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we report a first measurement for ultrahigh energy cosmic rays of the correlation between the depth of shower maximum and the signal in the water cherenkov stations of air-showers registered simultaneously by the fluorescence and the surface detectors of the pierre auger observatory. such a correlation measurement is a unique feature of a hybrid air-shower observatory with sensitivity to both the electromagnetic and muonic components. it allows an accurate determination of the spread of primary masses in the cosmic-ray flux. up till now, constraints on the spread of primary masses have been dominated by systematic uncertainties. the present correlation measurement is not affected by systematics in the measurement of the depth of shower maximum or the signal in the water cherenkov stations. the analysis relies on general characteristics of air showers and is thus robust also with respect to uncertainties in hadronic event generators. the observed correlation in the energy range around the 'ankle' at lg (e /ev) = 18.5- 19.0 differs significantly from expectations for pure primary cosmic-ray compositions. a light composition made up of proton and helium only is equally inconsistent with observations. the data are explained well by a mixed composition including nuclei with mass a > 4. scenarios such as the proton dip model, with almost pure compositions, are thus disfavored as the sole explanation of the ultrahigh-energy cosmic-ray flux at earth. | evidence for a mixed mass composition at the 'ankle' in the cosmic-ray spectrum |
primary cosmic-ray elemental spectra have been measured with the balloon-borne cosmic ray energetics and mass (cream) experiment since 2004. the third cream payload (cream-iii) flew for 29 days during the 2007-2008 antarctic season. energies of incident particles above 1 tev are measured with a calorimeter. individual elements are clearly separated with a charge resolution of ∼0.12 e (in charge units) and ∼0.14 e for protons and helium nuclei, respectively, using two layers of silicon charge detectors. the measured proton and helium energy spectra at the top of the atmosphere are harder than other existing measurements at a few tens of gev. the relative abundance of protons to helium nuclei is 9.53 ± 0.03 for the range of 1 tev/n to 63 tev/n. this ratio is considerably smaller than other measurements at a few tens of gev/n. the spectra become softer above ∼20 tev. however, our statistical uncertainties are large at these energies and more data are needed. | proton and helium spectra from the cream-iii flight |
the interaction of the interstellar and solar winds is complex, as revealed by differences in intensities and anisotropies of low-energy ions (>0.5 mev per nucleon) originating inside the heliosphere and those of higher-energy galactic cosmic rays (>70 mev per nucleon) originating outside, in the milky way. on 5 november 2018, voyager 2 observed a sharp decrease in the intensity of low-energy ions and a simultaneous increase in the intensity of cosmic rays, indicating that voyager 2 had crossed the heliopause at 119 au and entered interstellar space about six years after voyager 1. unlike voyager 1, which found that two interstellar flux tubes had invaded the heliosheath and served as precursors to the heliopause, voyager 2 found no similar precursors. however, just beyond the heliopause voyager 2 discovered a boundary layer, in which low-energy particles streamed outward along the magnetic field and cosmic ray intensities were only 90% of those further out. | cosmic ray measurements from voyager 2 as it crossed into interstellar space |
the detection of the hyper-bright gamma-ray burst (grb) 221009a enables us to explore the nature of the grb emission and the origin of very high-energy gamma rays. we analyze the fermi large area telescope (fermi-lat) data of this burst and investigate the gev-tev emission in the framework of the external reverse-shock model. we show that the early ~1-10 gev emission can be explained by the external inverse-compton mechanism via upscattering mev gamma rays by electrons accelerated at the reverse shock, in addition to the synchrotron self-compton component. the predicted early optical flux could have been brighter than that of the naked-eye grb 080319b. we also show that proton synchrotron emission from accelerated ultrahigh-energy cosmic rays (uhecrs) is detectable and could potentially explain ≳tev photons detected by lhaaso or constrain the uhecr acceleration mechanism. our model suggests that the detection of ${ \mathcal o }(10\,\mathrm{tev})$ photons with energies up to ~18 tev is possible for reasonable models of the extragalactic background light without invoking new physics and predicts anticorrelations between mev photons and tev photons, which can be tested with the lhaaso data. | external inverse-compton and proton synchrotron emission from the reverse shock as the origin of vhe gamma rays from the hyper-bright grb 221009a |
we report a search for cosmic-ray boosted dark matter with protons using the 0.37 megaton×years data collected at super-kamiokande experiment during the 1996-2018 period (ski-iv phase). we searched for an excess of proton recoils above the atmospheric neutrino background from the vicinity of the galactic center. no such excess is observed, and limits are calculated for two reference models of dark matter with either a constant interaction cross section or through a scalar mediator. this is the first experimental search for boosted dark matter with hadrons using directional information. the results present the most stringent limits on cosmic-ray boosted dark matter and exclude the dark matter-nucleon elastic scattering cross section between 1 0-33cm2 and 1 0-27cm2 for dark matter mass from 1 mev /c2 to 300 mev /c2 . | search for cosmic-ray boosted sub-gev dark matter using recoil protons at super-kamiokande |
tidal disruption events (tdes) are processes where stars are torn apart by the strong gravitational force near to a massive or supermassive black hole. if a jet is launched in such a process, particle acceleration may take place in internal shocks. we demonstrate that jetted tdes can simultaneously describe the observed neutrino and cosmic ray fluxes at the highest energies if stars with heavier compositions, such as carbon-oxygen white dwarfs, are tidally disrupted and these events are sufficiently abundant. we simulate the photo-hadronic interactions both in the tde jet and in the propagation through the extragalactic space and we show that the simultaneous description of ultra-high energy cosmic ray (uhecr) and pev neutrino data implies that a nuclear cascade in the jet is developed by photo-hadronic interactions. | tidally disrupted stars as a possible origin of both cosmic rays and neutrinos at the highest energies |
we re-evaluate the prompt atmospheric neutrino flux, using the measured charm cross sections at rhic and the large hadron collider to constrain perturbative qcd parameters such as the factorization and renormalization scales, as well as modern parton distribution functions and recent estimates of the cosmic-ray spectra. we find that our result for the prompt neutrino flux is lower than previous perturbative qcd estimates and, consequently, alters the signal-to-background statistics of the recent icecube measurements at high energies. | perturbative charm production and the prompt atmospheric neutrino flux in light of rhic and lhc |
we report a measurement of the energy spectrum of cosmic rays above 2.5 ×1018 ev based on 215 030 events. new results are presented: at about 1.3 ×1019 ev , the spectral index changes from 2.51 ±0.03 (stat ) ±0.05 (syst ) to 3.05 ±0.05 (stat ) ±0.10 (syst ) , evolving to 5.1 ±0.3 (stat ) ±0.1 (syst ) beyond 5 ×1019 ev , while no significant dependence of spectral features on the declination is seen in the accessible range. these features of the spectrum can be reproduced in models with energy-dependent mass composition. the energy density in cosmic rays above 5 ×1018 ev is [5.66 ±0.03 (stat ) ±1.40 (syst ) ]×1053 erg mpc-3 . | features of the energy spectrum of cosmic rays above 2.5 ×1018 ev using the pierre auger observatory |
a critical review of the standard paradigm for the origin of galactic cosmic rays (crs) is presented. recent measurements of local and far-away crs reveal unexpected behaviors, which challenge the commonly accepted scenario. these recent findings are discussed, together with long-standing open issues. despite the progress made thanks to ever-improving observational techniques and theoretical investigations, at present our understanding of the origin and of the behavior of crs remains incomplete. we believe it is still unclear whether a modification of the standard paradigm, or rather a radical change of the paradigm itself is needed in order to interpret all the available data on crs within a self-consistent scenario. | the origin of galactic cosmic rays: challenges to the standard paradigm |
using the latest ams-02 cosmic-ray antiproton flux data, we search for a potential dark matter annihilation signal. the background parameters about the propagation, source injection, and solar modulation are not assumed a priori but based on the results inferred from the recent b / c ratio and proton data measurements instead. the possible dark matter signal is incorporated into the model self-consistently under a bayesian framework. compared with the astrophysical background-only hypothesis, we find that a dark matter signal is favored. the rest mass of the dark matter particles is ∼20 - 80 gev , and the velocity-averaged hadronic annihilation cross section is about (0.2 - 5 )×10-26 cm3 s-1 , in agreement with that needed to account for the galactic center gev excess and/or the weak gev emission from dwarf spheroidal galaxies reticulum 2 and tucana iii. tight constraints on the dark matter annihilation models are also set in a wide mass region. | possible dark matter annihilation signal in the ams-02 antiproton data |
the nondetection of gev-scale weakly interacting massive particles (wimps) has led to increased interest in more general candidates, including sub-gev dark matter. direct-detection experiments, despite their high sensitivity to wimps, are largely blind to sub-gev dark matter. recent work has shown that cosmic-ray elastic scattering with sub-gev dark matter would both alter the observed cosmic ray spectra and produce a flux of relativistic dark matter, which would be detectable with traditional dark matter experiments as well as larger, higher-threshold detectors for neutrinos. using data, detectors, and analysis techniques not previously considered, we substantially increase the regions of parameter space excluded by neutrino experiments for both dark matter-nucleon and dark matter-electron elastic scattering. we also show how to further improve sensitivity to light dark matter. | strong new limits on light dark matter from neutrino experiments |
neutrinos with energies above 1017 ev are detectable with the surface detector array of the pierre auger observatory. the identification is efficiently performed for neutrinos of all flavors interacting in the atmosphere at large zenith angles, as well as for earth-skimming τ neutrinos with nearly tangential trajectories relative to the earth. no neutrino candidates were found in ~ 14.7 years of data taken up to 31 august 2018. this leads to restrictive upper bounds on their flux. the 90% c.l. single-flavor limit to the diffuse flux of ultra-high-energy neutrinos with an eν-2 spectrum in the energy range 1.0 × 1017 ev -2.5 × 1019 ev is e2 dnν/deν < 4.4 × 10-9 gev cm-2 s-1 sr-1, placing strong constraints on several models of neutrino production at eev energies and on the properties of the sources of ultra-high-energy cosmic rays. | probing the origin of ultra-high-energy cosmic rays with neutrinos in the eev energy range using the pierre auger observatory |
the microphysics of ~ gev cosmic ray (cr) transport on galactic scales remain deeply uncertain, with almost all studies adopting simple prescriptions (e.g. constant diffusivity). we explore different physically motivated, anisotropic, dynamical cr transport scalings in high-resolution cosmological feedback in realistic environment (fire) simulations of dwarf and ~l* galaxies where scattering rates vary with local plasma properties motivated by extrinsic turbulence (et) or self-confinement (sc) scenarios, with varying assumptions about e.g. turbulent power spectra on un-resolved scales, alfvén-wave damping, etc. we self-consistently predict observables including γ-rays (lγ), grammage, residence times, and cr energy densities to constrain the models. we demonstrate many non-linear dynamical effects (not captured in simpler models) tend to enhance confinement. for example, in multiphase media, even allowing arbitrary fast transport in neutral gas does not substantially reduce cr residence times (or lγ), as transport is rate-limited by the ionized wim and 'inner cgm' gaseous halo (104-106 k gas within $\lesssim 10\!-\!30\,$ kpc), and lγ can be dominated by trapping in small 'patches'. most physical et models contribute negligible scattering of ~1-10 gev crs, but it is crucial to account for anisotropy and damping (especially of fast modes) or else scattering rates would violate observations. we show that the most widely assumed scalings for sc models produce excessive confinement by factors ≳100 in the warm ionized medium (wim) and inner cgm, where turbulent and landau damping dominate. this suggests either a breakdown of quasi-linear theory used to derive the cr transport parameters in sc, or that other novel damping mechanisms dominate in intermediate-density ionized gas. | testing physical models for cosmic ray transport coefficients on galactic scales: self-confinement and extrinsic turbulence at ∼gev energies |
over the last decades, cosmogenic exposure dating has permitted major advances in many fields of earth surface sciences and particularly in paleoglaciology. yet, exposure age calculation remains a complicated and dense procedure. it requires numerous choices of parameterization and the use of an accurate production rate. this study describes the crep program (http://crep.crpg.cnrs-nancy.fr) crep is a octave/matlab© online code that computes cosmic ray exposure (cre) ages for 3he and 10be. a stand-alone version of the crep code is also released with the present article. note however that only the online version is connected to the online database ice-d. the crep program offers the possibility to calculate ages with two scaling models: i.e. the empirical lal-stone time-dependent model (balco et al., 2008; lal, 1991; stone, 2000) with the muon parameters of braucher et al. (2011), and the lifton-sato-dunai (lsd) theoretical model (lifton et al., 2014). the default atmosphere model is the era-40 database (uppala et al., 2005), but one may also use the standard atmosphere for comparison (n.o.a.a, 1976). to perform the time-dependent correction, users may import their own geomagnetic database for paleomagnetic corrections or opt for one of the three proposed datasets (lifton, 2016; lifton et al., 2014; muscheler et al., 2005). for the important choice of the production rate, crep is linked to a database of production rate calibration data that is part of the ice-d (informal cosmogenic-nuclide exposure-age database) project (http://calibration.ice-d.org) users however have several possibilities to select the production rate: 1) using a worldwide mean value, 2) a regionally averaged value (not available in regions with no data), 3) a local unique value, which can be chosen among the existing dataset or imported by the user, or 4) any combination of multiple calibration data. if a global mean is chosen, the 1σ uncertainty arising from the production rate is about 5% for 10be and 10% for 3he. if a regional production rate is picked, these uncertainties are potentially lower. crep is able to calculate a large number of ages in a reasonable time (typically < 30 s for 50 samples). the user may export a summary table of the computed ages and the density probability function associated with each age (in the form of a spreadsheet). | the crep program and the ice-d production rate calibration database: a fully parameterizable and updated online tool to compute cosmic-ray exposure ages |
