concepts. this may lead to an incorrect interpretation of antiproton data which could have broad consequences for other areas of astrophysics. in this work, we calculate antiproton production in pp-, pa-, and aa-interactions using epos-lhc and qgsjet-ii-04, two of the most advanced monte carlo (mc) generators tuned to numerous accelerator data including those from the large hadron collider (lhc). we show that the antiproton yields obtained with these mc generators differ by up to an order of magnitude from yields of parameterizations commonly used in astrophysics. | new calculation of antiproton production by cosmic ray protons and nuclei |
the ams-02 collaboration has just released the cosmic antiproton to proton ratio $\bar{p}/p$ with a high precision up to $\sim 450$ gev. in this work, we calculate the secondary antiprotons generated by cosmic ray interactions with the interstellar medium taking into account the uncertainties from the cosmic ray propagation. the $\bar{p}/p$ ratio predicted by these processes shows some tension with the ams-02 data in some regions of propagation parameters, but the excess is not significant. we then try to derive upper bounds on the dark matter annihilation cross section from the $\bar{p}/p$ data or signal regions favored by the data. it is shown that the constraint derived by the ams-02 data is similar to that from fermi-lat observations of dwarf galaxies. the signal region for dark matter is usually required $m_\chi \sim o(10)$ tev and $\left<\sigma v\right>\sim\mathcal{o}(10^{-23})~\cm^3~\sec^{-1}$. | implications for dark matter annihilation from the ams-02 $\\bar{p}/p$ ratio |
context. high-mass x-ray binaries (hmxbs) might have contributed a non-negligible fraction of the energy feedback to the interstellar and intergalactic media at high redshift, becoming important sources for the heating and ionization history of the universe. however, the importance of this contribution depends on the hypothesized increase in the number of hmxbs formed in low-metallicity galaxies and in their luminosities.aims: in this work we test the aforementioned hypothesis, and quantify the metallicity dependence of hmxb population properties.methods: we compile from the literature a large set of data on the sizes and x-ray luminosities of hmxb populations in nearby galaxies with known metallicities and star formation rates. we use bayesian inference to fit simple monte carlo models that describe the metallicity dependence of the size and luminosity of the hmxb populations.results: we find that hmxbs are typically ten times more numerous per unit star formation rate in low-metallicity galaxies (12 + log (o / h) < 8, namely <20% solar) than in solar-metallicity galaxies. the metallicity dependence of the luminosity of hmxbs is small compared to that of the population size.conclusions: our results support the hypothesis that hmxbs are more numerous in low-metallicity galaxies, implying the need to investigate the feedback in the form of x-rays and energetic mass outflows of these high-energy sources during cosmic dawn. | metallicity dependence of high-mass x-ray binary populations |
in the standard picture of galactic cosmic rays, a diffuse flux of high-energy gamma rays and neutrinos is produced from inelastic collisions of cosmic-ray nuclei with the interstellar gas. the neutrino flux is a guaranteed signal for high-energy neutrino observatories such as icecube but has not been found yet. experimental searches for this flux constitute an important test of the standard picture of galactic cosmic rays. both observation and nonobservation would allow important implications for the physics of cosmic-ray acceleration and transport. we present cringe, a new model of galactic diffuse high-energy gamma rays and neutrinos, fitted to recent cosmic-ray data from ams-02, dampe, icetop, as well as kascade. we quantify the uncertainties for the predicted emission from the cosmic-ray model but also from the choice of source distribution, gas maps, and cross sections. we consider the possibility of a contribution from unresolved sources. our model predictions exhibit significant deviations from older models. our fiducial model is available at https://doi.org/10.5281/zenodo.7859442 . | diffuse emission of galactic high-energy neutrinos from a global fit of cosmic rays |
the processes controlling the complex clump structure, phase distribution, and magnetic field geometry that develop across a broad range of scales in the turbulent interstellar medium (ism) remain unclear. using unprecedentedly high-resolution 3d magnetohydrodynamic simulations of thermally unstable turbulent systems, we show that large current sheets unstable to plasmoid-mediated reconnection form regularly throughout the volume. the plasmoids form in three distinct environments: (i) within cold clumps, (ii) at the asymmetric interface of the cold and warm phases, and (iii) within the warm, volume-filling phase. we then show that the complex magnetothermal phase structure is characterized by a predominantly highly magnetized cold phase, but that regions of high magnetic