abstract stringlengths 3 192k | title stringlengths 4 857 |
|---|---|
we point out a new type of diurnal effect for the cosmic ray boosted dark matter (dm). the dm-nucleon interactions not only allow the direct detection of dm with nuclear recoils but also allow cosmic rays to scatter with and boost the nonrelativistic dm to higher energies. if the dm-nuclei scattering cross sections are sufficiently large, the dm flux is attenuated as it propagates through the earth, leading to a strong diurnal modulation. this diurnal modulation provides another prominent signature for the direct detection of boosted sub-gev dm, in addition to signals with higher recoil energy. | diurnal effect of sub-gev dark matter boosted by cosmic rays |
bursts of gamma ray showers have been observed in coincidence with downward propagating negative leaders in lightning flashes by the telescope array surface detector (tasd). the tasd is a 700-km2 cosmic ray observatory located in southwestern utah, usa. in data collected between 2014 and 2016, correlated observations showing the structure and temporal development of three shower-producing flashes were obtained with a 3-d lightning mapping array, and electric field change measurements were obtained for an additional seven flashes, in both cases colocated with the tasd. national lightning detection network information was also used throughout. the showers arrived in a sequence of 2-5 short-duration (≤10 μs) bursts over time intervals of several hundred microseconds and originated at an altitude of ≃3-5 km above ground level during the first 1-2 ms of downward negative leader breakdown at the beginning of cloud-to-ground lightning flashes. the shower footprints, associated waveforms and the effect of atmospheric propagation indicate that the showers consist primarily of downward-beamed gamma radiation. this has been supported by geant simulation studies, which indicate primary source fluxes of ≃1012-1014 photons for 16° half-angle beams. we conclude that the showers are terrestrial gamma ray flashes, similar to those observed by satellites, but that the ground-based observations are more representative of the temporal source activity and are also more sensitive than satellite observations, which detect only the most powerful terrestrial gamma ray flashes. | gamma ray showers observed at ground level in coincidence with downward lightning leaders |
the arrival directions of galactic cosmic rays are highly isotropic. this is expected from the presence of turbulent magnetic fields in our galactic environment that repeatedly scatter charged cosmic rays during propagation. however, various cosmic ray observatories have identified weak anisotropies of various angular sizes and with relative intensities of up to a level of 1 part in 1000. whereas large-scale anisotropies are generally predicted by standard diffusion models, the appearance of small-scale anisotropies down to an angular size of 10° is surprising. in this review, we summarize the current experimental situation for both the large-scale and small-scale anisotropies. we address some of the issues in comparing different experimental results and remaining questions in interpreting the observed large-scale anisotropies. we then review the standard diffusive picture and its difficulty in producing the small-scale anisotropies. having set the stage, we review the various ideas and models put forward for explaining the small-scale anisotropies. | origin of small-scale anisotropies in galactic cosmic rays |
precise measurements of the boron-to-carbon and boron-to-oxygen ratios by dampe show clear hardenings around 100 gev/n, which provide important implications on the production, propagation, and interaction of galactic cosmic rays. in this work we investigate a number of models proposed in literature in light of the dampe findings. these models can roughly be classified into two classes, driven by propagation effects or by source ones. among these models discussed, we find that the re-acceleration of cosmic rays, during their propagation, by random magnetohydrodynamic waves may not reproduce sufficient hardenings of b/c and b/o, and an additional spectral break of the diffusion coefficient is required. the other models can properly explain the hardenings of the ratios. however, depending on simplifications assumed, the models differ in their quality in reproducing the data in a wide energy range. the models with significant re-acceleration effect will under-predict low-energy antiprotons but over-predict low-energy positrons, and the models with secondary production at sources over-predict high-energy antiprotons. for all models high-energy positron excess exists. | interpretations of the cosmic ray secondary-to-primary ratios measured by dampe |
local interstellar spectra (lis) for protons, helium, and antiprotons are built using the most recent experimental results combined with state-of-the-art models for propagation in the galaxy and heliosphere. two propagation packages, galprop and helmod, are combined to provide a single framework that is run to reproduce direct measurements of cosmic-ray (cr) species at different modulation levels and at both polarities of the solar magnetic field. to do so in a self-consistent way, an iterative procedure was developed, where the galprop lis output is fed into helmod, providing modulated spectra for specific time periods of selected experiments to compare with the data; the helmod parameter optimization is performed at this stage and looped back to adjust the lis using the new galprop run. the parameters were tuned with the maximum likelihood procedure using an extensive data set of proton spectra from 1997 to 2015. the proposed lis accommodate both the low-energy interstellar cr spectra measured by voyager 1 and the high-energy observations by bess, pamela, ams-01, and ams-02 made from the balloons and near-earth payloads; it also accounts for ulysses counting rate features measured out of the ecliptic plane. the found solution is in a good agreement with proton, helium, and antiproton data by ams-02, bess, and pamela in the whole energy range. | solution of heliospheric propagation: unveiling the local interstellar spectra of cosmic-ray species |
the cosmic background (cb) radiation, encompassing the sum of emission from all sources outside our own milky way galaxy across the entire electromagnetic spectrum, is a fundamental phenomenon in observational cosmology. many experiments have been conceived to measure it (or its constituents) since the extragalactic universe was first discovered; in addition to estimating the bulk (cosmic monopole) spectrum, directional variations have also been detected over a wide range of wavelengths. here we gather the most recent of these measurements and discuss the current status of our understanding of the cb from radio to $\gamma$-ray energies. using available data in the literature we piece together the sky-averaged intensity spectrum, and discuss the emission processes responsible for what is observed. we examine the effect of perturbations to the continuum spectrum from atomic and molecular line processes and comment on the detectability of these signals. we also discuss how one could in principle obtain a complete census of the cb by measuring the full spectrum of each spherical harmonic expansion coefficient. this set of spectra of multipole moments effectively encodes the entire statistical history of nuclear, atomic and molecular processes in the universe. | the spectrum of the universe |
the flavor composition of high-energy astrophysical neutrinos can reveal the physics governing their production, propagation, and interaction. the icecube collaboration has published the first experimental determination of the ratio of the flux in each flavor to the total. we present, as a theoretical counterpart, new results for the allowed ranges of flavor ratios at earth for arbitrary flavor ratios in the sources. our results will allow icecube to more quickly identify when their data imply standard physics, a general class of new physics with arbitrary (incoherent) combinations of mass eigenstates, or new physics that goes beyond that, e.g., with terms that dominate the hamiltonian at high energy. | theoretically palatable flavor combinations of astrophysical neutrinos |
we present a measurement of the combined νe+ν¯e flux-averaged charged-current inclusive cross section on argon using data from the microboone liquid argon time projection chamber (lartpc) at fermilab. using the off-axis flux from the numi beam, microboone has reconstructed 214 candidate νe+ν¯e interactions with an estimated exposure of 2.4 ×1020 protons on target. given the estimated purity of 38.6%, this implies the observation of 80 νe+ν¯e events in argon, the largest such sample to date. the analysis includes the first demonstration of a fully automated application of a de/dx-based particle discrimination technique of electron- and photon-induced showers in a lartpc neutrino detector. the main background for this first νe analysis is cosmic ray contamination. significantly higher purity is expected in underground detectors, as well as with next-generation reconstruction algorithms. we measure the νe+ν¯e flux-averaged charged-current total cross section to be 6.84 ±1.51 (stat ) ±2.33 (sys ) ×10-39 cm2/nucleon, for neutrino energies above 250 mev and an average neutrino flux energy of 905 mev when this threshold is applied. the measurement is sensitive to neutrino events where the final state electron momentum is above 48 mev /c , includes the entire angular phase space of the electron, and is in agreement with the theoretical predictions from genie and nuwro. this measurement is also the first demonstration of electron-neutrino reconstruction in a surface lartpc in the presence of cosmic-ray backgrounds, which will be a crucial task for surface experiments like those that comprise the short-baseline neutrino program at fermilab. | measurement of the flux-averaged inclusive charged-current electron neutrino and antineutrino cross section on argon using the numi beam and the microboone detector |
an excess of γ rays in the data measured by the fermi large area telescope in the direction of the galactic center has been reported in several publications. this excess, labeled as the galactic center excess (gce), is detected analyzing the data with different interstellar emission models, point source catalogs and analysis techniques. the characteristics of the gce, recently measured with unprecedented precision, are all compatible with dark matter particles (dm) annihilating in the main halo of our galaxy, even if other interpretations are still not excluded. we investigate the dm candidates that fit the observed gce spectrum and spatial morphology. we assume a simple scenario with dm annihilating into a single channel but we inspect also more complicated models with two and three channels. we perform a search for a γ -ray flux from a list of 48 milky way dwarf spheroidal galaxies (dsphs) using state-of-the-art estimation of the dm density in these objects. since we do not find any significant signal from the dsphs, we put upper limits on the annihilation cross section that result to be compatible with the dm candidate that fits the gce. however, we find that the gce dm signal is excluded at the 95% confidence level by the ams-02 p ¯ flux data for all purely hadronic (semihadronic) channels unless the diffusive halo size l is smaller than 1.7 kpc (2.6 kpc). such a small diffusion halo is at the 2 σ significance lower limit for the results inferred from fluxes of radioactive cosmic rays and is in some tension with results from analyses performed with radio and γ -ray data. furthermore, ams-02 e+ data rule out the gce dm interpretation with pure or partial annihilation into e+e-. the only dm candidate that fits the gce spectrum and fulfills all constraints obtained with the combined dsphs analysis and the ams-02 p ¯ and e+ data annihilates purely (or very dominantly) into μ+μ-, has a mass of ∼60 gev and roughly a thermal cross section. | multimessenger constraints on the dark matter interpretation of the f e r m i -lat galactic center excess |
i present a short overview of the latest developments in indirect searches for dark matter using gamma rays, x-rays, charged cosmic rays, micro waves, radio waves, and neutrinos. i briefly outline key past, present, and future experiments and their search strategies. in several searches there are exciting anomalies which could potentially be emerging dark matter signals. i discuss these anomalous signals, and some future prospects to determine their origins. | indirect detection of dark matter in the galaxy |
if gamma-ray bursts are at cosmological distances, they must be gravitationally lensed occasionally1,2. the detection of lensed images with millisecond-to-second time delays provides evidence for intermediate-mass black holes, a population that has been difficult to observe. several studies have searched for these delays in gamma-ray burst light curves, which would indicate an intervening gravitational lens3-6. among the ~104 gamma-ray bursts observed, there have been a handful of claimed lensing detections7, but none have been statistically robust. here we present a bayesian analysis identifying gravitational lensing in the light curve of grb 950830. the inferred lens mass ml depends on the unknown lens redshift zl, and is given by (1 +zl ) ml=5 .5−0.9+1.7×1 04m⊙ (90% credibility), which we interpret as evidence for an intermediate-mass black hole. the most probable configuration, with a lens redshift zl ≈ 1 and a gamma-ray burst redshift zs ≈ 2, yields a present-day number density of about 2 .3−1.6+4.9×1 03mpc−3 (90% credibility) with a dimensionless energy density ωimbh≈4 .6−3.3+9.8×1 0−4 . the false alarm probability for this detection is ~0.6% with trial factors. while it is possible that grb 950830 was lensed by a globular cluster, it is unlikely as we infer a cosmic density inconsistent with predictions for globular clusters ωgc ≈ 8 × 10−6 at 99.8% credibility. if a significant intermediate-mass black hole population exists, it could provide the seeds for the growth of supermassive black holes in the early universe. | evidence for an intermediate-mass black hole from a gravitationally lensed gamma-ray burst |
understanding the production mechanism of light (anti-)nuclei in high-energy nuclear collisions and cosmic rays has been a long-standing problem in nuclear physics. in the present study, we develop a stochastic method to solve the relativistic kinetic equations for light nuclei production from many-body reactions with the inclusion of their finite sizes. the present approach gives an excellent description of the deuteron and helium-3 data from central au+au (pb+pb) collisions at $\sqrt{s_{\rm nn}}$ $=$ $200~\rm gev$ ($2.76~\rm tev$). it can also naturally explain their suppressed production in $pp$ collisions at 7 tev as a result of their finite sizes. | relativistic kinetic approach to light nuclei production in high-energy nuclear collisions |
a precise measurement of the cosmic-ray proton spectrum with the calorimetric electron telescope (calet) is presented in the energy interval from 50 gev to 60 tev, and the observation of a softening of the spectrum above 10 tev is reported. the analysis is based on the data collected during ∼6.2 years of smooth operations aboard the international space station and covers a broader energy range with respect to the previous proton flux measurement by calet, with an increase of the available statistics by a factor of ∼2.2 . above a few hundred gev we confirm our previous observation of a progressive spectral hardening with a higher significance (more than 20 sigma). in the multi-tev region we observe a second spectral feature with a softening around 10 tev and a spectral index change from -2.6 to -2.9 consistently, within the errors, with the shape of the spectrum reported by dampe. we apply a simultaneous fit of the proton differential spectrum which well reproduces the gradual change of the spectral index encompassing the lower energy power-law regime and the two spectral features observed at higher energies. | observation of spectral structures in the flux of cosmic-ray protons from 50 gev to 60 tev with the calorimetric electron telescope on the international space station |
we unify the feeding and feedback of supermassive black holes with the global properties of galaxies, groups, and clusters by linking for the first time the physical mechanical efficiency at the horizon and megaparsec scale. the macro hot halo is tightly constrained by the absence of overheating and overcooling as probed by x-ray data and hydrodynamic simulations ({\varepsilon }{bh}≃ {10}-3 {t}{{x},7.4}). the micro flow is shaped by general-relativistic effects tracked by state-of-the-art gr-rmhd simulations ({\varepsilon }\bullet ≃ 0.03). the supermassive black hole properties are tied to the x-ray halo temperature {t}{{x}}, or related cosmic scaling relation (as {l}{{x}}). the model is minimally based on first principles, such as conservation of energy and mass recycling. the inflow occurs via chaotic cold accretion (cca), the rain of cold clouds condensing out of the quenched cooling flow and then recurrently funneled via inelastic collisions. within 100s gravitational radii, the accretion energy is transformed into ultrafast 104 km s-1 outflows (ufos) ejecting most of the inflowing mass. at larger radii, the energy-driven outflow entrains progressively more mass: at roughly kiloparsec scale, the velocities of the hot/warm/cold outflows are a few 103, 1000, and 500 km s-1, with median mass rates ∼ 10, 100, and several 100 {m}⊙yr-1, respectively. the unified cca model is consistent with the observations of nuclear ufos and ionized, neutral, and molecular macro outflows. we provide step-by-step implementation for subgrid simulations, (semi)analytic works, or observational interpretations that require self-regulated agn feedback at coarse scales, avoiding the a-posteriori fine-tuning of efficiencies. | unifying the micro and macro properties of agn feeding and feedback |
