Pulsars, transients and relativistic astrophysics

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Monte Carlo Simulations and Validation of NectarCAM, a Medium Sized Telescope Camera for CTA

Proceedings of Science 395 (2022)

Authors:

TP Armstrong, H Costantini, JF Glicenstein, JP Lenain, U Schwanke, T Tavernier, H Abdalla, H Abe, S Abe, A Abusleme, F Acero, A Acharyya, V Acín Portella, K Ackley, R Adam, C Adams, SS Adhikari, I Aguado-Ruesga, I Agudo, R Aguilera, A Aguirre-Santaella, F Aharonian, A Alberdi, R Alfaro, J Alfaro, C Alispach, R Aloisio, R Alves Batista, JP Amans, L Amati, E Amato, L Ambrogi, G Ambrosi, M Ambrosio, R Ammendola, J Anderson, M Anduze, EO Angüner, LA Antonelli, V Antonuccio, P Antoranz, R Anutarawiramkul, J Aragunde Gutierrez, C Aramo, A Araudo, M Araya, A Arbet-Engels, C Arcaro, V Arendt, C Armand, F Arqueros, L Arrabito, B Arsioli, M Artero, K Asano, Y Ascasíbar, J Aschersleben, M Ashley, P Attinà, P Aubert, CB Singh, D Baack, A Babic, M Backes, V Baena, S Bajtlik, A Baktash, C Balazs, M Balbo, O Ballester, J Ballet, B Balmaverde, A Bamba, R Bandiera, A Baquero Larriva, P Barai, C Barbier, V Barbosa Martins, M Barcelo, M Barkov, M Barnard, L Baroncelli, U Barres de Almeida, JA Barrio, D Bastieri, PI Batista, I Batkovic, C Bauer, R Bautista-González, J Baxter, U Becciani, J Becerra González, Y Becherini, G Beck, J Becker Tjus, W Bednarek, A Belfiore, L Bellizzi, R Belmont

Abstract:

The upcoming Cherenkov Telescope Array (CTA) ground-based gamma-ray observatory will open up our view of the very high energy Universe, offering an improvement in sensitivity of 5-10 times that of previous experiments. NectarCAM is one of the proposed cameras for the Medium-Sized Telescopes (MST) which have been designed to cover the core energy range of CTA, from 100 GeV to 10 TeV. The final camera will be capable of GHz sampling and provide a field of view of 8 degrees with its 265 modules of 7 photomultiplier each (for a total of 1855 pixels). In order to validate the performance of NectarCAM, a partially-equipped prototype has been constructed consisting of only the inner 61-modules. It has so far undergone testing at the integration test-bench facility in CEA Paris-Saclay (France) and on a prototype of the MST structure in Adlershof (Germany). To characterize the performance of the prototype, Monte Carlo simulations were conducted using a detailed model of the 61 module camera in the CORSIKA/sim_telarray framework. This contribution provides an overview of this work including the comparison of trigger and readout performance on test-bench data and trigger and image parameterization performance during on-sky measurements.

Performance of the Cherenkov Telescope Array in the presence of clouds

Proceedings of Science 395 (2022)

Authors:

M Pecimotika, K Adamczyk, DD Prester, O Gueta, D Hrupec, G Maier, S Mićanović, L Pavletić, J Sitarek, D Sobczyńska, M Szanecki, H Abdalla, H Abe, S Abe, A Abusleme, F Acero, A Acharyya, V Acín Portella, K Ackley, R Adam, C Adams, SS Adhikari, I Aguado-Ruesga, I Agudo, R Aguilera, A Aguirre-Santaella, F Aharonian, A Alberdi, R Alfaro, J Alfaro, C Alispach, R Aloisio, R Alves Batista, JP Amans, L Amati, E Amato, L Ambrogi, G Ambrosi, M Ambrosio, R Ammendola, J Anderson, M Anduze, EO Angüner, LA Antonelli, V Antonuccio, P Antoranz, R Anutarawiramkul, J Aragunde Gutierrez, C Aramo, A Araudo, M Araya, A Arbet-Engels, C Arcaro, V Arendt, C Armand, T Armstrong, F Arqueros, L Arrabito, B Arsioli, M Artero, K Asano, Y Ascasíbar, J Aschersleben, M Ashley, P Attinà, P Aubert, CB Singh, D Baack, A Babic, M Backes, V Baena, S Bajtlik, A Baktash, C Balazs, M Balbo, O Ballester, J Ballet, B Balmaverde, A Bamba, R Bandiera, A Baquero Larriva, P Barai, C Barbier, V Barbosa Martins, M Barcelo, M Barkov, M Barnard, L Baroncelli, U Barres de Almeida, JA Barrio, D Bastieri, PI Batista, I Batkovic, C Bauer, R Bautista-González, J Baxter, U Becciani, J Becerra González, Y Becherini, G Beck

Abstract:

