1,253 research outputs found
CTAO Instrument Response Functions - prod5 version v0.1
No full textCTAO Instrument Response Functions - prod5 version v0.1 The CTA Observatory (CTAO) will provide very wide energy range and excellent angular resolution and sensitivity in comparison to any existing gamma-ray detector. Energies down to 20 GeV will allow CTAO to study the most distant objects. Energies up to 300 TeV will push CTAO beyond the edge of the known electromagnetic spectrum, providing a completely new view of the sky. This data repository provides access to performance evaluation and instrument response functions (IRFs) for CTA. IRF version: prod5 v0.1 Telescope model and site configuration: prod5-model Publication date: Sep 2021 Archived webpage with performance figures included: CTAO Performance Description (file Website.md) Licence: this work is licensed under a Creative Commons Attribution 4.0 International License . Please use the contact address [email protected] for any inquiries. Citation and Acknowledgements: In cases for which the CTA instrument response functions are used in a research project, we ask to add the following acknowledgement in any resulting publication: 'This research has made use of the CTA instrument response functions provided by the CTA Consortium and Observatory, see https://www.ctao-observatory.org/science/cta-performance/ (version prod5 v0.1; [citation]) for more details.' Please use the following BibTex Entry for [citation] in the reference section of your publication: https://zenodo.org/record/5499840/export/hx Description Monte Carlo Simulations: The performance values are derived from detailed Monte Carlo (MC) simulations of the CTA instrument based on the CORSIKA air shower code (v7.71, with the hadronic interaction models QGSjet-II-04 and URQMD, [1]) and telescope simulation tool sim_telarray [2]. A power- law gamma-ray spectrum with photon index 2.62 was assumed in the calculations, although none of the instrument response functions (e.g. differential flux sensitivities, effective areas, angular or energy resolutions) depends on the assumed spectral shape of the gamma-ray source. Background cosmic-ray spectra of proton and electron/positron particle types are modelled according to recent measurements from cosmic-ray instruments. Nominal telescope pointing is assumed, with all telescopes pointing directions parallel to each other (performance estimation for other pointing modes, e.g. divergent pointing will be provided in the future). Performance estimations are available for three zenith angles (20 deg, 40 deg, and 60 deg), and for each zenith angle for two different azimuth angles (corresponding to pointing towards the magnetic North and South). There are significant performance differences found between the two azimuthal pointing directions (especially for the Northern site) as the impact of the geomagnetic field is large enough to influence notably the air shower development. For general studies, the use of the azimuth-averaged instrument response functions is recommended. Instrument Response Functions (IRFs): The analysis has been tuned to maximize the performance in terms of flux sensitivity. The optimal analysis cuts depend on the duration of the observation, therefore the IRFs are provided for 3 different observation times, from 0.5 to 50 h. IRFs are provided as binned histogram or FITS tables. It should be stressed, that the full potential of CTA in terms of angular and energy resolution is not revealed by these IRFS, due to the focus on the optimisation for best flux sensitivity. In general all histograms are binned with a 0.2-binning on the logarithmic energy axis (5 bins per decade); some selected histograms (e.g. effective areas or energy migration matrices) are provided with a finer binning. Effective area and energy migration matrix are available in a double version: one for the case in which there is no a priori knowledge of the true direction of incoming gamma rays (e.g. for the observation of diffuse sources), and another for observations of point-like objects (including among the analysis cuts one on the angle between the true and the reconstructed gamma-ray direction). IRFs are provided in ROOT format and as FITS tables. The FITS tables can be used directly as input to science analysis tools. The values of the IRFs are identical for the different file format, with one exception: the angular point-spread function is approximated by a Gaussian function for the FITS tables, while the ROOT files contain the full distribution. Telescope layouts are preliminary and subject to change. The following array layouts (Alpha configuration) have been assumed: CTA South with 14 MSTs and 37 SSTs (see [figure](figures/CTA-Performance-prod5-v0.1-South-Alpha-Layout.png)) CTA North with 4 LSTs and 9 MSTs (see [figure](figures/CTA-Performance-prod5-v0.1-North-Alpha-Layout.png)) Two zip files are uploaded: full archive with IRFs in FITS and ROOT format: cta-prod5-zenodo-v0.1.zip partial archive with IRFs in FITS format only: cta-prod5-zenodo-fitsonly-v0.1.zip File Naming (examples): Prod5-North-40deg-AverageAz-4LSTs09MSTs.18000s-v0.1.root: IRF for CTA Northern site on La Palma, 40 deg zenith angle, azimuth-averaged