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estimating the extent and age of the last glacial maxima as well as the chronology of glacial recessions in various environmental contexts is key to source‑to‑sink studies and paleoclimate reconstructions. the argentera‑mercantour massif is located at the transition between the alps and the mediterranean sea, therefore, its deglaciation chronology can be compared to the sediment budget of the var river basin. based on 13 new cosmic‑ray exposure (cre) beryllium‑10 (10be) datings performed on moraines and polished crystalline bedrocks and 22 reassessed 10be cre ages from similar altitude nearby steep basement surfaces, and from a lake sediment core, we can constrain the deglaciation chronology of the argentera‑mercantour massif. these data allow for the first time to fully reconstruct the deglaciation history at the scale of the entire massif in agreement with a major glacier recession at c. 15 ka, at the onset of bølling transition between the oldest and older dryas. main deglaciation of the upper slopes [2700–2800 m above sea level (a.s.l.)] occurred after the last glacial maximum (lgm) at 20.8–18.6 ka, followed by the main deglaciation of the lower slopes (2300 m a.s.l.) at 15.3–14.2 ka. finally, the flat polished surfaces above 2600 m a.s.l. and the zones confined within narrow lateral valleys were likely affected by progressive ice melting of remaining debris covered glaciers and moraine erosion following the younger dryas re‑advance stage between 12 and 8–9 ka. at lower elevations, the vens lake located at 2300 m a.s.l., allows evidence of the onset of lake sedimentation at c. 14 ka and a transition towards a vegetated environment that mainly occurred before 8 ka. moraine final stabilization at 5 ka might reflect denudation acceleration during the holocene humid phase. this contribution reveals a glacier–climate relationship more sensitive to warming phases in the southern alps highlighted by a major decrease of glaciers after c. 15 ka. this major deglaciation is correlated with a 2.5‑fold decrease of sediment discharge of rivers into the mediterranean sea. | deglaciation history at the alpine‑mediterranean transition (argentera‑mercantour, sw alps) from 10be dating of moraines and glacially polished bedrock |
the 28th of february 2017 marked the 75th anniversary of the first confident detection of solar cosmic rays (scrs), a term referring to accelerated solar particles with energies from about 10^6 to ∼ 1010-1011 ev. the present paper reviews the key observational and theoretical results on scrs that have been accumulated over this period. the history of the discovery of scrs is briefly described, together with scr recording techniques and instruments, and some physical, methodical, and practical aspects of scr generation are discussed in more detail. special attention is given to mechanisms of charged particle acceleration at and near the sun. current ideas on the interaction of solar cosmic rays with the solar atmosphere, peculiarities of their transport in interplanetary magnetic fields, movements in earth's magnetosphere, and their impact on earth's atmosphere are reviewed. it is shown that this field of space physics has produced many results of fundamental interest for astrophysics, solar-terrestrial physics, geophysics, and practical cosmonautics (astronautics). | solar cosmic rays: 75 years of research |
the central pyrenees hosted a large ice cap during the late pleistocene. the cirques under relatively low-altitude peaks (2200-2800 m) include the greatest variety of glacial landforms (moraines, fossil debris-covered glaciers and rock glaciers), but their age and formation process are poorly known. here, we focus on the headwaters of the garonne river, namely on the low-altitude bacivèr cirque (highest peaks at ~2600 m), with widespread erosive and depositional glacial and periglacial landforms. we reconstruct the pattern of deglaciation from geomorphological observations and a 17-sample dataset of 10be cosmic-ray exposure (cre) ages. ice thickness in the bacivèr cirque must have reached ~200 m during the maximum ice extent of the last glacial cycle, when it flowed down towards the garonne paleoglacier. however, by ~15 ka, during the bølling-allerød (b-a) interstadial, the mouth of the cirque was deglaciated as the tributary glacier shrank and disconnected from the garonne paleoglacier. glacial retreat was rapid, and the whole cirque was likely to have been deglaciated in only a few centuries, while paraglacial processes accelerated, leading to the transformation of debris-free glaciers into debris-covered and rock glaciers in their final stages. climate conditions prevailing at the transition between the b-a and the younger dryas (yd) favored glacial growth and the likely development of small moraines within the slopes of the cirque walls by ~12.9 ka, but the dating uncertainties make it impossible to state whether these moraines formed during the b-a or the yd. the melting of these glaciers favored paraglacial dynamics, which promoted the development of rock glaciers as well as debris-covered glaciers. these remained active throughout the early holocene until at least ~7 ka. since then, the landscape of the bacivèr cirque has seen a period of relative stability. a similar chronological sequence of deglaciation has been also detected in other cirques of the pyrenees below 3000 m. as in other mid-latitude mountain regions, the b-a triggered the complete deglaciation of the garonne paleoglacier and promoted the development of the wide variety of glacial and periglacial landforms existing in the bacivèr cirque. | rapid deglaciation during the bølling-allerød interstadial in the central pyrenees and associated glacial and periglacial landforms |
on 10 september 2017, a ground level enhancement (gle) of cosmic ray intensity, identified as gle72, was recorded by several stations of the worldwide neutron monitor network provided by the high-resolution neutron monitor database. the solar proton event that resulted in this gle was associated with active region ar2673, which produced an x8.2 flare on the solar west limb. protons were measured by the goes satellites with energies above 10, 50, and 100 mev, while particles at higher energies above 500 mev were registered by ground-based neutron monitors. this gle event was successfully detected in real time by the gle alert plus system of the athens neutron monitor station (a.ne.mo.s.). in this work an overview of the gle72 event is given, and a detailed analysis of the evolution of the gle alert signal issued by the gle alert plus system as well as a postevent summary are presented. | real-time detection of the ground level enhancement on 10 september 2017 by a.ne.mo.s.: system report |
we investigate acceleration and propagation processes of high-energy particles inside hot accretion flows. the magnetorotational instability (mri) creates turbulence inside accretion flows, which triggers magnetic reconnection and may produce non-thermal particles. they can be further accelerated stochastically by the turbulence. to probe the properties of such relativistic particles, we perform magnetohydrodynamic simulations to obtain the turbulent fields generated by the mri, and calculate orbits of the high-energy particles using snapshot data of the mri turbulence. we find that the particle acceleration is described by a diffusion phenomenon in energy space with a diffusion coefficient of the hard-sphere type: dɛ ∝ ɛ2, where ɛ is the particle energy. eddies in the largest scale of the turbulence play a dominant role in the acceleration process. on the other hand, the stochastic behaviour in configuration space is not usual diffusion but superdiffusion: the radial displacement increases with time faster than that in the normal diffusion. also, the magnetic field configuration in the hot accretion flow creates outward bulk motion of high-energy particles. this bulk motion is more effective than the diffusive motion for higher energy particles. our results imply that typical active galactic nuclei that host hot accretion flows can accelerate crs up to ɛ ∼ 0.1-10 pev. | acceleration and escape processes of high-energy particles in turbulence inside hot accretion flows |
a high-fidelity record covering nearly 40 years of water-dissolved radon from the hot spring site of banglazhang (blz), southwestern china is presented to study multi-year periodicities of radon. ancillary observational data, i.e., water temperature, spring discharge rate, barometric pressure, combined with regional rainfall, galactic cosmic rays (gcr flux is modulated by solar wind and thus a proxy for solar activity) and regional seismicity from the same period are considered to identify potentially influencing factors controlling the changes in radon. variations in radon concentration and ancillary observational data are studied using continuous wavelet power spectrum (wps), wavelet coherence (wtc), and partial wavelet coherence (pwc). the results show that the long-period radon concentration is characterized by a quasi-decadal (8-11 years) cycle, matching well with the concurrent periodicity in water temperature, spring discharge rates and gcr. pwcs of radon, discharge rate and water temperature suggest that water temperature variations explain most of the coherent variability of radon and the discharge rate. we tentatively conclude that radon variations are mainly explained by variations in water temperature and spring discharge, which are modified and modulated by earthquakes and quasi-decadal variations of an unidentified process. the influence of solar activity on the decadal periodicity is discussed. | decadal radon cycles in a hot spring |
growing evidence reveals universal hardening on various cosmic ray spectra, e.g., proton, positron, as well as antiproton fractions. such universality may indicate they have a common origin. in this paper, we argue that these widespread excesses can be accounted for by a nearby supernova remnant surrounded by a giant molecular cloud. secondary cosmic rays (p , e+ ) are produced through the collisions between the primary cosmic-ray nuclei from this supernova remnant and the molecular gas. different from the background, which is produced by the ensemble of a large number of sources in the milky way, the local injected spectrum can be harder. the time-dependent transport of particles would make the propagated spectrum even harder. under this scenario, the anomalies of both primary (p , e-) and secondary (e+, p ¯ /p ) cosmic rays can be properly interpreted. we further show that the tev to sub-pev anisotropy of the proton is consistent with the observations if the local source is relatively young and lying at the anti-galactic center direction. | excesses of cosmic ray spectra from a single nearby source |
the azimuthal asymmetry in the risetime of signals in auger surface detector stations is a source of information on shower development. the azimuthal asymmetry is due to a combination of the longitudinal evolution of the shower and geometrical effects related to the angles of incidence of the particles into the detectors. the magnitude of the effect depends upon the zenith angle and state of development of the shower and thus provides a novel observable, (sec θ )max , sensitive to the mass composition of cosmic rays above 3 ×1018 ev . by comparing measurements with predictions from shower simulations, we find for both of our adopted models of hadronic physics (qgsjetii-04 and epos-lhc) an indication that the mean cosmic-ray mass increases slowly with energy, as has been inferred from other studies. however, the mass estimates are dependent on the shower model and on the range of distance from the shower core selected. thus the method has uncovered further deficiencies in our understanding of shower modeling that must be resolved before the mass composition can be inferred from (sec θ )max. | azimuthal asymmetry in the risetime of the surface detector signals of the pierre auger observatory |
a general theoretical framework is presented that allows for the addition of cosmic ray-driven radiation chemistry to astrochemical models. | a general method for the inclusion of radiation chemistry in astrochemical models |
we have studied long-term variations of galactic cosmic-ray (gcr) intensity in relation to the sunspot number (ssn) during the most recent solar cycles. this study analyses the time lag between the gcr intensity and ssn, and hysteresis plots of the gcr count rate against ssn for solar cycles 20 - 23, to validate a methodology against previous results in the literature, before applying the method to provide a timely update on the behaviour of cycle 24. plots of ssn versus gcr show a clear difference between the odd- and even-numbered cycles. linear and elliptical models have been fit to the data, with the linear fit and elliptical model proving the more suitable model for even- and odd-numbered solar-activity cycles, respectively, in agreement with previous literature. through the application of these methods for solar cycle 24, it has been shown that cycle 24 experienced a lag of two to four months between the gcr intensity and ssn, and this follows the trend of the preceding activity cycles, albeit with a slightly longer lag than previous even-numbered cycles. it has been shown through the hysteresis analysis that the linear fit is a better representative model for cycle 24, as the ellipse model does not show a significant improvement, which is also in agreement with previous even-numbered cycles. | the behaviour of galactic cosmic-ray intensity during solar activity cycle 24 |
x-ray and mid-infrared emission are signposts of the accretion of matter onto the supermassive black holes that reside at the centres of most galaxies. as a major step towards understanding accreting supermassive black holes and their role in the evolution of galaxies, we will use the 4most multi-object spectrograph to provide a highly complete census of active galactic nuclei over a large fraction of the extragalactic sky observed in x-rays by erosita that is visible to 4most. we will systematically follow up all erosita point-like extragalactic x-ray sources (mostly active galactic nuclei), and complement them with a heavily obscured active galactic nuclei selection approach using mid-infrared data from the wide-field infrared survey explorer (wise). the x-ray and mid-infrared flux limits of erosita and wise are well matched to the spectroscopic capabilities of a 4-metre-class telescope, allowing us to reach completeness levels of 80-90% for all x-ray selected active galactic nuclei with fluxes f0.5-2 kev > 10-14 erg s-1 cm-2; this is about a factor of 30 deeper than the rosat all-sky survey. with these data we will determine the physical properties (redshift, luminosity, line emission strength, masses, etc.) of up to one million supermassive black holes, constrain their cosmic evolution and clustering properties, and explore the connection between active galactic nuclei and large-scale structure over redshifts 0 ≲ z ≲ 6. | 4most consortium survey 6: active galactic nuclei |
context. the nearby ultra-luminous infrared galaxy (ulirg) arp 220 is an excellent laboratory for studies of extreme astrophysical environments. for 20 years, very long baseline interferometry (vlbi) has been used to monitor a population of compact sources thought to be supernovae (sne), supernova remnants (snrs), and possibly active galactic nuclei (agns). sne and snrs are thought to be the sites of relativistic particle acceleration powering star formation induced radio emission in galaxies, and are hence important for studies of for example the origin of the fir-radio correlation.aims: in this work we aim for a self-consistent analysis of a large collection of arp 220 continuum vlbi data sets. with more data and improved consistency in calibration and imaging, we aim to detect more sources and improve source classifications with respect to previous studies. furthermore, we aim to increase the number of sources with robust size estimates, to analyse the compact source luminosity function (lf), and to search for a luminosity-diameter (ld) relation within arp 220.methods: using new and archival vlbi data spanning 20 years, we obtained 23 high-resolution radio images of arp 220 at wavelengths from 18 cm to 2 cm. from model-fitting to the images we obtained estimates of flux densities and sizes of detected sources. the sources were classified in groups according to their observed lightcurves, spectra and sizes. we fitted a multi-frequency supernova light-curve model to the object brightest at 6 cm to estimate explosion properties for this object.results: we detect radio continuum emission from 97 compact sources and present flux densities and sizes for all analysed observation epochs. the positions of the sources trace the star forming disks of the two nuclei known from lower-resolution studies. we find evidence for a ld-relation within arp 220, with larger sources being less luminous. we find a compact source lf n(l)∝lβ with β = -2.19 ± 0.15, similar to snrs in normal galaxies, and we argue that there are many relatively large and weak sources below our detection threshold. the brightest (at 6 cm) object 0.2195+0.492 is modelled as a radio sn with an unusually long 6 cm rise time of 17 years.conclusions: the observations can be explained by a mixed population of sne and snrs, where the former expand in a dense circumstellar medium (csm) and the latter interact with the surrounding interstellar medium (ism). nine sources are likely luminous sne, for example type iin, and correspond to few percent of the total number of sne in arp 220. assuming all iins reach these luminosities, and no confusion with other sne types, our data are consistent with a total sn-rate of 4 yr-1 as inferred from the total radio emission given a normal stellar initial mass function (imf). based on the fitted luminosity function, we argue that emission from all compact sources, also below our detection threshold, make up at most 20% of the total radio emission at ghz frequencies. however, colliding sn shocks and the production of secondary electrons through cosmic ray (cr) protons colliding with the dense ism may cause weak sources to radiate much longer than assumed in this work. this could potentially explain the remaining fraction of the smooth synchrotron component. future, deeper observations of arp 220 will probe the sources with lower luminosities and larger sizes. this will further constrain the evolution of sne/snrs in extreme environments and the presence of agn activity. data, images, and analysis scripts presented in this paper (see appendix a) 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/623/a173 | the population of sne/snrs in the starburst galaxy arp 220. a self-consistent analysis of 20 years of vlbi monitoring |