The Cherenkov Telescope Array (CTA) is the future ground-based observatory for gamma-ray astronomy at very high energies. The atmosphere is an integral part of every Cherenkov telescope. Different atmospheric conditions, such as clouds, can reduce the fraction of Cherenkov photons produced in air showers that reach ground-based telescopes, which may affect the performance. Decreased sensitivity of the telescopes may lead to misconstructed energies and spectra. This study presents the impact of various atmospheric conditions on CTA performance. The atmospheric transmission in a cloudy atmosphere in the wavelength range from 203 nm to 1000 nm was simulated for different cloud bases and different optical depths using the MODerate resolution atmospheric TRANsmission (MODTRAN) code. MODTRAN output files were used as inputs for generic Monte Carlo simulations. The analysis was performed using the MAGIC Analysis and Reconstruction Software (MARS) adapted for CTA. As expected, the effects of clouds are most evident at low energies, near the energy threshold. Even in the presence of dense clouds, high-energy gamma rays may still trigger the telescopes if the first interaction occurs lower in the atmosphere, below the cloud base. A method to analyze very high-energy data obtained in the presence of clouds is presented. The systematic uncertainties of the method are evaluated. These studies help to gain more precise knowledge about the CTA response to cloudy conditions and give insights on how to proceed with data obtained in such conditions. This may prove crucial for alert-based observations and time-critical studies of transient phenomena.

Prototype Open Event Reconstruction Pipeline for the Cherenkov Telescope Array

Proceedings of Science 395 (2022)

Authors:

M Nöthe, K Kosack, L Nickel, M Peresano, H Abdalla, H Abe, S Abe, A Abusleme, F Acero, A Acharyya, V Acín Portella, K Ackley, R Adam, C Adams, SS Adhikari, I Aguado-Ruesga, I Agudo, R Aguilera, A Aguirre-Santaella, F Aharonian, A Alberdi, R Alfaro, J Alfaro, C Alispach, R Aloisio, R Alves Batista, JP Amans, L Amati, E Amato, L Ambrogi, G Ambrosi, M Ambrosio, R Ammendola, J Anderson, M Anduze, EO Angüner, LA Antonelli, V Antonuccio, P Antoranz, R Anutarawiramkul, J Aragunde Gutierrez, C Aramo, A Araudo, M Araya, A Arbet-Engels, C Arcaro, V Arendt, C Armand, T Armstrong, F Arqueros, L Arrabito, B Arsioli, M Artero, K Asano, Y Ascasíbar, J Aschersleben, M Ashley, P Attinà, P Aubert, CB Singh, D Baack, A Babic, M Backes, V Baena, S Bajtlik, A Baktash, C Balazs, M Balbo, O Ballester, J Ballet, B Balmaverde, A Bamba, R Bandiera, A Baquero Larriva, P Barai, C Barbier, V Barbosa Martins, M Barcelo, M Barkov, M Barnard, L Baroncelli, U Barres de Almeida, JA Barrio, D Bastieri, PI Batista, I Batkovic, C Bauer, R Bautista-González, J Baxter, U Becciani, J Becerra González, Y Becherini, G Beck, J Becker Tjus, W Bednarek, A Belfiore, L Bellizzi, R Belmont, W Benbow, D Berge

Abstract:

The Cherenkov Telescope Array (CTA) is the next-generation gamma-ray observatory currently under construction. It will improve over the current generation of imaging atmospheric Cherenkov telescopes (IACTs) by a factor of five to ten in sensitivity and it will be able to observe the whole sky from a combination of two sites: a northern site in La Palma, Spain, and a southern one in Paranal, Chile. CTA will also be the first open gamma-ray observatory. Accordingly, the data analysis pipeline is developed as open-source software. The event reconstruction pipeline accepts raw data of the telescopes and processes it to produce suitable input for the higher-level science tools. Its primary tasks include reconstructing the physical properties of each recorded shower and providing the corresponding instrument response functions. ctapipe is a framework providing algorithms and tools to facilitate raw data calibration, image extraction, image parameterization and event reconstruction. Its main focus is currently the analysis of simulated data but it has also been successfully applied for the analysis of data obtained with the first CTA prototype telescopes, such as the Large-Sized Telescope 1 (LST-1). pyirf is a library to calculate IACT instrument response functions, needed to obtain physics results like spectra and light curves, from the reconstructed event lists. Building on these two, protopipe is a prototype for the event reconstruction pipeline for CTA. Recent developments in these software packages will be presented.