pointing, optimised for 5 hours of observation time Prod5-South-20deg-AverageAz-14MSTs37SSTs.180000s-v0.1.fits.gz: IRF for CTA Southern site in Paranal, 20 deg zenith angle, azimuth-averaged pointing, optimised for 50 hours of observation time List of files: FITS format: fits/CTA-Performance-prod5-v0.1-North-20deg.FITS.tar.gz fits/CTA-Performance-prod5-v0.1-North-40deg.FITS.tar.gz fits/CTA-Performance-prod5-v0.1-North-60deg.FITS.tar.gz fits/CTA-Performance-prod5-v0.1-South-20deg.FITS.tar.gz fits/CTA-Performance-prod5-v0.1-South-40deg.FITS.tar.gz fits/CTA-Performance-prod5-v0.1-South-60deg.FITS.tar.gz ROOT format: root/CTA-Performance-prod5-v0.1-North-20deg.tar.gz root/CTA-Performance-prod5-v0.1-North-40deg.tar.gz root/CTA-Performance-prod5-v0.1-North-60deg.tar.gz root/CTA-Performance-prod5-v0.1-South-20deg.tar.gz root/CTA-Performance-prod5-v0.1-South-40deg.tar.gz root/CTA-Performance-prod5-v0.1-South-60deg.tar.gz IRFs for subarrays of e.g., MSTs only are in the files named MSTSubArray (similar for all other telescope types). References [1] https://www.ikp.kit.edu/corsika/ [2] Bernloehr, K. 2008, Astroparticle Physics, 30, 149 Acknowledgements We would like to thank the computing centres that provided resources for the generation of the Prod 5 Instrument Response Functions (IRFs): CAMK, Nicolaus Copernicus Astronomical Center, Warsaw, Poland CIEMAT-LCG2, CIEMAT, Madrid, Spain CYFRONET-LCG2, ACC CYFRONET AGH, Cracow, Poland DESY-ZN, Deutsches Elektronen-Synchrotron, Standort Zeuthen, Germany GRIF, Grille de Recherche d’Ile de France, Paris, France IN2P3-CC, Centre de Calcul de l’IN2P3, Villeurbanne, France IN2P3-CPPM, Centre de Physique des Particules de Marseille, Marseille, France IN2P3-LAPP, Laboratoire d Annecy de Physique des Particules, Annecy, France INFN-FRASCATI, INFN Frascati, Frascati, Italy INFN-T1, CNAF INFN, Bologna, Italy INFN-TORINO, INFN Torino, Torino, Italy MPIK, Heidelberg, Germany OBSPM, Observatoire de Paris Meudon, Paris, France PIC, port d’informacio cientifica, Bellaterra, Spain prague_cesnet_lcg2, CESNET, Prague, Czech Republic praguelcg2, FZU Prague, Prague, Czech Republic UKI-NORTHGRID-LANCS-HEP, Lancaster University, United Kingdo
Sensitivity of the Cherenkov Telescope Array to spectral signatures of hadronic PeVatrons with application to Galactic Supernova Remnants
No full textThe local Cosmic Ray (CR) energy spectrum exhibits a spectral softening at energies around 3 PeV. Sources which are capable of accelerating hadrons to such energies are called hadronic PeVatrons. However, hadronic PeVatrons have not yet been firmly identified within the Galaxy. Several source classes, including Galactic Supernova Remnants (SNRs), have been proposed as PeVatron candidates. The potential to search for hadronic PeVatrons with the Cherenkov Telescope Array (CTA) is assessed. The focus is on the usage of very high energy γ-ray spectral signatures for the identification of PeVatrons. Assuming that SNRs can accelerate CRs up to knee energies, the number of Galactic SNRs which can be identified as PeVatrons with CTA is estimated within a model for the evolution of SNRs. Additionally, the potential of a follow-up observation strategy under moonlight conditions for PeVatron searches is investigated. Statistical methods for the identification of PeVatrons are introduced, and realistic Monte-Carlo simulations of the response of the CTA observatory to the emission spectra from hadronic PeVatrons are performed. Based on simulations of a simplified model for the evolution for SNRs, the detection of a γ-ray signal from in average 9 Galactic PeVatron SNRs is expected to result from the scan of the Galactic plane with CTA after 10 h of exposure. CTA is also shown to have excellent potential to confirm these sources as PeVatrons in deep observations with (100) hours of exposure per source
Observing the Galactic Plane with the Cherenkov Telescope Array
No full textThe Cherenkov Telescope Array is a next generation ground-based gamma-ray observatory de- signed to detect photons in the 20 GeV to 300 TeV energy range. With a sensitivity improvement of up to one order of magnitude on the entire energy range with respect to currently operating facilities, coupled with significantly better angular resolution, the array will be used to address many open questions in high-energy astrophysics. In addition, CTA will explore the ultra-high energy (E >50 TeV) window with great sensitivity for the first time. CTA is expected to reveal a detailed picture of the Galactic plane at the highest energies, and to discover around one hundred new supernova remnants and many hundreds of pulsar wind nebulae, according to current population estimates. The ability of the observatory to resolve such a large number of Galactic sources is one of the challenges to be faced. In this paper, we will present the first simulated scan of the Galactic plane with a realistic observation strategy, with particular attention to the potential source confusion. We will also present prospects for morphological studies of extended sources, such as the young SNR RX J1713.7-39
Exploring deep learning as an event classification method for the Cherenkov Telescope Array