we consider limits on the local (z =0 ) density (n0) of extragalactic neutrino sources set by the nondetection of steady high-energy neutrino sources producing ≳50 tev muon multiplets in the present icecube data, taking into account the redshift evolution, luminosity function, and neutrino spectrum of the sources. we show that the lower limit depends moderately on source spectra and strongly on redshift evolution. we find n0≳10-8- 10-7 mpc-3 for standard candle sources evolving rapidly, ns∝(1+z ) 3 , and n0≳10-6- 10-5 mpc-3 for nonevolving sources. the corresponding upper limits on their neutrino luminosity are lνμ eff≲1 042- 1 043 erg s-1 and lνμ eff≲1 041- 1 042 erg s-1 , respectively. applying these results to a wide range of classes of potential sources, we show that powerful "blazar" jets associated with active galactic nuclei are unlikely to be the dominant sources. for almost all other steady candidate source classes (including starbursts, radio galaxies, and galaxy clusters and groups), an order of magnitude increase in the detector sensitivity at ∼0.1 - 1 pev will enable a detection (as point sources) of the few brightest objects. such an increase, which may be provided by next-generation detectors like icecube-gen2 and an upgraded km3net, can improve the limit on n0 by more than 2 orders of magnitude. future gamma-ray observations (by fermi, the high-altitude water cherenkov observatory, and the cherenkov telescope array) will play a key role in confirming the association of the neutrinos with their sources. | constraining high-energy cosmic neutrino sources: implications and prospects |
mysteries about the origin of high-energy cosmic neutrinos have deepened by the recent icecube measurement of a large diffuse flux in the 10-100 tev range. based on the standard disk-corona picture of active galactic nuclei (agn), we present a phenomenological model enabling us to systematically calculate the spectral sequence of multimessenger emission from the agn coronae. we show that protons in the coronal plasma can be stochastically accelerated up to pev energies by plasma turbulence, and find that the model explains the large diffuse flux of medium-energy neutrinos if the cosmic rays carry only a few percent of the thermal energy. we find that the bethe-heitler process plays a crucial role in connecting these neutrinos and cascaded mev gamma rays, and point out that the gamma-ray flux can even be enhanced by the reacceleration of secondary pairs. critical tests of the model are given by its prediction that a significant fraction of the mev gamma-ray background correlates with ∼10 tev neutrinos, and nearby seyfert galaxies including ngc 1068 are promising targets for icecube, km3net, icecube-gen2, and future mev gamma-ray telescopes. | hidden cores of active galactic nuclei as the origin of medium-energy neutrinos: critical tests with the mev gamma-ray connection |
a new, more comprehensive model of gas-grain chemistry in hot molecular cores is presented, in which nondiffusive reaction processes on dust-grain surfaces and in ice mantles are implemented alongside traditional diffusive surface/bulk-ice chemistry. we build on our nondiffusive treatments used for chemistry in cold sources, adopting a standard collapse/warm-up physical model for hot cores. a number of other new chemical model inputs and treatments are also explored in depth, culminating in a final model that demonstrates excellent agreement with gas-phase observational abundances for many molecules, including some (e.g., methoxymethanol) that could not be reproduced by conventional diffusive mechanisms. the observed ratios of structural isomers methyl formate, glycolaldehyde, and acetic acid are well reproduced by the models. the main temperature regimes in which various complex organic molecules (coms) are formed are identified. nondiffusive chemistry advances the production of many coms to much earlier times and lower temperatures than in previous model implementations. those species may form either as by-products of simple-ice production, or via early photochemistry within the ices while external uv photons can still penetrate. cosmic ray-induced photochemistry is less important than in past models, although it affects some species strongly over long timescales. another production regime occurs during the high-temperature desorption of solid water, whereby radicals trapped in the ice are released onto the grain/ice surface, where they rapidly react. several recently proposed gas-phase com-production mechanisms are also introduced, but they rarely dominate. new surface/ice reactions involving ch and ch2 are found to contribute substantially to the formation of certain coms. | formation of complex organic molecules in hot molecular cores through nondiffusive grain-surface and ice-mantle chemistry |
persistent excesses in the spectra of gamma rays from the galactic center and cosmic ray antiprotons can be explained by dark matter of mass 50-65 gev annihilating into b quarks, but this is typically hard to reconcile with direct detection constraints. we resolve this tension using a simple class of models, where dark matter is a pseudo-nambu-goldstone boson, having naturally momentum-suppressed couplings to nuclei. exploring the parameter space of the model, we find that it can explain the cosmic ray anomalies while remaining compatible with constraints from the relic abundance and annihilation in dwarf spheroidal galaxies. in certain regions of parameter space, the higgs-dark matter coupling can help stabilize the higgs potential up to the planck scale. the scalar partner of the dark matter is an extra higgs boson, that can explain a tentative diphoton excess observed by cms, and an excess of b b ¯ signal from lep, if its mass is ∼96 gev and the model is extended to include a heavy scalar quark. this extended model predicts a monochromatic gamma-ray line near 64 gev, at a level close to current experimental sensitivity, from dark matter annihilations in the galaxy. | pseudo-goldstone dark matter confronts cosmic ray and collider anomalies |
the ams-02 experiment has reported a new measurement of the antiproton/proton ratio in galactic cosmic rays (crs). in the energy range e ∼60 - 450 gev , this ratio is found to be remarkably constant. using recent data on cr proton, helium, and carbon fluxes, 10be/9be and b/c ratios, we have performed a global bayesian analysis based on a markov chain monte carlo sampling algorithm under a "two halo model" of cr propagation. in this model, crs are allowed to experience a different type of diffusion when they propagate in the region close to the galactic disk. we found that the vertical extent of this region is about 900 pc above and below the disk, and the corresponding diffusion coefficient scales with energy as d ∝e0.15 , describing well the observations on primary cr spectra, secondary/primary ratios, and anisotropy. under this model, we have carried out improved calculations of antiparticle spectra arising from secondary cr production and their corresponding uncertainties. we made use of monte carlo generators and accelerator data to assess the antiproton production cross sections and their uncertainties. while the positron excess requires the contribution of additional unknown sources, we found that the new ams-02 antiproton data are consistent, within the estimated uncertainties, with our calculations based on secondary production. | bayesian analysis of spatial-dependent cosmic-ray propagation: astrophysical background of antiprotons and positrons |
we analyse the illustristng simulations to study the mass, volume fraction, and phase distribution of gaseous baryons embedded in the knots, filaments, sheets, and voids of the cosmic web from redshift z = 8 to redshift z = 0. we find that filaments host more star-forming gas than knots, and that filaments also have a higher relative mass fraction of gas in this phase than knots. we also show that the cool, diffuse intergalactic medium [igm; t< 10^5 k, n_h< 10^{-4}(1+z) cm^{-3}] and the warm-hot intergalactic medium [whim; 10^5 < t< 10^7 k, n_h < 10^{-4}(1+z) cm^{-3}] constitute {∼ } 39 and {∼ } 46{{ per cent}} of the baryons at redshift z = 0, respectively. our results indicate that the whim may constitute the largest reservoir of missing baryons at redshift z = 0. using our cosmic web classification, we predict the whim to be the dominant baryon mass contribution in filaments and knots at redshift z = 0, but not in sheets and voids where the cool, diffuse igm dominates. we also characterize the evolution of whim and igm from redshift z = 4 to redshift z = 0, and find that the mass fraction of whim in filaments and knots evolves only by a factor of ∼2 from redshift z = 0 to 1, but declines faster at higher redshift. the whim only occupies 4-11 per cent of the volume at redshift 0 ≤ z ≤ 1. we predict the existence of a significant number of currently undetected o vii and ne ix absorption systems in cosmic filaments, which could be detected by future x-ray telescopes like athena. | baryons in the cosmic web of illustristng - i: gas in knots, filaments, sheets, and voids |
primordial black holes (pbhs) with a mass m ≲1 017 g are expected to inject sub-gev electrons and positrons in the galaxy via hawking radiation. these cosmic rays are shielded by the solar magnetic field for earth-bound detectors, but not for voyager 1, which is now beyond the heliopause. we use its data to constrain the fraction of pbhs to the dark matter in the galaxy, finding that pbhs with m <1016 g cannot contribute more than 0.1% (or less for a log-normal mass distribution). our limits are based on local galactic measurements and are thus complementary to those derived from cosmological observations. | voyager 1 e± further constrain primordial black holes as dark matter |
extended results on the cosmic-ray electron + positron spectrum from 11 gev to 4.8 tev are presented based on observations with the calorimetric electron telescope (calet) on the international space station utilizing the data up to november 2017. the analysis uses the full detector acceptance at high energies, approximately doubling the statistics compared to the previous result. calet is an all-calorimetric instrument with a total thickness of 30 x0 at normal incidence and fine imaging capability, designed to achieve large proton rejection and excellent energy resolution well into the tev energy region. the observed energy spectrum in the region below 1 tev shows good agreement with alpha magnetic spectrometer (ams-02) data. in the energy region below ∼300 gev , calet's spectral index is found to be consistent with the ams-02, fermi large area telescope (fermi-lat), and dark matter particle explorer (dampe), while from 300 to 600 gev the spectrum is significantly softer than the spectra from the latter two experiments. the absolute flux of calet is consistent with other experiments at around a few tens of gev. however, it is lower than those of dampe and fermi-lat with the difference increasing up to several hundred gev. the observed energy spectrum above ∼1 tev suggests a flux suppression consistent within the errors with the results of dampe, while calet does not observe any significant evidence for a narrow spectral feature in the energy region around 1.4 tev. our measured all-electron flux, including statistical errors and a detailed breakdown of the systematic errors, is tabulated in the supplemental material in order to allow more refined spectral analyses based on our data. | extended measurement of the cosmic-ray electron and positron spectrum from 11 gev to 4.8 tev with the calorimetric electron telescope on the international space station |
the hypothesis that the late universe is isotropic and homogeneous is adopted by most cosmological studies, including studies of galaxy clusters. the cosmic expansion rate h0 is thought to be spatially constant, while bulk flows are often presumed to be negligible compared to the hubble expansion, even at local scales. the effects of bulk flows on the redshift-distance conversion are hence usually ignored. any deviation from this consensus can strongly bias the results of such studies, and thus the importance of testing these assumptions cannot be understated. scaling relations of galaxy clusters can be effectively used for this testing. in previous works, we observed strong anisotropies in cluster scaling relations, whose origins remain ambiguous. by measuring many different cluster properties, several scaling relations with different sensitivities can be built. nearly independent tests of cosmic isotropy and large bulk flows are then feasible. in this work, we make use of up to 570 clusters with measured properties at x-ray, microwave, and infrared wavelengths to construct ten different cluster scaling relations and test the isotropy of the local universe; to our knowedge, we present five of these scaling relations for the first time. through rigorous and robust tests, we ensure that our analysis is not prone to generally known systematic biases and x-ray absorption issues. by combining all available information, we detect an apparent 9% spatial variation in the local h0 between (l, b)∼(280°−35°+35°, −15°−20°+20°) and the rest of the sky. the observed anisotropy has a nearly dipole form. using isotropic monte carlo simulations, we assess the statistical significance of the anisotropy to be > 5σ. this result could also be attributed to a ∼900 km s−1 bulk flow, which seems to extend out to at least ∼500 mpc. these two effects will be indistinguishable until more high-z clusters are observed by future all-sky surveys such as erosita. | cosmological implications of the anisotropy of ten galaxy cluster scaling relations |
direct detection experiments relying on nuclear recoil signatures lose sensitivity to sub-gev dark matter for typical galactic velocities. this sensitivity is recovered if there exists another source of flux with higher momenta. such an energetic flux of light dark matter could originate from the decay of mesons produced in inelastic cosmic ray collisions. we compute this novel production mechanism—a cosmic beam dump experiment—and estimate the resulting limits from xenon1t and lz. we find that the dark matter flux from inelastic cosmic rays colliding with atmospheric nuclei can dominate over the flux from elastic collisions with relic dark matter. the limits that we obtain for hadrophilic scalar mediator models are competitive with those from miniboone for light mev-scale mediator masses. | detecting light dark matter via inelastic cosmic ray collisions |
we use super-k data to place new strong limits on interactions of sub-gev dark matter (dm) with nuclei, that rely on the dm flux inevitably induced by cosmic-ray upscatterings. we derive analogous sensitivities at hyper-k and dune and compare them with others, e.g. at juno. using simplified models, we find that our proposal tests genuinely new parameter space, allowed both by theoretical consistency and by other direct detection experiments, cosmology, meson decays and our recast of monojet. our results thus motivate and shape a new physics case for any large volume detector sensitive to nuclear recoils. | neutrino experiments probe hadrophilic light dark matter |
we present a measurement of the cosmic-ray electron +positron spectrum between 7 gev and 2 tev performed with almost seven years of data collected with the fermi large area telescope. we find that the spectrum is well fit by a broken power law with a break energy at about 50 gev. above 50 gev, the spectrum is well described by a single power law with a spectral index of 3.07 ±0.02 (stat +syst )±0.04 (energy measurement) . an exponential cutoff lower than 1.8 tev is excluded at 95% cl. | cosmic-ray electron-positron spectrum from 7 gev to 2 tev with the fermi large area telescope |
contributions of the pierre auger collaboration to the 34th international cosmic ray conference, 30 july - 6 august 2015, the hague, the netherlands | the pierre auger observatory: contributions to the 34th international cosmic ray conference (icrc 2015) |
the measurement of the energy spectrum of cosmic ray helium nuclei from 70 gev to 80 tev using 4.5 years of data recorded by the dark matter particle explorer (dampe) is reported in this work. a hardening of the spectrum is observed at an energy of about 1.3 tev, similar to previous observations. in addition, a spectral softening at about 34 tev is revealed for the first time with large statistics and well controlled systematic uncertainties, with an overall significance of 4.3 σ . the dampe spectral measurements of both cosmic protons and helium nuclei suggest a particle charge dependent softening energy, although with current uncertainties a dependence on the number of nucleons cannot be ruled out. | measurement of the cosmic ray helium energy spectrum from 70 gev to 80 tev with the dampe space mission |