Reconstruction of stereoscopic CTA events using deep learning with CTLearn

Proceedings of Science 395 (2022)

Authors:

T Miener, D Nieto, A Brill, S Spencer, JL Contreras, H Abdalla, H Abe, S Abe, A Abusleme, F Acero, A Acharyya, V Acín Portella, K Ackley, R Adam, C Adams, SS Adhikari, I Aguado-Ruesga, I Agudo, R Aguilera, A Aguirre-Santaella, F Aharonian, A Alberdi, R Alfaro, J Alfaro, C Alispach, R Aloisio, R Alves Batista, JP Amans, L Amati, E Amato, L Ambrogi, G Ambrosi, M Ambrosio, R Ammendola, J Anderson, M Anduze, EO Angüner, LA Antonelli, V Antonuccio, P Antoranz, R Anutarawiramkul, J Aragunde Gutierrez, C Aramo, A Araudo, M Araya, A Arbet-Engels, C Arcaro, V Arendt, C Armand, T Armstrong, F Arqueros, L Arrabito, B Arsioli, M Artero, K Asano, Y Ascasíbar, J Aschersleben, M Ashley, P Attinà, P Aubert, CB Singh, D Baack, A Babic, M Backes, V Baena, S Bajtlik, A Baktash, C Balazs, M Balbo, O Ballester, J Ballet, B Balmaverde, A Bamba, R Bandiera, A Baquero Larriva, P Barai, C Barbier, V Barbosa Martins, M Barcelo, M Barkov, M Barnard, L Baroncelli, U Barres de Almeida, JA Barrio, D Bastieri, PI Batista, I Batkovic, C Bauer, R Bautista-González, J Baxter, U Becciani, J Becerra González, Y Becherini, G Beck, J Becker Tjus, W Bednarek, A Belfiore, L Bellizzi, R Belmont, W Benbow

Abstract:

The Cherenkov Telescope Array (CTA), conceived as an array of tens of imaging atmospheric Cherenkov telescopes (IACTs), is an international project for a next-generation ground-based gamma-ray observatory, aiming to improve on the sensitivity of current-generation instruments a factor of five to ten and provide energy coverage from 20 GeV to more than 300 TeV. Arrays of IACTs probe the very-high-energy gamma-ray sky. Their working principle consists of the simultaneous observation of air showers initiated by the interaction of very-high-energy gamma rays and cosmic rays with the atmosphere. Cherenkov photons induced by a given shower are focused onto the camera plane of the telescopes in the array, producing a multi-stereoscopic record of the event. This image contains the longitudinal development of the air shower, together with its spatial, temporal, and calorimetric information. The properties of the originating very-high-energy particle (type, energy, and incoming direction) can be inferred from those images by reconstructing the full event using machine learning techniques. In this contribution, we present a purely deep-learning driven, full-event reconstruction of simulated, stereoscopic IACT events using CTLearn. CTLearn is a package that includes modules for loading and manipulating IACT data and for running deep learning models, using pixel-wise camera data as input.

Sensitivity of CTA to gamma-ray emission from the Perseus galaxy cluster

Proceedings of Science 395 (2022)

Authors:

H Abdalla, H Abe, S Abe, A Abusleme, F Acero, A Acharyya, V Acín Portella, K Ackley, R Adam, C Adams, SS Adhikari, I Aguado-Ruesga, I Agudo, R Aguilera, A Aguirre-Santaella, F Aharonian, A Alberdi, R Alfaro, J Alfaro, C Alispach, R Aloisio, R Alves Batista, JP Amans, L Amati, E Amato, L Ambrogi, G Ambrosi, M Ambrosio, R Ammendola, J Anderson, M Anduze, EO Angüner, LA Antonelli, V Antonuccio, P Antoranz, R Anutarawiramkul, J Aragunde Gutierrez, C Aramo, A Araudo, M Araya, A Arbet-Engels, C Arcaro, V Arendt, C Armand, T Armstrong, F Arqueros, L Arrabito, B Arsioli, M Artero, K Asano, Y Ascasíbar, J Aschersleben, M Ashley, P Attinà, P Aubert, CB Singh, D Baack, A Babic, M Backes, V Baena, S Bajtlik, A Baktash, C Balazs, M Balbo, O Ballester, J Ballet, B Balmaverde, A Bamba, R Bandiera, A Baquero Larriva, P Barai, C Barbier, V Barbosa Martins, M Barcelo, M Barkov, M Barnard, L Baroncelli, U Barres de Almeida, JA Barrio, D Bastieri, PI Batista, I Batkovic, C Bauer, R Bautista-González, J Baxter, U Becciani, J Becerra González, Y Becherini, G Beck, J Becker Tjus, W Bednarek, A Belfiore, L Bellizzi, R Belmont, W Benbow, D Berge, E Bernardini, MI Bernardos, K Bernlöhr, A Berti

Abstract:

In these proceedings we summarize the current status of the study of the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse gamma-ray emission from the Perseus galaxy cluster. Gamma-ray emission is expected in galaxy clusters both from interactions of cosmic rays (CR) with the intra-cluster medium, or as a product of annihilation or decay of dark matter (DM) particles in case they are weakly interactive massive particles (WIMPs). The observation of Perseus constitutes one of the Key Science Projects to be carried out by the CTA Consortium. In this contribution, we focus on the DM-induced component of the flux. Our DM modelling includes the substructures we expect in the main halo which will boost the annihilation signal significantly. We adopt an ON/OFF observation strategy and simulate the expected gamma-ray signals. Finally we compute the expected CTA sensitivity using a likelihood maximization analysis including the most recent CTA instrument response functions. In absence of signal, we show that CTA will allow us to provide stringent and competitive constraints on TeV DM, especially for the case of DM decay.