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Redshift determination of blazars for the Cherenkov Telescope Array

Published online by Cambridge University Press:  11 September 2023

E. Kasai Open the ORCID record for E. Kasai [Opens in a new window] ,
P. Goldoni ,
S. Pita ,
C. Boisson Open the ORCID record for C. Boisson [Opens in a new window] ,
M. Backes Open the ORCID record for M. Backes [Opens in a new window] ,
G. Cotter ,
F. D’Ammando  and
B. van Soelen
E. Kasai
Affiliation:
Department of Physics, Chemistry & Material Science, University of Namibia, Private Bag 13301, Windhoek, Namibia
P. Goldoni
Affiliation:
Université Paris Cité, CNRS, CEA, Astroparticule et Cosmologie, F-75013 Paris, France
S. Pita
Affiliation:
Université Paris Cité, CNRS, Astroparticule et Cosmologie, F-75013 Paris, France
C. Boisson
Affiliation:
LUTH, Observatoire de Paris, PSL Research University, CNRS, Université Paris Cité, Meudon, France
M. Backes
Affiliation:
Department of Physics, Chemistry & Material Science, University of Namibia, Private Bag 13301, Windhoek, Namibia Centre for Space Research, North-West University, Potchefstroom 2520, South Africa
G. Cotter
Affiliation:
University of Oxford, Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH, United Kingdom
F. D’Ammando
Affiliation:
INAF - Istituto di Radioastronomia, Via Gobetti 101, I-40129 Bologna, Italy
B. van Soelen
Affiliation:
Department of Physics, University of the Free State, Bloemfontein 9300, South Africa
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Abstract

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Blazars are the most numerous type of observed high-energy gamma-ray emitters. However, their emission mechanisms and population properties are still not well-understood. Crucial to this understanding are their cosmological redshifts, which are often not easy to obtain. This presents a great challenge to the next-generation ground-based observatory for very-high-energy gamma rays, the Cherenkov Telescope Array (CTA), which aims to detect a large number of distant blazars to study their intrinsic emission properties and to place tight constraints on the extragalactic background light density, amongst others. The successful investigation of these subjects needs a precise redshift determination. Motivated by these challenges, the CTA redshift task force initiated more than 3 years ago a spectroscopic observing program using some of the largest optical and infrared telescopes to measure the redshifts of a large fraction of blazars that are likely to be detected with CTA. In this proceedings, we give an overview of the CTA redshift task force, discuss some of the difficulties associated with measuring the redshifts of blazars and present our sample selection and observing strategies. We end the proceedings with reporting selected results from the program, the on-going collaborative efforts and our plans for the future.

Keywords

galaxies: activeBL Lacertae objects: generalgalaxies: distances and redshiftsgamma-rays: galaxies
Type
Contributed Paper
Information
Proceedings of the International Astronomical Union , Volume 17 , Symposium S375: The Multimessenger Chakra of Blazar Jets , December 2021 , pp. 96 - 100
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Copyright
© The Author(s), 2023. Published by Cambridge University Press on behalf of International Astronomical Union

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