curvature, which are the sites of reconnection, span a broad range in temperature. furthermore, we show that thermal instabilities change the scale-dependent anisotropy of the turbulent magnetic field, reducing the increase in eddy elongation at smaller scales. finally, we show that most of the mass is contained in one contiguous cold structure surrounded by smaller clumps that follow a scale-free mass distribution. these clumps tend to be highly elongated and exhibit a size versus internal velocity relation consistent with supersonic turbulence and a relative clump distance-velocity scaling consistent with subsonic motion. we discuss the striking similarity of cold plasmoids to observed tiny-scale atomic and ionized structures and h i fibers and consider how the presence of plasmoids will modify the motion of charged particles, thereby impacting cosmic-ray transport and thermal conduction in the ism and other similar systems. | plasmoid instability in the multiphase interstellar medium |
many practical hydrological, meteorological, and agricultural management problems require estimates of soil moisture with an areal footprint equivalent to field scale, integrated over the entire root zone. the cosmic-ray neutron probe is a promising instrument to provide field-scale areal coverage, but these observations are shallow and require depth-scaling in order to be considered representative of the entire root zone. a study to identify appropriate depth-scaling techniques was conducted at a grazing pasture site in central saskatchewan, canada over a 2-year period. area-averaged soil moisture was assessed using a cosmic-ray neutron probe. root zone soil moisture was measured at 21 locations within the 500 m × 500 m study area, using a down-hole neutron probe. the cosmic-ray neutron probe was found to provide accurate estimates of field-scale surface soil moisture, but measurements represented less than 40 % of the seasonal change in root zone storage due to its shallow measurement depth. the root zone estimation methods evaluated were: (a) the coupling of the cosmic-ray neutron probe with a time-stable neutron probe monitoring location, (b) coupling the cosmic-ray neutron probe with a representative landscape unit monitoring approach, and (c) convolution of the cosmic-ray neutron probe measurements with the exponential filter. the time stability method provided the best estimate of root zone soil moisture (rmse = 0.005 cm3 cm-3), followed by the exponential filter (rmse = 0.014 cm3 cm-3). the landscape unit approach, which required no calibration, had a negative bias but estimated the cumulative change in storage reasonably. the feasibility of applying these methods to field sites without existing instrumentation is discussed. based upon its observed performance and its minimal data requirements, it is concluded that the exponential filter method has the most potential for estimating root zone soil moisture from cosmic-ray neutron probe data. | estimating field-scale root zone soil moisture using the cosmic-ray neutron probe |
the search for weakly interacting massive particles (wimps) by direct detection faces an encroaching background due to coherent neutrino-nucleus scattering. for a given wimp mass the cross section at which neutrinos constitute a dominant background is dependent on the uncertainty on the flux of each neutrino source, principally from the sun, supernovae or atmospheric cosmic ray collisions. however there are also considerable uncertainties with regard to the astrophysical ingredients of the predicted wimp signal. uncertainties in the velocity of the sun with respect to the milky way dark matter halo, the local density of wimps, and the shape of the local wimp speed distribution all have an effect on the expected event rate in direct detection experiments and hence will change the region of the wimp parameter space for which neutrinos are a significant background. in this work we extend the neutrino floor calculation to account for the uncertainty in the astrophysics dependence of the wimp signal. we show the effect of uncertainties on projected discovery limits with an emphasis on low wimp masses (less than 10 gev) when solar neutrino backgrounds are most important. we find that accounting for astrophysical uncertainties changes the shape of the neutrino floor as a function of wimp mass but also causes it to appear at cross sections up to an order of magnitude larger, extremely close to existing experimental limits, indicating that neutrino backgrounds will become an issue sooner than previously thought. we also explore how neutrinos hinder the estimation of wimp parameters and how astrophysical uncertainties impact the discrimination of wimps and neutrinos with the use of their respective time dependencies. | dark matter astrophysical uncertainties and the neutrino floor |