cosmogenic neutrinos are produced when ultrahigh-energy cosmic rays (uhecrs) interact with cosmological photon fields. limits on the diffuse flux of these neutrinos can be used to constrain the fraction of protons arriving at earth with energies ep≳30 eev , thereby providing bounds on the composition of uhecrs without fully relying on hadronic interaction models. we show to which extent current neutrino telescopes already constrain this fraction of protons and discuss the prospects for next-generation detectors to further constrain it. additionally, we discuss the implications of these limits for several popular candidates for uhecr source classes. | determining the fraction of cosmic-ray protons at ultrahigh energies with cosmogenic neutrinos |
data from the nucleon space observatory give a strong indication of the existence of a new universal cosmic ray "knee", which is observed in all groups of nuclei, including heavy nuclei, near a magnetic rigidity of about 10 tv. universality means the same position of the knee in the magnetic rigidity scale for all groups of nuclei. the knee is observed by both methods of measurement of particles energy implemented in the nucleon observatory—the calorimetric method and the kinematic method kinematic lightweight energy meter. this new cosmic ray knee is probably connected with the limit of acceleration of cosmic rays by some generic or nearby source of cosmic rays. | new universal cosmic-ray knee near a magnetic rigidity of 10 tv with the nucleon space observatory |
the large high altitude air shower observatory (lhaaso) (fig. 1) is located at mt. haizi (4410 m a.s.l., 600 g/cm2, 29° 21' 27.56" n, 100° 08' 19.66" e) in daocheng, sichuan province, p.r. china. lhaaso consists of 1.3 km2 array (km2a) of electromagnetic particle detectors (ed) and muon detectors (md), a water cherenkov detector array (wcda) with a total active area of 78,000 m2, 18 wide field-of-view air cherenkov telescopes (wfcta) and a newly proposed electron-neutron detector array (enda) covering 10,000 m2. each detector is synchronized with all the other through a clock synchronization network based on the white rabbit protocol. the observatory includes an it center which comprises the data acquisition system and trigger system, the data analysis facility. in this chapter, all the above-mentioned components of lhaaso as well as infrastructure are described. * supported by national natural science foundation in china (nsfc) (u2031103, u1831208, 11805209, 11775233), nsfc for distinguished young scholars (12025502), the science and technology department of sichuan province (2021yfsy0031) and the international partnership program of chinese academy of sciences (113111kysb20170055) | chapter 1 lhaaso instruments and detector technology |
we present maddm v.3.0, a numerical tool to compute particle dark matter observables in generic new physics models. the new version features a comprehensive and automated framework for dark matter searches at the interface of collider physics, astrophysics and cosmology and is deployed as a plugin of the madgraph5_amc@nlo platform, inheriting most of its features. with respect to the previous version, maddm v.3.0 can now provide predictions for indirect dark matter signatures in astrophysical environments, such as the annihilation cross section at present time and the energy spectra of prompt photons, cosmic rays and neutrinos resulting from dark matter annihilation. maddm indirect detection features support both 2 → 2 and 2 → n dark matter annihilation processes. in addition, the ability to compare theoretical predictions with experimental constraints is extended by including the fermi-lat likelihood for gamma-ray constraints from dwarf spheroidal galaxies and by providing an interface with the nested sampling algorithm pymultinest to perform high dimensional parameter scans efficiently. we validate the code for a wide set of dark matter models by comparing the results from maddm v.3.0 to existing tools and results in the literature. | maddm v.3.0: a comprehensive tool for dark matter studies |
imaging methods based on the absorption or scattering of atmospheric muons, collectively named under the neologism "muography", exploit the abundant natural flux of muons produced from cosmic-ray interactions in the atmosphere. recent years have seen a steep rise in the development of muography methods in a variety of innovative multidisciplinary approaches to study the interior of natural or human-made structures, establishing synergies between usually disconnected academic disciplines such as particle physics, geology, and archaeology. muography also bears promise of immediate societal impact through geotechnical investigations, nuclear waste surveys, homeland security, and natural hazard monitoring. our aim is to provide an introduction to this vibrant research area, starting from the physical principles at the basis of the methods and describing the main detector technologies and imaging tools, including their combination with conventional techniques from other disciplines, where appropriate. then, we discuss critically some outstanding issues that affect a broad variety of applications, and the current state of the art in addressing them. finally, we review several recent developments in the application of muography methods to specific use cases, without any pretence of exhaustiveness. | atmospheric muons as an imaging tool |
we report a quasidifferential upper limit on the extremely-high-energy (ehe) neutrino flux above 5 ×106 gev based on an analysis of nine years of icecube data. the astrophysical neutrino flux measured by icecube extends to pev energies, and it is a background flux when searching for an independent signal flux at higher energies, such as the cosmogenic neutrino signal. we have developed a new method to place robust limits on the ehe neutrino flux in the presence of an astrophysical background, whose spectrum has yet to be understood with high precision at pev energies. a distinct event with a deposited energy above 1 06 gev was found in the new two-year sample, in addition to the one event previously found in the seven-year ehe neutrino search. these two events represent a neutrino flux that is incompatible with predictions for a cosmogenic neutrino flux and are considered to be an astrophysical background in the current study. the obtained limit is the most stringent to date in the energy range between 5 ×106 and 2 ×1010 gev . this result constrains neutrino models predicting a three-flavor neutrino flux of eν2ϕνe+νμ+ντ≃2 ×10-8 gev /cm2 sec sr at 1 09 gev . a significant part of the parameter space for ehe neutrino production scenarios assuming a proton-dominated composition of ultra-high-energy cosmic rays is disfavored independently of uncertain models of the extragalactic background light which previous icecube constraints partially relied on. | differential limit on the extremely-high-energy cosmic neutrino flux in the presence of astrophysical background from nine years of icecube data |
in this work we present the interpretation of the energy spectrum and mass composition data as measured by the pierre auger collaboration above 6 × 1017 ev. we use an astrophysical model with two extragalactic source populations to model the hardening of the cosmic-ray flux at around 5 × 1018 ev (the so-called "ankle" feature) as a transition between these two components. we find our data to be well reproduced if sources above the ankle emit a mixed composition with a hard spectrum and a low rigidity cutoff. the component below the ankle is required to have a very soft spectrum and a mix of protons and intermediate-mass nuclei. the origin of this intermediate-mass component is not well constrained and it could originate from either galactic or extragalactic sources. to the aim of evaluating our capability to constrain astrophysical models, we discuss the impact on the fit results of the main experimental systematic uncertainties and of the assumptions about quantities affecting the air shower development as well as the propagation and redshift distribution of injected ultra-high-energy cosmic rays (uhecrs). | constraining the sources of ultra-high-energy cosmic rays across and above the ankle with the spectrum and composition data measured at the pierre auger observatory |
the recently reported excess in xenon1t is explained by new leptonic forces, which are free from gauge anomalies. we focus on two scenarios with and without dark matter. in scenario #1, the gauge boson of gauged lepton number u(1)le-lj, j = μ or τ provides non-standard interaction between solar neutrino and electron that enhances the number of electron recoil events in the xenon1t detector. in scenarino #2, the new gauge boson exclusively couples to electron and dark matter, then cosmic-ray electrons can transfer their momenta to dark matter in halo. the boosted dark matter generates the electron recoil signals of o (1) kev. the dark matter, aided by the new gauge interaction, efficiently heats up a neutron star in our galaxy more than ∼1500 k as a neutron star captures the halo dark matter. therefore, we propose to utilize the future infrared telescope to test our scenario. scenario #1: the solar neutrinos can interact with electrons in the xenon1t detector by the exchange of the new gauge boson x and generate signals [30]. the gauged symmetry u(1)le-li with i = μ or τ is chosen scenario #2: the dark matter, as well as electron, couples with the new gauge boson x. the dm particles boosted by cosmic-ray electrons [34-37] can interact with electrons in the xenon1t detector and produce the observed excessive signals. | leptonic new force and cosmic-ray boosted dark matter for the xenon1t excess |
light halo dark matter (dm) particles up-scattered by high-energy cosmic rays (referred to as crdm) can be energetic and become detectable at conventional dm and neutrino experiments. we show that the crdm flux has a novel and detectable morphological feature. unlike most of the recently proposed boosted dm models, which predict azimuthally symmetric dm fluxes around the galactic center, the crdm flux breaks the azimuthal symmetry significantly. using cosmic-ray electron distribution in the whole galaxy and optimized search region in the sky according to the morphology of the crdm flux, we derive, so far, the most stringent constraints on the dm-electron scattering cross section from the super-kamiokande (sk) iv data, which improves the previous constraints from the sk-iv full-sky data by more than an order of magnitude. based on the improved constraints, we predict that the azimuthal symmetry-breaking effect can be observed in the future hyper-kamiokande experiment at ∼3 σ level. | azimuthal asymmetry in cosmic-ray boosted dark matter flux |
the physics of energetic particle propagation in magnetized environments plays a crucial role in both the processes of acceleration and transport of cosmic rays. recent theoretical developments in the field of cosmic ray research have been mainly in the direction of exploring non-linear aspects of the processes in which these particles are involved, namely the action of cosmic rays on the environment in which the transport and/or acceleration take place. when cosmic rays propagate outside of the acceleration region, such action is mainly in two forms: (1) they generate hydromagnetic waves, through streaming instabilities, leading to a dependence of the scattering properties of the medium on the spectrum and spatial distribution of the energetic particles, and (2) they exert a dynamical action on the plasma, which may cause the launching of cosmic ray driven galactic winds. in this article we discuss these and other recent developments and how they compare with the bulk of new observations on the spectra of primary nuclei (mainly h and he) and secondary to primary ratios, such as the b/c ratio and the p bar / p ratio, and the positrons ratio e+ / (e- +e+) . we also comment on some radically new models of the origin of crs, in which the physical meaning of the secondary to primary ratios is not the same as in the standard model. | cosmic ray transport in the galaxy: a review |
the recoil threshold of direct detection (dd) experiments limits the mass range of dark matter (dm) particles that can be detected, with most dd experiments being blind to sub-mev dm particles. however, these light dm particles can be boosted to very high energies via collisions with energetic cosmic ray electrons. this allows dark matter particles to induce detectable recoil in the target of direct detection experiments. we derive constraints on a scattering cross section of dm and an electron, using xenonnt and super-kamiokande data. vector and scalar mediators are considered in the heavy and light regimes. we discuss the importance of including energy-dependent cross sections (due to the specific lorentz structure of the vertex) in our analysis and show that the bounds can be significantly different than the results obtained assuming a constant energy-independent cross section, often assumed in the literature for simplicity. our bounds are also compared with other astrophysical and cosmological constraints. | bounds on boosted dark matter from direct detection: the role of energy-dependent cross sections |
it has been reported that the large high altitude air shower observatory (lhaaso) observed very high energy photons from grb 221009a, with the highest energy reaching 18 tev. we find that observation of such high energy photons is quite nontrivial since extragalactic background light could absorb these photons severely and the flux is too weak to be observed. therefore we discuss a potential mechanism for us to observe these photons, and suggest that lorentz invariance violation induced threshold anomaly of the process γγ →e-e+ provides a candidate to explain this phenomenon. | lorentz invariance violation induced threshold anomaly versus very-high energy cosmic photon emission from grb 221009a |
we present the dissection in space, time, and energy of the region around the icecube-170922a neutrino alert. this study is motivated by: (1) the first association between a neutrino alert and a blazar in a flaring state, txs 0506+056; (2) the evidence of a neutrino flaring activity during 2014-2015 from the same direction; (3) the lack of an accompanying simultaneous γ-ray enhancement from the same counterpart; (4) the contrasting flaring activity of a neighbouring bright γ-ray source, the blazar pks 0502+049, during 2014-2015. our study makes use of multiwavelength archival data accessed through open universe tools and includes a new analysis of fermi-lat data. we find that pks 0502+049 contaminates the γ-ray emission region at low energies but txs 0506+056 dominates the sky above a few gev. txs 0506+056, which is a very strong (top percent) radio and γ-ray source, is in a high γ-ray state during the neutrino alert but in a low though hard γ-ray state in coincidence with the neutrino flare. both states can be reconciled with the energy associated with the neutrino emission and, in particular during the low/hard state, there is evidence that txs 0506+056 has undergone a hadronic flare with very important implications for blazar modelling. all multimessenger diagnostics reported here support a single coherent picture in which txs 0506+056, a very high energy γ-ray blazar, is the only counterpart of all the neutrino emissions in the region and therefore the most plausible first non-stellar neutrino and, hence, cosmic ray source. | dissecting the region around icecube-170922a: the blazar txs 0506+056 as the first cosmic neutrino source |
contributions of the pierre auger collaboration to the 35th international cosmic ray conference (icrc 2017), 12-20 july 2017, bexco, busan, korea. | the pierre auger observatory: contributions to the 35th international cosmic ray conference (icrc 2017) |
the light emitted by all galaxies over the history of the universe produces the extragalactic background light (ebl) at ultraviolet, optical, and infrared wavelengths. the ebl is a source of opacity for gamma rays via photon-photon interactions, leaving an imprint in the spectra of distant gamma-ray sources. we measured this attenuation using 739 active galaxies and one gamma-ray burst detected by the fermi large area telescope. this allowed us to reconstruct the evolution of the ebl and determine the star formation history of the universe over 90% of cosmic time. our star formation history is consistent with independent measurements from galaxy surveys, peaking at redshift z ~ 2. upper limits of the ebl at the epoch of reionization suggest a turnover in the abundance of faint galaxies at z ~ 6. | a gamma-ray determination of the universe's star formation history |