most of the observed features of radio gischt relics, such as spectral steepening across the relic width and a power-law-like integrated spectrum, can be adequately explained by a diffusive shock acceleration (dsa) model in which relativistic electrons are (re-)accelerated at shock waves induced in the intracluster medium. however, the steep spectral curvature in the integrated spectrum above ∼2 ghz detected in some radio relics, such as the sausage relic in cluster ciza j2242.8+5301, may not be interpreted by the simple radiative cooling of postshock electrons. in order to understand such steepening, we consider here a model in which a spherical shock sweeps through and then exits out of a finite-size cloud with fossil relativistic electrons. the ensuing integrated radio spectrum is expected to steepen much more than predicted for aging postshock electrons, since the re-acceleration stops after the cloud-crossing time. using dsa simulations that are intended to reproduce radio observations of the sausage relic, we show that both the integrated radio spectrum and the surface brightness profile can be fitted reasonably well, if a shock of speed {u}s ∼ 2.5-2.8 × {10}3 {km} {{{s}}}-1 and a sonic mach number {m}s ∼ 2.7-3.0 traverses a fossil cloud for ∼45 myr, and the postshock electrons cool further for another ∼10 myr. this attempt illustrates that steep curved spectra of some radio gischt relics could be modeled by adjusting the shape of the fossil electron spectrum and adopting the specific configuration of the fossil cloud. | re-acceleration model for radio relics with spectral curvature |
high-energy astrophysical neutrino fluxes are, for many applications, modeled as simple power laws as a function of energy. while this is reasonable in the case of neutrino production in hadronuclear pp sources, it typically does not capture the behavior in photohadronic pγ sources: in that case, the neutrino spectrum depends on the properties of the target photons the cosmic rays collide with and on possible magnetic-field effects on the secondary pions and muons. we show that the neutrino production from known photohadronic sources can be reproduced by a thermal (black-body) target-photon spectrum if one suitably adjusts the temperature, thanks to multi-pion production processes. this allows discussing neutrino production from most known pγ sources, such as gamma-ray bursts, active galactic nuclei and tidal disruption events, in terms of a few parameters. we apply this thermal model to study the sensitivity of different classes of neutrino telescopes to photohadronic sources: we classify the model parameter space according to which experiment is most suitable for detection of a specific source class and demonstrate that different experiment classes, such as dense arrays, conventional neutrino telescopes, or radio-detection experiments, cover different parts of the parameter space. since the model can also reproduce the flavor and neutrino-antineutrino composition, we study the impact on the track-to-shower ratio and the glashow resonance. | unified thermal model for photohadronic neutrino production in astrophysical sources |
we present an analysis of the intrinsic (unattenuated by the extragalactic background light, ebl) power-law spectral indices of 128 extragalactic sources detected up to z∼ 2 with the fermi-large area telescope (lat) at very high energies (vhes, e≥slant 50 gev). the median of the intrinsic index distribution is 2.20 (versus 2.54 for the observed distribution). we also analyze the observed spectral breaks (i.e., the difference between the vhe and high energy, he, 100 {mev}≤slant e≤slant 300 {{gev}}, spectral indices). the fermi-lat has now provided a large sample of sources detected both at vhe and he with comparable exposure that allows us to test models of extragalactic γ-ray photon propagation. we find that our data are compatible with simulations that include intrinsic blazar curvature and ebl attenuation. there is also no evidence of evolution with redshift of the physics that drives the photon emission in high-frequency synchrotron peak (hsp) blazars. this makes hsp blazars excellent probes of the ebl. | spectral analysis of fermi-lat blazars above 50 gev |
galaxy clusters are one of the prime sites to search for dark matter (dm) annihilation signals. depending on the substructure of the dm halo of a galaxy cluster and the cross sections for dm annihilation channels, these signals might be detectable by the latest generation of γ-ray telescopes. here we use three years of fermi-large area telescope data, which are the most suitable for searching for very extended emission in the vicinity of the nearby virgo galaxy cluster. our analysis reveals statistically significant extended emission which can be well characterized by a uniformly emitting disk profile with a radius of 3° that moreover is offset from the cluster center. we demonstrate that the significance of this extended emission strongly depends on the adopted interstellar emission model (iem) and is most likely an artifact of our incomplete description of the iem in this region. we also search for and find new point source candidates in the region. we then derive conservative upper limits on the velocity-averaged dm pair annihilation cross section from virgo. we take into account the potential γ-ray flux enhancement due to dm sub-halos and its complex morphology as a merging cluster. for dm annihilating into b\bar{b}, assuming a conservative sub-halo model setup, we find limits that are between 1 and 1.5 orders of magnitude above the expectation from the thermal cross section for mdm ≲ 100 gev. in a more optimistic scenario, we exclude < σ v> ∼ 3× {10}-26 {{cm}}3 {{{s}}}-1 for mdm ≲ 40 gev for the same channel. finally, we derive upper limits on the γ-ray-flux produced by hadronic cosmic-ray interactions in the inter cluster medium. we find that the volume-averaged cosmic-ray-to-thermal pressure ratio is less than ∼6%. | search for extended gamma-ray emission from the virgo galaxy cluster with fermi-lat |
the flux of very high-energy neutrinos produced in our galaxy by the interaction of accelerated cosmic rays with the interstellar medium is not yet determined. the characterization of this flux will shed light on galactic accelerator features, gas distribution morphology and galactic cosmic ray transport. the central galactic plane can be the site of an enhanced neutrino production, thus leading to anisotropies in the extraterrestrial neutrino signal as measured by the icecube collaboration. the antares neutrino telescope, located in the mediterranean sea, offers a favorable view of this part of the sky, thereby allowing for a contribution to the determination of this flux. the expected diffuse galactic neutrino emission can be obtained, linking a model of generation and propagation of cosmic rays with the morphology of the gas distribution in the milky way. in this paper, the so-called "gamma model" introduced recently to explain the high-energy gamma-ray diffuse galactic emission is assumed as reference. the neutrino flux predicted by the "gamma model" depends on the assumed primary cosmic ray spectrum cutoff. considering a radially dependent diffusion coefficient, this proposed scenario is able to account for the local cosmic ray measurements, as well as for the galactic gamma-ray observations. nine years of antares data are used in this work to search for a possible galactic contribution according to this scenario. all flavor neutrino interactions are considered. no excess of events is observed, and an upper limit is set on the neutrino flux of 1.1 (1.2) times the prediction of the "gamma model," assuming the primary cosmic ray spectrum cutoff at 5 (50) pev. this limit excludes the diffuse galactic neutrino emission as the major cause of the "spectral anomaly" between the two hemispheres measured by icecube. | new constraints on all flavor galactic diffuse neutrino emission with the antares telescope |
context. the study of nonthermal processes such as synchrotron emission, inverse compton scattering, bremsstrahlung, and pion production is crucial to understanding the properties of the galactic cosmic-ray population, to shed light on their origin and confinement mechanisms, and to assess the significance of exotic signals possibly associated to new physics.aims: we present a public code called hermes which is designed generate sky maps associated to a variety of multi-messenger and multi-wavelength radiative processes, spanning from the radio domain all the way up to high-energy gamma-ray and neutrino production.methods: we describe the physical processes under consideration, the code concept and structure, and the user interface, with particular focus on the python-based interactive mode. in particular, present the modular and flexible design that allows the user to easily extend the numerical package according to their needs.results: in order to demonstrate the capabilities of the code, we describe the details of a comprehensive set of sky maps and spectra associated to all physical processes included in the code. we comment in particular on the radio, gamma-ray, and neutrino maps, and mention the possibility of studying signals stemming from dark matter annihilation.conclusions: hermes can be successfully applied to constrain the properties of the galactic cosmic-ray population, improve our understanding of the diffuse galactic radio, gamma-ray, and neutrino emission, and search for signals associated to particle dark matter annihilation or decay. | simulating the galactic multi-messenger emissions with hermes |
the eas cherenkov light array tunka-133, with 3 km2 geometric area, is taking data since 2009.the array permits a detailed study of energy spectrum and mass composition of cosmic rays in the energy range from 6 · 1015 to 1018 ev. we describe the methods of time and amplitude calibration of the array and the methods of eas parameters reconstruction. we present the all-particle energy spectrum, based on 7 seasons of operation. | the primary cosmic-ray energy spectrum measured with the tunka-133 array |
enshrouded in several well-known controversies, dwarf galaxies have been extensively studied to learn about the underlying cosmology, notwithstanding that physical processes regulating their properties are poorly understood. to shed light on these processes, we introduce the pandora suite of 17 high-resolution (3.5 parsec half-cell side) dwarf galaxy formation cosmological simulations. commencing with magneto-thermo-turbulent star formation and mechanical supernova (sn) feedback, we gradually increase the complexity of physics incorporated, ultimately leading to our full-physics models combining magnetism, on-the-fly radiative transfer and the corresponding stellar photoheating, and sn-accelerated cosmic rays. we investigate multiple combinations of these processes, comparing them with observations to constrain what are the main mechanisms determining dwarf galaxy properties. we find hydrodynamical 'sn feedback-only' simulations struggle to produce realistic dwarf galaxies, leading either to overquenched or too centrally concentrated, dispersion-dominated systems when compared to observed field dwarfs. accounting for radiation with cosmic rays results in extended and rotationally supported systems. spatially 'distributed' feedback leads to realistic stellar and h i masses, galaxy sizes, and integrated kinematics. furthermore, resolved kinematic maps of our full-physics models predict kinematically distinct clumps and kinematic misalignments of stars, h i, and h ii after star formation events. episodic star formation combined with its associated feedback induces more core-like dark matter central profiles, which our 'sn feedback-only' models struggle to achieve. our results demonstrate the complexity of physical processes required to capture realistic dwarf galaxy properties, making tangible predictions for integral field unit surveys, radio synchrotron emission, and for galaxy and multiphase interstellar medium properties that jwst will probe. | the pandora project - i. the impact of radiation, magnetic fields, and cosmic rays on the baryonic and dark matter properties of dwarf galaxies |
in hidden sector models, dark matter does not directly couple to the particle content of the standard model, strongly suppressing rates at direct detection experiments, while still allowing for large signals from annihilation. in this paper, we conduct an extensive study of hidden sector dark matter, covering a wide range of dark matter spins, mediator spins, interaction diagrams, and annihilation final states, in each case determining whether the annihilations are s-wave (thus enabling efficient annihilation in the universe today). we then go on to consider a variety of portal interactions that allow the hidden sector annihilation products to decay into the standard model. we broadly classify constraints from relic density requirements and dwarf spheroidal galaxy observations. in the scenario that the hidden sector was in equilibrium with the standard model in the early universe, we place a lower bound on the portal coupling, as well as on the dark matter's elastic scattering cross section with nuclei. we apply our hidden sector results to the observed galactic center gamma-ray excess and the cosmic-ray antiproton excess. we find that both of these excesses can be simultaneously explained by a variety of hidden sector models, without any tension with constraints from observations of dwarf spheroidal galaxies. | a systematic study of hidden sector dark matter: application to the gamma-ray and antiproton excesses |
to search for a signature of an intracluster magnetic field, we compare measurements of faraday rotation of polarised extragalactic radio sources in the line of sight of galaxy clusters with those outside. to this end, we correlated a catalogue of 1383 rotation measures of extragalactic polarised radio sources with galaxy clusters from the classix survey (combining reflex ii and noras ii) detected by their x-ray emission in the rosat all-sky survey. the survey covers 8.25 ster of the sky at | bii | ≥ 20°. we compared the rotation measures in the line of sight of clusters within their projected radii of r500 with those outside and found a significant excess of the dispersion of the rotation measures in the cluster regions. since the observed rotation measure is the result of faraday rotation in several presumably uncorrelated magnetised cells of the intracluster medium, the observations correspond to quantities averaged over several magnetic field directions and strengths. therefore the interesting quantity is the dispersion or standard deviation of the rotation measure for an ensemble of clusters. in the analysis of the observations we found a standard deviation of the rotation measure inside r500 of about 120 (± 21) rad m-2. this compares to about 56 (± 8) rad m-2 outside. correcting for the effect of the galaxy with the mean rotation measure in a region of 10 deg radius in the outskirts of the clusters does not change the outcome quoted above. we show that the most x-ray luminous and thus most massive clusters contribute most to the observed excess rotation measure. modelling the electron density distribution in the intracluster medium with a self-similar model based on the rexcess survey, we found that the dispersion of the rotation measure increases with the column density, and we deduce a magnetic field value of about 2-6 (l/ 10 kpc)- 1/2μg assuming a constant magnetic field strength, where l is the size of the coherently magnetised intracluster medium cells. this magnetic field energy density amounts to a few percent of the average thermal energy density in clusters. on the other hand, when we allowed the magnetic field to vary such that the magnetic energy density is a constant fraction of the thermal energy density, we deduced a slightly lower value for this fraction of 3-10 (l/ 10 kpc)- 1/2 per mille. compared to the situation in the milky way, where the ratio of the magnetic to thermal energy density is about unity, this ratio is much lower in galaxy clusters. the reason for this is most probably the different generation mechanism for the magnetic field, which is mostly powered by supernovae in the galaxy and by turbulence from cluster mergers in galaxy clusters. the latter process sets a natural upper limit on the growth of the magnetic field. | the cosmic large-scale structure in x-rays (classix) cluster survey. i. probing galaxy cluster magnetic fields with line of sight rotation measures |
