Autonomous radio-detection, i.e., detection of air-showers with standalone radio arrays, is one of the major technical challenges to overcome for the next generation astroparticle detectors. In this ...context, we study polarisation signatures of simulated radio signals to perform an identification of the associated air-showers initiated by cosmic-rays and neutrinos. We compare the two sources of radio emission (the charge excess and geomagnetic) and show that the former is almost negligible for inclined (zenith angle >65°) cosmic-ray air-showers. This provides an efficient background rejection criterion at the DAQ level, based on the projection of the total electric field along the direction of the local magnetic field. This relevant quantity can be computed, — even in an online treatment — for antennas measuring three orthogonal polarisations. Independently of the experimental antenna layout, we estimate that assuming a random polarisation of noise events, a rejection from ≈72% (for a non favourable detector location) to ≈93% (for a favourable one) of the noise induced events and a trigger efficiency of 86% (93%) with a 3σ (5σ) trigger threshold level should be achievable. We also show that neutrino-induced showers present a charge excess to geomagnetic signal ratio up to ∼10 times higher than for cosmic ray showers. Although this characteristic makes the identification of neutrino-induced showers challenging via the method developed here, it provides an efficient criterion to perform an offline discrimination between cosmic-ray and neutrino primaries. The stronger charge excess emission will also help the reconstruction of air-shower parameters, such as the core position.
Radio-detection is a mature technique that has gained large momentum over the past decades. Its physical detection principle is mainly driven by the electromagnetic part of the shower, and is ...therefore not too sensitive to uncertainties on hadronic interactions. Furthermore its technical detection principle allows for a 100% duty cycle, and large surface coverage thanks to the low cost of antennas. Various detection methods of UHE particles now rely on the radio signal as main observable. For instance, ground based experiments such as AERA on the Pierre Auger Observatory or LOFAR detect the radio emission from air-showers induced by high-energy particles in the atmosphere; in-ice experiment such as ARA, IceCube, or ARIANNA benefits from a detection in denser media which reduces the interaction lengths; finally, balloon experiments such as ANITA allow for very sensitive UHE neutrino detection with only a few antennas. Radio-detection is now focused on building increasingly large-scale radio experiments to enhance the detector sensitivity and address the low fluxes at UHE. In this proceeding we give an overview of the past, current and future experiments for the detection of UHE cosmic particles using the radio technique in air (AERA, Auger-Prime, GRAND), in balloon (ANITA, PUEO) or in other media (IceCube-Gen2, BEACON, RNO-G).
The reconstruction of very inclined air showers is a new challenge for next-generation radio experiments such as the AugerPrime radio upgrade, BEACON, and GRAND, which focus on the detection of ...ultra-high-energy particles. To tackle this, we study the electromagnetic particle content of very inclined air showers, which has scarcely been studied so far. Using the simulation tools CORSIKA and CoREAS, and analytical modeling, we explore the energy range of the particles that contribute most to the radio emission, quantify their lateral extent, and estimate the atmospheric depth at which the radio emission is strongest. We find that the distribution of the electromagnetic component in very inclined air showers has characteristic features that could lead to clear signatures in the radio signal, and hence impact the reconstruction strategies of next-generation radio-detection experiments.
Next-generation radio experiments such as the Radio Detector of the upgraded Pierre Auger Observatory and the planned GRAND and BEACON arrays target the detection of ultra-high-energy particle air ...showers arriving at low elevation angles. These inclined cosmic-ray air showers develop higher in the atmosphere than vertical ones, enhancing magnetic deflections of electrons and positrons inside the cascade. We evidence two novel features in their radio emission: a new polarization pattern, consistent with a geo-synchrotron emission model and a coherence loss of the radio emission, both for showers with zenith angle \(\theta \gtrsim 65^{\circ}\) and strong enough magnetic field amplitude (typical strength of \(B\sim 50\, \rm \mu T\)). Our model is compared with both ZHAireS and CoREAS Monte-Carlo simulations. Our results break the cannonical description of a radio signal made of Askaryan and transverse current emission only, and provide guidelines for the detection and reconstruction strategies of next-generation experiments, including cosmic-ray/neutrino discrimination.
