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sensor-to-sensor variability is a source of error common to all geoscientific instruments that needs to be assessed before comparative and applied research can be performed with multiple sensors. consistency among sensor systems is especially critical when subtle features of the surrounding terrain are to be identified. cosmic-ray neutron sensors (crnss) are a recent technology used to monitor hectometre-scale environmental water storages, for which a rigorous comparison study of numerous co-located sensors has not yet been performed. in this work, nine stationary crns probes of type "crs1000" were installed in relative proximity on a grass patch surrounded by trees, buildings, and sealed areas. while the dynamics of the neutron count rates were found to be similar, offsets of a few percent from the absolute average neutron count rates were found. technical adjustments of the individual detection parameters brought all instruments into good agreement. furthermore, we found a critical integration time of 6 h above which all sensors showed consistent dynamics in the data and their rmse fell below 1 % of gravimetric water content. the residual differences between the nine signals indicated local effects of the complex urban terrain on the scale of several metres. mobile crns measurements and spatial simulations with the uranos neutron transport code in the surrounding area (25 ha) have revealed substantial sub-footprint heterogeneity to which crns detectors are sensitive despite their large averaging volume. the sealed and constantly dry structures in the footprint furthermore damped the dynamics of the crns-derived soil moisture. we developed strategies to correct for the sealed-area effect based on theoretical insights about the spatial sensitivity of the sensor. this procedure not only led to reliable soil moisture estimation during dry-out periods, it further revealed a strong signal of intercepted water that emerged over the sealed surfaces during rain events. the presented arrangement offered a unique opportunity to demonstrate the crns performance in complex terrain, and the results indicated great potential for further applications in urban climate research. | intercomparison of cosmic-ray neutron sensors and water balance monitoring in an urban environment |
by heating the intergalactic medium (igm) before reionization, x-rays are expected to play a prominent role in the early universe. the cosmic 21-cm signal from this 'epoch of heating' (eoh) could serve as a clean probe of high-energy processes inside the first galaxies. here, we improve on prior estimates of this signal by using high-resolution hydrodynamic simulations to calculate the x-ray absorption due to the interstellar medium (ism) of the host galaxy, typically residing in haloes with mass 107.5-8.5 m⊙ at z ∼ 8-15. x-rays absorbed inside the host galaxy are unable to escape into the igm and contribute to the eoh. we find that the x-ray opacity through these galaxies can be approximated by a metal-free ism with a typical column density of log [n_{h i}/cm^{-2}] = 21.4^{+0.40}_{-0.65}. we compute the resulting 21-cm signal by combining these ism opacities with public spectra of high-mass x-ray binaries (thought to be important x-ray sources in the early universe). our results support 'standard scenarios' in which the x-ray heating of the igm is inhomogeneous, and occurs before the bulk of reionization. the large-scale (k ∼ 0.1 mpc-1) 21-cm power reaches a peak of ≈100 mk2 at z ∼ 10-15, with the redshift depending on the cosmic star formation history. our main results can be reproduced by approximating the x-ray emission from high-mass x-ray binaries by a power law with energy index α ≈ 1, truncated at energies below 0.5 kev. | high-mass x-ray binaries and the cosmic 21-cm signal: impact of host galaxy absorption |
soil moisture patterns are commonly thought to be dominated by land surface characteristics, such as soil texture, at small scales and by atmospheric processes, such as precipitation, at larger scales. however, a growing body of evidence challenges this conceptual model. we investigated the structural similarity and spatial correlations between mesoscale (∼1-100 km) soil moisture patterns and land surface and atmospheric factors along a 150 km transect using 4 km multisensor precipitation data and a cosmic-ray neutron rover, with a 400 m diameter footprint. the rover was used to measure soil moisture along the transect 18 times over 13 months. spatial structures of soil moisture, soil texture (sand content), and antecedent precipitation index (api) were characterized using autocorrelation functions and fitted with exponential models. relative importance of land surface characteristics and atmospheric processes were compared using correlation coefficients (r) between soil moisture and sand content or api. the correlation lengths of soil moisture, sand content, and api ranged from 12-32 km, 13-20 km, and 14-45 km, respectively. soil moisture was more strongly correlated with sand content (r = -0.536 to -0.704) than with api for all but one date. thus, land surface characteristics exhibit coherent spatial patterns at scales up to 20 km, and those patterns often exert a stronger influence than do precipitation patterns on mesoscale spatial patterns of soil moisture. | soil texture often exerts a stronger influence than precipitation on mesoscale soil moisture patterns |
cosmic-ray neutron sensing (crns) allows for non-invasive soil moisture estimations at the field scale. the derivation of soil moisture generally relies on secondary cosmic-ray neutrons in the epithermal to fast energy ranges. most approaches and processing techniques for observed neutron intensities are based on the assumption of homogeneous site conditions or of soil moisture patterns with correlation lengths shorter than the measurement footprint of the neutron detector. however, in view of the non-linear relationship between neutron intensities and soil moisture, it is questionable whether these assumptions are applicable. in this study, we investigated how a non-uniform soil moisture distribution within the footprint impacts the crns soil moisture estimation and how the combined use of epithermal and thermal neutrons can be advantageous in this case. thermal neutrons have lower energies and a substantially smaller measurement footprint around the sensor than epithermal neutrons. analyses using the uranos (ultra rapid neutron-only simulation) monte carlo simulations to investigate the measurement footprint dynamics at a study site in northeastern germany revealed that the thermal footprint mainly covers mineral soils in the near-field to the sensor while the epithermal footprint also covers large areas with organic soils. we found that either combining the observed thermal and epithermal neutron intensities by a rescaling method developed in this study or adjusting all parameters of the transfer function leads to an improved calibration against the reference soil moisture measurements in the near-field compared to the standard approach and using epithermal neutrons alone. we also found that the relationship between thermal and epithermal neutrons provided an indicator for footprint heterogeneity. we, therefore, suggest that the combined use of thermal and epithermal neutrons offers the potential of a spatial disaggregation of the measurement footprint in terms of near- and far-field soil moisture dynamics. | towards disentangling heterogeneous soil moisture patterns in cosmic-ray neutron sensor footprints |
a search for ultra-high energy photons with energies above 1 eev is performed using nine years of data collected by the pierre auger observatory in hybrid operation mode. an unprecedented separation power between photon and hadron primaries is achieved by combining measurements of the longitudinal air-shower development with the particle content at ground measured by the fluorescence and surface detectors, respectively. only three photon candidates at energies 1-2 eev are found, which is compatible with the expected hadron-induced background. upper limits on the integral flux of ultra-high energy photons of 0.027, 0.009, 0.008, 0.008 and 0.007 km-2 sr-1 yr-1 are derived at 95% c.l. for energy thresholds of 1, 2, 3, 5 and 10 eev. these limits bound the fractions of photons in the all-particle integral flux below 0.1%, 0.15%, 0.33%, 0.85% and 2.7%. for the first time the photon fraction at eev energies is constrained at the sub-percent level. the improved limits are below the flux of diffuse photons predicted by some astrophysical scenarios for cosmogenic photon production. the new results rule-out the early top-down models - in which ultra-high energy cosmic rays are produced by, e.g., the decay of super-massive particles - and challenge the most recent super-heavy dark matter models. | search for photons with energies above 1018 ev using the hybrid detector of the pierre auger observatory |
we propose the idea of "earth shielding" to reject cosmic-ray backgrounds, in the search for boosted dark matter at surface neutrino detectors, resulting in the enhancement of the signal-to-background ratio. the identification of cosmic-originating rare signals, especially lacking features, at surface detectors is often considered hopeless due to a vast amount of cosmic-ray-induced background, hence underground experiments are better motivated to avoid such a challenge. we claim that surface detectors can attain remarkable sensitivities to even featureless signals, once restricting to events coming through the earth from the opposite side of the detector location for the signals leaving appreciable tracks from which the source direction is inferred. by doing so, potential backgrounds in the signal region of interest can be substantially suppressed. to validate our claim, we study experimental reaches at several surface experiments such as sbn program (microboone, icarus, and sbnd) and protodune for elastic boosted dark matter signatures stemming from the galactic center. we provide a systematic discussion on maximizing associated signal sensitivities. | boosted dark matter quarrying at surface neutrino detectors |
the metal abundance of the hot plasma that permeates galaxy clusters represents the accumulation of heavy elements produced by billions of supernovae. therefore, x-ray spectroscopy of the intracluster medium provides an opportunity to investigate the nature of supernova explosions integrated over cosmic time. in particular, the abundance of the iron-peak elements (chromium, manganese, iron and nickel) is key to understanding how the progenitors of typical type ia supernovae evolve and explode. recent x-ray studies of the intracluster medium found that the abundance ratios of these elements differ substantially from those seen in the sun, suggesting differences between the nature of type ia supernovae in the clusters and in the milky way. however, because the k-shell transition lines of chromium and manganese are weak and those of iron and nickel are very close in photon energy, high-resolution spectroscopy is required for an accurate determination of the abundances of these elements. here we report observations of the perseus cluster, with statistically significant detections of the resonance emission from chromium, manganese and nickel. our measurements, combined with the latest atomic models, reveal that these elements have near-solar abundance ratios with respect to iron, in contrast to previous claims. comparison between our results and modern nucleosynthesis calculations disfavours the hypothesis that type ia supernova progenitors are exclusively white dwarfs with masses well below the chandrasekhar limit (about 1.4 times the mass of the sun). the observed abundance pattern of the iron-peak elements can be explained by taking into account a combination of near- and sub-chandrasekhar-mass type ia supernova systems, adding to the mounting evidence that both progenitor types make a substantial contribution to cosmic chemical enrichment. | solar abundance ratios of the iron-peak elements in the perseus cluster |
the escape of cosmic rays from the galaxy leads to a gradient in the cosmic ray pressure that acts as a force on the background plasma, in the direction opposite to the gravitational pull. if this force is large enough to win against gravity, a wind can be launched that removes gas from the galaxy, thereby regulating several physical processes, including star formation. the dynamics of these cosmic ray driven winds is intrinsically non-linear in that the spectrum of cosmic rays determines the characteristics of the wind (velocity, pressure, magnetic field) and in turn the wind dynamics affects the cosmic ray spectrum. moreover, the gradient of the cosmic ray distribution function causes excitation of alfvén waves, that in turn determines the scattering properties of cosmic rays, namely their diffusive transport. these effects all feed into each other so that what we see at the earth is the result of these non-linear effects. here, we investigate the launch and evolution of such winds, and we determine the implications for the spectrum of cosmic rays by solving together the hydrodynamical equations for the wind and the transport equation for cosmic rays under the action of self-generated diffusion and advection with the wind and the self-excited alfvén waves. | cosmic ray driven galactic winds |
mev dark matter (dm) particles annihilating or decaying to electron-positron pairs cannot, in principle, be observed via local cosmic-ray (cr) measurements because of the shielding solar magnetic field. in this letter, we take advantage of spacecraft voyager 1's capacity for detecting interstellar crs since it crossed the heliopause in 2012. this opens up a new avenue to probe dm in the sub-gev energy/mass range that we exploit here for the first time. from a complete description of the transport of electrons and positrons at low energy, we derive predictions for both the secondary astrophysical background and the pair production mechanisms relevant to dm annihilation or decay down to the mev mass range. interestingly, we show that reacceleration may push positrons up to energies larger than the dm particle mass. we combine the constraints from the voyager and ams-02 data to get novel limits covering a very extended dm particle mass range, from mev to tev. in the mev mass range, our limits reach annihilation cross sections of order ⟨σ v ⟩∼10-28 cm3/s . an interesting aspect is that these limits barely depend on the details of cosmic-ray propagation in the weak reacceleration case, a configuration which seems to be favored by the most recent b /c data. though extracted from a completely different and new probe, these bounds have a strength similar to those obtained with the cosmic microwave background—they are even more stringent for p -wave annihilation. | novel cosmic-ray electron and positron constraints on mev dark matter particles |
it is widely believed that the bulk of the galactic cosmic rays is accelerated in supernova remnants (snrs). however, no observational evidence of the presence of particles of pev energies in snrs has yet been found. the young historical snr cassiopeia a (cas a) appears as one of the best candidates to study acceleration processes. between 2014 december and 2016 october, we observed cas a with the magic telescopes, accumulating 158 h of good quality data. we derived the spectrum of the source from 100 gev to 10 tev. we also analysed ∼8 yr of fermi-lat to obtain the spectral shape between 60 mev and 500 gev. the spectra measured by the lat and magic telescopes are compatible within the errors and show a clear turn-off (4.6σ) at the highest energies, which can be described with an exponential cut-off at e_c = 3.5(^{+1.6}_{-1.0})_{stat} (^{+0.8}_{-0.9})_{sys} tev. the gamma-ray emission from 60 mev to 10 tev can be attributed to a population of high-energy protons with a spectral index of ∼2.2 and an energy cut-off at ∼10 tev. this result indicates that cas a is not contributing to the high energy (∼pev) cosmic ray sea in a significant manner at the present moment. a one-zone leptonic model fails to reproduce by itself the multiwavelength spectral energy distribution. besides, if a non-negligible fraction of the flux seen by magic is produced by leptons, the radiation should be emitted in a region with a low magnetic field (b⪅180 μg) like in the reverse shock. | a cut-off in the tev gamma-ray spectrum of the snr cassiopeia a |
we consider the positivity bounds for wimp scalar dark matter with effective higgs-portal couplings up to dimension-8 operators. taking the superposed states for standard model higgs and scalar dark matter, we show that the part of the parameter space for the effective couplings, otherwise unconstrained by phenomenological bounds, is ruled out by the positivity bounds on the dimension-8 derivative operators. we find that dark matter relic density, direct and indirect detection and lhc constraints are complementary to the positivity bounds in constraining the effective higgs-portal couplings. in the effective theory obtained from massive graviton or radion, there appears a correlation between dimension-8 operators and other effective higgs-portal couplings for which the strong constraint from direct detection can be evaded. nailing down the parameter space mainly by relic density, direct detection and positivity bounds, we find that there are observable cosmic ray signals coming from the dark matter annihilations into a pair of higgs bosons, ww or zz. | positivity bounds on higgs-portal dark matter |