No full textTelescopes based on the imaging atmospheric Cherenkov technique (IACTs) detect images of the atmospheric showers generated by gamma rays and cosmic rays as they are absorbed by the atmosphere. The much more frequent cosmic-ray events form the main background when looking for gamma-ray sources, and therefore IACT sensitivity is significantly driven by the capability to distinguish between these two types of events. Supervised learning algorithms, like random forests and boosted decision trees, have been shown to effectively classify IACT events. In this contribution we present results from exploratory work using deep learning as an event classification method for the Cherenkov Telescope Array (CTA). CTA, conceived as an array of tens of IACTs, is an international project for a next-generation ground-based gamma-ray observatory, aiming to improve on the sensitivity of current-generation experiments by an order of magnitude and provide energy coverage from 20 GeV to more than 300 TeV
CTAO Monte Carlo Simulations - Eventlists on DL2 data level - prod5
No full textAuthor: Cherenkov Telescope Array Observatory; Cherenkov Telescope Array Consortium Contact: [email protected] The Cherenkov Telescope Array Observatory (CTAO) will be the next-generation gamma-ray observatory and is currently under construction on the island of La Palma (Spain) and near Paranal (Chile). This repository provides access to reconstructed event information (DL2- and DL1-level, simulation parameters) from Monte Carlo simulations of the CTAO Northern Array (production 5). The Monte Carlo simulations for prod5 are described in arXiv:2108.04512 , the simulation telescopes models used in the telescope simulation program sim_telarray and the configuration used in the air-shower code CORSIKA are available from the Zenodo archive for CTA Prod5 Telescope Models . MC events are calibrated and reconstructed using the ctapipe package and stored for the following data levels: - R1-MC: simulated raw data (output from sim_telarray) - DL1 (this repository) : telescope level data including images and image parameters - DL2 (this repository) : reconstructed event parameters such as energy, direction, gamma/hadron discrimination parameters - DL3: selected events with associated instrument response functions (IRFs). Preliminary DL3-IRFs are available from [here](https://doi.org/10.5281/zenodo.5499839). For a description of the file format and data model, see CTAPipe Data Model . Data set description: - using ctapipe version 0.17 ( GitHub release page , Zenodo page ) - CTAO Northern Array on La Palma for the Alpha configuration (4 large-sized telescopes, 9 mid-sized telescopes) - Zenith angles of 20 deg, telescope pointing direction north and south - Primary particles: photons, protons - For convenience, the same data is provided in a single, large file per particle type for the whole dataset which do not contain the low-level DL1 image information and a larger number of files including this information. We explicitly note that the products provided are preliminary and do not reflect the final performance of the CTA Observatory, neither are data structure or formats finalized. We also note that these data products are different to those used for the CTAO Instrument Response Functions . In cases in which the data provided in this repository are used in a research project, we ask that the following acknowledgment is added in any resulting publication: 'This research has made use of the CTA DL1 and DL2 Event lists provided by the CTA Observatory and Consortium (version prod5-DL2-release1-DL2)' and cite this repository in the reference section of your publication. We would like to thank the computing centers that provided resources for the generation of the Prod5 simulation set, click here for a list of service providers
Contributions from the Cherenkov Telescope Array (CTA) Consortium to the ICRC 2011
No full textThe Cherenkov Telescope Array (CTA) is a project for the construction of a next generation VHE gamma ray observatory with full sky coverage. Its aim is improving by about one order of magnitude the sensitivity of the existing installations, covering about 5 decades in energy (from few tens of GeV to above a hundred TeV) and having enhanced angular and energy resolutions. During 2010 the project became a truly global endeavour carried out by a consortium of about 750 collaborators from Europe, Asia, Africa and the North and South Americas. Also during 2010 the CTA project completed its Design Study phase and started a Preparatory Phase that is expected to extend for three years and should lead to the starting of the construction of CTA. An overview of the CTA Consortium activities project will be given
Atmospheric monitoring and array calibration in CTA using the Cherenkov Transparency Coefficient
