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July 29, 2015 to August 6, 2015
World Forum
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Redshift measurement of Fermi Blazars for the Cherenkov Telescope Array

Jul 30, 2015, 3:30 PM
Mississippi Foyer (World Forum)

Mississippi Foyer

World Forum

Churchillplein 10 2517 JW Den Haag The Netherlands
Board: 75
Poster contribution GA-EX Poster 1 GA


Dr Paolo Goldoni (APC/CEA-Irfu)


Blazars are active galactic nuclei, and the most numerous High Energy (HE) and Very High Energy (VHE)gamma-ray emitters. Their optical emission is often dominated by non-thermal, and, in the case of BL Lacs, featureless continuum radiation. This renders the determination of their redshift extremely difficult. Indeed as of today only about 50% of gamma-ray blazars have a measured spectroscopic redshift. The knowledge of redshift is fundamental because it allows the precise modeling of the VHE emission and also of its interaction with the extragalactic background light (EBL). The beginning of the Cherenkov Telescope Array (CTA) operations in the near future will allow detecting several hundreds of new BL Lacs. Using the first Fermi catalogue of sources above 10 GeV (1FHL), we performed simulations which demonstrate that at least half of the 1FHL BL Lacs detectable by CTA will not have a measured redshift. Indeed the organization of observing campaigns to measure the redshift of these blazars has been recognized as a necessary support for the AGN Key Science Project of CTA. Taking advantage of the recent success of an X-shooter GTO observing campaign, we thus devised an observing campaign to measure the redshifts of as many as possible of these candidates. The main characteristic of this campaign with respect to previous ones will be the use of higher resolution spectrographs and of 8 meter class telescopes. We are starting submitting proposals for our observations. In this paper we will briefly describe the selection of the candidates, the characteristics of our observation and the expected results.
Collaboration CTA
Registration number following "ICRC2015-I/" 814

Primary author

Dr Paolo Goldoni (APC/CEA-Irfu)


Dr Catherine Boisson (LUTH/OBSPM) Dr David Williams (UCSC) Dr Elina Lindfors (Tuorla Observatory) Garret Cotter (Oxford Astrophysics) Santiago Pita (APC)

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