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the local cosmic-ray (cr) spectra are calculated for typical characteristic regions of a cold, dense molecular cloud to investigate two mechanisms of dust charging that have, thus far, been neglected: the collection of suprathermal cr electrons and protons by grains and photoelectric emission from grains due to the uv radiation generated by crs. these two mechanisms add to the conventional charging by ambient plasma, produced in the cloud by crs. we show that the cr-induced photoemission can dramatically modify the charge distribution function for submicron grains. we demonstrate the importance of the obtained results for dust coagulation: while the charging by ambient plasma alone leads to a strong coulomb repulsion between grains and inhibits their further coagulation, the combination with the photoemission provides optimum conditions for the growth of large dust aggregates in a certain region of the cloud, corresponding to the densities n({{{h}}}2) between ∼104 and ∼106 cm-3. the charging effect of crs is of a generic nature, and is therefore expected to operate not only in dense molecular clouds but also in the upper layers and the outer parts of protoplanetary disks. | interstellar dust charging in dense molecular clouds: cosmic ray effects |
the intra-cluster medium contains cosmic rays and magnetic fields that are manifested through the large scale synchrotron sources, termed radio haloes, relics, and mini-haloes. the extended giant metrewave radio telescope (gmrt) radio halo survey (egrhs) is an extension of the gmrt radio halo survey (grhs) designed to search for radio haloes using gmrt 610/235 mhz observations. the grhs and egrhs consists of 64 clusters in the redshift range 0.2-0.4 that have an x-ray luminosity larger than 5 × 1044 erg s-1 in the 0.1-2.4 kev band and declination, δ > -31° in the reflex and ebcs x-ray cluster catalogues. in this second paper in the series, gmrt 610/235 mhz data on the last batch of 11 galaxy clusters and the statistical analysis of the full sample are presented. a new mini-halo in rx j2129.6+0005 and candidate diffuse sources in z5247, a2552, and z1953 have been discovered. a unique feature of this survey are the upper limits on the detections of 1 mpc sized radio haloes; 4 new are presented here, making a total of 31 in the survey. of the sample, 58 clusters with adequately sensitive radio information were used to obtain the most accurate occurrence fractions so far. the occurrence fractions of radio haloes, mini-haloes and relics in our sample are ~22%, ~16% and ~5%, respectively. the p1.4 ghz-lx diagrams for the radio haloes and mini-haloes are presented. the morphological estimators - centroid shift (w), concentration parameter (c), and power ratios (p3/p0) derived from the chandra x-ray images - are used as proxies for the dynamical states of the grhs and egrhs clusters. the clusters with radio haloes and mini-haloes occupy distinct quadrants in the c-w, c-p3/p0 and w-p3/p0 planes, corresponding to the more and less morphological disturbance, respectively. the non-detections span both the quadrants. appendices are available in electronic form at http://www.aanda.org | the extended gmrt radio halo survey. ii. further results and analysis of the full sample |
following the discovery of the cosmic rays by victor hess in 1912, more than 70 years and numerous technological developments were needed before an unambiguous detection of the first very-high-energy gamma-ray source in 1989 was made. since this discovery, the field on very-high-energy gamma-ray astronomy experienced a true revolution: a second, then a third generation of instruments were built, observing the atmospheric cascades from the ground, either through the atmospheric cherenkov light they comprise, or via the direct detection of the charged particles they carry. present arrays, 100 times more sensitive than the pioneering experiments, have detected a large number of astrophysical sources of various types, thus opening a new window on the non-thermal universe. new, even more sensitive instruments are currently being built; these will allow us to explore further this fascinating domain. in this article we describe the detection techniques, the history of the field and the prospects for the future of ground-based very-high-energy gamma-ray astronomy. | ground-based detectors in very-high-energy gamma-ray astronomy |
we present measurements of the large-scale cosmic-ray (cr) anisotropies in r.a., using data collected by the surface detector array of the pierre auger observatory over more than 14 yr. we determine the equatorial dipole component, d\perp, through a fourier analysis in r.a. that includes weights for each event so as to account for the main detector-induced systematic effects. for the energies at which the trigger efficiency of the array is small, the "east-west" method is employed. besides using the data from the array with detectors separated by 1500 m, we also include data from the smaller but denser subarray of detectors with 750 m separation, which allows us to extend the analysis down to ∼0.03 eev. the most significant equatorial dipole amplitude obtained is that in the cumulative bin above 8 eev, d\perp={6.0}-0.9+1.0 %, which is inconsistent with isotropy at the 6σ level. in the bins below 8 eev, we obtain 99% cl upper bounds on d⊥ at the level of 1%-3%. at energies below 1 eev, even though the amplitudes are not significant, the phases determined in most of the bins are not far from the r.a. of the galactic center, at αgc = -94°, suggesting a predominantly galactic origin for anisotropies at these energies. the reconstructed dipole phases in the energy bins above 4 eev point instead to r.a. that are almost opposite to the galactic center one, indicative of an extragalactic cr origin. | cosmic-ray anisotropies in right ascension measured by the pierre auger observatory |
we present the prospects for the pre-merger detection and localization of binary neutron star mergers with third-generation gravitational-wave (gw) observatories. we consider a wide variety of gw networks that may be operating in the 2030s and beyond; these networks include up to two cosmic explorer (ce) sites, the einstein telescope (et), and continued observation with the existing second-generation ground-based detectors. for a fiducial local merger rate of 300 gpc-3 yr-1, we find that the et on its own is able to detect six and two sources per year at 5 and 30 minutes before merger, respectively, while providing a localization of <10 deg2. a single ce would detect but be unable to localize sources on its own. a two-detector ce network, however, would detect 22 and 0.4 mergers per year using the same criteria. a full three-detector network with the operation of dual ces and the et would allow for <1 deg2 source localization at 5 minutes before merger for ~seven sources per year. given the dramatic increase in localization and detection capabilities, third-generation observatories will enable the regular observation of the prompt emission of mergers by a broad array of observatories including gamma-ray, x-ray, and optical telescopes. moreover, sub-degree localizations minutes before merger, combined with narrow-field-of-view high-energy telescopes, could strongly constrain the high-energy pre-merger emission models proposed in the last decade. | pre-merger localization of compact-binary mergers with third-generation observatories |
we investigated whether ammonia-rich constituents are present on the surface of the uranian moon ariel by analyzing 32 near-infrared reflectance spectra collected over a wide range of sub-observer longitudes and latitudes. we measured the band areas and depths of a 2.2 μm feature in these spectra, which has been attributed to ammonia-bearing species on other icy bodies. ten spectra display prominent 2.2 μm features with band areas and depths >2σ. we determined the longitudinal distribution of the 2.2 μm band, finding no statistically meaningful differences between ariel's leading and trailing hemispheres, indicating that this band is distributed across ariel's surface. we compared the band centers and shapes of the five ariel spectra displaying the strongest 2.2 μm bands to laboratory spectra of various ammonia-bearing and ammonium-bearing species, finding that the spectral signatures of the ariel spectra are best matched by ammonia-hydrates and flash frozen ammonia-water solutions. our analysis also revealed that four ariel spectra display 2.24 μm bands (>2σ band areas and depths), with band centers and shapes that are best matched by ammonia ice. because ammonia should be efficiently removed over short timescales by ultraviolet photons, cosmic rays, and charged particles trapped in uranus' magnetosphere, the possible presence of this constituent supports geologic activity in the recent past, such as emplacement of ammonia-rich cryolavas and exposure of ammonia-rich deposits by tectonism, impact events, and mass wasting. | evidence for ammonia-bearing species on the uranian satellite ariel supports recent geologic activity |
non-ideal magnetohydrodynamic (mhd) effects have been shown recently as a robust mechanism of averting the magnetic braking 'catastrophe' and promoting protostellar disc formation. however, the magnetic diffusivities that determine the efficiency of non-ideal mhd effects are highly sensitive to microphysics. we carry out non-ideal mhd simulations to explore the role of microphysics on disc formation and the interplay between ambipolar diffusion (ad) and hall effect during the protostellar collapse. we find that removing the smallest grain population (≲10 nm) from the standard mrn size distribution is sufficient for enabling disc formation. further varying the grain sizes can result in either a hall-dominated or an ad-dominated collapse; both form discs of tens of au in size regardless of the magnetic field polarity. the direction of disc rotation is bimodal in the hall-dominated collapse but unimodal in the ad-dominated collapse. we also find that ad and hall effect can operate either with or against each other in both radial and azimuthal directions, yet the combined effect of ad and hall is to move the magnetic field radially outward relative to the infalling envelope matter. in addition, microphysics and magnetic field polarity can leave profound imprints both on observables (e.g. outflow morphology, disc to stellar mass ratio) and on the magnetic field characteristics of protoplanetary discs. including hall effect relaxes the requirements on microphysics for disc formation, so that prestellar cores with cosmic ray ionization rate of ≲2-3 × 10-16 s-1 can still form small discs of ≲10 au radius. we conclude that disc formation should be relatively common for typical prestellar core conditions, and that microphysics in the protostellar envelope is essential to not only disc formation, but also protoplanetary disc evolution. | the interplay between ambipolar diffusion and hall effect on magnetic field decoupling and protostellar disc formation |
the simultaneous detection of gravitational waves and light from the binary neutron star merger gw170817 led to independent measurements of distance and redshift, providing a direct estimate of the hubble constant h0 that does not rely on a cosmic distance ladder, nor assumes a specific cosmological model. by using gravitational waves as "standard sirens", this approach holds promise to arbitrate the existing tension between the h0 value inferred from the cosmic microwave background and those obtained from local measurements. however, the known degeneracy in the gravitational-wave analysis between distance and inclination of the source led to a h0 value from gw170817 that was not precise enough to resolve the existing tension. in this review, we summarize recent works exploiting the viewing-angle dependence of the electromagnetic signal, namely the associated short gamma-ray burst and kilonova, to constrain the system inclination and improve on h0. we outline the key ingredients of the different methods, summarize the results obtained in the aftermath of gw170817 and discuss the possible systematics introduced by each of these methods. | multi-messenger constraints on the hubble constant through combination of gravitational waves, gamma-ray bursts and kilonovae from neutron star mergers |
we explore inferences on ultrahigh energy cosmic ray (uhecr) source environments -- constrained by the spectrum and composition of uhecrs and non-observation of extremely high energy neutrinos -- and their implications for the observed high energy astrophysical neutrino spectrum. we find acceleration mechanisms producing power-law cr spectra~$\propto e^{-2}$ are compatible with uhecr data, if crs at high rigidities are in the quasi-ballistic diffusion regime as they escape their source environment. both gas-dominated and photon-dominated source environments are able to account for uhecr observations, however photon-dominated sources give a better fit. additionally, gas-dominated sources are in tension with current neutrino constraints. accurate measurement of the neutrino flux at $\sim 10$ pev will provide crucial information on the viability of gas-dominated sources, as well as whether diffusive shock acceleration is consistent with uhecr observations. we also show that uhecr sources are able to give a good fit to the high energy portion of the astrophysical neutrino spectrum, above $\sim$ pev. this common origin of uhecrs and high energy astrophysical neutrinos is natural if air shower data is interpreted with the sibyll2.3c hadronic interaction model, which gives the best-fit to uhecrs and astrophysical neutrinos in the same part of parameter space, but not for epos-lhc. | probing the environments surrounding ultrahigh energy cosmic ray accelerators and their implications for astrophysical neutrinos |
the estimate of the total electron yield is fundamental for our understanding of the test-mass charging associated with cosmic rays in the laser interferometer space antenna (lisa) pathfinder mission and in the forthcoming gravitational wave observatory lisa. to unveil the role of low energy electrons in this process owing to galactic and solar energetic particle events, in this work we study the interaction of kev and sub-kev electrons with a gold slab using a mixed monte carlo (mc) and ab-initio framework. we determine the energy spectrum of the electrons emerging from such a gold slab hit by a primary electron beam by considering the relevant energy loss mechanisms as well as the elastic scattering events. we also show that our results are consistent with experimental data and mc simulations carried out with the geant4-dna toolkit. | the role of low-energy electrons in the charging process of lisa test masses |
we review numerical methods for simulations of cosmic ray (cr) propagation on galactic and larger scales. we present the development of algorithms designed for phenomenological and self-consistent models of cr propagation in kinetic description based on numerical solutions of the fokker-planck equation. the phenomenological models assume a stationary structure of the galactic interstellar medium and incorporate diffusion of particles in physical and momentum space together with advection, spallation, production of secondaries and various radiation mechanisms. the self-consistent propagation models of crs include the dynamical coupling of the cr population to the thermal plasma. the cr transport equation is discretized and solved numerically together with the set of mhd equations in various approaches treating the cr population as a separate relativistic fluid within the two-fluid approach or as a spectrally resolved population of particles evolving in physical and momentum space. the relevant processes incorporated in self-consistent models include advection, diffusion and streaming propagation as well as adiabatic compression and several radiative loss mechanisms. we discuss, applications of the numerical models for the interpretation of cr data collected by various instruments. we present example models of astrophysical processes influencing galactic evolution such as galactic winds, the amplification of large-scale magnetic fields and instabilities of the interstellar medium. | simulations of cosmic ray propagation |
we derive a consistent set of moment equations for cosmic ray (cr)-magnetohydrodynamics, assuming a gyrotropic distribution function (df). unlike previous efforts, we derive a closure, akin to the m1 closure in radiation hydrodynamics (rhd), that is valid in both the nearly isotropic df and/or strong-scattering regimes, and the arbitrarily anisotropic df or free-streaming regimes, as well as allowing for anisotropic scattering and transport/magnetic field structure. we present the appropriate two-moment closure and equations for various choices of evolved variables, including the cr phase space df f, number density n, total energy e, kinetic energy ϵ, and their fluxes or higher moments, and the appropriate coupling terms to the gas. we show that this naturally includes and generalizes a variety of terms including convection/fluid motion, anisotropic cr pressure, streaming, diffusion, gyro-resonant/streaming losses, and re-acceleration. we discuss how this extends previous treatments of cr transport including diffusion and moment methods and popular forms of the fokker-planck equation, as well as how this differs from the analogous m1-rhd equations. we also present two different methods for incorporating a reduced speed of light (rsol) to reduce time-step limitations: in both, we carefully address where the rsol (versus true c) must appear for the correct behaviour to be recovered in all interesting limits, and show how current implementations of crs with an rsol neglect some additional terms. | a consistent reduced-speed-of-light formulation of cosmic ray transport valid in weak- and strong-scattering regimes |