on the largest scales, the universe consists of voids and filaments making up the cosmic web. galaxy clusters are located at the knots in this web, at the intersection of filaments. clusters grow through accretion from these large-scale filaments and by mergers with other clusters and groups. in a growing number of galaxy clusters, elongated mpc-sized radio sources have been found1,2 . also known as radio relics, these regions of diffuse radio emission are thought to trace relativistic electrons in the intracluster plasma accelerated by low-mach-number shocks generated by cluster-cluster merger events 3 . a long-standing problem is how low-mach-number shocks can accelerate electrons so efficiently to explain the observed radio relics. here, we report the discovery of a direct connection between a radio relic and a radio galaxy in the merging galaxy cluster abell 3411-3412 by combining radio, x-ray and optical observations. this discovery indicates that fossil relativistic electrons from active galactic nuclei are re-accelerated at cluster shocks. it also implies that radio galaxies play an important role in governing the non-thermal component of the intracluster medium in merging clusters. | the case for electron re-acceleration at galaxy cluster shocks |
very recently, it was pointed out that when basic ideas of the swampland program are combined with the cosmological hierarchy problem (i.e., the smallness of the dark energy in planck units) and together are confronted to experiment lead to the prediction of the existence of a single extra-dimension (dubbed the dark dimension) with characteristic length-scale in the micron range. we propose a feasible test procedure to probe the dark dimension using the highest energy cosmic rays. | dark dimension, the swampland, and the origin of cosmic rays beyond the greisen-zatsepin-kuzmin barrier |
we present measurements of the evolution of normal-galaxy x-ray emission from z\quad ≈ 0-7 using local galaxies and galaxy samples in the ≈6 ms chandra deep field-south (cdf-s) survey. the majority of the cdf-s galaxies are observed at rest-frame energies above 2 kev, where the emission is expected to be dominated by x-ray binary (xrb) populations; however, hot gas is expected to provide small contributions to the observed-frame ≲1 kev emission at z ≲ 1. we show that a single scaling relation between x-ray luminosity ({l}{{x}}) and star-formation rate (sfr) literature, is insufficient for characterizing the average x-ray emission at all redshifts. we establish that scaling relations involving not only sfr, but also stellar mass ({m}\star ) and redshift, provide significantly improved characterizations of the average x-ray emission from normal galaxy populations at z\quad ≈ 0-7. we further provide the first empirical constraints on the redshift evolution of x-ray emission from both low-mass xrb (lmxb) and high-mass xrb (hmxb) populations and their scalings with {m}\starand sfr, respectively. we find {l}2-10{kev}(lmxb)/{m}\star \propto {(1+z)}2-3 and {l}2-10{kev}(hmxb)/sfr \propto \quad (1+z), and show that these relations are consistent with xrb population-synthesis model predictions, which attribute the increase in lmxb and hmxb scaling relations with redshift as being due to declining host galaxy stellar ages and metallicities, respectively. we discuss how emission from xrbs could provide an important source of heating to the intergalactic medium in the early universe, exceeding that of active galactic nuclei. | the evolution of normal galaxy x-ray emission through cosmic history: constraints from the 6 ms chandra deep field-south |
we present the source associations, cross-identifications, and multi-wavelength properties of the faint radio source population detected in the deep tier of the lofar two metre sky survey (lotss): the lotss deep fields. the first lotss deep fields data release consists of deep radio imaging at 150 mhz of the elais-n1, lockman hole, and boötes fields, down to rms sensitives of around 20, 22, and 32 μjy beam−1, respectively. these fields are some of the best studied extra-galactic fields in the northern sky, with existing deep, wide-area panchromatic photometry from x-ray to infrared wavelengths, covering a total of ≈26 deg2. we first generated improved multi-wavelength catalogues in elais-n1 and lockman hole; combined with the existing catalogue for boötes, we present forced, matched aperture photometry for over 7.2 million sources across the three fields. we identified multi-wavelength counterparts to the radio detected sources, using a combination of the likelihood ratio method and visual classification, which greatly enhances the scientific potential of radio surveys and allows for the characterisation of the photometric redshifts and the physical properties of the host galaxies. the final radio-optical cross-matched catalogue consists of 81 951 radio-detected sources, with counterparts identified and multi-wavelength properties presented for 79 820 (>97%) sources. we also examine the properties of the host galaxies, and through stacking analysis find that the radio population with no identified counterpart is likely dominated by active galactic nuclei (agn) at z ~ 3−4. this dataset contains one of the largest samples of radio-selected star-forming galaxies and agn at these depths, making it ideal for studying the history of star-formation, and the evolution of galaxies and agn across cosmic time. the catalogues are only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/648/a3 the value-added catalogues are available at https://lofar-surveys.org/ as part of this data release. | the lofar two-meter sky survey: deep fields data release 1. iii. host-galaxy identifications and value added catalogues |
in this paper, we present the analysis and results of a direct measurement of the cosmic-ray proton spectrum with the calet instrument onboard the international space station, including the detailed assessment of systematic uncertainties. the observation period used in this analysis is from october 13, 2015 to august 31, 2018 (1054 days). we have achieved the very wide energy range necessary to carry out measurements of the spectrum from 50 gev to 10 tev covering, for the first time in space, with a single instrument the whole energy interval previously investigated in most cases in separate subranges by magnetic spectrometers (bess-tev, pamela, and ams-02) and calorimetric instruments (atic, cream, and nucleon). the observed spectrum is consistent with ams-02 but extends to nearly an order of magnitude higher energy, showing a very smooth transition of the power-law spectral index from -2.81 ±0.03 (50-500 gev) neglecting solar modulation effects (or -2.87 ±0.06 including solar modulation effects in the lower energy region) to -2.56 ±0.04 (1-10 tev), thereby confirming the existence of spectral hardening and providing evidence of a deviation from a single power law by more than 3 σ . | direct measurement of the cosmic-ray proton spectrum from 50 gev to 10 tev with the calorimetric electron telescope on the international space station |
galaxy clusters are the endpoints of structure formation and are continuously growing through the merging and accretion of smaller structures. numerical simulations predict that a fraction of their energy content is not yet thermalized, mainly in the form of kinetic motions (turbulence, bulk motions). measuring the level of non-thermal pressure support is necessary to understand the processes leading to the virialization of the gas within the potential well of the main halo and to calibrate the biases in hydrostatic mass estimates. we present high-quality measurements of hydrostatic masses and intracluster gas fraction out to the virial radius for a sample of 13 nearby clusters with available xmm-newton and planck data. we compare our hydrostatic gas fractions with the expected universal gas fraction to constrain the level of non-thermal pressure support. we find that hydrostatic masses require little correction and infer a median non-thermal pressure fraction of ∼6% and ∼10% at r500 and r200, respectively. our values are lower than the expectations of hydrodynamical simulations, possibly implying a faster thermalization of the gas. if instead we use the mass calibration adopted by the planck team, we find that the gas fraction of massive local systems implies a mass bias 1 - b = 0.85 ± 0.05 for sunyaev-zeldovich-derived masses, with some evidence for a mass-dependent bias. conversely, the high bias required to match planck cosmic microwave background and cluster count cosmology is excluded by the data at high significance, unless the most massive halos are missing a substantial fraction of their baryons. | non-thermal pressure support in x-cop galaxy clusters |
we investigate the impact of cosmic rays (crs) and different modes of cr transport on the properties of milky way-mass galaxies in cosmological magnetohydrodynamical simulations in the context of the auriga project. we systematically study how advection, anisotropic diffusion, and additional alfvén-wave cooling affect the galactic disc and the circumgalactic medium (cgm). global properties such as stellar mass and star formation rate vary little between simulations with and without various cr transport physics, whereas structural properties such as disc sizes, cgm densities, or temperatures can be strongly affected. in our simulations, crs affect the accretion of gas on to galaxies by modifying the cgm flow structure. this alters the angular momentum distribution that manifests itself as a difference in stellar and gaseous disc size. the strength of this effect depends on the cr transport model: cr advection results in the most compact discs while the alfvén-wave model resembles more the auriga model. the advection and diffusion models exhibit large (r ~ 50 kpc) cr pressure-dominated gas haloes causing a smoother and partly cooler cgm. the additional cr pressure smoothes small-scale density peaks and compensates for the missing thermal pressure support at lower cgm temperatures. in contrast, the alfvén-wave model is only cr pressure dominated at the disc-halo interface and only in this model the gamma-ray emission from hadronic interactions agrees with observations. in contrast to previous findings, we conclude that details of cr transport are critical for accurately predicting the impact of cr feedback on galaxy formation. | the effects of cosmic rays on the formation of milky way-mass galaxies in a cosmological context |
large liquid argon time projection chambers (lartpcs), especially those operating near the surface, are susceptible to space charge effects. in the context of lartpcs, the space charge effect is the build-up of slow-moving positive ions in the detector primarily due to ionization from cosmic rays, leading to a distortion of the electric field within the detector. this effect leads to a displacement in the reconstructed position of signal ionization electrons in lartpc detectors ("spatial distortions"), as well as to variations in the amount of electron-ion recombination experienced by ionization throughout the volume of the tpc. we present techniques that can be used to measure and correct for space charge effects in large lartpcs by making use of cosmic muons, including the use of track pairs to unambiguously pin down spatial distortions in three dimensions. the performance of these calibration techniques are studied using both monte carlo simulation and microboone data, utilizing a uv laser system as a means to estimate the systematic bias associated with the calibration methodology. | measurement of space charge effects in the microboone lartpc using cosmic muons |
the auger engineering radio array (aera) is part of the pierre auger observatory and is used to detect the radio emission of cosmic-ray air showers. these observations are compared to the data of the surface detector stations of the observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. the response of the radio stations in the 30-80 mhz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. for the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. the spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the aera frequency range. we measure 15.8 mev of radiation energy for a 1 eev air shower arriving perpendicularly to the geomagnetic field. this radiation energy—corrected for geometrical effects—is used as a cosmic-ray energy estimator. performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. we find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal. | energy estimation of cosmic rays with the engineering radio array of the pierre auger observatory |
the inner few hundred parsecs of the milky way harbours gas densities, pressures, velocity dispersions, an interstellar radiation field and a cosmic ray ionization rate orders of magnitude higher than the disc; akin to the environment found in star-forming galaxies at high redshift. previous studies have shown that this region is forming stars at a rate per unit mass of dense gas which is at least an order of magnitude lower than in the disc, potentially violating theoretical predictions. we show that all observational star formation rate diagnostics - both direct counting of young stellar objects and integrated light measurements - are in agreement within a factor two, hence the low star formation rate (sfr) is not the result of the systematic uncertainties that affect any one method. as these methods trace the star formation over different time-scales, from 0.1 to 5 myr, we conclude that the sfr has been constant to within a factor of a few within this time period. we investigate the progression of star formation within gravitationally bound clouds on ∼parsec scales and find 1-4 per cent of the cloud masses are converted into stars per free-fall time, consistent with a subset of the considered 'volumetric' star formation models. however, discriminating between these models is obstructed by the current uncertainties on the input observables and, most importantly and urgently, by their dependence on ill-constrained free parameters. the lack of empirical constraints on these parameters therefore represents a key challenge in the further verification or falsification of current star formation theories. | star formation rates and efficiencies in the galactic centre |
accurate analyses of present and next-generation cosmological galaxy surveys require new ways to handle effects of non-linear gravitational structure formation processes in data. to address these needs we present an extension of our previously developed algorithm for bayesian origin reconstruction from galaxies (borg) to analyse matter clustering at non-linear scales in observations. this is achieved by incorporating a numerical particle mesh model of gravitational structure formation into our bayesian inference framework. the algorithm simultaneously infers the three-dimensional primordial matter fluctuations from which present non-linear observations formed and provides reconstructions of velocity fields and structure formation histories. the physical forward modelling approach automatically accounts for the non-gaussian features in gravitationally evolved matter density fields and addresses the redshift space distortion problem associated with peculiar motions of observed galaxies. our algorithm employs a hierarchical bayes approach to jointly account for various observational effects, such as unknown galaxy biases, selection effects, and observational noise. corresponding parameters of the data model are marginalized out via a sophisticated markov chain monte carlo approach relying on a combination of a multiple block sampling framework and an efficient implementation of a hamiltonian monte carlo sampler. we demonstrate the performance of the method by applying it to the 2m++ galaxy compilation, tracing the matter distribution of the nearby universe. we show accurate and detailed inferences of the three-dimensional non-linear dark matter distribution of the nearby universe. as exemplified in the case of the coma cluster, our method provides complementary mass estimates that are compatible with those obtained from weak lensing and x-ray observations. for the first time, we also present a reconstruction of the vorticity of the non-linear velocity field from observations. in summary, our method provides plausible and very detailed inferences of the dark matter and velocity fields of our cosmic neighbourhood. | physical bayesian modelling of the non-linear matter distribution: new insights into the nearby universe |