observations of the milky way at tev-pev energies reveal a bright diffuse flux of hadronic cosmic rays and also bright point sources of gamma rays. if the gamma-ray sources are hadronic cosmic-ray accelerators, then they must also be neutrino sources. however, no neutrino sources have been detected. where are they? we introduce a new population-based approach to probe milky way hadronic pevatrons, demanding consistency between diffuse and point-source pev-range data on cosmic rays, gamma rays, and neutrinos. for the pevatrons, two extreme scenarios are allowed: (1) the hadronic cosmic-ray accelerators and the gamma-ray sources are the same objects, so that bright neutrino sources exist and improved telescopes can detect them, versus (2) the hadronic cosmic-ray accelerators and the gamma-ray sources are distinct, so that there are no detectable neutrino sources. the latter case is possible if hadronic accelerators have sufficiently thin column densities. we quantify present constraints and future prospects, showing how to reveal the nature of the hadronic pevatrons. | where are milky way's hadronic pevatrons? |
the origin of lithium (li) and its production process have long been uncertain. li could be produced by big bang nucleosynthesis, interactions of energetic cosmic rays with interstellar matter, evolved low-mass stars, novae, and supernova explosions. chemical evolution models and observed stellar li abundances suggest that at least half the li may have been produced in red giants, asymptotic giant branch (agb) stars, and novae. no direct evidence, however, for the supply of li from evolved stellar objects to the galactic medium has hitherto been found. here we report the detection of highly blue-shifted resonance lines of the singly ionized radioactive isotope of beryllium, 7be, in the near-ultraviolet spectra of the classical nova v339 del (nova delphini 2013) 38 to 48 days after the explosion. 7be decays to form 7li within a short time (half-life of 53.22 days). the 7be was created during the nova explosion via the alpha-capture reaction 3he(α,γ)7be (ref. 5). this result supports the theoretical prediction that a significant amount of 7li is produced in classical nova explosions. | explosive lithium production in the classical nova v339 del (nova delphini 2013) |
the mountain ranges of the iberian peninsula preserve a valuable record of past glaciations that may help reconstruct past atmospheric circulation patterns in response to cooling events in the north atlantic ocean. available chronologies for the glacial record of the cantabrian mountains, which are mainly based on radiocarbon and luminescence dating of glacial-related sediments, suggest that glaciers recorded their glacial maximum (gm) during mis 3 and experienced a later last glacial maximum (lgm) advance. this lgm extent is not established yet, preventing a fair correlation with available cosmic ray exposure (cre) based chronologies for the glacial record of the pyrenees and the sistema central. we present a glacial reconstruction and a 10be cre chronology for the porma valley, in the southern slope of the central cantabrian mountains. glacial evidence at the lowest altitudes correspond to erratic boulders and composite moraines whose minimum 10be cre age of 113.9 ± 7.1 ka suggests that glaciers were at their maximum extent during mis 5d, most likely in response to the minima in summertime insolation of the last glacial cycle. recessional moraines preserved within the glacial maximum limits allow the assessment of subsequent glacier advances or stagnations. the most remarkable advance took place prior to 55.7 ± 4.0 ka (probably at the end of mis 4), consistently with minimum radiocarbon ages previously reported for lacustrine glacial-related deposits in the cantabrian mountains. a limited number of 10be cre ages from a composite moraine suggest a possible advance of the porma glacier coeval with the global lgm; the glacier front attributed to the lgm would be placed within the margins of the previous gm like in the western pyrenees. erratic boulders perched on an ice-moulded bedrock surface provided a mean 10be cre age of 17.7 ± 1.0 ka, suggesting that part of the recessional moraine sequence corresponds to minor advances or stagnations of the glacier fronts during the lateglacial period. this recessional response is consistent with deglacial chronologies previously established in the pyrenees and the sistema central, and correlates with the coldest and driest conditions of mis 2 according to lacustrine records. finally, a relict rock glacier provided a mean 10be cre age of 15.7 ± 0.8 ka for movement cessation of its toe, indicating that periglacial conditions prevailed, at least, until the end of heinrich stadial 1/mystery interval. | chronology of glaciations in the cantabrian mountains (nw iberia) during the last glacial cycle based on in situ-produced 10be |
over the past few years, the taiga (tunka advanced instrument for cosmic ray physics and gamma-ray astronomy) observatory has been being deployed in the tunka valley, republic of buryatia. it is designed for studying gamma rays of energy above 30 tev and performing searches for sources of galactic cosmic rays with energies in the vicinity of 1 pev, which is an energy region around the classic knee in the cosmic-ray energy spectrum. the first phase of the observatory will be situated at a distance of about 50 km from lake baikal at the site of the tunka-133 array. the taiga gamma observatory will include a network of 500 wide-angle (0.6 sr) cherenkov detectors (taiga-hiscore array) and up to 16 atmospheric cherenkov telescopes (act) designed for analyzing the eas images (imaging atmospheric cherenkov telescopes, or iact) and positioned within an area of 5 km2. the observatory will also include muon detectors of total area 2000 m2 distributed over an area of 1 km2. within the next three years, it is planned to enhance the area of the taiga-hiscore array by a factor of four—from 0.25 km2 to 1 km2; to supplement the existing iact with two new ones; and to deploy new muon detectors with a total coverage of 200 m2. the structure of the new observatory is described along with the data analysis techniques used. the most interesting physical results are presented, and the research program for the future is discussed. | taiga gamma observatory: status and prospects |
motivated by the recently reported evidence of an association between a high-energy neutrino and a γ-ray flare from the blazar txs 0506+056, we calculate the expected high-energy neutrino signal from past, individual flares, from 12 blazars, selected in declinations favourable for detection with icecube. to keep the number of free parameters to a minimum, we mainly focus on bl lac objects and assume the synchrotron self-compton mechanism produces the bulk of the high-energy emission. we consider a broad range of the allowed parameter space for the efficiency of proton acceleration, the proton content of bl lac jets, and the presence of external photon fields. to model the expected neutrino fluence, we use simultaneous multiwavelength observations. we find that in the absence of external photon fields and with jet proton luminosity normalized to match the observed production rate of ultrahigh-energy cosmic rays, individual flaring sources produce a modest neutrino flux in icecube, n^{ic,10 yr}_{ν _{μ > 100 tev ≲ 10^{-3} muon neutrinos with energy exceeding 100 tev, stacking 10 yr of flare periods selected in the >800 mev fermi energy range, from each source. under optimistic assumptions about the jet proton luminosity and in the presence of external photon fields, we find that the two most powerful sources in our sample, ao 0235+164, and oj 287, would produce, in total, n^{ic × 10,10 yr}_{ν _{μ }, all flares, > 100 tev ≈ 3 muon neutrinos during fermi flaring periods, in future neutrino detectors with total instrumented volume ∼10 times larger than icecube, or otherwise, constrain the proton luminosity of blazar jets. | high-energy neutrino flux from individual blazar flares |
papers on the searches for the sources of astrophysical neutrinos, submitted to the 35th international cosmic ray conference (icrc 2017, busan, south korea) by the icecube collaboration | the icecube neutrino observatory - contributions to icrc 2017 part i: searches for the sources of astrophysical neutrinos |
the dark matter particle explorer (dampe) has observed a tentative peak at e ∼ 1.4 tev in the cosmic-ray electron spectrum. in this paper, we interpret this excess in the scotogenic type-ii seesaw model. this model extends the canonical type-ii seesaw model with dark matter (dm) candidates and a loop-induced vacuum expectation value of the triplet scalars, vδ , resulting in small neutrino masses naturally even for tev scale triplet scalars. assuming a nearby dm subhalo, the dampe excess can be explained by dm annihilating into a pair of triplet scalars which subsequently decay to charged lepton final states. spectrum fitting of the dampe excess indicates it potentially favors the inverted neutrino mass hierarchy. we also discuss how to evade associated neutrino flux in our model. | confronting the dampe excess with the scotogenic type-ii seesaw model |
context. the xmm-newton survey science centre consortium (ssc) develops software in close collaboration with the science operations centre to perform a pipeline analysis of all xmm-newton observations. in celebration of the twentieth anniversary of the xmm-newton launch, the ssc has compiled the fourth generation of serendipitous source catalogues, 4xmm.aims: the catalogue described here, 4xmm-dr9s, explores sky areas that were observed more than once by xmm-newton. these observations are bundled in groups referred to as stacks. stacking leads to a higher sensitivity, resulting in newly discovered sources and better constrained source parameters, and unveils long-term brightness variations.methods: the 4xmm-dr9s catalogue was constructed from simultaneous source detection on overlapping observations. as a novel feature, positional rectification was applied beforehand. observations with all filters and suitable camera settings were included. exposures with a high background were discarded. the high-background thresholds were determined through a statistical analysis of all exposures in each instrument configuration. the x-ray background maps used in source detection were modelled via an adaptive smoothing procedure with newly determined parameters. source fluxes were derived for all contributing observations, irrespective of whether the source would be detectable in an individual observation.results: the new catalogue lists the x-ray sources detected in 1329 stacks with 6604 contributing observations over repeatedly covered 300 square degrees in the sky. most stacks are composed of two observations, the largest one comprises 352 observations. we find 288 191 sources of which 218 283 were observed several times. the number of observations of a source ranges from 1 to 40. auxiliary products, like x-ray full-band and false-colour images, long-term x-ray light curves, and optical finding charts, are published as well.conclusions: 4xmm-dr9s contains new detections and is considered a prime resource to explore long-term variability of x-ray sources discovered by xmm-newton. regular incremental releases, including new public observations, are planned. the catalogue is available in fits format via the ssc web pages at http://xmmssc.irap.omp.eu and https://xmmssc.aip.de and at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/641/a137, xsa https://www.cosmos.esa.int/web/xmm-newton/xsa, and heasarc https://heasarc.gsfc.nasa.gov/w3browse/xmm-newton/xmmstack.html data services. based on observations obtained with xmm-newton, an esa science mission with instruments and contributions directly funded by esa member states and nasa. | the xmm-newton serendipitous survey. x. the second source catalogue from overlapping xmm-newton observations and its long-term variable content |
feeding and feedback of active galactic nuclei (agns) are critical for understanding the dynamics and thermodynamics of the intracluster medium (icm) within the cores of galaxy clusters. although radio bubbles inflated by agn jets could be dynamically supported by cosmic rays (crs), the impact of cr-dominated jets is not well understood. in this work, we perform three-dimensional simulations of cr-jet feedback in an isolated cluster atmosphere; we find that cr jets impact the multiphase gas differently than jets dominated by kinetic energy. in particular, cr bubbles can more efficiently uplift the cluster gas and cause an outward expansion of the hot icm. due to adiabatic cooling from the expansion and less efficient heating from cr bubbles by direct mixing, the icm is more prone to local thermal instabilities, which will later enhance chaotic cold accretion onto the agn. the amount of cold gas formed during the bubble formation and its late-time evolution sensitively depend on whether or not cr transport processes are included. we also find that low-level, subsonic driving of turbulence by agn jets holds for both kinetic and cr jets; nevertheless, the kinematics is consistent with the hitomi measurements. finally, we carefully discuss the key observable signatures of each bubble model, focusing on gamma-ray emission (and related comparison with fermi), as well as thermal sunyaev-zel’dovich constraints. | the impact of radio agn bubble composition on the dynamics and thermal balance of the intracluster medium |
we use the cosmo-overwhelmingly large simulation (cosmo-owls) suite of cosmological hydrodynamical simulations to investigate the scatter and evolution of the global hot gas properties of large simulated populations of galaxy groups and clusters. our aim is to compare the predictions of different physical models and to explore the extent to which commonly adopted assumptions in observational analyses (e.g. self-similar evolution) are violated. we examine the relations between (true) halo mass and the x-ray temperature, x-ray luminosity, gas mass, sunyaev-zel'dovich (sz) flux, the x-ray analogue of the sz flux (yx) and the hydrostatic mass. for the most realistic models, which include active galactic nuclei (agn) feedback, the slopes of the various mass-observable relations deviate substantially from the self-similar ones, particularly at late times and for low-mass clusters. the amplitude of the mass-temperature relation shows negative evolution with respect to the self-similar prediction (i.e. slower than the prediction) for all models, driven by an increase in non-thermal pressure support at higher redshifts. the agn models predict strong positive evolution of the gas mass fractions at low halo masses. the sz flux and yx show positive evolution with respect to self-similarity at low mass but negative evolution at high mass. the scatter about the relations is well approximated by log-normal distributions, with widths that depend mildly on halo mass. the scatter decreases significantly with increasing redshift. the exception is the hydrostatic mass-halo mass relation, for which the scatter increases with redshift. finally, we discuss the relative merits of various hot gas-based mass proxies. | the scatter and evolution of the global hot gas properties of simulated galaxy cluster populations |
we delineate the allowed parameter and mass range for a wino-like dark matter particle containing some higgsino admixture in the mssm by analysing the constraints from diffuse gamma-rays from the dwarf spheroidal galaxies, galactic cosmic rays, direct detection and cosmic microwave background anisotropies. a complete calculation of the sommerfeld effect for the mixed-neutralino case is performed. we find that the combination of direct and indirect searches poses significant restrictions on the thermally produced wino-higgsino dark matter with correct relic density. for μ > 0 nearly the entire parameter space considered is excluded, while for μ < 0 a substantial region is still allowed, provided conservative assumptions on astrophysical uncertainties are adopted. | the last refuge of mixed wino-higgsino dark matter |
recent observations in the total luminosity density have led to significant progress in establishing the star formation rate (sfr) at high redshift. concurrently observed gamma-ray burst rates have also been used to extract the sfr at high redshift. the sfr in turn can be used to make a host of predictions concerning the ionization history of the universe, the chemical abundances, and supernova rates. we compare the predictions made using a hierarchical model of cosmic chemical evolution based on three recently proposed sfrs: two based on extracting the sfr from the observed gamma-ray burst rate at high redshift, and one based on the observed galaxy luminosity function at high redshift. using the wmap/planck data on the optical depth and epoch of reionization, we find that only the sfr inferred from gamma-ray burst data at high redshift suffices to allow a single mode (in the initial mass function - imf) of star formation which extends from z = 0 to redshifts >10. for the case of the sfr based on the observed galaxy luminosity function, the reionization history of the universe requires a bimodal imf which includes at least a coeval high- (or intermediate-) mass mode of star formation at high redshift (z > 10). therefore, we also consider here a more general bimodal case which includes an early-forming high-mass mode as a fourth model to test the chemical history of the universe. we conclude that observational constraints on the global metallicity and optical depth at high redshift favour unseen faint but active star-forming galaxies as pointed out in many recent studies. | the impact of star formation and gamma-ray burst rates at high redshift on cosmic chemical evolution and reionization |
