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Optical spectroscopy of Blazars for the Cherenkov Telescope Array
- Publication Year :
- 2020
- Publisher :
- arXiv, 2020.
-
Abstract
- Context. Blazars are the most numerous class of High Energy (HE; E about 50 MeV - few 100 GeV) and Very High Energy (VHE; E about 100 GeV - 10 TeV) gamma-ray emitters. As of today, a measured spectroscopic redshift is available for only about 50% of gamma-ray BL Lacs, mainly due to the difficulty of measuring reliable redshifts from their nearly featureless, continuum-dominated optical spectra. The knowledge of the redshift is fundamental for understanding the emission from blazars, for population studies and also for indirect studies of the extragalactic background light and searches for Lorentz invariance violation and axion-like particles using blazars. Aims. This paper is the first of a series of papers which aim to measure the redshift of a sample of blazars likely to be detected with the upcoming Cherenkov Telescope Array (CTA), a ground based gamma-ray observatory. Methods. Monte Carlo simulations were performed to select those hard spectrum gamma-ray blazars detected with the Fermi-LAT telescope still lacking redshift measurements but likely to be detected by CTA in 30 hours of observing time or less. Optical observing campaigns involving deep imaging and spectroscopic observations were organised to efficiently constrain their redshifts. We performed deep medium to high resolution spectroscopy of nineteen blazar optical counterparts using the ESI spectrograph at Keck, the RSS spectrograph at the SALT telescope, and the EFOSC2 spectrograph at the ESO NTT. We searched systematically for spectral features and, when possible, we estimated the contribution of the host galaxy to the total flux. Results. We measured eleven firm spectroscopic redshifts with values ranging from 0.1116 to 0.482. one tentative redshift, three redshift lower limits including one at z > 0.449 and another at z > 0.868. There were four objects found to have featureless spectra.<br />Accepted by Astronomy & Astrophysics
- Subjects :
- [PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE]
gamma-rays: galaxies
Astrophysics::High Energy Astrophysical Phenomena
Population
FOS: Physical sciences
Astrophysics
Astrophysics::Cosmology and Extragalactic Astrophysics
01 natural sciences
law.invention
Telescope
law
0103 physical sciences
Astrophysics::Solar and Stellar Astrophysics
education
Blazar
010303 astronomy & astrophysics
Spectrograph
Astrophysics::Galaxy Astrophysics
Physics
High Energy Astrophysical Phenomena (astro-ph.HE)
education.field_of_study
010308 nuclear & particles physics
Astrophysics::Instrumentation and Methods for Astrophysics
Astronomy and Astrophysics
gamma-rays galaxies
BL Lacertae objects: general
Cherenkov Telescope Array
Astrophysics - Astrophysics of Galaxies
Galaxy
Redshift
[PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Extragalactic background light
Space and Planetary Science
Astrophysics of Galaxies (astro-ph.GA)
galaxies: distances and redshifts
Astrophysics - High Energy Astrophysical Phenomena
Subjects
Details
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....f7c7d7cf6b80fc1146c7a30fcab1b50a
- Full Text :
- https://doi.org/10.48550/arxiv.2012.05176