understanding the formation and evolution of the first stars and galaxies represents one of the most exciting frontiers in astronomy. since the universe was filled with hydrogen atoms at early times, the most promising method for observing the epoch of the first stars is to use the prominent 21-cm spectral line of hydrogen. current observational efforts are focused on the cosmic reionization era, but observations of the pre-reionization cosmic dawn are also beginning and promise exciting discoveries. while observationally unexplored, theoretical studies predict a rich variety of observational signatures from the astrophysics of the early galaxies that formed during cosmic dawn. as the first stars formed, their radiation (plus that from stellar remnants) produced feedback that radically affected both the intergalactic medium and the character of newly-forming stars. lyman- α radiation from stars generated a strong 21-cm absorption signal, observation of which is currently the only feasible method of detecting the dominant population of galaxies at redshifts as early as z ∼ 25. another major player is cosmic heating; if due to soft x-rays, then it occurred fairly early (z ∼ 15) and produced the strongest pre-reionization signal, while if it is due to hard x-rays, as now seems more likely, then it occurred later and may have dramatically affected the 21-cm sky even during reionization. in terms of analysis, much focus has gone to studying the angle-averaged power spectrum of 21-cm fluctuations, a rich dataset that can be used to reconstruct the astrophysical information of greatest interest. this does not, however, diminish the importance of finding additional probes that are complementary or amenable to a more model-independent analysis. examples include the global (sky-averaged) 21-cm spectrum, and the line-of-sight anisotropy of the 21-cm power spectrum. another striking feature may result from a recently recognized effect of a supersonic relative velocity between the dark matter and gas. this effect enhanced large-scale clustering and, if early 21-cm fluctuations were dominated by small galactic halos, it produced a prominent pattern on 100 mpc scales. work in this field, focused on understanding the whole era of reionization and cosmic dawn with analytical models and numerical simulations, is likely to grow in intensity and importance, as the theoretical predictions are finally expected to confront 21-cm observations in the coming years. | the rise of the first stars: supersonic streaming, radiative feedback, and 21-cm cosmology |
precision results on cosmic-ray electrons are presented in the energy range from 0.5 gev to 1.4 tev based on 28.1 ×106 electrons collected by the alpha magnetic spectrometer on the international space station. in the entire energy range the electron and positron spectra have distinctly different magnitudes and energy dependences. the electron flux exhibits a significant excess starting from 42. 1-5.2+5.4 gev compared to the lower energy trends, but the nature of this excess is different from the positron flux excess above 25.2 ±1.8 gev . contrary to the positron flux, which has an exponential energy cutoff of 81 0-180+310 gev , at the 5 σ level the electron flux does not have an energy cutoff below 1.9 tev. in the entire energy range the electron flux is well described by the sum of two power law components. the different behavior of the cosmic-ray electrons and positrons measured by the alpha magnetic spectrometer is clear evidence that most high energy electrons originate from different sources than high energy positrons. | towards understanding the origin of cosmic-ray electrons |
we present a measurement of the atmospheric neutrino oscillation parameters using three years of data from the icecube neutrino observatory. the deepcore infill array in the center of icecube enables the detection and reconstruction of neutrinos produced by the interaction of cosmic rays in earth's atmosphere at energies as low as ∼5 gev . that energy threshold permits measurements of muon neutrino disappearance, over a range of baselines up to the diameter of the earth, probing the same range of l /eν as long-baseline experiments but with substantially higher-energy neutrinos. this analysis uses neutrinos from the full sky with reconstructed energies from 5.6 to 56 gev. we measure δ m322=2.31-0.13+0.11×10-3 ev2 and sin2θ23=0.5 1-0.09+0.07, assuming normal neutrino mass ordering. these results are consistent with, and of similar precision to, those from accelerator- and reactor-based experiments. | measurement of atmospheric neutrino oscillations at 6-56 gev with icecube deepcore |
a promising energy range to look for angular correlations between cosmic rays of extragalactic origin and their sources is at the highest energies, above a few tens of eev (1 eev ≡ 1018 ev). despite the flux of these particles being extremely low, the area of ~3000 km2 covered at the pierre auger observatory, and the 17 yr data-taking period of the phase 1 of its operations, have enabled us to measure the arrival directions of more than 2600 ultra-high-energy cosmic rays above 32 eev. we publish this data set, the largest available at such energies from an integrated exposure of 122,000 km2 sr yr, and search it for anisotropies over the 3.4π steradians covered with the observatory. evidence for a deviation in excess of isotropy at intermediate angular scales, with ~15° gaussian spread or ~25° top-hat radius, is obtained at the 4σ significance level for cosmic-ray energies above ~40 eev. | arrival directions of cosmic rays above 32 eev from phase one of the pierre auger observatory |
we present 108 full-sky gravitational lensing simulation data sets generated by performing multiple-lens plane ray-tracing through high-resolution cosmological n-body simulations. the data sets include full-sky convergence and shear maps from redshifts z = 0.05 to 5.3 at intervals of 150 {h}-1{mpc} comoving radial distance (corresponding to a redshift interval of {{δ }}z≃ 0.05 at the nearby universe), enabling the construction of a mock shear catalog for an arbitrary source distribution up to z = 5.3. the dark matter halos are identified from the same n-body simulations with enough mass resolution to resolve the host halos of the sloan digital sky survey (sdss) cmass and luminous red galaxies (lrgs). angular positions and redshifts of the halos are provided by a ray-tracing calculation, enabling the creation of a mock halo catalog to be used for galaxy-galaxy and cluster-galaxy lensing. the simulation also yields maps of gravitational lensing deflections for a source redshift at the last scattering surface, and we provide 108 realizations of lensed cosmic microwave background (cmb) maps in which the post-born corrections caused by multiple light scattering are included. we present basic statistics of the simulation data, including the angular power spectra of cosmic shear, cmb temperature and polarization anisotropies, galaxy-galaxy lensing signals for halos, and their covariances. the angular power spectra of the cosmic shear and cmb anisotropies agree with theoretical predictions within 5% up to {\ell }=3000 (or at an angular scale θ > 0.5 arcmin). the simulation data sets are generated primarily for the ongoing subaru hyper suprime-cam survey, but are freely available for download at http://cosmo.phys.hirosaki-u.ac.jp/takahasi/allsky_raytracing/. | full-sky gravitational lensing simulation for large-area galaxy surveys and cosmic microwave background experiments |
large reservoirs of cold (∼104 k) gas exist out to and beyond the virial radius in the circumgalactic medium (cgm) of all types of galaxies. photoionization modeling suggests that cold cgm gas has significantly lower densities than expected by theoretical predictions based on thermal pressure equilibrium with hot cgm gas. in this work, we investigate the impact of cosmic-ray physics on the formation of cold gas via thermal instability. we use idealized three-dimensional magnetohydrodynamic simulations to follow the evolution of thermally unstable gas in a gravitationally stratified medium. we find that cosmic-ray pressure lowers the density and increases the size of cold gas clouds formed through thermal instability. we develop a simple model for how the cold cloud sizes and the relative densities of cold and hot gas depend on cosmic-ray pressure. cosmic-ray pressure can help counteract gravity to keep cold gas in the cgm for longer, thereby increasing the predicted cold mass fraction and decreasing the predicted cold gas inflow rates. efficient cosmic-ray transport, by streaming or diffusion, redistributes cosmic-ray pressure from the cold gas to the background medium, resulting in cold gas properties that are in between those predicted by simulations with inefficient transport and simulations without cosmic rays. we show that cosmic rays can significantly reduce galactic accretion rates and resolve the tension between theoretical models and observational constraints on the properties of cold cgm gas. | the impact of cosmic rays on thermal instability in the circumgalactic medium |
we present several studies of convolutional neural networks applied to data coming from the microboone detector, a liquid argon time projection chamber (lartpc). the algorithms studied include the classification of single particle images, the localization of single particle and neutrino interactions in an image, and the detection of a simulated neutrino event overlaid with cosmic ray backgrounds taken from real detector data. these studies demonstrate the potential of convolutional neural networks for particle identification or event detection on simulated neutrino interactions. we also address technical issues that arise when applying this technique to data from a large lartpc at or near ground level. | convolutional neural networks applied to neutrino events in a liquid argon time projection chamber |
we present the first results of one extremely high resolution, non-radiative magnetohydrodynamical cosmological zoom-in simulation of a massive cluster with a virial mass m$_\mathrm{vir} = 2.0 \times 10^{15}$ solar masses. we adopt a mass resolution of $4 \times 10^5$ m$_{\odot}$ with a maximum spatial resolution of around 250 pc in the central regions of the cluster. we follow the detailed amplification process in a resolved small-scale turbulent dynamo in the intracluster medium (icm) with strong exponential growth until redshift 4, after which the field grows weakly in the adiabatic compression limit until redshift 2. the energy in the field is slightly reduced as the system approaches redshift zero in agreement with adiabatic decompression. the field structure is highly turbulent in the center and shows field reversals on a length scale of a few 10 kpc and an anti-correlation between the radial and angular field components in the central region that is ordered by small-scale turbulent dynamo action. the large-scale field on mpc scales is almost isotropic, indicating that the structure formation process in massive galaxy cluster formation is suppressing memory of both the initial field configuration and the amplified morphology via the turbulent dynamo in the central regions. we demonstrate that extremely high-resolution simulations of the magnetized icm are in reach that can resolve the small-scale magnetic field structure which is of major importance for the injection of and transport of cosmic rays in the icm. this work is a major cornerstone for follow-up studies with an on-the-fly treatment of cosmic rays to model in detail electron-synchrotron and gamma-ray emissions. | towards cosmological simulations of the magnetized intracluster medium with resolved coulomb collision scale |
future cosmological measurements should enable the sum of neutrino masses to be determined indirectly through their effects on the expansion rate of the universe and the clustering of matter. we consider prospects for the gravitationally lensed cosmic microwave background (cmb) anisotropies and baryon acoustic oscillations (baos) in the galaxy distribution, examining how the projected uncertainty of ≈15 mev on the neutrino mass sum (a 4 σ detection of the minimal mass) might be reached over the next decade. the current 1 σ uncertainty of ≈103 mev (planck-2015 +bao -15 ) will be improved by upcoming "stage-3" (s3) cmb experiments (s 3 +bao -15 : 44 mev ), then upcoming bao measurements (s 3 +desi : 22 mev ), and planned next-generation "stage 4" (s4) cmb experiments (s 4 +desi : 15 - 19 mev , depending on angular range). an improved optical depth measurement is important: the projected neutrino mass uncertainty increases to 26 mev if s4 is limited to ℓ>20 and combined with current large-scale polarization data. looking beyond λ cdm , including curvature uncertainty increases the forecast mass error by ≈50 % for s 4 +desi , and more than doubles the error with a two-parameter dark-energy equation of state. complementary low-redshift probes including galaxy lensing will play a role in distinguishing between massive neutrinos and a departure from a w =-1 , flat geometry. | towards a cosmological neutrino mass detection |
utilizing the fermi measurement of the γ -ray spectrum toward the inner galaxy, we derive some of the strongest constraints to date on the dark matter (dm) lifetime in the mass range from hundreds of mev to above an eev. our profile-likelihood-based analysis relies on 413 weeks of fermi pass 8 data from 200 mev to 2 tev, along with up-to-date models for diffuse γ -ray emission within the milky way. we model galactic and extragalactic dm decay and include contributions to the dm-induced γ -ray flux resulting from both primary emission and inverse-compton scattering of primary electrons and positrons. for the extragalactic flux, we also calculate the spectrum associated with cascades of high-energy γ rays scattering off of the cosmic background radiation. we argue that a decaying dm interpretation for the 10 tev-1 pev neutrino flux observed by icecube is disfavored by our constraints. our results also challenge a decaying dm explanation of the ams-02 positron flux. we interpret the results in terms of individual final states and in the context of simplified scenarios such as a hidden-sector glueball model. | γ -ray constraints on decaying dark matter and implications for icecube |
lux-zeplin (lz) collaboration has achieved the strongest constraint on weak-scale dark matter (dm)-nucleon spin-independent (si) scattering cross section in a large region of parameter space. in this paper, we take a complementary approach and study the prospect of detecting cosmic-ray boosted sub-gev dm in lz. in the absence of a signal for dm, we improve upon the previous constraints by a factor of $\sim 2$ using the lz result for some regions of the parameter space. we also show that upcoming xenonnt and future darwin experiments will be sensitive to cross sections smaller by factors of $\sim 3$ and $\sim 10$ compared to the current lz limit, respectively. | cosmic-ray boosted dark matter in xe-based direct detection experiments |
context. the galactic center is the closest region where we can study star formation under extreme physical conditions like those in high-redshift galaxies.aims: we measure the temperature of the dense gas in the central molecular zone (cmz) and examine what drives it.methods: we mapped the inner 300 pc of the cmz in the temperature-sensitive j = 3-2 para-formaldehyde (p - h2co) transitions. we used the 32,1-22,0/ 30,3-20,2 line ratio to determine the gas temperature in n ~ 104-105 cm-3 gas. we have produced temperature maps and cubes with 30'' and 1 km s-1 resolution and published all data in fits form.results: dense gas temperatures in the galactic center range from ~60 k to >100 k in selected regions. the highest gas temperatures tg> 100 k are observed around the sgr b2 cores, in the extended sgr b2 cloud, the 20 km s-1 and 50 km s-1 clouds, and in "the brick" (g0.253+0.016). we infer an upper limit on the cosmic ray ionization rate ζcr< 10-14s-1.conclusions: the dense molecular gas temperature of the region around our galactic center is similar to values found in the central regions of other galaxies, in particular starburst systems. the gas temperature is uniformly higher than the dust temperature, confirming that dust is a coolant in the dense gas. turbulent heating can readily explain the observed temperatures given the observed line widths. cosmic rays cannot explain the observed variation in gas temperatures, so cmz dense gas temperatures are not dominated by cosmic ray heating. the gas temperatures previously observed to be high in the inner ~75 pc are confirmed to be high in the entire cmz. the data can be accessed from doi:10.7910/dvn/27601 and are available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/586/a50 | dense gas in the galactic central molecular zone is warm and heated by turbulence |