the 21-cm power spectrum (ps) has been shown to be a powerful discriminant of reionization and cosmic dawn astrophysical parameters. however, the 21-cm tomographic signal is highly non-gaussian. therefore there is additional information which is wasted if only the ps is used for parameter recovery. here we showcase astrophysical parameter recovery directly from 21-cm images, using deep learning with convolutional neural networks (cnn). using a data base of 2d images taken from 10 000 21-cm light-cones (each generated from different cosmological initial conditions), we show that a cnn is able to recover parameters describing the first galaxies: (i) tvir , their minimum host halo virial temperatures (or masses) capable of hosting efficient star formation; (ii) ζ , their typical ionizing efficiencies; (iii) lx/sfr , their typical soft-band x-ray luminosity to star formation rate; and (iv) e0 , the minimum x-ray energy capable of escaping the galaxy into the igm. for most of their allowed ranges, log tvir and log lx/sfr are recovered with < 1 per cent uncertainty, while ζ and e0 are recovered with ∼ 10 per cent uncertainty. our results are roughly comparable to the accuracy obtained from monte carlo markov chain sampling of the ps with 21cmmc for the two mock observations analysed previously, although we caution that we do not yet include noise and foreground contaminants in this proof-of-concept study. | deep learning from 21-cm tomography of the cosmic dawn and reionization |
we compute the γ-ray and neutrino diffuse emission of the galaxy on the basis of a recently proposed phenomenological model characterized by radially dependent cosmic-ray (cr) transport properties. we show how this model, designed to reproduce both fermi-lat γ-ray data and local cr observables, naturally reproduces the anomalous tev diffuse emission observed by milagro in the inner galactic plane. above 100 tev our picture predicts a neutrino flux that is about five (two) times larger than the neutrino flux computed with conventional models in the galactic center region (full-sky). explaining in that way up to ∼25% of the flux measured by icecube, we reproduce the full-sky icecube spectrum adding an extra-galactic component derived from the muonic neutrinos flux in the northern hemisphere. we also present precise predictions for the galactic plane region where the flux is dominated by the galactic emission. | the gamma-ray and neutrino sky: a consistent picture of fermi-lat, milagro, and icecube results |
light nonrelativistic components of the galactic dark matter halo elude direct detection constraints because they lack the kinetic energy to create an observable recoil. however, cosmic rays can upscatter dark matter to significant energies, giving direct detection experiments access to previously unreachable regions of parameter space at very low dark matter mass. in this work we extend the cosmic-ray dark matter formalism to models of inelastic dark matter and show that previously inaccessible regions of the mass-splitting p arameter space can be probed. conventional direct detection of nonrelativistic halo dark matter is limited to mass splittings of δ ∼10 kev and is highly mass dependent. we find that including the effect of cosmic-ray upscattering can extend the reach to mass splittings of δ ∼100 mev and maintain that reach at much lower dark matter mass. | cosmic-ray upscattered inelastic dark matter |
the cosmic 21 cm signal is set to revolutionize our understanding of the early universe, allowing us to probe the 3d temperature and ionization structure of the intergalactic medium (igm). it will open a window on to the unseen first galaxies, showing us how their uv and x-ray photons drove the cosmic milestones of the epoch of reionization (eor) and epoch of heating (eoh). to facilitate parameter inference from the 21 cm signal, we previously developed 21cmmc: a monte carlo markov chain sampler of 3d eor simulations. here, we extend 21cmmc to include simultaneous modelling of the eoh, resulting in a complete bayesian inference framework for the astrophysics dominating the observable epochs of the cosmic 21 cm signal. we demonstrate that second-generation interferometers, the hydrogen epoch of reionization array and square kilometre array will be able to constrain ionizing and x-ray source properties of the first galaxies with a fractional precision of the order of ∼1-10 per cent (1σ). the ionization history of the universe can be constrained to within a few percent. using our extended framework, we quantify the bias in eor parameter recovery incurred by the common simplification of a saturated spin temperature in the igm. depending on the extent of overlap between the eor and the eoh, the recovered astrophysical parameters can be biased by ∼3σ-10σ. | simultaneously constraining the astrophysics of reionization and the epoch of heating with 21cmmc |
gamma-ray bursts (grbs) are generally believed to be efficient particle accelerators. in the presence of energetic protons in a grb jet, interactions between these protons and the intense radiation field of the grb are supposed to induce an electromagnetic cascade. electrons/positrons generated in the cascade will produce an additional spectrum of a robust feature, which is in the form of a power-law distribution up to a gev regime with an index of ≲2. we suggest that measurements of the fermi large area telescope at the gev band can provide independent constraints on the key grb model parameters such as the dissipation radius, the jet's bulk lorentz factor, and the baryon loading factor. taking grb 221009a, the brightest grb ever detected, as an example, we show that the constraints from gev gamma-ray emission may be more stringent than that from the neutrino observation, providing us with deep insight into the origin of grbs. | constraints on gamma-ray burst models from grb 221009a: gev gamma rays versus high-energy neutrinos |
the formation of a protostellar disc is a natural outcome during the star formation process. as gas in a molecular cloud core collapses under self-gravity, the angular momentum of the gas will slow its collapse on small scales and promote the formation of a protostellar disc. although the angular momenta of dense star-forming cores remain to be fully characterized observationally, existing data indicates that typical cores have enough angular momenta to form relatively large, 100 au-scale, rotationally supported discs, as illustrated by hydrodynamic simulations. however, the molecular clouds are observed to be permeated by magnetic fields, which can in principle strongly affect the evolution of angular momentum during the core collapse through magnetic braking. indeed, in the ideal magnetohydrodynamic (mhd) limit, magnetic braking has been shown to be so efficient as to remove essentially all of the angular momentum of the material close to the forming star such that disc formation is suppressed. this failure to produce discs in idealized cores is known as the magnetic braking catastrophe. the catastrophe must be averted in order for the all-important rotationally supported discs to appear, but when and how this happens remains debated. we review the resolutions proposed to date, with emphasis on misalignment, turbulence and especially non-ideal effects. non-ideal mhd accounts for charged and neutral species, making it a natural extension to the ideal mhd approximation, since molecular clouds are only weakly ionized. the dissipative non-ideal effects diffuse the magnetic field to weaken it, and the dispersive term redirects the magnetic field to promote or hinder disc formation, dependent upon the magnetic geometry. when self-consistently applying non-ideal processes, rotationally supported discs of at least tens of au form, thus preventing the magnetic braking catastrophe. the non-ideal processes are sensitive to the magnetic field strength, cosmic ray ionization rate, and gas and dust grain properties, thus a complete understanding of the host molecular cloud is required. therefore, the properties of the host molecular cloud - and especially its magnetic field - cannot be ignored when numerically modelling the formation and evolution of protostellar discs. | the role of magnetic fields in the formation of protostellar discs |
late time decay of very heavy dark matter is considered as one of the possible explanations for diffuse pev neutrinos observed in icecube. we consider implications of multimessenger constraints, and show that proposed models are marginally consistent with the diffuse γ -ray background data. critical tests are possible by a detailed analysis and identification of the sub-tev isotropic diffuse γ -ray data observed by fermi and future observations of sub-pev γ rays by observatories like hawc or tibet as +md . in addition, with several-year observations by next-generation telescopes such as icecube-gen2, muon neutrino searches for nearby dark matter halos such as the virgo cluster should allow us to rule out or support the dark matter models, independently of γ -ray and anisotropy tests. | testing the dark matter scenario for pev neutrinos observed in icecube |
in this work, we present detailed constraints on the metallicity dependence of the high-mass x-ray binary (hmxb) x-ray luminosity function (xlf). we analyze ≈5 ms of chandra data for 55 actively star-forming galaxies at d ≲ 30 mpc, with gas-phase metallicities spanning $12+\mathrm{log}({\rm{o}}/{\rm{h}})$ ≈ 7-9.2. within the galactic footprints, our sample contains a total of 1311 x-ray point sources, of which ≈49% are expected to be hmxbs, with the remaining sources likely to be low-mass x-ray binaries (lmxbs; ≈22%) and unrelated background sources (≈29%). we construct a model that successfully characterizes the average hmxb xlf over the full metallicity range. we demonstrate that the sfr-normalized hmxb xlf shows clear trends with metallicity, showing steadily increasing numbers of luminous and ultraluminous x-ray sources ( $\mathrm{log}l$ (erg s-1) = 38-40.5) with declining metallicity. however, we find that the low-luminosity ( $\mathrm{log}l$ (erg s-1) = 36-38) hmxb xlf appears to show a nearly constant sfr scaling and slope with metallicity. our model provides a revised scaling relation of integrated lx/sfr versus $12+\mathrm{log}({\rm{o}}/{\rm{h}})$ , and a new characterization of its sfr-dependent stochastic scatter. the general trend of this relation is broadly consistent with past studies based on integrated galaxy emission; however, our model suggests that this relation is driven primarily by the high-luminosity end of the hmxb xlf. our results have implications for binary population synthesis models, the nature of super-eddington accreting objects (e.g., ultraluminous x-ray sources), recent efforts to identify active galactic nucleus candidates in dwarf galaxies, and the x-ray radiation fields in the early universe during the epoch of cosmic heating at z ≳ 10. | the metallicity dependence of the high-mass x-ray binary luminosity function |
we present the results and methodology of a search for neutrinos produced in the decay of charged pions created in interactions between protons and gamma-rays during the prompt emission of 807 gamma-ray bursts (grbs) over the entire sky. this three-year search is the first in icecube for shower-like cherenkov light patterns from electron, muon, and tau neutrinos correlated with grbs. we detect five low-significance events correlated with five grbs. these events are consistent with the background expectation from atmospheric muons and neutrinos. the results of this search in combination with those of icecube's four years of searches for track-like cherenkov light patterns from muon neutrinos correlated with northern-hemisphere grbs produce limits that tightly constrain current models of neutrino and ultra high energy cosmic ray production in grb fireballs. | an all-sky search for three flavors of neutrinos from gamma-ray bursts with the icecube neutrino observatory |
cosmic rays are the highest-energy particles found in nature. measurements of the mass composition of cosmic rays with energies of 1017-1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. it has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. cosmic rays initiate air showers—cascades of secondary particles in the atmosphere—and their masses can be inferred from measurements of the atmospheric depth of the shower maximum (xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground. current measurements have either high uncertainty, or a low duty cycle and a high energy threshold. radio detection of cosmic rays is a rapidly developing technique for determining xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. the radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front. here we report radio measurements of xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017-1017.5 electronvolts. this high resolution in xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017-1017.5 electronvolt range. | a large light-mass component of cosmic rays at 1017-1017.5 electronvolts from radio observations |
context. a large-scale magnetic field permeates our galaxy and is involved in a variety of astrophysical processes, such as star formation and cosmic ray propagation. dust polarization has been proven to be one of the most powerful observables for studying the field properties in the interstellar medium (ism). however, it does not provide a direct measurement of its strength. different methods have been developed that employ both polarization and spectroscopic data in order to infer the field strength. the most widely applied method was developed by davis (1951, phys. rev., 81, 890) and chandrasekhar & fermi (1953, apj, 118, 1137), hereafter dcf. the dcf method relies on the assumption that isotropic turbulent motions initiate the propagation of alfvén waves. observations, however, indicate that turbulence in the ism is anisotropic and that non-alfvénic (compressible) modes may be important.aims: our goal is to develop a new method for estimating the field strength in the ism that includes the compressible modes and does not contradict the anisotropic properties of turbulence.methods: we adopt the following assumptions: (1) gas is perfectly attached to the field lines; (2) field line perturbations propagate in the form of small-amplitude magnetohydrodynamic (mhd) waves; and (3) turbulent kinetic energy is equal to the fluctuating magnetic energy. we use simple energetics arguments that take the compressible modes into account to estimate the strength of the magnetic field.results: we derive the following equation: b0 = √2πρδv/√δθ, where ρ is the gas density, δv is the rms velocity as derived from the spread of emission lines, and δθ is the dispersion of polarization angles. we produce synthetic observations from 3d mhd simulations, and we assess the accuracy of our method by comparing the true field strength with the estimates derived from our equation. we find a mean relative deviation of 17%. the accuracy of our method does not depend on the turbulence properties of the simulated model. in contrast, the dcf method, even when combined with the hildebrand et al. (2009, apj, 696, 567) and houde et al. (2009, apj, 706, 1504) method, systematically overestimates the field strength.conclusions: compressible modes can significantly affect the accuracy of methods that are based solely on alfvénic modes. the formula that we propose includes compressible modes; however, it is applicable only in regions with no self-gravity. density inhomogeneities may bias our estimates to lower values. | high-accuracy estimation of magnetic field strength in the interstellar medium from dust polarization |
aims: the circumgalactic medium (cgm) plays an important role in galaxy evolution as the main interface between the star-forming body of galaxies and the surrounding cosmic network of in- and out-flowing matter. in this work, we aim to characterize the hot phase of the cgm in a large sample of galaxies using recent soft-x-ray observations made by srg/erosita.methods: we stack x-ray events from the `erosita final equatorial depth survey' (efeds) around central galaxies in the 9hr field of the `galaxy and mass assembly' (gama) survey to construct radially projected x-ray luminosity profiles in the 0.5-2 kev rest frame energy band as a function of their stellar mass and specific star formation rate. we consider samples of quiescent (star-forming) galaxies in the stellar mass range 2 × 1010-1012 m⊙ (3 × 109-6 × 1011 m⊙).results: for quiescent galaxies, the x-ray profiles are clearly extended throughout the available mass range; however, the measured profile is likely biased high because of projection effects, as these galaxies tend to live in dense and hot environments. for the most massive star-forming samples (≥1011 m⊙), there is a hint of detection of extended emission. on the other hand, for star-forming galaxies with < 1011 m⊙ the x-ray stacked profiles are compatible with unresolved sources and are consistent with the expected emission from faint active galactic nuclei (agn) and x-ray binaries. we measure for the first time the mean relation between average x-ray luminosity and stellar mass separately for quiescent and star-forming galaxies. we find that the relation is different for the two galaxy populations: high-mass (≥1011 m⊙) star-forming or quiescent galaxies follow the expected scaling of virialized hot haloes, while lower mass star-forming galaxies show a less prominent luminosity and a weaker dependence on stellar mass consistent with empirical models of the population of weak agn. when comparing our results with state-of-the-art numerical simulations (illustristng and eagle), we find overall consistency on the average emission on large (> 80 kpc) scales at masses ≥1011 m⊙, but disagreement on the small scales, where brighter-than-observed compact cores are predicted. the simulations also do not predict the clear differentiation that we observe between quiescent and star-forming galaxies in our samples.conclusions: this is a stepping stone towards a more profound understanding of the hot phase of the cgm, which holds a key role in the regulation of star formation. future analysis using erosita all-sky survey data, combined with future generation galaxy evolution surveys, shall provide much enhanced quantitative measurements and mapping of the cgm and its hot phase(s). | the erosita final equatorial depth survey (efeds). x-ray emission around star-forming and quiescent galaxies at 0.05 < z < 0.3 |