recent direct measurements of galactic cosmic ray spectra by balloon/space-borne detectors reveal spectral hardenings of all major nucleus species at rigidities of a few hundred gv. the all-sky diffuse γ -ray emissions measured by the fermi large area telescope also show spatial variations of the intensities and spectral indices of cosmic rays. these new observations challenge the traditional simple acceleration and/or propagation scenario of galactic cosmic rays. in this work, we propose a spatially dependent diffusion scenario to explain all these phenomena. the diffusion coefficient is assumed to be anticorrelated with the source distribution, which is a natural expectation from the charged particle transportation in a turbulent magnetic field. the spatially dependent diffusion model also gives a lower level of anisotropies of cosmic rays, which are consistent with observations by underground muons and air shower experiments. the spectral variations of cosmic rays across the galaxy can be properly reproduced by this model. | understanding the spectral hardenings and radial distribution of galactic cosmic rays and fermi diffuse γ rays with spatially-dependent propagation |
the sources of ultrahigh-energy cosmic rays (uhecrs) have been stubbornly elusive. however, the latest report of the pierre auger observatory provides a compelling indication for a possible correlation between the arrival directions of uhecrs and nearby starburst galaxies. we argue that if starbursts are sources of uhecrs, then particle acceleration in the large-scale terminal shock of the superwind that flows from the starburst engine represents the best known concept model in the market. we investigate new constraints on the model and readjust free parameters accordingly. we show that uhecr acceleration above about 1 011 gev remains consistent with observation. we also show that the model could accommodate hard source spectra as required by auger data. we demonstrate how neutrino emission can be used as a discriminator among acceleration models. | acceleration of ultrahigh-energy cosmic rays in starburst superwinds |
the diffuse flux of cosmic neutrinos has been measured by the icecube observatory from tev to pev energies. we show that an improved characterization of this flux at lower energies, tev and sub-tev, reveals important information on the nature of the astrophysical neutrino sources in a model-independent way. most significantly, it could confirm the present indications that neutrinos originate in cosmic environments that are optically thick to gev-tev γ-rays. this conclusion will become inevitable if an uninterrupted or even steeper neutrino power law is observed in the tev region. in such γ-ray-obscured sources, the γ-rays that inevitably accompany cosmic neutrinos will cascade down to mev-gev energies. the requirement that the cascaded γ-ray flux accompanying cosmic neutrinos should not exceed the observed diffuse γ-ray background puts constraints on the peak energy and density of the radiation fields in the sources. our calculations inspired by the existing data suggest that a fraction of the observed diffuse mev-gev γ-ray background may be contributed by neutrino sources with intense radiation fields that obscure the high-energy γ-ray emission accompanying the neutrinos. | the tev diffuse cosmic neutrino spectrum and the nature of astrophysical neutrino sources |
context. starbursts are galaxies undergoing massive episodes of star formation. the combined effect of stellar winds from hot stars and supernova explosions creates a high-temperature cavity in the nuclear region of these objects. the very hot gas expands adiabatically and escapes from the galaxy creating a superwind which sweeps matter from the galactic disk. the superwind region in the halo is filled with a multi-phase gas with hot, warm, cool, and relativistic components.aims: the shocks associated with the superwind of starbursts and the turbulent gas region of the bubble inflated by them might accelerate cosmic rays up to high energies. in this work we calculate the cosmic ray production associated with the superwind using parameters that correspond to the nearby southern starburst galaxy ngc 253, which has been suggested as a potential accelerator of ultra-high-energy cosmic rays.methods: we evaluate the efficiency of both diffusive shock acceleration (dsa) and stochastic diffusive acceleration (sda) in the superwind of ngc 253. we estimate the distribution of both hadrons and leptons and calculate the corresponding spectral energy distributions of photons. the electromagnetic radiation can help to discriminate between the different scenarios analyzed.results: we find that the strong mass load of the superwind, recently determined through alma observations, strongly attenuates the efficiency of dsa in ngc 253, whereas sda is constrained by the age of the starburst.conclusions: we conclude that ngc 253 and similar starbursts can only accelerate iron nuclei beyond 1018 ev under very special conditions. if the central region of the galaxy harbors a starved supermassive black hole of 106 m⊙, as suggested by some recent observations, a contribution in the range 1018-1019 ev can be present for accretion rates ṁ 10-3 in eddington units. shock energies of the order of 100 eev might only be possible if very strong magnetic field amplification occurs close to the superwind. | particle acceleration in the superwinds of starburst galaxies |
current measurements of cosmic-ray fluxes have reached unprecedented accuracy thanks to the new generation of experiments, and in particular the ams-02 mission. at the same time, significant progress has been made in the propagation models of galactic cosmic rays. these models include several propagation parameters, which are usually inferred from the ratios of secondary to primary cosmic rays, and which depend on the cross sections describing the collisions among the various species of cosmic-ray nuclei. at present, our knowledge of these cross sections in the energy range where cosmic-ray interactions occur is limited, and this is a source of uncertainties in the predicted fluxes of secondary cosmic-ray nuclei. in this work we study the impact of the cross section uncertainties on the fluxes of light secondary nuclei (li, be, b) using a preliminary version of the upcoming dragon2 code. we first present a detailed comparison of the secondary fluxes computed by implementing different parameterizations for the network of spallation cross sections. then, we discuss the use of secondary-over-secondary cosmic-ray flux ratios as a tool to improve the consistency of cross sections parameterizations and give insight of the overall uncertainties coming from the cross sections parametrisations. we show that the uncertainties inferred from the cross section data are enough to explain the discrepancies in the be and li fluxes with respect to the ams-02 data, with no need of a primary component in their spectra. in addition, we show that the fluxes of b, be and li can be simultaneously reproduced by rescaling their cross sections within the experimental uncertainty. finally, we also revisit the diffusive estimation of the halo size, obtaining good agreement with previous works and a best fit value of 6.8 ± 1 kpc from the most updated cross sections parametrisations. | implications of current nuclear cross sections on secondary cosmic rays with the upcoming dragon2 code |
the activity of stars such as the sun varies over timescales ranging from the very short to the very long - stellar and planetary evolutionary timescales. experience from our solar system indicates that short-term, transient events such as stellar flares and coronal mass ejections create hazardous space environmental conditions that impact earth-orbiting satellites and planetary atmospheres. extreme events such as stellar superflares may play a role in atmospheric mass loss and create conditions unsuitable for life. slower, long-term evolutions of the activity of sun-like stars over millennia to billions of years result in variations in stellar wind properties, radiation flux, cosmic ray flux, and frequency of magnetic storms. this coupled evolution of star-planet systems eventually determines planetary and exoplanetary habitability. the solar evolution and extrema (see) initiative of the variability of the sun and its terrestrial impact (varsiti) program of the scientific committee on solar-terrestrial physics (scostep) aimed to facilitate and build capacity in this interdisciplinary subject of broad interest in astronomy and astrophysics. in this review, we highlight progress in the major themes that were the focus of this interdisciplinary program, namely, reconstructing and understanding past solar activity including grand minima and maxima, facilitating physical dynamo-model-based predictions of future solar activity, understanding the evolution of solar activity over earth's history including the faint young sun paradox, and exploring solar-stellar connections with the goal of illuminating the extreme range of activity that our parent star - the sun - may have displayed in the past, or may be capable of unleashing in the future. | solar evolution and extrema: current state of understanding of long-term solar variability and its planetary impacts |
we explore inferences on ultrahigh energy cosmic ray (uhecr) source environments—constrained by the spectrum and composition of uhecrs and nonobservation of extremely high energy neutrinos—and their implications for the observed high energy astrophysical neutrino spectrum. we find acceleration mechanisms producing power-law cosmic ray (cr) spectra ∝e-2 are compatible with uhecr data, if crs at high rigidities are in the quasiballistic diffusion regime as they escape their source environment. both gas-dominated and photon-dominated source environments are able to account for uhecr observations, however photon-dominated sources give a better fit. additionally, gas-dominated sources are in tension with current neutrino constraints. accurate measurement of the neutrino flux at ∼10 pev will provide crucial information on the viability of gas-dominated sources, as well as whether diffusive shock acceleration is consistent with uhecr observations. we also show that uhecr sources are able to give a good fit to the high energy portion of the astrophysical neutrino spectrum, above ∼pev . this common origin of uhecrs and high energy astrophysical neutrinos is natural if air shower data is interpreted with the sibyll2.3c hadronic interaction model, which gives the best-fit to uhecrs and astrophysical neutrinos in the same part of parameter space, but not for epos-lhc. | probing the environments surrounding ultrahigh energy cosmic ray accelerators and their implications for astrophysical neutrinos |
this paper describes the current understanding of the interaction between geospheres from a complex set of physical and chemical processes under the influence of ionization. the sources of ionization involve the earth's natural radioactivity and its intensification before earthquakes in seismically active regions, anthropogenic radioactivity caused by nuclear weapon testing and accidents in nuclear power plants and radioactive waste storage, the impact of galactic and solar cosmic rays, and active geophysical experiments using artificial ionization equipment. this approach treats the environment as an open complex system with dissipation, where inherent processes can be considered in the framework of the synergistic approach. we demonstrate the synergy between the evolution of thermal and electromagnetic anomalies in the earth's atmosphere, ionosphere, and magnetosphere. this makes it possible to determine the direction of the interaction process, which is especially important in applications related to short-term earthquake prediction. that is why the emphasis in this study is on the processes proceeding the final stage of earthquake preparation; the effects of other ionization sources are used to demonstrate that the model is versatile and broadly applicable in geophysics. | physical bases of the generation of short-term earthquake precursors: a complex model of ionization-induced geophysical processes in the lithosphere-atmosphere-ionosphere-magnetosphere system |
based on current cern infrastructure, an electron-proton collider is proposed at a centre-of-mass energy of about 9 tev. a 7 tev lhc bunch is used as the proton driver to create a plasma wakefield which then accelerates electrons to 3 tev, these then colliding with the other 7 tev lhc proton beam. although of very high energy, the collider has a modest projected integrated luminosity of 10-100 pb^{-1}. for such a collider, with a centre-of-mass energy 30 times greater than hera, parton momentum fractions, x, down to about 10^{-8} are accessible for photon virtualities, q^2, of 1 gev^2. the energy dependence of hadronic cross sections at high energies, such as the total photon-proton cross section, which has synergy with cosmic-ray physics, can be measured and qcd and the structure of matter better understood in a region where the effects are completely unknown. searches at high q^2 for physics beyond the standard model will be possible, in particular the significantly increased sensitivity to the production of leptoquarks. these and other physics highlights of a very high energy electron-proton collider are outlined. | vheep: a very high energy electron-proton collider |
radiography with cosmic ray muon scattering has proven to be a successful method of imaging nuclear material through heavy shielding. of particular interest is monitoring dry storage casks for diversion of plutonium contained in spent reactor fuel. using muon tracking detectors that surround a cylindrical cask, cosmic ray muon scattering can be simultaneously measured from all azimuthal angles, giving complete tomographic coverage of the cask interior. this paper describes the first application of filtered back projection algorithms, typically used in medical imaging, to cosmic ray muon scattering imaging. the specific application to monitoring spent nuclear fuel in dry storage casks is investigated via geant4 simulations. with a cylindrical muon tracking detector surrounding a typical spent fuel cask, simulations indicate that missing fuel bundles can be detected with a statistical significance of ∼ 18 σ in less than two days exposure and a sensitivity at 1σ to a 5% missing portion of a fuel bundle. potential detector technologies and geometries are discussed. | cosmic ray muon computed tomography of spent nuclear fuel in dry storage casks |
motivated by recent claims of a compelling ~3.5 kev emission line from nearby galaxies and galaxy clusters, we investigate a novel plasma model incorporating a charge exchange component obtained from theoretical scattering calculations. fitting this kind of component with a standard thermal model yields positive residuals around 3.5 kev, produced mostly by s xvi transitions from principal quantum numbers n ≥ 9 to the ground. such high-n states can only be populated by the charge exchange process. in this scenario, the observed 3.5 kev line flux in clusters can be naturally explained by an interaction in an effective volume of ~1 kpc3 between a ~3 kev temperature plasma and cold dense clouds moving at a few hundred kev-1. the s xvi lines at ~3.5 kev also provide a unique diagnostic of the charge exchange phenomenon in hot cosmic plasmas. | a novel scenario for the possible x-ray line feature at ~3.5 kev. charge exchange with bare sulfur ions |
the sydney university giant air-shower recorder (sugar) measured the energy spectrum of ultra-high-energy cosmic rays reconstructed from muon-detector readings, while the pierre auger observatory, looking at the same southern sky, used the calorimetric fluorescence method for the same purpose. comparison of their two spectra allows us to reconstruct the empirical dependence of the number of muons in a vertical shower on the primary energy for energies between 1 017 and 1 018.5 ev . we compare this dependence with the predictions of hadronic interaction models qgsjet-ii-04, epos-lhc and sibyll-2.3c. the empirically determined number of muons with energies above 0.75 gev in a vertical shower exceeds the simulated one by the factors ∼1.7 and ∼1.3 for 1 017 ev proton and iron primaries, respectively. the muon excess grows moderately with the primary energy, increasing by an additional factor of ∼1.2 for 1 018.5 ev primaries. | muon content of extensive air showers: comparison of the energy spectra obtained by the sydney university giant air-shower recorder and by the pierre auger observatory |
we present an efficient heating/cooling method coupled with chemistry and uv radiative transfer that can be applied to numerical simulations of the interstellar medium (ism). we follow the time-dependent evolution of hydrogen species (h2, h, h+), assume carbon/oxygen species (c, c+, co, o, and o+) are in formation-destruction balance given the nonsteady hydrogen abundances, and include essential heating/cooling processes needed to capture the thermodynamics of all ism phases. uv radiation from discrete point sources and the diffuse background is followed through adaptive ray tracing and a six-ray approximation, respectively, allowing for h2 self-shielding; cosmic-ray heating and ionization are also included. to validate our methods and demonstrate their application for a range of density, metallicity, and radiation fields, we conduct a series of tests, including the equilibrium curves of thermal pressure versus density, the chemical and thermal structure in photodissociation regions, h i-to-h2 transitions, and the expansion of h ii regions and radiative supernova remnants. careful treatment of photochemistry and cosmic-ray ionization is essential for many aspects of ism physics, including identifying the thermal pressure at which cold and warm neutral phases coexist. we caution that many current heating and cooling treatments used in galaxy formation simulations do not reproduce the correct thermal pressure and ionization fraction in the neutral ism. our new model is implemented in the mhd code athena and incorporated in the tigress simulation framework, for use in studying the star-forming ism in a wide range of environments. | photochemistry and heating/cooling of the multiphase interstellar medium with uv radiative transfer for magnetohydrodynamic simulations |