No full textThe Cherenkov Telescope Array (CTA) will be the next generation observatory employing different types of Cherenkov telescopes for the detection of particle showers initiated by very-high-energy gamma rays. A good knowledge of the Earths atmosphere, which acts as a calorimeter in the detection technique, will be crucial for calibration in CTA. Variations of the atmospheres transparency to Cherenkov light and not correctly performed calibration of individual telescopes in the array result in large systematic uncertainties on the energy scale. The Cherenkov Transparency Coefficient (CTC), developed within the H.E.S.S. experiment, quantifies the mean atmosphere transparency ascertained from data taken by Cherenkov telescopes during scientific observations. Provided that atmospheric conditions over the array are uniform, transparency values obtained per telescope can be also used for the calibration of individual telescope responses. The application of the CTC in CTA presents a challenge due to the greater complexity of the observatory and the variety of telescope cameras compared with currently operating experiments, such as H.E.S.S. We present here the first results of a feasibility study for extension of the CTC concept in CTA for purposes of the inter-calibration of the telescopes in the array and monitoring of the atmosphere
Prototype 9.7 m Schwarzschild-Couder telescope for the Cherenkov Telescope Array: status of the optical system
No full textThe Cherenkov Telescope Array (CTA) is an international project for a next-generation ground-based gamma ray observatory, aiming to improve on the sensitivity of current-generation experiments by an order of magnitude and provide energy coverage from 30 GeV to more than 300 TeV. The 9.7m Schwarzschild-Couder (SC) candidate medium-size telescope for CTA exploits a novel aplanatic two-mirror optical design that provides a large field of view of 8 degrees and substantially improves the off-axis performance giving better angular resolution across all of the field of view with respect to single-mirror telescopes. The realization of the SC optical design implies the challenging production of large aspherical mirrors accompanied by a submillimeter-precision custom alignment system. In this contribution we report on the status of the implementation of the optical system on a prototype 9.7 m SC telescope located at the Fred Lawrence Whipple Observatory in southern Arizona
Atmospheric monitoring for the H.E.S.S. experiment using a single scattering lidar
No full textThe High Energy Stereoscopic System (H.E.S.S.) is an array of 4 telescopes located in Namibia, which use the imaging atmospheric Cherenkov technique (IACT) to study astrophysical emission of gamma radiation in the energy window from 100 GeV to 50 TeV. The calorimetric nature of the technique means that the sensitivity and energy resolution of the instrument are highly dependent on atmospheric parameters. This thesis presents the findings of atmospheric measurements taken using a 355 nm single scattering lidar. The lidar wavelength is well matched to the maximum in the Cherenkov spectrum seen by the telescopes. Monte Carlo simulation software is presented which has been developed to calculate the integral vertical lidar ratio (the ratio of extinction to backscatter) for Mie scattering by aerosols assumed to be at the H.E.S.S. site. This is found to be 29 ± 3 steradians. This ratio is used with the Fernald method to derive the probability of transmission profile, and is also compared to other lidar analysis techniques; the Klett method and the multi-angle method. The results of all 3 methods are compared to the lidar manufacturer's closed-source analysis software, with which the Klett method is found to be in strongest agreement. A model that describes the relationship between the lidar ratio and the extinction is presented. Using this with the lidar manufacturer's extinction values provides a vertical lidar ratio profile which, for the first time, provides insight into the aerosol scattering layers present at the H.E.S.S. site in Namibia. Recommendations for improvement of this research, and suggestions for incorporation of data into the H.E.S.S. analysis, have been mad
The gamma-ray Cherenkov telescope for the Cherenkov telescope array
No full textThe Cherenkov Telescope Array (CTA) is a forthcoming ground-based observatory for very-high-energy gamma rays. CTA will consist of two arrays of imaging atmospheric Cherenkov telescopes in the Northern and Southern hemispheres, and will combine telescopes of different types to achieve unprecedented performance and energy coverage. The Gamma-ray Cherenkov Telescope (GCT) is one of the small-sized telescopes proposed for CTA to explore the energy range from a few TeV to hundreds of TeV with a field of view ≳ 8° and angular resolution of a few arcminutes. The GCT design features dual-mirror Schwarzschild-Couder optics and a compact camera based on densely-pixelated photodetectors as well as custom electronics. In this contribution we provide an overview of the GCT project with focus on prototype development and testing that is currently ongoing. We present results obtained during the first on-telescope campaign in late 2015 at the Observatoire de Paris-Meudon, during which we recorded the first Cherenkov images from atmospheric showers with the GCT multi-anode photomultiplier camera prototype. We also discuss the development of a second GCT camera prototype with silicon photomultipliers as photosensors, and plans toward a contribution to the realisation of CTA
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