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Southern African Large Telescope Spectroscopy of BL Lacs for the CTA project

Kasai, E. ; Goldoni, P. ; Backes, M. ; Cotter, G. ; Pita, S. ; Boisson, C. ; Williams, D. A. ; D'ammando, F. ; Lindfors, E. and Barres de Almeida, U. , et al. (2022) In Proceedings of Science 395.
Abstract
In the last two decades, very-high-energy gamma-ray astronomy has reached maturity: over 200 sources have been detected, both Galactic and extragalactic, by ground-based experiments. At present, Active Galactic Nuclei (AGN) make up about 40% of the more than 200 sources detected at very high energies with ground-based telescopes, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth and three quarters of which are classified as high-frequency peaked BL Lac objects. One challenge to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGN to be... (More)
In the last two decades, very-high-energy gamma-ray astronomy has reached maturity: over 200 sources have been detected, both Galactic and extragalactic, by ground-based experiments. At present, Active Galactic Nuclei (AGN) make up about 40% of the more than 200 sources detected at very high energies with ground-based telescopes, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth and three quarters of which are classified as high-frequency peaked BL Lac objects. One challenge to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGN to be detected with the future Cherenkov Telescope Array (CTA) observatory will have no spectroscopic redshifts, compromising the reliability of BL Lac population studies, particularly of their cosmic evolution. We started an effort in 2019 to measure the redshifts of a large fraction of the AGN that are likely to be detected with CTA, using the Southern African Large Telescope (SALT). In this contribution, we present two results from an on-going SALT program focused on the determination of BL Lac object redshifts that will be relevant for the CTA observatory. © Copyright owned by the author(s) under the terms of the Creative Commons. (Less)
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author collaboration
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
keywords
Cosmic rays, Cosmology, Gamma rays, Observatories, Telescopes, Active galactic nuclei, Blazars, Cherenkov telescope arrays, Ground based, Ground-based telescopes, Line of Sight, Red shift, Southern African Large Telescopes, Very high energies, Very-high-energy gamma-ray astronomies, Active Galactic Nuclei
host publication
37th International Cosmic Ray Conference (ICRC2021) - GAI - Gamma Ray Indirect
series title
Proceedings of Science
volume
395
article number
881
external identifiers
  • scopus:85145018881
ISSN
1824-8039
DOI
10.22323/1.395.0881
language
English
LU publication?
yes
id
3fed2e9d-8216-4b92-bd06-4d5786ca1689
date added to LUP
2023-01-16 12:43:28
date last changed
2024-04-03 18:20:22
@inproceedings{3fed2e9d-8216-4b92-bd06-4d5786ca1689,
  abstract     = {{In the last two decades, very-high-energy gamma-ray astronomy has reached maturity: over 200 sources have been detected, both Galactic and extragalactic, by ground-based experiments. At present, Active Galactic Nuclei (AGN) make up about 40% of the more than 200 sources detected at very high energies with ground-based telescopes, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth and three quarters of which are classified as high-frequency peaked BL Lac objects. One challenge to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGN to be detected with the future Cherenkov Telescope Array (CTA) observatory will have no spectroscopic redshifts, compromising the reliability of BL Lac population studies, particularly of their cosmic evolution. We started an effort in 2019 to measure the redshifts of a large fraction of the AGN that are likely to be detected with CTA, using the Southern African Large Telescope (SALT). In this contribution, we present two results from an on-going SALT program focused on the determination of BL Lac object redshifts that will be relevant for the CTA observatory. © Copyright owned by the author(s) under the terms of the Creative Commons.}},
  author       = {{Kasai, E. and Goldoni, P. and Backes, M. and Cotter, G. and Pita, S. and Boisson, C. and Williams, D. A. and D'ammando, F. and Lindfors, E. and Barres de Almeida, U. and Max-Moerbeck, W. and Navarro-Aranguiz, V. and Becerra-Gonzalez, J. and Hervet, O. and Lenain, J. -P. and Sol, H. and Wagner, S. and Abdalla, H. and Carlile, C. and Dravins, D. and Zmija, A.}},
  booktitle    = {{37th International Cosmic Ray Conference (ICRC2021) - GAI - Gamma Ray Indirect}},
  issn         = {{1824-8039}},
  keywords     = {{Cosmic rays; Cosmology; Gamma rays; Observatories; Telescopes; Active galactic nuclei; Blazars; Cherenkov telescope arrays; Ground based; Ground-based telescopes; Line of Sight; Red shift; Southern African Large Telescopes; Very high energies; Very-high-energy gamma-ray astronomies; Active Galactic Nuclei}},
  language     = {{eng}},
  series       = {{Proceedings of Science}},
  title        = {{Southern African Large Telescope Spectroscopy of BL Lacs for the CTA project}},
  url          = {{http://dx.doi.org/10.22323/1.395.0881}},
  doi          = {{10.22323/1.395.0881}},
  volume       = {{395}},
  year         = {{2022}},
}