supernova remnants (snrs) have been considered to be the dominant contributors to galactic cosmic rays. however, the relation between high-energy particles trapped in snrs and cosmic rays observed at the earth remains obscure. in this paper, we fit the spectral energy distributions of 35 snrs with a simple one-zone emission model and analyze correlations of model parameters to uncover the evolution of high-energy particle distribution in snrs. we find that (1) the particle distribution in general can be described by a broken power-law function with a high-energy cutoff for all snrs; (2) the low-energy spectrum becomes harder and the break energy decreases with aging of snrs, (3) for most middle-age snrs, the energy loss timescale of electrons at the high-energy cutoff is approximately equal to the age of the corresponding remnant implying quenching of very-high-energy electron acceleration; for young snrs, this energy loss timescale is shorter than the age of snrs implying continuous electron acceleration at the cutoff energy; and for a few old age snrs, the energy loss timescale is longer than the corresponding age, which may suggest escaping of higher energy particles from snrs. finally, we comment on the implications of these results on the snr origin of galactic cosmic rays. | evolution of high-energy particle distribution in supernova remnants |
complex nitriles, such as hc3n, and ch3cn, are observed in a wide variety of astrophysical environments, including at relatively high abundances in photon-dominated regions (pdrs) and the ultraviolet exposed atmospheres of planet-forming disks. the latter have been inferred to be oxygen-poor, suggesting that these observations may be explained by organic chemistry in c-rich environments. in this study we first explore if the pdr complex nitrile observations can be explained by gas-phase pdr chemistry alone if the elemental c/o ratio is elevated. in the case of the horsehead pdr, we find that gas-phase chemistry with c/o ≳ 0.9 can indeed explain the observed nitrile abundances, increasing predicted abundances by several orders of magnitude compared to standard c/o assumptions. we also find that the nitrile abundances are sensitive to the cosmic-ray ionization treatment, and provide constraints on the branching ratios between ch3cn and ch3nc productions. in a fiducial disk model, an elevated c/o ratio increases the ch3cn and hc3n productions by more than an order of magnitude, bringing abundance predictions within an order of magnitude to what has been inferred from observations. the c/o ratio appears to be a key variable in predicting and interpreting complex organic molecule abundances in pdrs across a range of scales. | the role of c/o in nitrile astrochemistry in pdrs and planet-forming disks |
aims: future astrophysics and cosmic microwave background space missions operating in the far-infrared to millimetre part of the spectrum will require very large arrays of ultra-sensitive detectors in combination with high multiplexing factors and efficient low-noise and low-power readout systems. we have developed a demonstrator system suitable for such applications.methods: the system combines a 961 pixel imaging array based upon microwave kinetic inductance detectors (mkids) with a readout system capable of reading out all pixels simultaneously with only one readout cable pair and a single cryogenic amplifier. we evaluate, in a representative environment, the system performance in terms of sensitivity, dynamic range, optical efficiency, cosmic ray rejection, pixel-pixel crosstalk and overall yield at an observation centre frequency of 850 ghz and 20% fractional bandwidth.results: the overall system has an excellent sensitivity, with an average detector sensitivity < nepdet> =3×10-19 whz measured using a thermal calibration source. at a loading power per pixel of 50 fw we demonstrate white, photon noise limited detector noise down to 300 mhz. the dynamic range would allow the detection of 1 jy bright sources within the field of view without tuning the readout of the detectors. the expected dead time due to cosmic ray interactions, when operated in an l2 or a similar far-earth orbit, is found to be <4%. additionally, the achieved pixel yield is 83% and the crosstalk between the pixels is <-30 db.conclusions: this demonstrates that mkid technology can provide multiplexing ratios on the order of a 1000 with state-of-the-art single pixel performance, and that the technology is now mature enough to be considered for future space based observatories and experiments. | a kilo-pixel imaging system for future space based far-infrared observatories using microwave kinetic inductance detectors |
modelling of cosmic ray transport and interpretation of cosmic ray data ultimately rely on a solid understanding of the interactions of charged particles with turbulent magnetic fields. the paradigm over the last 50 years has been the so-called quasi-linear theory, despite some well-known issues. in the absence of a widely accepted extension of quasi-linear theory, wave-particle interactions must also be studied in numerical simulations where the equations of motion are directly solved in a realisation of the turbulent magnetic field. the applications of such test particle simulations of cosmic rays are manifold: testing transport theories, computing parameters like diffusion coefficients or making predictions for phenomena beyond standard diffusion theories, e.g. for cosmic ray small-scale anisotropies. in this review, we seek to give a low-level introduction to test particle simulations of cosmic rays, enabling readers to perform their own test particle simulations. we start with a review of quasi-linear theory, highlighting some of its issues and suggested extensions. next, we summarise the state-of-the-art in test particle simulations and give concrete recipes for generating synthetic turbulence. we present a couple of examples for applications of such simulations and comment on an important conceptual detail in the backtracking of particles. | test particle simulations of cosmic rays |
context. while euclid is an esa mission specifically designed to investigate the nature of dark energy and dark matter, the planned unprecedented combination of survey area (∼15 000 deg2), spatial resolution, low sky-background, and depth also make euclid an excellent space observatory for the study of the low surface brightness universe. scientific exploitation of the extended low surface brightness structures requires dedicated calibration procedures that are yet to be tested.aims: we investigate the capabilities of euclid to detect extended low surface brightness structure by identifying and quantifying sky-background sources and stray-light contamination. we test the feasibility of generating sky flat-fields to reduce large-scale residual gradients in order to reveal the extended emission of galaxies observed in the euclid survey.methods: we simulated a realistic set of euclid/vis observations, taking into account both instrumental and astronomical sources of contamination, including cosmic rays, stray-light, zodiacal light, interstellar medium, and the cosmic infrared background, while simulating the effects of background sources in the field of view.results: we demonstrate that a combination of calibration lamps, sky flats, and self-calibration would enable recovery of emission at a limiting surface brightness magnitude of μlim = 29.5−0.27+0.08 mag arcsec−2 (3σ, 10 × 10 arcsec2) in the wide survey, and it would reach regions deeper by 2 mag in the deep surveys. conclusions.euclid/vis has the potential to be an excellent low surface brightness observatory. covering the gap between pixel-to-pixel calibration lamp flats and self-calibration observations for large scales, the application of sky flat-fielding will enhance the sensitivity of the vis detector at scales larger than 1″, up to the size of the field of view, enabling euclid to detect extended surface brightness structures below μlim = 31 mag arcsec−2 and beyond. | euclid preparation. xvi. exploring the ultra-low surface brightness universe with euclid/vis |
after over 60 years, the powerful engines that accelerate ultra-high-energy cosmic rays (uhecrs) to the formidable energies at which we observe them from earth remain mysterious. assuming standard physics, we expect uhecr sources to lie within the local universe (up to a few hundred mpc). the distribution of matter in the local universe is anisotropic, and we expect this anisotropy to be imprinted on the distribution of uhecr arrival directions. even though intervening intergalactic and galactic magnetic fields deflect charged uhecrs and can distort these anisotropies, some amount of information on the distribution of the sources is preserved. in this proceedings contribution, we present the results of the joint pierre auger observatory and telescope array searches for (a) the largest-scale anisotropies (the harmonic dipole and quadrupole) and (b) correlations with a sample of nearby starburst galaxies and the 2mrs catalogue tracing stellar mass within 250 mpc. this analysis updates our previous results with the most recent available data, notably with the addition of 3 years of new telescope array data. the main finding is a correlation between the arrival directions of 12.1%−3.1%+4.5% of uhecrs detected with e ≥ 38 eev by auger or with e ≳ 49 eev by ta and the positions of nearby starburst galaxies on a 15.1°−3.0°+4.6° angular scale, with a 4.7σ post-trial significance, up from 4.2σ obtained in our previous study. | 2022 report from the auger-ta working group on uhecr arrival directions |
we revisit constraints on decaying very heavy dark matter (vhdm) using the latest ultrahigh-energy cosmic-ray (uhecr; e ≳1018 ev ) data and ultrahigh-energy (uhe) γ -ray flux upper limits, measured by the pierre auger observatory. we present updated limits on the vhdm lifetime (τχ) for masses up to ∼1015 gev , considering decay into quarks, leptons, and massive bosons. in particular, we consider not only the uhecr spectrum but their composition data that favors heavier nuclei. such a combined analysis improves the limits at ≲1012 gev because vhdm decay does not produce uhecr nuclei. we also show that the constraints from the uhe γ -ray upper limits are ∼10 more stringent than that obtained from cosmic rays, for all of the standard model final states we consider. the latter improves our limits to vhdm lifetime by a factor of two for dark matter mass ≳1012 gev . | revisiting ultrahigh-energy constraints on decaying superheavy dark matter |
in recent years, the increasing precision of direct cosmic rays measurements opened the door to high-sensitivity indirect searches of dark matter and to more accurate predictions for radiation doses received by astronauts and electronics in space. the key ingredients in the study of these phenomena are the knowledge of the local interstellar spectrum (lis) of galactic cosmic rays and the understanding of how the solar modulation affects the lis inside the heliosphere. voyager 1, ams-02, pamela, and bess measurements of proton and helium fluxes provide valuable information, allowing us to shed light on the shape of the lis and the details of the solar modulation during solar cycles 22-24. a new parametrization of the lis is presented, based on the latest data from voyager 1 and ams-02. using the framework of the force-field approximation, the solar modulation parameter is extracted from the time-dependent fluxes measured by pamela and bess. a modified version of the force-field approximation with a rigidity-dependent modulation parameter is introduced, yielding better fits than the force-field approximation. the results are compared with the modulation parameter inferred by neutron monitors. | solar modulation of the local interstellar spectrum with voyager 1, ams-02, pamela, and bess |
the nucleon satellite experiment is designed to directly investigate the energy spectra of cosmic-ray nuclei and the chemical composition (z = 1-30) in the energy range of 2-500 tev. the experimental results are presented, including the energy spectra of different abundant nuclei measured using the new kinematic lightweight energy meter (klem) technique. the primary energy is reconstructed by registration of spatial density of the secondary particles. the particles are generated by the first hadronic inelastic interaction in a carbon target. then additional particles are produced in a thin tungsten converter, by electromagnetic and hadronic interactions. the deconvolution of spectra was performed. statistical errors were presented. | energy spectra of abundant cosmic-ray nuclei in the nucleon experiment |
recent theoretical studies predict that the circumgalactic medium (cgm) around low-redshift, ~l* galaxies could have substantial non-thermal pressure support in the form of cosmic rays. however, these predictions are sensitive to the specific model of cosmic ray transport employed, which is theoretically and observationally underconstrained. in this work, we propose a novel observational constraint for calculating the lower limit of the radially averaged, effective cosmic ray transport rate, ${\kappa _{\rm eff}^{\rm min}}$. under a wide range of assumptions (so long as cosmic rays do not lose a significant fraction of their energy in the galactic disc, regardless of whether the cosmic ray pressure is important or not in the cgm), we demonstrate a well-defined relationship between ${\kappa _{\rm eff}^{\rm min}}$ and three observable galaxy properties: the total hydrogen column density, the average star formation rate, and the gas circular velocity. we use a suite of feedback in realistic environments 2 galaxy simulations with a variety of cosmic ray transport physics to demonstrate that our analytical model of ${\kappa _{\rm eff}^{\rm min}}$ is a robust lower limit of the true cosmic ray transport rate. we then apply our new model to calculate ${\kappa _{\rm eff}^{\rm min}}$ for galaxies in the cos-halos sample, and confirm this already reveals strong evidence for an effective transport rate that rises rapidly away from the interstellar medium to values ${\kappa _{\rm eff}^{\rm min}}\gtrsim 10^{30\!-\!31}\, {\rm cm}^2\, {\rm s}^{-1}$ (corresponding to anisotropic streaming velocities of $v^{\rm stream}_{\rm eff} \gtrsim 1000\, {\rm km}\, {\rm s}^{-1}$) in the diffuse cgm, at impact parameters larger than 50-100 kpc. we discuss how future observations can provide qualitatively new constraints in our understanding of cosmic rays in the cgm and intergalactic medium. | constraining cosmic ray transport with observations of the circumgalactic medium |
proposed mechanisms for the production of calcium in the first stars (population iii stars)—primordial stars that formed out of the matter of the big bang—are at odds with observations1. advanced nuclear burning and supernovae were thought to be the dominant source of the calcium production seen in all stars2. here we suggest a qualitatively different path to calcium production through breakout from the `warm' carbon-nitrogen-oxygen (cno) cycle through a direct experimental measurement of the 19f(p, γ)20ne breakout reaction down to a very low energy point of 186 kiloelectronvolts, reporting a key resonance at 225 kiloelectronvolts. in the domain of astrophysical interest2, at around 0.1 gigakelvin, this thermonuclear 19f(p, γ)20ne rate is up to a factor of 7.4 larger than the previous recommended rate3. our stellar models show a stronger breakout during stellar hydrogen burning than previously thought1,4,5, and may reveal the nature of calcium production in population iii stars imprinted on the oldest known ultra-iron-poor star, smss0313-67086. our experimental result was obtained in the china jinping underground laboratory7, which offers an environment with an extremely low cosmic-ray-induced background8. our rate showcases the effect that faint population iii star supernovae can have on the nucleosynthesis observed in the oldest known stars and first galaxies, which are key mission targets of the james webb space telescope9. | measurement of 19f(p, γ)20ne reaction suggests cno breakout in first stars |
supernova remnants (snrs) are commonly believed to be the primary sources of galactic cosmic rays. despite intensive study of the non-thermal emission of many snrs the identification of the accelerated particle type relies heavily on assumptions of ambient-medium parameters that are only loosely constrained. compelling evidence of hadronic acceleration can be provided by detecting a strong roll-off in the secondary γ-ray spectrum below the {π }0 production threshold energy of about 135 mev, the so called “pion bump.” here we use five years of fermi-large area telescope data to study the spectrum above 60 mev of the middle-aged snr w51c. a clear break in the power-law γ-ray spectrum at {e}{{break}}=290+/- 20 {{mev}} is detected with 9σ significance and we show that this break is most likely associated with the energy production threshold of {π }0mesons. a high-energy break in the γ-ray spectrum at about 2.7 gev is found with 7.5σ significance. the spectral index at energies beyond this second break is {{{γ }}}2={2.52}-0.07+0.06 and closely matches the spectral index derived by the magic collaboration above 75 gev. therefore our analysis provides strong evidence to explain the γ-ray spectrum of w51c by a single particle population of protons with a momentum spectrum best described by a broken power law with break momentum {p}{{break}}∼ 80 {{g}}{{e}}{{v}}/c. w51c is the third middle-aged snr that displays compelling evidence for cosmic-ray acceleration and thus strengthens the case of snrs as the main source of galactic cosmic rays. | revealing w51c as a cosmic ray source using fermi-lat data |