the magnetic fields observed in the milky way and nearby galaxies appear to be in equipartition with the turbulent, thermal and cosmic ray energy densities, and hence are expected to be dynamically important. however, the origin of these strong magnetic fields is still unclear, and most previous attempts to simulate galaxy formation from cosmological initial conditions have ignored them altogether. here, we analyse the magnetic fields predicted by the simulations of the auriga project, a set of 30 high-resolution cosmological zoom simulations of milky way like galaxies, carried out with a moving-mesh magnetohydrodynamics code and a detailed galaxy formation physics model. we find that the magnetic fields grow exponentially at early times owing to a small-scale dynamo with an e-folding time of roughly 100 myr in the centre of haloes until saturation occurs around z = 2-3, when the magnetic energy density reaches about 10 per cent of the turbulent energy density with a typical strength of $10\text{--}50\,\rm {\mu g}$. in the galactic centres, the ratio between magnetic and turbulent energies remains nearly constant until z = 0. at larger radii, differential rotation in the discs leads to linear amplification that typically saturates around z = 0.5-0. the final radial and vertical variations of the magnetic field strength can be well described by two joint exponential profiles, and are in good agreement with observational constraints. overall, the magnetic fields have only little effect on the global evolution of the galaxies as it takes too long to reach equipartition. we also demonstrate that our results are well converged with numerical resolution. | magnetic field formation in the milky way like disc galaxies of the auriga project |
we present a measurement of the cosmic-ray spectrum above 100 pev using the part of the surface detector of the pierre auger observatory that has a spacing of 750 m. an inflection of the spectrum is observed, confirming the presence of the so-called second-knee feature. the spectrum is then combined with that of the 1500 m array to produce a single measurement of the flux, linking this spectral feature with the three additional breaks at the highest energies. the combined spectrum, with an energy scale set calorimetrically via fluorescence telescopes and using a single detector type, results in the most statistically and systematically precise measurement of spectral breaks yet obtained. these measurements are critical for furthering our understanding of the highest energy cosmic rays. | the energy spectrum of cosmic rays beyond the turn-down around 1017 ev as measured with the surface detector of the pierre auger observatory |
we report on an upward traveling, radio-detected cosmic-ray-like impulsive event with characteristics closely matching an extensive air shower. this event, observed in the third flight of the antarctic impulsive transient antenna (anita), a nasa-sponsored long-duration balloon payload, is consistent with a similar event reported in a previous flight. these events could be produced by the atmospheric decay of an upward-propagating τ lepton produced by a ντ interaction, although their relatively steep arrival angles create tension with the standard model neutrino cross section. each of the two events have a posteriori background estimates of ≲10-2 events. if these are generated by τ -lepton decay, then either the charged-current ντ cross section is suppressed at eev energies, or the events arise at moments when the peak flux of a transient neutrino source was much larger than the typical expected cosmogenic background neutrinos. | observation of an unusual upward-going cosmic-ray-like event in the third flight of anita |
we present version 2 of the dragon code designed for computing realistic predictions of the cr densities in the galaxy. the code numerically solves the interstellar cr transport equation (including inhomogeneous and anisotropic diffusion, either in space and momentum, advective transport and energy losses), under realistic conditions. the new version includes an updated numerical solver and several models for the astrophysical ingredients involved in the transport equation. improvements in the accuracy of the numerical solution are proved against analytical solutions and in reference diffusion scenarios. the novel features implemented in the code allow to simulate the diverse scenarios proposed to reproduce the most recent measurements of local and diffuse cr fluxes, going beyond the limitations of the homogeneous galactic transport paradigm. to this end, several applications using dragon2 are presented as well. this new version facilitates the users to include their own physical models by means of a modular c++ structure. | cosmic-ray propagation with dragon2: i. numerical solver and astrophysical ingredients |
sediment accumulation rates and thermal trackers suggest a substantial and global increase in erosion rates over the past few million years. that increase is commonly associated with the impact of the northern hemisphere glaciation, but methodological biases have led researchers to debate this hypothesis. here, we test whether himalayan erosion rates increased by measuring beryllium-10 (10be) in the sediment of the bengal bay seabed. sediment originated from rocks that produced 10be under the impact of cosmic rays during erosion near surface. thus, the 10be concentrations indicate erosion rates. the 10be concentration of the bengal bay sediment depends on the contributions of the ganga and brahmaputra rivers. their sediments have distinct 10be concentrations because of distinct elevations and erosion in their drainage basins. variable contributions could thus complicate erosion-rate calculation. we traced these contributions by a provenance study using the strontium (sr) and neodymium (nd) isotopic sediment compositions. within uncertainties of ±30%, our reconstructed past erosion rates show no long-term increase for the past six million years. this stability suggests that climatic changes during the late cenozoic have an undetectable impact on the erosion patterns in the himalayas, at least on the ten thousand to million year timescales accounted for by our dataset. | steady erosion rates in the himalayas through late cenozoic climatic changes |
the galactic centre contains a supermassive black hole with a mass of four million suns1 within an environment that differs markedly from that of the galactic disk. although the black hole is essentially quiescent in the broader context of active galactic nuclei, x-ray observations have provided evidence for energetic outbursts from its surroundings2. also, although the levels of star formation in the galactic centre have been approximately constant over the past few hundred million years, there is evidence of increased short-duration bursts3, strongly influenced by the interaction of the black hole with the enhanced gas density present within the ring-like central molecular zone4 at galactic longitude |l| < 0.7 degrees and latitude |b| < 0.2 degrees. the inner 200-parsec region is characterized by large amounts of warm molecular gas5, a high cosmic-ray ionization rate6, unusual gas chemistry, enhanced synchrotron emission7,8, and a multitude of radio-emitting magnetized filaments9, the origin of which has not been established. here we report radio imaging that reveals a bipolar bubble structure, with an overall span of 1 degree by 3 degrees (140 parsecs × 430 parsecs), extending above and below the galactic plane and apparently associated with the galactic centre. the structure is edge-brightened and bounded, with symmetry implying creation by an energetic event in the galactic centre. we estimate the age of the bubbles to be a few million years, with a total energy of 7 × 1052 ergs. we postulate that the progenitor event was a major contributor to the increased cosmic-ray density in the galactic centre, and is in turn the principal source of the relativistic particles required to power the synchrotron emission of the radio filaments within and in the vicinity of the bubble cavities. | inflation of 430-parsec bipolar radio bubbles in the galactic centre by an energetic event |
we present high-resolution (0.''3) atacama large millimeter array 870 μm imaging of 52 sub-millimeter galaxies (smgs) in the ultra deep survey field to investigate the size and morphology of the sub-millimeter (sub-mm) emission on 2-10 kpc scales. we derive a median intrinsic angular size of fwhm = 0.''30 ± 0.''04 for the 23 smgs in the sample detected at a signal-to-noise ratio (s/n) >10. using the photometric redshifts of the smgs we show that this corresponds to a median physical half-light diameter of 2.4 ± 0.2 kpc. a stacking analysis of the smgs detected at s/n <10 shows they have sizes consistent with the 870 μm bright smgs in the sample. we compare our results to the sizes of smgs derived from other multi-wavelength studies, and show that the rest-frame ~250 μm sizes of smgs are consistent with studies of resolved 12co (j = 3-2 to 7-6) emission lines, but that sizes derived from 1.4 ghz imaging appear to be approximately two times larger on average, which we attribute to cosmic ray diffusion. the rest-frame optical sizes of smgs are around four times larger than the sub-millimeter sizes, indicating that the star formation in these galaxies is compact relative to the pre-existing stellar distribution. the size of the starburst region in smgs is consistent with the majority of the star formation occurring in a central region, a few kiloparsecs in extent, with a median star formation rate surface density of 90 ± 30 m ⊙ yr-1 kpc-2, which may suggest that we are witnessing an intense period of bulge growth in these galaxies. | the scuba-2 cosmology legacy survey: alma resolves the rest-frame far-infrared emission of sub-millimeter galaxies |
tunka-rex is a radio detector for cosmic-ray air showers in siberia, triggered by tunka-133, a co-located air-cherenkov detector. the main goal of tunka-rex is the cross-calibration of the two detectors by measuring the air-cherenkov light and the radio signal emitted by the same air showers. this way we can explore the precision of the radio-detection technique, especially for the reconstruction of the primary energy and the depth of the shower maximum. the latter is sensitive to the mass of the primary cosmic-ray particles. in this paper we describe the detector setup and explain how electronics and antennas have been calibrated. the analysis of data of the first season proves the detection of cosmic-ray air showers and therefore, the functionality of the detector. we confirm the expected dependence of the detection threshold on the geomagnetic angle and the correlation between the energy of the primary cosmic-ray particle and the radio amplitude. furthermore, we compare reconstructed amplitudes of radio pulses with predictions from coreas simulations, finding agreement within the uncertainties. | measurement of cosmic-ray air showers with the tunka radio extension (tunka-rex) |
for nearly a century, studying cosmic-ray air showers has driven progress in our understanding of elementary particle physics. in this work, we revisit the production of millicharged particles in these atmospheric showers and provide new constraints for xenon1t and super-kamiokande and new sensitivity estimates of current and future detectors, such as juno. we discuss distinct search strategies, specifically studies of single-energy-deposition events, where one electron in the detector receives a relatively large energy transfer, as well as multiple-scattering events consisting of (at least) two relatively small energy depositions. we demonstrate that these atmospheric search strategies — especially the multiple-scattering signature — provide significant room for improvement beyond existing searches, in a way that is complementary to anthropogenic, beam-based searches for mev-gev millicharged particles. finally, we also discuss the implementation of a monte carlo simulation for millicharged particle detection in large-volume neutrino detectors, such as icecube. | millicharged particles from the heavens: single- and multiple-scattering signatures |
high-energy neutrino astrophysics has come of age with icecube's discovery of neutrinos in the tev to pev energy range, attributable to extragalactic sources at cosmological distances. at such energies, astrophysical neutrinos must originate in cosmic-ray interactions, providing information about the sources of high-energy cosmic rays, as well as leading to the coproduction of high-energy γ-rays. the intimate link with these two independently observed types of radiation provides important tools for the quest to identify and understand the nature of the astrophysical sources of the neutrinos. these neutrinos can set important constraints on the cosmic-ray acceleration process, and because they travel essentially unimpeded, they can probe our universe out to the farthest cosmological distances. | astrophysical sources of high-energy neutrinos in the icecube era |
light sub-gev halo dark matter (dm) particles up-scattered by high-energy cosmic-rays (crs) (referred to as crdm) can be energetic and become detectable by conventional dm direct detection experiments. we perform a refined analysis on the exclusion bounds of the spin-independent dm-nucleon scattering cross section σχ p in this approach. for the exclusion lower bounds, we determine the parameter of the effective distance deff for crdm production using spatial-dependent cr fluxes and including the contributions from the major heavy cr nuclear species. we obtain deff≃ 9 kpc for crdm particles with kinetic energy above ~ 1 gev, which pushes the corresponding exclusion lower bounds down to σχ p~ 4× 10-32 cm2 for dm particle mass at mev scale and below. for the exclusion upper bounds from earth attenuation, previous estimations neglecting the nuclear form factor leaded to typical exclusion upper bounds of σχ p~𝒪(10-28) cm2 from the xenon1t data. using both the analytic and numerical approaches, we show that for crdm particles, the presence of the nuclear form factor strongly suppresses the effect of earth attenuation. consequently, the cross section that can be excluded by the xenon1t data can be a few orders of magnitude higher, which closes the gap in the cross sections excluded by the xenon1t experiment and that by the astrophysical measurements such that for the cosmic microwave background (cmb), galactic gas cloud cooling, and structure formation, etc.. | production and attenuation of cosmic-ray boosted dark matter |
muons and neutrinos from cosmic ray interactions in the atmosphere originate from decays of mesons in air-showers. uc(sibyll)-2.3c aims to give a precise description of hadronic interactions in the relevant phase space for conventional and prompt leptons in light of new accelerator data, including that from the lhc. uc(sibyll) is designed primarily as an event generator for use in simulation of extensive air showers. because it has been tuned for forward physics as well as the central region, it can also be used to calculate inclusive fluxes. the purpose of this paper is to describe the use of uc(sibyll)-2.3c for calculation of fluxes of atmospheric leptons. | hadronic interaction model uc(sibyll) 2.3 c and inclusive lepton fluxes |