muography is an imaging technique based on the measurement of absorption profiles for muons as they pass through rocks and earth. muons are produced in the interactions of high-energy cosmic rays in the earth's atmosphere. the technique is conceptually similar to usual x-ray radiography, but with extended capabilities of investigating over much larger thicknesses of matter thanks to the penetrating power of high-energy muons. over the centuries a complex system of cavities has been excavated in the yellow tuff of mt. echia, the site of the earliest settlement of the city of naples in the 8th century bc. a new generation muon detector designed by us, was installed under a total rock overburden of about 40 metres. a 26 days pilot run provided about 14 millions of muon events. a comparison of the measured and expected muon fluxes improved the knowledge of the average rock density. the observation of known cavities proved the validity of the muographic technique. hints on the existence of a so far unknown cavity was obtained. the success of the investigation reported here demonstrates the substantial progress of muography in underground imaging and is likely to open new avenues for its widespread utilisation. | imaging of underground cavities with cosmic-ray muons from observations at mt. echia (naples) |
multiwavelength observations indicate that some starburst galaxies show a dominant nonthermal contribution from their central region. these active galactic nuclei (agn)-starburst composites are of special interest, as both phenomena on their own are potential sources of highly energetic cosmic rays and associated γ-ray and neutrino emission. in this work, a homogeneous, steady-state two-zone multimessenger model of the nonthermal emission from the agn corona as well as the circumnuclear starburst region is developed and subsequently applied to the case of ngc 1068, which has recently shown some first indications of high-energy neutrino emission. here, we show that the entire spectrum of multimessenger data-from radio to γ-rays including the neutrino constraint-can be described very well if both, starburst and agn corona, are taken into account. using only a single emission region is not sufficient. | solving the multimessenger puzzle of the agn-starburst composite galaxy ngc 1068 |
the cosmic-ray extremely distributed observatory (credo) is a newly formed, global collaboration dedicated to observing and studying cosmic rays (cr) and cosmic-ray ensembles (cre): groups of at least two cr with a common primary interaction vertex or the same parent particle. the credo program embraces testing known cr and cre scenarios, and preparing to observe unexpected physics, it is also suitable for multi-messenger and multi-mission applications. perfectly matched to credo capabilities, cre could be formed both within classical models (e.g., as products of photon–photon interactions), and exotic scenarios (e.g., as results of decay of super-heavy dark matter particles). their fronts might be significantly extended in space and time, and they might include cosmic rays of energies spanning the whole cosmic-ray energy spectrum, with a footprint composed of at least two extensive air showers with correlated arrival directions and arrival times. as the cre are predominantly expected to be spread over large areas and, due to the expected wide energy range of the contributing particles, such a cre detection might only be feasible when using all available cosmic-ray infrastructure collectively, i.e., as a globally extended network of detectors. thus, with this review article, the credo collaboration invites the astroparticle physics community to actively join or to contribute to the research dedicated to cre and, in particular, to pool together cosmic-ray data to support specific cre detection strategies. | cosmic-ray extremely distributed observatory |
star formation in galaxies appears to be self-regulated by energetic feedback processes. among the most promising agents of feedback are cosmic rays (crs), the relativistic ion population of interstellar and intergalactic plasmas. in these environments, energetic crs are virtually collisionless and interact via collective phenomena mediated by kinetic-scale plasma waves and large-scale magnetic fields. the enormous separation of kinetic and global astrophysical scales requires a hydrodynamic description. here, we develop a new macroscopic theory for cr transport in the self-confinement picture, which includes cr diffusion and streaming. the interaction between crs and electromagnetic fields of alfvénic turbulence provides the main source of cr scattering, and causes crs to stream along the magnetic field with the alfvén velocity if resonant waves are sufficiently energetic. however, numerical simulations struggle to capture this effect with current transport formalisms and adopt regularization schemes to ensure numerical stability. we extent the theory by deriving an equation for the cr momentum density along the mean magnetic field and include a transport equation for the alfvén-wave energy. we account for energy exchange of crs and alfvén waves via the gyroresonant instability and include other wave damping mechanisms. using numerical simulations, we demonstrate that our new theory enables stable, self-regulated cr transport. the theory is coupled to magnetohydrodynamics, conserves the total energy and momentum, and correctly recovers previous macroscopic cr transport formalisms in the steady-state flux limit. because it is free of tunable parameters, it holds the promise to provide predictable simulations of cr feedback in galaxy formation. | cosmic-ray hydrodynamics: alfvén-wave regulated transport of cosmic rays |
we carry out a comprehensive bayesian correlation analysis between hot halos and direct masses of supermassive black holes (smbhs), by retrieving the x-ray plasma properties (temperature, luminosity, density, pressure, and masses) over galactic to cluster scales for 85 diverse systems. we find new key scalings, with the tightest relation being {m}\bullet -{\text{}}{t}{{x}}, followed by {m}\bullet -{\text{}}{l}{{x}}. the tighter scatter (down to 0.2 dex) and stronger correlation coefficient of all the x-ray halo scalings compared with the optical counterparts (as the {m}\bullet -{σ }{{e}}) suggest that plasma halos play a more central role than stars in tracing and growing smbhs (especially those that are ultramassive). moreover, {m}\bulletcorrelates better with the gas mass than dark matter mass. we show the important role of the environment, morphology, and relic galaxies/coronae, as well as the main departures from virialization/self-similarity via the optical/x-ray fundamental planes. we test the three major channels for smbh growth: hot/bondi-like models have inconsistent anticorrelation with x-ray halos and too low feeding; cosmological simulations find smbh mergers as subdominant over most of cosmic time and too rare to induce a central-limit-theorem effect; the scalings are consistent with chaotic cold accretion, the rain of matter condensing out of the turbulent x-ray halos that sustains a long-term self-regulated feedback loop. the new correlations are major observational constraints for models of smbh feeding/feedback in galaxies, groups, and clusters (e.g., to test cosmological hydrodynamical simulations), and enable the study of smbhs not only through x-rays, but also via the sunyaev-zel’dovich effect (compton parameter), lensing (total masses), and cosmology (gas fractions). | the x-ray halo scaling relations of supermassive black holes |
observations of the cosmic microwave background indicate that baryons account for 5 per cent of the universe’s total energy content. in the local universe, the census of all observed baryons falls short of this estimate by a factor of two. cosmological simulations indicate that the missing baryons have not condensed into virialized haloes, but reside throughout the filaments of the cosmic web (where matter density is larger than average) as a low-density plasma at temperatures of 105-107 kelvin, known as the warm-hot intergalactic medium. there have been previous claims of the detection of warm-hot baryons along the line of sight to distant blazars and of hot gas between interacting clusters. these observations were, however, unable to trace the large-scale filamentary structure, or to estimate the total amount of warm-hot baryons in a representative volume of the universe. here we report x-ray observations of filamentary structures of gas at 107 kelvin associated with the galaxy cluster abell 2744. previous observations of this cluster were unable to resolve and remove coincidental x-ray point sources. after subtracting these, we find hot gas structures that are coherent over scales of 8 megaparsecs. the filaments coincide with over-densities of galaxies and dark matter, with 5-10 per cent of their mass in baryonic gas. this gas has been heated up by the cluster’s gravitational pull and is now feeding its core. our findings strengthen evidence for a picture of the universe in which a large fraction of the missing baryons reside in the filaments of the cosmic web. | warm-hot baryons comprise 5-10 per cent of filaments in the cosmic web |
effects on atmospheric prompt neutrino fluxes of present uncertainties affecting the nucleon composition are studied by using the prosa fit to parton distribution functions (pdfs). the prosa fit extends the precision of the pdfs to low x, which is the kinematic region of relevance for high-energy neutrino production, by taking into account lhcb data on charm and bottom hadroproduction collected at the center-of-mass energy of √{s}=7 tev. in the range of neutrino energies explored by present very large volume neutrino telescopes, it is found that pdf uncertainties are far smaller with respect to those due to renormalization and factorization scale variation and to assumptions on the cosmic ray composition, which at present dominate and limit our knowledge of prompt neutrino fluxes. a discussion is presented on how these uncertainties affect the expected number of atmospheric prompt neutrino events in the analysis of high-energy events characterized by interaction vertices fully contained within the instrumented volume of the detector, performed by the icecube collaboration. [figure not available: see fulltext.] | prompt neutrino fluxes in the atmosphere with prosa parton distribution functions |
global fits of primary and secondary cosmic-ray (cr) fluxes measured by ams-02 have great potential to study cr propagation models and search for exotic sources of antimatter such as annihilating dark matter (dm). previous studies of ams-02 antiprotons revealed a possible hint for a dm signal which, however, could be affected by systematic uncertainties. to test the robustness of such a dm signal, in this work we systematically study two important sources of uncertainties: the antiproton production cross sections needed to calculate the source spectra of secondary antiprotons and the potential correlations in the experimental data, so far not provided by the ams-02 collaboration. to investigate the impact of cross-section uncertainties we perform global fits of cr spectra including a covariance matrix determined from nuclear cross-section measurements. as an alternative approach, we perform a joint fit to both the cr and cross-section data. the two methods agree and show that cross-section uncertainties have a small effect on the cr fits and on the significance of a potential dm signal, which we find to be at the level of 3 σ . correlations in the data can have a much larger impact. to illustrate this effect, we determine possible benchmark models for the correlations in a data-driven method. the inclusion of correlations strongly improves the constraints on the propagation model and, furthermore, enhances the significance of the dm signal up to above 5 σ . our analysis demonstrates the importance of providing the covariance of the experimental data, which is needed to fully exploit their potential. | scrutinizing the evidence for dark matter in cosmic-ray antiprotons |
diffuse filaments connect galaxy clusters to form the cosmic web. detecting these filaments could yield information on the magnetic field strength, cosmic ray population, and temperature of intercluster gas; yet, the faint and large-scale nature of these bridges makes direct detections very challenging. using multiple independent all-sky radio and x-ray maps we stack pairs of luminous red galaxies as tracers for cluster pairs. for the first time, we detect an average surface brightness between the clusters from synchrotron (radio) and thermal (x-ray) emission with ≳5σ significance, on physical scales larger than observed to date (${\ge}3$ mpc). we obtain a synchrotron spectral index of α ≃ -1.0 and estimates of the average magnetic field strength of $30\,\mathrm{ ng} \le b \le 60 $ ng, derived from both equipartition and inverse-compton arguments, implying a 5-15 per cent degree of field regularity when compared with faraday rotation measure estimates. while the x-ray detection is inline with predictions, the average radio signal comes out higher than predicted by cosmological simulations and dark matter annihilation and decay models. this discovery demonstrates that there are connective structures between mass concentrations that are significantly magnetized, and the presence of sufficient cosmic rays to produce detectable synchrotron radiation. | discovery of magnetic fields along stacked cosmic filaments as revealed by radio and x-ray emission |
monitoring soil moisture is still a challenge: it varies strongly in space and time and at various scales while conventional sensors typically suffer from small spatial support. with a sensor footprint up to several hectares, cosmic-ray neutron sensing (crns) is a modern technology to address that challenge. so far, the crns method has typically been applied with single sensors or in sparse national-scale networks. this study presents, for the first time, a dense network of 24 crns stations that covered, from may to july 2019, an area of just 1 km2: the pre-alpine rott headwater catchment in southern germany, which is characterized by strong soil moisture gradients in a heterogeneous landscape with forests and grasslands. with substantially overlapping sensor footprints, this network was designed to study root-zone soil moisture dynamics at the catchment scale. the observations of the dense crns network were complemented by extensive measurements that allow users to study soil moisture variability at various spatial scales: roving (mobile) crns units, remotely sensed thermal images from unmanned areal systems (uass), permanent and temporary wireless sensor networks, profile probes, and comprehensive manual soil sampling. since neutron counts are also affected by hydrogen pools other than soil moisture, vegetation biomass was monitored in forest and grassland patches, as well as meteorological variables; discharge and groundwater tables were recorded to support hydrological modeling experiments. as a result, we provide a unique and comprehensive data set to several research communities: to those who investigate the retrieval of soil moisture from cosmic-ray neutron sensing, to those who study the variability of soil moisture at different spatiotemporal scales, and to those who intend to better understand the role of root-zone soil moisture dynamics in the context of catchment and groundwater hydrology, as well as land-atmosphere exchange processes. the data set is available through the eudat collaborative data infrastructure and is split into two subsets: https://doi.org/10.23728/b2share.282675586fb94f44ab2fd09da0856883 (fersch et al., 2020a) and https://doi.org/10.23728/b2share.bd89f066c26a4507ad654e994153358b (fersch et al., 2020b). | a dense network of cosmic-ray neutron sensors for soil moisture observation in a highly instrumented pre-alpine headwater catchment in germany |
athena (advanced telescope for high-energy astrophysics) is an esa large-class mission, at present under a re-definition "design-to-cost" phase, planned for a prospective launch at l1 orbit in the second half of the 2030s. it will be an observatory alternatively focusing on two complementary instruments: the x-ifu (x-ray integral field unit), a tes (transitionedge sensor)-based kilo-pixel array which is able to perform simultaneous high-grade energy spectroscopy (~3 ev@7 kev) and imaging over 4' fov (field of view), and the wfi (wide field imager), which has good energy spectral resolution (~170 ev@7 kev) and imaging on wide 40' × 40' fov. athena will be a truly transformational observatory, operating in conjunction with other large observatories across the electromagnetic spectrum available in the 2030s like alma, elt, jwst, ska, cta, etc., and in multi-messenger synergies with facilities like ligo a+, advanced virgo+, lisa, icecube and km3net. the italian team is involved in both instruments. it has the co-piship of the cryogenic instrument for which it has to deliver the tes-based cryogenic anticoincidence detector (cryoac) necessary to guarantee the x-ifu sensitivity, degraded by a primary particle background of both solar and galactic cosmic ray (gcr) origins, and by secondary electrons produced by primaries interacting with the materials surrounding the main detector. the outcome of geant4 studies shows the necessity for adopting both active and passive techniques to guarantee the residual particle background at 5 × 10‑3 cts cm‑2 s‑1 kev‑1 level in 2–10 kev scientific bandwidth. the cryoac is a four-pixel detector made of si-suspended absorbers sensed by ir/au teses placed at <1 mm below the main detector. after a brief overview of the athena mission, we will report on the particle background reduction techniques highlighting the impact of the geant4 simulation on the x-ifu focal plane assembly design, then hold a broader discussion on the cryoac program in terms of detection chain system requirements, test, design concept against trade-off studies and programmatic. | the cryogenic anticoincidence detector for the newathena x-ifu instrument: a program overview |