eighteen samples for 36cl cosmic-ray exposure (cre) dating were taken from glacially polished bedrocks, moraine boulders, fossil/active rock glaciers and debris-covered glaciers in fremri-grjótárdalur and hóladalur cirques in the víðinesdalur, hofsdalur and héðinsdalur valleys, close to hólar village, in the tröllaskagi peninsula, northern iceland. boulder sampling was preceded by a study of the boulder stability with the twofold aim of: ensuring that the surfaces to be sampled were stable enough for the reliable application of cre dating, and to better understand the relation between the glacier dynamics and exposition history. the results show that the glaciers which occupy the valleys in tröllaskagi began their retreat around 16 ka. later, the glaciers advanced again around 11 ka within the cirques, and small moraines were formed. thereafter, these small glaciers retreated and evolved into rock glaciers as debris from paraglacial processes accumulated on the glacier surface. the fronts of these rock glaciers stabilized definitively shortly after their formation and became eventually fossil after the melting of their internal ice. new rock glaciers and debris-covered glaciers formed afterwards, which still have internal ice at present, although their current dynamics are mostly related to subsidence. the stabilization of these rock glaciers and debris-covered glaciers is dated to the period between 7 and 3 ka, although they may have been reactivated during cold neoglacial periods. this research demonstrates the potential interest in applying cre dating methods to debris-covered glaciers and rock glaciers to determine their origin, evolution and phase of cessation of internal movement until they finally lost their internal ice and became fossil. | constraints on the timing of debris-covered and rock glaciers: an exploratory case study in the hólar area, northern iceland |
as a result of intense solar activity during the first 10 days of september, a ground level enhancement occurred on 10 september 2017. here we computed the effective dose rates in the polar region at several altitudes during the event using the derived rigidity spectra of the energetic solar protons. the contribution of different populations of energetic particles, namely, galactic cosmic rays and solar protons, to the exposure is explicitly considered and compared. we also assessed the exposure of a crew members/passengers to radiation at different locations and at several cruise flight altitudes and calculated the received doses for two typical intercontinental flights. the estimated received dose during a high latitude, 40 kft, ∼10-hr flight is ∼100 μsv. | assessment of the radiation environment at commercial jet-flight altitudes during gle 72 on 10 september 2017 using neutron monitor data |
the origins of the elements and isotopes of cosmic material is a critical aspect of understanding the evolution of the universe. nucleosynthesis typically requires physical conditions of high temperatures and densities. these are found in the big bang, in the interiors of stars, and in explosions with their compressional shocks and high neutrino and neutron fluxes. many different tools are available to disentangle the composition of cosmic matter, in material of extraterrestrial origins such as cosmic rays, meteorites, stardust grains, lunar and terrestrial sediments, and through astronomical observations across the electromagnetic spectrum. understanding cosmic abundances and their evolution requires combining such measurements with approaches of astrophysical, nuclear theories and laboratory experiments, and exploiting additional cosmic messengers, such as neutrinos and gravitational waves. recent years have seen significant progress in almost all these fields; they are presented in this review. the sun and the solar system are our reference system for abundances of elements and isotopes. many direct and indirect methods are employed to establish a refined abundance record from the time when the sun and the earth were formed. indications for nucleosynthesis in the local environment when the sun was formed are derived from meteoritic material and inclusion of radioactive atoms in deep-sea sediments. spectroscopy at many wavelengths and the neutrino flux from the hydrogen fusion processes in the sun have established a refined model of how the nuclear energy production shapes stars. models are required to explore nuclear fusion of heavier elements. these stellar evolution calculations have been confirmed by observations of nucleosynthesis products in the ejecta of stars and supernovae, as captured by stardust grains and by characteristic lines in spectra seen from these objects. one of the successes has been to directly observe γ rays from radioactive material synthesised in stellar explosions, which fully support the astrophysical models. another has been the observation of radioactive afterglow and characteristic heavy-element spectrum from a neutron-star merger, confirming the neutron rich environments encountered in such rare explosions. the ejecta material captured by earth over millions of years in sediments and identified through characteristic radio-isotopes suggests that nearby nucleosynthesis occurred in recent history, with further indications for sites of specific nucleosynthesis. together with stardust and diffuse γ rays from radioactive ejecta, these help to piece together how cosmic materials are transported in interstellar space and re-cycled into and between generations of stars. our description of cosmic compositional evolution needs such observational support, as it rests on several assumptions that appear challenged by recent recognition of violent events being common during evolution of a galaxy. this overview presents the flow of cosmic matter and the various sites of nucleosynthesis, as understood from combining many techniques and observations, towards the current knowledge of how the universe is enriched with elements. | cosmic nucleosynthesis: a multi-messenger challenge |
the nearby radio galaxy centaurus a belongs to a class of active galaxies that are luminous at radio wavelengths. most show collimated relativistic outflows known as jets, which extend over hundreds of thousands of parsecs for the most powerful sources. accretion of matter onto the central supermassive black hole is believed to fuel these jets and power their emission1. synchrotron radiation from relativistic electrons causes the radio emission, and it has been suggested that the x-ray emission from centaurus a also originates in electron synchrotron processes2-4. another possible explanation is inverse compton scattering with cosmic microwave background (cmb) soft photons5-7. synchrotron radiation needs ultrarelativistic electrons (about 50 teraelectronvolts) and, given their short cooling times, requires some continuous re-acceleration mechanism8. inverse compton scattering, on the other hand, does not require very energetic electrons, but the jets must stay highly relativistic on large scales (exceeding 1 megaparsec). some recent evidence disfavours inverse compton-cmb models9-12, although other work seems to be compatible with them13,14. in principle, the detection of extended γ-ray emission, which directly probes the presence of ultrarelativistic electrons, could distinguish between these options. at gigaelectronvolt energies there is also an unusual spectral hardening15,16 in centaurus a that has not yet been explained. here we report observations of centaurus a at teraelectronvolt energies that resolve its large-scale jet. we interpret the data as evidence for the acceleration of ultrarelativistic electrons in the jet, and favour the synchrotron explanation for the x-rays. given that this jet is not exceptional in terms of power, length or speed, it is possible that ultrarelativistic electrons are commonplace in the large-scale jets of radio-loud active galaxies. | resolving acceleration to very high energies along the jet of centaurus a |
dwarf spheroidal galaxies (dsphs) are promising targets for the indirect detection of dark matter through gamma-ray emission due to their proximity, lack of astrophysical backgrounds and high dark matter density. they are often used to place restrictive bounds on the dark matter annihilation cross section. in this paper, we analyze six years of fermi-lat gamma-ray data from 19 dsphs that are satellites of the milky way, and derive from a stacked analysis of 15 dsphs, robust 95% confidence level lower limits on the dark matter lifetime for several decay channels and dark matter masses between ∼1 gev and 10 tev. our findings are based on a bin-by-bin maximum likelihood analysis treating the j -factor as a nuisance parameter using the pass 8 event class. our constraints from this ensemble are among the most stringent and solid in the literature, and competitive with existing ones coming from the extragalactic gamma-ray background, galaxy clusters, ams-02 cosmic ray data, super-k and icecube neutrino data, while rather insensitive to systematic uncertainties. in particular, among gamma-ray searches, we improve existing limits for dark matter decaying into b ¯b (μ+μ-) for dark matter masses below ∼30 (200 ) gev , demonstrating that dsphs are compelling targets for constraining dark matter decay lifetimes. | new limits on the dark matter lifetime from dwarf spheroidal galaxies using fermi-lat |
the existence of a large population of compton thick (ct; nh > 1024 cm-2) active galactic nuclei (agn) is a key ingredient of most cosmic x-ray background synthesis models. however, direct identification of these sources, especially at high redshift, is difficult due to flux suppression and complex spectral shape produced by ct obscuration. we explored the chandra cosmological evolution survey (cosmos) legacy point source catalogue, comprising 1855 sources to select, via x-ray spectroscopy, a large sample of ct candidates at high redshift. adopting a physical model to reproduce the toroidal absorber and a monte-carlo sampling method, we selected 67 individual sources with > 5 per cent probability of being ct, in the redshift range 0.04 ≲ z ≲ 3.5. the sum of the probabilities above nh > 1024 cm-2 gives a total of 41.9 effective ct, corrected for classification bias. we derive number counts in the 2-10 kev band in three redshift bins. the observed log n-log s is consistent with an increase of the intrinsic ct fraction (fct) from ∼0.30 to ∼0.55 from low to high redshift. when rescaled to a common luminosity (log(lx/ erg s-1) = 44.5), we find an increase from fct = 0.19_{-0.06}^{+0.07} to 0.30_{-0.08}^{+0.10} and fct = 0.49_{-0.11}^{+0.12} from low to high z. this evolution can be parametrized as fct = 0.11_{-0.04}^{+0.05}(1+z)^{1.11± 0.13}. thanks to hubble space telescope-advanced camera for surveys deep imaging, we find that the fraction of ct agn in mergers/interacting systems increases with luminosity and redshift and is significantly higher than for non-ct agn hosts. | the chandra cosmos legacy survey: compton thick agn at high redshift |
theories of a pre-rna world suggest that glycolonitrile (hoch2cn) is a key species in the process of ribonucleotide assembly, which is considered as a molecular precursor of nucleic acids. in this letter, we report the first detection of this pre-biotic molecule in the interstellar medium by using alma data obtained at frequencies between 86.5 ghz and 266.5 ghz toward the solar-type protostar iras16293-2422 b. a total of 15 unblended transitions of hoch2cn were identified. our analysis indicates the presence of a cold (t_{ex} = 24 ± 8 k) and a warm (t_{ex} = 158 ± 38 k) component meaning that this molecule is present in both the inner hot corino and the outer cold envelope of iras16293 b. the relative abundance with respect to h2 is (6.5 ± 0.6) × 10-11 and ≥(6 ± 2) × 10-10 for the warm and cold components, respectively. our chemical modelling seems to underproduce the observed abundance for both the warm and cold component under various values of the cosmic ray ionization rate (ζ). key gas phase routes for the formation of this molecule might be missing in our chemical network. | first detection of the pre-biotic molecule glycolonitrile (hoch2cn) in the interstellar medium |
we present the first full-sky analysis of the cosmic ray arrival direction distribution with data collected by the high-altitude water cherenkov and icecube observatories in the northern and southern hemispheres at the same median primary particle energy of 10 tev. the combined sky map and angular power spectrum largely eliminate biases that result from partial sky coverage and present a key to probe into the propagation properties of tev cosmic rays through our local interstellar medium and the interaction between the interstellar and heliospheric magnetic fields. from the map, we determine the horizontal dipole components of the anisotropy δ 0h= 9.16 × 10-4 and δ 6h= 7.25 × 10-4 (±0.04 × 10-4). in addition, we infer the direction (229.°2 ± 3.°5 r.a., 11.°4 ± 3.°0 decl.) of the interstellar magnetic field from the boundary between large-scale excess and deficit regions from which we estimate the missing corresponding vertical dipole component of the large-scale anisotropy to be {δ }n∼ -{3.97}-2.0+1.0× {10}-4. | all-sky measurement of the anisotropy of cosmic rays at 10 tev and mapping of the local interstellar magnetic field |
the large hadron collider forward (lhcf) experiment is designed to use the lhc to verify the hadronic-interaction models used in cosmic-ray physics. forward baryon production is one of the crucial points to understand the development of cosmic-ray showers. we report the neutron-energy spectra for lhc √{ s} = 7 tev proton-proton collisions with the pseudo-rapidity η ranging from 8.81 to 8.99, from 8.99 to 9.22, and from 10.76 to infinity. the measured energy spectra obtained from the two independent calorimeters of arm1 and arm2 show the same characteristic feature before unfolding the detector responses. we unfolded the measured spectra by using the multidimensional unfolding method based on bayesian theory, and the unfolded spectra were compared with current hadronic-interaction models. the qgsjet ii-03 model predicts a high neutron production rate at the highest pseudo-rapidity range similar to our results, and the dpmjet 3.04 model describes our results well at the lower pseudo-rapidity ranges. however, no model perfectly explains the experimental results over the entire pseudo-rapidity range. the experimental data indicate a more abundant neutron production rate relative to the photon production than any model predictions studied here. | measurement of very forward neutron energy spectra for 7 tev proton-proton collisions at the large hadron collider |
atmospheric ionization produced by cosmic rays has been suspected to influence aerosols and clouds, but its actual importance has been questioned. if changes in atmospheric ionization have a substantial impact on clouds, one would expect to observe significant responses in earth's energy budget. here it is shown that the average of the five strongest week-long decreases in atmospheric ionization coincides with changes in the average net radiative balance of 1.7 w/m2? (median value: 1.2 w/m2?) using ceres satellite observations. simultaneous satellite observations of clouds show that these variations are mainly caused by changes in the short-wave radiation of low liquid clouds along with small changes in the long-wave radiation, and are almost exclusively located over the pristine areas of the oceans. these observed radiation and cloud changes are consistent with a link in which atmospheric ionization modulates aerosol's formation and growth, which survive to cloud condensation nuclei and ultimately affect cloud formation and thereby temporarily the radiative balance of earth. | atmospheric ionization and cloud radiative forcing |
compact binaries such as double neutron stars or a neutron star paired with a black hole, are strong sources of gravitational waves during coalescence and also the likely progenitors of various electromagnetic phenomena, notably short-duration gamma-ray bursts (sgrbs), and kilonovae. in this work, we generate populations of synthetic binaries and place them in galaxies from the large-scale hydrodynamical galaxy evolution simulation, eagle. with our zelda code, binaries are seeded in proportion to star formation rate, and we follow their evolution to merger using both the bpass and cosmic binary stellar evolution codes. we track their dynamical evolution within their host galaxy potential, to estimate the galactocentric distance at the time of the merger. finally, we apply observational selection criteria to allow comparison of this model population with the legacy sample of sgrbs. we find a reasonable agreement with the redshift distribution (peaking at 0.5 < z < 1), host morphologies, and projected galactocentric offsets (modal impact parameter ≲10 kpc). depending on the binary simulation used, we predict $\sim 16\!-\!35{{\ \rm per\ cent}}$ of sgrb events would appear 'host-less', i.e. sources that merge with high impact parameters or have hosts fainter than the detection limit (h > 26). | exploring compact binary merger host galaxies and environments with zelda |
the astri (astrofisica con specchi a tecnologia replicante italiana) project led by the italian national institute for astrophysics (inaf) is developing and will deploy at the observatorio del teide a mini-array (astri mini-array) composed of nine telescopes similar to the small-size dual-mirror schwarzschild-couder telescope (astri-horn) currently operating on the slopes of mt. etna in sicily. the astri mini-array will surpass the current cherenkov telescope array differential sensitivity above a few tera-electronvolt (tev), extending the energy band well above hundreds of tev. this will allow us to explore a new window of the electromagnetic spectrum, by convolving the sensitivity performance with excellent angular and energy resolution figures. in this paper we describe the core science that we will address during the first four years of operation, providing examples of the breakthrough results that we will obtain when dealing with current open questions, such as the acceleration of cosmic rays, cosmology and fundamental physics and the new window, for the tev energy band, of the time-domain astrophysics. | astri mini-array core science at the observatorio del teide |
