Publications by Rafael Alves Batista


The Giant Radio Array for Neutrino Detection (GRAND): Science and design

Science China: Physics, Mechanics and Astronomy 63 (2020)

J Álvarez-Muñiz, R Alves Batista, A Balagopal V, J Bolmont, M Bustamante, W Carvalho, D Charrier, I Cognard, V Decoene, PB Denton, S De Jong, KD De Vries, R Engel, K Fang, C Finley, S Gabici, QB Gou, JH Gu, C Guépin, HB Hu, Y Huang, K Kotera, S Le Coz, JP Lenain, GL Lü, O Martineau-Huynh, M Mostafá, F Mottez, K Murase, V Niess, F Oikonomou, T Pierog, XL Qian, B Qin, D Ran, N Renault-Tinacci, M Roth, FG Schröder, F Schüssler, C Tasse, C Timmermans, M Tueros, XP Wu, P Zarka, A Zech, BT Zhang, JL Zhang, Y Zhang, Q Zheng, A Zilles

© 2019, Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature. The Giant Radio Array for Neutrino Detection (GRAND) is a planned large-scale observatory of ultra-high-energy (UHE) cosmic particles, with energies exceeding 108 GeV. Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays. To do this, GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity. GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere. Its design is modular: 20 separate, independent sub-arrays, each of 10000 radio antennas deployed over 10000 km2. A staged construction plan will validate key detection techniques while achieving important science goals early. Here we present the science goals, detection strategy, preliminary design, performance goals, and construction plans for GRAND.


Numerical models of neutrino and gamma-ray emission from magnetic reconnection in the core of radio-galaxies

Proceedings of Science 329 (2018)

JC Rodríguez-Ramírez, EM de Gouveia Dal Pino, R Alves Batista

© Copyright owned by the author(s) under the terms of the Creative Commons. Non-blazar radio-galaxies emitting in the very-high-energy (VHE; >100 GeV) regime offer a unique perspective for probing particle acceleration and emission processes in black hole (BH) accretion-jet systems. The misaligned nature of these sources indicates the presence of an emission component that could be of hadronic origin and located in the core region. Here we consider turbulent magnetic reconnection in the BH accretion flow of radio-galaxies as a potential mechanism for cosmic-ray (CR) acceleration and VHE emission. To investigate if this scenario is able to account for the observed VHE data, we combine three numerical techniques to self-consistently model the accretion flow environment and the propagation of CRs plus electromagnetic cascades within the accretion flow zone. Here we apply our approach to the radio-galaxy Centaurus A and find that injection of CRs consistent with magnetic reconnection power partially reproduce the VHE data, provided that the accretion flow makes no substantial contribution to the radio-GeV components. The associated neutrino emission peaks at ∼ 1016 eV and is two orders of magnitude below the minimum IceCube flux.


Secondary neutrino and gamma-ray fluxes from SimProp and CRPropa

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS (2019) ARTN 006

RA Batista, D Boncioli, A di Matteo, A van Vliet


Determining the fraction of cosmic-ray protons at ultrahigh energies with cosmogenic neutrinos

PHYSICAL REVIEW D 100 (2019) ARTN 021302

A van Vliet, RA Batist, JR Horandel


Monte Carlo studies for the optimisation of the Cherenkov Telescope Array layout

Astroparticle Physics Elsevier 111 (2019) 35-53

A Acharyya, I Agudo, EO Angüner, R Alfaro, J Alfaro, C Alispach, R Aloisio, R Alves Batista, JP Amans, L Amati, E Amato, G Ambrosi, LA Antonelli, C Aramo, T Armstrong, F Arqueros, L Arrabito, K Asano, H Ashkar, C Balazs, M Balbo, B Balmaverde, P Barai, A Barbano, M Barkov

The Cherenkov Telescope Array (CTA) is the major next-generation observatory for ground-based very-high-energy gamma-ray astronomy. It will improve the sensitivity of current ground-based instruments by a factor of five to twenty, depending on the energy, greatly improving both their angular and energy resolutions over four decades in energy (from 20 GeV to 300 TeV). This achievement will be possible by using tens of imaging Cherenkov telescopes of three successive sizes. They will be arranged into two arrays, one per hemisphere, located on the La Palma island (Spain) and in Paranal (Chile). We present here the optimised and final telescope arrays for both CTA sites, as well as their foreseen performance, resulting from the analysis of three different large-scale Monte Carlo productions.