context. robust x-ray temperature measurements of the intracluster medium (icm) of galaxy clusters require an accurate energy-dependent effective area calibration. since the hot gas x-ray emission of galaxy clusters does not vary on relevant timescales, they are excellent cross-calibration targets. moreover, cosmological constraints from clusters rely on accurate gravitational mass estimates, which in x-rays strongly depend on cluster gas temperature measurements. therefore, systematic calibration differences may result in biased, instrument-dependent cosmological constraints. this is of special interest in light of the tension between the planck results of the primary temperature anisotropies of the cosmic microwave background (cmb) and sunyaev-zel'dovich-plus-x-ray cluster-count analyses.aims: we quantify in detail the systematics and uncertainties of the cross-calibration of the effective area between five x-ray instruments, epic-mos1/mos2/pn onboard xmm-newton and acis-i/s onboard chandra, and the influence on temperature measurements. furthermore, we assess the impact of the cross-calibration uncertainties on cosmology.methods: using the hiflugcs sample, consisting of the 64 x-ray brightest galaxy clusters, we constrain the icm temperatures through spectral fitting in the same, mostly isothermal regions and compare the different instruments. we use the stacked residual ratio method to evaluate the cross-calibration uncertainties between the instruments as a function of energy. our work is an extension to a previous one using x-ray clusters by the international astronomical consortium for high energy calibration (iachec) and is carried out in the context of iachec.results: performing spectral fitting in the full energy band, (0.7-7) kev, as is typical of the analysis of cluster spectra, we find that best-fit temperatures determined with xmm-newton/epic are significantly lower than chandra/acis temperatures. this confirms the previous iachec results obtained with older calibrations with high precision. the difference increases with temperature, and we quantify this dependence with a fitting formula. for instance, at a cluster temperature of 10 kev, epic temperatures are on average 23% lower than acis temperatures. we also find systematic differences between the three xmm-newton/epic instruments, with the pn detector typically estimating the lowest temperatures. testing the cross-calibration of the energy-dependence of the effective areas in the soft and hard energy bands, (0.7-2) kev and (2-7) kev, respectively, we confirm the previously indicated relatively good agreement between all instruments in the hard and the systematic differences in the soft band. we provide scaling relations to convert between the different instruments based on the effective area, gas temperature, and hydrostatic mass. we demonstrate that effects like multitemperature structure and different relative sensitivities of the instruments at certain energy bands cannot explain the observed differences. we conclude that using xmm-newton/epic instead of chandra/acis to derive full energy band temperature profiles for cluster mass determination results in an 8% shift toward lower ωm values and <1% change of σ8 values in a cosmological analysis of a complete sample of galaxy clusters. such a shift alone is insufficient to significantly alleviate the tension between planck cmb primary anisotropies and sunyaev-zel'dovich-plus-xmm-newton cosmological constraints. appendices are available in electronic form at http://www.aanda.org | xmm-newton and chandra cross-calibration using hiflugcs galaxy clusters . systematic temperature differences and cosmological impact |
the detectability of light dark matter in direct detection experiments is limited by the small kinetic energy of the recoiling targets. thus, scenarios where dark matter is boosted to relativistic velocities provide a useful tactic to constrain sub-gev dark matter particles. of the possible dark matter boosting mechanisms, cosmic-ray upscattering is an appealing paradigm as it doesn't require any additional assumptions beyond dark matter coupling to nucleons or electrons. however, detectable signals are obtained only with relatively large cross sections which, in turn, can only be realized with large couplings, light mediators or composite dark matter. in this work we consider a general set of light mediators that couple dark matter to hadrons. using data from borexino, xenon1t, lz and super-k, we show that existing constraints on such mediators preclude appreciable cosmic-ray dark matter upscattering. this finding highlights the limited applicability of cosmic-ray upscattering constraints and suggests they only be used in model-dependent studies. | cosmic-ray dark matter confronted by constraints on new light mediators |
radiative energy losses are very important in regulating the cosmic ray electron and/or positron (cre) spectrum during their propagation in the milky way. particularly, the klein-nishina (kn) effect of the inverse compton scattering (ics) results in less efficient energy losses of high-energy electrons, which is expected to leave imprints on the propagated electron spectrum. it has been proposed that the hardening of cre spectra around 50 gev observed by fermi-lat, ams-02, and dampe could be due to the kn effect. we show in this work that the transition from the thomson regime to the kn regime of the ics is actually quite smooth compared with the approximate treatment adopted in some previous works. as a result, the observed spectral hardening of cres cannot be explained by the kn effect. it means that an additional hardening of the primary electrons spectrum is needed. we also provide a parameterized form for the accurate calculation of the ics energy-loss rate in a wide energy range. supported by the national key research and development program of china (grant no. 2016yfa0400203 and 2016yfa0400204), the national natural science foundation of china (grant nos. 11722328, u1738205, u1738203, 11851303 and 11851305), and the program for innovative talents and entrepreneur in jiangsu. | klein-nishina effect and the cosmic ray electron spectrum |
as the fundamental physical process with many astrophysical implications, the diffusion of cosmic rays (crs) is determined by their interaction with magnetohydrodynamic (mhd) turbulence. we consider the magnetic mirroring effect arising from mhd turbulence on the diffusion of crs. due to the intrinsic superdiffusion of turbulent magnetic fields, crs with large pitch angles that undergo mirror reflection, i.e., bouncing crs, are not trapped between magnetic mirrors, but move diffusively along the turbulent magnetic field, leading to a new type of parallel diffusion, i.e., mirror diffusion. this mirror diffusion is in general slower than the diffusion of nonbouncing crs with small pitch angles that undergo gyroresonant scattering. the critical pitch angle at the balance between magnetic mirroring and pitch-angle scattering is important for determining the diffusion coefficients of both bouncing and nonbouncing crs and their scalings with the cr energy. we find nonuniversal energy scalings of diffusion coefficients, depending on the properties of mhd turbulence. | diffusion of cosmic rays in mhd turbulence with magnetic mirrors |
cosmic rays (crs) with ~gev energies can contribute significantly to the energy and pressure budget in the interstellar, circumgalactic, and intergalactic medium (ism, cgm, igm). recent cosmological simulations have begun to explore these effects, but almost all studies have been restricted to simplified models with constant cr diffusivity and/or streaming speeds. physical models of cr propagation/scattering via extrinsic turbulence and self-excited waves predict transport coefficients which are complicated functions of local plasma properties. in a companion paper, we consider a wide range of observational constraints to identify proposed physically motivated cosmic ray propagation scalings which satisfy both detailed milky way (mw) and extragalactic γ-ray constraints. here, we compare the effects of these models relative to simpler 'diffusion+streaming' models on galaxy and cgm properties at dwarf through mw mass scales. the physical models predict large local variations in cr diffusivity, with median diffusivity increasing with galactocentric radii and decreasing with galaxy mass and redshift. these effects lead to a more rapid dropoff of cr energy density in the cgm (compared to simpler models), in turn producing weaker effects of crs on galaxy star formation rates (sfrs), cgm absorption profiles, and galactic outflows. the predictions of the more physical cr models tend to lie 'in between' models which ignore crs entirely and models which treat crs with constant diffusivity. | effects of different cosmic ray transport models on galaxy formation |
galaxy clusters are expected to be dark matter (dm) reservoirs and storage rooms for the cosmic-ray protons (crp) that accumulate along the cluster's formation history. accordingly, they are excellent targets to search for signals of dm annihilation and decay at gamma-ray energies and are predicted to be sources of large-scale gamma-ray emission due to hadronic interactions in the intracluster medium. we estimate the sensitivity of the cherenkov telescope array (cta) to detect diffuse gamma-ray emission from the perseus galaxy cluster. we perform a detailed spatial and spectral modelling of the expected signal for the dm and the crp components. for each, we compute the expected cta sensitivity. the observing strategy of perseus is also discussed. in the absence of a diffuse signal (non-detection), cta should constrain the crp to thermal energy ratio within the radius $r_{500}$ down to about $x_{500}<3\times 10^{-3}$, for a spatial crp distribution that follows the thermal gas and a crp spectral index $\alpha_{\rm crp}=2.3$. under the optimistic assumption of a pure hadronic origin of the perseus radio mini-halo and depending on the assumed magnetic field profile, cta should measure $\alpha_{\rm crp}$ down to about $\delta\alpha_{\rm crp}\simeq 0.1$ and the crp spatial distribution with 10% precision. regarding dm, cta should improve the current ground-based gamma-ray dm limits from clusters observations on the velocity-averaged annihilation cross-section by a factor of up to $\sim 5$, depending on the modelling of dm halo substructure. in the case of decay of dm particles, cta will explore a new region of the parameter space, reaching models with $\tau_{\chi}>10^{27}$s for dm masses above 1 tev. these constraints will provide unprecedented sensitivity to the physics of both crp acceleration and transport at cluster scale and to tev dm particle models, especially in the decay scenario. | prospects for $\\gamma$-ray observations of the perseus galaxy cluster with the cherenkov telescope array |
in the third-generation (3g) gravitational-wave (gw) detector era, the multi-messenger gw observation for binary neutron star (bns) merger events can exert great impacts on exploring the cosmic expansion history. in this work, we comprehensively explore the potential of 3g gw standard siren observations in cosmological parameter estimations by considering the 3g gw detectors and the future short $\gamma$-ray burst (grb) detector theseus-like telescope joint observations. based on the 10-year observation of different detection strategies, we predict that the numbers of detectable gw-grb events are 277-685 with the redshifts $z<4$ and the inclination angles $\iota<17^{\circ}$. for the cosmological analysis, we consider five typical dark energy models, i.e., the $\lambda$cdm, $w$cdm, $w_0w_a$cdm models, and interacting dark energy (ide) models (i$\lambda$cdm and i$w$cdm). we find that gw can tightly constrain the hubble constant with precisions of $0.09\%$-$0.37\%$, but perform not well in constraining other cosmological parameters. fortunately, gw could effectively break the cosmological parameter degeneracies generated by the mainstream em observations, cmb+bao+sn (cbs). when combining the mock gw data with the cbs data, cbs+gw can tightly constrain the equation of state parameter of dark energy $w$ with a precision of $1.36\%$, close to the standard of precision cosmology. meanwhile, the addition of gw to cbs could improve constraints on cosmological parameters by $35.3\%$-$92.0\%$. in conclusion, gw standard siren observations from 3g gw detectors could play a crucial role in helping solve the hubble tension and probe the fundamental nature of dark energy. | a comprehensive forecast for cosmological parameter estimation using joint observations of gravitational-wave standard sirens and short $\\gamma$-ray bursts |
we reexamine unitarity bounds on the annihilation cross section of thermal weakly interacting massive particle (wimp) dark matter. for high-mass pointlike dark matter, it is generic to form wimp bound states, which, together with sommerfeld enhancement, affects the relic abundance. we show that these effects lower the unitarity bound from 139 tev to below 100 tev for non-self-conjugate dark matter and from 195 tev (the oft-quoted value of 340 tev assumes ωdmh2=1 ) to 140 tev for the self-conjugate case. for composite dark matter, for which the unitarity limit on the radius was thought to be mass independent, we show that the largest allowed mass is 1 pev. in addition, we find important new effects for annihilation in the late universe. for example, while the production of high-energy light fermions in wimp annihilation is suppressed by helicity, we show that bound-state formation changes this. coupled with rapidly improving experimental sensitivity to tev-range gamma rays, cosmic rays, and neutrinos, our results give new hope to attack the thermal-wimp mass range from the high-mass end. | tev-scale thermal wimps: unitarity and its consequences |
we present the results of the most complete scan of the parameter space for cosmic ray (cr) injection and propagation. we perform a bayesian search of the main galprop parameters, using the multinest nested sampling algorithm, augmented by the bambi neural network machine-learning package. this is the first study to separate out low-mass isotopes (p, \bar{p}, and he) from the usual light elements (be, b, c, n, and o). we find that the propagation parameters that best-fit p,\bar{p}, and he data are significantly different from those that fit light elements, including the b/c and 10be/9be secondary-to-primary ratios normally used to calibrate propagation parameters. this suggests that each set of species is probing a very different interstellar medium, and that the standard approach of calibrating propagation parameters using b/c can lead to incorrect results. we present posterior distributions and best-fit parameters for propagation of both sets of nuclei, as well as for the injection abundances of elements from h to si. the input galdef files with these new parameters will be included in an upcoming public galprop update. | bayesian analysis of cosmic ray propagation: evidence against homogeneous diffusion |
long-wavelength spectral distortions in the cosmic microwave background arising from the 21 cm transition in neutral hydrogen are a key probe of the cosmic dawn and the epoch of reionization. these features may reveal the nature of the first stars and ultra-faint galaxies that transformed the spin temperature and ionization state of the primordial gas. saras 2 is a spectral radiometer purposely designed for the precision measurement of these monopole or all-sky global 21 cm spectral distortions. we use 63 hr nighttime observations of the radio background in the frequency band 110-200 mhz, with the radiometer deployed at the timbaktu collective in southern india, to derive likelihoods for plausible redshifted 21 cm signals predicted by theoretical models. first light with saras 2 disfavors the class of models that feature weak x-ray heating (with {f}x≤slant 0.1) and rapid reionization (with peak \tfrac{{{dt}}b}{{dz}}≥slant 120 mk per unit redshift interval). | first results on the epoch of reionization from first light with saras 2 |
the discoveries of a number of binary black hole mergers by ligo and virgo have reinvigorated the interest that primordial black holes (pbhs) of tens of solar masses could contribute non-negligibly to the dark matter energy density. should even a small population of pbhs with masses ≳o (m⊙) exist, they could profoundly impact the properties of the intergalactic medium and provide insight into novel processes at work in the early universe. we demonstrate here that observations of the 21-cm transition in neutral hydrogen during the epochs of reionization and cosmic dawn will likely provide one of the most stringent tests of solar mass pbhs. in the context of 21-cm cosmology, pbhs give rise to three distinct observable effects: (i) the modification to the primordial power spectrum (and thus also the halo mass function) induced by poisson noise, (ii) a uniform heating and ionization of the intergalactic medium via x-rays produced during accretion, and (iii) a local modification to the temperature and density of the ambient medium surrounding isolated pbhs. using a four-parameter astrophysical model, we show that experiments like ska and hera could potentially improve upon existing constraints derived using observations of the cosmic microwave background by more than 1 order of magnitude. | constraining the primordial black hole abundance with 21-cm cosmology |
$\mathrm{co}$ is the most widely used observational tracer of molecular gas. the observable $\mathrm{co}$ luminosity is translated to ${{\rm{h}}}_{2}$ mass via a conversion factor, ${x}_{\mathrm{co}}$ , which is a source of uncertainty and bias. despite variations in ${x}_{\mathrm{co}}$ , the empirically determined solar neighborhood value is often applied across different galactic environments. to improve understanding of ${x}_{\mathrm{co}}$ , we employ 3d magnetohydrodynamics simulations of the interstellar medium (ism) in galactic disks with a large range of gas surface densities, allowing for varying metallicity, far-ultraviolet (fuv) radiation, and cosmic-ray ionization rate (crir). with the tigress simulation framework we model the three-phase ism with self-consistent star formation and feedback, and post-process outputs with chemistry and radiation transfer to generate synthetic co (1-0) and (2-1) maps. our models reproduce the observed co excitation temperatures, line widths, and line ratios in nearby disk galaxies. ${x}_{\mathrm{co}}$ decreases with increasing metallicity, with a power-law slope of -0.8 for the (1-0) line and -0.5 for the (2-1) line. ${x}_{\mathrm{co}}$ also decreases at higher crir and is insensitive to the fuv radiation. as density increases, ${x}_{\mathrm{co}}$ first decreases owing to increasing excitation temperature and then increases when the emission is fully saturated. we provide fits between ${x}_{\mathrm{co}}$ and observable quantities such as the line ratio, peak antenna temperature, and line brightness, which probe local gas conditions. these fits, which allow for varying beam size, may be used in observations to calibrate out systematic biases. we also provide estimates of the co-dark ${{\rm{h}}}_{2}$ fraction at different gas surface densities, observational sensitivities, and beam sizes. | the environmental dependence of the xco conversion factor |