fluorine is one of the most interesting elements in nuclear astrophysics, where the f 19 (p ,α )o 16 reaction is of crucial importance for galactic f 19 abundances and cno cycle loss in first generation population iii stars. as a day-one campaign at the jinping underground nuclear astrophysics experimental facility, we report direct measurements of the essential f 19 (p ,α γ )o 16 reaction channel. the γ -ray yields were measured over ec .m .=72.4 - 344 kev , covering the gamow window; our energy of 72.4 kev is unprecedentedly low, reported here for the first time. the experiment was performed under the extremely low cosmic-ray-induced background environment of the china jinping underground laboratory, one of the deepest underground laboratories in the world. the present low-energy s factors deviate significantly from previous theoretical predictions, and the uncertainties are significantly reduced. the thermonuclear f 19 (p ,α γ )o 16 reaction rate has been determined directly at the relevant astrophysical energies. | direct measurement of the astrophysical f 19 (p ,α γ )o 16 reaction in the deepest operational underground laboratory |
we report calculations of cosmic-ray proton, nuclei, antiproton, electron and positron energy spectra within a "two-halo model" of diffusive transport. the two halos represent a simple, physically consistent generalization of the standard diffusion models, which assume a unique type of diffusion for cosmic rays in the whole galactic halo. we believe instead that cosmic rays may experience a smaller energy dependence of diffusion when they are in proximity of the galactic disk. our scenario is supported by recent observations of cosmic ray protons, nuclei, anisotropy, and gamma-rays. we predict remarkably hard antiparticle spectra at high energy. in particular, at e ≳10 gev , the antiproton/proton ratio is expected to flatten, while the positron fraction is found to increase with energy. we discuss the implications for cosmic-ray physics and dark matter searches via antimatter. | cosmic-ray protons, nuclei, electrons, and antiparticles under a two-halo scenario of diffusive propagation |
the role of the sun in climate change is hotly debated. some studies suggest its impact is significant, while others suggest it is minimal. the intergovernmental panel on climate change (ipcc) supports the latter view and suggests that nearly 100% of the observed surface warming from 1850-1900 to 2020 is due to anthropogenic emissions. however, the ipcc's conclusions are based solely on computer simulations made with global climate models (gcms) forced with a total solar irradiance (tsi) record showing a low multi-decadal and secular variability. the same models also assume that the sun affects the climate system only through radiative forcing - such as tsi - even though the climate could also be affected by other solar processes. in this paper i propose three "balanced" multi-proxy models of total solar activity (tsa) that consider all main solar proxies proposed in scientific literature. their optimal signature on global and sea surface temperature records is assessed together with those produced by the anthropogenic and volcanic radiative forcing functions adopted by the cmip6 gcms. this is done by using a basic energy balance model calibrated with a differential multi-linear regression methodology, which allows the climate system to respond to the solar input differently than to radiative forcings alone, and to evaluate the climate's characteristic time-response as well. the proposed methodology reproduces the results of the cmip6 gcms when their original forcing functions are applied under similar physical conditions, indicating that, in such a scenario, the likely range of the equilibrium climate sensitivity (ecs) could be 1.4 °c to 2.8 °c, with a mean of 2.1 °c (using the hadcrut5 temperature record), which is compatible with the low-ecs cmip6 gcm group. however, if the proposed solar records are used as tsa proxies and the climatic sensitivity to them is allowed to differ from the climatic sensitivity to radiative forcings, a much greater solar impact on climate change is found, along with a significantly reduced radiative effect. in this case, the ecs is found to be 0.9-1.8 °c, with a mean of around 1.3 °c. lower ecs ranges (up to 20%) are found using hadsst4, hadcrut4, and hadsst3. the result also suggests that at least about 80% of the solar influence on the climate may not be induced by tsi forcing alone, but rather by other sun-climate processes (e.g., by a solar magnetic modulation of cosmic ray and other particle fluxes, and/or others), which must be thoroughly investigated and physically understood before trustworthy gcms can be created. this result explains why empirical studies often found that the solar contribution to climate changes throughout the holocene has been significant, whereas gcm-based studies, which only adopt radiative forcings, suggest that the sun plays a relatively modest role. | empirical assessment of the role of the sun in climate change using balanced multi-proxy solar records |
cosmogenic exposure dating of glacial boulders is commonly used to estimate the timing of past glaciations because the method enables direct dating of the duration a boulder has been exposed to cosmic rays. for successful dating, the boulders must have been fully shielded from cosmic rays prior to deposition and continuously exposed to cosmic rays ever since. a common assumption is that boulder height (the distance between the top of the boulder and the surrounding surface) is important, and that tall boulders are more likely to have been continuously exposed to cosmic rays than short boulders and therefore yield more accurate exposure ages. here we test this assumption based on exposure age clustering for groups of glacial boulders (and single cobbles) 10be exposure ages that have recorded boulder heights (3741 boulders; 579 boulder groups with ≥3 boulders). of the full set of boulder groups with ≥3 boulders, 21% fulfill a reduced chi square criterion (χr2 < 2) for well-clustered exposure ages. for boulder groups containing only tall boulders, the fraction of well-clustered exposure age groups is consistently larger. moreover, this fraction of well-clustered exposure age groups increases with the minimum boulder height in each group. this result confirms the common assumption that tall boulders are generally better targets for cosmogenic exposure dating compared to short boulders. whereas the tall boulder groups have a significantly larger fraction of well-clustered exposure age groups, there is nonetheless a dominant fraction (>50%) of the boulder groups with scattered exposure ages, highlighting the problem with prior and incomplete exposure for cosmogenic dating of glacial boulders. | boulder height - exposure age relationships from a global glacial 10be compilation |
ultra-high-energy photons with energies exceeding 1017 ev offer a wealth of connections to different aspects of cosmic-ray astrophysics as well as to gamma-ray and neutrino astronomy. the recent observations of photons with energies in the 1015 ev range further motivate searches for even higher-energy photons. in this paper, we present a search for photons with energies exceeding 2 × 1017 ev using about 5.5 yr of hybrid data from the low-energy extensions of the pierre auger observatory. the upper limits on the integral photon flux derived here are the most stringent ones to date in the energy region between 1017 and 1018 ev. | a search for photons with energies above 2 × 1017 ev using hybrid data from the low-energy extensions of the pierre auger observatory |
phosphorus (p) is one of the essential elements for life due to its central role in biochemical processes. recent searches have shown that p-bearing molecules (in particular pn and po) are present in star-forming regions, although their formation routes remain poorly understood. in this letter, we report observations of pn and po towards seven molecular clouds located in the galactic center, which are characterized by different types of chemistry. pn is detected in five out of seven sources, whose chemistry is thought to be shock-dominated. the two sources with pn non-detections correspond to clouds exposed to intense uv/x-rays/cosmic ray (cr) radiation. po is detected only towards the cloud g+0.693-0.03, with a po/pn abundance ratio of ∼1.5. we conclude that p-bearing molecules likely form in shocked gas as a result of dust grain sputtering, while are destroyed by intense uv/x-ray/cr radiation. | phosphorus-bearing molecules in the galactic center |
a number of merging galaxy clusters show the presence of shocks and cold fronts, i.e. sharp discontinuities in surface brightness and temperature. the observation of these features requires an x-ray telescope with high spatial resolution like chandra, and allows to study important aspects concerning the physics of the intracluster medium (icm), such as its thermal conduction and viscosity, as well as to provide information on the physical conditions leading to the acceleration of cosmic rays and magnetic field amplification in the cluster environment. in this work we search for new discontinuities in 15 merging and massive clusters observed with chandra by using different imaging and spectral techniques of x-ray observations. our analysis led to the discovery of 22 edges: six shocks, eight cold fronts, and eight with uncertain origin. all the six shocks detected have m< 2 derived from density and temperature jumps. this work contributed to increase the number of discontinuities detected in clusters and shows the potential of combining diverse approaches aimed to identify edges in the icm. a radio follow-up of the shocks discovered in this paper will be useful to study the connection between weak shocks and radio relics. | shocks and cold fronts in merging and massive galaxy clusters: new detections with chandra |
the luminosity densities of high-energy cosmic radiations are studied to find connections among the various components, including high-energy neutrinos measured with icecube and gamma rays with the fermi satellite. matching the cosmic-ray energy generation rate density in a gev-tev range estimated for milky way with the ultra-high-energy component requires a power-law index of the spectrum scr≈2.1 - 2.2 , somewhat harder than scr≈2.3 - 2.4 for the local index derived from the ams-02 experiment. the soft gev-tev cosmic-ray spectrum extrapolated to higher energies can be compatible with pev cosmic rays inferred from neutrino measurements, but overshoots the cr luminosity density to explain gev-tev gamma rays. the extrapolation from ultrahigh energies with a hard spectrum, on the other hand, can be consistent with both neutrinos and gamma rays. these point towards either reacceleration of galactic cosmic rays or the presence of extragalactic sources with a hard spectrum. we discuss possible cosmic-ray sources that can be added. | energetics of high-energy cosmic radiations |
the cosmic infrared background (cib) contains emissions accumulated over the entire history of the universe, including from objects inaccessible to individual telescopic studies. the near-infrared (∼1 -10 μ m ) part of the cib, and its fluctuations, reflects emissions from nucleosynthetic sources and gravitationally accreting black holes. if known galaxies are removed to sufficient depths the source-subtracted cib fluctuations at near-infrared can reveal sources present in the first stars era and possibly new stellar populations at more recent times. this review discusses the recent progress in this newly emerging field which identified, with new data and methodology, significant source-subtracted cib fluctuations substantially in excess of what can be produced by remaining known galaxies. the cib fluctuations further appear coherent with unresolved cosmic x-ray background indicating a very high fraction of black holes among the new sources producing the cib fluctuations. these observations have led to intensive theoretical efforts to explain the measurements and their properties. while current experimental configurations have limitations in decisively probing these theories, their potentially remarkable implications will be tested in the upcoming cib measurements with the european space agency's euclid dark energy mission. the goals and methodologies of librae (looking at infrared background radiation with euclid), a national aeronautics and space administration (nasa) selected project for cib science with euclid, which has the potential for transforming the field into a new area of precision cosmology, are described. | looking at cosmic near-infrared background radiation anisotropies |
conventional lore from tremaine and gunn excludes fermionic dark matter lighter than a few hundred ev, based on the pauli exclusion principle. we highlight a simple way of evading this bound with a large number of species that leads to numerous nontrivial consequences. in this scenario there are many distinct species of fermions with quasidegenerate masses and no couplings to the standard model. nonetheless, gravitational interactions lead to constraints from measurements at the lhc, of cosmic rays, of supernovae, and of black hole spins and lifetimes. we find that the lhc constrains the number of distinct species, bosons or fermions lighter than ∼500 gev , to be n ≲1062. this, in particular, implies that roughly degenerate fermionic dark matter must be heavier than ∼10-14 ev , which thus relaxes the tremaine-gunn bound by ∼16 orders of magnitude. slightly weaker constraints applying to masses up to ∼100 tev exist from cosmic ray measurements while various constraints on masses ≲10-10 ev apply from black hole observations. we consider a variety of phenomenological bounds on the number of species of particles. finally, we note that there exist theoretical considerations regarding quantum gravity which could impose more severe constraints that may limit the number of physical states to n ≲1032. | ultralight fermionic dark matter |
we study the acceleration of cosmic rays by collisionless structure formation shocks with enzo grid simulations. data from the fermi satellite enable the use of galaxy clusters as a testbed for particle acceleration models. based on advanced cosmological simulations that include different prescriptions for gas and cosmic rays physics, we use the predicted γ-ray emission to constrain the shock acceleration efficiency. we infer that the efficiency must be on average ≤10-3 for cosmic shocks, particularly for the m ∼ 2-5 merger shocks that are mostly responsible for the thermalization of the intracluster medium (icm). these results emerge, both, from non-radiative and radiative runs including feedback from active galactic nuclei, as well as from zoomed resimulations of a cluster resembling macsj1752.0+0440. the limit on the acceleration efficiency we report is lower than what has been assumed in the literature so far. combined with the information from radio emission in clusters, it appears that a revision of the present understanding of shock acceleration in the icm is unavoidable. | constraining the efficiency of cosmic ray acceleration by cluster shocks |
with the breakthrough in pev gamma-ray astronomy brought about by the lhaaso experiment, the high-energy sky is becoming richer. recently, the lhaaso collaboration reported the observation of a gamma-ray diffuse emission with energy up to the pev level from both the inner and outer galactic plane. in these spectra, there is a bump that is hard to explain using the conventional cosmic-ray transport scenarios. therefore, we introduce two extra components corresponding to unresolved sources with exponential-cutoff-power-law (ecpl) spectral shape—one with an index of 2.4 and cutoff energy of 20 tev, and another with an index of 2.3 and cutoff energy of 2 pev. with our constructed model, we simulate the galactic diffuse neutrino flux and find that our results are in full agreement with the latest icecube galactic plane search. we estimate the galactic neutrino contributes ∼9 % of astrophysical neutrinos at 20 tev. in the high-energy regime, as expected, most of the neutrinos observed by icecube should be from extragalactic environments. | multimessenger study of the galactic diffuse emission with lhaaso and icecube observations |
supernova remnants (snrs) are believed to produce the majority of galactic cosmic rays (crs). snrs harbor non-relativistic collisionless shocks responsible for the acceleration of crs via diffusive shock acceleration (dsa), in which particles gain their energy via repeated interactions with the shock front. since the dsa theory involves pre-existing mildly energetic particles, a means of pre-acceleration is required, especially for electrons. electron injection remains one of the most troublesome and still unresolved issues and our physical understanding of it is essential to fully comprehend the physics of snrs. to study any electron-scale phenomena responsible for pre-acceleration, we require a method capable of resolving these small kinetic scales and particle-in-cell simulations that fulfill this criterion. here, i report on the latest achievements made by utilizing kinetic simulations of non-relativistic high mach number shocks. i discuss how the physics of snr shocks depends on the shock parameters (e.g. the shock obliquity, mach number, the ion-to-electron mass ratio) as well as the processes responsible for the electron heating and acceleration. | electron acceleration in supernova remnants |