a simplified ab initio approach is followed to model cosmic-ray proton modulation, using a steady-state three-dimensional stochastic solver of the parker transport equation that simulates some effects of time dependence. standard diffusion coefficients based on quasilinear theory and nonlinear guiding center theory are employed. the spatial and temporal dependences of the various turbulence quantities required as inputs for the diffusion, as well as the turbulence-reduced drift coefficients, follow from parametric fits to results from a turbulence transport model as well as from spacecraft observations of these turbulence quantities. effective values are used for the solar wind speed, magnetic field magnitude, and tilt angle in the modulation model to simulate temporal effects due to changes in the large-scale heliospheric plasma. the unusually high cosmic-ray intensities observed during the 2009 solar minimum follow naturally from the current model for most of the energies considered. this demonstrates that changes in turbulence contribute significantly to the high intensities during that solar minimum. we also discuss and illustrate how this model can be used to predict future cosmic-ray intensities, and comment on the reliability of such predictions. | a simplified ab initio cosmic-ray modulation model with simulated time dependence and predictive capability |
the pierre auger observatory, at present the largest cosmic-ray observatory ever built, is instrumented with a ground array of 1600 water-cherenkov detectors, known as the surface detector (sd). the sd samples the secondary particle content (mostly photons, electrons, positrons and muons) of extensive air showers initiated by cosmic rays with energies ranging from 1017ev up to more than 1020ev. measuring the independent contribution of the muon component to the total registered signal is crucial to enhance the capability of the observatory to estimate the mass of the cosmic rays on an event-by-event basis. however, with the current design of the sd, it is difficult to straightforwardly separate the contributions of muons to the sd time traces from those of photons, electrons and positrons. in this paper, we present a method aimed at extracting the muon component of the time traces registered with each individual detector of the sd using recurrent neural networks. we derive the performances of the method by training the neural network on simulations, in which the muon and the electromagnetic components of the traces are known. we conclude this work showing the performance of this method on experimental data of the pierre auger observatory. we find that our predictions agree with the parameterizations obtained by the agasa collaboration to describe the lateral distributions of the electromagnetic and muonic components of extensive air showers. | extraction of the muon signals recorded with the surface detector of the pierre auger observatory using recurrent neural networks |
after the successful detection of cosmic high-energy neutrinos, the field of multiwavelength photon studies of active galactic nuclei (agn) is entering an exciting new phase. the first hint of a possible neutrino signal from the blazar txs 0506+056 leads to the anticipation that agn could soon be identified as point sources of high-energy neutrino radiation, representing another messenger signature besides the established photon signature. to understand the complex flaring behavior at multiwavelengths, a genuine theoretical understanding needs to be developed. these observations of the electromagnetic spectrum and neutrinos can only be interpreted fully when the charged, relativistic particles responsible for the different emissions are modeled properly. the description of the propagation of cosmic rays in a magnetized plasma is a complex question that can only be answered when analyzing the transport regimes of cosmic rays in a quantitative way. in this paper, therefore, a quantitative analysis of the propagation regimes of cosmic rays is presented in the approach that is most commonly used to model non-thermal emission signatures from blazars, i.e., the existence of a high-energy cosmic-ray population in a relativistic plasmoid traveling along the jet axis. it is shown that in the considered energy range of high-energy photon and neutrino emission, the transition between diffusive and ballistic propagation takes place, significantly influencing not only the spectral energy distribution, but also the lightcurve of blazar flares. | propagation of cosmic rays in plasmoids of agn jets-implications for multimessenger predictions |
cluster spiral galaxies suffer catastrophic losses of the cool, neutral gas component of their interstellar medium due to ram pressure stripping, contributing to the observed quenching of star formation in the disc compared to galaxies in lower density environments. however, the short-term effects of ram pressure on the star formation rate and active galactic nucleus (agn) activity of galaxies undergoing stripping remain unclear. numerical studies have recently demonstrated cosmic rays can dramatically influence galaxy evolution for isolated galaxies, yet their influence on ram pressure stripping remains poorly constrained. we perform the first cosmic ray magnetohydrodynamic simulations of an l* galaxy undergoing ram pressure stripping, including radiative cooling, self-gravity of the gas, star formation, and stellar feedback. we find the microscopic transport of cosmic rays plays a key role in modulating the star formation enhancement experienced by spirals at the outskirts of clusters compared to isolated spirals. moreover, we find that galaxies undergoing ram pressure stripping exhibit enhanced gas accretion on to their centres, which may explain the prevalence of agns in these objects. in agreement with observations, we find cosmic rays significantly boost the global radio emission of cluster spirals. although the gas removal rate is relatively insensitive to cosmic ray physics, we find that cosmic rays significantly modify the phase distribution of the remaining gas disc. these results suggest observations of galaxies undergoing ram pressure stripping may place novel constraints on cosmic ray calorimetry and transport. | stress-testing cosmic ray physics: the impact of cosmic rays on the surviving disc of ram-pressure-stripped galaxies |
the cosmic distance duality relation (cddr) has been test through several astronomical observations in the last years. this relation establishes a simple equation relating the angular diameter (da) and luminosity (dl) distances at a redshift z, dlda-1(1 + z)-2 = η = 1 . however, only very recently this relation has been observationally tested at high redshifts (z ≈ 3.6) by using luminosity distances from type ia supernovae (sne ia) and gamma ray bursts (grbs) plus angular diameter distances from strong gravitational lensing (sgl) observations. the results show that no significant deviation from the cddr validity has been verified. in this work, we test the potentialities of future luminosity distances from gravitational waves (gws) sources to impose limit on possible departures of cddr jointly with current sgl observations. the basic advantage of dl from gws is being insensitive to non-conservation of the number of photons. by simulating 600, 900 and 1200 data of gws using the einstein telescope (et) as reference, we derive limits on η(z) function and obtain that the results will be at least competitive with current limits from the sne ia + grbs + sgls analyses. | constraints on the cosmic distance duality relation with simulated data of gravitational waves from the einstein telescope |
recent data on galactic cosmic-ray (cr) leptons and hadrons gave rise to two exciting problems: on the lepton side, the origin of the rise of the cr positron fraction e +/(e - + e +) at ∼10-300 gev of energy; on the hadron side, the nature of the spectral hardening observed in cr protons and nuclei at ∼tev energies. the lepton anomaly indicates the existence of a nearby {{e}+/- } source. it has been proposed that high-energy positrons can be produced inside nearby supernova remnants (snrs) via interactions of cr hadrons with the ambient medium. a distinctive prediction of this mechanism is a high-energy rise of the boron-to-carbon ratio, which has not been observed. it also requires old snrs at work (with ineffective magnetic field amplification and slow shock speed) that cannot account for the cr hadronic spectra observed up to the knee energies (∼5 pev). we propose a new picture where, in addition to such a nearby cr accelerator, the high-energy spectrum of cr hadrons is provided by the large-scale population of snrs, younger on average, which can efficiently accelerate crs up to the knee. under this scenario, the spectral hardening of cr hadrons can be naturally interpreted as the transition between the two components. as we will show, our two-component model breaks the connection between the positron fraction and the boron-to-carbon ratio, which is now predicted to decrease with energy in accordance with the data. forthcoming data from ams will be crucial for testing this model. | the connection between the positron fraction anomaly and the spectral features in galactic cosmic-ray hadrons |
dark matter candidates such as weakly interacting massive particles are predicted to annihilate or decay into standard model particles, leaving behind distinctive signatures in gamma rays, neutrinos, positrons, antiprotons, or even antinuclei. indirect dark matter searches, and in particular those based on gamma-ray observations and cosmic-ray measurements, could detect such signatures. here we review the strengths and limitations of this approach and look into the future of indirect dark matter searches. | indirect dark matter searches in gamma and cosmic rays |
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 |
collisionless shocks with low sonic mach numbers, {m}{{s}}≲ 4, are expected to accelerate cosmic ray (cr) protons via diffusive shock acceleration (dsa) in the intracluster medium (icm). however, observational evidence for cr protons in the icm has yet to be established. performing particle-in-cell simulations, we study the injection of protons into dsa and the early development of a nonthermal particle population in weak shocks in high-β (≈100) plasmas. reflection of incident protons, self-excitation of plasma waves via cr-driven instabilities, and multiple cycles of shock drift acceleration are essential to the early acceleration of cr protons in supercritical quasi-parallel shocks. we find that only in icm shocks with {m}{{s}}≳ {m}{{s}}* ≈ 2.25, a sufficient fraction of incoming protons is reflected by the overshoot in the shock electric potential and magnetic mirror at locally perpendicular magnetic fields, leading to efficient excitation of magnetic waves via cr streaming instabilities and the injection into the dsa process. since a significant fraction of icm shocks have {m}{{s}}< {m}{{s}}* , cr proton acceleration in the icm might be less efficient than previously expected. this may explain why the diffuse gamma-ray emission from galaxy clusters due to proton-proton collisions has not been detected so far. | proton acceleration in weak quasi-parallel intracluster shocks: injection and early acceleration |
we construct a model for cosmic-ray (cr) acceleration from protostellar accretion shocks and calculate the resulting cr ionization rate within star-forming molecular clouds. we couple a protostar cluster model with an analytic accretion shock model to calculate the cr acceleration from protostellar surfaces. we present the cr flux spectrum from kev to gev energies for a typical low-mass protostar. we find that at the shock surface, the spectrum follows a power-law trend across six orders of magnitude in energy. after attenuation, the spectrum at high energies steepens, while at low energies it is relatively flat. we calculate the cr pressure and ionization rates from relativistic protons at the protostellar surface and the edge of the core. we present the cr ionization rate for individual protostars as a function of their instantaneous and final masses. the protostellar cr ionization rate is ζ ≈ 0.01-1 s-1 at the accretion shock surface. however, at the edge of the core, the cr ionization rate drops substantially to between ζ ≈ 10-20 and 10-17 s-1. there is a large spatial gradient in the cr ionization rate, such that inner regions may experience cr ionization rates larger than the often assumed fiducial rate, ζ = 3 × 10-17 s-1. finally, we calculate the cr ionization rate for protostellar clusters over five orders of magnitude of cluster size. we find that clusters with more than approximately 200 protostars produce a higher cr ionization rate within their natal cloud than the fiducial galactic value. | exploration of cosmic-ray acceleration in protostellar accretion shocks and a model for ionization rates in embedded protoclusters |
a ground level enhancement event occurred on 10-11 september 2017, associated with an x8.2 solar flare on the western limb of the sun. we report the results of our manually conducted nowcast using warning system for aviation exposure to solar energetic particles. the maximum radiation dose rate at a flight altitude of 12 km was estimated to be approximately 3 μsv/h, which is less than half of the dose rate due to galactic cosmic rays. we also discuss a possible quasi-parallel shock-acceleration mechanism that may have led to the exceptionally soft proton energy spectrum as ground level enhancement events. | radiation dose nowcast for the ground level enhancement on 10-11 september 2017 |
we present astrochemical photodissociation region models in which cosmic-ray (cr) attenuation has been fully coupled to the chemical evolution of the gas. we model the astrochemical impact of crs, including those accelerated by protostellar accretion shocks, on molecular clouds hosting protoclusters. our models with embedded protostars reproduce observed ionization rates. we study the imprint of cr attenuation on ions for models with different surface cr spectra and different star formation efficiencies. we find that abundances, particularly ions, are sensitive to the treatment of crs. we show the column densities of ions are underpredicted by the “classic” treatment of crs by an order of magnitude. we also test two common chemistry approximations used to infer ionization rates. we conclude that the approximation based on the {{{h}}}3+ abundance underpredicts the ionization rate, except in regions where the crs dominate the chemistry. our models suggest the chemistry in dense gas will be significantly impacted by the increased ionization rates, leading to a reduction in molecules such as nh3 and causing h2-rich gas to become [c ii] bright. | the astrochemical impact of cosmic rays in protoclusters. i. molecular cloud chemistry |
the main signature of the interaction between cosmic rays and molecular clouds is the high ionisation degree. this decreases towards the densest parts of a cloud, where star formation is expected, because of energy losses and magnetic effects. however recent observations hint to high levels of ionisation in protostellar systems, therefore leading to an apparent contradiction that could be explained by the presence of energetic particles accelerated within young protostars. our modelling consists of a set of conditions that has to be satisfied in order to provide an efficient particle acceleration through the diffusive shock acceleration mechanism. we find that jet shocks can be strong accelerators of protons which can be boosted up to relativistic energies. another possibly efficient acceleration site is located at protostellar surfaces, where shocks caused by impacting material during the collapse phase are strong enough to accelerate protons. our results demonstrate the possibility of accelerating particles during the early phase of a proto-solar-like system and can be used as an argument to support available observations. the existence of an internal source of energetic particles can have a strong and unforeseen impact on the star and planet formation process as well as on the formation of pre-biotic molecules. | cosmic-ray acceleration in young protostars |
the all-sky planck survey in 9 frequency bands was used to search for emission from all 274 known galactic supernova remnants. of these, 16 were detected in at least two planck frequencies. the radio-through-microwave spectral energy distributions were compiled to determine the mechanism for microwave emission. in only one case, ic 443, is there high-frequency emission clearly from dust associated with the supernova remnant. in all cases, the low-frequency emission is from synchrotron radiation. as predicted for a population of relativistic particles with energy distribution that extends continuously to high energies, a single power law is evident for many sources, including the crab and pks 1209-51/52. a decrease in flux density relative to the extrapolation of radio emission is evident in several sources. their spectral energy distributions can be approximated as broken power laws, sν ∝ ν-α, with the spectral index, α, increasing by 0.5-1 above a break frequency in the range 10-60 ghz. the break could be due to synchrotron losses. | planck intermediate results. xxxi. microwave survey of galactic supernova remnants |