the recent icecube publication claims the observation of cosmic neutrinos with energies down to ∼10 tev , reinforcing the growing evidence that the neutrino flux in the 10-100 tev range is unexpectedly large. any conceivable source of these neutrinos must also produce a γ -ray flux which degrades in energy en route to the earth and contributes to the extragalactic γ -ray background measured by the fermi satellite. in a quantitative multimessenger analysis, featuring minimalistic assumptions, we find a ≳3 σ tension in the data, reaching ∼5 σ for cosmic neutrinos extended down to ∼1 tev , interpreted as evidence for a population of hidden cosmic-ray accelerators. | new constraints on the origin of medium-energy neutrinos observed by icecube |
the cosmic web is a complex network of filaments, walls, and voids that represent the largest structures in the universe. in this network, which is the direct result of structure formation, galaxy clusters occupy central positions that form the nodes and these are connected by filaments. in this work, we investigate the position in the cosmic web of one of the most well-known and best-studied clusters of galaxies, the coma cluster. we make use of the sloan digital sky survey data release 7 main galaxy sample and of the discrete persistent structure extractor to detect large-scale filaments around the coma cluster and analyse the properties of the cosmic web. we study the network of filaments around coma in a region of 75 mpc in radius. we find that the coma cluster has a median connectivity of 2.5, in agreement with measurements from clusters of similar mass in the literature as well as with what is expected from numerical simulations. coma is indeed connected to three secure filaments which connect it to abell 1367 and to several other clusters in the field. the location of these filaments in the vicinity of coma is consistent with features detected in the x-ray, as well as the likely direction of infall of galaxies, such as for example ngc 4839. the overall picture that emerges of the coma cluster is that of a highly connected structure occupying a central position as a dense node of the cosmic web. we also find a tentative detection, at 2.1σ significance, of the filaments in the sz signal. | like a spider in its web: a study of the large-scale structure around the coma cluster |
we have simulated the evolution of non-thermal cosmic ray electrons (cres) in 3d relativistic magneto hydrodynamic (mhd) jets evolved up to a height of 9 kpc. the cres have been evolved in space and in energy concurrently with the relativistic jet fluid, duly accounting for radiative losses and acceleration at shocks. we show that jets stable to mhd instabilities show expected trends of regular flow of cres in the jet spine and acceleration at a hotspot followed by a settling backflow. however, unstable jets create complex shock structures at the jet head (kink instability), the jet spine-cocoon interface, and the cocoon itself (kelvin-helmholtz modes). cres after exiting jet head undergo further shock crossings in such scenarios and are re-accelerated in the cocoon. cres with different trajectories in turbulent cocoons have different evolutionary history with different spectral parameters. thus, at the same spatial location, there is mixing of different cre populations, resulting in a complex total cre spectrum when averaged over a given area. cocoons of unstable jets can have an excess build up of energetic electrons due to re-acceleration at turbulence driven shocks and slowed expansion of the decelerated jet. this will add to the non-thermal energy budget of the cocoon. | simulating the dynamics and synchrotron emission from relativistic jets - ii. evolution of non-thermal electrons |
quantum error correction holds the key to scaling up quantum computers. cosmic ray events severely impact the operation of a quantum computer by causing chip-level catastrophic errors, essentially erasing the information encoded in a chip. here, we present a distributed error correction scheme to combat the devastating effect of such events by introducing an additional layer of quantum erasure error correcting code across separate chips. we show that our scheme is fault tolerant against chip-level catastrophic errors and discuss its experimental implementation using superconducting qubits with microwave links. our analysis shows that in state-of-the-art experiments, it is possible to suppress the rate of these errors from 1 per 10 s to less than 1 per month. | distributed quantum error correction for chip-level catastrophic errors |
in the universe, matter outside of stars and compact objects is mostly composed of collisionless plasma. the interaction of a supersonic plasma flow with an obstacle results in collisionless shocks that are often associated with intense nonthermal radiation and the production of cosmic ray particles. motivated by simulations of non-relativistic high-mach-number shocks in supernova remnants, we investigate the instabilities excited by relativistic electron beams in the extended foreshock of oblique shocks. the phase-space distributions in the inner and outer foreshock regions are derived with a particle-in-cell simulation of the shock and used as initial conditions for simulations with periodic boundary conditions to study their relaxation toward equilibrium. we find that the observed electron-beam instabilities agree very well with the predictions of a linear dispersion analysis: the electrostatic electron-acoustic instability dominates in the outer region of the foreshock, while the denser electron beams in the inner foreshock drive the gyroresonant oblique-whistler instability. | the electron foreshock at high-mach-number non-relativistic oblique shocks |