gamma-ray bursts (grbs) are short-lived, luminous explosions at cosmological distances, thought to originate from relativistic jets launched at the deaths of massive stars. they are among the prime candidates to produce the observed cosmic rays at the highest energies. recent neutrino data have, however, started to constrain this possibility in the simplest models with only one emission zone. in the classical theory of grbs, it is expected that particles are accelerated at mildly relativistic shocks generated by the collisions of material ejected from a central engine. here we consider neutrino and cosmic-ray emission from multiple emission regions since these internal collisions must occur at very different radii, from below the photosphere all the way out to the circumburst medium, as a consequence of the efficient dissipation of kinetic energy. we demonstrate that the different messengers originate from different collision radii, which means that multi-messenger observations open windows for revealing the evolving grb outflows. | neutrino and cosmic-ray emission from multiple internal shocks in gamma-ray bursts |
we report the observation of new properties of primary cosmic rays, neon (ne), magnesium (mg), and silicon (si), measured in the rigidity range 2.15 gv to 3.0 tv with 1.8 ×106 ne , 2.2 ×106 mg , and 1.6 ×106 si nuclei collected by the alpha magnetic spectrometer experiment on the international space station. the ne and mg spectra have identical rigidity dependence above 3.65 gv. the three spectra have identical rigidity dependence above 86.5 gv, deviate from a single power law above 200 gv, and harden in an identical way. unexpectedly, above 86.5 gv the rigidity dependence of primary cosmic rays ne, mg, and si spectra is different from the rigidity dependence of primary cosmic rays he, c, and o. this shows that the ne, mg, and si and he, c, and o are two different classes of primary cosmic rays. | properties of neon, magnesium, and silicon primary cosmic rays results from the alpha magnetic spectrometer |
geological surface-exposure dating using cosmogenic-nuclide accumulation became a practical geochronological endeavor in 1986, when the utility of 10be, 26al, 36cl, and 3he were all demonstrated. in response to the lack of a common basis for quantifying analytical consistency and calibrating cosmogenic-nuclide production, the cronus-earth project in the u.s. was started in 2005, along with a european partner project, cronus-eu. the goal of the cronus-earth project was to improve the accuracy and precision of terrestrial cosmogenic nuclide dating in general, focusing especially on nuclide production rates and their variation with altitude, latitude, and time, and to attempt to move from empirically based methods to ones with a stronger basis in physics. the cronus-earth project conducted extensive intercomparisons of reference materials to attempt to quantify analytical reproducibility at the community level. we found that stated analytical uncertainties nearly always underestimate the actual degree of variability, as quantified by the over-all coefficient of variation of the intercalibration data. the average amount by which the actual coefficient of variation exceeded the analytical uncertainty was a factor of two (100%), but ranged from 15% to 300% depending on the nuclide and material. coefficients of variation ranged from 3-4% for 10be to 6-8% for 36cl, 14c, and 21ne, to 5-11% for 26al. both interlaboratory bias and within-laboratory excess spread of the data played a role in increasing variability above the stated analytical uncertainties. the physical basis for cosmogenic nuclide production was investigated through numerical modeling and the measurement of energy-dependent neutron cross sections for nuclide interactions. we formulated new, physically based, scaling models, denoted lsd and lsdn, by generalizing global numerical simulations of cosmic-ray processes. the cronus-earth project identified new geological calibration sites, including one at low latitude and high elevation (huancané, peru), and replicated nuclide measurement at numerous laboratories. at many sites multiple nuclides were measured, providing much more confidence in the equivalence of surface-exposure ages calculated from differing nuclides. the data were interpreted using an original cosmogenic-nuclide calculator, cronuscalc, that incorporates the new physically based scaling. the new data and model produced significantly better fits than previous efforts, but do not fully resolve apparent spatial variations in production rates. the cronus-earth and cronus-eu projects have provided a firm foundation for assessing the strengths and weaknesses of cosmogenic-nuclide analytical methods, adjusted the ams standards for 10be and consequently revised the half-life, and have provided improved calibration data sets and interpretative tools. | the cronus-earth project: a synthesis |
cosmic rays (crs) have recently re-emerged as attractive candidates for mediating feedback in galaxies because of their long cooling time-scales. simulations have shown that the momentum and energy deposited by crs moving with respect to the ambient medium can drive galactic winds. however, simulations are hampered by our ignorance of the details of cr transport. two key limits previously considered model cr transport as a purely diffusive process (with constant diffusion coefficient) and as an advective streaming process. with a series of gadget simulations, we compare the results of these different assumptions. in idealized three-dimensional galaxy formation models, we show that these two cases result in significant differences for the galactic wind mass-loss rates and star formation suppression in dwarf galaxies with halo masses m ≈ 1010 m⊙: diffusive cr transport results in more than 10 times larger mass-loss rates compared to cr streaming models. we demonstrate that this is largely due to the excitation of alfvén waves during the cr streaming process that drains energy from the cr population to the thermal gas, which is subsequently radiated away. by contrast, cr diffusion conserves the cr energy in the absence of adiabatic changes and if crs are efficiently scattered by alfvén waves that are propagating up the cr gradient. moreover, because pressure gradients are preserved by cr streaming, but not diffusion, the two can have a significantly different dynamical evolution regardless of this energy exchange. in particular, the constant diffusion coefficients usually assumed can lead to unphysically high cr fluxes. | cosmic ray-driven galactic winds: streaming or diffusion? |
previous measurements of the composition of ultra-high energy cosmic rays (uhecrs) made by the high resolution fly's eye (hires) and pierre auger observatory (pao) are seemingly contradictory, but utilize different detection methods, as hires was a stereo detector and pao is a hybrid detector. the five year telescope array (ta) middle drum hybrid composition measurement is similar in some, but not all, respects in methodology to pao, and good agreement is evident between data and a light, largely protonic, composition when comparing the measurements to predictions obtained with the qgsjetii-03 and qgsjet-01c models. these models are also in agreement with previous hires stereo measurements, confirming the equivalence of the stereo and hybrid methods. the data is incompatible with a pure iron composition, for all models examined, over the available range of energies. the elongation rate and mean values of xmax are in good agreement with pierre auger observatory data. this analysis is presented using two methods: data cuts using simple geometrical variables and a new pattern recognition technique. | study of ultra-high energy cosmic ray composition using telescope array's middle drum detector and surface array in hybrid mode |
soon after the discovery of the kerr metric, penrose realized that superradiance can be exploited to extract energy from black holes. the original idea (involving the breakup of a single particle) yields only modest energy gains. a variant of the penrose process consists of particle collisions in the ergoregion. the collisional penrose process has been explored recently in the context of dark matter searches, with the conclusion that the ratio η between the energy of postcollision particles detected at infinity and the energy of the colliding particles should be modest (η ≲1.5 ). schnittman [phys. rev. lett. 113, 261102 (2014)] has shown that these studies underestimated the maximum efficiency by about 1 order of magnitude (i.e., η ≲15 ). in this work we show that particle collisions in the vicinity of rapidly rotating black holes can produce high-energy ejecta and result in high efficiencies under much more generic conditions. the astrophysical likelihood of these events deserves further scrutiny, but our study hints at the tantalizing possibility that the collisional penrose process may power gamma rays and ultrahigh-energy cosmic rays. | ultrahigh-energy debris from the collisional penrose process |
we study the implications of ultrahigh-energy cosmic-ray (uhecr) data from the pierre auger observatory for potential accelerator candidates and cosmogenic neutrino fluxes for different combinations of nuclear disintegration and air-shower models. we exploit the most recent spectral and mass composition data (2017) with a new, computationally efficient simulation code, prince. we extend a systematic framework, which has been previously applied in a combined fit by the pierre auger collaboration, with the cosmological source evolution as an additional free parameter. in this framework, an ensemble of generalized uhecr accelerators is characterized by a universal spectral index (equal for all injection species), a maximal rigidity, and the normalizations for five nuclear element groups. we find that the 2017 data favor a small but constrained contribution of heavy elements (iron) at the source. we demonstrate that the results moderately depend on the nuclear disintegration (puget-stecker-bredekamp, peanut, or talys) model and more strongly on the air-shower (epos-lhc, sibyll 2.3, or qgsjetii-04) model. variations of these models result in different source evolution and spectral indices, limiting the interpretation in terms of a particular class of cosmic accelerators. better-constrained parameters include the maximal rigidity and the mass composition at the source. hence, the cosmogenic neutrino flux can be robustly predicted. depending on the source evolution at high redshifts, the flux is likely out of reach of future neutrino observatories in most cases, and a minimal cosmogenic neutrino flux cannot be claimed from data without assuming a cosmological distribution of the sources. | a new view on auger data and cosmogenic neutrinos in light of different nuclear disintegration and air-shower models |
tidal disruption events (tde) have been considered as cosmic-ray and neutrino sources for a decade. we suggest two classes of new scenarios for high-energy multi-messenger emission from tdes that do not have to harbor powerful jets. first, we investigate high-energy neutrino and gamma-ray production in the core region of a supermassive black hole. in particular, we show that ∼1-100 tev neutrinos and mev gamma rays can efficiently be produced in hot coronae around an accretion disk. we also study the consequences of particle acceleration in radiatively inefficient accretion flows (riafs). second, we consider possible cosmic-ray acceleration by sub-relativistic disk-driven winds or interactions between tidal streams, and show that subsequent hadronuclear and photohadronic interactions inside the tde debris lead to gev-pev neutrinos and sub-gev cascade gamma rays. we demonstrate that these models should be accompanied by soft gamma rays or hard x-rays as well as optical/uv emission, which can be used for future observational tests. although this work aims to present models of non-jetted high-energy emission, we discuss the implications of the tde at2019dsg that might coincide with the high-energy neutrino icecube-191001a, by considering the corona, riaf, hidden sub-relativistic wind, and hidden jet models. it is not yet possible to be conclusive about their physical association and the expected number of neutrinos is typically much less than unity. we find that the most optimistic cases of the corona and hidden wind models could be consistent with the observation of icecube-191001a, whereas jet models are unlikely to explain the multi-messenger observations. | high-energy neutrino and gamma-ray emission from tidal disruption events |
the landscape of high- and ultra-high-energy astrophysics has changed in the last decade, largely due to the inflow of data collected by large-scale cosmic-ray, gamma-ray, and neutrino observatories. at the dawn of the multimessenger era, the interpretation of these observations within a consistent framework is important to elucidate the open questions in this field. crpropa 3.2 is a monte carlo code for simulating the propagation of high-energy particles in the universe. this version represents a major leap forward, significantly expanding the simulation framework and opening up the possibility for many more astrophysical applications. this includes, among others: efficient simulation of high-energy particles in diffusion-dominated domains, self-consistent and fast modelling of electromagnetic cascades with an extended set of channels for photon production, and studies of cosmic-ray diffusion tensors based on updated coherent and turbulent magnetic-field models. furthermore, several technical updates and improvements are introduced with the new version, such as: enhanced interpolation, targeted emission of sources, and a new propagation algorithm (boris push). the detailed description of all novel features is accompanied by a discussion and a selected number of example applications. | crpropa 3.2 - an advanced framework for high-energy particle propagation in extragalactic and galactic spaces |
the icecube neutrino observatory at the south pole has measured the diffuse astrophysical neutrino flux up to ~pev energies and is starting to identify first point source candidates. the next generation facility, icecube-gen2, aims at extending the accessible energy range to eev in order to measure the continuation of the astrophysical spectrum, to identify neutrino sources, and to search for a cosmogenic neutrino flux. as part of icecube-gen2, a radio array is foreseen that is sensitive to detect askaryan emission of neutrinos beyond ~30 pev. surface and deep antenna stations have different benefits in terms of effective area, resolution, and the capability to reject backgrounds from cosmic-ray air showers and may be combined to reach the best sensitivity. the optimal detector configuration is still to be identified. this contribution presents the full-array simulation efforts for a combination of deep and surface antennas, and compares different design options with respect to their sensitivity to fulfill the science goals of icecube-gen2. | sensitivity studies for the icecube-gen2 radio array |
the sharp change in slope of the ultrahigh energy cosmic ray (uhecr) spectrum around 1 018.6 ev (the ankle), combined with evidence of a light but extragalactic component near and below the ankle and intermediate composition above, has proved exceedingly challenging to understand theoretically, without fine-tuning. we propose a mechanism whereby photo-disintegration of ultrahigh energy nuclei in the region surrounding a uhecr accelerator accounts for the observed spectrum and inferred composition at earth. for suitable source conditions, the model reproduces the spectrum and the composition over the entire extragalactic cosmic ray energy range, i.e. above 1 017.5 ev . predictions for the spectrum and flavors of neutrinos resulting from this process are also presented. | origin of the ankle in the ultrahigh energy cosmic ray spectrum, and of the extragalactic protons below it |
we investigate the cosmic evolution of the ratio between black hole (bh) mass (mbh) and host galaxy total stellar mass (mstellar) out to z ∼ 2.5 for a sample of 100 x-ray-selected moderate-luminosity, broad-line active galactic nuclei (agns) in the chandra-cosmos legacy survey. by taking advantage of the deep multiwavelength photometry and spectroscopy in the cosmos field, we measure in a uniform way the galaxy total stellar mass using an spectral energy distribution decomposition technique and the bh mass based on broad emission line measurements and single-epoch virial estimates. our sample of agn host galaxies has total stellar masses of 1010-12m⊙, and bh masses of 107.0-9.5m⊙. combining our sample with the relatively bright agn samples from the literature, we find no significant evolution of the mbh-mstellar relation with the bh-to-host total stellar mass ratio of mbh/mstellar ∼ 0.3% at all redshifts probed. we conclude that the average bh-to-host stellar mass ratio appears to be consistent with the local value within the uncertainties, suggesting a lack of evolution of the mbh-mstellar relation up to z ∼ 2.5. | no significant evolution of relations between black hole mass and galaxy total stellar mass up to z ∼ 2.5 |