Cosmogenic photon and neutrino fluxes in the Auger era

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS (2019) ARTN 002

RA Batista, RM de Almeida, B Lago, K Kotera


On the measurement of the helicity of intergalactic magnetic fields using ultra-high-energy cosmic rays

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS (2019) ARTN 011

RA Batista, A Saveliev


Very-high-energy Emission from Magnetic Reconnection in the Radiative-inefficient Accretion Flow of SgrA*

ASTROPHYSICAL JOURNAL 879 (2019) ARTN 6

JC Rodriguez-Ramirez, EM de Gouveia Dal Pino, RA Batista


The impact of plasma instabilities on the spectra of TeV blazars

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 489 (2019) 3836-3849

RA Batista, A Saveliev, EM de Gouveia Dal Pino


Science with the Cherenkov Telescope Array

World Scientific, 2019

BS Acharya, I Agudo, T Armstrong, R Batista, G Cotter, A Franco, P Morris, S Sarkar, JJ Watson

The Cherenkov Telescope Array, CTA, will be the major global observatory for very high energy gamma-ray astronomy over the next decade and beyond. The scientific potential of CTA is extremely broad: from understanding the role of relativistic cosmic particles to the search for dark matter. CTA is an explorer of the extreme universe, probing environments from the immediate neighbourhood of black holes to cosmic voids on the largest scales. Covering a huge range in photon energy from 20 GeV to 300 TeV, CTA will improve on all aspects of performance with respect to current instruments. The observatory will operate arrays on sites in both hemispheres to provide full sky coverage and will hence maximize the potential for the rarest phenomena such as very nearby supernovae, gamma-ray bursts or gravitational wave transients. With 99 telescopes on the southern site and 19 telescopes on the northern site, flexible operation will be possible, with sub-arrays available for specific tasks. CTA will have important synergies with many of the new generation of major astronomical and astroparticle observatories. Multi-wavelength and multi-messenger approaches combining CTA data with those from other instruments will lead to a deeper understanding of the broad-band non-thermal properties of target sources. The CTA Observatory will be operated as an open, proposal-driven observatory, with all data available on a public archive after a pre-defined proprietary period. Scientists from institutions worldwide have combined together to form the CTA Consortium. This Consortium has prepared a proposal for a Core Programme of highly motivated observations. The programme, encompassing approximately 40% of the available observing time over the first ten years of CTA operation, is made up of individual Key Science Projects (KSPs), which are presented in this document.


CRPropa - A toolbox for cosmic ray simulations

Journal of Physics: Conference Series 1181 (2019)

R Alves Batista, J Becker Tjus, A Dundovic, M Erdmann, C Heiter, KH Kampert, D Kuempel, L Merten, G Müller, G Sigl, AV Vliet, D Walz, T Winchen, M Wirtz

© Published under licence by IOP Publishing Ltd. The astrophysical interpretation of recent experimental observations of cosmic rays relies increasingly on Monte Carlo simulations of cosmic ray propagation and acceleration. Depending on the energy range of interest, several different propagation effects inside the Milky Way as well as in extragalactic space have to be taken into account when interpreting the data. With the CRPropa framework we aim to provide a toolbox for according simulations. In recent versions of CRPropa, the ballistic single particle propagation mode aiming primarily at extragalactic cosmic rays has been complemented by a solver for the differential transport equation to address propagation of galactic cosmic rays. Additionally, modules have been developed to address cosmic ray acceleration and many improvements have been added for simulations of electromagnetic secondaries. In this contribution we will give an overview of the CRPropa simulation framework with a focus on the latest improvements and highlight selected features by example applications.