Very inclined extensive air showers (EAS), with both down-going and up-going trajectories, are particularly targeted by the next generation of extended radio arrays, such as GRAND. Methods to ...reconstruct the incoming direction, core position, primary energy and composition of showers with these specific geometries, remain to be developed. Towards that goal, we present a new reconstruction procedure based on the arrival times and the amplitudes of the radio signal, measured at each antenna station. This hybrid reconstruction method, harnesses the fact that the emission is observed, at the antenna level, far away from the emission region, thus allowing for a point-like emission description. Thanks to this assumption, the arrival times are modelled following a spherical wavefront emission, which offers the possibility to reconstruct the radio emission zone as a fixed point along the shower axis. From that point the amplitude distribution at the antenna level is described through an Angular Distribution Function (ADF) taking into account at once all geo-magnetic asymmetries and early late effects as well as additional signal asymmetries featured by very inclined EAS. This method shows promising results in terms of arrival direction reconstruction, within the 0.1{\deg} range, even when taking into account experimental uncertainties, and interesting potential for the energy reconstruction and primary composition identification.
Autonomous radio-detection, i.e., detection of air-showers with standalone radio arrays, is one of the major technical challenges to overcome for the next generation astroparticle detectors. In this ...context, we study polarisation signatures of simulated radio signals to perform an identification of the associated air-showers initiated by cosmic-rays and neutrinos. We compare the two sources of radio emission (the charge excess and geomagnetic) and show that the former is almost negligible for inclined (zenith angle \(>65^{\circ}\)) cosmic-ray air-showers. This provides an efficient background rejection criterion at the DAQ level, based on the projection of the total electric field along the direction of the local magnetic field. This relevant quantity can be easily computed -- even in an online treatment -- for antennas measuring three orthogonal polarisations. Independently of the experimental antenna layout, we estimate that assuming a random polarisation of noise events, a rejection from \(\approx 72\%\) (for a non favorable detector location) to \(\approx 93\%\) (for a favorable location) of the noise induced events and a trigger efficiency of 87% (93%) with a \(3\sigma\) (\(5\sigma\)) trigger threshold level should be achievable. We also show that neutrino-induced showers present a charge excess to geomagnetic signal ratio up to \(\sim 10\) times higher than for cosmic ray showers. Although this characteristic makes the identification of neutrino-induced showers challenging via the method developed here, it provides an efficient criterion to perform an offline discrimination between cosmic-ray and neutrino primaries. The stronger charge excess emission will also help the reconstruction of air-shower parameters, such as the core position.
Galaxies in clusters undergo several phenomena such as ram pressure stripping and tidal interactions, that can trigger or quench their star formation and, in some cases, lead to galaxies acquiring ...unusual shapes and long tails. We searched for jellyfish galaxy candidates in a sample of 40 clusters from the DAFT/FADA and CLASH surveys covering the redshift range 0.2<z<0.9. In MACS J0717.5+3745 (MACS0717), our large spatial coverage and abundant sampling of spectroscopic redshifts allowed us to pursue a detailed analysis of jellyfish galaxy candidates in this cluster and its extended filament. We looked at the Hubble Space Telescope images of all the cluster galaxies (based on redshifts), and classified them as a function of their likeliness to be jellyfish galaxies, and give catalogues of jellyfish candidates with positions, redshifts, magnitudes, and projected distance to the respective cluster centre. We found 81 jellyfish candidates in the extended region around MACS0717, and 97 in 22 other clusters. Jellyfish galaxy candidates in MACS0717 tend to avoid the densest regions of the cluster, while this does not appear to be the case in the other clusters. For 79 galaxies in MACS0717 and 31 in other clusters, we computed the best stellar population fits with LePhare through the GAZPAR interface. We find that jellyfish candidates tend to be star forming objects, with blue colours, young ages, high star formation rates and specific star formation rates. In a SFR versus stellar mass diagram, jellyfish galaxy candidates appear to have somewhat larger SFRs than non-jellyfish star forming galaxies Based on several arguments, the jellyfish candidates identified in MACS0717 seem to have fallen rather recently into the cluster. A very rough estimate of the proportions of jellyfish galaxies in the studied clusters is about 10%.
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