we present a comprehensive study about the phenomenological implications of the theory describing galactic cosmic ray scattering on to magnetosonic and alfvénic fluctuations in the gev-pev domain. we compute a set of diffusion coefficients from first principles, for different values of the alfvénic mach number and other relevant parameters associated with both the galactic halo and the extended disc, taking into account the different damping mechanisms of turbulent fluctuations acting in these environments. we confirm that the scattering rate associated with alfvénic turbulence is highly suppressed if the anisotropy of the cascade is taken into account. on the other hand, we highlight that magnetosonic modes play a dominant role in galactic confinement of cosmic rays up to pev energies. we implement the diffusion coefficients in the numerical framework of the dragon code, and simulate the equilibrium spectrum of different primary and secondary cosmic ray species. we show that, for reasonable choices of the parameters under consideration, all primary and secondary fluxes at high energy (above a rigidity of $\simeq 200 \, \mathrm{gv}$ ) are correctly reproduced within our framework, in both normalization and slope. | the theory of cosmic ray scattering on pre-existing mhd modes meets data |
cosmic dawn (cd) and epoch of reionization (eor) are epochs of the universe which host invaluable information about the cosmology and astrophysics of x-ray heating and hydrogen reionization. radio interferometric observations of the 21-cm line at high redshifts have the potential to revolutionize our understanding of the universe during this time. however, modelling the evolution of these epochs is particularly challenging due to the complex interplay of many physical processes. this makes it difficult to perform the conventional statistical analysis using the likelihood-based markov-chain monte carlo (mcmc) methods, which scales poorly with the dimensionality of the parameter space. in this paper, we show how the simulation-based inference through marginal neural ratio estimation (mnre) provides a step towards evading these issues. we use 21cmfast to model the 21-cm power spectrum during cd-eor with a six-dimensional parameter space. with the expected thermal noise from the square kilometre array, we are able to accurately recover the posterior distribution for the parameters of our model at a significantly lower computational cost than the conventional likelihood-based methods. we further show how the same training data set can be utilized to investigate the sensitivity of the model parameters over different redshifts. our results support that such efficient and scalable inference techniques enable us to significantly extend the modelling complexity beyond what is currently achievable with conventional mcmc methods. | constraining the x-ray heating and reionization using 21-cm power spectra with marginal neural ratio estimation |
observations of the 21 cm line from neutral hydrogen indicate that an epoch of heating (eoh) might have preceded the later epoch of reionization. here we study the effects on the ionization state and the thermal history of the intergalactic medium (igm) during the eoh induced by different assumptions on ionizing sources in the high-redshift universe: (i) stars; (ii) x-ray binaries (xrbs); (iii) thermal bremsstrahlung of the hot interstellar medium (ism); and (iv) accreting nuclear black holes (bhs). to this aim, we post-process outputs from the (100 h-1 comoving mpc)3 hydrodynamical simulation massiveblack-ii with the cosmological 3d radiative transfer code crash, which follows the propagation of ultraviolet and x-ray photons, computing the thermal and ionization state of hydrogen and helium through the eoh. we find that stars determine the fully ionized morphology of the igm, while the spectrally hard xrbs pave way for efficient subsequent heating and ionization by the spectrally softer ism. with the seeding prescription in massiveblack-ii, bhs do not contribute significantly to either ionization or heating. with only stars, most of the igm remains in a cold state (with a median t = 11 k at z = 10), however, the presence of more energetic sources raises the temperature of regions around the brightest and more clustered sources above that of the cosmic microwave background, opening the possibility to observing the 21 cm signal in emission. | the epoch of cosmic heating by early sources of x-rays |
self-regulated feedback by active galactic nuclei (agns) appears to be critical in balancing radiative cooling of the low-entropy gas at the centres of galaxy clusters and in regulating star formation in central galaxies. in a companion paper, we found steady-state solutions of the hydrodynamic equations that are coupled to the cosmic ray (cr) energy equation for a large cluster sample. in those solutions, radiative cooling in the central region is balanced by streaming crs through the generation and dissipation of resonantly generated alfvén waves and by thermal conduction at large radii. here, we demonstrate that the predicted non-thermal emission resulting from hadronic cr interactions in the intracluster medium exceeds observational radio (and gamma-ray) data in a subsample of clusters that host radio mini haloes (rmhs). in contrast, the predicted non-thermal emission is well below observational data in cooling galaxy clusters without rmhs. these are characterized by exceptionally large agn radio fluxes, indicating high cr yields and associated cr heating rates. we suggest a self-regulation cycle of agn feedback in which non-rmh clusters are heated by streaming crs homogeneously throughout the central cooling region. we predict radio micro haloes surrounding the agns of these cr-heated clusters in which the primary emission may predominate the hadronically generated emission. once the cr population has streamed sufficiently far and lost enough energy, the cooling rate increases, which explains the increased star formation rates in clusters hosting rmhs. those could be powered hadronically by crs that have previously heated the cluster core. | cosmic ray heating in cool core clusters - ii. self-regulation cycle and non-thermal emission |
massive black holes at the centers of galaxies can launch powerful wide-angle winds that, if sustained over time, can unbind the gas from the stellar bulges of galaxies. these winds may be responsible for the observed scaling relation between the masses of the central black holes and the velocity dispersion of stars in galactic bulges. propagating through the galaxy, the wind should interact with the interstellar medium creating a strong shock, similar to those observed in supernovae explosions, which is able to accelerate charged particles to high energies. in this work we use data from the fermi large area telescope to search for the γ-ray emission from galaxies with an ultrafast outflow (ufo): a fast (v ~ 0.1 c), highly ionized outflow, detected in absorption at hard x-rays in several nearby active galactic nuclei (agn). adopting a sensitive stacking analysis we are able to detect the average γ-ray emission from these galaxies and exclude that it is due to processes other than ufos. moreover, our analysis shows that the γ-ray luminosity scales with the agn bolometric luminosity and that these outflows transfer ~0.04% of their mechanical power to γ-rays. interpreting the observed γ-ray emission as produced by cosmic rays (crs) accelerated at the shock front, we find that the γ-ray emission may attest to the onset of the wind-host interaction and that these outflows can energize charged particles up to the transition region between galactic and extragalactic crs. | gamma rays from fast black-hole winds |
aims: we examine the x-ray, optical, and radio properties of the member clusters of a new supercluster discovered during the srg/erosita performance verification phase.methods: we analyzed the 140 deg2 erosita final equatorial depth survey (efeds) field observed during the performance verification phase to a nominal depth of about 2.3 ks. in this field, we detect a previously unknown supercluster consisting of a chain of eight galaxy clusters at z ~ 0.36. the redshifts of these members were determined through hyper suprime-cam photometric measurements. we examined the x-ray morphological and dynamical properties, gas, and total mass out to r500 of the members and compare these with the same properties of the general population of clusters detected in the efeds field. we further investigated the gas in the bridge region between the cluster members for a potential whim detection. we also used radio follow-up observations with lofar and ugmrt to search for diffuse emission and constrain the dynamic state of the system.results: we do not find significant differences between the morphological parameters and properties of the intra-cluster medium of the clusters embedded in this large-scale filament and those of the efeds clusters. we also provide upper limits on the electron number density and mass of the warm-hot intergalactic medium as provided by the erosita data. these limits are consistent with previously reported values for the detections in the vicinity of clusters of galaxies. in lofar and ugmrt follow-up observations of the northern part of this supercluster, we find two new radio relics and a radio halo that are the result of major merger activity in the system.conclusions: these early results show the potential of erosita to probe large-scale structures such as superclusters and the properties of their members. our forecasts show that we will be able to detect about 450 superclusters, with approximately 3000 member clusters located in the erosita_de region at the final erosita all-sky survey depth, enabling statistical studies of the properties of superclusters and their constituents embedded in the cosmic web. | discovery of a supercluster in the erosita final equatorial depth survey: x-ray properties, radio halo, and double relics |
cosmic ray (cr) protons are an important component in many astrophysical systems. processes like cr injection, cooling, adiabatic changes as well as active cr transport through the medium strongly modify the cr momentum distribution and have to be taken into account in hydrodynamical simulations. we present an efficient novel numerical scheme to accurately compute the evolution of the particle distribution function by solving the fokker-planck equation with a low number of spectral bins (10-20), which is required to include a full spectrum for every computational fluid element. the distribution function is represented by piecewise power laws and is not forced to be continuous, which enables an optimal representation of the spectrum. the fokker-planck equation is solved with a two-moment approach evolving the cr number and energy density. the low numerical diffusion of the scheme reduces the numerical errors by orders of magnitude in comparison to classical schemes with piecewise constant spectral representations. with this method not only the spectral evolution of crs can be computed accurately in magnetohydrodynamic simulations but also their dynamical impact as well as cr ionization. this allows for more accurate models for astrophysical plasmas, like the interstellar medium, and direct comparisons with observations. | spectrally resolved cosmic ray hydrodynamics - i. spectral scheme |
based on the standard gaisser's formula, a modified parametrization for the sea-level cosmic-ray muon flux is introduced. the modification is verified against experimental results. the average vertical cosmic-ray muon intensity as a function of depth of standard rock is simulated using the modified formula as input to the music code. the calculated muon intensities is consistent with the experimental measurements. | a parametrization of the cosmic-ray muon flux at sea-level |
we observed three γ-ray bursts related to thunderclouds in winter using the prototype of anti-neutrino detector panda made of 360-kg plastic scintillator deployed at ohi power station at the coastal area of the japan sea. the maximum rate of the events which deposited the energy higher than 3 mev was (5.5 ± 0.1) ×102 /s. monte carlo simulation showed that electrons with approximately monochromatic energy falling downwards from altitudes of order 100 m roughly produced the observed total energy spectra of the bursts. it is supposed that secondary cosmic-ray electrons, which act as seed, were accelerated in electric field of thunderclouds and multiplied by relativistic runaway electron avalanche. we actually found that the γ-rays of the bursts entered into the detector from the direction close to the zenith. the direction stayed constant during the burst within the detector resolution. in addition, taking advantage of the delayed coincidence detection of the detector, we found neutron events in one of the bursts at the maximum rate of ∼ 14 ± 5 /s. | observation of gamma ray bursts at ground level under the thunderclouds |
we present a study of γ-ray emission from the core-collapse supernova remnant cas a in the energy range from 0.1 gev to 10 tev. we used 65 hr of the very energetic radiation imaging telescope array system (veritas) data to cover 200 gev-10 tev, and 10.8 yr of fermi-large area telescope (lat) data to cover 0.1-500 gev. the spectral analysis of fermi-lat data shows a significant spectral curvature around 1.3 ± 0.4stat gev that is consistent with the expected spectrum from pion decay. above this energy, the joint spectrum from fermi-lat and veritas deviates significantly from a simple power law, and it is best described by a power law with a spectral index of 2.17 ± 0.02stat and a cutoff energy of 2.3 ± 0.5stat tev. these results, along with radio, x-ray, and γ-ray data, are interpreted in the context of leptonic and hadronic models. assuming a one-zone model, we exclude a purely leptonic scenario and conclude that proton acceleration up to at least 6 tev is required to explain the observed γ-ray spectrum. from modeling of the entire multiwavelength spectrum, a minimum magnetic field inside the remnant of bmin ≈ 150 μg is deduced. | evidence for proton acceleration up to tev energies based on veritas and fermi-lat observations of the cas a snr |
dark matter (dm) direct detection experiments have been setting strong limits on the dm-nucleon scattering cross section at the dm mass above a few gev, but leave large parameter space unexplored in the low mass region. dm is likely to be scattered and boosted by relativistic cosmic rays in the expanding universe if it can generate nuclear recoils in direct detection experiments to offer observable signals. since low energy threshold detectors using germanium have provided good constraints on ordinary halo gev-scale dm, it is necessary to re-analyze 102.8 kg$\times$day data in the cdex-10 experiment assuming that dm is boosted by cosmic rays. for the dm mass range 1 kev $<m_\chi <$ 1 mev and the effective distance within 1 kpc, we reach an almost flat floor limit at $8.32\times10^{-30}$ cm$^2$ on spin-independent dm-nucleon scattering cross section at a 90\% confidence level. the cdex-10 result is able to close the gap unambiguously in the parameter space between miniboone and xenon1t constraints which was partially hindered by the earth attenuation effect. we also quantitatively calculate expected neutrino floor on searching for crbdm in future direct detection experiments using germanium. | constraints on cosmic-ray boosted dm in cdex-10 |
imaging of nuclear gamma-ray lines in the 1-10 mev range is far from being established in both medical and physical applications. in proton therapy, 4.4 mev gamma rays are emitted from the excited nucleus of either 12c* or 11b* and are considered good indicators of dose delivery and/or range verification. further, in gamma-ray astronomy, 4.4 mev gamma rays are produced by cosmic ray interactions in the interstellar medium, and can thus be used to probe nucleothynthesis in the universe. in this paper, we present a high-precision image of 4.4 mev gamma rays taken by newly developed 3-d position sensitive compton camera (3d-pscc). to mimic the situation in proton therapy, we first irradiated water, pmma and ca(oh)2 with a 70 mev proton beam, then we identified various nuclear lines with the hpge detector. the 4.4 mev gamma rays constitute a broad peak, including single and double escape peaks. thus, by setting an energy window of 3d-pscc from 3 to 5 mev, we show that a gamma ray image sharply concentrates near the bragg peak, as expected from the minimum energy threshold and sharp peak profile in the cross section of 12c(p,p)12c*. | precision imaging of 4.4 mev gamma rays using a 3-d position sensitive compton camera |
the systematic analysis of optical large-scale surveys has revealed a population of dwarf galaxies hosting active galactic nuclei (agn), which have been confirmed by x-ray follow-up observations. recently, the manga survey identified six dwarf galaxies that appear to have an agn that is preventing on-going star formation. it is therefore timely to study the physical properties of dwarf galaxies, in particular whether the presence of an agn can affect their evolution. using the moving mesh code arepo, we have investigated different models of agn activity, ranging from simple energy-driven spherical winds to collimated, mass-loaded, bipolar outflows in high-resolution simulations of isolated dwarf galaxies hosting an active black hole. our simulations also include a novel implementation of star formation and mechanical supernova (sn) feedback. we find that agn outflows have a small but systematic effect on the central star formation rates (sfrs) for all set-ups explored, while substantial effects on the global sfr are only obtained with strong sne and a sustained high-luminosity agn with an isotropic wind. this suggests that agn feedback in dwarf galaxies is unlikely to directly regulate their global sfrs. there is, however, a significant effect on outflow properties, which are notably enhanced by the agn to much higher outflow temperatures and velocities, in agreement with kinematic signatures from the manga survey. this indicates that agn may play an indirect role in regulating the baryon cycle in dwarf galaxies by hindering cosmic gas inflows. | fast and energetic agn-driven outflows in simulated dwarf galaxies |