the recent observation of very high energy cosmic neutrinos by icecube heralds the beginning of neutrino astronomy. at these energies, the dominant background to the astrophysical signal is the flux of `prompt' neutrinos, arising from the decay of charmed mesons produced by cosmic ray collisions in the atmosphere. in this work we provide predictions for the prompt atmospheric neutrino flux in the framework of perturbative qcd, using state-of-the-art monte carlo event generators. our calculation includes the constraints set by charm production measurements from the lhcb experiment at 7 tev, recently validated with the corresponding 13 tev data. our result for the prompt flux is a factor of about 2 below the previous benchmark calculation, in general agreement with other recent estimates, but with an improved estimate of the uncertainty. this alleviates the existing tension between the theoretical prediction and icecube limits, and suggests that a direct detection of the prompt flux is imminent. | the prompt atmospheric neutrino flux in the light of lhcb |
in diffuse interstellar clouds the chemistry that leads to the formation of the oxygen-bearing ions oh+, h2o+, and h3o+ begins with the ionization of atomic hydrogen by cosmic rays, and continues through subsequent hydrogen abstraction reactions involving h2. given these reaction pathways, the observed abundances of these molecules are useful in constraining both the total cosmic-ray ionization rate of atomic hydrogen (ζh) and molecular hydrogen fraction (f_h_2). we present observations targeting transitions of oh+, h2o+, and h3o+ made with the herschel space observatory along 20 galactic sight lines toward bright submillimeter continuum sources. both oh+ and h2o+ are detected in absorption in multiple velocity components along every sight line, but h3o+ is only detected along 7 sight lines. from the molecular abundances we compute f_h_2 in multiple distinct components along each line of sight, and find a gaussian distribution with mean and standard deviation 0.042 ± 0.018. this confirms previous findings that oh+ and h2o+ primarily reside in gas with low h2 fractions. we also infer ζh throughout our sample, and find a lognormal distribution with mean log (ζh) = -15.75 (ζh = 1.78 × 10-16 s-1) and standard deviation 0.29 for gas within the galactic disk, but outside of the galactic center. this is in good agreement with the mean and distribution of cosmic-ray ionization rates previously inferred from h_3^+ observations. ionization rates in the galactic center tend to be 10-100 times larger than found in the galactic disk, also in accord with prior studies. herschel is an esa space observatory with science instruments provided by european-led principal investigator consortia and with important participation from nasa. | herschel survey of galactic oh+, h2o+, and h3o+: probing the molecular hydrogen fraction and cosmic-ray ionization rate |
context. in addition to its relevant astrophysical and cosmological significance, the extragalactic background light (ebl) is a fundamental source of opacity for cosmic high energy photons, as well as a limitation for the propagation of high-energy particles in the universe.aims: we review our previously published determinations of the ebl photon density in the universe and its evolution with cosmic time, in the light of recent surveys of ir sources at long wavelengths.methods: we exploit deep survey observations by the herschel space observatory and the spitzer telescope, matched to optical and near-ir photometric and spectroscopic data, to re-estimate number counts and luminosity functions longwards of a few microns, and the contribution of resolved sources to the ebl.results: these new data indicate slightly lower photon densities in the mid- and far-infrared and sub-millimeter compared to previous determinations. this implies slightly lower cosmic opacity for photon-photon interactions.conclusions: the new data do not modify previously published ebl modeling in the uv-optical and near-ir up to several microns, while reducing the photon density at longer wavelengths. this improved model of the ebl alleviates some tension that had emerged in the interpretation of the highest-energy tev observations of local blazars, reducing the case for new physics beyond the standard model (like violations of the lorenz invariance, liv, at the highest particle energies), or for exotic astrophysics, that had sometimes been called for to explain it. applications of this improved ebl model on current data are considered, as well as perspectives for future instrumentation, the cherenkov telescope array (cta) in particular. | the extragalactic background light revisited and the cosmic photon-photon opacity |
we study the composition of the faint radio population selected from the karl g. jansky very large array cosmic evolution survey (vla-cosmos) 3 ghz large project, which is a radio continuum survey performed at 10 cm wavelength. the survey covers a 2.6 square degree area with a mean rms of 2.3 μjy/beam, cataloging 10 830 sources above 5σ, and enclosing the full 2 square degree cosmos field. by combining these radio data with optical, near-infrared (ultravista), and mid-infrared (spitzer/irac) data, as well as x-ray data (chandra), we find counterparts to radio sources for 93% of the total radio sample reaching out to z ≲ 6; these sources are found in the unmasked areas of the cosmos field, i.e., those not affected by saturated or bright sources in the optical to near-infrared (nir) bands. we further classify the sources as star-forming galaxies or agn based on various criteria, such as x-ray luminosity; observed mid-infrared color; uv-far-infrared spectral energy distribution; rest-frame, near-uv optical color that is corrected for dust extinction; and radio excess relative to that expected from the star formation rate of the hosts. we separate the agn into subsamples dominated by low-to-moderate and moderate-to-high radiative luminosity agn, i.e., candidates for high-redshift analogs to local low- and high-excitation emission line agn, respectively. we study the fractional contributions of these subpopulations down to radio flux levels of 11 μjy at 3 ghz (or 20 μjy at 1.4 ghz assuming a spectral index of -0.7). we find that the dominant fraction at 1.4 ghz flux densities above 200 μjy is constituted of low-to-moderate radiative luminosity agn. below densities of 100 μjy the fraction of star-forming galaxies increases to 60%, followed by the moderate-to-high radiative luminosity agn ( 20%) and low-to-moderate radiative luminosity agn ( 20%). based on this observational evidence, we extrapolate the fractions down to sensitivities of the square kilometer array (ska). our estimates suggest that at the faint flux limits to be reached by the (wide, deep, and ultradeep) ska1 surveys, a selection based only on radio flux limits can provide a simple tool to efficiently identify samples highly (>75%) dominated by star-forming galaxies. the catalog is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/602/a2 | the vla-cosmos 3 ghz large project: multiwavelength counterparts and the composition of the faint radio population |
we measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 mhz. exploiting the accurate energy scale of the pierre auger observatory, we obtain a radiation energy of 15.8 ±0.7 (stat)±6.7 (syst) mev for cosmic rays with an energy of 1 eev arriving perpendicularly to a geomagnetic field of 0.24 g, scaling quadratically with the cosmic-ray energy. a comparison with predictions from state-of-the-art first-principles calculations shows agreement with our measurement. the radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the pierre auger observatory. | measurement of the radiation energy in the radio signal of extensive air showers as a universal estimator of cosmic-ray energy |
magnetic reconnection is invoked as one of the primary mechanisms to produce energetic particles. we employ large-scale 3d particle-in-cell simulations of reconnection in magnetically dominated (σ = 10) pair plasmas to study the energization physics of high-energy particles. we identify an acceleration mechanism that only operates in 3d. for weak guide fields, 3d plasmoids/flux ropes extend along the z-direction of the electric current for a length comparable to their cross-sectional radius. unlike in 2d simulations, where particles are buried in plasmoids, in 3d we find that a fraction of particles with γ ≳ 3σ can escape from plasmoids by moving along z, and so they can experience the large-scale fields in the upstream region. these "free" particles preferentially move in z along speiser-like orbits sampling both sides of the layer and are accelerated linearly in time-their lorentz factor scales as γ ∝ t, in contrast to $\gamma \propto \sqrt{t}$ in 2d. the energy gain rate approaches ~ee rec c, where e rec ≃ 0.1b 0 is the reconnection electric field and b 0 the upstream magnetic field. the spectrum of free particles is hard, ${{dn}}_{\mathrm{free}}/d\gamma \propto {\gamma }^{-1.5}$ , contains ~20% of the dissipated magnetic energy independently of domain size, and extends up to a cutoff energy scaling linearly with box size. our results demonstrate that relativistic reconnection in grb and agn jets may be a promising mechanism for generating ultra-high-energy cosmic rays. | fast particle acceleration in three-dimensional relativistic reconnection |
an important factor limiting our ability to understand the production and propagation of cosmic rays pertains to the effects of heliospheric forces, commonly known as solar modulation. the solar wind is capable of generating time- and charge-dependent effects on the spectrum and intensity of low-energy (≲10 gev ) cosmic rays reaching earth. previous analytic treatments of solar modulation have utilized the force-field approximation, in which a simple potential is adopted whose amplitude is selected to best fit the cosmic-ray data taken over a given period of time. making use of recently available cosmic-ray data from the voyager 1 spacecraft, along with measurements of the heliospheric magnetic field and solar wind, we construct a time-, charge- and rigidity-dependent model of solar modulation that can be directly compared to data from a variety of cosmic-ray experiments. we provide a simple analytic formula that can be easily utilized in a variety of applications, allowing us to better predict the effects of solar modulation and reduce the number of free parameters involved in cosmic-ray propagation models. | a predictive analytic model for the solar modulation of cosmic rays |
context. radio relics in galaxy clusters are giant diffuse synchrotron sources powered in cluster outskirts by merger shocks. although the relic-shock connection has been consolidated in recent years by a number of observations, the details of the mechanisms leading to the formation of relativistic particles in this environment are still not well understood.aims: the diffusive shock acceleration (dsa) theory is a commonly adopted scenario to explain the origin of cosmic rays at astrophysical shocks, including those in radio relics in galaxy clusters. however, in a few specific cases it has been shown that the energy dissipated by cluster shocks is not enough to reproduce the luminosity of the relics via dsa of thermal particles. studies based on samples of radio relics are required to further address this limitation of the mechanism.methods: in this paper, we focus on ten well-studied radio relics with underlying shocks observed in the x-rays and calculate the electron acceleration efficiency of these shocks that is necessary to reproduce the observed radio luminosity of the relics.results: we find that in general the standard dsa cannot explain the origin of the relics if electrons are accelerated from the thermal pool with an efficiency significantly smaller than 10%. our results show that other mechanisms, such as shock re-acceleration of supra-thermal seed electrons or a modification of standard dsa, are required to explain the formation of radio relics. | shock acceleration efficiency in radio relics |
context. galactic cosmic rays (crs) are a ubiquitous source of ionisation of the interstellar gas, competing with uv and x-ray photons as well as natural radioactivity in determining the fractional abundance of electrons, ions, and charged dust grains in molecular clouds and circumstellar discs.aims: we model the propagation of various components of galactic crs versus the column density of the gas. our study is focussed on the propagation at high densities, above a few g cm-2, especially relevant for the inner regions of collapsing clouds and circumstellar discs.methods: the propagation of primary and secondary cr particles (protons and heavier nuclei, electrons, positrons, and photons) is computed in the continuous slowing down approximation, diffusion approximation, or catastrophic approximation by adopting a matching procedure for the various transport regimes. a choice of the proper regime depends on the nature of the dominant loss process modelled as continuous or catastrophic.results: the cr ionisation rate is determined by cr protons and their secondary electrons below ≈130 g cm-2 and by electron-positron pairs created by photon decay above ≈600 g cm-2. we show that a proper description of the particle transport is essential to compute the ionisation rate in the latter case, since the electron and positron differential fluxes depend sensitively on the fluxes of both protons and photons.conclusions: our results show that the cr ionisation rate in high-density environments, such as the inner parts of collapsing molecular clouds or the mid-plane of circumstellar discs, is higher than previously assumed. it does not decline exponentially with increasing column density, but follows a more complex behaviour because of the interplay of the different processes governing the generation and propagation of secondary particles. | cosmic-ray ionisation in circumstellar discs |
extp is a science mission designed to study the state of matter under extreme conditions of density, gravity and magnetism. primary goals are the determination of the equation of state of matter at supra-nuclear density, the measurement of qed effects in highly magnetized star, and the study of accretion in the strong-field regime of gravity. primary targets include isolated and binary neutron stars, strong magnetic field systems like magnetars, and stellar-mass and supermassive black holes. the mission carries a unique and unprecedented suite of state-of-the-art scientific instruments enabling for the first time ever the simultaneous spectral-timing-polarimetry studies of cosmic sources in the energy range from 0.5-30 kev (and beyond). key elements of the payload are: the spectroscopic focusing array (sfa) - a set of 11 x-ray optics for a total effective area of ∼0.9 m2 and 0.6 m2 at 2 kev and 6 kev respectively, equipped with silicon drift detectors offering <180 ev spectral resolution; the large area detector (lad) - a deployable set of 640 silicon drift detectors, for a total effective area of ∼3.4 m2, between 6 and 10 kev, and spectral resolution better than 250 ev; the polarimetry focusing array (pfa) - a set of 2 x-ray telescope, for a total effective area of 250 cm2 at 2 kev, equipped with imaging gas pixel photoelectric polarimeters; the wide field monitor (wfm) - a set of 3 coded mask wide field units, equipped with position-sensitive silicon drift detectors, each covering a 90 degrees x 90 degrees field of view. the extp international consortium includes major institutions of the chinese academy of sciences and universities in china, as well as major institutions in several european countries and the united states. the predecessor of extp, the xtp mission concept, has been selected and funded as one of the so-called background missions in the strategic priority space science program of the chinese academy of sciences since 2011. the strong european participation has significantly enhanced the scientific capabilities of extp. the planned launch date of the mission is earlier than 2025. | extp: enhanced x-ray timing and polarization mission |
the development and operation of liquid-argon time-projection chambers for neutrino physics has created a need for new approaches to pattern recognition in order to fully exploit the imaging capabilities offered by this technology. whereas the human brain can excel at identifying features in the recorded events, it is a significant challenge to develop an automated, algorithmic solution. the pandora software development kit provides functionality to aid the design and implementation of pattern-recognition algorithms. it promotes the use of a multi-algorithm approach to pattern recognition, in which individual algorithms each address a specific task in a particular topology. many tens of algorithms then carefully build up a picture of the event and, together, provide a robust automated pattern-recognition solution. this paper describes details of the chain of over one hundred pandora algorithms and tools used to reconstruct cosmic-ray muon and neutrino events in the microboone detector. metrics that assess the current pattern-recognition performance are presented for simulated microboone events, using a selection of final-state event topologies. | the pandora multi-algorithm approach to automated pattern recognition of cosmic-ray muon and neutrino events in the microboone detector |