the galactic center’s giant outflows are manifest in three different, nonthermal phenomena: (1) the hard-spectrum, γ-ray “fermi bubbles” emanating from the nucleus and extending to | b| ∼ 50^\circ ; (2) the hard-spectrum, total-intensity microwave (∼20-40 ghz) “haze” extending to | b| ∼ 35^\circ in the lower reaches of the fermi bubbles; and (3) the steep-spectrum, polarized, “s-pass” radio (∼2-20 ghz) lobes that envelop the bubbles and extend to | b| ∼ 60^\circ . we find that the nuclear outflows inflate a genuine bubble in each galactic hemisphere that has the classical structure, working outward, of reverse shock, contact discontinuity (cd), and forward shock. expanding into the finite pressure of the halo and given appreciable cooling and gravitational losses, the cd of each bubble is now expanding only very slowly. we find observational signatures in both hemispheres of giant, reverse shocks at heights of ∼1 kpc above the nucleus; their presence ultimately explains all three of the nonthermal phenomena mentioned above. synchrotron emission from shock-reaccelerated cosmic-ray electrons explains the spectrum, morphology, and vertical extent of the microwave haze and the polarized radio lobes. collisions between shock-reaccelerated hadrons and denser gas in cooling condensations that form inside the cd account for most of the bubbles’ γ-ray emissivity. inverse compton emission from primary electrons contributes at the 10%-30% level. our model suggests that the bubbles are signatures of a comparatively weak but sustained nuclear outflow driven by galactic center star formation over ≳few × 108 yr. | a unified model of the fermi bubbles, microwave haze, and polarized radio lobes: reverse shocks in the galactic center’s giant outflows |
recently, the direct detection of gravitational waves from black hole (bh) mergers was announced by the advanced ligo collaboration. multi-messenger counterparts of stellar-mass bh mergers are of interest, and it had been suggested that a small disk or celestial body may be involved in the binary of two bhs. to test such possibilities, we consider the fate of a wind powered by an active minidisk in a relatively short, super-eddington accretion episode onto a bh with ∼10-100 solar masses. we show that its thermal emission could be seen as a fast optical transient with the duration from hours to days. we also find that the coasting outflow forms external shocks due to interaction with the interstellar medium, whose synchrotron emission might be expected in the radio band on a timescale of years. finally, we also discuss a possible jet component and the associated high-energy neutrino emission as well as ultra-high-energy cosmic-ray acceleration. | ultrafast outflows from black hole mergers with a minidisk |
context. low-energy cosmic rays (<1 tev) play a fundamental role in the chemical and dynamical evolution of molecular clouds, as they control the ionisation, dissociation, and excitation of h2. their characterisation is therefore important both for the interpretation of observations and for the development of theoretical models. however, the methods used so far for estimating the cosmic-ray ionisation rate in molecular clouds have several limitations due to uncertainties in the adopted chemical networks.aims: we refine and extend a previously proposed method to estimate the cosmic-ray ionisation rate in molecular clouds by observing rovibrational transitions of h2 at near-infrared wavelengths, which are mainly excited by secondary cosmic-ray electrons.methods: combining models of interstellar cosmic-ray propagation and attenuation in molecular clouds with the rigorous calculation of the expected secondary electron spectrum and updated electron-h2 excitation cross sections, we derive the intensity of the four h2 rovibrational transitions observable in cold dense gas: (1−0)o(2), (1−0)q(2), (1−0)s(0), and (1−0)o(4).results: the proposed method allows the estimation of the cosmic-ray ionisation rate for a given observed line intensity and h2 column density. we are also able to deduce the shape of the low-energy cosmic-ray proton spectrum impinging upon the molecular cloud. in addition, we present a look-up plot and a web-based application that can be used to constrain the low-energy spectral slope of the interstellar cosmic-ray proton spectrum. we finally comment on the capability of the james webb space telescope to detect these near-infrared h2 lines, which will make it possible to derive, for the first time, spatial variation in the cosmic-ray ionisation rate in dense gas. besides the implications for the interpretation of the chemical-dynamic evolution of a molecular cloud, it will finally be possible to test competing models of cosmic-ray propagation and attenuation in the interstellar medium, as well as compare cosmic-ray spectra in different galactic regions. | cosmic rays in molecular clouds probed by h2 rovibrational lines. perspectives for the james webb space telescope |
the sky at mev energies is currently poorly explored. here we present an innovative mission concept that builds upon the heritage of past and current missions improving the sensitivity and, very importantly, the angular resolution. this consists in combining a compton telescope and a coded-mask telescope. we delineate the motivation for such a concept and we define the scientific goals for such a mission. the galactic explorer with a coded aperture mask compton telescope (gecco) is a novel concept for a next-generation telescope covering hard x-ray and soft gamma-ray energies. the potential and importance of this approach that bridges the observational gap in the mev energy range are presented. with the unprecedented angular resolution of the coded mask telescope combined with the sensitive compton telescope, a mission such as gecco can disentangle the discrete sources from the truly diffuse emission. individual galactic and extragalactic sources are detected. this also allows to understand the gamma-ray galactic center excess and the fermi bubbles, and to trace the low-energy cosmic rays, and their propagation in the galaxy. nuclear and annihilation lines are spatially and spectrally resolved from the continuum emission and from sources, addressing the role of low-energy cosmic rays in star formation and galaxy evolution, the origin of the 511 kev positron line, fundamental physics, and the chemical enrichment in the galaxy. such an instrument also detects explosive transient gamma-ray sources, which, in turn, enables identifying and studying the astrophysical objects that produce gravitational waves and neutrinos in a multi-messenger context. by looking at a poorly explored energy band it also allows discoveries of new astrophysical phenomena. | exploring the mev sky with a combined coded mask and compton telescope: the galactic explorer with a coded aperture mask compton telescope (gecco) |
arti is a complete framework designed to simulate the signals produced by the secondary particles emerging from the interaction of single, multiple, and even from the complete flux of primary cosmic rays with the atmosphere. these signals are simulated for any particle detector located at any place (latitude, longitude and altitude), including the real-time atmospheric, geomagnetic and detector conditions. formulated through a sequence of codes written in c++, fortran, bash and perl, it provides an easy-to-use integration of three different simulation environments: magnetocosmics, corsika and geant4. these tools evaluate the geomagnetic field effects on the primary flux and simulate atmospheric showers of cosmic rays and the detectors' response to the secondary flux of particles. in this work, we exhibit the usage of the arti framework by calculating the total expected signal flux at eight selected sites of the latin american giant observatory: a cosmic ray observatory all over latin america covering a wide range of altitudes, latitudes and geomagnetic rigidities. arti will also calculate the signal flux expected during the sudden occurrence of a gamma-ray burst or the flux of energetic photons originating from steady gamma sources. it also compares these fluxes with the expected background when they are detected in a single water cherenkov detector deployed in a high-altitude site. furthermore, by using arti, it is possible to calculate in a very precise way the expected flux of high-energetic muons and other secondaries at the ground level and to inject them through geological structures for muography applications. | the arti framework: cosmic rays atmospheric background simulations |
the theory of gravitational lensing has revealed many generic and fundamental properties of compact objects like black holes and wormholes. in this article, we utilize a recent formulation to compute the quantum effects on the deflection angle of a light ray, namely, the gauss-bonnet theorem (gbt) to explore the semiclassical gravitational effects in the spacetime of a point-like global monopole and a cosmic string. previously, the gauss-bonnet theorem (gibbons and werner, 2008) was proposed as an alternative way to compute the deflection angle of light in a static, spherically symmetric and asymptotically flat spacetime. in the present article we have used the celebrated gbt that applied to the optical metric as well as the geodesic method in computing the deflection angle. interestingly one can observe that we have found an exact result between gbt and the standard approach up to the third-order contributions terms by modifying the domain of integration for cosmic string and global monopole deflection angles. finally we have considered the time delay in the cosmic string/global monopole spacetime and found that the delay in time is proportional to the linear mass density of the cosmic string and global monopole parameter, respectively. | semiclassical gravitational effects on the gravitational lensing in the spacetime of topological defects |
the standard approach to cosmic-ray (cr) propagation in the galaxy is based on the assumption that local transport properties can be extrapolated to the whole cr confining volume. such models tend to underestimate the γ -ray flux above a few gev measured by the fermi large area telescope toward the inner galactic plane. we consider here for the first time a phenomenological scenario allowing for both the rigidity scaling of the diffusion coefficient and the convective effects to be position dependent. we show that within this approach we can reproduce the observed γ -ray spectra at both low and mid galactic latitudes—including the galactic center—without spoiling any local cr observable. | gamma-ray sky points to radial gradients in cosmic-ray transport |
very recently, diffuse gamma-rays with 0.1 pev < eγ < 1 pev have been discovered from the galactic disk by the tibet air shower array and muon detector array (tibet as+md array). while the measured sub-pev flux may be compatible with the hadronic origin in the conventional galactic cosmic-ray propagation model, we find that it is in possible tension with the nondetection of galactic neutrino emissions by the icecube neutrino telescope. we further find that the presence of an extra cosmic-ray component of relatively hard spectrum, which is probably related to the cygnus cocoon region and other pev cosmic-ray sources in the galactic disk, would alleviate the tension. this scenario implies the existence of an extreme accelerator of either protons or electrons beyond pev in the cygnus region, and predicts the continuation of the gamma-ray spectrum of cygnus cocoon up to 1 pev with a possible hardening beyond ∼30-100 tev. | origin of galactic sub-pev diffuse gamma-ray emission: constraints from high-energy neutrino observations |
galactic sites of acceleration of cosmic rays to energies of order 1015 ev and higher, dubbed pevatrons, reveal themselves by recently discovered gamma radiation of energies above 100 tev. however, joint gamma-ray and neutrino production, which marks unambiguously cosmic-ray interactions with ambient matter and radiation, was not observed until now. in 2020 november, the icecube neutrino observatory reported an ~150 tev neutrino event from the direction of one of the most promising galactic pevatrons, the cygnus cocoon. here we report on the observation of a 3.1σ (post-trial) excess of atmospheric air showers from the same direction, observed by the carpet-2 experiment and consistent with a few months flare in photons above 300 tev, in temporal coincidence with the neutrino event. the fluence of the gamma-ray flare is of the same order as that expected from the neutrino observation, assuming the standard mechanism of neutrino production. this is the first evidence for the joint production of high-energy neutrinos and gamma-rays in a galactic source. | observation of photons above 300 tev associated with a high-energy neutrino from the cygnus region |
we present results from suzaku key project observations of the virgo cluster, the nearest galaxy cluster to us, mapping its x-ray properties along four long 'arms' extending beyond the virial radius. the entropy profiles along all four azimuths increase with radius, then level out beyond ∼0.5r200, while the average pressure at large radii exceeds planck sunyaev-zel'dovich measurements. these results can be explained by enhanced gas density fluctuations (clumping) in the cluster's outskirts. using a standard navarro, frenk and white model, we estimate a virial mass, radius and concentration parameter of m200 = 1.05 ± 0.02 × 1014 m⊙, r200 = 974.1 ± 5.7 kpc and c = 8.8 ± 0.2, respectively. the inferred cumulative baryon fraction exceeds the cosmic mean at r ∼ r200 along the major axis, suggesting enhanced gas clumping possibly sourced by a candidate large-scale structure filament along the north-south direction. the suzaku data reveal a large-scale sloshing pattern, with two new cold fronts detected at radii of 233 and 280 kpc along the western and southern arms, respectively. two high-temperature regions are also identified 1 mpc towards the south and 605 kpc towards the west of m87, likely representing shocks associated with the ongoing cluster growth. although systematic uncertainties in measuring the metallicity for low-temperature plasma remain, the data at large radii appear consistent with a uniform metal distribution on scales of ∼90 × 180 kpc and larger, providing additional support for the early chemical enrichment scenario driven by galactic winds at redshifts of 2-3. | witnessing the growth of the nearest galaxy cluster: thermodynamics of the virgo cluster outskirts |
the lisa pathfinder charge management device was responsible for neutralizing the cosmic-ray-induced electric charge that inevitably accumulated on the free-falling test masses at the heart of the experiment. we present measurements made on ground and in flight that quantify the performance of this contactless discharge system which was based on photoemission under uv illumination. in addition, a two-part simulation is described that was developed alongside the hardware. modeling of the absorbed uv light within the pathfinder sensor was carried out with the geant4 software toolkit and a separate matlab charge transfer model calculated the net photocurrent between the test masses and surrounding housing in the presence of ac and dc electric fields. we confront the results of these models with observations and draw conclusions for the design of discharge systems for future experiments like lisa that will also employ free-falling test masses. | precision charge control for isolated free-falling test masses: lisa pathfinder results |
a hypernucleus, a subatomic bound system with at least one hyperon, is a great test ground to investigate nuclear forces and general baryonic interactions with up, down and strange quarks. hypernuclei have been extensively studied for almost seven decades in reactions involving cosmic rays and with accelerator beams. in recent years, experimental studies of hypernuclei have entered a new stage using energetic collisions of heavy-ion beams. however, these investigations have revealed two puzzling results related to the lightest three-body hypernuclear system, the so-called hypertriton, and the unexpected existence of a bound state of two neutrons with a λ hyperon. solving these puzzles will not only impact our understanding of the fundamental baryonic interactions with strange quarks but also of the nature of the deep interior of neutron stars. in this perspective, we discuss approaches to solving these puzzles, including experiments with heavy-ion beams and the analysis of nuclear emulsions using state-of-the-art technologies. we summarize ongoing projects and experiments at various facilities worldwide and outline future perspectives. | new directions in hypernuclear physics |
supernova remnants (snrs) in the galaxy are an important source of energy injection into the interstellar medium, and also of cosmic rays. currently there are 294 known snrs in the galaxy, and their distribution with galactocentric radius is of interest for various studies. here i discuss some of the statistics of galactic snrs, including the observational selection effects that apply, and difficulties in obtaining distances for individual remnants from the σ-d relation. comparison of the observed galactic longitude distribution of a sample of bright galactic snrs - which are not strongly affected by selection effects - with those expected from models is used to constrain the galactic distribution of snrs. the best-fitting power-law/exponential model is more concentrated towards the galactic centre than the widely used distribution obtained by case & bhattacharya. | constraints on the distribution of supernova remnants with galactocentric radius |
the radiation risk radiometer-dosimeter (r3d)-r2 solid-state detector performed radiation measurements at the european space agency expose-r2 platform outside of the russian "zvezda" module at the international space station (iss) from 24 october 2014 to 11 january 2016. the iss orbital parameters were average altitude of 415 km and 51.6° inclination. we developed special software and used experimentally obtained formulas to determine the radiation flux-to-dose ratio from the r3dr2 liulin-type deposited-energy spectrometer. we provide for the first time simultaneous, long-term estimates of radiation dose external to the iss for four source categories: (i) galactic cosmic ray particles and their secondary products; (ii) protons in the south atlantic anomaly region of the inner radiation belt (irb); (iii) relativistic electrons and/or bremsstrahlung in the outer radiation belt (orb); and (iv) solar energetic particle (sep) events. the latter category is new in this study. additionally, in this study, secondary particles (sp) resulting from energetic particle interaction with the detector and nearby materials are identified. these are observed continuously at high latitudes. the detected sps are identified using the same sorting requirements as sep protons. the irb protons provide the highest consistent hourly dose, while the orb electrons and seps provide the most extreme hourly doses. seps were observed 11 times during the study interval. the r3dr2 data support calculation of average equivalent doses. the 30 day and 1 year average equivalent doses are much smaller than the skin and eyes doses recommendations by the national council on radiation protection (report 132), which provides radiation protection guidance for low earth orbit. | overview of the iss radiation environment observed during the esa expose-r2 mission in 2014-2016 |