the atmospheric depth of the air shower maximum xmax is an observable commonly used for the determination of the nuclear mass composition of ultra-high energy cosmic rays. direct measurements of xmax are performed using observations of the longitudinal shower development with fluorescence telescopes. at the same time, several methods have been proposed for an indirect estimation of xmax from the characteristics of the shower particles registered with surface detector arrays. in this paper, we present a deep neural network (dnn) for the estimation of xmax. the reconstruction relies on the signals induced by shower particles in the ground based water-cherenkov detectors of the pierre auger observatory. the network architecture features recurrent long short-term memory layers to process the temporal structure of signals and hexagonal convolutions to exploit the symmetry of the surface detector array. we evaluate the performance of the network using air showers simulated with three different hadronic interaction models. thereafter, we account for long-term detector effects and calibrate the reconstructed xmax using fluorescence measurements. finally, we show that the event-by-event resolution in the reconstruction of the shower maximum improves with increasing shower energy and reaches less than 25 g/cm2 at energies above 2 × 1019 ev. | deep-learning based reconstruction of the shower maximum xmax using the water-cherenkov detectors of the pierre auger observatory |
determining the atomic and molecular content of the interstellar medium (ism) is of fundamental importance to understand the star-formation process. although there exist various three-dimensional hydro-chemical codes modelling the ism, they are computationally expensive and inefficient for studies over a large parameter space. building on our earlier approach, we present pdfchem, a novel algorithm that models the cold ism at moderate and large scales using functions connecting the quantities of the local (av, eff) and the observed (av, obs) visual extinctions, and the local number density, nh, with probability density functions (pdf) of av, obs on cloud scales typically tens-to-hundreds of pc as an input. for any given av, obs-pdf, the algorithm instantly computes the average abundances of the most important species (h i, h2, c ii, c i, co, oh, oh+, h2o+, ch, hco+) and performs radiative transfer calculations to estimate the average emission of the most commonly observed lines ([c ii] 158$\mu$m, both [c i] fine-structure lines and the first five rotational transitions of 12co). we examine two av, obs-pdfs corresponding to a non-star-forming and a star-forming ism region, under a variety of environmental parameters combinations. these cover far-ultraviolet intensities in the range of χ/χ0 = 10-1 - 103, cosmic ray ionization rates in the range of $\zeta _{\rm cr}=10^{-17}-10^{-13}\, {\rm s}^{-1}$ and metallicities in the range of $z=0.1-2\, {\rm z}_{\odot }$. pdfchem is fast, easy to use, reproduces the pdr quantities of the hydrodynamical models, and can be used directly with observed data of the cold ism. | pdfchem: a new fast method to determine ism properties and infer environmental parameters using probability distributions |
the cosmos-uk observation network has been providing field-scale soil moisture and hydrometeorological measurements across the uk since 2013. at the time of publication a total of 51 cosmos-uk sites have been established, each delivering high-temporal resolution data in near-real time. each site utilizes a cosmic-ray neutron sensor, which counts epithermal neutrons at the land surface. these measurements are used to derive field-scale near-surface soil water content, which can provide unique insight for science, industry, and agriculture by filling a scale gap between localized point soil moisture and large-scale satellite soil moisture datasets. additional soil physics and meteorological measurements are made by the cosmos-uk network including precipitation, air temperature, relative humidity, barometric pressure, soil heat flux, wind speed and direction, and components of incoming and outgoing radiation. these near-real-time observational data can be used to improve the performance of hydrological models, validate remote sensing products, improve hydro-meteorological forecasting, and underpin applications across a range of other scientific fields. the most recent version of the cosmos-uk dataset is publically available at https://doi.org/10.5285/b5c190e4-e35d-40ea-8fbe-598da03a1185 (stanley et al., 2021). | cosmos-uk: national soil moisture and hydrometeorology data for environmental science research |
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