ligo's discovery of a gravitational wave from two merging black holes (bhs) of similar masses rekindled suggestions that primordial bhs (pbhs) make up the dark matter (dm). if so, pbhs would add a poissonian isocurvature density fluctuation component to the inflation-produced adiabatic density fluctuations. for ligo's bh parameters, this extra component would dominate the small-scale power responsible for collapse of early dm halos at z ≳ 10, where first luminous sources formed. we quantify the resultant increase in high-z abundances of collapsed halos that are suitable for producing the first generation of stars and luminous sources. the significantly increased abundance of the early halos would naturally explain the observed source-subtracted near-ir cosmic infrared background (cib) fluctuations, which cannot be accounted for by known galaxy populations. for ligo's bh parameters, this increase is such that the observed cib fluctuation levels at 2-5 μm can be produced if only a tiny fraction of baryons in the collapsed dm halos forms luminous sources. gas accretion onto these pbhs in collapsed halos, where first stars should also form, would straightforwardly account for the observed high coherence between the cib and unresolved cosmic x-ray background in soft x-rays. we discuss modifications possibly required in the processes of first star formation if ligo-type bhs indeed make up the bulk or all of dm. the arguments are valid only if the pbhs make up all, or at least most, of dm, but at the same time the mechanism appears inevitable if dm is made of pbhs. | ligo gravitational wave detection, primordial black holes, and the near-ir cosmic infrared background anisotropies |
the anita collaboration have reported observation of two anomalous events that appear to be $\varepsilon_{\rm cr} \approx 0.6$ eev cosmic ray showers emerging from the earth with exit angles of $27^\circ$ and $35^\circ$, respectively. while eev-scale upgoing showers have been anticipated as a result of astrophysical tau neutrinos converting to tau leptons during earth passage, the observed exit angles are much steeper than expected in standard model (sm) scenarios. indeed, under conservative extrapolations of the sm interactions, there is no particle that can propagate through the earth with probability $p > 10^{-6}$ at these energies and exit angles. we explore here whether "beyond the standard model" (bsm) particles are required to explain the anita events, if correctly interpreted, and conclude that they are. seeking confirmation or refutation of the physical phenomenon of sub-eev earth-emergent cosmic rays in data from other facilities, we find support for the reality of the anita events, and three candidate analog events, among the extremely high energy northern track neutrinos of the icecube neutrino observatory. properties of the implied bsm particle are anticipated, at least in part, by those predicted for the "stau" slepton ($\tilde{\tau}_r$) in some supersymmetric models of the fundamental interactions, wherein the stau manifests as the next-to-lowest mass supersymmetric partner particle. | the anita anomalous events as signatures of a beyond standard model particle, and supporting observations from icecube |
a diffuse flux of astrophysical neutrinos above 100 tev has been observed at the icecube neutrino observatory. here we extend this analysis to probe the astrophysical flux down to 35 tev and analyze its flavor composition by classifying events as showers or tracks. taking advantage of lower atmospheric backgrounds for showerlike events, we obtain a shower-biased sample containing 129 showers and 8 tracks collected in three years from 2010 to 2013. we demonstrate consistency with the (fe∶fμ∶fτ)⊕≈(1 ∶1 ∶1 )⊕ flavor ratio at earth commonly expected from the averaged oscillations of neutrinos produced by pion decay in distant astrophysical sources. limits are placed on nonstandard flavor compositions that cannot be produced by averaged neutrino oscillations but could arise in exotic physics scenarios. a maximally tracklike composition of (0 ∶1 ∶0 )⊕ is excluded at 3.3 σ , and a purely showerlike composition of (1 ∶0 ∶0 )⊕ is excluded at 2.3 σ . | flavor ratio of astrophysical neutrinos above 35 tev in icecube |
the unprecedented quality of the data collected by the ams-02 experiment onboard the international space station allowed us to address subtle questions concerning the origin and propagation of cosmic rays. here we discuss the implications of these data for the injection spectrum of elements with different masses and for the diffusion coefficient probed by cosmic rays through their journey from the sources to the earth. we find that the best fit to the spectra of primary and secondary nuclei requires (1) a break in the energy dependence of the diffusion coefficient at energies ∼300 gv ; (2) an injection spectrum that is the same for all nuclei heavier than helium, and different injections for both protons and helium. moreover, if to force the injection spectrum of helium to be the same as for heavier nuclei, the fit to oxygen substantially worsens. accounting for a small, xs∼0.4 g cm-2 , grammage accumulated inside the sources leads to a somewhat better fit to the b/c ratio but makes the difference between he and other elements even more evident. the statistic and systematic error bars claimed by the ams collaboration exceed the error that is expected from calculations once the uncertainties in the cross sections of production of secondary nuclei are taken into account. in order to make this point more quantitative, we present a novel parametrization of a large set of cross sections, relevant for cosmic ray physics, and we introduce the uncertainty in the branching ratios in a way that its effect can be easily grasped. | galactic cosmic rays after the ams-02 observations |
we present the first hybrid measurement of the average muon number in air showers at ultrahigh energies, initiated by cosmic rays with zenith angles between 62° and 80°. the measurement is based on 174 hybrid events recorded simultaneously with the surface detector array and the fluorescence detector of the pierre auger observatory. the muon number for each shower is derived by scaling a simulated reference profile of the lateral muon density distribution at the ground until it fits the data. a 1019 ev shower with a zenith angle of 67°, which arrives at the surface detector array at an altitude of 1450 m above sea level, contains on average (2.68 ±0.04 ±0.48 (sys))×107 muons with energies larger than 0.3 gev. the logarithmic gain d ln nμ/d ln e of muons with increasing energy between 4 ×1018 ev and 5 ×1019 ev is measured to be (1.029 ±0.024 ±0.030 (sys)) . | muons in air showers at the pierre auger observatory: mean number in highly inclined events |
dark matter (dm) charged under a dark u(1) force appears in many extensions of the standard model, and has been invoked to explain anomalies in cosmic-ray data, as well as a self-interacting dm candidate. in this paper, we perform a comprehensive phenomenological analysis of such a model, assuming that the dm abundance arises from the thermal freeze-out of the dark interactions. we include, for the first time, bound-state effects both in the dm production and in the indirect detection signals, and quantify their importance for fermi, ams-02, and cmb experiments. we find that dm in the mass range 1 gev to 100 tev, annihilating into dark photons of mev to gev mass, is in conflict with observations. instead, dm annihilation into heavier dark photons is viable. we point out that the late decays of multi-gev dark photons can produce significant entropy and thus dilute the dm density. this can lower considerably the dark coupling needed to obtain the dm abundance, and in turn relax the existing constraints. | dark matter's secret liaisons: phenomenology of a dark u(1) sector with bound states |
these lectures, presented at tasi 2016: anticipating the next discoveries in particle physics, provide an introduction to some key methods and tools of indirect dark matter searches. topics covered include estimation of dark matter signals, thermal freezeout and related scenarios, potential effects of dark matter annihilation on the early universe, modeling photon signals from annihilation or decay, and a brief and qualitative introduction to diffusive propagation of cosmic rays. the second half of the notes gives a status report (circa summer 2016) on selected experimental searches, the resulting constraints and some potential signal candidates. these notes are intended as an introduction to indirect dark matter searches for graduate students, focusing on back-of-the-envelope estimates and useful concepts rather than detailed quantitative computations. | tasi lectures on indirect detection of dark matter |
we present data and initial results from vlt/x-shooter emission-line spectroscopy of 96 galaxies selected by long γ-ray bursts (grbs) at 0.1 <z< 3.6, the largest sample of grb host spectra available to date. most of our grbs were detected by swift and 76% are at 0.5 <z< 2.5 with a median zmed ~ 1.6. based on balmer and/or forbidden lines of oxygen, nitrogen, and neon, we measure systemic redshifts, star formation rates (sfr), visual attenuations (av), oxygen abundances (12 + log (o/h)), and emission-line widths (σ). we study grb hosts up to z ~ 3.5 and find a strong change in their typical physical properties with redshift. the median sfr of our grb hosts increases from sfrmed ~ 0.6 m⊙ yr-1 at z ~ 0.6 up to sfrmed ~ 15 m⊙ yr-1 at z ~ 2. a higher ratio of [o iii]/[o ii] at higher redshifts leads to an increasing distance of grb-selected galaxies to the locus of local galaxies in the baldwin-phillips-terlevich diagram. there is weak evidence for a redshift evolution in av and σ, with the highest values seen at z ~ 1.5 (av) or z ~ 2 (σ). oxygen abundances of the galaxies are distributed between 12 + log (o/h) = 7.9 and 12 + log (o/h) = 9.0 with a median 12 + log (o/h)med ~ 8.5. the fraction of grb-selected galaxies with super-solar metallicities is ~20% at z< 1 in the adopted metallicity scale. this is significantly less than the fraction of total star formation in similar galaxies, illustrating that grbs are scarce in high metallicity environments. at z ~ 3, sensitivity limits us to probing only the most luminous grb hosts for which we derive metallicities of z ≲ 0.5 z⊙. together with a high incidence of z ~ 0.5 z⊙ galaxies at z ~ 1.5, this indicates that a metallicity dependence at low redshift will not be dominant at z ~ 3. significant correlations exist between the hosts' physical properties. oxygen abundance, for example, relates to av (12 + log (o/h) ∝ 0.17·av), line width (12 + log (o/h) ∝ σ0.6), and sfr (12 + log (o/h) ∝ sfr0.2). in the last two cases, the normalization of the relations shift to lower metallicities at z> 2 by ~0.4 dex. these properties of grb hosts and their evolution with redshift can be understood in a cosmological context of star-forming galaxies and a picture in which the hosts' properties at low redshift are influenced by the tendency of grbs to avoid the most metal-rich environments. based on observations at eso, program ids: 084.a-0260, 084.a-0303, 085.a-0009, 086.b-0954, 086.a-0533, 086.a-0874, 087.a-0055, 087.a-0451, 087.b-0737, 088.a-0051, 088.a-0644, 089.a-0067, 089.a-0120, 089.d-0256, 089.a-0868, 090.a-0088, 090.a-0760, 090.a-0825, 091.a-0342, 091.a-0703, 091.a-0877, 091.c-0934, 092.a-0076, 092.a-0124, 092.a-0231, 093.a-0069, 094.a-0593.tables 1-4 and appendices are available in electronic form at http://www.aanda.orgthe reduced spectra are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/581/a125 | grb hosts through cosmic time. vlt/x-shooter emission-line spectroscopy of 96 γ-ray-burst-selected galaxies at 0.1 <z < 3.6 |
the high-altitude water cherenkov (hawc) observatory is a second-generation continuously operated, wide field-of-view, tev gamma-ray observatory. the hawc observatory and its analysis techniques build on experience of the milagro experiment in using ground-based water cherenkov detectors for gamma-ray astronomy. hawc is located on the sierra negra volcano in méxico at an elevation of 4100 meters above sea level. the completed hawc observatory principal detector (hawc) consists of 300 closely spaced water cherenkov detectors, each equipped with four photomultiplier tubes to provide timing and charge information to reconstruct the extensive air shower energy and arrival direction. the hawc observatory has been optimized to observe transient and steady emission from sources of gamma rays within an energy range from several hundred gev to several hundred tev. however, most of the air showers detected are initiated by cosmic rays, allowing studies of cosmic rays also to be performed. this paper describes the characteristics of the hawc main array and its hardware. | the high-altitude water cherenkov (hawc) observatory in méxico: the primary detector |
we propose that the symbol alphabet for classes of planar, dual-conformal-invariant feynman integrals can be obtained as truncated cluster algebras purely from their kinematics, which correspond to boundaries of (compactifications of) g+(4, n)/t for the n-particle massless kinematics. for one-, two-, three-mass-easy hexagon kinematics with n = 7, 8, 9, we find finite cluster algebras d4, d5 and d6 respectively, in accordance with previous result on alphabets of these integrals. as the main example, we consider hexagon kinematics with two massive corners on opposite sides and find a truncated affine d4 cluster algebra whose polytopal realization is a co-dimension 4 boundary of that of g+(4, 8)/t with 39 facets; the normal vectors for 38 of them correspond to g-vectors and the remaining one gives a limit ray, which yields an alphabet of 38 rational letters and 5 algebraic ones with the unique four-mass-box square root. we construct the space of integrable symbols with this alphabet and physical first-entry conditions, whose dimension can be reduced using conditions from a truncated version of cluster adjacency. already at weight 4, by imposing last-entry conditions inspired by the n = 8 double-pentagon integral, we are able to uniquely determine an integrable symbol that gives the algebraic part of the most generic double-pentagon integral. finally, we locate in the space the n = 8 double-pentagon ladder integrals up to four loops using differential equations derived from wilson-loop d log forms, and we find a remarkable pattern about the appearance of algebraic letters. | truncated cluster algebras and feynman integrals with algebraic letters |
the association of two icecube detections, the icecube-170922a event and a neutrino flare, with the blazar txs 0506+056, has paved the way for the multimessenger quest for cosmic accelerators. icecube has observed many other neutrinos but their origin remains unknown. to better understand the reason for the apparent lack of neutrino counterparts, we have extended the comprehensive dissection of the sky area performed for the icecube-170922a event to all 70 public icecube high-energy neutrinos that are well reconstructed and off the galactic plane. using the multifrequency data available through the open universe platform, we have identified numerous candidate counterparts of icecube events. we report here the classification of all the γ-ray blazars found and the results of subsequent statistical tests. in addition, we have checked the 4lac, 3fhl, and 3hsp catalogues for potential counterparts. following the dissection of all areas associated with icecube neutrinos, we evaluate the data using a likelihood-ratio test and find a $3.23\, \sigma$ (post-trial) excess of hbls and ibls with a best fit of 15 ± 3.6 signal sources. this result, together with previous findings, consistently points to a growing evidence for a connection between icecube neutrinos and blazars, the most energetic particle accelerators known in the universe. | dissecting the regions around icecube high-energy neutrinos: growing evidence for the blazar connection |
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