the high altitude water cherenkov (hawc) gamma-ray observatory is a wide field-of-view observatory sensitive to 500 gev - 100 tev gamma rays and cosmic rays. with its observations over 2/3 of the sky every day, the hawc observatory is sensitive to a wide variety of astrophysical sources, including possible gamma rays from dark matter. dark matter annihilation and decay in the milky way galaxy should produce gamma-ray signals across many degrees on the sky. the hawc instantaneous field-of-view of 2 sr enables observations of extended regions on the sky, such as those from dark matter in the galactic halo. here we show limits on the dark matter annihilation cross-section and decay lifetime from hawc observations of the galactic halo with 15 months of data. these are some of the most robust limits on tev and pev dark matter, largely insensitive to the dark matter morphology. these limits begin to constrain models in which pev icecube neutrinos are explained by dark matter which primarily decays into hadrons. | a search for dark matter in the galactic halo with hawc |
the dampe experiment has recently reported strong indications for the existence of an excess of high-energy electrons and positrons. if interpreted in terms of the annihilation of dark matter, the dampe result restricts the dark matter mass and possible annihilation channels to a few case. in this paper we explain the dampe result with the electron-flavored $z^\prime$-portal fermionic dark matter. we show that the dirac dark matter scenario is promising to explain the excess via the process $\bar \chi \chi \to\mathbf{z}'\to \bar e e$. the reduced annihilation cross section is limited in a range of $10^{-26}\sim 10^{-24}~{\rm cm^3 s^{-1}}$ to interpret the excess. | the electron-flavored z'-portal dark matter and the dampe cosmic ray excess |
the escape process of particles accelerated at supernova remnant (snr) shocks is one of the poorly understood aspects of the shock acceleration theory. here we adopt a phenomenological approach to study the particle escape and its impact on the gamma-ray spectrum resulting from hadronic collisions both inside and outside of a middle-aged snr. under the assumption that in the spatial region immediately outside of the remnant the diffusion coefficient is suppressed with respect to the average galactic one, we show that a significant fraction of particles are still located inside the snr long time after their nominal release from the acceleration region. this fact results into a gamma-ray spectrum that resembles a broken power law, similar to those observed in several middle-aged snrs. above the break, the spectral steepening is determined by the diffusion coefficient outside of the snr and by the time dependence of maximum energy. consequently, the comparison between the model prediction and actual data will contribute to determining these two quantities, the former being particularly relevant within the predictions of the gamma-ray emission from the halo of escaping particles around snrs, which could be detected with future cherenkov telescope facilities. we also calculate the spectrum of runaway particles injected into the galaxy by an individual remnant. assuming that the acceleration stops before the snr enters the snowplow phase, we show that the released spectrum can be a featureless power law only if the accelerated spectrum is ∝ p-α with α > 4. | exploring particle escape in supernova remnants through gamma rays |
we use n-body simulations to study the dynamical evolution of population iii (pop iii) stellar systems and the resulting binary statistics. we design a physically motivated framework for the initial conditions of pop iii star clusters, based on small-scale hydrodynamic simulations and the scale-free nature of disc evolution during pop iii star formation. our novel approach enables us to explore the dependence of binary statistics on initial conditions and arrive at more robust predictions for the signals of pop iii x-ray binaries (xrbs) and binary black hole (bbh) mergers, compared to simple extrapolations of pop iii protostar systems. we find that binary properties are highly sensitive to the initial cluster size and distribution of binary separation, while the effect of initial mass function is relatively minor. our simulations predict less close binaries, and thus, significantly lower efficiencies (by a factor of ∼10-104) for the formation and accretion of pop iii xrbs, than found in previous studies, implying that the contribution of pop iii xrbs to the cosmic x-ray background is negligible and their feedback effects are unimportant. we estimate the efficiency of pop iii bbh mergers as $\sim 10^{-5}\!-\!10^{-4}\ \rm m_{\odot }^{-1}$ , for which three-body hardening by surrounding stars in dense star clusters or close binary interactions is required to facilitate in-spirals of bbhs. all simulation data, including catalogues of pop iii binaries and multiple systems, are publicly available. | dynamical evolution of population iii stellar systems and the resulting binary statistics |
the recent discovery of the electromagnetic counterpart of the gravitational wave source gw170817, has demonstrated the huge informative power of multi-messenger observations. during the next decade the nascent field of multi-messenger astronomy will mature significantly. around 2030 and beyond, third generation ground-based gravitational wave detectors will be roughly ten times more sensitive than the current ones. at the same time, neutrino detectors currently upgrading to multi km3 telescopes, will include a 10 km3 facility in the southern hemisphere. in this review, we describe the most promising sources of high frequency gravitational waves and neutrinos that will be detected in the next two decades. in this context, we show the important role of the transient high energy sky and early universe surveyor (theseus), a mission concept accepted by esa for phase a study and proposed by a large international collaboration in response to the call for the cosmic vision programme m5 missions. theseus aims at providing a substantial advancement in early universe science as well as in multi-messenger and time-domain astrophysics, operating in strong synergy with future gravitational wave and neutrino detectors as well as major ground- and space-based telescopes. this review is an extension of the theseus white paper (amati et al., 2017), also in light of the discovery of gw170817/grb170817a that was announced on october 16th, 2017. | theseus: a key space mission concept for multi-messenger astrophysics |
modelling the transport of cosmic rays (crs) in the heliosphere represents a global challenge in the field of heliophysics, in that such a study, if it were to be performed from first principles, requires the careful modelling of both large scale heliospheric plasma quantities (such as the global structure of the heliosphere, or the heliospheric magnetic field) and small scale plasma quantities (such as various turbulence-related quantities). here, recent advances in our understanding of the transport of galactic cosmic rays are reviewed, with an emphasis on new developments pertaining to their transport coefficients, with a special emphasis on novel theoretical and numerical simulation results, as well as the cr transport studies that employ them. furthermore, brief reviews are given of recent progress in cr focused transport modelling, as well as the modelling of non-diffusive cr transport. | theory of cosmic ray transport in the heliosphere |
recent progress of dating techniques has greatly improved the age determination of various types of landslides. since the turn of the 21st century, the number of dated landslides throughout the world has increased several fold and the introduction of modern dating methods (e.g. cosmic ray exposure dating) has enabled the dating of new landslide features and elements. based on the analysis of >950 dated landslides (of which 734 have been dated since the year 2000), it is clear that the predominant traditional strategies have continued to rely on the radiocarbon method; however, there is a remarkable trend of using cosmic ray exposure techniques for dating both the accumulation (e.g. landslide boulders) and the depletion (e.g. landslide scarps) parts of landslides. furthermore, an increasing number of slope failures is determined by a multi-dating approach, which enables the verification of particular dating methods. although coherent regional landslide chronologies are still relatively scarce in comparison with extensive databases of fluvial, glacial and/or eolian landforms, they offer important insights into temporal landslide distribution, long-term landslide behavior and their relationships with paleoenvironmental changes. the most extensive data sets exist for the mountain areas of north america (pacific coast ranges), south america (andes), europe (alps, scottish highlands, norway, carpathians and apennines), the himalaya-tibet orogeny and the southern alps of new zealand. dated landslides in the plate interiors are lacking, especially in south america, africa and australia. despite the fact that some dating results are well correlated with major regional and continental-scale changes in the seismic activity, moisture abundance, glacier regimes and vegetation patterns, some of these results contradict previously established straightforward hypotheses. this indicates the rather complex chronological behavior of landslides, reflecting both intrinsic (e.g. gradual stress relaxation within a rock mass) and external factors, including high-magnitude earthquakes or heavy rainfalls. | recent progress in landslide dating |
the aim of this research is to improve our current understanding of the deglaciation stages in the southeastern pyrenees and integrate it into reconstructions of the long‑term deglaciation in the iberian mountains since the last glaciation. first, we examine the existing chronological data for deglaciation in iberian mountain ranges, mainly focusing on the pyrenees and the results derived from cosmic ray exposure dating methods. then, we recalculate the age of 17 samples from four different areas in the se pyrenees (arànser, la llosa and duran valleys and malniu‑guils complex) based on the 36cl isotope and applying a new age calculator. in addition, we date eight new samples from the malniu‑guils complex to provide a more accurate chronology for this site. the results do not clarify the timing of the maximum glacier extent, but support an extensive glacial advance followed by multiple small advances and retreats during the last glacial maximum (lgm). geomorphological and chronological data show evidence of massive deglaciation at the end of the lgm around 18 ka, and deglaciation was practically complete during the bølling‑allerød interstadial. there is no geomorphological evidence of glacial advances in the cirques during the younger dryas. instead, cirque walls were covered with rock glaciers during the bølling‑allerød interstadial. the fronts of these rock glaciers stabilized at the end of this period, while their roots remained active until well into the holocene. | timing of deglaciation and rock glacier origin in the southeastern pyrenees: a review and new data |
as is well known, dark matter direct detection experiments will ultimately be limited by a "neutrino floor," due to the scattering of nuclei by mev neutrinos from, e.g., nuclear fusion in the sun. here we point out the existence of a new neutrino floor that will similarly limit indirect detection with the sun, due to high-energy neutrinos from cosmic-ray interactions with the solar atmosphere. we have two key findings. first, solar atmospheric neutrinos ≲1 tev cause a sensitivity floor for standard weakly interacting massive particles (wimp) scenarios, for which higher-energy neutrinos are absorbed in the sun. this floor will be reached once the present sensitivity is improved by just 1 order of magnitude. second, for neutrinos ≳1 tev , which can be isolated by muon energy loss rate, solar atmospheric neutrinos should soon be detectable in icecube. discovery will help probe the complicated effects of solar magnetic fields on cosmic rays. these events will be backgrounds to wimp scenarios with long-lived mediators, for which higher-energy neutrinos can escape from the sun. | solar atmospheric neutrinos: a new neutrino floor for dark matter searches |
in this work we are reporting on the measurement of the proton-air inelastic cross section σp-air inel using the telescope array detector. based on the measurement of the σp-air inel, the proton-proton cross section σp -p value is also determined at √{s }=9 5-8+5 tev . detecting cosmic ray events at ultrahigh energies with the telescope array enables us to study this fundamental parameter that we are otherwise unable to access with particle accelerators. the data used in this report are the hybrid events observed by the middle drum fluorescence detector together with the surface array detector collected over five years. the value of the σp-air inel is found to be equal to 567.0 ±70.5 [stat]-25+29[sys] mb . the total proton-proton cross section is subsequently inferred from glauber formalism and the block, halzen and stanev qcd inspired fit and is found to be equal to 17 0-44+48[stat]-17+19[sys] mb . | measurement of the proton-air cross section with telescope array's middle drum detector and surface array in hybrid mode |
axion strings are horizon-size topological defects that may be produced in the early universe. ultra-light axion-like particles may form strings that persist to temperatures below that of big bang nucleosynthesis. such strings have been considered previously as sources of gravitational waves and cosmic microwave background (cmb) polarization rotation. in this work we show, through analytic arguments and dedicated adaptive mesh refinement cosmological simulations, that axion strings deposit a sub-dominant fraction of their energy into high-energy standard model (sm) final states, for example, by the direct production of heavy radial modes that subsequently decay to sm particles. this high-energy sm radiation is absorbed by the primordial plasma, leading to novel signatures in precision big bang nucleosynthesis, the cmb power spectrum, and gamma-ray surveys. in particular, we show that cmb power spectrum data constrains axion strings with decay constants $f_a \lesssim 10^{12}$ gev, up to model dependence on the ultraviolet completion, for axion masses $m_a \lesssim 10^{-29}$ ev; future cmb surveys could find striking evidence of axion strings with lower decay constants. | signatures of primordial energy injection from axion strings |
the presence of relativistic electrons within the diffuse gas phase of galaxy clusters is now well established, thanks to deep radio observations obtained over the last decade, but their detailed origin remains unclear. cosmic ray protons are also expected to accumulate during the formation of clusters. they may explain part of the radio signal and would lead to γ-ray emission through hadronic interactions within the thermal gas. recently, the detection of γ-ray emission has been reported toward the coma cluster with fermi-lat. assuming that this γ-ray emission arises essentially from pion decay produced in proton-proton collisions within the intracluster medium (icm), we aim at exploring the implication of this signal on the cosmic ray content of the coma cluster and comparing it to observations at other wavelengths. we use the minot software to build a physical model of the coma cluster, which includes the thermal target gas, the magnetic field strength, and the cosmic rays, to compute the corresponding expected γ-ray signal. we apply this model to the fermi-lat data using a binned likelihood approach, together with constraints from x-ray and sunyaev-zel'dovich observations. we also consider contamination from compact sources and the impact of various systematic effects on the results. we confirm that a significant γ-ray signal is observed within the characteristic radius θ500 of the coma cluster, with a test statistic ts ≃ 27 for our baseline model. the presence of a possible point source (4fgl j1256.9+2736) may account for most of the observed signal. however, this source could also correspond to the peak of the diffuse emission of the cluster itself as it is strongly degenerate with the expected icm emission, and extended models match the data better. given the fermi-lat angular resolution and the faintness of the signal, it is not possible to strongly constrain the shape of the cosmic ray proton spatial distribution when assuming an icm origin of the signal, but preference is found in a relatively flat distribution elongated toward the southwest, which, based on data at other wavelengths, matches the spatial distribution of the other cluster components well. assuming that the whole γ-ray signal is associated with hadronic interactions in the icm, we constrain the cosmic ray to thermal energy ratio within r500 to xcrp = 1.79−0.30+1.11% and the slope of the energy spectrum of cosmic rays to α = 2.80−0.13+0.67 (xcrp = 1.06−0.22+0.96% and α = 2.58−0.09+1.12 when including both the cluster and 4fgl j1256.9+2736 in our model). finally, we compute the synchrotron emission associated with the secondary electrons produced in hadronic interactions assuming steady state. this emission is about four times lower than the overall observed radio signal (six times lower when including 4fgl j1256.9+2736), so that primary cosmic ray electrons or reacceleration of secondary electrons is necessary to explain the total emission. we constrain the amplitude of the primary to secondary electrons, or the required boost from reacceleration with respect to the steady state hadronic case, depending on the scenario, as a function of radius. our results confirm that γ-ray emission is detected in the direction of the coma cluster. assuming that the emission is due to hadronic interactions in the intracluster gas, they provide the first quantitative measurement of the cosmic ray proton content in a galaxy cluster and its implication for the cosmic ray electron populations. | γ-ray detection toward the coma cluster with fermi-lat: implications for the cosmic ray content in the hadronic scenario |