we present constraints derived from a search of four years of icecube data for a prompt neutrino flux from gamma-ray bursts (grbs). a single low-significance neutrino, compatible with the atmospheric neutrino background, was found in coincidence with one of the 506 observed bursts. although grbs have been proposed as candidate sources for ultra-high-energy cosmic rays, our limits on the neutrino flux disfavor much of the parameter space for the latest models. we also find that no more than ∼1% of the recently observed astrophysical neutrino flux consists of prompt emission from grbs that are potentially observable by existing satellites. | search for prompt neutrino emission from gamma-ray bursts with icecube |
the heliopause is a boundary that separates the heliosheath (which contains magnetic fields and plasmas that originate in the sun) from the interstellar medium (which contains magnetic fields and particles of stellar/interstellar origin). observations of the heliopause were first made by the particles and fields instruments on the voyager 1 spacecraft, moving radially in the northern hemisphere, which crossed the heliopause on 25 august 2012 at a distance of 121.6 au. we show using observations of the magnetic field and energetic particles that voyager 2 crossed the heliopause in the southern hemisphere on 5 november 2018 at a distance of ≈119.0 au. voyager 2 observed a much thinner and simpler heliopause than voyager 1 as well as stronger interstellar magnetic fields, and it discovered a `magnetic barrier' in the heliosheath adjacent to the heliopause that strongly influences the entry of cosmic rays into the heliosphere. the magnetic field direction observed by voyager 2 changed smoothly from the time of arrival at the magnetic barrier, through it, and onwards into the interstellar medium, with a small (a few degrees) or no change across the heliopause. these observations, together with the voyager 1 observations and existing models, show that the magnetic barrier, the heliopause and the neighbouring very local interstellar medium form a complex interconnected dynamical system. | magnetic field and particle measurements made by voyager 2 at and near the heliopause |
cosmic-ray transport in astrophysical environments is often dominated by the diffusion of particles in a magnetic field composed of both a turbulent and a mean component. this process, which is two-fold turbulent mixing in that the particle motion is stochastic with respect to the field lines, needs to be understood in order to properly model cosmic-ray signatures. one of the most important aspects in the modeling of cosmic-ray diffusion is that fully resonant scattering, the most effective such process, is only possible if the wave spectrum covers the entire range of propagation angles. by taking the wave spectrum boundaries into account, we quantify cosmic-ray diffusion parallel and perpendicular to the guide field direction at turbulence levels above 5% of the total magnetic field. we apply our results of the parallel and perpendicular diffusion coefficient to the milky way. we show that simple purely diffusive transport is in conflict with observations of the inner galaxy, but that just by taking a galactic wind into account, data can be matched in the central 5 kpc zone. further comparison shows that the outer galaxy at $>5\,$kpc, on the other hand, should be dominated by perpendicular diffusion, likely changing to parallel diffusion at the outermost radii of the milky way. | regimes of cosmic-ray diffusion in galactic turbulence |
ongoing and future radio surveys aim to trace the evolution of black hole growth and feedback from active galactic nuclei (agns) throughout cosmic time; however, there remain major uncertainties in translating radio luminosity functions into a reliable assessment of the energy input as a function of galaxy and/or dark matter halo mass. a crucial and long-standing problem is the composition of the radio-lobe plasma that traces agn jet activity. in this paper, we carry out a systematic comparison of the plasma conditions in fanaroff & riley class i and ii radio galaxies to demonstrate conclusively that their internal composition is systematically different. this difference is best explained by the presence of an energetically dominant proton population in the fri, but not the frii radio galaxies. we show that, as expected from this systematic difference in particle content, radio morphology also affects the jet-power/radio-luminosity relationship, with frii radio galaxies having a significantly lower ratio of jet power to radio luminosity than the fri cluster radio sources used to derive jet-power scaling relations via x-ray cavity measurements. finally, we also demonstrate conclusively that lobe composition is unconnected to accretion mode (optical excitation class): the internal conditions of low- and high-excitation frii radio lobes are indistinguishable. we conclude that inferences of population-wide agn impact require careful assessment of the contribution of different jet subclasses, particularly given the increased diversity of jet evolutionary states expected to be present in deep, low-frequency radio surveys such as the lofar two-metre sky survey. | particle content, radio-galaxy morphology, and jet power: all radio-loud agn are not equal |
the event generator sibyll can be used for the simulation of hadronic multiparticle production up to the highest cosmic ray energies. it is optimized for providing an economic description of those aspects of the expected hadronic final states that are needed for the calculation of air showers and atmospheric lepton fluxes. new measurements from fixed target and collider experiments, in particular those at lhc, allow us to test the predictive power of the model version 2.1, which was released more than 10 years ago, and also to identify shortcomings. based on a detailed comparison of the model predictions with the new data we revisit model assumptions and approximations to obtain an improved version of the interaction model. in addition a phenomenological model for the production of charm particles is implemented as needed for the calculation of prompt lepton fluxes in the energy range of the astrophysical neutrinos recently discovered by icecube. after giving an overview of the new ideas implemented in sibyll and discussing how they lead to an improved description of accelerator data, predictions for air showers and atmospheric lepton fluxes are presented. | a new version of the event generator sibyll |
in this chapter, we review some features of particle acceleration in astrophysical jets. we begin by describing four observational results relating to the topic, with particular emphasis on jets in active galactic nuclei and parallels between different sources. we then discuss the ways in which particles can be accelerated to high energies in magnetised plasmas, focusing mainly on shock acceleration, second-order fermi and magnetic reconnection; in the process, we attempt to shed some light on the basic conditions that must be met by any mechanism for the various observational constraints to be satisfied. we describe the limiting factors for the maximum particle energy and briefly discuss multimessenger signals from neutrinos and ultrahigh energy cosmic rays, before describing the journey of jet plasma from jet launch to cocoon with reference to the different acceleration mechanisms. we conclude with some general comments on the future outlook. | particle acceleration in astrophysical jets |
cosmic ray (cr) feedback has been identified as a critical process in galaxy formation. most previous simulations have integrated out the energy dependence of the cr distribution, despite its large extent over more than 12 decades in particle energy. to improve upon this simplification, we present the implementation and first application of spectrally resolved crs, which are coupled to the magnetohydrodynamics in simulations of galaxy formation. the spectral model for the crs enables more accurate cr cooling and allows for an energy-dependent spatial diffusion, for which we introduce a new stable numerical algorithm that proves to be essential in highly dynamical systems. we perform galaxy formation simulations with this new model and compare the results to a grey cr approach with a simplified diffusive transport and effective cooling that assumes steady-state spectra. we find that the galaxies with spectrally resolved crs differ in morphology, star formation rate, and strength and structure of the outflows. the first outflow front is driven by crs with average momenta of $\sim 200-600\, \mathrm{gev}~c^{-1}$. the subsequent formation of outflows, which reach mass loading factors of order unity, are primarily launched by crs of progressively smaller average momenta of $\sim 8-15\, \mathrm{gev}~c^{-1}$. the cr spectra in the galactic centre quickly approach a steady state, with small temporal variations. in the outer disc and outflow regions, the spectral shape approaches steady state only after $\sim 2\, \mathrm{gyr}$ of evolution. furthermore, the shapes of the approximate steady-state spectra differ for individual regions of the galaxy, which highlights the importance of actively including the full cr spectrum. | spectrally resolved cosmic rays - ii. momentum-dependent cosmic ray diffusion drives powerful galactic winds |
transatlantic exploration took place centuries before the crossing of columbus. physical evidence for early european presence in the americas can be found in newfoundland, canada1,2. however, it has thus far not been possible to determine when this activity took place3-5. here we provide evidence that the vikings were present in newfoundland in ad 1021. we overcome the imprecision of previous age estimates by making use of the cosmic-ray-induced upsurge in atmospheric radiocarbon concentrations in ad 993 (ref. 6). our new date lays down a marker for european cognisance of the americas, and represents the first known point at which humans encircled the globe. it also provides a definitive tie point for future research into the initial consequences of transatlantic activity, such as the transference of knowledge, and the potential exchange of genetic information, biota and pathologies7,8. | evidence for european presence in the americas in ad 1021 |
context. the existence of magnetic fields in the circumgalactic medium (cgm) is largely unconstrained. their detection is important as magnetic fields can have a significant impact on the evolution of the cgm, and, in turn, the fields can serve as tracers for dynamical processes in the cgm.aims: using the faraday rotation of polarised background sources, we aim to detect a possible excess of the rotation measure in the surrounding area of nearby galaxies.methods: we used 2461 residual rotation measures (rrms) observed with the low frequency array (lofar), where the foreground contribution from the milky way is subtracted. the rrms were then studied around a subset of 183 nearby galaxies that was selected by apparent b-band magnitude.results: we find that, in general, the rrms show no significant excess for small impact parameters (i.e., the perpendicular distance to the line of sight). however, if we only consider galaxies at higher inclination angles and sightlines that pass close to the minor axis of the galaxies, we find significant excess at impact parameters of less than 100 kpc. the excess in |rrm| is 3.7 rad m−2 with an uncertainty between ±0.9 rad m−2 and ±1.3 rad m−2 depending on the statistical properties of the background (2.8σ-4.1σ). with electron densities of ∼10−4 cm−3, this suggests magnetic field strengths of a few tenths of a microgauss.conclusions: our results suggest a slow decrease in the magnetic field strength with distance from the galactic disc, as expected if the cgm is magnetised by galactic winds and outflows. | detection of magnetic fields in the circumgalactic medium of nearby galaxies using faraday rotation |
we report on four radio-detected cosmic-ray (cr) or cr-like events observed with the antarctic impulsive transient antenna (anita), a nasa-sponsored long-duration balloon payload. two of the four were previously identified as stratospheric cr air showers during the anita-i flight. a third stratospheric cr was detected during the anita-ii flight. here, we report on characteristics of these three unusual cr events, which develop nearly horizontally, 20-30 km above the surface of earth. in addition, we report on a fourth steeply upward-pointing anita-i cr-like radio event which has characteristics consistent with a primary that emerged from the surface of the ice. this suggests a possible τ -lepton decay as the origin of this event, but such an interpretation would require significant suppression of the standard model τ -neutrino cross section. | characteristics of four upward-pointing cosmic-ray-like events observed with anita |
the luminosity distance measurement of gw170817 derived from gravitational-wave analysis in abbott et al. (2017a, hereafter a17:h0) is highly correlated with the measured inclination of the ns-ns system. to improve the precision of the distance measurement, we attempt to constrain the inclination by modeling the broadband x-ray-to-radio emission from gw170817, which is dominated by the interaction of the jet with the environment. we update our previous analysis and we consider the radio and x-ray data obtained at t < 40 days since merger. we find that the afterglow emission from gw170817 is consistent with an off-axis relativistic jet with energy ek∼ 1048 -3 × 1050 erg propagating into an environment with density n ∼ 10-2-10-4 cm-3, with preference for wider jets (opening angle θj= 15°). for these jets, our modeling indicates an off-axis angle θ obs ∼ 25°-50°. we combine our constraints on θ obs with the joint distance-inclination constraint from ligo. using the same ∼170 km s-1 peculiar velocity uncertainty assumed in a17:h0 but with an inclination constraint from the afterglow data, we get a value of {h}0=74.0+/- \tfrac{11.5}{7.5} km s-1 mpc-1, which is higher than the value of {h}0=70.0+/- \tfrac{12.0}{8.0} km s-1 mpc-1 found in a17:h0. further, using a more realistic peculiar velocity uncertainty of 250 km s-1 derived from previous work, we find {h}0=75.5+/- \tfrac{11.6}{9.6} km s-1 mpc-1 for h 0 from this system. this is in modestly better agreement with the local distance ladder than the planck cosmic microwave background, though such a significant discrimination will require ∼50 such events. measurements at t > 100 days of the x-ray and radio emission will lead to tighter constraints. | improved constraints on h 0 from a combined analysis of gravitational-wave and electromagnetic emission from gw170817 |
models for cosmic ray (cr) dynamics fundamentally depend on the rate of cr scattering from magnetic fluctuations. in the ism, for crs with energies ~mev-tev, these fluctuations are usually attributed either to 'extrinsic turbulence' (et) - a cascade from larger scales - or 'self-confinement' (sc) - self-generated fluctuations from cr streaming. using simple analytic arguments and detailed 'live' numerical cr transport calculations in galaxy simulations, we show that both of these, in standard form, cannot explain even basic qualitative features of observed cr spectra. for et, any spectrum that obeys critical balance or features realistic anisotropy, or any spectrum that accounts for finite damping below the dissipation scale, predicts qualitatively incorrect spectral shapes and scalings of b/c and other species. even if somehow one ignored both anisotropy and damping, observationally required scattering rates disagree with et predictions by orders of magnitude. for sc, the dependence of driving on cr energy density means that it is nearly impossible to recover observed cr spectral shapes and scalings, and again there is an orders-of-magnitude normalization problem. but more severely, sc solutions with super-alfvénic streaming are unstable. in live simulations, they revert to either arbitrarily rapid cr escape with zero secondary production, or to bottleneck solutions with far-too-strong cr confinement and secondary production. resolving these fundamental issues without discarding basic plasma processes requires invoking different drivers for scattering fluctuations. these must act on a broad range of scales with a power spectrum obeying several specific (but plausible) constraints. | standard self-confinement and extrinsic turbulence models for cosmic ray transport are fundamentally incompatible with observations |
sporadic solar energetic particle (sep) events affect the earth’s atmosphere and environment, in particular leading to depletion of the protective ozone layer in the earth’s atmosphere, and pose potential technological and even life hazards. the greatest sep storm known for the last 11 millennia (the holocene) occurred in 774-775 ad, serving as a likely worst-case scenario being 40-50 times stronger than any directly observed one. here we present a systematic analysis of the impact such an extreme event can have on the earth’s atmosphere. using state-of-the-art cosmic ray cascade and chemistry-climate models, we successfully reproduce the observed variability of cosmogenic isotope 10be, around 775 ad, in four ice cores from greenland and antarctica, thereby validating the models in the assessment of this event. we add to prior conclusions that any nitrate deposition signal from sep events remains too weak to be detected in ice cores by showing that, even for such an extreme solar storm and sub-annual data resolution, the nitrate deposition signal is indistinguishable from the seasonal cycle. we show that such a severe event is able to perturb the polar stratosphere for at least one year, leading to regional changes in the surface temperature during northern hemisphere winters. | atmospheric impacts of the strongest known solar particle storm of 775 ad |