in our galaxy, light antinuclei composed of antiprotons and antineutrons can be produced through high-energy cosmic-ray collisions with the interstellar medium or could also originate from the annihilation of dark-matter particles that have not yet been discovered. on earth, the only way to produce and study antinuclei with high precision is to create them at high-energy particle accelerators. although the properties of elementary antiparticles have been studied in detail, the knowledge of the interaction of light antinuclei with matter is limited. we determine the disappearance probability of $^{3}\overline{\rm he}$ when it encounters matter particles and annihilates or disintegrates within the alice detector at the large hadron collider. we extract the inelastic interaction cross section, which is then used as input to calculations of the transparency of our galaxy to the propagation of $^{3}\overline{\rm he}$ stemming from dark-matter annihilation and cosmic-ray interactions within the interstellar medium. for a specific dark-matter profile, we estimate a transparency of about 50%, whereas it varies with increasing $^{3}\overline{\rm he}$ momentum from 25% to 90% for cosmic-ray sources. the results indicate that $^{3}\overline{\rm he}$ nuclei can travel long distances in the galaxy, and can be used to study cosmic-ray interactions and dark-matter annihilation. | measurement of of $^{3}\\overline{\\rm he}$ nuclei absorption in matter and impact on their propagation in the galaxy |
recent high-energy cosmic e± measurement from the dark matter particle explorer (dampe) satellite confirms the deviation of total cosmic ray electron spectrum above 700-900 gev from a simple power law. in this paper, we demonstrate that the cascade decay of dark matter (dm) can account for dampe's tev e+e- spectrum. we select the least constraint dm decay channel into four muons as the benchmark scenario, and perform an analysis with propagation variance in both dm signal and the milky way's electron background. the best fit of the model is obtained for joint dampe, fermi-large area telescope (fermi-lat), high energy stereoscopic system (hess) high-energy electron data sets, and with an o(10^{26}) second decay lifetime, which is consistent with existing gamma-ray and cosmic microwave background limits. we compare the spectral difference between the cascade decay of typical final-state channels. the least constrained 4μ channels give good fits to the electron spectrum's tev scale downturn, yet their low-energy spectrum has tension with sub-tev positron data from ams02 (alpha magnetic spectrometer). we also consider a three-step cascade decay into eight muons, and a gamma-ray constrained 4μ-4b mixed channel, to demonstrate that a further softened cascade decay signal would be required for the agreement with all the cosmic e^{±} data sets. | implications of dark matter cascade decay from dampe, hess, fermi-lat, and ams02 data |
we scrutinize the paradigm that conventional long-duration gamma-ray bursts (grbs) are the dominant source of the ultrahigh energy cosmic rays (uhecrs) within the internal shock scenario by describing uhecr spectrum and composition and by studying the predicted (source and cosmogenic) neutrino fluxes. since it has been demonstrated that the stacking searches for astrophysical grb neutrinos strongly constrain the parameter space in single-zone models, we focus on the dynamics of multiple collisions for which different messengers are expected to come from different regions of the same object. we propose a model that can describe both stochastic and deterministic engines, which we study in a systematic way. we find that grbs can indeed describe the uhecrs for a wide range of different model assumptions with comparable quality albeit with the previously known problematic energy requirements; the heavy mass fraction at injection is found to be larger than 70 per cent ( $95 {{\ \rm per\ cent}}$ cl). we demonstrate that the post-dicted (from uhecr data) neutrino fluxes from sources and uhecr propagation are indeed below the current sensitivities but will be reached by the next generation of experiments. we finally critically review the required source energetics with the specific examples found in this study. | systematic parameter space study for the uhecr origin from grbs in models with multiple internal shocks |
context. phosphorus-bearing species are essential to the formation of life on earth, however they have barely been detected in the interstellar medium. in particular, towards star-forming regions only pn and po have been identified so far. since only a small number of detections of p-bearing molecules are available, their chemical formation pathways are not easy to constrain and are thus highly debatable. an important factor still missing in the chemical models is the initial elemental abundance of phosphorus, that is, the depletion level of p at the start of chemical models of dense clouds.aims: in order to overcome this problem, we study p-bearing species in diffuse and translucent clouds. in these objects phosphorus is expected to be mainly in the gas phase and therefore the elemental initial abundance needed in our chemical simulations corresponds to the cosmic one and is well constrained.methods: for the study of p-bearing chemistry we used an advanced chemical model. we updated and significantly extended the p-chemistry network based on chemical databases and previous literature. we performed single-pointing observations with the iram 30 m telescope in the 3 mm range towards the line of sight to the strong continuum source b0355+508 aiming for the (2-1) transitions of pn, po, hcp, and cp. this line of sight incorporates five diffuse and/or translucent clouds.results: the (2-1) transitions of the pn, po, hcp, and cp were not detected. we report high signal-to-noise-ratio detections of the (1-0) lines of 13co, hnc, and cn along with a first detection of c34s towards this line of sight. we have attempted to reproduce the observations of hnc, cn, cs, and co in every cloud with our model by applying typical physical conditions for diffuse or translucent clouds. we find that towards the densest clouds with vlsr = -10, - 17 km s-1 the best-fit model is given by the parameters (n(h), av, tgas) = (300 cm-3, 3 mag, 40 k).conclusions: according to our best-fit model, the most abundant p-bearing species are hcp and cp (~10-10). the molecules pn, po, and ph3 also show relatively high predicted abundances of ~10-11. we show that the abundances of these species are sensitive to visual extinction, cosmic-ray ionization rate, and the diffusion-to-desorption energy ratio on dust grains. the production of p-bearing species is favored towards translucent rather than diffuse clouds, where the environment provides a stronger shielding from the interstellar radiation. based on our improved model, we show that the (1-0) transitions of hcp, cp, pn, and po are expected to be detectable with estimated intensities of up to ~200 mk. the phosphorus chemical network and the 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/cat/j/a+a/633/a54 based on observations carried out with the iram 30 m telescope. iram is supported by insu/cnrs (france), mpg (germany), and ign (spain). | the first steps of interstellar phosphorus chemistry |
the last measurement of the diffuse emission spectrum of the milky way in the megaelectronvolt (mev) photon energy range was performed by cgro/comptel more than 20 yr ago. we report a new analysis with the spectrometer spi aboard integral in the band 0.5-8.0 mev, finally superseding the signal-to-noise ratio (s/n) of the historic observations. this is possible thanks to an elaborate instrumental background model and careful considerations of the selected data, which are strongly affected by solar activity. we base our analysis on energy-dependent spatial template fitting in a region of δl ×δb = 95° ×95° around the galactic centre. our flux estimates are consistent with comptel measurements and show no `mev bump' the spectrum follows a power-law shape with index −1.39 ± 0.09stat ± 0.10syst and an integrated flux of (5.7 ± 0.8stat ± 1.7syst) x 10−8 erg cm−2 s−1 between 0.5 and 8.0 mev. we find that cosmic-ray electrons and propagation models consistent with the latest fermi/lat, voyager 1, and ams-02 data are broadly in agreement with the inferred inverse compton spectral shape. however, a mismatch of a factor of 2-3 in normalisation with respect to baseline expectations may point to enhanced target photon densities and/or electron source spectra in the inner galaxy, slightly modified diffusion properties, or the presence of an unresolved population of mev γ-ray sources. | diffuse galactic emission spectrum between 0.5 and 8.0 mev |
cosmic ray atmospheric showers provide an effective environment for the production of mev-scale dark sector particles. we show that, when available, the resonant annihilation of positrons from the shower on atmospheric electrons is the dominant production mechanism by more than an order of magnitude. we provide a quantitative example based on dark photon production and update existing constraints on a corresponding light dark matter model from kilotons neutrino experiments and xenon-based direct detection experiments. | atmospheric resonant production for light dark sectors |
by combining swampland conjectures with observational data, it was recently pointed out that our universe could stretch off in an asymptotic region of the string landscape of vacua. within this framework, the cosmological hierarchy problem (i.e. the smallness of the cosmological constant in planck units: λ ∼ 10-122 mpl4) can be naturally resolved by the addition of one mesoscopic (dark) dimension of size ∼ λλ - 1 / 4 ∼ 1 μm . the planck scale of the higher dimensional theory, muv ∼λ - 1 / 3λ 1 / 12mpl2/3 ∼ 1010 gev , is tantalizingly close to the energy above which the telescope array (ta) and the pierre auger collaborations found conclusive evidence for a sharp cutoff of the flux of ultra-high-energy cosmic rays (uhecrs). it was recently suggested that since physics becomes strongly coupled to gravity beyond muv, universal features deep-rooted in the dark dimension could control the energy cutoff of the source spectra ∝e-γ exp(- e /muv) , where e is the cosmic ray energy and γ a free parameter. conversely, in the absence of phenomena inborn within the dark dimension, we would expect a high variance of the cosmic ray maximum energy emax characterizing the source spectra ∝e-γ exp(- e /emax) , reflecting the many different properties inherent to the most commonly assumed uhecr accelerators. the most recent analysis of auger and ta data exposed strong evidence for a correlation between uhecrs and nearby starburst galaxies, with a global significance post-trial of 4 . 7 σ . since these galaxies are in our cosmic backyard, the flux attenuation factor due to cosmic ray interactions en route to earth turns out to be negligible. this reasoning implies that for each source, the shape of the observed spectrum should roughly match the emission spectrum by the starburst, providing a unique testing ground for the dark dimension hypothesis. using auger data, we carry out a maximum likelihood analysis to characterize the shape of the uhecr emission from the galaxies dominating the anisotropy signal. we show that the observed spectra from these sources could be universal only if λ ≲ 10-3 . | probing the dark dimension with auger data |
the online reconstruction of muon tracks in high energy physics experiments is a highly demanding task, typically performed on reconfigurable digital circuits, such as fpgas. complex analytical algorithms are executed in a quasi-real-time environment to identify, select, and reconstruct local tracks in often noise-rich environments. a novel approach to the generation of local triggers based on a hybrid combination of artificial neural networks and analytical methods is proposed, targeting the muon reconstruction for drift tube detectors. the proposed algorithm exploits neural networks to solve otherwise computationally expensive analytical tasks for the unique identification of coherent signals and the removal of geometrical ambiguities. the proposed approach is deployed on state-of-the-art fpga and its performances are evaluated on simulation and on data collected from cosmic rays. | muon trigger with fast neural networks on fpga, a demonstrator |
secondary particles produced in spallation reactions of cosmic rays with the interstellar gas provide valuable information that allow us to investigate the injection and transport of charged particles in the galaxy. a good understanding of the cross sections of production of these particles is crucial to correctly interpret our models, although the existing experimental data is very scarce and uncertain. we have developed a new set of cross sections, both inelastic and inclusive, computed with the fluka monte carlo nuclear code and tested its compatibility with cr data. inelastic and inclusive cross sections have been compared to the most up-to-date data and parameterisations finding a general good agreement. then, these cross sections have been implemented in the dragon2 code to characterize the spectra of cr nuclei up to z = 26 and the secondary-to-primary ratios of b, be and li. interestingly, we find that the fluka cross sections allow us to predict an energy-dependence of the b, be and li flux ratios which is compatible with ams-02 data and to reproduce simultaneously these flux ratios with a scaling lower than 20%. finally, we implement the cross sections of production of gamma rays, calculated with fluka, in the gammasky code and compute diffuse gamma-ray sky maps and the local hi emissivity spectrum, finding a very good agreement with fermi large area telescope data. | fluka cross sections for cosmic-ray interactions with the dragon2 code |
young massive star clusters inhabit regions of star formation and play an essential role in the galactic evolution. they are sources of both thermal and non-thermal radiation, and are effective cosmic ray accelerators. we present the 3d magnetohydrodynamic modelling of the plasma flows in a young compact cluster at the evolutionary stage comprising multiple interacting supersonic winds of massive ob and wr stars. the modelling allows studying the partitioning of the mechanical energy injected by the winds between the bulk motions, thermal heating, and magnetic fields. cluster-scale magnetic fields reaching the magnitudes of ~300 $\mu$g show the filamentary structures spreading throughout the cluster core. the filaments with the high magnetic fields are produced by the axford-cranfill-type effect in the downstream of the wind termination shocks, which is amplified by a compression of the fields with the hot plasma thermal pressure in the central part of the cluster core. the hot (~a few kev) plasma is heated at the termination shocks of the stellar winds and compressed in the colliding post-shock flows. we also discuss a possible role of the thermal conduction effects on the plasma flow, and analyse temperature maps in the cluster core and the diffuse thermal x-ray emission spectra. the presence of high cluster-scale magnetic fields supports the possibility of high-energy cosmic ray acceleration in clusters at the given evolutionary stage. | inside the core of a young massive star cluster: 3d mhd simulations |
cosmic ray muons have been considered as a non-conventional radiation probe in various applications. to utilize cosmic ray muons in engineering applications, two important quantities, trajectory and momentum, must be known. the muon trajectories are easily reconstructed using two-fold detector arrays with a high spatial resolution. however, precise measurement of muon momentum is difficult to be achieved without deploying large and expensive spectrometers such as solenoid magnets. here, we propose a new method to estimate muon momentum using multi-layer pressurized gas cherenkov radiators. this is accurate, portable, compact (< 1m3), and easily coupled with existing muon detectors without the need of neither bulky magnetic nor time-of-flight spectrometers. the results show that not only our new muon spectrometer can measure muon momentum with a resolution of ± 0.5 gev/c in a momentum range of 0.1-10.0 gev/c, but also we can reconstruct cosmic muon spectrum with high accuracy (~ 90%). | fieldable muon spectrometer using multi-layer pressurized gas cherenkov radiators and its applications |
this paper studies cosmic-ray (cr) transport in magnetohydrodynamic (mhd) turbulence. cr transport is strongly dependent on the properties of the magnetic turbulence. we perform test particle simulations to study the interactions of cr with both total mhd turbulence and decomposed mhd modes. the spatial diffusion coefficients and the pitch angle scattering diffusion coefficients are calculated from the test particle trajectories in turbulence. our results confirm that the fast modes dominate the cr propagation, whereas alfvén and slow modes are much less efficient and have shown similar pitch-angle scattering rates. we investigate the cross field transport on large and small scales. on large/global scales, normal diffusion is observed and the diffusion coefficient is suppressed by ${m}_{a}^{\zeta }$ compared to the parallel diffusion coefficients, with ζ closer to 4 in alfvén modes than that in total turbulence, as theoretically expected. for the cr transport on scales smaller than the turbulence injection scale, both the local and global magnetic reference frames are adopted. superdiffusion is observed on such small scales in all the cases. particularly, cr transport in alfvén modes show clear richardson diffusion in the local reference frame. the diffusion transitions smoothly from the richardson's one with index 1.5 to normal diffusion as the particle mean free path decreases from λ ∥ ≫ l to λ ∥ ≪ l, where l is the injection/coherence length of turbulence. our results have broad applications to crs in various astrophysical environments. | cosmic-ray transport in magnetohydrodynamic turbulence |