supernova remnants are believed to be the main sources of galactic cosmic rays (cr). within this framework, particles are accelerated at supernova remnant shocks and then released in the interstellar medium. the mechanism through which crs are released and the way in which they propagate still remain open issues. the main difficulty is the high non-linearity of the problem: crs themselves excite the magnetic turbulence that confines them close to their sources. we solve numerically the coupled differential equations describing the evolution in space and time of the escaping particles and of the waves generated through the cr streaming instability. the warm ionized and warm neutral phases of the interstellar medium are considered. these phases occupy the largest fraction of the disc volume, where most supernovae explode, and are characterized by the significant presence of neutral particles. the friction between those neutrals and ions results in a very effective wave damping mechanism. it is found that streaming instability affects the propagation of crs even in the presence of ion-neutral friction. the diffusion coefficient can be suppressed by more than a factor of ∼2 over a region of few tens of pc around the remnant. the suppression increases for smaller distances. the propagation of ≈10 gev particles is affected for several tens of kiloyears after escape, while ≈1 tev particles are affected for few kiloyears. this might have a great impact on the interpretation of gamma-ray observations of molecular clouds located in the vicinity of supernova remnants. | non-linear diffusion of cosmic rays escaping from supernova remnants - i. the effect of neutrals |
galactic cosmic rays (crs) are accelerated at the forward shocks of supernova remnants (snrs) via diffusive shock acceleration (dsa), an efficient acceleration mechanism that predicts power-law energy distributions of crs. however, observations of nonthermal snr emission imply cr energy distributions that are generally steeper than e-2, the standard dsa prediction. recent results from kinetic hybrid simulations suggest that such steep spectra may arise from the drift of magnetic structures with respect to the thermal plasma downstream of the shock. using a semi-analytic model of nonlinear dsa, we investigate the implications that these results have on the phenomenology of a wide range of snrs. by accounting for the motion of magnetic structures in the downstream, we produce cr energy distributions that are substantially steeper than e-2 and consistent with observations. our formalism reproduces both modestly steep spectra of galactic snrs (∝e-2.2) and the very steep spectra of young radio supernovae (∝e-3). | steep cosmic-ray spectra with revised diffusive shock acceleration |
the daya bay experiment consists of functionally identical antineutrino detectors immersed in pools of ultrapure water in three well-separated underground experimental halls near two nuclear reactor complexes. these pools serve both as shields against natural, low-energy radiation, and as water cherenkov detectors that efficiently detect cosmic muons using arrays of photomultiplier tubes. each pool is covered by a plane of resistive plate chambers as an additional means of detecting muons. design, construction, operation, and performance of these muon detectors are described. | the muon system of the daya bay reactor antineutrino experiment |
the 25mg(p, γ)26al reaction plays an important role in the study of cosmic 1.809 mev γ -ray as a signature of ongoing nucleosynthesis in the galaxy. at astrophysical temperature around 0.1 gk, the 25mg(p, γ)26al reaction rates are dominated by the 92 kev resonance capture process. we report a precise measurement of the 92 kev 25mg(p, γ)26al resonance in the day-one experiment at jinping underground nuclear astrophysics experiment (juna) facility in the china jinping underground laboratory (cjpl). the resonance strength and ground state feeding factor are determined to be 3.8 ± 0.3 ×10-10 ev and 0.66 ± 0.04 , respectively. the results are in agreement with those reported in the previous direct underground measurement within uncertainty, but with significantly reduced uncertainties. consequently, we recommend new 25mg(p, γ)26al reaction rates which are by a factor of 2.4 larger than those adopted in reaclib database at the temperature around 0.1 gk. the new results indicate higher production rates of 26gal and the cosmic 1.809 mev γ -ray. the implication of the new rates for the understanding of other astrophysical situations is also discussed. | first result from the jinping underground nuclear astrophysics experiment juna: precise measurement of the 92 kev 25mg(p, γ)26al resonance |
the microboone liquid argon time projection chamber (lartpc) has been taking data at fermilab since 2015 collecting, in addition to neutrino beam, cosmic-ray muons. results are presented on the reconstruction of michel electrons produced by the decay at rest of cosmic-ray muons. michel electrons are abundantly produced in the tpc, and given their well known energy spectrum can be used to study microboone's detector response to low-energy electrons (electrons with energies up to ~ 50 mev). we describe the fully-automated algorithm developed to reconstruct michel electrons, with which a sample of ~ 14,000 michel electron candidates is obtained. most of this article is dedicated to studying the impact of radiative photons produced by michel electrons on the accuracy and resolution of their energy measurement. in this energy range, ionization and bremsstrahlung photon production contribute similarly to electron energy loss in argon, leading to a complex electron topology in the tpc. by profiling the performance of the reconstruction algorithm on simulation we show that the ability to identify and include energy deposited by radiative photons leads to a significant improvement in the energy measurement of low-energy electrons. the fractional energy resolution we measure improves from over 30% to ~ 20% when we attempt to include radiative photons in the reconstruction. these studies are relevant to a large number of analyses which aim to study neutrinos by measuring electrons produced by νe interactions over a broad energy range. | michel electron reconstruction using cosmic-ray data from the microboone lartpc |
we investigated the radio continuum spectra of 14 star-forming galaxies by fitting nonthermal (synchrotron) and thermal (free-free) radiation laws. the underlying radio continuum measurements cover a frequency range of 325 mhz to 24.5 ghz (32 ghz in case of m 82). it turns out that most of these synchrotron spectra are not simple power-laws, but are best represented by a low-frequency spectrum with a mean slope αnth = 0.59 ± 0.20 (sν ∝ ν-α), and by a break or an exponential decline in the frequency range of 1-12 ghz. simple power-laws or mildly curved synchrotron spectra lead to unrealistically low thermal flux densities, and/or to strong deviations from the expected optically thin free-free spectra with slope αth = 0.10 in the fits. the break or cutoff energies are in the range of 1.5-7 gev. we briefly discuss the possible origin of such a cutoff or break. if the low-frequency spectra obtained here reflect the injection spectrum of cosmic-ray electrons, they comply with the mean spectral index of galactic supernova remnants. a comparison of the fitted thermal flux densities with the (foreground-corrected) hα fluxes yields the extinction, which increases with metallicity. the fraction of thermal emission is higher than believed hitherto, especially at high frequencies, and is highest in the dwarf galaxies of our sample, which we interpret in terms of a lack of containment in these low-mass systems, or a time effect caused by a very young starburst. | radio synchrotron spectra of star-forming galaxies |
short-lived mediators are often used to describe dark matter interactions with standard model particles. when the dark matter mass is heavier than the mass of the mediator, it may self-annihilate into short-lived mediators, and in some cases this might be the dominant annihilation channel. this scenario is known as secluded dark matter. we use fermi-lat observations of dwarf spheroidal galaxies, h.e.s.s. data from the galactic center, and planck measurements of the cosmic microwave background to constrain secluded dark matter. we explore the interplay between these experiments and we assess the impact of the mediator mass on our bounds, an often overlooked yet very important point. in particular, we exclude pair -annihilation cross-sections greater or on the order of σ v ~ 4 × 10-27 cm3/s for dark matter masses around 10 gev and greater or on the order of σ v ~ × 10-25 cm3/s for dark matter masses around a tev . our findings supersede previous constraints which use fermi-lat data, and constitute the first limits on secluded dark sectors using the h.e.s.s. telescope. we also show that one can fit tev gamma-ray observations from h.e.s.s. with secluded dark matter annihilations, with the mediator mass impacting the best-fit dark matter particle mass. our findings indicate that any assessment of secluded dark sectors in the context of indirect detection significantly depends on the choice of the mediator mass. | searching for secluded dark matter with h.e.s.s., fermi-lat, and planck |
the ams-02 collaboration has published the measurement of the cosmic antiproton to proton ratio p ¯/p and the p ¯ flux with a high precision up to ∼450 gev . in this work, we perform a systematic analysis of the secondary antiproton flux generated by the cosmic ray interaction with the interstellar gas. the uncertainties of the prediction from the cosmic ray propagation process and the hadronic interaction models are analyzed. we find the two effects may interplay with each other in the prediction. in some combinations of the propagation and hadronic interaction models the secondary p ¯ predictions give quite good fit to the ams-02 data and thus set very stringent constraint on the dark matter annihilation cross section, while in some cases the predictions would deviate from the data. especially, we find that the epos lhc hadronic model, which can fit the collider data very well, predicts a slightly lower p ¯ /p ratio than the ams-02 data at the high energy end. | systematic study on the cosmic ray antiproton flux |
the anita balloon experiment has recently observed several ∼eev cascade events at an angle below the horizon that renders any standard model (sm) interpretation unlikely as the earth is significantly opaque to all sm particles at such energies. in this paper, we study a sterile neutrino interpretation of these events, calculating the angular acceptance of cascades and the relative sensitivities of several experiments to a cascade initiated by an eev sterile neutrino. we find that anita is uniquely sensitive to this type of upward directed cascade signal over a wide portion of the sky and from the direction of the two observed events has a transient acceptance roughly equivalent to that of the icecube experiment. | sterile neutrino origin for the upward directed cosmic ray showers detected by anita |
we compare the predictions of aafrag for the spectra of secondary photons, neutrinos, electrons, and positrons produced in proton-proton collisions to those of the parametrizations of kamae et al., kelner et al. and kafexhiu et al. we find that the differences in the normalization of the photon energy spectra reach 20%-50% at intermediate values of the transferred energy fraction x , growing up to a factor of two for x →1 , while the differences in the neutrino spectra are even larger. we argue that lhcf results on the forward production of photons and neutral pions favor the use of the qgsjet-ii-04m model on which aafrag is based. the differences in the normalization have important implications in the context of multimessenger astronomy, in particular, for the prediction of neutrino fluxes, based on gamma-ray flux measurements, or regarding the inference of the cosmic ray spectrum, based on gamma-ray data. we note also that the positron-electron ratio from hadronic interactions increases with energy toward the cutoff, an effect which is missed using the average electron-positron spectrum from kelner et al. finally, we describe the publicly available python package aafragpy, which provides the secondary spectra of photons, neutrinos, electrons, and positrons. this package complements the aafrag results for protons with energies above 4 gev with previous analytical parameterizations of particle spectra for lower energy protons. | energy spectra of secondaries in proton-proton interactions |
the cross-correlation between cosmic microwave background (cmb) gravitational lensing and large-scale structure tracers will be an important cosmological probe in the coming years. quadratic estimators provide a simple and powerful (if suboptimal) way to reconstruct the cmb lensing potential and are widely used. for gaussian fields, the cross-correlation of a quadratic-estimator cmb lensing reconstruction with a tracer is exactly unbiased if the power spectra are known and consistent analytic lensing mode response functions are used. however, the bispectrum induced by non-linear large-scale structure growth and post-born lensing can introduce an additional bias term (nl(3/2)) in the cross-correlation spectrum, similar to the nl(3/2) bias in the auto-spectrum demonstrated in recent works. we give analytic flat-sky results for the cross-correlation bias using approximate models for the post-born and large-scale structure cross-bispectra, and compare with n-body simulation results using ray-tracing techniques. we show that the bias can be at the 5-15% level in all large-scale structure cross-correlations using small-scale cmb temperature lensing reconstruction, but is substantially reduced using polarization-based lensing estimators or simple foreground-projected temperature estimators. the relative magnitude of these effects is almost three times higher than in the cmb lensing auto-correlation, but is small enough that it can be modelled to sufficient precision using simple analytic models. we show that nl(3/2) effects in cross-correlation will be detected with high significance when using data of future surveys and could affect systematic effects marginalization in cosmic shear measurements mimicking galaxy intrinsic alignment. | cmb lensing reconstruction biases in cross-correlation with large-scale structure probes |
originating from neutron starneutron star or neutron starblack hole mergers, short gamma-ray bursts (sgrbs) are the first electromagnetic emitters associated with gravitational waves (gws). this association makes the determination of sgrb formation rate (fr) a critical issue. we determine the true sgrb fr and its relation to the cosmic star formation rate (sfr). this can help in determining the expected gw rate involving small mass mergers. we present nonparametric methods for the determination of the evolutions of the luminosity function (lf) and the fr using sgrbs observed by swift, without any assumptions. these are powerful tools for small samples, such as our sample of 68 sgrbs. we combine sgrbs with and without extended emission (see), assuming that both descend from the same progenitor. to overcome the incompleteness introduced by redshift measurements we use the kolmogorovsmirnov (ks) test to find flux thresholds yielding a sample of sources with a redshift drawn from the parent sample including all sources. using two subsamples of sgrbs with flux limits of 4.57 107 and 2.15 107 erg cm2 s1 with respective ks p (1, 0.9), we find a 3 evidence for luminosity evolution (le), a broken power-law lf with significant steepening at l 1050 erg s1, and an fr evolution that decreases monotonically with redshift (independent of le and the thresholds). thus, sgrbs may have been more luminous in the past with an fr delayed relative to the sfr as expected in the merger scenario. | cosmological evolution of the formation rate of short gamma-ray bursts with and without extended emission |
in nuclei of starburst galaxies (sbgs), the combination of an enhanced rate of supernova explosions and a high gas density suggests that cosmic rays (crs) can be efficiently produced, and that most of them lose their energy before escaping these regions, resulting in a large flux of secondary products, including neutrinos. although the flux inferred from an individual starburst region is expected to be well below the sensitivity of current neutrino telescopes, such sources may provide a substantial contribution to the diffuse neutrino flux measured by icecube. here, we compute the gamma-ray and neutrino flux due to sbgs based on a physical model of cr transport in a starburst nucleus, and accounting for the redshift evolution of the number density of starburst sources as inferred from recent measurements of the star formation rate. the model accounts for gamma-ray absorption both inside the sources and in the intergalactic medium. the latter process is responsible for electromagnetic cascades, which also contribute to the diffuse gamma-ray background at lower energies. the conditions for acceleration of cr protons up to energies exceeding ∼10 pev in starburst regions, necessary for the production of pev neutrinos, are investigated in a critical way. we show that starburst nuclei can account for the diffuse neutrino flux above ∼ 200 tev, thereby producing ≲ 40 per cent of the extragalactic diffuse gamma-ray background. below ∼200 tev, the flux from starburst appears to be somewhat lower than the observed one, where both the galactic contribution and the flux of atmospheric neutrinos may account for the difference. | contribution of starburst nuclei to the diffuse gamma-ray and neutrino flux |
