On the redshift of the gamma-ray blazar PKS 0447-439: Optical spectroscopy using Gemini observations with high S/N ratio

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Abstract: The BL-Lac blazar PKS 0447-439 was detected at very high energy gamma-rays by HESS following the discovery by Fermi-LAT. The lack of both emission and absorption lines in BL-Lacs make the estimation of their redshifts very difficult. Modeling the drop in gamma-ray spectra it was possib...

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Autores principales: Rovero, A.C., Donzelli, Carlos, Muriel, Hernán, Cilis, A., Pichel, A.C.
Formato: conferenceObject
Lenguaje:Inglés
Publicado: Centro Brasileiro de Pesquisas Físicas (CBPF) 2021
Materias:
Gamma-ray blazars
Gamma rays
Blazars
Optical spectroscopy
BL-Lac objects
Redshift
Acceso en línea:http://hdl.handle.net/11086/18971
Aporte de:
Repositorio Digital Universitario (UNC) de Universidad Nacional de Córdoba
id I10-R14111086-18971
record_format dspace
institution Universidad Nacional de Córdoba
institution_str I-10
repository_str R-141
collection Repositorio Digital Universitario (UNC)
language Inglés
topic Gamma-ray blazars
Gamma rays
Blazars
Optical spectroscopy
BL-Lac objects
Redshift
spellingShingle Gamma-ray blazars
Gamma rays
Blazars
Optical spectroscopy
BL-Lac objects
Redshift
Rovero, A.C.
Donzelli, Carlos
Muriel, Hernán
Cilis, A.
Pichel, A.C.
On the redshift of the gamma-ray blazar PKS 0447-439: Optical spectroscopy using Gemini observations with high S/N ratio
topic_facet Gamma-ray blazars
Gamma rays
Blazars
Optical spectroscopy
BL-Lac objects
Redshift
description Abstract: The BL-Lac blazar PKS 0447-439 was detected at very high energy gamma-rays by HESS following the discovery by Fermi-LAT. The lack of both emission and absorption lines in BL-Lacs make the estimation of their redshifts very difficult. Modeling the drop in gamma-ray spectra it was possible to have an estimation of redshift for PKS 0447-439 of z approx 0.2, which is compatible with the value z=0.205 reported by the identification of Ca II absorption lines in optical spectra. By the identification of a weak line of Mg II using spectra with average signal-to-noise S/N approx 80, it has been recently reported a lower limit for the redshift of this blazar of z<=1.246. Triggered by this controversy, we have proposed new optical observations with the Gemini South telescope to perform further spectroscopic analysis with very high S/N ratio (approx 200-500). In this work we present a new optical spectrum of PKS 0447-439, and report on the analysis and results of such observations. Even with this significantly high quality signal we were not able to identify any spectral features to allow an estimation of the redshift. In agreement with other recent studies, we identify the Mg II line reported previously as originated in the Earth´s atmosphere, and conclude the lower limit of the redshift is incorrect. More interestingly, we could not identify the Ca II absorption lines used to report a redshift of 0.205.
format conferenceObject
author Rovero, A.C.
Donzelli, Carlos
Muriel, Hernán
Cilis, A.
Pichel, A.C.
author_facet Rovero, A.C.
Donzelli, Carlos
Muriel, Hernán
Cilis, A.
Pichel, A.C.
author_sort Rovero, A.C.
title On the redshift of the gamma-ray blazar PKS 0447-439: Optical spectroscopy using Gemini observations with high S/N ratio
title_short On the redshift of the gamma-ray blazar PKS 0447-439: Optical spectroscopy using Gemini observations with high S/N ratio
title_full On the redshift of the gamma-ray blazar PKS 0447-439: Optical spectroscopy using Gemini observations with high S/N ratio
title_fullStr On the redshift of the gamma-ray blazar PKS 0447-439: Optical spectroscopy using Gemini observations with high S/N ratio
title_full_unstemmed On the redshift of the gamma-ray blazar PKS 0447-439: Optical spectroscopy using Gemini observations with high S/N ratio
title_sort on the redshift of the gamma-ray blazar pks 0447-439: optical spectroscopy using gemini observations with high s/n ratio
publisher Centro Brasileiro de Pesquisas Físicas (CBPF)
publishDate 2021
url http://hdl.handle.net/11086/18971
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