known sources of lithium (li) in the universe include the big bang, novae, asymptotic giant branch stars, and cosmic-ray spallation. during their longer-lived evolutionary phases, stars are not expected to add to the li budget of the galaxy, but to largely deplete it. in this context, recent analyses of li data from galah and lamost for field red clump (rc) stars have concluded that there is the need for a new production channel of li, ubiquitous among low-mass stars, and that would be triggered on the upper red giant branch (rgb) or at helium ignition. this is distinct from the li-rich giant problem and reflects bulk rc star properties. we provide an analysis of the galah li data that accounts for the distribution of progenitor masses of field rc stars observed today. such progenitors are different than today's field rgb stars. using standard post-main-sequence stellar evolution, we show that the distribution of li among field rc giants as observed by galah is consistent with standard model predictions, and does not require new li production mechanisms. our model predicts a large fraction of very low li abundances from low-mass progenitors, with higher abundances from higher mass ones. moreover, there should be a large number of upper limits for rc giants, and higher abundances should correspond to higher masses. the most recent galah data indeed confirm the presence of large numbers of upper limits, and a much lower mean li abundance in rc stars, in concordance with our interpretation. | mass matters: no evidence for ubiquitous lithium production in low-mass clump giants |
the ams-02 experiment is measuring the high energy cosmic rays with unprecedented accuracy. we explore the possibility of determining the cosmic-ray propagation models using the ams-02 data alone. a global bayesian analysis of the constraints on the cosmic-ray propagation models from the preliminary ams-02 data on the boron to carbon nuclei flux ratio and proton flux is performed, with the assumption that the primary nucleon source is a broken power law in rigidity. the ratio of the diffusion coefficient d0 to the diffusive halo height zh is determined with high accuracy d0/zh≃ 2.00±0.07 cm2s-1kpc-1, and the value of the halo width is found to be zh≃ 3.3 kpc with uncertainty less than 50%. as a consequence, the typical uncertainties in the positron fraction predicted from dark matter (dm) annihilation is reduced to a factor of two, and that in the antiproton flux is about an order of magnitude. both of them are significantly smaller than that from the analyses prior to ams-02. taking into account the uncertainties and correlations in the propagation parameters, we derive conservative upper limits on the cross sections for dm annihilating into various standard model final states from the current pamela antiproton data. we also investigate the reconstruction capability of the future high precision ams-02 antiproton data on the dm properties. the results show that for dm particles lighter than 0~ 10 gev and with typical thermal annihilation cross section, the cross section can be well reconstructed with uncertainties about a factor of two for the ams-02 three-year data taking. | cosmic ray propagation and dark matter in light of the latest ams-02 data |
we reconsider the possibility that gamma-ray bursts (grbs) are the sources of the ultra-high energy cosmic rays (uhecrs) within the internal shock model, assuming a pure proton composition of the uhecrs. for the first time, we combine the information from gamma-rays, cosmic rays, prompt neutrinos, and cosmogenic neutrinos quantitatively in a joint cosmic ray production and propagation model, and we show that the information on the cosmic energy budget can be obtained as a consequence. in addition to the neutron model, we consider alternative scenarios for the cosmic ray escape from the grbs, i.e., that cosmic rays can leak from the sources. we find that the dip model, which describes the ankle in uhecr observations by the pair production dip, is strongly disfavored in combination with the internal shock model because (a) unrealistically high baryonic loadings (energy in protons versus energy in electrons/gamma-rays) are needed for the individual grbs and (b) the prompt neutrino flux easily overshoots the corresponding neutrino bound. on the other hand, grbs may account for the uhecrs in the ankle transition model if cosmic rays leak out from the source at the highest energies. in that case, we demonstrate that future neutrino observations can efficiently test most of the parameter space - unless the baryonic loading is much larger than previously anticipated. | are gamma-ray bursts the sources of ultra-high energy cosmic rays? |
we examine a sample of 106 galaxies for which the total luminosities of the two fine structure lines 3p1 → 3p0, and 3p2 → 3p1 of neutral atomic carbon (c) are available, and find their average excitation conditions to be strongly subthermal. this is deduced from the ci(2-1)/(1-0) ratios ($\rm r^{(ci)}_{21/10}$) modeled by the exact solutions of the corresponding three-level system, without any special assumptions about the kinematic state of the concomitant $\rm h_2$ gas (and thus the corresponding line formation mechanism). this non-lte excitation of the ci lines can induce the curious clustering of (ci,lte)-derived gas temperatures near ~25 k reported recently by valentino et al. (2020), which is uncorrelated to the actual gas temperatures. the non-lte ci line excitation in the interstellar medium of galaxies deprives us from a simple method for estimating molecular gas temperatures, and adds uncertainty in ci-based molecular gas mass estimates especially when the j = 2-1 line is used. however the $\rm r^{(ci)}_{21/10}$ = $\rm f(n, t_{k})$ ratio is now more valuable for joint co/ci sled and dust sed models of galaxies, and independent of the assumptions used in the co radiative transfer models (e.g. the large velocity gradient approximation). finally we speculate that the combination of low ratios $\rm r^{(ci)}_{21/10} \lesssim 1$ and high $\rm t_{dust}$ values found in some extreme starbursts indicates massive low-density molecular wind and/or circumgalactic gas reservoirs. if verified by imaging observations this can be a useful indicator of the presence of such reservoirs in galaxies. | the subthermal excitation of the c i lines in the molecular gas reservoirs of galaxies: its significance and potential utility |
today's geomagnetic field can prevent energetic particles, including solar energetic particles and galactic cosmic rays, from directly hitting the earth's atmosphere. however, when the geomagnetic field strength is significantly decreased during geomagnetic field excursions or reversals, the geomagnetic field shielding effect becomes less prominent. geomagnetic cutoff rigidity, as a quantitative estimation of the shielding effect, can be calculated using trajectory tracing or theoretical equations. we use a recent high-resolution continuous geomagnetic field model (lsmod.2) to study the geomagnetic cutoff rigidity during the laschamps excursion. global grids of the geomagnetic cutoff rigidities are presented, in particular for the excursion midpoint when the geomagnetic field is weak and not dipole-dominated anymore at earth's surface. we compare the cutoff rigidity calculation results between a trajectory tracing program and theoretical equations and we find that the influence of the non-dipole component of the geomagnetic field cannot be ignored during the excursion. our results indicate that the exposure of earth's atmosphere to energetic particles of cosmic and solar origin is high and nearly independent of latitude in the middle of the laschamps excursion. our results will be useful for future studies associated with cosmic radiation dose rate and cosmogenic isotope production rate during the laschamps excursion. | effects of the laschamps excursion on geomagnetic cutoff rigidities |
core ideas cosmic‑ray neutron data are used to inversely estimate soil hydraulic properties. the forward neutron operator cosmic is coupled with the vadose zone model hydrus‑1d. bayesian analyses confirm the information content of cosmic‑ray neutron data. observations of soil moisture content from remote sensing platforms can be used in conjunction with hydrological models to inversely estimate soil hydraulic properties (shps). in recent years, cosmic‑ray neutron sensing (crns) has proven to be a reliable method for the estimation of area‑average soil moisture at field scales. however, its use in the inverse estimation of the effective shps is largely unexplored. thus, the main objective of this study was to assess the information content of aboveground fast‑neutron counts to estimate shps using both a synthetic modeling study and actual experimental data from the rollesbroich catchment in germany. for this, the forward neutron operator cosmic was externally coupled with the hydrological model hydrus‑1d. the coupled model was combined with the affine invariant ensemble sampler to calculate the posterior distributions of effective soil hydraulic parameters as well as the model‑predictive uncertainty for different synthetic and experimental scenarios. measured water contents at different depths were used to assess estimated shps. the analysis of both synthetic and actual crns data from homogenous and heterogeneous soil profiles, respectively, led to confident estimations of the shape parameters α and n, while higher uncertainty was observed for the saturated hydraulic conductivity. furthermore, results demonstrated that neutron data are less influenced by local sources of uncertainty compared with near‑surface point measurements. the simultaneous use of crns and water content data further reduced the overall uncertainty, opening up new perspectives for the combination of crns with other remote sensing techniques for the inverse estimation of the effective shps. | on the information content of cosmic‑ray neutron data in the inverse estimation of soil hydraulic properties |
more than 3 decades after the discovery of the ozone hole, the processes involved in its formation are believed to be understood in great detail. current state-of-the-art models can reproduce the observed chemical composition in the springtime polar stratosphere, especially regarding the quantification of halogen-catalysed ozone loss. however, we report here on a discrepancy between simulations and observations during the less-well-studied period of the onset of chlorine activation. during this period, which in the antarctic is between may and july, model simulations significantly overestimate hcl, one of the key chemical species, inside the polar vortex during polar night. this hcl discrepancy is also observed in the arctic. the discrepancy exists in different models to varying extents; here, we discuss three independent ones, the chemical lagrangian model of the stratosphere (clams) as well as the eulerian models sd-waccm (the specified dynamics version of the whole atmosphere community climate model) and tomcat/slimcat. the hcl discrepancy points to some unknown process in the formulation of stratospheric chemistry that is currently not represented in the models. we characterise the hcl discrepancy in space and time for the lagrangian chemistry-transport model clams, in which hcl in the polar vortex core stays about constant from june to august in the antarctic, while the observations indicate a continuous hcl decrease over this period. the somewhat smaller discrepancies in the eulerian models sd-waccm and tomcat/slimcat are also presented. numerical diffusion in the transport scheme of the eulerian models is identified to be a likely cause for the inter-model differences. although the missing process has not yet been identified, we investigate different hypotheses on the basis of the characteristics of the discrepancy. an underestimated hcl uptake into the polar stratospheric cloud (psc) particles that consist mainly of h2o and hno3 cannot explain it due to the temperature correlation of the discrepancy. also, a direct photolysis of particulate hno3 does not resolve the discrepancy since it would also cause changes in chlorine chemistry in late winter which are not observed. the ionisation caused by galactic cosmic rays provides an additional nox and hox source that can explain only about 20 % of the discrepancy. however, the model simulations show that a hypothetical decomposition of particulate hno3 by some other process not dependent on the solar elevation, e.g. involving galactic cosmic rays, may be a possible mechanism to resolve the hcl discrepancy. since the discrepancy reported here occurs during the beginning of the chlorine activation period, where the ozone loss rates are small, there is only a minor impact of about 2 % on the overall ozone column loss over the course of antarctic winter and spring. | on the discrepancy of hcl processing in the core of the wintertime polar vortices |
28 february 2017 marked 75 years since the first confident registration of solar cosmic rays (scrs), i.e., accelerated solar particles with energies from about 106 to 1010 ÷ 1011 ev. modern state of the problems related to the studies of ground level enhancements (gles) of relativistic scrs is critically analyzed based on available direct and proxy data. we are also taking into account extremely large fluxes of non-relativistic solar energetic particles (seps). both kinds of scr events are of great astrophysical and geo-scientific (geophysical) interests. a number of the gle properties (total statistics, occurrence rate, longitude distribution, ranking of gles, a number of specific gles - so-called "rogue" sep events etc.) are discussed in some detail. we note also the problems of gle identification (definition) by ground-based observations, the difficulties in the studies of weak ("hidden", or sub-) gles etc. one of serious challenges to the problem of radiation hazard in space is a lack of a clear, unambiguous relation between the fluxes (fluences) of relativistic scr and non-relativistic seps. special attention is paid to the recent debate on the validity, origin and properties of the "ancient" events ad775, ad994, ad1859 (carrington event) and bc3372. we demonstrate that, in spite of existing uncertainties in proton fluences above 30 mev, all of them are fitted well by a unique distribution function, at least, with the present level of solar activity. extremely large sep events are shown to obey a probabilistic distribution on their fluences with a sharp break in the range of large fluences (or low probabilities). the studies of this kind may be extended for periods with different levels of solar activity in the past and/or in the future. dose rates at aircraft altitudes are also demonstrated during some gles. several examples of using the scr data and gle properties in radiation prediction schemes are considered. | retrospective analysis of gles and estimates of radiation risks |
cosmic ray muon radiography utilizes highly penetrating cosmic ray muons to image the density profile of an object of interest. here we report on a trial to use a portable field-deployable cosmic ray muon tracking system in order to image the whole overburden of a uk railway tunnel with short-duration scans (c. 30 min). an unknown overburden void was identified and, after trial, confirmed by railway authorities. these experiments demonstrate the identification of hidden construction shafts with high levels of statistical significance as density anomalies within the data. | muon tomography for railway tunnel imaging |
cosmic-ray neutron sensing (crns) is a promising non-invasive technique to estimate snow water equivalent (swe) over large areas. in contrast to preliminary studies focusing on shallow snow conditions (swe <130 mm), more recently the method was shown experimentally to be sensitive also to deeper snowpacks providing the basis for its use at mountain experimental sites. however, hysteretic neutron response has been observed for complex snow cover including patchy snow-free areas. in the present study we aimed to understand and support the experimental findings using a comprehensive neutron modeling approach. several simulations have been set up in order to disentangle the effect on the signal of different land surface characteristics and to reproduce multiple observations during periods of snow melt and accumulation. to represent the actual land surface heterogeneity and the complex snow cover, the model used data from terrestrial laser scanning. the results show that the model was able to accurately reproduce the crns signal and particularly the hysteresis effect during accumulation and melting periods. moreover, the sensor footprint was found to be anisotropic and affected by the spatial distribution of liquid water and snow as well as by the topography of the nearby mountains. under fully snow-covered conditions the crns is able to accurately estimate swe without prior knowledge about snow density profiles or other spatial anomalies. these results provide new insights into the characteristics of the detected neutron signal in complex terrain and support the use of crns for long-term snow monitoring in high elevated mountain environments. | sensing area-average snow water equivalent with cosmic-ray neutrons: the influence of fractional snow cover |