in this paper, we present the measurement of the energy spectra of carbon and oxygen in cosmic rays based on observations with the calorimetric electron telescope on the international space station from october 2015 to october 2019. analysis, including the detailed assessment of systematic uncertainties, and results are reported. the energy spectra are measured in kinetic energy per nucleon from 10 gev /n to 2.2 tev /n with an all-calorimetric instrument with a total thickness corresponding to 1.3 nuclear interaction length. the observed carbon and oxygen fluxes show a spectral index change of ∼0.15 around 200 gev /n established with a significance >3 σ . they have the same energy dependence with a constant c /o flux ratio 0.911 ±0.006 above 25 gev /n . the spectral hardening is consistent with that measured by ams-02, but the absolute normalization of the flux is about 27% lower, though in agreement with observations from previous experiments including the pamela spectrometer and the calorimetric balloon-borne experiment cream. | direct measurement of the cosmic-ray carbon and oxygen spectra from 10 gev /n to 2.2 tev /n with the calorimetric electron telescope on the international space station |
the diffusive motion of charged particles in synthetic magnetic turbulence with different properties is investigated by using numerical simulations with unprecedented dynamical range, which allow us to ensure that both the inertial range and the long wavelength part of the turbulent spectrum are properly described. this is of particular importance in evaluating previous suggestions that parallel and perpendicular diffusion coefficients differ in their energy dependence, an assertion at odds with the many claims of universality of the d⊥ and d∥ as functions of particle energy. cases with and without an ordered magnetic field are discussed. results of the numerical simulations are compared with available theoretical models, for slab, slab/2d and isotropic turbulence. we find widespread evidence that universality is broken, and that the ratio d⊥/d∥ is not independent of energy. the implications of this finding for the physics of cosmic ray transport are discussed in depth. | novel aspects of cosmic ray diffusion in synthetic magnetic turbulence |
recent results from the pierre auger observatory suggest that nuclei heavier than protons might be present in significant amounts among ultrahigh-energy cosmic rays (uhecrs). it is therefore interesting to investigate the acceleration both protons and nuclei in relativistic jets. we calculate the acceleration of a mixed composition of cosmic rays at gamma-ray burst (grb) internal shocks, taking into account the relevant energy loss processes. 3d trajectories during the relativistic fermi cycles are simulated following previous works by niemiec & ostrowski. we use the internal shock model of daigne & mochkovitch to derive the evolution of the relevant physical quantities (magnetic fields, baryon and photon densities, shock velocity). we consider different phenomenological hypotheses about the sharing of the dissipated energy between accelerated cosmic rays, electrons and the magnetic field. for various choices of the parameters, we calculate the spectrum of cosmic rays escaping from the grb environment as well as secondary particles produced either during the acceleration or extragalactic propagation of uhecrs. only models where (i) the prompt emission represents only a small fraction of the energy dissipated at internal shocks and (ii) most of this dissipated energy is communicated to cosmic rays, are able to reproduce the magnitude of the uhecr flux observed on earth. for these models, however, the observed shape of the uhecr spectrum can be well reproduced above the ankle, with an evolution of the composition compatible with the trend suggested by auger, and associated diffuse fluxes of secondary particles which do not violate current observational limits. | uhecr acceleration at grb internal shocks |
in this white paper we introduce the imagine consortium and its scientific background, goals and structure. the purpose of the consortium is to coordinate and facilitate the efforts of a diverse group of researchers in the broad areas of the interstellar medium, galactic magnetic fields and cosmic rays, and our overarching goal is to develop more comprehensive insights into the structures and roles of interstellar magnetic fields and their interactions with cosmic rays within the context of galactic astrophysics. the ongoing rapid development of observational and numerical facilities and techniques has resulted in a widely felt need to advance this subject to a qualitatively higher level of self-consistency, depth and rigour. this can only be achieved by the coordinated efforts of experts in diverse areas of astrophysics involved in observational, theoretical and numerical work. we present our view of the present status of this research area, identify its key unsolved problems and suggest a strategy that will underpin our work. the backbone of the consortium is the interstellar magnetic field inference engine, a publicly available bayesian platform that employs robust statistical methods to explore the multi-dimensional likelihood space using any number of modular inputs. this tool will be used by the imagine consortium to develop an interpretation and modelling framework that provides the method, power and flexibility to interfuse information from a variety of observational, theoretical and numerical lines of evidence into a self-consistent and comprehensive picture of the thermal and non-thermal interstellar media. an important innovation is that a consistent understanding of the phenomena that are directly or indirectly influenced by the galactic magnetic field, such as the deflection of ultra-high energy cosmic rays or extragalactic backgrounds, is made an integral part of the modelling. the imagine consortium, which is informal by nature and open to new participants, hereby presents a methodological framework for the modelling and understanding of galactic magnetic fields that is available to all communities whose research relies on a state of the art solution to this problem. | imagine: a comprehensive view of the interstellar medium, galactic magnetic fields and cosmic rays |
in this paper we report the first close, high-resolution observations of downward-directed terrestrial gamma-ray flashes (tgfs) detected by the large-area telescope array cosmic ray observatory, obtained in conjunction with broadband vhf interferometer and fast electric field change measurements of the parent discharge. the results show that the tgfs occur during strong initial breakdown pulses (ibps) in the first few milliseconds of negative cloud-to-ground and low-altitude intracloud flashes and that the ibps are produced by a newly identified streamer-based discharge process called fast negative breakdown. the observations indicate the relativistic runaway electron avalanches (rreas) responsible for producing the tgfs are initiated by embedded spark-like transient conducting events (tces) within the fast streamer system and potentially also by individual fast streamers themselves. the tces are inferred to be the cause of impulsive sub-pulses that are characteristic features of classic ibp sferics. additional development of the avalanches would be facilitated by the enhanced electric field ahead of the advancing front of the fast negative breakdown. in addition to showing the nature of ibps and their enigmatic sub-pulses, the observations also provide a possible explanation for the unsolved question of how the streamer to leader transition occurs during the initial negative breakdown, namely, as a result of strong currents flowing in the final stage of successive ibps, extending backward through both the ibp itself and the negative streamer breakdown preceding the ibp. | observations of the origin of downward terrestrial gamma-ray flashes |
on 2017 august 17, a gravitational-wave event (gw170817) and an associated short gamma-ray burst (grb 170817a) from a binary neutron star merger had been detected. the follow-up optical/infrared observations also identified the macronova/kilonova emission (at 2017gfo). in this work, we discuss some implications of the remarkable gw170817/grb 170817a/at 2017gfo association. we show that the ∼1.7 s time delay between the gravitational-wave (gw) and grb signals imposes very tight constraints on the superluminal movement of gravitational waves (i.e., the relative departure of gw velocity from the speed of light is ≤slant 4.3× {10}-16) or the possible violation of the weak equivalence principle (i.e., the difference of the gamma-ray and gw trajectories in the gravitational field of the galaxy and the local universe should be within a factor of ∼ 3.4× {10}-9). the so-called dark matter emulators and a class of contender models for cosmic acceleration (“covariant galileon”) are ruled out as well. the successful identification of lanthanide elements in the macronova/kilonova spectrum also excludes the possibility that the progenitors of grb 170817a are a binary strange star system. the high neutron star merger rate (inferred from both the local sgrb data and the gravitational-wave data) together with the significant ejected mass strongly suggest that such mergers are the prime sites of heavy r-process nucleosynthesis. | the gw170817/grb 170817a/at 2017gfo association: some implications for physics and astrophysics |
a highly significant excess of high-energy astrophysical neutrinos has been reported by the icecube collaboration. some features of the energy and declination distributions of icecube events hint at a north/south asymmetry of the neutrino flux. this could be due to the presence of the bulk of our galaxy in the southern hemisphere. the antares neutrino telescope, located in the mediterranean sea, has been taking data since 2007. it offers the best sensitivity to muon neutrinos produced by galactic cosmic ray interactions in this region of the sky. in this letter a search for an extended neutrino flux from the galactic ridge region is presented. different models of neutrino production by cosmic ray propagation are tested. no excess of events is observed and upper limits for different neutrino flux spectral indices γ are set. for γ = 2.4 the 90% confidence level flux upper limit at 100 tev for one neutrino flavour corresponds to φ01 f (100 tev) = 2.0 ṡ10-17 gev-1cm-2s-1sr-1. under this assumption, at most two events of the icecube cosmic candidates can originate from the galactic ridge. a simple power-law extrapolation of the fermi-lat flux to account for icecube high energy starting events is excluded at 90% confidence level. | constraints on the neutrino emission from the galactic ridge with the antares telescope |
the quenching `maintenance' and related `cooling flow' problems are important in galaxies from milky way mass through clusters. we investigate this in haloes with masses ∼10^{12} - 10^{14} m_{\odot }, using non-cosmological high-resolution hydrodynamic simulations with the fire-2 (feedback in realistic environments) stellar feedback model. we specifically focus on physics present without agn, and show that various proposed `non-agn' solution mechanisms in the literature, including type ia supernovae, shocked agb winds, other forms of stellar feedback (e.g. cosmic rays), magnetic fields, spitzer-braginskii conduction, or `morphological quenching' do not halt or substantially reduce cooling flows nor maintain `quenched' galaxies in this mass range. we show that stellar feedback (including cosmic rays from sne) alters the balance of cold/warm gas and the rate at which the cooled gas within the galaxy turns into stars, but not the net baryonic inflow. if anything, outflowing metals and dense gas promote additional cooling. conduction is important only in the most massive haloes, as expected, but even at ∼10^{14} m_{\odot } reduces inflow only by a factor ∼2 (owing to saturation effects and anisotropic suppression). changing the morphology of the galaxies only slightly alters their toomre-q parameter, and has no effect on cooling (as expected), so has essentially no effect on cooling flows or maintaining quenching. this all supports the idea that additional physics, e.g. agn feedback, must be important in massive galaxies. | the failure of stellar feedback, magnetic fields, conduction, and morphological quenching in maintaining red galaxies |
traditionally, galaxy clusters have been expected to retain all the material accreted since their formation epoch. for this reason, their matter content should be representative of the universe as a whole, and thus their baryon fraction should be close to the universal baryon fraction ωb/ ωm. we make use of the sample of the 100 brightest galaxy clusters discovered in the xxl survey to investigate the fraction of baryons in the form of hot gas and stars in the cluster population. since it spans a wide range of mass (1013-1015 m⊙) and redshift (0.05-1.1) and benefits from a large set of multiwavelength data, the xxl-100-gc sample is ideal for measuring the global baryon budget of massive halos. we measure the gas masses of the detected halos and use a mass-temperature relation directly calibrated using weak-lensing measurements for a subset of xxl clusters to estimate the halo mass. we find that the weak-lensing calibrated gas fraction of xxl-100-gc clusters is substantially lower than was found in previous studies using hydrostatic masses. our best-fit relation between gas fraction and mass reads fgas,500 = 0.055-0.006+0.007(m500/1014 m⊙)0.21-0.10+0.11. the baryon budget of galaxy clusters therefore falls short of the universal baryon fraction by about a factor of two at r500,mt. our measurements require a hydrostatic bias 1-b = mx/mwl = 0.72-0.07+0.08 to match the gas fraction obtained using lensing and hydrostatic equilibrium, which holds independently of the instrument considered. comparing our gas fraction measurements with the expectations from numerical simulations, we find that our results favour an extreme feedback scheme in which a significant fraction of the baryons are expelled from the cores of halos. this model is, however, in contrast with the thermodynamical properties of observed halos, which might suggest that weak-lensing masses are overestimated. in light of these results, we note that a mass bias 1-b = 0.58 as required to reconcile planck cosmic microwave background and cluster counts should translate into an even lower baryon fraction, which poses a major challenge to our current understanding of galaxy clusters. based on observations obtained with xmm-newton, an esa science mission with instruments and contributions directly funded by esa member states and nasa.the master catalogue is available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/592/a2 | the xxl survey. xiii. baryon content of the bright cluster sample |
we report the detection of thermal sunyaev-zeldovich (sz) effect fluctuations in the intracluster medium (icm) of coma cluster observed with planck. the sz data links the maximum observable x-ray scale to the large mpc scale, extending our knowledge of the power spectrum of icm fluctuations. deprojecting the 2d sz perturbations into 3d pressure fluctuations, we find an amplitude spectrum which peaks at δp/p = 33 ± 12 and 74 ± 19 per cent in the 15 and 40 arcmin radius region, respectively. we perform tests to ensure fluctuations are intrinsic to the cluster and not due to noise contamination. by using high-resolution hydrodynamical models, we improve the icm turbulence constraints in coma, finding 3d mach number ma3d = 0.8 ± 0.3 (15 arcmin region), increasing to supersonic values at larger radii (40 arcmin) and an injection scale linj ≈ 500 kpc. such properties are consistent with driving due to mergers, in particular tied to internal galaxy groups. the large pressure fluctuations show that coma is in adiabatic mode (mediated by sound waves), rather than isobaric mode (mediated by buoyancy waves). as predicted by turbulence models, the distribution of sz fluctuations is lognormal with mild non-gaussianities (heavy tails). the substantial non-thermal pressure support implies hydrostatic mass bias bm = -15 to -45 per cent from the core to the outskirt region, respectively. while total sz power probes the thermal energy content, the sz fluctuations constrain the non-thermal deviations important for precision cosmology. the proposed, novel approach can be exploited by multifrequency observations using ground-based interferometers and future space cosmic microwave background missions. | thermal sz fluctuations in the icm: probing turbulence and thermodynamics in coma cluster with planck |
neutrinos from supernovae (sne) are crucial probes of explosive phenomena at the deaths of massive stars and neutrino physics. high-energy neutrinos are produced through hadronic processes by cosmic rays, which are accelerated during interaction between the supernova (sn) ejecta and circumstellar material (csm). recent observations of extragalactic sne have revealed that a dense csm is commonly expelled by the progenitor star. we provide new quantitative predictions of time-dependent high-energy neutrino emission from diverse types of sne. we show that icecube and km3net can detect ∼103 events from a sn ii-p (and ∼3 ×105 events from a sn iin) at a distance of 10 kpc. the new model also enables us to critically optimize the time window for dedicated searches for nearby sne. a successful detection will give us a multienergy neutrino view of sn physics and new opportunities to study neutrino properties, as well as clues to the cosmic-ray origin. gev-tev neutrinos may also be seen by km3net, hyper-kamiokande, and pingu. | new prospects for detecting high-energy neutrinos from nearby supernovae |