we exploit the 7 ms chandra observations in the chandra deep field-south (cdf-s), the deepest x-ray survey to date, coupled with candels/goods-s data, to measure the total x-ray emission arising from 2076 galaxies at 3.5 ≤ z < 6.5. this aim is achieved by stacking the chandra data at the positions of optically selected galaxies, reaching effective exposure times of ≥109s. we detect significant (>3.7σ) x-ray emission from massive galaxies at z ≈ 4. we also report the detection of massive galaxies at z ≈ 5 at a 99.7 per cent confidence level (2.7σ), the highest significance ever obtained for x-ray emission from galaxies at such high redshifts. no significant signal is detected from galaxies at even higher redshifts. the stacking results place constraints on the bhad associated with the known high-redshift galaxy samples, as well as on the sfrd at high redshift, assuming a range of prescriptions for x-ray emission due to x- ray binaries. we find that the x-ray emission from our sample is likely dominated by processes related to star formation. our results show that low-rate mass accretion on to smbhs in individually x-ray-undetected galaxies is negligible, compared with the bhad measured for samples of x-ray detected agn, for cosmic smbh mass assembly at high redshift. we also place, for the first time, constraints on the faint-end of the agn x-ray luminosity function (loglx ∼ 42) at z > 4, with evidence for fairly flat slopes. the implications of all of these findings are discussed in the context of the evolution of the agn population at high redshift. | the deepest x-ray view of high-redshift galaxies: constraints on low-rate black hole accretion |
we consider the synchrotron emission from high-energy electrons accelerated in supernova explosions of massive population iii stars in high-redshift minihaloes of mass 10^{5-7} m_⊙. we show the resulting intensity of radio background from this process can be substantial, which could potentially explain the recently reported edges result, if not for the associated heating of the igm by cr protons, which are also produced at the same time. the trade-off between the radio background and heating is such that the 21 cm brightness temperature cannot be larger than |δt21| ∼ 0.25 k. the radio background and heating are both produced by energetic particles, although one by energetic electrons and the other by energetic protons. the two competing processes, production of radio background and heating of igm by pop iii supernovae, determine the depth of the trough in the 21 cm brightness temperature, which can be observed in future experiments and used as a test of this scenario. | radio background and igm heating due to pop iii supernova explosions |
the microboone detector utilizes a liquid argon time projection chamber (lartpc) with an 85 t active mass to study neutrino interactions along the booster neutrino beam (bnb) at fermilab. with a deployment location near ground level, the detector records many cosmic muon tracks in each beam-related detector trigger that can be misidentified as signals of interest. to reduce these cosmogenic backgrounds, we have designed and constructed a tpc-external cosmic ray tagger (crt) . this sub-system was developed by the laboratory for high energy physics (lhep), albert einstein center for fundamental physics, university of bern. the system utilizes plastic scintillation modules to provide precise time and position information for tpc-traversing particles. successful matching of tpc tracks and crt data will allow us to reduce cosmogenic background and better characterize the light collection system and lartpc data using cosmic muons. in this paper we describe the design and installation of the microboone crt system and provide an overview of a series of tests done to verify the proper operation of the system and its components during installation, commissioning, and physics data-taking. | design and construction of the microboone cosmic ray tagger system |
current-day cosmic ray (cr) propagation studies use static milky way models and fit parametrized source distributions to data. instead, we use three-dimensional magnetohydrodynamic (mhd) simulations of isolated galaxies with the moving-mesh code arepo that self-consistently accounts for hydrodynamic effects of cr protons. in post-processing, we calculate their steady-state spectra, taking into account all relevant loss processes. we show that this steady-state assumption is well justified in the disc and generally for regions that emit non-thermal radio and gamma rays. additionally, we model the spectra of primary electrons, accelerated by supernova remnants, and secondary electrons and positrons produced in hadronic cr proton interactions with the gas. we find that proton spectra above 10 gev only weakly depend on galactic radius, while they acquire a radial dependence at lower energies due to coulomb interactions. radiative losses steepen the spectra of primary cr electrons in the central galactic regions, while diffusive losses dominate in the outskirts. secondary electrons exhibit a steeper spectrum than primaries because they originate from the transported steeper cr proton spectra. consistent with voyager-1 and ams-02 data, our models (i) show a turnover of proton spectra below gev energies due to coulomb interactions so that electrons start to dominate the total particle spectra and (ii) match the shape of the positron fraction up to 10 gev. we conclude that our steady-state cr modelling in mhd cr galaxy simulations is sufficiently realistic to capture the dominant transport effects shaping their spectra, arguing for a full mhd treatment to accurately model cr transport in the future. | cosmic rays and non-thermal emission in simulated galaxies - i. electron and proton spectra compared to voyager-1 data |
measurements of the cosmic ray antiproton spectrum can be used to search for contributions from annihilating dark matter and to constrain the dark matter annihilation cross section. depending on the assumptions made regarding cosmic ray propagation in the galaxy, such constraints can be quite stringent. we revisit this topic, utilizing a set of propagation models fit to the cosmic ray boron, carbon, oxygen and beryllium data. we derive upper limits on the dark matter annihilation cross section and find that when the cosmic ray propagation parameters are treated as nuisance parameters (as we argue is appropriate), the resulting limits are significantly less stringent than have been previously reported. we also note (as have several previous groups) that simple galprop-like diffusion-reacceleration models predict a spectrum of cosmic ray antiprotons that is in good agreement with pamela's observations above ~ 5 gev, but that significantly underpredict the flux at lower energies. although the complexity of modeling cosmic ray propagation at gev-scale energies makes it difficult to determine the origin of this discrepancy, we consider the possibility that the excess antiprotons are the result of annihilating dark matter. suggestively, we find that this excess is best fit for mdm ~ 35 gev and σ v ~ 10-26 cm3/s (to bb̄), in good agreement with the mass and cross section previously shown to be required to generate the gamma-ray excess observed from the galactic center. | what does the pamela antiproton spectrum tell us about dark matter? |
the spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. the first spallation reactions induced with an accelerator took place in 1947 at the berkeley cyclotron (university of california) with 200mev deuterons and 400mev alpha beams. they highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. in the same year, r. serber described the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. in 2010 iaea organized a workshop to present the results of the most widely used spallation codes within a benchmark of spallation models. if one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since serber. particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of mev up to some gev. an overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool. | spallation reactions: a successful interplay between modeling and applications |
the infrared spectrograph (irs) on board the spitzer space telescope observed about 15,000 objects during the cryogenic mission lifetime. observations provided low-resolution (r=λ /{δ }λ ≈ 60-127) spectra over ≈ 5-38 μm and high-resolution (r≈ 600) spectra over 10-37 μm. the cornell atlas of spitzer/irs sources (cassis) was created to provide publishable quality spectra to the community. low-resolution spectra have been available in cassis since 2011, and here we present the addition of the high-resolution spectra. the high-resolution observations represent approximately one-third of all staring observations performed with the irs instrument. while low-resolution observations are adapted to faint objects and/or broad spectral features (e.g., dust continuum, molecular bands), high-resolution observations allow more accurate measurements of narrow features (e.g., ionic emission lines) as well as a better sampling of the spectral profile of various features. given the narrow aperture of the two high-resolution modules, cosmic ray hits and spurious features usually plague the spectra. our pipeline is designed to minimize these effects through various improvements. a super-sampled point-spread function was created in order to enable the optimal extraction in addition to the full aperture extraction. the pipeline selects the best extraction method based on the spatial extent of the object. for unresolved sources, the optimal extraction provides a significant improvement in signal-to-noise ratio over a full aperture extraction. we have developed several techniques for optimal extraction, including a differential method that eliminates low-level rogue pixels (even when no dedicated background observation was performed). the updated cassis repository now includes all the spectra ever taken by the irs, with the exception of mapping observations. | cassis: the cornell atlas of spitzer/infrared spectrograph sources. ii. high-resolution observations |
although supernova remnants remain the main suspects as sources of galactic cosmic rays up to the knee, the supernova paradigm still has many loose ends. the weakest point in this construction is the possibility that individual supernova remnants can accelerate particles to the rigidity of the knee, ~ 106 gv. this scenario heavily relies upon the possibility to excite current driven non-resonant hybrid modes while the shock is still at the beginning of the sedov phase. these modes can enhance the rate of particle scattering thereby leading to potentially very-high maximum energies. here we calculate the spectrum of particles released into the interstellar medium from the remnants of different types of supernovae. we find that only the remnants of very powerful, rare core-collapse supernova explosions can accelerate light elements such as hydrogen and helium nuclei, to the knee rigidity, and that the local spectrum of cosmic rays directly constrains the rate of such events, if they are also source of pev cosmic rays. on the other hand, for remnants of typical core-collapse supernova explosions, the sedov phase is reached at late times, when the maximum energy is too low and the spectrum at very-high energies is very steep, being mostly produced during the ejecta dominated phase. for typical thermonuclear explosions, resulting in type ia supernovae, we confirm previous findings that these objects can only produce cosmic rays up to ≲ 105 gev. the implications for the overall cosmic ray spectrum observed at the earth and for the detection of pevatrons by future gamma-ray observatories are discussed. | the low rate of galactic pevatrons |
we simulate the propagation of cosmic rays at ultra-high energies, ≳1018 ev, in models of extragalactic magnetic fields in constrained simulations of the local universe. we use constrained initial conditions with the cosmological magnetohydrodynamics code enzo. the resulting models of the distribution of magnetic fields in the local universe are used in the crpropa code to simulate the propagation of ultra-high energy cosmic rays. we investigate the impact of six different magneto-genesis scenarios, both primordial and astrophysical, on the propagation of cosmic rays over cosmological distances. moreover, we study the influence of different source distributions around the milky way. our study shows that different scenarios of magneto-genesis do not have a large impact on the anisotropy measurements of ultra-high energy cosmic rays. however, at high energies above the greisen-zatsepin-kuzmin (gzk)-limit, there is anisotropy caused by the distribution of nearby sources, independent of the magnetic field model. this provides a chance to identify cosmic ray sources with future full-sky measurements and high number statistics at the highest energies. finally, we compare our results to the dipole signal measured by the pierre auger observatory. all our source models and magnetic field models could reproduce the observed dipole amplitude with a pure iron injection composition. our results indicate that the dipole is observed due to clustering of secondary nuclei in direction of nearby sources of heavy nuclei. a light injection composition is disfavoured, since the increase in dipole angular power from 4 to 8 eev is too slow compared to observation by the pierre auger observatory. | simulations of ultra-high energy cosmic rays in the local universe and the origin of cosmic magnetic fields |
very high-energy γ rays (vhe, e ≳ 100 gev) propagating over cosmological distances can interact with the low-energy photons of the extragalactic background light (ebl) and produce electron-positron pairs. the transparency of the universe to vhe γ rays is then directly related to the spectral energy distribution (sed) of the ebl. the observation of features in the vhe energy spectra of extragalactic sources allows the ebl to be measured, which otherwise is very difficult. an ebl model-independent measurement of the ebl sed with the h.e.s.s. array of cherenkov telescopes is presented. it was obtained by extracting the ebl absorption signal from the reanalysis of high-quality spectra of blazars. from h.e.s.s. data alone the ebl signature is detected at a significance of 9.5σ, and the intensity of the ebl obtained in different spectral bands is presented together with the associated γ-ray horizon. | measurement of the ebl spectral energy distribution using the vhe γ-ray spectra of h.e.s.s. blazars |
understanding large-scale interacting quantum matter requires dealing with the huge number of quanta that are produced by scattering even a few particles against a complex quantum object. prominent examples are found from high-energy cosmic ray showers, to the optical or electrical driving of degenerate fermi gases. we tackle this challenge in the context of many-body quantum optics, as motivated by the recent developments of circuit quantum electrodynamics at ultrastrong coupling. the issue of particle production is addressed quantitatively with a simple yet powerful concept rooted in the quantum superposition principle of multimode coherent states. this key idea is illustrated by the study of multiphoton emission from a single two-level artificial atom coupled to a high impedance waveguide, driven by a nearly monochromatic coherent tone. we find surprisingly that the off-resonant inelastic emission line shape is dominated by broadband particle production, due to the large phase space associated with contributions that do not conserve the number of excitations. such frequency conversion processes produce striking signatures in time correlation measurements, which can be tested experimentally in quantum waveguides. these ideas open new directions for the simulation of a variety of physical systems, from polaron dynamics in solids to complex superconducting quantum architectures. | particle production in ultrastrong-coupling waveguide qed |
here we present halo-fdca, a robust open source python package for modeling and estimating total flux densities of radio (mini) halos in galaxy clusters. radio halos are extended (∼ 200 - 1500 kpc in size) synchrotron emitting sources found in galaxy clusters that trace the presence of cosmic rays and magnetic fields in the intracluster medium (icm). these sources are centrally located and have a low surface brightness. their exact origin is still unknown but they are likely related to cosmic rays being re-accelerated in-situ by merger or sloshing driven icm turbulence. the presented algorithm combines the numerical power of the markov chain monte carlo routine and multiple theoretical models to estimate the total radio flux density of a radio halo from a radio image and its associated uncertainty. this method introduces a flexible analytic fitting procedure to replace existing simplistic manual measurements prone to biases and inaccuracies. it allows to easily determine the properties of the emission and is particularly suitable for future studies of large samples of clusters. | a robust model for flux density calculations of radio halos in galaxy clusters: halo-fdca |