the respective impacts of northern and southern hemispheric climatic changes on the tropics during the last deglaciation remain poorly understood. in the high tropical andes, the antarctic cold reversal (acr, 14.3-12.9 ka bp) is better represented among morainic records than the younger dryas (12.9-11.7 ka bp). however, in the altiplano basin (bolivia), two cold periods of the northern hemisphere (heinrich stadial 1a, 16.5-14.5 ka bp, and the younger dryas) are synchronous with (i) major advances or standstills of paleoglaciers and (ii) the highstands of giant paleolakes tauca and coipasa. here, we present new cosmic ray exposure (cre) ages from glacial landforms of the bolivian andes that formed during the last deglaciation (termination 1). we reconstruct the equilibrium line altitudes (ela) associated with each moraine and use them in an inverse algorithm combining paleoglaciers and paleolake budgets to derive temperature and precipitation during the last deglaciation. our temperature reconstruction (δt relative to present day) yields a consistent regional trend of progressive warming from δt = -5 to -2.5 °c during 17-14.5 ka bp, followed by a return to colder conditions around -4 °c during the acr (14.5-12.9 ka bp). the coipasa highstand (12.9-11.8 ka bp) is coeval with another warming trend followed by δt stabilization at the onset of the holocene (ca. 10 ka bp), around -3 °c. our results suggest that, during the last deglaciation (20-10 ka bp) atmospheric temperatures in the tropical andes mimicked antarctic variability, whereas precipitation over the altiplano was driven by changes in the northern hemisphere. | antarctic-like temperature variations in the tropical andes recorded by glaciers and lakes during the last deglaciation |
as a fundamental astrophysical process, the scattering of particles by turbulent magnetic fields has its physical foundation laid by the magnetohydrodynamic (mhd) turbulence theory. in the framework of the modern theory of mhd turbulence, we derive a generalized broadened resonance function by taking into account both the magnetic fluctuations and nonlinear decorrelation of turbulent magnetic fields arising in mhd turbulence, and we specify the energy range of particles for the dominance of different broadening mechanisms. the broadened resonance allows for scattering of particles beyond the energy threshold of the linear resonance. by analytically determining the pitch-angle diffusion coefficients for transit time damping (ttd) with slow and fast modes, we demonstrate that the turbulence anisotropy of slow modes suppresses their scattering efficiency. furthermore, we quantify the dependence of the relative importance between slow and fast modes in ttd scattering on (i) particle energy, (ii) plasma β (the ratio of gas pressure to magnetic pressure), and (iii) damping of mhd turbulence, and we also provide the parameter space for the dominance of slow modes. to exemplify its applications, we find that among typical partially ionized interstellar phases, in the warm neutral medium slow and fast modes have comparable efficiencies in ttd scattering of cosmic rays. for low-energy particles, e.g., sub-alfvénic charged grains, we show that slow modes always dominate ttd scattering. | resonance-broadened transit time damping of particles in mhd turbulence |
the discovery of extraterrestrial neutrinos in the ∼30 tev - pev energy range by icecube provides new constraints on high energy astrophysics. an important background to the signal are the prompt neutrinos which originate from the decay of charm hadrons produced by high energy cosmic-ray particles interacting in the earth's atmosphere. it is conventional to use the calculations of charm hadroproduction using gluon splitting g →c c ¯ alone. however, qcd predicts an additional "intrinsic" component of the heavy quark distribution which arises from diagrams where heavy quarks are multiply connected to the proton's valence quarks. we estimate the prompt neutrino spectrum due to intrinsic charm. we find that the atmospheric prompt neutrino flux from intrinsic charm is comparable to those calculated using qcd computations not including intrinsic charm, once we normalize the intrinsic charm differential cross sections to the isr and the lebc-mps collaboration data. in the future, icecube will constrain the intrinsic charm content of the proton and will contribute to one of the major questions in high energy physics phenomenology. | icecube can constrain the intrinsic charm of the proton |
we predict quantitative mass-loss rates and terminal wind velocities for early-type supergiants and luminous blue variables (lbvs) using a dynamical version of the monte carlo radiative transfer method. first, the observed drop in terminal wind velocity around spectral type b1 is confirmed by the monte carlo method at the correct effective temperature of about 21 000 k. this drop in wind velocity is much steeper than would be expected from the drop in escape speed for cooler stars. the results may be particularly relevant for slow winds inferred for some high-mass x-ray binaries. second, the strength of the mass-loss bi-stability jump is found to be significantly greater than previously assumed. this could this make bi-stability braking more efficient in massive star evolution; in addition, a rotationally induced version of the bi-stability mechanism may now be capable of producing the correct density of outflowing disks around b[e] supergiants, although multi-dimensional modelling including the disk velocity structure is still needed. for lbvs we find that the bi-stability jump becomes larger at higher metallicities, but perhaps surprisingly also larger at lower eddington parameters. this may have consequences for the role of lbvs in the evolution of massive stars at different metallicities and cosmic epochs. finally, our predicted low wind velocities may be important for explaining the slow outflow speeds of supernova type iib/iin progenitors, for which the direct lbv-sn link was first introduced. | fast and slow winds from supergiants and luminous blue variables |
the chinese satellite wukong, also known as the dark matter particle explorer (dampe), has released its observation data of the cosmic ray (cr) electrons and positrons. the data shows an excess in the energy spectrum up to tev energy, and possibly a peak-like fine structure at $\sim 1.4 \tev$. we investigate the scenario that the source of the excess comes from dark matter annihilation or decay. we find that the annihilation or decay of diffuse dark matter particles in the galactic halo can give excellent ($w^+w^-$ channel) or at least good (double $\tau^+\tau^-$ channel) fits to the broad excess. however, the annihilation cross-section is $10^{-23}\cm^3s^{-1}$, larger than required for getting the correct relic abundance. we then study whether the narrow peak at $\sim 1.4\tev$ could be explained by a nearby subhalo, which thanks to the smaller distance, could supply $e^+e^-$ within a narrow energy range. we find that in order to produce a peak width less than the energy bin width (0.2 tev), the source must be located within $r\lsim 0.53~\kpc$. our global fit models do not produce the peak-like feature, instead at 1.4 tev the spectrum show either a slope or a cliff-like feature. however, if less than optimal fit is allowed, the peak-like feature could be generated. furthermore, an excellent fit with peak could be obtained with model b if the background is rescaled. if the dark matter decay and annihilation rates are determined using the broad excess, the required subhalo mass $\sim10^{5}~m_\odot$ for decay model, or $\sim10^{4.5}\msun$ for annihilation model and a shallower density profile slope $\alpha=1.2$, or $\sim10^{2.5}\msun$ for the steep density profile $\alpha=1.7$. however, the probability for the existence of a such nearby subhalo as massive as given above is very low. | cosmic ray $e^{+} e^{-}$ spectrum excess and peak feature observed by the dampe experiment from dark matter |
context. small amounts of atomic hydrogen, detected as absorption dips in the 21 cm line spectrum, are a well-known characteristic of dark clouds. the abundance of hydrogen atoms measured in the densest regions of molecular clouds can only be explained by the dissociation of h2 by cosmic rays.aims: we wish to assess the role of galactic cosmic rays in the formation of atomic hydrogen, for which we use recent developments in the characterisation of the low-energy spectra of cosmic rays and advances in the modelling of their propagation in molecular clouds.methods: we modelled the attenuation of the interstellar cosmic rays that enter a cloud and computed the dissociation rate of molecular hydrogen that is due to collisions with cosmic-ray protons and electrons as well as fast hydrogen atoms. we compared our results with the available observations.results: the cosmic-ray dissociation rate is entirely determined by secondary electrons produced in primary ionisation collisions. these secondary particles constitute the only source of atomic hydrogen at column densities above 1021 cm-2. we also find that the dissociation rate decreases with column density, while the ratio between the dissociation and ionisation rates varies between about 0.6 and 0.7. from comparison with observations, we conclude that a relatively flat spectrum of interstellar cosmic-ray protons, such as suggested by the most recent voyager 1 data, can only provide a lower bound for the observed atomic hydrogen fraction. an enhanced spectrum of low-energy protons is needed to explain most of the observations.conclusions: our findings show that a careful description of molecular hydrogen dissociation by cosmic rays can explain the abundance of atomic hydrogen in dark clouds. an accurate characterisation of this process at high densities is crucial for understanding the chemical evolution of star-forming regions. | production of atomic hydrogen by cosmic rays in dark clouds |
for decades, the detection of phosphorus-bearing molecules in the interstellar medium was restricted to high-mass star-forming regions (e.g., sgrb2 and orion kl) and the circumstellar envelopes of evolved stars. however, recent higher-sensitivity observations have revealed that molecules such as pn and po are present not only toward cold massive cores and low-mass star-forming regions with po/pn ratios ≥1 but also toward the giant molecular clouds in the galactic center known to be exposed to highly energetic phenomena such as intense uv radiation fields, shock waves, and cosmic rays. in this paper, we carry out a comprehensive study of the chemistry of phosphorus-bearing molecules across different astrophysical environments that cover a range of physical conditions (cold molecular dark clouds, warm clouds, and hot cores/hot corinos) and are exposed to different physical processes and energetic phenomena (proto-stellar heating, shock waves, intense uv radiation, and cosmic rays). we show how the measured po/pn ratio (either ≥1, as in, e.g., hot molecular cores, or ≤1, as in uv strongly illuminated environments) can provide constraints on the physical conditions and energetic processing of the source. we propose that the reaction p + oh → po + h, not included in previous works, could be an efficient gas-phase po formation route in shocks. our modeling provides a template with which to study the detectability of p-bearing species not only in regions in our own galaxy but also in extragalactic sources. | the chemistry of phosphorus-bearing molecules under energetic phenomena |
cosmic filaments are the channel through which galaxy groups assemble their mass. cosmic connectivity, namely the number of filaments connected to a given group, is therefore expected to be an important ingredient in shaping group properties. the local connectivity is measured in cosmos around x-ray-detected groups between redshift 0.5 and 1.2. to this end, large-scale filaments are extracted using the accurate photometric redshifts of the cosmos2015 catalogue in two-dimensional slices of thickness 120 comoving mpc centred on the group's redshift. the link between connectivity, group mass, and the properties of the brightest group galaxy (bgg) is investigated. the same measurement is carried out on mocks extracted from the light-cone of the hydrodynamical simulation horizon-agn in order to control systematics. more massive groups are on average more connected. at fixed group mass in low-mass groups, bgg mass is slightly enhanced at high connectivity, while in high-mass groups bgg mass is lower at higher connectivity. groups with a star-forming bgg have on average a lower connectivity at given mass. from the analysis of the horizon-agn simulation, we postulate that different connectivities trace different paths of group mass assembly: at high group mass, groups with higher connectivity are more likely to have grown through a recent major merger, which might be in turn the reason for the quenching of the bgg. future large-field photometric surveys, such as euclid and lsst, will be able to confirm and extend these results by probing a wider mass range and a larger variety of environment. | group connectivity in cosmos: a tracer of mass assembly history |
the first measurement of the diffuse background spectrum at 0.8 - 1.7 μ m from the ciber experiment has revealed a significant excess of the cosmic infrared background (cib) radiation compared to the theoretically expected spectrum. we revisit the hypothesis that decays of axionlike particle (alp) can explain this excess, extending previous analyses to the case of a warm relic population. we show that such a scenario is not excluded by anisotropy measurements nor by stellar cooling arguments. moreover, we find that the increased extragalactic background light (ebl) does not contradict observations of blazar spectra. furthermore, the increased ebl attenuates the diffuse tev gamma-ray flux and alleviates the tension between the detected neutrino and gamma ray fluxes. | cosmic infrared background excess from axionlike particles and implications for multimessenger observations of blazars |
the icecube neutrino discovery was punctuated by three showers with eν≈1 - 2 pev . interest is intense in possible fluxes at higher energies, though a deficit of eν≈6 pev glashow resonance events implies a spectrum that is soft and/or cutoff below ∼few pev. however, icecube recently reported a through-going track depositing 2.6 ±0.3 pev . a muon depositing so much energy can imply eνμ≳10pev . alternatively, we find a tau can deposit this much energy, requiring eν τ∼10 × higher. we show that extending soft spectral fits from tev-pev data is unlikely to yield such an event, while an ∼eν-2 flux predicts excessive glashow events. these instead hint at a new flux, with the hierarchy of νμ and ντ energies implying astrophysical neutrinos at eν∼100 pev if a tau. we address implications for ultrahigh-energy cosmic-ray and neutrino origins. | multi-pev signals from a new astrophysical neutrino flux beyond the glashow resonance |
using a semianalytical approach based on the thin-shell approximation, we calculate the long-term evolution of supernova remnants (snrs) while also accounting for the cosmic rays (crs) accelerated at their blast waves. our solution reproduces the results of state-of-the-art fluid simulations across the adiabatic and radiative stages for the gas-only case, and it predicts that typical cr acceleration efficiencies (≈10 % ) can boost snr momentum deposition by a factor of 2-3. this enhancement can become as large as an order of magnitude in environments in which the gas experiences more severe radiative losses. this result may have a crucial impact on modeling the effect of supernova feedback on star formation and galaxy evolution. | effect of cosmic rays on the evolution and momentum deposition of supernova remnants |
to understand the conditions under which dense, molecular gas is able to form within a galaxy, we post-process a series of three-dimensional galactic-disc-scale simulations with ray-tracing-based radiative transfer and chemical network integration to compute the equilibrium chemical and thermal state of the gas. in performing these simulations, we vary a number of parameters, such as the interstellar radiation field strength, vertical scaleheight of stellar sources, and cosmic ray flux, to gauge the sensitivity of our results to these variations. self-shielding permits significant molecular hydrogen (h2) abundances in dense filaments around the disc mid-plane, accounting for approximately ∼10-15 per cent of the total gas mass. significant co fractions only form in the densest, nh≳ 10^3 cm^{-3}, gas where a combination of dust, h2, and self-shielding attenuates the far-ultraviolet background. we additionally compare these ray-tracing-based solutions to photochemistry with complementary models where photoshielding is accounted for with locally computed prescriptions. with some exceptions, these local models for the radiative shielding length perform reasonably well at reproducing the distribution and amount of molecular gas as compared with a detailed, global ray-tracing calculation. specifically, an approach based on the jeans length with a t = 40 k temperature cap performs the best in regard to a number of different quantitative measures based on the h2 and co abundances. | chemistry and radiative shielding in star-forming galactic discs |