extreme magnifications of distant objects by factors of several thousand have recently become a reality. small, very luminous compact objects, such as supernovae (sne), giant stars at z = 1 - 2, pop iii stars at z > 7, and even gravitational waves (gws) from merging binary black holes near caustics of gravitational lenses can be magnified many thousands or even tens of thousands of times thanks to their small size. we explore the probability of such extreme magnifications in a cosmological context and include the effect of microlenses near critical curves. we show how the presence of microlenses near the critical curve sets a limit on the maximum magnification. we use a combination of state of the art halo mass functions, high-resolution analytical models for the density profiles, and inverse ray tracing to estimate the probability of magnification near caustics. we estimate the rate of highly magnified events in the case of sne, gws, and very luminous stars including pop iii stars. our findings reveal that future observations will increase the number of events at extreme magnifications, and will open the door not only to studying individual sources at cosmic distances, but also to constraining compact dark matter candidates. | the universe at extreme magnification |
we present an improved method for the precise reconstruction of cosmic-ray air showers above 1 017 ev with sparse radio arrays. the method is based on the comparison of measured pulses to predictions for radio pulse shapes by coreas simulations. we applied our method to the data of tunka-rex, a 1 km2 radio array in siberia operating in the frequency band of 30-80 mhz. tunka-rex is triggered by the air-cherenkov detector tunka-133 and by scintillators (tunka-grande). the instrument collects air-shower data since 2012. the present paper describes an updated data analysis of tunka-rex and details of the new method applied. after quality cuts, when tunka-rex reaches its full efficiency, the energy resolution of about 10% given by the new method has reached the limit of systematic uncertainties due to the calibration uncertainty and shower-to-shower fluctuations. at the same time the shower maximum reconstruction has improved compared to the previous method based on the slope of the lateral distribution and reaches a precision of better than 35 g /cm2 . we also define conditions of the measurements at which the shower maximum resolution of tunka-rex reaches a value of 25 g /cm2 and becomes competitive to optical detectors. to check and validate our reconstruction and efficiency cuts we compare individual events to the reconstruction of tunka-133. furthermore, we compare the mean of the shower maximum as a function of primary energy to the measurements of other experiments. | reconstruction of cosmic ray air showers with tunka-rex data using template fitting of radio pulses |
we study the impact of cosmic rays (crs) on the structure of virial shocks, using a large suite of high-resolution cosmological fire-2 simulations accounting for cr injection by supernovae. in milky way-mass, low-redshift (z ≲ 1-2) haloes, which are expected to form 'hot haloes' with slowly cooling gas in quasi-hydrostatic equilibrium (with a stable virial shock), our simulations without crs do exhibit clear virial shocks. the cooler phase condensing out from inflows becomes pressure confined to overdense clumps, embedded in low-density, volume-filling hot gas with volume-weighted cooling time longer than inflow time. the gas thus transitions sharply from cool free-falling inflow, to hot and thermal-pressure supported at approximately the virial radius (≈rvir), and the shock is quasi-spherical. with crs, we previously argued that haloes in this particular mass and redshift range build up cr-pressure-dominated gaseous haloes. here, we show that when cr pressure dominates over thermal pressure, there is no significant virial shock. instead, inflowing gas is gradually decelerated by the cr pressure gradient and the gas is relatively subsonic out to and even beyond rvir. rapid cooling also maintains subvirial temperatures in the inflowing gas within ~rvir. | virial shocks are suppressed in cosmic ray-dominated galaxy haloes |
in this work, we reexamine sulfur chemistry occurring on and in the ice mantles of interstellar dust grains, and report the effects of two new modifications to standard astrochemical models: namely, (a) the incorporation of cosmic-ray-driven radiation chemistry and (b) the assumption of fast, nondiffusive reactions for key radicals in the bulk. results from our models of dense molecular clouds show that these changes can have a profound influence on the abundances of sulfur-bearing species in ice mantles, including a reduction in the abundance of solid-phase h2s and hs, and a significant increase in the abundances of ocs, so2, as well as pure allotropes of sulfur, especially s8. these pure-sulfur species—though nearly impossible to observe directly—have long been speculated to be potential sulfur reservoirs and our results represent possibly the most accurate estimates yet of their abundances in the dense interstellar medium. moreover, the results of these updated models are found to be in good agreement with available observational data. finally, we examine the implications of our findings with regard to the as-yet-unknown sulfur reservoir thought to exist in dense interstellar environments. | efficient production of s8 in interstellar ices: the effects of cosmic-ray-driven radiation chemistry and nondiffusive bulk reactions |
particle acceleration in magnetized relativistic jets still puzzles theorists. in this work, we investigate the acceleration of particles injected into a three-dimensional relativistic magnetohydrodynamical jet subject to current-driven kink (cdk) instability. we find that, once turbulence driven by cdk fully develops, achieving a nearly stationary state, the amplitude of excited wiggles along the jet spine attains maximum growth, causing disruption of the magnetic field lines and the formation of several sites of fast reconnection. low-energy protons injected into the jet at this state experience exponential acceleration, mostly in directions parallel to the local magnetic field, up to maximum energies $e\sim {10}^{16}$ ev for $b\sim 0.1$ g and $e\sim {10}^{18}$ ev for $b\sim 10$ g. the larmor radius of the particles attaining these energies corresponds to the size of the acceleration region (∼the diameter of the perturbed jet). there is a clear association of the accelerated particles with regions of fast reconnection. in the early nonlinear growth stage of the cdk, when there are no sites of fast reconnection yet, injected particles with initially much larger energy are accelerated by magnetic curvature drift. we have also obtained the acceleration time due to reconnection with a dependence on the particles' energy, ${t}_{a}\propto {e}^{0.1}$ . the energy spectrum of the accelerated particles develops a power-law index $p$ ∼ -1.2 in the beginning, in agreement with earlier works. our results provide a multidimensional framework for exploring this process in real systems and explain their emission patterns, especially at very high energies, and associated neutrino emission recently detected in some blazars. | particle acceleration by relativistic magnetic reconnection driven by kink instability turbulence in poynting flux-dominated jets |
with the advent of the first luminous sources at cosmic dawn (cd), the redshifted 21-cm signal, from the neutral hydrogen in the inter-galactic medium (igm), is predicted to undergo a transition from absorption to emission against the cmb. using simulations, we show that the redshift evolution of the sign and the magnitude of the 21-cm bispectrum can disentangle the contributions from ly$\alpha$ coupling and x-ray heating of the igm, the two most dominant processes which drive this transition. this opens a new avenue to probe the first luminous sources and the igm physics at cd. | probing igm physics during cosmic dawn using the redshifted 21-cm bispectrum |
galactic gamma ray astronomy at very high energy (eγ≳30 tev ) is a vital tool in the study of the nonthermal universe. the interpretation of the observations in this energy region requires the precise modeling of the attenuation of photons due to pair production interactions (γ γ →e+e- ) where the targets are the radiation fields present in interstellar space. for gamma rays with energy eγ≳300 tev the attenuation is mostly due to the photons of the cosmic microwave background radiation. at lower energy the most important targets are infrared photons with wavelengths in the range λ ≃50 - 500 μ m emitted by dust. the evaluation of the attenuation requires a good knowledge of the density, and energy and angular distributions of the target photons for all positions in the galaxy. in this work we discuss a simple model for the infrared radiation that depends on only few parameters associated to the space and temperature distributions of the emitting dust. the model allows to compute with good accuracy the effects of absorption for any space and energy distribution of the diffuse galactic gamma ray emission. the absorption probability due to the galactic infrared radiation is maximum for eγ≃150 tev , and can be as large as pabs≃0.45 for distant sources on lines of sight that pass close to the galactic center. the systematic uncertainties on the absorption probability are estimated as δ pabs≲0.08 . | absorption of very high energy gamma rays in the milky way |
high energy γ -rays from giant molecular clouds (gmcs) carry direct information about the spatial and energy distributions of galactic cosmic rays (crs). the recently released catalogs of gmcs contain sufficiently massive clouds to be used as barometers for probing, through their γ -ray emission, the density of crs throughout the galactic disk. based on the data of fermi-lat, we report the discovery of γ -ray signals from nineteen gmcs located at distances up to 12.5 kpc. the galactocentric radial distribution of the cr density derived from the γ -ray and co observations of these objects, as well as from some nearby clouds that belong to the gould belt complex, unveil a homogeneous "sea" of crs with a constant density and spectral shape close to the flux of directly (locally) measured crs. this concerns the galactocentric distances exceeding 8 kpc, as well as the sagittarius b complex, in the region of the galactic center. on the other hand, for the galactocentric distances between 4 and 8 kpc, we found noticeable deviations from the cr sea level; in some locations, gmcs are characterized by enhanced cr density. this could be the result of a possible global increase of the level of the cr sea towards the galactic center and/or by the presence of recent cr accelerators close to some specific clouds. | probing the sea of galactic cosmic rays with fermi-lat |
the influence of solar forcing and galactic cosmic rays (gcr) ionization on the global distribution of clouds is investigated using 42 years era-5 data (1979-2020). in the mid-latitudes over eurasia, gcr and cloudiness are negatively correlated, which argues against the ionization theory of enhanced cloud droplet nucleation due to increased gcr during minima in the solar cycle. in the tropics, the solar cycle and cloudiness are positively correlated in regional walker circulations below 2 km altitude. the phase relationship between amplification of regional tropical circulations and the solar cycle is consistent with total solar forcing, rather than modulation of gcr. however, in the intertropical convergence zone, changes in the cloud distribution are consistent with a positive coupling with gcr in the free atmosphere (2-6 km). this study opens some future challenges and research directions, and clarifies how atmospheric circulation at the regional scale can help in understanding solar-induced climate variability. | the influence of solar-modulated regional circulations and galactic cosmic rays on global cloud distribution |
aim. the vertical halo scale height is a crucial parameter to understand the transport of cosmic-ray electrons (cre) and their energy loss mechanisms in spiral galaxies. until now, the radio scale height could only be determined for a few edge-on galaxies because of missing sensitivity at high resolution.methods: we developed a sophisticated method for the scale height determination of edge-on galaxies. with this we determined the scale heights and radial scale lengths for a sample of 13 galaxies from the chang-es radio continuum survey in two frequency bands.results: the sample average values for the radio scale heights of the halo are 1.1 ± 0.3 kpc in c-band and 1.4 ± 0.7 kpc in l-band. from the frequency dependence analysis of the halo scale heights we found that the wind velocities (estimated using the adiabatic loss time) are above the escape velocity. we found that the halo scale heights increase linearly with the radio diameters. in order to exclude the diameter dependence, we defined a normalized scale height h∼ which is quite similar for all sample galaxies at both frequency bands and does not depend on the star formation rate or the magnetic field strength. however, h∼ shows a tight anticorrelation with the mass surface density.conclusions: the sample galaxies with smaller scale lengths are more spherical in the radio emission, while those with larger scale lengths are flatter. the radio scale height depends mainly on the radio diameter of the galaxy. the sample galaxies are consistent with an escape-dominated radio halo with convective cosmic ray propagation, indicating that galactic winds are a widespread phenomenon in spiral galaxies. while a higher star formation rate or star formation surface density does not lead to a higher wind velocity, we found for the first time observational evidence of a gravitational deceleration of cre outflow, e.g. a lowering of the wind velocity from the galactic disk. | chang-es. ix. radio scale heights and scale lengths of a consistent sample of 13 spiral galaxies seen edge-on and their correlations |
context. carbon fractionation has been studied from a theoretical point of view with different models of time-dependent chemistry, including both isotope-selective photodissociation and low-temperature isotopic exchange reactions.aims: recent chemical models predict that isotopic exchange reactions may lead to a depletion of 13c in nitrile-bearing species, with 12c/13c ratios two times higher than the elemental abundance ratio of 68 in the local interstellar medium. since the carbon isotopic ratio is commonly used to evaluate the 14n/15n ratios with the double-isotope method, it is important to study carbon fractionation in detail to avoid incorrect assumptions.methods: in this work, we implemented a gas-grain chemical model with new isotopic exchange reactions and investigated their introduction in the context of dense and cold molecular gas. in particular, we investigated the 12c/13c ratios of hnc, hcn, and cn using a grid of models, with temperatures and densities ranging from 10 to 50 k and 2 × 103 to 2 × 107 cm-3, respectively.results: we suggest a possible 13c exchange through the 13c + c3 → 12c +13cc2 reaction, which does not result in dilution, but rather in 13c enhancement, for molecules that are formed starting from atomic carbon. this effect is efficient in a range of time between the formation of co and its freeze-out on grains. furthermore, the parameter-space exploration shows, on average, that the 12c/13c ratios of nitriles are predicted to be a factor 0.8-1.9 different from the local 12c/13c of 68 for high-mass star-forming regions. this result also affects the 14n/15n ratio: a value of 330 obtained with the double-isotope method is predicted to vary in the range 260-630, up to 1150, depending on the physical conditions. finally, we studied the 12c/13c ratios of nitriles by varying the cosmic-ray ionisation rate, ζ: the 12c/13c ratios increase with ζ because of secondary photons and cosmic-ray reactions. | carbon isotopic fractionation in molecular clouds |
shear flows are ubiquitously present in space and astrophysical plasmas. this paper highlights the central idea of the non-thermal acceleration of charged particles in shearing flows and reviews some of the recent developments. topics include the acceleration of charged particles by microscopic instabilities in collisionless relativistic shear flows, fermi-type particle acceleration in macroscopic, gradual and non-gradual shear flows, as well as shear particle acceleration by large-scale velocity turbulence. when put in the context of jetted astrophysical sources such as active galactic nuclei, the results illustrate a variety of means beyond conventional diffusive shock acceleration by which power-law like particle distributions might be generated. this suggests that relativistic shear flows can account for efficient in-situ acceleration of energetic electrons and be of relevance for the production of extreme cosmic rays. | an introduction to particle acceleration in shearing flows |
the standard-model extension (sme) provides a comprehensive effective field-theory framework for the study of cpt and lorentz symmetry. this work reviews the structure and philosophy of the sme and provides some intuitive examples of symmetry violation. the results of recent gravitational tests performed within the sme are summarized including analysis of results from the laser interferometer gravitational-wave observatory (ligo), sensitivities achieved in short-range gravity experiments, constraints from cosmic-ray data, and results achieved by studying planetary ephemerids. some proposals and ongoing efforts will also be considered including gravimeter tests, tests of the weak equivalence principle, and antimatter experiments. our review of the above topics is augmented by several original extensions of the relevant work. we present new examples of symmetry violation in the sme and use the cosmic-ray analysis to place first-ever constraints on 81 additional operators. | the standard-model extension and gravitational tests |
