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

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...

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Detalles Bibliográficos
Publicado: 2013
Materias:
BL-Lac objects
Gamma-ray blazars
Optical spectroscopy
Redshift
Cosmic rays
Cosmology
Earth atmosphere
Magnesium compounds
Signal to noise ratio
Spectroscopic analysis
Spectrum analysis
Ultraviolet spectroscopy
Blazars
Gamma ray spectra
Optical observations
Red shift
Spectral feature
Very high energies
Gamma rays
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_97885890_v2013-October_n_p_Rovero
http://hdl.handle.net/20.500.12110/paper_97885890_v2013-October_n_p_Rovero
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling paper:paper_97885890_v2013-October_n_p_Rovero2023-06-08T16:39:06Z On the redshift of the gamma-ray blazar PKS 0447-439: Optical spectroscopy using Gemini observations with high S/N ratio BL-Lac objects Gamma-ray blazars Optical spectroscopy Redshift Cosmic rays Cosmology Earth atmosphere Magnesium compounds Signal to noise ratio Spectroscopic analysis Spectrum analysis Ultraviolet spectroscopy BL-Lac objects Blazars Gamma ray spectra Optical observations Optical spectroscopy Red shift Spectral feature Very high energies Gamma rays 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∼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∼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 (∼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. © 2013 Sociedade Brasileira de Fisica. All Rights Reserved. 2013 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_97885890_v2013-October_n_p_Rovero http://hdl.handle.net/20.500.12110/paper_97885890_v2013-October_n_p_Rovero
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic BL-Lac objects
Gamma-ray blazars
Optical spectroscopy
Redshift
Cosmic rays
Cosmology
Earth atmosphere
Magnesium compounds
Signal to noise ratio
Spectroscopic analysis
Spectrum analysis
Ultraviolet spectroscopy
BL-Lac objects
Blazars
Gamma ray spectra
Optical observations
Optical spectroscopy
Red shift
Spectral feature
Very high energies
Gamma rays
spellingShingle BL-Lac objects
Gamma-ray blazars
Optical spectroscopy
Redshift
Cosmic rays
Cosmology
Earth atmosphere
Magnesium compounds
Signal to noise ratio
Spectroscopic analysis
Spectrum analysis
Ultraviolet spectroscopy
BL-Lac objects
Blazars
Gamma ray spectra
Optical observations
Optical spectroscopy
Red shift
Spectral feature
Very high energies
Gamma rays
On the redshift of the gamma-ray blazar PKS 0447-439: Optical spectroscopy using Gemini observations with high S/N ratio
topic_facet BL-Lac objects
Gamma-ray blazars
Optical spectroscopy
Redshift
Cosmic rays
Cosmology
Earth atmosphere
Magnesium compounds
Signal to noise ratio
Spectroscopic analysis
Spectrum analysis
Ultraviolet spectroscopy
BL-Lac objects
Blazars
Gamma ray spectra
Optical observations
Optical spectroscopy
Red shift
Spectral feature
Very high energies
Gamma rays
description 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∼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∼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 (∼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. © 2013 Sociedade Brasileira de Fisica. All Rights Reserved.
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
publishDate 2013
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_97885890_v2013-October_n_p_Rovero
http://hdl.handle.net/20.500.12110/paper_97885890_v2013-October_n_p_Rovero
_version_ 1769175807743229952

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