Magnetic Reconnection, Cosmic Ray Acceleration, and Gamma-Ray emission around Black Holes and Relativistic Jets

Proceedings of Science 329 (2018)

EM de Gouveia Dal Pino, RA Batista, LS Kadowaki, G Kowal, T Medina-Torrejon, JC Ramirez-Rodriguez

© Copyright owned by the author(s) under the terms of the Creative Commons. Particle acceleration by magnetic reconnection is now recognized as an important process in magnetically dominated regions of galactic and extragalactic black hole sources. This process helps to solve current puzzles specially related to the origin of the very high energy flare emission in these sources. In this review, we discuss this acceleration mechanism and show recent analytical studies and multidimensional numerical SRMHD and GRMHD (special and general relativistic magnetohydrodynamical) simulations with the injection of test particles, which help us to understand this process both in relativistic jets and coronal regions of these sources. The very high energy and neutrino emission resulting from the accelerated particles by reconnection is also discussed.


Extragalactic Sources and Propagation of UHECRs

Proceedings of 2016 International Conference on Ultra-High Energy Cosmic Rays (UHECR2016) Journal of the Physical Society of Japan (2018)

A van Vliet, RA Batista, G Sigl


Morphological properties of blazar-induced gamma-ray haloes

Proceedings of Science (2017)

RA Batista, A Saveliev

© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0). At TeV energies and above gamma rays can induce electromagnetic cascades, whose charged component is sensitive to intervening intergalactic magnetic fields (IGMFs). When interpreting gamma-ray measurements in the energy range between a few GeV and hundreds of TeV, one has to carefully account for effects due to IGMFs, which depend on their strength and power spectrum. Therefore, gamma-ray-induced electromagnetic cascades can be used as probes of cosmic magnetism, since their arrival distribution as well as spectral and temporal properties can provide unique information about IGMFs, whose origin and properties are currently poorly understood. In this contribution we present an efficient three-dimensional Monte Carlo code for simulations of gamma-ray propagation. We focus on the effects of different configurations of IGMFs, in particular magnetic helicity and the power spectrum of stochastic fields, on the morphology of the arrival directions of gamma rays, and discuss the prospects for detecting pair haloes around distant blazars.


Implications of strong intergalactic magnetic fields for ultrahigh-energy cosmic-ray astronomy

Physical Review D American Physical Society 96 (2017) 023010

R Batista, M-S Shin, J Devriendt, D Semikoz, G Sigl

We study the propagation of ultra-high-energy cosmic rays in the magnetised cosmic web. We focus on the particular case of highly magnetised voids ($B \sim \text{nG}$), using the upper bounds from the Planck satellite. The cosmic web was obtained from purely magnetohydrodynamical cosmological simulations of structure formation considering different power spectra for the seed magnetic field in order to account for theoretical uncertainties. We investigate the impact of these uncertainties on the propagation of cosmic rays, showing that they can affect the measured spectrum and composition by up to $\simeq 80\%$ and $\simeq 5\%$, respectivelly. In our scenarios, even if magnetic fields in voids are strong, deflections of 50 EeV protons from sources closer than $\sim\;$50 Mpc are less than $15^\circ$ in approximately 10-50% of the sky, depending on the distribution of sources and magnetic power spectrum. Therefore, UHECR astronomy might be possible in a significant portion of the sky depending on the primordial magnetic power spectrum, provided that protons constitute a sizeable fraction of the observed UHECR flux.


Ultrahigh-energy cosmic rays from tidally-ignited white dwarfs

PHYSICAL REVIEW D 96 (2017) ARTN 103003

RA Batista, J Silk


The Resilience of Life to Astrophysical Events

Scientific Reports Springer Nature 7 (2017) 5419-

D Sloan, R Alves Batista, A Loeb

<p>Much attention has been given in the literature to the effects of astrophysical events on human and land-based life. However, little has been discussed on the resilience of life itself. Here we instead explore the statistics of events that completely sterilise an Earth-like planet with planet radii in the range 0.5-1.5R ⊕ and temperatures of &amp;Tilde;300 K, eradicating all forms of life. We consider the relative likelihood of complete global sterilisation events from three astrophysical sources - supernovae, gamma-ray bursts, large asteroid impacts, and passing-by stars. To assess such probabilities we consider what cataclysmic event could lead to the annihilation of not just human life, but also extremophiles, through the boiling of all water in Earth&amp;apos;s oceans. Surprisingly we find that although human life is somewhat fragile to nearby events, the resilience of Ecdysozoa such as Milnesium tardigradum renders global sterilisation an unlikely event.</p>