the interaction properties of cold dark matter (cdm) particle candidates, such as those of weakly interacting massive particles (wimps), generically lead to the structuring of dark matter on scales much smaller than typical galaxies, potentially down to ∼10-10 m⊙ . this clustering translates into a very large population of subhalos in galaxies and affects the predictions for direct and indirect dark matter searches (gamma rays and antimatter cosmic rays). in this paper, we elaborate on previous analytic works to model the galactic subhalo population, while keeping consistent with current observational dynamical constraints on the milky way. in particular, we propose a self-consistent method to account for tidal effects induced by both dark matter and baryons. our model does not strongly rely on cosmological simulations, as they can hardly be fully matched to the real milky way, apart from setting the initial subhalo mass fraction. still, it allows us to recover the main qualitative features of simulated systems. it can further be easily adapted to any change in the dynamical constraints, and can be used to make predictions or derive constraints on dark matter candidates from indirect or direct searches. we compute the annihilation boost factor, including the subhalo-halo cross product. we confirm that tidal effects induced by the baryonic components of the galaxy play a very important role, resulting in a local average subhalo mass density ≲1 % of the total local dark matter mass density, while selecting the most concentrated objects and leading to interesting features in the overall annihilation profile in the case of a sharp subhalo mass function. values of global annihilation boost factors range from ∼2 to ∼20 , while the local annihilation rate is about boosted half as much. | modeling dark matter subhalos in a constrained galaxy: global mass and boosted annihilation profiles |
recently, the alice collaboration reported an enhancement of the yield ratio of strange and multi-strange hadrons to charged pions as a function of multiplicity at mid-rapidity in proton-proton, proton-lead, lead-lead, and xenon-xenon scattering. alice observations provide a strong indication that a quark-gluon plasma is partly formed in high multiplicity events of both small and large colliding systems. motivated by alice's results, we propose a new test for hadronic interaction models used for analyzing ultra-high-energy-cosmic-ray (uhecr) collisions with air nuclei. the test is grounded in the almost equal column-energy density in uhecr-air collisions and lead-lead collisions at the lhc. we applied the test to post-lhc event generators describing hadronic phenomena of uhecr scattering and show that these qcd monte carlo-based codes must be retuned to accommodate the strangeness enhancement relative to pions observed in lhc data. | through the looking-glass with alice into the quark-gluon plasma: a new test for hadronic interaction models used in air shower simulations |
the advanced ligo gravitational wave detectors are second-generation instruments designed and built for the two ligo observatories in hanford, wa and livingston, la, usa. the two instruments are identical in design, and are specialized versions of a michelson interferometer with 4 km long arms. as in initial ligo, fabry-perot cavities are used in the arms to increase the interaction time with a gravitational wave, and power recycling is used to increase the effective laser power. signal recycling has been added in advanced ligo to improve the frequency response. in the most sensitive frequency region around 100 hz, the design strain sensitivity is a factor of 10 better than initial ligo. in addition, the low frequency end of the sensitivity band is moved from 40 hz down to 10 hz. all interferometer components have been replaced with improved technologies to achieve this sensitivity gain. much better seismic isolation and test mass suspensions are responsible for the gains at lower frequencies. higher laser power, larger test masses and improved mirror coatings lead to the improved sensitivity at mid and high frequencies. data collecting runs with these new instruments are planned to begin in mid-2015. | advanced ligo |
this horizon study describes a next-generation ground-based gravitational-wave observatory: cosmic explorer. with ten times the sensitivity of advanced ligo, cosmic explorer will push gravitational-wave astronomy towards the edge of the observable universe ($z \sim 100$). the goals of this horizon study are to describe and evaluate design concepts for cosmic explorer; to plan for the united states' leadership in gravitational-wave astronomy; and to envisage the role of cosmic explorer in the international effort to build a "third-generation" (3g) observatory network that will make discoveries transformative across astronomy, physics, and cosmology. | a horizon study for cosmic explorer: science, observatories, and community |
on 2017 august 17 at 12:41:06 utc the fermi gamma-ray burst monitor (gbm) detected and triggered on the short gamma-ray burst (grb) 170817a. approximately 1.7 s prior to this grb, the laser interferometer gravitational-wave observatory triggered on a binary compact merger candidate associated with the grb. this is the first unambiguous coincident observation of gravitational waves and electromagnetic radiation from a single astrophysical source and marks the start of gravitational-wave multi-messenger astronomy. we report the gbm observations and analysis of this ordinary short grb, which extraordinarily confirms that at least some short grbs are produced by binary compact mergers. | an ordinary short gamma-ray burst with extraordinary implications: fermi-gbm detection of grb 170817a |
the modern-era retrospective analysis for research and applications-2 (merra2) version of the goddard earth observing system-5 (geos-5) atmospheric general circulation model (agcm) is currently in use in the nasa global modeling and assimilation office (gmao) at a wide range of resolutions for a variety of applications. details of the changes in parameterizations subsequent to the version in the original merra reanalysis are presented here. results of a series of atmosphere-only sensitivity studies are shown to demonstrate changes in simulated climate associated with specific changes in physical parameterizations, and the impact of the newly implemented resolution-aware behavior on simulations at different resolutions is demonstrated. the geos-5 agcm presented here is the model used as part of the gmao merra2 reanalysis, global mesoscale simulations at 10 km resolution through 1.5 km resolution, the real-time numerical weather prediction system, and for atmosphere-only, coupled ocean-atmosphere and coupled atmosphere-chemistry simulations.the seasonal mean climate of the merra2 version of the geos-5 agcm represents a substantial improvement over the simulated climate of the merra version at all resolutions and for all applications. fundamental improvements in simulated climate are associated with the increased re-evaporation of frozen precipitation and cloud condensate, resulting in a wetter atmosphere. improvements in simulated climate are also shown to be attributable to changes in the background gravity wave drag, and to upgrades in the relationship between the ocean surface stress and the ocean roughness. the series of resolution-aware parameters related to the moist physics was shown to result in improvements at higher resolutions and result in agcm simulations that exhibit seamless behavior across different resolutions and applications. | development of the geos-5 atmospheric general circulation model: evolution from merra to merra2 |
we lay out a comprehensive physics case for a future high-energy muon collider, exploring a range of collision energies (from 1 to 100 tev) and luminosities. we highlight the advantages of such a collider over proposed alternatives. we show how one can leverage both the point-like nature of the muons themselves as well as the cloud of electroweak radiation that surrounds the beam to blur the dichotomy between energy and precision in the search for new physics. the physics case is buttressed by a range of studies with applications to electroweak symmetry breaking, dark matter, and the naturalness of the weak scale. furthermore, we make sharp connections with complementary experiments that are probing new physics effects using electric dipole moments, flavor violation, and gravitational waves. an extensive appendix provides cross section predictions as a function of the center-of-mass energy for many canonical simplified models. | the muon smasher's guide |
understanding gravity in the framework of quantum mechanics is one of the great challenges in modern physics. however, the lack of empirical evidence has lead to a debate on whether gravity is a quantum entity. despite varied proposed probes for quantum gravity, it is fair to say that there are no feasible ideas yet to test its quantum coherent behavior directly in a laboratory experiment. here, we introduce an idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator. we show that despite the weakness of gravity, the phase evolution induced by the gravitational interaction of two micron size test masses in adjacent matter-wave interferometers can detectably entangle them even when they are placed far apart enough to keep casimir-polder forces at bay. we provide a prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, through simple spin correlation measurements. | spin entanglement witness for quantum gravity |
this thesis covers a diverse set of topics related to space-based gravitational wave detectors such as the laser interferometer space antenna (lisa). the core of the thesis is devoted to the preprocessing of the interferometric link data for a lisa constellation, specifically developing optimal kalman filters to reduce arm length noise due to clock noise. the approach is to apply kalman filters of increasing complexity to make optimal estimates of relevant quantities such as constellation arm length, relative clock drift, and doppler frequencies based on the available measurement data. depending on the complexity of the filter and the simulated data, these kalman filter estimates can provide up to a few orders of magnitude improvement over simpler estimators. while the basic concept of the lisa measurement (time delay interferometry) was worked out some time ago, this work brings a level of rigor to the processing of the constellation-level data products. the thesis concludes with some topics related to the elisa such as a new class of phenomenological waveforms for extreme mass-ratio inspiral sources (emris, one of the main source for elisa), an octahedral space-based gw detector that does not require drag-free test masses, and some efficient template-search algorithms for the case of relatively high snr signals. | first-stage lisa data processing and gravitational wave data analysis: ultraprecise inter-satellite laser ranging, clock synchronization and novel gravitational wave data analysis algorithms |
tjonnie li's thesis covers two applications of gravitational wave astronomy: tests of general relativity in the strong-field regime and cosmological measurements. the first part of the thesis focuses on the so-called tiger, i.e. test infrastructure for general relativity, an innovative bayesian framework for performing hypothesis tests of modified gravity using ground-based gw data. after developing the framework, li simulates a variety of general relativity deviations and demonstrates the ability of the aforementioned tiger to measure them. the advantages of the method are nicely shown and compared to other, less generic methods. given the extraordinary implications that would result from any measured deviation from general relativity, it is extremely important that a rigorous statistical approach for supporting these results would be in place before the first gravitational wave detections begin. in developing tiger, tjonnie li shows a large amount of creativity and originality, and his contribution is an important step in the direction of a possible discovery of a deviation (if any) from general relativity. in another section, li's thesis deals with cosmology, describing an exploratory study where the possibility of cosmological parameters measurement through gravitational wave compact binary coalescence signals associated with electromagnetic counterparts is evaluated. in particular, the study explores the capabilities of the future einstein telescope observatory. although of very long term-only applicability, this is again a thorough investigation, nicely put in the context of the current and the future observational cosmology. the author is the winner of the 2013 stefano braccini thesis prize awarded by the gravitational wave international committee. | extracting physics from gravitational waves: testing the strong-field dynamics of general relativity and inferring the large-scale structure of the universe |
in this work, we established a novel theory for the dynamics of oscillating bubbles such as cavitation bubbles, underwater explosion bubbles, and air bubbles. for the first time, we proposed bubble dynamics equations that can simultaneously take into consideration the effects of boundaries, bubble interaction, ambient flow field, gravity, bubble migration, fluid compressibility, viscosity, and surface tension while maintaining a unified and elegant mathematical form. the present theory unifies different classical bubble equations such as the rayleigh-plesset equation, the gilmore equation, and the keller-miksis equation. furthermore, we validated the theory with experimental data of bubbles with a variety in scales, sources, boundaries, and ambient conditions and showed the advantages of our theory over the classical theoretical models, followed by a discussion on the applicability of the present theory based on a comparison to simulation results with different numerical methods. finally, as a demonstration of the potential of our theory, we modeled the complex multi-cycle bubble interaction with wide ranges of energy and phase differences and gained new physical insight into inter-bubble energy transfer and coupling of bubble-induced pressure waves. | a unified theory for bubble dynamics |
we consider higher derivative corrections to the graviton three-point coupling within a weakly coupled theory of gravity. lorentz invariance allows further structures beyond the one present in the einstein theory. we argue that these are constrained by causality. we devise a thought experiment involving a high energy scattering process which leads to causality violation if the graviton three-point vertex contains the additional structures. this violation cannot be fixed by adding conventional particles with spins j ≤ 2. but, it can be fixed by adding an infinite tower of extra massive particles with higher spins, j > 2. in ads theories this implies a constraint on the conformal anomaly coefficients |a-c/c|≲ 1/δ_{gap^2} n terms of δgap, the dimension of the lightest single trace operator with spin j > 2. for inflation, or de sitter-like solutions, it indicates the existence of massive higher spin particles if the gravity wave non-gaussianity deviates significantly from the one computed in the einstein theory. | causality constraints on corrections to the graviton three-point coupling |
tianqin is a proposal for a space-borne detector of gravitational waves in the millihertz frequencies. the experiment relies on a constellation of three drag-free spacecraft orbiting the earth. inter-spacecraft laser interferometry is used to monitor the distances between the test masses. the experiment is designed to be capable of detecting a signal with high confidence from a single source of gravitational waves within a few months of observing time. we describe the preliminary mission concept for tianqin, including the candidate source and experimental designs. we present estimates for the major constituents of the experiment’s error budget and discuss the project’s overall feasibility. given the current level of technological readiness, we expect tianqin to be flown in the second half of the next decade. | tianqin: a space-borne gravitational wave detector |
squeezed states of light belong to the most prominent nonclassical resources. they have compelling applications in metrology, which has been demonstrated by their routine exploitation for improving the sensitivity of a gravitational-wave detector since 2010. here, we report on the direct measurement of 15 db squeezed vacuum states of light and their application to calibrate the quantum efficiency of photoelectric detection. the object of calibration is a customized ingaas positive intrinsic negative (p-i-n) photodiode optimized for high external quantum efficiency. the calibration yields a value of 99.5% with a 0.5% (k =2 ) uncertainty for a photon flux of the order 1 017 s-1 at a wavelength of 1064 nm. the calibration neither requires any standard nor knowledge of the incident light power and thus represents a valuable application of squeezed states of light in quantum metrology. | detection of 15 db squeezed states of light and their application for the absolute calibration of photoelectric quantum efficiency |