cosmic rays (crs) are an important energy source in the circumgalactic medium that impact the multiphase gas structure and dynamics. we perform two-dimensional cr-magnetohydrodynamic simulations to investigate the role of crs in accelerating multiphase gas formed via thermal instability. we compare outflows driven by crs to those driven by a hot wind with equivalent momentum. we find that cr-driven outflow produces lower density contrast between cold and hot gas due to nonthermal pressure support, and yields a more filamentary cloud morphology. while entrainment in a hot wind can lead to cold gas increasing due to efficient cooling, crs tend to suppress cold gas growth. the mechanism of this suppression depends on magnetic field strength, with crs either reducing cooling or shredding the clouds by differential acceleration. despite the suppression of cold gas growth, crs are able to launch the cold clouds to observed velocities without rapid destruction. the dynamical interaction between crs and multiphase gas is also sensitive to the magnetic field strength. in relatively strong fields, the crs are more important for direct momentum input to cold gas. in relatively weak fields, the crs impact gas primarily by heating, which modifies gas pressure. | cosmic-ray-driven multiphase gas formed via thermal instability |
we account for particle emission and gravitational radiation from cosmic string loops to determine their effect on the loop distribution and observational signatures of strings. the effect of particle emission is that the number density of loops no longer scales. this results in a high-frequency cutoff on the stochastic gravitational wave background, but we show that the expected cutoff is outside the range of current and planned detectors. particle emission from string loops also produces a diffuse gamma-ray background that is sensitive to the presence of kinks and cusps on the loops. however, both for kinks and cusps, and with mild assumptions about particle physics interactions, current diffuse gamma-ray background observations do not constrain g μ . | particle emission and gravitational radiation from cosmic strings: observational constraints |
a soft x-ray focusing telescope (sxt) was launched in a near earth, near equatorial orbit aboard the astrosat on september 28th, 2015. the sxt electronics was switched on within 3 days of the launch and the first light was seen on october 26th, 2015 after a sequence of operations involving venting of the camera, cooling of the ccd, opening of the telescope door followed by the opening of the camera door. several cosmic x-ray sources have been observed since then during the performance verification phase. a few near-simultaneous observations have also been carried out with the swift observatory. the in-orbit performance of the sxt based on these observations is presented here. | in-orbit performance of sxt aboard astrosat |
we forecast the potential of the forthcoming x-ray galaxy-cluster survey with erosita to constrain dark-energy models. we focus on spatially flat cosmological scenarios with either constant or time-dependent dark-energy equation-of-state parameters. fisher information is extracted from the number density and spatial clustering of a photon-count-limited sample of clusters of galaxies up to z ∼ 2. we consider different scenarios for the availability of (i) x-ray follow-up observations, (ii) photometric and spectroscopic redshifts, and (iii) accurate knowledge of the observable - mass relation down to the scale of galaxy groups, but no additional observation-related systematics are taken into account. with about 125 000 clusters (detected with more than 50 photons and with mass m500c ≳ 1013h-1 m⊙) from an average all-sky exposure of 1.6 ks, erosita will give marginalized, one-dimensional, 1σ errors of δσ8 = ±0.008 (∼1 per cent), δωm = ±0.006 (2.2 per cent), δw0 = ±0.07 (7 per cent), and δwa = ±0.25 (optimistic scenario) in combination with (and largely improving upon) current constraints from various cosmological probes (cosmic microwave background, baryonic acoustic oscillations, type ia sne). our findings correspond to a dark-energy figure of merit in the range of 116-162 (after the 4 yr of all-sky survey), making erosita one of the first stage iv experiments to come on line according to the classification of the dark energy task force. to secure improved mass calibrations and to include high-redshift clusters (z ≳ 0.5) as well as objects at the group-mass scale (m500c ≲ 5 × 1013h-1 m⊙) will be vital to reach such accuracies. | forecasts on dark energy from the x-ray cluster survey with erosita: constraints from counts and clustering |
the heliospheric modulation model helmod is a two dimensional treatment dealing with the helio-colatitude and radial distance from sun and is employed to solve the transport-equation for the gcr propagation through the heliosphere down to earth. this work presents the current version 3 of the helmod model and reviews how main processes involved in gcr propagation were implemented. the treatment includes the so-called particle drift effects - e.g., those resulting, for instance, from the extension of the neutral current sheet inside the heliosphere and from the curvature and gradient of the imf -, which affect the transport of particles entering the solar cavity as a function of their charge sign. the helmod model is capable to provide modulated spectra which well agree within the experimental errors with those measured by ams-01, bess, pamela and ams-02 during the solar cycles 23 and 24. furthermore, the counting rate measured by ulysses at ± 80 ° of solar latitude and 1-5 au was also found in agreement with that expected by helmod code version 3. | propagation of cosmic rays in heliosphere: the helmod model |
potential deleterious health effects to astronauts induced by space radiation is one of the most important long-term risks for human space missions, especially future planetary missions to mars which require a return-trip duration of about 3 years with current propulsion technology. in preparation for future human exploration, the radiation assessment detector (rad) was designed to detect and analyze the most biologically hazardous energetic particle radiation on the martian surface as part of the mars science laboratory (msl) mission. rad has measured the deep space radiation field within the spacecraft during the cruise to mars and the cosmic ray induced energetic particle radiation on mars since curiosity's landing in august 2012. these first-ever surface radiation data have been continuously providing a unique and direct assessment of the radiation environment on mars. we analyze the temporal variation of the galactic cosmic ray (gcr) radiation and the observed solar energetic particle (sep) events measured by rad from the launch of msl until december 2020, i.e., from the pre-maximum of solar cycle 24 throughout its solar minimum until the initial year of cycle 25. over the long term, the mars's surface gcr radiation increased by about 50% due to the declining solar activity and the weakening heliospheric magnetic field. at different time scales in a shorter term, rad also detected dynamic variations in the radiation field on mars. we present and quantify the temporal changes of the radiation field which are mainly caused by: (a) heliospheric influences which include both temporary impacts by solar transients and the long-term solar cycle evolution, (b) atmospheric changes which include the martian daily thermal tide and seasonal co2 cycle as well as the altitude change of the rover, (c) topographical changes along the rover path-way causing addition structural shielding and finally (d) solar particle events which occur sporadically and may significantly enhance the radiation within a short time period. quantification of the variation allows the estimation of the accumulated radiation for a return trip to the surface of mars under various conditions. the accumulated gcr dose equivalent, via a hohmann transfer, is about 0.65 ±0.24 sievert and 1.59 ±0.12 sievert during solar maximum and minimum periods, respectively. the shielding of the gcr radiation by heliospheric magnetic fields during solar maximum periods is rather efficient in reducing the total gcr-induced radiation for a mars mission, by more than 50%. however, further contributions by seps must also be taken into account. in the future, with advanced nuclear thrusters via a fast transfer, we estimate that the total gcr dose equivalent can be reduced to about 0.2 sievert and 0.5 sievert during solar maximum and minimum periods respectively. in addition, we also examined factors which may further reduce the radiation dose in space and on mars and discuss the many uncertainties in the interpreting the biological effect based on the current measurement. | radiation environment for future human exploration on the surface of mars: the current understanding based on msl/rad dose measurements |
dark matter (dm) direct detection experiments have been setting strong limits on the dm-nucleon scattering cross section at the dm mass above a few gev, but leave large parameter spaces unexplored in the low mass region. dm is likely to be scattered and boosted by relativistic cosmic rays in the expanding universe if it can generate nuclear recoils in direct detection experiments to offer observable signals. since low energy threshold detectors using germanium have provided good constraints on ordinary halo gev-scale dm, it is necessary to re-analyze 102.8 kg $ \times $ day data in the cdex-10 experiment assuming that dm is boosted by cosmic rays. for the dm mass range 1 kev $ <m_\chi < $ 1 mev and the effective distance within 1 kpc, we reach an almost flat floor limit at $ 8.32\times10^{-30} $ cm2 for the spin-independent dm-nucleon scattering cross section, at a 90% confidence level. the cdex-10 result is able to close the gap unambiguously in the parameter space between the miniboone and xenon1t constraints, which were partially hindered by the earth attenuation effect. we also quantitatively calculate the expected neutrino floor on searching for crbdm in future direct detection experiments using germanium. *supported in part by guangdong basic and applied basic research foundation (2019a1515012216), national undergraduate innovation and entrepreneurship training program (20201023) and the cas center for excellence in particle physics (ccepp) | constraints on cosmic-ray boosted dark matter in cdex-10 |
the bess-polar collaboration measured the energy spectra of cosmic-ray protons and helium during two long-duration balloon flights over antarctica in 2004 december and 2007 december at substantially different levels of solar modulation. proton and helium spectra probe the origin and propagation history of cosmic rays in the galaxy, and are essential to calculations of the expected spectra of cosmic-ray antiprotons, positrons, and electrons from interactions of primary cosmic-ray nuclei with the interstellar gas, and to calculations of atmospheric muons and neutrinos. we report absolute spectra at the top of the atmosphere for cosmic-ray protons in the kinetic energy range 0.2-160 gev and helium nuclei in the range 0.15-80 gev/nucleon. the corresponding magnetic-rigidity ranges are 0.6-160 gv for protons and 1.1-160 gv for helium. these spectra are compared to measurements from previous bess flights and from atic-2, pamela, and ams-02. we also report the ratio of the proton and helium fluxes from 1.1 to 160 gv and compare this to the ratios from pamela and ams-02. | measurements of cosmic-ray proton and helium spectra from the bess-polar long-duration balloon flights over antarctica |
context. the h3+ molecule has been detected in many lines of sight within the central molecular zone (cmz) with exceptionally large column densities and unusual excitation properties compared to diffuse local clouds. the detection of the (3, 3) metastable level has been suggested to be the signature of warm and diffuse gas in the cmz.aims: we aim to determine the physical conditions and processes in the cmz that explain the ubiquitous properties of h3+ in this medium and to constrain the value of the cosmic-ray ionization rate.methods: we use the meudon photodissociation region (pdr) code in which h3+ excitation has been implemented. we re-examine the relationship between the column density of h3+ and the cosmic-ray ionization rate, ζ, up to large values of ζ in the frame of this full chemical model. we study the impact of the various mechanisms that can excite h3+ in its metastable state. we produce grids of pdr models exploring different parameters (ζ, size of clouds, metallicity) and infer the physical conditions that best match the observations toward ten lines of sight in the cmz. for one of them, herschel observations of hf, oh+, h2o+, and h3o+ can be used as additional constraints. we check that the results found for h3+ also account for the observations of these molecules.results: we find that the linear relationship between n(h3+) and ζ only holds up to a certain value of the cosmic-ray ionization rate, which depends on the proton density. a value ζ ~ 1-11 × 10-14 s-1 explains both the large observed h3+ column density and its excitation in the metastable level (3, 3). this ζ value agrees with that derived from synchrotron emission and fe kα line. it also reproduces n(oh+), n(h2o+) and n(h3o+) detected toward sgr b2(n). we confirm that the cmz probed by h3+ is diffuse, nh≲ 100 cm-3 and warm, t ~ 212-505 k. this warm medium is due to cosmic-ray heating. we also find that the diffuse component probed by h3+ must fill a large fraction of the cmz. finally, we suggest the warm gas in the cmz enables efficient h2 formation via chemisorption sites as in pdrs. this contributes to enhance the abundance of h3+ in this high cosmic-ray flux environment. | physical conditions in the central molecular zone inferred by h3+ |
direct measurements of cosmic ray (cr) species combined with observations of their associated γ-ray emissions can be used to constrain models of cr propagation, trace the structure of the galaxy, and search for signatures of new physics. the spatial density distribution of interstellar gas is a vital element for all these studies. so far, models have employed the 2d cylindrically symmetric geometry, but their accuracy is well behind that of the available data. in this paper, 3d spatial density models for neutral and molecular hydrogen are constructed based on empirical model fitting to gas line-survey data. the developed density models incorporate spiral arms and account for the warping of the disk, and the increasing gas scale height with radial distance from the galactic center. they are employed together with the galprop cr propagation code to investigate how the new 3d gas models affect calculations of cr propagation and high-energy γ-ray intensity maps. the calculations reveal non-trivial features that are directly related to the new gas models. the best-fit values for propagation model parameters employing 3d gas models are presented and they differ significantly from those derived with the 2d gas density models that have been widely used. the combination of 3d cr and gas density models provide a more realistic basis for the interpretation of non-thermal emissions from the galaxy. | the three-dimensional spatial distribution of interstellar gas in the milky way: implications for cosmic rays and high-energy gamma-ray emissions |
we calculate the diffusion coefficients of charged cosmic rays (cr) propagating in regular and turbulent magnetic fields. if the magnetic field is dominated by an isotropic turbulent component, we find that crs reside too long in the galactic disc. as a result, crs overproduce secondary nuclei like boron for any reasonable values of the strength and the coherence length of an isotropic turbulent field. we conclude therefore that the propagation of galactic crs has to be strongly anisotropic because of a sufficiently strong regular field and/or of an anisotropy in the turbulent field. as a consequence, the number of sources contributing to the local cr flux is reduced by a factor script o(100) compared to the case of isotropic cr diffusion. | reconciling cosmic ray diffusion with galactic magnetic field models |
in this work, we investigate the 2014-2015 neutrino flare associated with the blazar txs 0506+056 and a recently discovered muon neutrino event icecube-200107a in spatial coincidence with the blazar 4fgl j0955.1+3551, under the framework of a two-zone radiation model of blazars where an inner/outer blob close to/far from the supermassive black hole is invoked. an interesting feature that the two sources have in common is that no evidence of gev gamma-ray activity is found during the neutrino detection period, probably implying a large opacity for gev gamma rays in the neutrino production region. in our model, continuous particle acceleration/injection takes place in the inner blob at the jet base, where the hot x-ray corona of the supermassive black hole provides target photon fields for efficient neutrino production and strong gev gamma-ray absorption. we show that this model can self-consistently interpret the neutrino emission from both blazars in a large parameter space. in the meantime, the dissipation processes in outer blob are responsible for the simultaneous multiwavelength emission of both sources. in agreement with previous studies of txs 0506+056, an intense mev emission from the induced electromagnetic cascade in the inner blob is robustly expected to accompany the neutrino flare in our model and could be used to test the model using the next-generation mev gamma-ray detector in the future. | a two-zone blazar radiation model for "orphan" neutrino flares |
we present a novel determination of the astrophysical uncertainties associated to the secondary antiproton flux originating from cosmic-ray spallation on the interstellar gas. we select a set of propagation models compatible with the recent b/c data from pamela, and find those providing minimal and maximal antiproton fluxes in different energy ranges. we use this result to determine the most conservative bounds on relevant dark matter (dm) annihilation channels: we find that the recent claim of a dm interpretation of a gamma-ray excess in the galactic center region cannot be ruled out by current antiproton data. | secondary antiprotons as a galactic dark matter probe |
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