Electromagnetic cascades as probes of cosmic magnetism

Nuovo Cimento della Societa Italiana di Fisica C 40 (2017)

RA Batista

The existence of intergalactic magnetic fields (IGMFs) is an open problem in cosmology and has never been unambiguously confirmed. High-energy gamma rays emitted by blazars are unique probes of cosmic magnetism, as their interactions with pervasive radiation fields generate a short-lived charged component sensitive to intervening magnetic fields. Spatial and temporal properties of the secondary gamma rays generated in the electromagnetic cascade can provide information about the strength, power spectrum, and topology of IGMFs. To probe these fields, detailed simulations of gamma-ray propagation in the intergalactic medium are necessary. In this work the effects of magnetic fields on the spectrum and arrival directions of gamma rays are studied using three-dimensional simulations, emphasising the particular case of helical IGMFs.


Cosmogenic gamma-rays and neutrinos constrain UHECR source models

Proceedings of Science Part F135186 (2017)

A Van Vliet, JR Hörandel, RA Batista

© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0). Purpose. When ultra-high-energy cosmic rays (UHECRs) propagate through the universe they produce secondary neutrinos as well as photons, electrons and positrons (initiating electromagnetic cascades) in different kinds of interactions. These neutrinos and electromagnetic cascades are detected at Earth as isotropic extragalactic fluxes. The level of these fluxes can be predicted and used to constrain UHECR source models. Methods. The public astrophysical simulation framework CRPropa 3, designed for simulating the propagating extraterrestrial ultra-high energy particles, is ideally suited for this purpose. CRPropa includes all relevant UHECR interactions as well as secondary neutrino and electromagnetic cascade production and propagation. It is designed for high-performance computing and provides the flexibility to scan large parameter ranges of UHECR models. Results. The expected cosmogenic neutrino and gamma-ray spectra depend strongly on the evolution with redshift of the UHECR sources and on the chemical composition of UHECRs at injection. The isotropic diffuse gamma-ray background measured by Fermi/LAT is already close to touching upon a model with co-moving source evolution and with the chemical composition, spectral index and maximum acceleration energy optimized to provide the best fit to the UHECR spectrum and composition measured by the Pierre Auger Collaboration. Additionally, the detectable fraction of protons present at the highest energies in UHECRs is shown as a function of the evolution of UHECR sources for a range of sensitivities of neutrino detectors at an energy of ∼ 1 EeV. Conclusions. Neutrino and gamma-ray measurements are starting to constrain realistic UHECR models. Current and future neutrino experiments with sensitivities in the range of ∼ 10 -8 - 10 -10 GeV cm -2 s -1 sr -1 for the single-flavor neutrino flux at ∼ 1 EeV will be able to significantly constrain the proton fraction for realistic source evolution models.


Morphological properties of blazar-induced gamma-ray haloes

Proceedings of Science Part F135186 (2017)

RA Batista, A Saveliev

© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License (CC BY-NC-ND 4.0). At TeV energies and above gamma rays can induce electromagnetic cascades, whose charged component is sensitive to intervening intergalactic magnetic fields (IGMFs). When interpreting gamma-ray measurements in the energy range between a few GeV and hundreds of TeV, one has to carefully account for effects due to IGMFs, which depend on their strength and power spectrum. Therefore, gamma-ray-induced electromagnetic cascades can be used as probes of cosmic magnetism, since their arrival distribution as well as spectral and temporal properties can provide unique information about IGMFs, whose origin and properties are currently poorly understood. In this contribution we present an efficient three-dimensional Monte Carlo code for simulations of gamma-ray propagation. We focus on the effects of different configurations of IGMFs, in particular magnetic helicity and the power spectrum of stochastic fields, on the morphology of the arrival directions of gamma rays, and discuss the prospects for detecting pair haloes around distant blazars.

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