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Title: Monte Carlo performance studies for the site selection of the Cherenkov Telescope Array

Abstract

The Cherenkov Telescope Array (CTA) represents the next generation of ground-based instruments for very-high-energy (VHE) gamma-ray astronomy, aimed at improving on the sensitivity of current-generation experiments by an order of magnitude and providing coverage over four decades of energy. The current CTA design consists of two arrays of tens of imaging atmospheric Cherenkov Telescopes, comprising Small, Medium and Large-Sized Telescopes, with one array located in each of the Northern and Southern Hemispheres. To study the effect of the site choice on the overall CTA performance and support the site evaluation process, detailed Monte Carlo simulations have been performed. These results show the impact of different site-related attributes such as altitude, night-sky background and local geomagnetic field on CTA performance for the observation of VHE gamma rays.

Authors:
 [1];  [2];  [3];  [2];  [1];  [1];  [4];  [5];  [6];  [3];  [7];  [8];  [1];  [5];  [6];  [7]
  1. Inst. for High Energy Physics (IFAE), Barcelona (Spain)
  2. Univ. Montpellier (France)
  3. Max Planck Inst. fur Kernphysik, Heidelberg (Germany)
  4. Istituto Nazionale di Fisica Nucleare (INFN), Torino (Italy)
  5. National Inst. of Nuclear Physics (INFN), Rome (Italy)
  6. Univ. of Sao Paulo (Brazil)
  7. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  8. Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1374282
Grant/Contract Number:
AC02-76SF00515; 653477
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Astroparticle Physics
Additional Journal Information:
Journal Volume: 93; Journal Issue: C; Journal ID: ISSN 0927-6505
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 79 ASTRONOMY AND ASTROPHYSICS; Monte Carlo simulations; Cherenkov Telescopes; IACT technique; Gamma rays; Cosmic rays

Citation Formats

Hassan, T., Arrabito, L., Bernlöhr, K., Bregeon, J., Cortina, J., Cumani, P., Di Pierro, F., Falceta-Goncalves, D., Lang, R. G., Hinton, J., Jogler, T., Maier, G., Moralejo, A., Morselli, A., Todero Peixoto, C. J., and Wood, M. Monte Carlo performance studies for the site selection of the Cherenkov Telescope Array. United States: N. p., 2017. Web. doi:10.1016/j.astropartphys.2017.05.001.
Hassan, T., Arrabito, L., Bernlöhr, K., Bregeon, J., Cortina, J., Cumani, P., Di Pierro, F., Falceta-Goncalves, D., Lang, R. G., Hinton, J., Jogler, T., Maier, G., Moralejo, A., Morselli, A., Todero Peixoto, C. J., & Wood, M. Monte Carlo performance studies for the site selection of the Cherenkov Telescope Array. United States. doi:10.1016/j.astropartphys.2017.05.001.
Hassan, T., Arrabito, L., Bernlöhr, K., Bregeon, J., Cortina, J., Cumani, P., Di Pierro, F., Falceta-Goncalves, D., Lang, R. G., Hinton, J., Jogler, T., Maier, G., Moralejo, A., Morselli, A., Todero Peixoto, C. J., and Wood, M. Wed . "Monte Carlo performance studies for the site selection of the Cherenkov Telescope Array". United States. doi:10.1016/j.astropartphys.2017.05.001. https://www.osti.gov/servlets/purl/1374282.
@article{osti_1374282,
title = {Monte Carlo performance studies for the site selection of the Cherenkov Telescope Array},
author = {Hassan, T. and Arrabito, L. and Bernlöhr, K. and Bregeon, J. and Cortina, J. and Cumani, P. and Di Pierro, F. and Falceta-Goncalves, D. and Lang, R. G. and Hinton, J. and Jogler, T. and Maier, G. and Moralejo, A. and Morselli, A. and Todero Peixoto, C. J. and Wood, M.},
abstractNote = {The Cherenkov Telescope Array (CTA) represents the next generation of ground-based instruments for very-high-energy (VHE) gamma-ray astronomy, aimed at improving on the sensitivity of current-generation experiments by an order of magnitude and providing coverage over four decades of energy. The current CTA design consists of two arrays of tens of imaging atmospheric Cherenkov Telescopes, comprising Small, Medium and Large-Sized Telescopes, with one array located in each of the Northern and Southern Hemispheres. To study the effect of the site choice on the overall CTA performance and support the site evaluation process, detailed Monte Carlo simulations have been performed. These results show the impact of different site-related attributes such as altitude, night-sky background and local geomagnetic field on CTA performance for the observation of VHE gamma rays.},
doi = {10.1016/j.astropartphys.2017.05.001},
journal = {Astroparticle Physics},
number = C,
volume = 93,
place = {United States},
year = {Wed May 03 00:00:00 EDT 2017},
month = {Wed May 03 00:00:00 EDT 2017}
}

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  • In this paper, we present studies for optimizing the next generation of ground-based imaging atmospheric Cherenkov telescopes (IACTs). Results focus on mid-sized telescopes (MSTs) for CTA, detecting very high energy gamma rays in the energy range from a few hundred GeV to a few tens of TeV. We describe a novel, flexible detector Monte Carlo package, FAST (FAst Simulation for imaging air cherenkov Telescopes), that we use to simulate different array and telescope designs. The simulation is somewhat simplified to allow for efficient exploration over a large telescope design parameter space. We investigate a wide range of telescope performance parametersmore » including optical resolution, camera pixel size, and light collection area. In order to ensure a comparison of the arrays at their maximum sensitivity, we analyze the simulations with the most sensitive techniques used in the field, such as maximum likelihood template reconstruction and boosted decision trees for background rejection. Choosing telescope design parameters representative of the proposed Davies–Cotton (DC) and Schwarzchild–Couder (SC) MST designs, we compare the performance of the arrays by examining the gamma-ray angular resolution and differential point-source sensitivity. We further investigate the array performance under a wide range of conditions, determining the impact of the number of telescopes, telescope separation, night sky background, and geomagnetic field. We find a 30–40% improvement in the gamma-ray angular resolution at all energies when comparing arrays with an equal number of SC and DC telescopes, significantly enhancing point-source sensitivity in the MST energy range. Finally, we attribute the increase in point-source sensitivity to the improved optical point-spread function and smaller pixel size of the SC telescope design.« less
  • The current generation of Imaging Atmospheric telescopes (IACTs) has demonstrated the power of this observational technique, providing high sensitivity and an angular resolution of {approx}0.1 deg. per event above an energy threshold of {approx}100 GeV. Planned future arrays of IACTs such as AGIS or CTA are aiming at significantly improving the angular resolution. Preliminary results have shown that values down to {approx}1' might be achievable. Here we present the results of Monte-Carlo simulations that aim to exploring the limits of angular resolution for next generation IACTs and investigate how the resolution can be optimised by changes to array and telescopemore » parameters such as the number of pixel in the camera, the field of view of the camera, the angular pixel size, the mirror size, and also the telescope separation.« less
  • The current generation of Imaging Atmospheric telescopes (IACTs) has demonstrated the power of the technique in an energy range between {approx}100 GeV up to several tens of TeV. At the high-energy end, these instruments are limited by photon statistics. Future arrays of IACTs such as CTA or AGIS are planned to push into the energy range beyond 100 TeV. Scientifically, this region is very promising, providing a probe of particles up to the 'knee' in the cosmic ray spectrum and access to an unexplored region in the spectra of nearby extragalactic sources. We present first results from our simulation studiesmore » of the high-energy part of a future IACT array and discuss the design parameters of such an array.« less
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