the stochastic gravitational-wave background is a superposition of sources that are either too weak or too numerous to detect individually. in this study, we present the results from a cross-correlation analysis on data from advanced ligo's second observing run (o2), which we combine with the results of the first observing run (o1). we do not find evidence for a stochastic background, so we place upper limits on the normalized energy density in gravitational waves at the 95% credible level of ωgw<6.0 ×10-8 for a frequency-independent (flat) background and ωgw<4.8 ×10-8 at 25 hz for a background of compact binary coalescences. the upper limit improves over the o1 result by a factor of 2.8. additionally, we place upper limits on the energy density in an isotropic background of scalar- and vector-polarized gravitational waves, and we discuss the implication of these results for models of compact binaries and cosmic string backgrounds. finally, we present a conservative estimate of the correlated broadband noise due to the magnetic schumann resonances in o2, based on magnetometer measurements at both the ligo hanford and ligo livingston observatories. we find that correlated noise is well below the o2 sensitivity. | search for the isotropic stochastic background using data from advanced ligo's second observing run |
advanced ligo and advanced virgo are monitoring the sky and collecting gravitational-wave strain data with sufficient sensitivity to detect signals routinely. in this paper we describe the data recorded by these instruments during their first and second observing runs. the main data products are gravitational-wave strain time series sampled at 16384 hz. the datasets that include this strain measurement can be freely accessed through the gravitational wave open science center at http://gw-openscience.org, together with data-quality information essential for the analysis of ligo and virgo data, documentation, tutorials, and supporting software. | open data from the first and second observing runs of advanced ligo and advanced virgo |
the atmosphere and ocean are two of the most important components of the climate system, and fluid dynamics is central to our understanding of both. this book provides a unified and comprehensive treatment of the field that blends classical results with modern interpretations. it takes the reader seamlessly from the basics to the frontiers of knowledge, from the equations of motion to modern theories of the general circulation of the atmosphere and ocean. these concepts are illustrated throughout the book with observations and numerical examples. as well as updating existing chapters, this full-color second edition includes new chapters on tropical dynamics, el niño, the stratosphere and gravity waves. supplementary resources are provided online, including figures from the book and problem sets, making this new edition an ideal resource for students in the atmospheric, oceanic and climate sciences, as well as in applied mathematics and engineering. | atmospheric and oceanic fluid dynamics: fundamentals and large-scale circulation |
the european centre for medium-range weather forecasts' (ecmwf's) next-generation reanalysis era5 provides many improvements, but it also confronts the community with a "big data" challenge. data storage requirements for era5 increase by a factor of ∼80 compared with the era-interim reanalysis, introduced a decade ago. considering the significant increase in resources required for working with the new era5 data set, it is important to assess its impact on lagrangian transport simulations. to quantify the differences between transport simulations using era5 and era-interim data, we analyzed comprehensive global sets of 10-day forward trajectories for the free troposphere and the stratosphere for the year 2017. the new era5 data have a considerable impact on the simulations. spatial transport deviations between era5 and era-interim trajectories are up to an order of magnitude larger than those caused by parameterized diffusion and subgrid-scale wind fluctuations after 1 day and still up to a factor of 2-3 larger after 10 days. depending on the height range, the spatial differences between the trajectories map into deviations as large as 3 k in temperature, 30 % in specific humidity, 1.8 % in potential temperature, and 50 % in potential vorticity after 1 day. part of the differences between era5 and era-interim is attributed to the better spatial and temporal resolution of the era5 reanalysis, which allows for a better representation of convective updrafts, gravity waves, tropical cyclones, and other meso- to synoptic-scale features of the atmosphere. another important finding is that era5 trajectories exhibit significantly improved conservation of potential temperature in the stratosphere, pointing to an improved consistency of ecmwf's forecast model and observations that leads to smaller data assimilation increments. we conducted a number of downsampling experiments with the era5 data, in which we reduced the numbers of meteorological time steps, vertical levels, and horizontal grid points. significant differences remain present in the transport simulations, if we downsample the era5 data to a resolution similar to era-interim. this points to substantial changes of the forecast model, observations, and assimilation system of era5 in addition to improved resolution. a comparison of two lagrangian trajectory models allowed us to assess the readiness of the codes and workflows to handle the comprehensive era5 data and to demonstrate the consistency of the simulation results. our results will help to guide future lagrangian transport studies attempting to navigate the increased computational complexity and leverage the considerable benefits and improvements of ecmwf's new era5 data set. | from era-interim to era5: the considerable impact of ecmwf's next-generation reanalysis on lagrangian transport simulations |
we show how to compute classical wave observables using quantum scattering amplitudes. we discuss observables both with incoming and with outgoing waves. the required classical limits are naturally described by coherent states of massless bosons. we recompute the classic gravitational deflection of light, and also show how to rederive thomson scattering. we introduce a new class of local observables, which includes the asymptotic electromagnetic and gravitational newman-penrose scalars. as an example, we compute a simple radiated waveform: the expectation of the electromagnetic field in charged-particle scattering. at leading order, the waveform is trivially related to the five-point scattering amplitude. | waveforms from amplitudes |
we report the first results of the lisa pathfinder in-flight experiment. the results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like lisa, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2 ±0.1 fm s-2/√{hz } , or (0.54 ±0.01 ) ×10-15 g/√{hz } , with g the standard gravity, for frequencies between 0.7 and 20 mhz. this value is lower than the lisa pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the lisa mission, and is compatible with brownian noise from viscous damping due to the residual gas surrounding the test masses. above 60 mhz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8 ±0.3 ) fm /√{hz } , about 2 orders of magnitude better than requirements. at f ≤0.5 mhz we observe a low-frequency tail that stays below 12 fm s-2/√{hz } down to 0.1 mhz. this performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for lisa. | sub-femto-g free fall for space-based gravitational wave observatories: lisa pathfinder results |
in this report we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de sitter (ads) space, and conformal quantum mechanics. this approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in qcd in the limit of massless quarks. the result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in ads space. this equation allows for the computation of essential features of hadron spectra in terms of a single scale. the light-front holographic methods described here give a precise interpretation of holographic variables and quantities in ads space in terms of light-front variables and quantum numbers. this leads to a relation between the ads wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound-states in physical space-time. the pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear regge trajectories with identical slopes in the radial and orbital quantum numbers. in the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. at large q2 the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. at low q2 the form factor leads to vector dominance. the approach is also extended to include small quark masses. we briefly review in this report other holographic approaches to qcd, in particular top-down and bottom-up models based on chiral symmetry breaking. we also include a discussion of open problems and future applications. | light-front holographic qcd and emerging confinement |
the laser interferometer space antenna (lisa) will open the mhz band of the gravitational wave spectrum for exploration. sensitivity curves are a useful tool for surveying the types of sources that can be detected by the lisa mission. here we describe how the sensitivity curve is constructed, and how it can be used to compute the signal-to-noise ratio for a wide range of binary systems. we adopt the 2018 lisa mission performance requirement design parameters. we consider both sky-averaged sensitivities, and the sensitivity to sources at particular sky locations. the calculations are included in a publicly available python notebook. | the construction and use of lisa sensitivity curves |
kagra is a newly built gravitational-wave telescope, a laser interferometer comprising arms with a length of 3 km, located in kamioka, gifu, japan. kagra was constructed under the ground and it is operated using cryogenic mirrors that help in reducing the seismic and thermal noise. both technologies are expected to provide directions for the future of gravitational-wave telescopes. in 2019, kagra finished all installations with the designed configuration, which we call the baseline kagra. for this occasion, we present an overview of the baseline kagra from various viewpoints in a series of articles. in this article, we introduce the design configurations of kagra with its historical background. | overview of kagra: detector design and construction history |
the january 2022 hunga tonga-hunga ha'apai eruption was one of the most explosive volcanic events of the modern era1,2, producing a vertical plume that peaked more than 50 km above the earth3. the initial explosion and subsequent plume triggered atmospheric waves that propagated around the world multiple times4. a global-scale wave response of this magnitude from a single source has not previously been observed. here we show the details of this response, using a comprehensive set of satellite and ground-based observations to quantify it from surface to ionosphere. a broad spectrum of waves was triggered by the initial explosion, including lamb waves5,6 propagating at phase speeds of 318.2 ± 6 m s−1 at surface level and between 308 ± 5 to 319 ± 4 m s−1 in the stratosphere, and gravity waves7 propagating at 238 ± 3 to 269 ± 3 m s−1 in the stratosphere. gravity waves at sub-ionospheric heights have not previously been observed propagating at this speed or over the whole earth from a single source8,9. latent heat release from the plume remained the most significant individual gravity wave source worldwide for more than 12 h, producing circular wavefronts visible across the pacific basin in satellite observations. a single source dominating such a large region is also unique in the observational record. the hunga tonga eruption represents a key natural experiment in how the atmosphere responds to a sudden point-source-driven state change, which will be of use for improving weather and climate models. | surface-to-space atmospheric waves from hunga tonga-hunga ha'apai eruption |
we obtain the total impulse in the scattering of nonspinning binaries in general relativity at fourth post-minkowskian order, i.e., o (g4), including linear, nonlinear, and hereditary radiation-reaction effects. we derive the total radiated spacetime momentum as well as the associated energy flux. the latter can be used to compute gravitational-wave observables for generic (un)bound orbits. we employ the ("in-in") schwinger-keldysh worldline effective field theory framework in combination with modern "multiloop" integration techniques from collider physics. the complete results are in agreement with various partial calculations in the post-minkowskian and post-newtonian expansion. | radiation reaction and gravitational waves at fourth post-minkowskian order |
controlling a quantum system by using observations of its dynamics is complicated by the backaction of the measurement process—that is, the unavoidable quantum disturbance caused by coupling the system to a measurement apparatus. an efficient measurement is one that maximizes the amount of information gained per disturbance incurred. real-time feedback can then be used to cancel the backaction of the measurement and to control the evolution of the quantum state. such measurement-based quantum control has been demonstrated in the clean settings of cavity and circuit quantum electrodynamics, but its application to motional degrees of freedom has remained elusive. here we demonstrate measurement-based quantum control of the motion of a millimetre-sized membrane resonator. an optomechanical transducer resolves the zero-point motion of the resonator in a fraction of its millisecond-scale coherence time, with an overall measurement efficiency close to unity. an electronic feedback loop converts this position record to a force that cools the resonator mode to its quantum ground state (residual thermal occupation of about 0.29). this occupation is nine decibels below the quantum-backaction limit of sideband cooling and six orders of magnitude below the equilibrium occupation of the thermal environment. we thus realize a long-standing goal in the field, adding position and momentum to the degrees of freedom that are amenable to measurement-based quantum control, with potential applications in quantum information processing and gravitational-wave detectors. | measurement-based quantum control of mechanical motion |
in 2009-2010, the laser interferometer gravitational-wave observatory (ligo) operated together with international partners virgo and geo600 as a network to search for gravitational waves (gws) of astrophysical origin. the sensitivity of these detectors was limited by a combination of noise sources inherent to the instrumental design and its environment, often localized in time or frequency, that couple into the gw readout. here we review the performance of the ligo instruments during this epoch, the work done to characterize the detectors and their data, and the effect that transient and continuous noise artefacts have on the sensitivity of ligo to a variety of astrophysical sources. | characterization of the ligo detectors during their sixth science run |
discrete r symmetries always play an important role in low energy susy. the spontaneously broken of such discrete r symmetries, for example, by gaugino condensation, can lead to domain walls, which need to be either inflated away or collapse to avoid cosmic difficulties. we propose that explicitly r symmetry violation needed for collapse of domain walls can be the consequence of multiple sector susy breaking. the consistency constraints for the generation of non-problematic domain walls from gaugino condensation are discussed. we also study the emitted gravitational waves related to the collapse of domain walls. we find that, for susy breaking scale of order ${\cal o}(1)$ ${\rm gev}$ in one of the sequestered sector (and also a low reheating temperature of order ${\rm mev}$ if the reheating is not completed when the domain walls collapse), the peak frequency of gravitational waves emitted can lie at nhz. such a low susy breaking scale can be consistency and natural in multiple sector susy breaking scenario. the gws signal by nanograv could be a signal of such multiple sector susy breaking scenario and it may also indicate the existences of light goldstini at ${\rm ev}$ mass scale. | did the nhz gravitational waves signatures observed by nanograv indicate multiple sector susy breaking? |
this white paper describes the research and development needed over the next decade to realize “cosmic explorer,” the u.s. node of a future third-generation detector network that will be capable of observing and characterizing compact gravitational-wave sources to cosmological redshifts. | cosmic explorer: the u.s. contribution to gravitational-wave astronomy beyond ligo |
we demonstrate unprecedented accuracy for rapid gravitational wave parameter estimation with deep learning. using neural networks as surrogates for bayesian posterior distributions, we analyze eight gravitational wave events from the first ligo-virgo gravitational-wave transient catalog and find very close quantitative agreement with standard inference codes, but with inference times reduced from o (day ) to 20 s per event. our networks are trained using simulated data, including an estimate of the detector noise characteristics near the event. this encodes the signal and noise models within millions of neural-network parameters and enables inference for any observed data consistent with the training distribution, accounting for noise nonstationarity from event to event. our algorithm—called "dingo"—sets a new standard in fast and accurate inference of physical parameters of detected gravitational wave events, which should enable real-time data analysis without sacrificing accuracy. | real-time gravitational wave science with neural posterior estimation |
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