Publications by Rafael Alves Batista

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


J Alvarez-Muniz, RA Batista, AV Balagopal, J Bolmont, M Bustamante, CW Jr, D Charrier, I Cognard, V Decoene, PB Denton, S De Jong, KD De Vries, R Engel, K Fang, C Finley, S Gabici, Q Gou, J Gu, C Guepin, H Hu, Y Huang, K Kotera, S Le Coz, J-P Lenain, G Lu, O Martineau-Huynh, M Mostafa, F Mottez, K Murase, V Niess, F Oikonomou, T Pierog, X Qian, B Qin, D Ran, N Renault-Tinacci, M Roth, FG Schroeder, F Schussler, C Tasse, C Timmermans, M Tueros, X Wu, P Zarka, A Zech, BT Zhang, J Zhang, Y Zhang, Q Zheng, A Zilles

Neutrino and Î3-ray Emission from the Core of NGC1275 by Magnetic Reconnection: GRMHD Simulations and Radiative Transfer/Particle Calculations

Proceedings of the International Astronomical Union (2020) 184-188

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

© International Astronomical Union 2020. Very high energy (VHE) emission has been detected from the radio galaxy NGC1275, establishing it as a potential cosmic-ray (CR) accelerator and a high energy neutrino source. We here study neutrino and Î3-ray emission from the core of NGC1275 simulating the interactions of CRs assumed to be accelerated by magnetic reconnection, with the accreting plasma environment. To do this, we combine (i) numerical general relativistic (GR) magneto-hydrodynamics (MHD), (ii) Monte Carlo GR leptonic radiative transfer and, (iii) Monte Carlo interaction of CRs. A leptonic emission model that reproduces the SED in the [103-1010.5] eV energy range is used as the background target for photo-pion interactions+electromagnetic cascading. CRs injected with the power-law index κ=1.3 produce an emission profile that matches the VHE tail of NGC1275. The associated neutrino flux, below the IceCube limits, peaks at âˆ1/4PeV energies. However, coming from a single source, this neutrino flux may be an over-estimation.

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.

Open Questions in Cosmic-Ray Research at Ultrahigh Energies

Frontiers in Astronomy and Space Sciences 6 (2019)

R Alves Batista, J Biteau, M Bustamante, K Dolag, R Engel, K Fang, KH Kampert, D Kostunin, M Mostafa, K Murase, F Oikonomou, AV Olinto, MI Panasyuk, G Sigl, AM Taylor, M Unger

© Copyright © 2019 Alves Batista, Biteau, Bustamante, Dolag, Engel, Fang, Kampert, Kostunin, Mostafa, Murase, Oikonomou, Olinto, Panasyuk, Sigl, Taylor and Unger. We review open questions and prospects for progress in ultrahigh-energy cosmic ray (UHECR) research, based on a series of discussions that took place during the “The High-Energy Universe: Gamma-Ray, Neutrino, and Cosmic-ray Astronomy” MIAPP workshop in 2018. Specifically, we overview open questions on the origin of the bulk of UHECRs, the UHECR mass composition, the origin of the end of the cosmic-ray spectrum, the transition from Galactic to extragalactic cosmic rays, the effect of magnetic fields on the trajectories of UHECRs, anisotropy expectations for specific astrophysical scenarios, hadronic interactions, and prospects for discovering neutral particles as well as new physics at ultrahigh energies. We also briefly overview upcoming and proposed UHECR experiments and discuss their projected science reach.

Secondary neutrino and gamma-ray fluxes from SimProp and CRPropa


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

E Amato, LA Antonelli, C Aramo, F Arqueros, K Asano, M Balbo, B Balmaverde, P Barai, A Barbano, J Becerra González, L Bellizzi, MI Bernardos, A Bonardi, C Bonavolontá, G Bonnoli, AM Brown, A Bulgarelli, R Capuzzo-Dolcetta, R Carosi, S Casanova, O Catalano, D Cauz, A Costa, P Cristofari, S Spencer

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.

Current constraints from cosmogenic neutrinos on the fraction of protons in UHECRs

Proceedings of Science 358 (2019)

A van Vliet, RA Batista, JR Hörandel

© Owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). Cosmogenic neutrinos are created when ultra-high-energy cosmic rays (UHECRs) interact with extragalactic photon backgrounds. In general, the expected flux of these cosmogenic neutrinos depends on multiple parameters, describing the sources and propagation of UHECRs. In our recent paper [1], we show that a 'sweet spot'occurs at a neutrino energy of E? ~ 1 EeV. At that energy the flux mainly depends on two parameters, the source evolution and the fraction of protons in UHECRs at Earth for Ep & 30 EeV. Therefore, with current upper limits on the cosmogenic neutrino flux at E? ~ 1 EeV and assuming a certain source class, a constraint on the composition of UHECRs can be obtained. This constraint is independent of hadronic interaction models and indicates that the combination of a large proton fraction and a strong source evolution is disfavored. Upcoming neutrino experiments will be able to constrain the fraction of protons in UHECRs even further, and for any realistic model for the evolution of UHECR sources.

Cosmogenic photon and neutrino fluxes in the Auger era


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


RA Batista, A Saveliev

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


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

The impact of plasma instabilities on the spectra of TeV blazars


RA Batista, A Saveliev, EM de Gouveia Dal Pino

Science with the Cherenkov Telescope Array

World Scientific, 2019

BS Acharya, I Agudo, R Batista, T Armstrong, 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

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.