we examine indirect detection of dark matter that annihilates into dark glueballs, which in turn decay into the standard model via a range of portals. this arises if the dark matter candidate couples to a confining gauge force without light flavours, representative of many possible complex dark sectors. such hidden valley scenarios are being increasingly considered due to non-detection of minimal models as well as theoretical motivations such as the twin higgs solution to the little hierarchy problem. study of dark glueballs in indirect detection has previously been hampered by the difficulty of modeling their production in dark showers. we use the recent glueshower code to produce the first constraints on dark matter annihilating via dark glueballs into the standard model across photon, antiproton, and positron channels. we also fit the galactic centre excess and use this observation, combined with other astrophysical constraints, to show how multi-channel observations can constrain uv and ir details of the theory, namely the exact decay portal and hadronization behaviour respectively. this provides unique complementary discovery and diagnostic potential to hidden valley searches at colliders. it is interesting to note that thermal wimps annihilating to o (10 gev) dark glueballs and then the sm via the twin-higgs-like decay portal can account for the gce while respecting other constraints. | indirect detection of dark matter annihilating into dark glueballs |
many of the baryons associated with a galaxy reside in its circumgalactic medium (cgm), in a diffuse volume-filling phase at roughly the virial temperature. much of the oxygen produced over cosmic time by the galaxy’s stars also ends up there. the resulting absorption lines in the spectra of uv and x-ray background sources are powerful diagnostics of the feedback processes that prevent more of those baryons from forming stars. this paper presents predictions for cgm absorption lines (o vi, o vii, o viii, ne viii, n v) that are based on precipitation-regulated feedback models, which posit that the radiative cooling time of the ambient medium cannot drop much below 10 times the freefall time without triggering a strong feedback event. the resulting predictions align with many different observational constraints on the milky way’s ambient cgm and explain why n o vi≈ 1014 cm-2 over large ranges in halo mass and projected radius. within the precipitation framework, the strongest o vi absorption lines result from vertical mixing of the cgm that raises low-entropy ambient gas to greater altitudes, because adiabatic cooling of the uplifted gas then lowers its temperature and raises the fractional abundance of o5+. condensation stimulated by uplift may also produce associated low-ionization components. the observed velocity structure of the o vi absorption suggests that galactic outflows do not expel circumgalactic gas at the halo’s escape velocity, but rather drive circulation that dissipates much of the galaxy’s supernova energy within the ambient medium, causing some of it to expand beyond the virial radius. | ambient column densities of highly ionized oxygen in precipitation-limited circumgalactic media |
khufu's pyramid is one of the largest archaeological monument all over the world, which still holds many mysteries. in 2016 and 2017, the scanpyramids team reported on several discoveries of previously unknown voids by cosmic-ray muon radiography that is a non-destructive technique ideal for the investigation of large-scale structures. among these discoveries, a corridor-shaped structure has been observed behind the so-called chevron zone on the north face, with a length of at least 5 meters. a dedicated study of this structure was thus necessary to better understand its function in relation with the enigmatic architectural role of this chevron. here we report on new measurements of excellent sensitivity obtained with nuclear emulsion films from nagoya university and gaseous detectors from cea, revealing a structure of about 9 m length with a transverse section of about 2.0 m by 2.0 m. | precise characterization of a corridor-shaped structure in khufu's pyramid by observation of cosmic-ray muons |
grb 221009a is the brightest gamma-ray burst (grb) ever detected. to probe the very-high-energy (vhe; >100 gev) emission, the high energy stereoscopic system (h.e.s.s.) began observations 53 hr after the triggering event, when the brightness of the moonlight no longer precluded observations. we derive differential and integral upper limits using h.e.s.s. data from the third, fourth, and ninth nights after the initial grb detection, after applying atmospheric corrections. the combined observations yield an integral energy flux upper limit of ${{\rm{\phi }}}_{\mathrm{ul}}^{95 \% }=9.7\times {10}^{-12}\,\mathrm{erg}\,{\mathrm{cm}}^{-2}\,{{\rm{s}}}^{-1}$ above e thr = 650 gev. the constraints derived from the h.e.s.s. observations complement the available multiwavelength data. the radio to x-ray data are consistent with synchrotron emission from a single electron population, with the peak in the spectral energy distribution occurring above the x-ray band. compared to the vhe-bright grb 190829a, the upper limits for grb 221009a imply a smaller gamma-ray to x-ray flux ratio in the afterglow. even in the absence of a detection, the h.e.s.s. upper limits thus contribute to the multiwavelength picture of grb 221009a, effectively ruling out an ic-dominated scenario. | h.e.s.s. follow-up observations of grb 221009a |
the first population of x-ray binaries (xrbs) is expected to affect the thermal and ionization states of the gas in the early universe. although these x-ray sources are predicted to have important implications for high-redshift observable signals, such as the hydrogen 21-cm signal from cosmic dawn and the cosmic x-ray background, their properties are poorly explored, leaving theoretical models largely uninformed. in this paper we model a population of x-ray binaries arising from zero metallicity stars. we explore how their properties depend on the adopted initial mass function (imf) of primordial stars, finding a strong effect on their number and x-ray production efficiency. we also present scaling relations between xrbs and their x-ray emission with the local star formation rate, which can be used in sub-grid models in numerical simulations to improve the x-ray feedback prescriptions. specifically, we find that the uniformity and strength of the x-ray feedback in the intergalactic medium is strongly dependant on the imf. bottom-heavy imfs result in a smoother distribution of xrbs, but have a luminosity orders of magnitude lower than more top-heavy imfs. top-heavy imfs lead to more spatially uneven, albeit strong, x-ray emission. an intermediate imf has a strong x-ray feedback while sustaining an even emission across the intergalactic medium. these differences in x-ray feedback could be probed in the future with measurements of the cosmic dawn 21-cm line of neutral hydrogen, which offers us a new way of constraining population iii imf. | population iii x-ray binaries and their impact on the early universe |
we derive new constraints on combination of dark matter-electron cross section (σχ e) and dark matter-neutrino cross section (σχ ν) utilizing the gain in kinetic energy of the dark matter (dm) particles due to scattering with the cosmic ray electrons and the diffuse supernova neutrino background (dsnb). since the flux of the dsnb neutrinos is comparable to the cosmic ray (cr) electron flux in the energy range ∼1 mev - 50 mev , scattering with the dsnb neutrinos can also boost low-mass dm significantly in addition to the boost due to interaction with the cr electrons. we use the xenon1t as well as the super-kamiokande data to derive bounds on σχ e and σχ ν. while our bounds for σχ e are comparable with those in the literature, we show that the super-kamiokande experiment provides the strongest constraint on σχ ν for dm masses below a few mev. | exclusion limits on dark matter-neutrino scattering cross section |
the determination of the injection composition of cosmic ray nuclei within astrophysical sources requires sufficiently accurate descriptions of the source physics and the propagation - apart from controlling astrophysical uncertainties. we therefore study the implications of nuclear data and models for cosmic ray astrophysics, which involves the photo-disintegration of nuclei up to iron in astrophysical environments. we demonstrate that the impact of nuclear model uncertainties is potentially larger in environments with non-thermal radiation fields than in the cosmic microwave background. we also study the impact of nuclear models on the nuclear cascade in a gamma-ray burst radiation field, simulated at a level of complexity comparable to the most precise cosmic ray propagation code. we conclude with an isotope chart describing which information is in principle necessary to describe nuclear interactions in cosmic ray sources and propagation. | nuclear physics meets the sources of the ultra-high energy cosmic rays |
relativistic magnetized jets from active galaxies are among the most powerful cosmic accelerators, but their particle acceleration mechanisms remain a mystery. we present a new acceleration mechanism associated with the development of the helical kink instability in relativistic jets, which leads to the efficient conversion of the jet's magnetic energy into nonthermal particles. large-scale three-dimensional ab initio simulations reveal that the formation of highly tangled magnetic fields and a large-scale inductive electric field throughout the kink-unstable region promotes rapid energization of the particles. the energy distribution of the accelerated particles develops a well-defined power-law tail extending to the radiation-reaction limited energy in the case of leptons, and to the confinement energy of the jet in the case of ions. when applied to the conditions of well-studied bright knots in jets from active galaxies, this mechanism can account for the spectrum of synchrotron and inverse compton radiating particles, and offers a viable means of accelerating ultrahigh-energy cosmic rays to 1 020 ev . | efficient nonthermal particle acceleration by the kink instability in relativistic jets |
ultrahigh-energy cosmic rays (uhecrs) are atomic nuclei from space with vastly higher energies than any other particles ever observed. their origin and chemical composition remain a mystery. as we show here, the large and intermediate angular scale anisotropies observed by the pierre auger observatory are a powerful tool for understanding the origin of uhecrs. without specifying any particular production mechanism but only postulating that the source distribution follows the matter distribution of the local universe, a good accounting of the magnitude, direction, and energy dependence of the dipole anisotropy at energies above 8 × 1018 ev is obtained after taking into account the impact of energy losses during propagation (the "gzk horizon"), diffusion in the extragalactic magnetic field, and deflections in the galactic magnetic field (gmf). this is a major step toward the long-standing hope of using uhecr anisotropies to constrain uhecr composition and magnetic fields. the observed dipole anisotropy is incompatible with a pure proton composition in this scenario. with a more accurate treatment of energy losses, it should be possible to further constrain the cosmic-ray composition and properties of the extragalactic magnetic field, self-consistently improve the gmf model, and potentially expose individual uhecr sources. | the imprint of large-scale structure on the ultrahigh-energy cosmic-ray sky |
the radar echo telescope for cosmic rays (ret-cr) is a recently funded experiment designed to detect the englacial cascade of a cosmic ray-initiated air shower via in-ice radar, toward the goal of a full-scale, next-generation experiment to detect ultrahigh energy neutrinos in polar ice. for cosmic rays with a primary energy greater than 10 pev, roughly 10% of an air shower's energy reaches the surface of a high elevation ice sheet (≳2 k ˙ m ) concentrated into a radius of roughly 10 cm. this penetrating shower core creates an in-ice cascade orders of magnitude more dense than the preceding in-air cascade. this dense cascade can be detected via the radar echo technique, where transmitted radio waves are reflected from the ionization deposit left in the wake of the cascade. ret-cr will test the radar echo method in nature, with the in-ice cascade of a cosmic ray-initiated air shower serving as a test beam. we present the projected event rate and sensitivity based upon a three part simulation using corsika, geant4, and radioscatter. ret-cr expects ∼1 rad ar echo event per day. | the radar echo telescope for cosmic rays: pathfinder experiment for a next-generation neutrino observatory |
the kilometer square array~(km2a) of the large high altitude air shower observatory (lhaaso) aims at surveying the northern gamma-ray sky at energies above 10 tev with unprecedented sensitivity. gamma-ray observations have long been one of the most powerful tools for dark matter searches, as e.g., high-energy gamma-rays could be produced by the decays of heavy dark matter particles. in this letter, we present the first dark matter analysis with lhaaso-km2a, using the first 340~days of data from 1/2-km2a and 230~days of data from 3/4-km2a. several regions of interest are used to search for a signal and account for the residual cosmic-ray background after gamma/hadron separation. we find no excess of dark matter signals, and thus place some of the strongest gamma-ray constraints on the lifetime of heavy dark matter particles with mass between 10^5 and 10^9~gev. our results with lhaaso are robust, and have important implications for dark matter interpretations of the diffuse astrophysical high-energy neutrino emission. | constraints on heavy decaying dark matter from 570 days of lhaaso observations |
we present x-ray spectral analysis of xmm-newton and chandra observations in the 31.3 deg2 stripe-82x (s82x) field. of the 6181 unique x-ray sources in this field, we analyze a sample of 2937 candidate active galactic nuclei (agns) with solid redshifts and sufficient counts determined by simulations. our results show an observed population with median values of spectral index ${\rm{\gamma }}={1.94}_{-0.39}^{+0.31}$ , column density log $\,{n}_{{\rm{h}}}/{\mathrm{cm}}^{-2}={20.7}_{-0.5}^{+1.2}$ and intrinsic, de-absorbed, 2-10 kev luminosity log $\,{l}_{{\rm{x}}}/\mathrm{erg}\,\ {{\rm{s}}}^{-1}={44.0}_{-1.0}^{+0.7}$ , in the redshift range 0-4. we derive the intrinsic, model-independent, fraction of agns that are obscured ( $22\leqslant \mathrm{log}\,{n}_{{\rm{h}}}/{\mathrm{cm}}^{-2}\lt 24$ ), finding a significant increase in the obscured agn fraction with redshift and a decline with increasing luminosity. the average obscured agn fraction is 57% ± 4% for log l x/erg s-1 > 43. this work constrains the agn obscuration and spectral shape of the still uncertain high-luminosity and high-redshift regimes (log l x/erg s-1 > 45.5, z > 3), where the obscured agn fraction rises to 64% ± 12%. we report a luminosity and density evolution of the x-ray luminosity function, with obscured agns dominating at all luminosities at z > 2, and unobscured sources prevailing at log l x/erg s-1 > 45 at lower redshifts. our results agree with the evolutionary models in which the bulk of agn activity is triggered by gas-rich environments and in a downsizing scenario. moreover, the black hole accretion density (bhad) is found to evolve similarly to the star formation rate density, confirming the coevolution between agn and host galaxy, but suggesting different timescales in their growing history. the derived bhad evolution shows that compton-thick agns contribute to the accretion history of agns as much as all other agn populations combined. | on the cosmic evolution of agn obscuration and the x-ray luminosity function: xmm-newton and chandra spectral analysis of the 31.3 deg2 stripe 82x |
a gravitationally collapsed object can bounce out from its horizon via a tunnelling process that violates the classical equations in a finite region. since tunnelling is a nonperturbative phenomenon, it cannot be described in terms of quantum fluctuations around a classical solution, and a background-free formulation of quantum gravity is needed to analyze it. here, we use loop quantum gravity to compute the amplitude for this process, in a first approximation. the amplitude determines the tunnelling time as a function of the mass. this is the key information to evaluate the relevance of this process for the interpretation of fast radio bursts or high-energy cosmic rays. the calculation offers a template and a concrete example of how a background-free quantum theory of gravity can be used to compute a realistic observable quantity. | planck star tunneling time: an astrophysically relevant observable from background-free quantum gravity |
galactic cosmic rays (gcrs) are affected by solar modulation while they propagate through the heliosphere. the study of the time variation of gcr spectra observed at earth can shed light on the underlying physical processes, specifically diffusion and particle drifts. recently, the ams-02 experiment measured with very high accuracy the time variation of the cosmic-ray proton and helium flux between 2011 may and 2017 may in the rigidity range from 1 to 60 gv. in this work, a comprehensive three-dimensional steady-state numerical model is used to solve parker’s transport equation and reproduce the monthly proton fluxes observed by ams-02. we find that the rigidity slope of the perpendicular mean free path above 4 gv remains constant, while below 4 gv, it increases during solar maximum. assuming the same mean free paths for helium and protons, the models are able to reproduce the time behavior of the p/he ratio observed by ams-02. the dependence of the diffusion tensor on the particle mass-to-charge ratio, a/z, is found to be the main cause of the time dependence of p/he below 3 gv. | numerical modeling of galactic cosmic-ray proton and helium observed by ams-02 during the solar maximum of solar cycle 24 |
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