the production and acceleration mechanisms of ultrahigh-energy cosmic rays (uhecrs) of energy >1020 ev, clearly beyond the gzk cutoff limit, remain unclear, which points to the exotic nature of the phenomena. recent observations of extragalactic neutrinos may indicate that the source of uhecrs is an extragalactic supermassive black hole (smbh). we demonstrate that ultraefficient energy extraction from a rotating smbh driven by the magnetic penrose process (mpp) could indeed fit the bill. we envision ionization of neutral particles, such as neutron beta decay, skirting close to the black hole horizon that energizes protons to over 1020 ev for an smbh of mass 109m⊙ and magnetic field 104 g. applied to the galactic center smbh, we have a proton energy of order ≈1015.6 ev that coincides with the knee of the cosmic-ray spectra. we show that large γz factors of high-energy particles along the escaping directions occur only in the presence of an induced charge of the black hole, which is known as the wald charge in the case of a uniform magnetic field. it is remarkable that the process requires neither an extended acceleration zone nor fine-tuning of accreting-matter parameters. further, this leads to certain verifiable constraints on the smbh's mass and magnetic field strength as the source of uhecrs. this clearly makes the ultraefficient regime of the mpp one of the most promising mechanisms for fueling the uhecr powerhouse. | supermassive black holes as possible sources of ultrahigh-energy cosmic rays |
we investigate the capability of the probe of extreme multi-messenger astrophysics (poemma) in performing target-of-opportunity (too) neutrino observations. poemma is a proposed space-based probe-class mission for ultrahigh-energy cosmic ray and very-high-energy neutrino detection using two spacecraft, each equipped with a large schmidt telescope to detect optical and near-ultraviolet signals generated by extensive air showers (eass). poemma will be sensitive to cherenkov radiation from upward-moving eass initiated by tau neutrinos interacting in the earth. poemma will be able to quickly repoint (90° in 500 s) each of the two spacecrafts to the direction of an astrophysical source, which in combination with its orbital speed will provide it with unparalleled capability to follow-up transient alerts. we calculate poemma's transient sensitivity for two observational configurations for the satellites (too-stereo and too-dual for smaller and larger satellite separations, respectively) and investigate the impact of variations arising due to poemma's orbital characteristics on its sensitivity to tau neutrinos in various regions of the sky. we explore separate scenarios for long (∼1 05 -6 s ) and short (∼103 s ) duration events, accounting for intrusion from the sun and the moon in the long-duration scenario. we compare the sensitivity and sky coverage of poemma for too observations with those for existing experiments (e.g., icecube, antares, and the pierre auger observatory) and other proposed future experiments (e.g., grand200k). for long bursts, we find that poemma will provide a factor of ≳7 improvement in average neutrino sensitivity above 300 pev with respect to existing experiments, reaching the level of model predictions for neutrino fluences at these energies and above from several types of long-duration astrophysical transients (e.g., binary neutron star mergers and tidal disruption events). for short bursts, poemma will improve the sensitivity over existing experiments by at least an order of magnitude for eν≳100 pev in the "best-case" scenario. poemma's orbital characteristics and rapid repointing capability will provide it access to the full celestial sky, including regions that will not be accessible to ground-based neutrino experiments. finally, we discuss the prospects for poemma to detect neutrinos from candidate astrophysical neutrino sources in the nearby universe. our results demonstrate that with its improved neutrino sensitivity at ultrahigh energies and unique full-sky coverage, poemma will be an essential, complementary component in a rapidly expanding multimessenger network. | poemma's target-of-opportunity sensitivity to cosmic neutrino transient sources |
we add nonlinear and state-dependent terms to quantum field theory. we show that the resulting low-energy theory, nonlinear quantum mechanics, is causal, preserves probability and permits a consistent description of the process of measurement. we explore the consequences of such terms and show that nonlinear quantum effects can be observed in macroscopic systems even in the presence of decoherence. we find that current experimental bounds on these nonlinearities are weak and propose several experimental methods to significantly probe these effects. the locally exploitable effects of these nonlinearities have enormous technological implications. for example, they would allow large-scale parallelization of computing (in fact, any other effort) and enable quantum sensing beyond the standard quantum limit. we also expose a fundamental vulnerability of any nonlinear modification of quantum mechanics—these modifications are highly sensitive to cosmic history and their locally exploitable effects can dynamically disappear if the observed universe has a tiny overlap with the overall quantum state of the universe, as is predicted in conventional inflationary cosmology. we identify observables that should persist in this case and discuss opportunities to detect them in cosmic ray experiments, tests of strong field general relativity and current probes of the equation of state of the universe. nonlinear quantum mechanics also enables novel gravitational phenomena and may open new directions to solve the black hole information problem and to uncover the theory underlying quantum field theory and gravitation. | causal framework for nonlinear quantum mechanics |
supermassive black holes (smbhs) are thought to originate from early universe seed black holes of mass m bh ~ 102-105 m ⊙ and grown through cosmic time. such seeds could be powering the active galactic nuclei (agn) found in today's dwarf galaxies. however, probing a connection between the early seeds and local smbhs has not yet been observationally possible. massive black holes hosted in dwarf galaxies at intermediate redshifts, on the other hand, may represent the evolved counterparts of the seeds formed at very early times. we present a sample of seven broad-line agn in dwarf galaxies with a spectroscopic redshift ranging from z = 0.35 to z = 0.93. the sources are drawn from the vipers survey as having an large magellanic cloud (lmc) like stellar mass (m ∗) derived from spectral energy distribution fitting, and they are all star-forming galaxies. six of these sources are also x-ray agn. the agn are powered by smbhs of >107 m ⊙, more massive than expected from the m bh-m ∗ scaling relation of agn. based on semianalytical simulations, we find that these objects are likely overmassive with respect to their hosts since early times (z > 4), independently of whether they formed as heavy (~105 m ⊙) or light (~102 m ⊙) seed black holes. in our simulations, these objects tend to grow faster than their host galaxies, contradicting models of synchronized growth. the host galaxies are found to possibly evolve into massive systems by z ~ 0, indicating that local smbhs in massive galaxies could originate in dwarf galaxies hosting seed black holes at higher z. | overmassive black holes in dwarf galaxies out to z 0.9 in the vipers survey |
we explore the possibility that relativistic protons in the extremely powerful jets of blazars may boost via elastic collisions the dark matter particles in the surroundings of the source to high energies. we concentrate on two sample blazars, txs 0506 +056 , towards which icecube recently reported evidence for a high-energy neutrino flux, and bl lacertae, a representative nearby blazar. we find that the dark matter flux at earth induced by these sources may be sizable, larger than the flux associated with the analogous process of dark matter boosted by galactic cosmic rays, and relevant to access direct detection for dark matter particle masses lighter than 1 gev. from the null detection of a signal by xenon1t, miniboone, and borexino, we derive limits on dark matter-nucleus spin-independent and spin-dependent cross sections which, depending on the modelization of the source, improve on other currently available bounds for light dark matter candidates of 1 up to 5 orders of magnitude. | direct detection constraints on blazar-boosted dark matter |
the antarctic impulsive transient antenna (anita) balloon experiment was designed to detect radio signals initiated by high-energy neutrinos and cosmic ray (cr) air showers. these signals are typically discriminated by the polarization and phase inversions of the radio signal. the reflected signal from crs suffer phase inversion compared to a direct 'tau neutrino' event. in this paper, we study subsurface reflection, which can occur without phase inversion, in the context of the two anomalous up-going events reported by anita. it is found that subsurface layers and firn density inversions may plausibly account for the events, while ice fabric layers and wind ablation crusts could also play a role. this hypothesis can be tested with radar surveying of the antarctic region in the vicinity of the anomalous anita events. future experiments should not use phase inversion as a sole criterion to discriminate between down-going and up-going events, unless the subsurface reflection properties are well understood. | reflections on the anomalous anita events: the antarctic subsurface as a possible explanation |
gravitational-wave (gw) detectors can contribute to the measurement of cosmological parameters and to testing the dark-energy sector of alternatives to λcdm, by using standard sirens. in this paper we focus on binary neutron stars with a counterpart detected through a gamma-ray burst (grb), both at a second-generation network made by advanced ligo+advanced virgo+ligo india+kagra, and at third-generation (3g) detectors, discussing in particular the cases of a single einstein telescope (et), and of a network of et plus two cosmic explorer (ce). we construct mock catalogs of standard sirens, using different scenarios for the local merger rate and for the detection of the electromagnetic counterpart. for 3g detectors we estimate the coincidences with a grb detector with the characteristics of the proposed theseus mission. we discuss how these standard sirens with a grb counterpart can improve the determination of cosmological parameters (and particularly of h0) in λcdm, and we then study how to extract information on dark energy, considering both a non-trivial dark energy equation of state and modified gw propagation. we find that a 2g detector network can already reach, over several years of data taking, an interesting sensitivity to modified gw propagation, while a single et detector would have a remarkable potential for discovery. we also find that, to fully exploit the potential of a et+ce+ce network, it is necessary a much stronger program of search for electromagnetic counterparts (or else to resort to statistical methods for standard sirens), and furthermore gravitational lensing can become a limiting factor. | cosmology and dark energy from joint gravitational wave-grb observations |
gravitational-wave detectors can be used to search for yet-undiscovered ultralight bosons, including those conjectured to solve problems in particle physics, high-energy theory, and cosmology. in particular, ground-based instruments could probe boson masses between 10-15 ev and 10-11 ev , which are largely inaccessible to other experiments. in this paper, we explore the prospect of searching for the continuous gravitational waves generated by boson clouds around known black holes. we carefully study the predicted waveforms and use the latest-available numerical results to model signals for different black-hole and boson parameters. we then demonstrate the suitability of a specific method (hidden markov model tracking) to efficiently search for such signals, even when the source parameters are not perfectly known as well as allowing for some uncertainty in theoretical predictions. we empirically study this method's sensitivity and computational cost in the context of boson signals, finding that it will be possible to target remnants from compact-binary mergers localized with at least three instruments. for signals from scalar clouds, we also compute detection horizons for future detectors (advanced ligo, ligo voyager, cosmic explorer, and the einstein telescope). among other results, we find that, after one year of observation, an advanced ligo detector at design sensitivity could detect these sources up to over 100 mpc, while cosmic explorer could reach over 1 04 mpc . these projections offer a more complete picture than previous estimates based on analytic approximations to the signal power or idealized search strategies. finally, we discuss specific implications for the follow-up of compact-binary coalescences and black holes in x-ray binaries. along the way, we review the basic physics of bosons around black holes, in the hope of providing a bridge between the theory and data-analysis literatures. | directed searches for gravitational waves from ultralight bosons |
we report on the host properties of five x-ray-luminous active galactic nuclei (agn) identified at 3 < z < 5 in the first epoch of imaging from the cosmic evolution early release science survey. each galaxy has been imaged with the jwst near-infrared camera, which provides rest-frame optical morphologies at these redshifts. we also derive stellar masses and star formation rates for each host by fitting its spectral energy distribution using a combination of galaxy and agn templates. we find that three of the agn hosts have spheroidal morphologies, one is a bulge-dominated disk, and one is dominated by pointlike emission. none are found to show strong morphological disturbances that might indicate a recent interaction or merger event. when compared to a sample of mass-matched inactive galaxies, we find that the agn hosts have morphologies that are less disturbed and more bulge-dominated. notably, all four of the resolved hosts have rest-frame optical colors consistent with a quenched or poststarburst stellar population. the presence of agn in passively evolving galaxies at z > 3 is significant because a rapid feedback mechanism is required in most semianalytic models and cosmological simulations to explain the growing population of massive quiescent galaxies observed at these redshifts. our findings show that agn can continue to inject energy into these systems after their star formation is curtailed, potentially heating their halos and preventing renewed star formation. additional observations will be needed to determine what role this feedback may play in helping to quench these systems and/or maintain their quiescent state. | ceers key paper. ii. a first look at the resolved host properties of agn at 3 < z < 5 with jwst |
the diffuse galactic gamma-ray flux between 0.1 and 1 pev has recently been measured by the tibet asγ collaboration. the flux and spectrum are consistent with the decay of neutral pions from hadronuclear interactions between galactic cosmic rays and the interstellar medium (ism). we derive the flux of the galactic diffuse neutrino emission from the same interaction process that produces the gamma rays. our calculation accounts for the effect of gamma-ray attenuation inside the milky way and uncertainties due to the spectrum and distribution of cosmic rays, gas density, and infrared emission of the ism. we find that the contribution from the galactic plane (gp) to the all-sky neutrino flux is ≲5%-10% around 100 tev. the galactic and extragalactic neutrino intensities are comparable in the gp region. our results are consistent with the upper limit reported by the icecube and antares collaborations, and predict that next-generation neutrino experiments may observe the galactic component. we also show that the tibet asγ data imply either an additional component in the cosmic-ray nucleon spectrum or contribution from discrete sources, including pevatrons such as superbubbles and hypernova remnants, and pev electron accelerators. future multimessenger observations between 1 tev and 1 pev are crucial to decomposing the origin of sub-pev gamma-rays. | multimessenger implications of sub-pev diffuse galactic gamma-ray emission |
current and upcoming radio interferometric experiments are aiming to make a statistical characterization of the high-redshift 21 cm fluctuation signal spanning the hydrogen reionization and x-ray heating epochs of the universe. however, connecting 21 cm statistics to the underlying physical parameters is complicated by the theoretical challenge of modeling the relevant physics at computational speeds quick enough to enable exploration of the high-dimensional and weakly constrained parameter space. in this work, we use machine learning algorithms to build a fast emulator that can accurately mimic an expensive simulation of the 21 cm signal across a wide parameter space. we embed our emulator within a markov chain monte carlo framework in order to perform bayesian parameter constraints over a large number of model parameters, including those that govern the epoch of reionization, the epoch of x-ray heating, and cosmology. as a worked example, we use our emulator to present an updated parameter constraint forecast for the hydrogen epoch of reionization array experiment, showing that its characterization of a fiducial 21 cm power spectrum will considerably narrow the allowed parameter space of reionization and heating parameters, and could help strengthen planck's constraints on {σ }8. we provide both our generalized emulator code and its implementation specifically for 21 cm parameter constraints as publicly available software. | emulating simulations of cosmic dawn for 21 cm power spectrum constraints on cosmology, reionization, and x-ray heating |
the existence of diffuse galactic neutrino production is expected from cosmic-ray interactions with galactic gas and radiation fields. thus, neutrinos are a unique messenger offering the opportunity to test the products of galactic cosmic-ray interactions up to energies of hundreds of tev. here we present a search for this production using ten years of astronomy with a neutrino telescope and abyss environmental research (antares) track and shower data, as well as seven years of icecube track data. the data are combined into a joint likelihood test for neutrino emission according to the kra{}γmodel assuming a 5 pev per nucleon galactic cosmic-ray cutoff. no significant excess is found. as a consequence, the limits presented in this letter start constraining the model parameter space for galactic cosmic-ray production and transport. | joint constraints on galactic diffuse neutrino emission from the antares and icecube neutrino telescopes |
while the radio detection of cosmic rays has advanced to a standard method in astroparticle physics, the radio detection of neutrinos is just about to start its full bloom. the successes of pilot-arrays have to be accompanied by the development of modern and flexible software tools to ensure rapid progress in reconstruction algorithms and data processing. we present nuradioreco as such a modern python-based data analysis tool. it includes a suitable data-structure, a database-implementation of a time-dependent detector, modern browser-based data visualization tools, and fully separated analysis modules. we describe the framework and examples, as well as new reconstruction algorithms to obtain the full three-dimensional electric field from distributed antennas which is needed for high-precision energy reconstruction of particle showers. | nuradioreco: a reconstruction framework for radio neutrino detectors |
we study the spectral energy distribution (sed) of the radio continuum (rc) emission from the key insight in nearby galaxies emitting in radio (kingfisher) sample of nearby galaxies to understand the energetics and origin of this emission. effelsberg multi-wavelength observations at 1.4, 4.8, 8.4, and 10.5 ghz combined with archive data allow us, for the first time, to determine the mid-rc (1-10 ghz, mrc) bolometric luminosities and further present calibration relations versus the monochromatic radio luminosities. the 1-10 ghz radio sed is fitted using a bayesian markov chain monte carlo technique leading to measurements for the nonthermal spectral index ({s}ν ∼ {ν }-{α {nt}}) and the thermal fraction ({f}{th}) with mean values of {α }{nt}=0.97 +/- 0.16(0.79 +/- 0.15 for the total spectral index) and {f}{th} = (10 ± 9)% at 1.4 ghz. the mrc luminosity changes over ∼3 orders of magnitude in the sample, 4.3× {10}2 {l}⊙< mrc < 3.9× {10}5 {l}⊙ . the thermal emission is responsible for ∼23% of the mrc on average. we also compare the extinction-corrected diagnostics of the star-formation rate (sfr) with the thermal and nonthermal radio tracers and derive the first star-formation calibration relations using the mrc radio luminosity. the nonthermal spectral index flattens with increasing sfr surface density, indicating the effect of the star-formation feedback on the cosmic-ray electron population in galaxies. comparing the radio and ir seds, we find that the fir-to-mrc ratio could decrease with sfr, due to the amplification of the magnetic fields in star-forming regions. this particularly implies a decrease in the ratio at high redshifts, where mostly luminous/star-forming galaxies are detected. | the radio spectral energy distribution and star-formation rate calibration in galaxies |
we present a multi-messenger model for the prompt emission from grb 221009a within the internal shock scenario. we consider the time-dependent evolution of the outflow with its impact on the observed light curve from multiple collisions, as well as the self-consistent generation of the electromagnetic spectrum in synchrotron and inverse compton-dominated scenarios. our lepto-hadronic model includes uhe protons potentially accelerated in the outflow, and their feedback on spectral energy distribution and on the neutrino emission. we find that we can roughly reproduce the observed light curves with an engine with varying ejection velocity of ultrarelativistic material, which has an intermediate quiescent period of about 200 s and a variability timescale of ~1 s. we consider baryonic loadings of 3 and 30 that are compatible with the hypothesis that the highest-energetic lhaaso photons might come from uhecr interactions with the extragalactic background light, and the paradigm that energetic grbs may power the uhecr flux. for these values and the high dissipation radii considered, we find consistency with the nonobservation of neutrinos and no significant signatures on the electromagnetic spectrum. inverse compton-dominated scenarios from the prompt emission are demonstrated to lead to about an order of magnitude higher fluxes in the he range; this enhancement is testable via its spectral impact in the fermi-gbm and lat ranges. | multi-messenger model for the prompt emission from grb 221009a |
muography consists in observing the differential absorption of muons - elementary particles produced through cosmic-ray interactions in the earth atmosphere - going through the volcano and can attain a spatial resolution of tens of meters. we present here the first experiment of nuclear emulsion muography at the stromboli volcano. muons have been recorded during a period of five months by a detector of 0.96 m2 area. the emulsion films were prepared at the gran sasso underground laboratory and were analyzed at napoli, salerno and tokyo scanning laboratories. our results highlight a significant low-density zone at the summit of the volcano with density contrast of 30-40% with respect to bedrock. the structural setting of this part of the volcanic edifice controls the eruptive dynamics and the stability of the "sciara del fuoco" slope, which is affected by recurrent tsunamigenic landslides. periodical imaging of the summit of the stromboli volcano such as that provided by muography can become a useful method for studying the evolution of the internal structure of the volcanic edifice. | first muography of stromboli volcano |
the next generation magnetic spectrometer in space, ams-100, is designed to have a geometrical acceptance of 100 m 2 sr and to be operated for at least ten years at the sun-earth lagrange point 2. compared to existing experiments, it will improve the sensitivity for the observation of new phenomena in cosmic rays, and in particular in cosmic antimatter, by at least a factor of 1000. the magnet design is based on high temperature superconductor tapes, which allow the construction of a thin solenoid with a homogeneous magnetic field of 1 tesla inside. the inner volume is instrumented with a silicon tracker reaching a maximum detectable rigidity of 100 tv and a calorimeter system that is 70 radiation lengths deep, equivalent to four nuclear interaction lengths, which extends the energy reach for cosmic-ray nuclei up to the pev scale, i.e. beyond the cosmic-ray knee. covering most of the sky continuously, ams-100 will detect high-energy gamma-rays in the calorimeter system and by pair conversion in the thin solenoid, reconstructed with excellent angular resolution in the silicon tracker. | ams-100: the next generation magnetic spectrometer in space - an international science platform for physics and astrophysics at lagrange point 2 |
we investigate current and future prospects for coincident detection of high-energy neutrinos and gravitational waves (gws). short gamma-ray bursts (sgrbs) are believed to originate from mergers of compact star binaries involving neutron stars. we estimate high-energy neutrino fluences from prompt emission, extended emission (ee), x-ray flares, and plateau emission, and we show that neutrino signals associated with the ee are the most promising. assuming that the cosmic-ray loading factor is ∼10 and the lorentz factor distribution is lognormal, we calculate the probability of neutrino detection from ee by current and future neutrino detectors, and we find that the quasi-simultaneous detection of high-energy neutrinos, gamma-rays, and gws is possible with future instruments or even with current instruments for nearby sgrbs having ee. we also discuss stacking analyses that will also be useful with future experiments such as icecube-gen2. | high-energy neutrino emission from short gamma-ray bursts: prospects for coincident detection with gravitational waves |
observations indicate that a continuous supply of gas is needed to maintain observed star formation rates in large, discy galaxies. to fuel star formation, gas must reach the inner regions of such galaxies. despite its crucial importance for galaxy evolution, how and where gas joins galaxies is poorly constrained observationally and rarely explored in fully cosmological simulations. to investigate gas accretion in the vicinity of galaxies at low redshift, we analyse the fire-2 cosmological zoom-in simulations for 4 milky way mass galaxies (mhalo ~ 1012m⊙), focusing on simulations with cosmic ray physics. we find that at z ~ 0, gas approaches the disc with angular momentum similar to the gaseous disc edge and low radial velocities, piling-up near the edge and settling into full rotational support. accreting gas moves predominately parallel to the disc and joins largely in the outskirts. immediately prior to joining the disc, trajectories briefly become more vertical on average. within the disc, gas motion is complex, being dominated by spiral arm induced oscillations and feedback. however, time and azimuthal averages show slow net radial infall with transport speeds of 1-3 km s-1 and net mass fluxes through the disc of ~m⊙ yr-1, comparable to the galaxies' star formation rates and decreasing towards galactic centre as gas is sunk into star formation. these rates are slightly higher in simulations without cosmic rays (1-7 km s-1, ~4-5 m⊙ yr-1). we find overall consistency of our results with observational constraints and discuss prospects of future observations of gas flows in and around galaxies. | gas infall and radial transport in cosmological simulations of milky way-mass discs |
the high altitude water cherenkov (hawc) gamma-ray observatory is a wide field of view observatory sensitive to 500 gev-100 tev gamma-rays and cosmic rays. it can also perform diverse indirect searches for dark matter annihilation and decay. among the most promising targets for the indirect detection of dark matter are dwarf spheroidal galaxies. these objects are expected to have few astrophysical sources of gamma-rays but high dark matter content, making them ideal candidates for an indirect dark matter detection with gamma-rays. here we present individual limits on the annihilation cross section and decay lifetime for 15 dwarf spheroidal galaxies within the field of view, as well as their combined limit. these are the first limits on the annihilation cross section and decay lifetime using data collected with hawc. we also present the hawc flux upper limits of the 15 dwarf spheroidal galaxies in half-decade energy bins. | dark matter limits from dwarf spheroidal galaxies with the hawc gamma-ray observatory |
light dark matter (dm), defined here as having a mass between 1 mev and about 1 gev, is an interesting possibility both theoretically and phenomenologically, at one of the frontiers of current progress in the field of dm searches. its indirect detection via gamma rays is challenged by the scarcity of experiments in the mev-gev region. we look therefore at lower-energy x-ray data from the integral telescope, and compare them with the predicted dm flux. we derive bounds which are competitive with existing ones from other techniques. crucially, we include the contribution from inverse compton scattering on galactic radiation fields and the cosmic microwave background, which leads to much stronger constraints than in previous studies for dm masses above 20 mev. | integral x-ray constraints on sub-gev dark matter |
more than 80 years after its first postulation in modern form, the existence and distribution of dark matter in our universe is well established. dark matter is the gravitational glue that holds together galaxies, galaxy clusters and structures on the largest cosmological scales, and an essential component to explain the observed fluctuations in the cosmic microwave background. yet its existence is inferred indirectly, through its gravitational influence on luminous matter, and its nature is not known. a viable hypothesis is that dark matter is made of new, elementary particles, with allowed masses and interaction strengths spanning a wide range. two well-motivated classes of candidates are axions and weakly interacting massive particles (wimps), and experimental efforts have now reached sensitivities that allow them to test this hypothesis. axions, produced non-thermally in the early universe, can be detected by exploiting their predicted couplings to photons and electrons. wimps can be detected directly by looking for their collisions with atomic nuclei ultra-low background detectors, or indirectly, through the observation of their annihilation products such as neutrinos, gamma rays, positrons and antiprotons over the astrophysical background. a complementary method is the production of dark matter particles at colliders such as the large hadron collider, where they could be observed indirectly via missing transverse energy, or via associated particle production. i will review the main experimental efforts to search for dark matter particles, and the existing constraints on the interaction cross sections. i will also discuss future experiments, their complementarity and their ability to measure the properties of these particles. | dark matter detection |
we study the possibility to directly detect the boosted dark matter generated from the scatterings with high energetic cosmic particles, such as protons and electrons. as a concrete example, we consider the sub-gev dark matter mediated by a u (1 )d gauge boson, which has a mixing with a u (1 )y gauge boson in the standard model. the enhanced kinetic energy of the light dark matter from the collision with the cosmic rays can recoil the target nucleus and electron in the underground direct detection experiments, transferring enough energy to them to be detectable. we show the impact of boosted dark matter with existing direct detection experiments as well as collider and beam-dump experiments. | searching for boosted dark matter mediated by a new gauge boson |
the characteristics of an aboveground cosmic-ray neutron sensor (crns) are evaluated for monitoring a mountain snowpack in the austrian alps from march 2014 to june 2016. neutron counts were compared to continuous point-scale snow depth (sd) and snow-water-equivalent (swe) measurements from an automatic weather station with a maximum swe of 600 mm (april 2014). several spatially distributed terrestrial laser scanning (tls)-based sd and swe maps were additionally used. a strong nonlinear correlation is found for both sd and swe. the representative footprint of the crns is in the range of 230-270 m. in contrast to previous studies suggesting signal saturation at around 100 mm of swe, no complete signal saturation was observed. these results imply that crns could be transferred into an unprecedented method for continuous detection of spatially averaged sd and swe for alpine snowpacks, though with sensitivity decreasing with increasing swe. while initially different functions were found for accumulation and melting season conditions, this could be resolved by accounting for a limited measurement depth. this depth limit is in the range of 200 mm of swe for dense snowpacks with high liquid water contents and associated snow density values around 450 kg m-3 and above. in contrast to prior studies with shallow snowpacks, interannual transferability of the results is very high regardless of presnowfall soil moisture conditions. this underlines the unexpectedly high potential of crns to close the gap between point-scale measurements, hydrological models, and remote sensing of the cryosphere in alpine terrain. | continuous monitoring of snowpack dynamics in alpine terrain by aboveground neutron sensing |
motivated by the very recent cosmic-ray electron+positron excess observed by dampe collaboration, we investigate a dirac fermion dark matter (dm) in the gauged {{l_e} - {l_μ }} model. dm interacts with the electron and muon via the u(1)_{e-μ } gauge boson z^' . the model can explain the dampe data well. although a non-zero dm-nucleon cross section is only generated at one loop level and there is a partial cancellation between z^' }ee and z^' }μ μ couplings, we find that a large portion of z' mass is ruled out from direct dm detection limit leaving the allowed z^' } mass to be close to two times of the dm mass. implications for pp → z^' } → 2ℓ and pp → 2ℓ + z^' }, and muon g-2 anomaly are also studied. | leptophilic dark matter in gauged u(1)_{l{_e}-l_{μ }} model in light of dampe cosmic ray {e{^+}} + {e{^-}} excess |
we use fully kinetic particle-in-cell simulations with unprecedentedly large transverse box sizes to study particle acceleration in weakly magnetized mildly relativistic shocks travelling at a velocity ≈ 0.75c and a mach number of 15. we examine both subluminal (quasi-parallel) and superluminal (quasi-perpendicular) magnetic field orientations. we find that quasi-parallel shocks are mediated by a filamentary non-resonant (bell) instability driven by returning ions, producing magnetic fluctuations on scales comparable to the ion gyroradius. in quasi-parallel shocks, both electrons and ions are accelerated into non-thermal power laws whose maximum energy grows linearly with time. the upstream heating of electrons is small, and the two species enter the shock front in rough thermal equilibrium. the shock's structure is complex; the current of returning non-thermal ions evacuates cavities in the upstream that form filaments of amplified magnetic fields once advected downstream. at late times, 10 per cent of the shock's energy goes into non-thermal protons and ≳ 10 per cent into magnetic fields. we find that properly capturing the magnetic turbulence driven by the non-thermal ions is important for properly measuring the energy fraction of non-thermal electrons, ɛe. we find ɛe ∼ 5 × 10-4 for quasi-parallel shocks with v = 0.75c, slightly larger than what was measured in simulations of non-relativistic shocks. in quasi-perpendicular shocks, no non-thermal power-law develops in ions or electrons. the ion acceleration efficiency in quasi-parallel shocks suggests that astrophysical objects that could host mildly relativistic quasi-parallel shocks - for example, the jets of active galactic nuclei or microquasars - may be important sources of cosmic rays and their secondaries, such as gamma-rays and neutrinos. | kinetic simulations of mildly relativistic shocks - i. particle acceleration in high mach number shocks |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.