The Fermi Large Area Telescope (LAT) revealed that blazars, representing the
most extreme radio-loud active galactic nuclei (AGN) population, dominate the
census of the gamma-ray sky, and a significant correlation was found between
radio and gamma-ray emission in the 0.1-100 GeV energy range. However, the
possible connection between radio and very high energy (VHE, E>0.1 TeV)
emission still remains elusive, owing to the lack of a homogeneous coverage of
the VHE sky. The main goal of this work is to quantify and assess the
significance of a possible connection between the radio emission on parsec
scale measured by the very long baseline interferometry (VLBI) and GeV-TeV
gamma-ray emission in blazars, which is a central issue for understanding the
blazar physics and the emission processes. We investigate the radio VLBI and
high energy gamma-ray emission by using two large and unbiased AGN samples
extracted from the first and second Fermi-LAT catalogs of hard gamma-ray
sources detected above 10 GeV (1FHL) and 50 GeV (2FHL). For comparison, we
perform the same correlation analysis by using the 0.1-300 GeV gamma-ray energy
flux provided by the third Fermi-LAT source catalog. We find that the
correlation strength and significance depend on the gamma-ray energy range with
a different behavior among the blazar sub-classes. Overall, the radio and
gamma-ray emission above 10 GeV turns out to be uncorrelated for the full
samples and for all of the blazar sub-classes with the exception of high
synchrotron peaked (HSP) objects, which show a strong and significant
correlation. On the contrary, when 0.1-300 GeV gamma-ray energies are
considered, a strong and significant correlation is found for the full blazar
sample as well as for all of the blazar sub-classes. We interpret and explain
this correlation behavior within the framework of the blazar spectral energy
distribution properties.Comment: 8 pages, 6 figures, 3 tables. Accepted for publication in Astronomy
  and Astrophysic

Costamante, L.

D'Ammando, F.

Giroletti, M.

Lico, R.

Orienti, M.

Pavlidou, V.

Tavecchio, F.

Astronomy and Astrophysics

English

arXiv

Context. With the advent of the Fermi Large Area Telescope (LAT) it was revealed that blazars, representing the most extreme radio-loud active galactic nuclei (AGN) population, dominate the census of the γ-ray sky, and a significant correlation was found between radio and γ-ray emission in the 0.1−100 GeV energy range. However, the possible connection between radio and very high energy (VHE, E> 0.1 TeV) emission still remains elusive, owing to the lack of a homogeneous coverage of the VHE sky. 
        Aims. The main goal of this work is to quantify and assess the significance of a possible connection between the radio emission on parsec scale measured by the very long baseline interferometry (VLBI) and GeV-TeV γ-ray emission in blazars, which is a central issue for understanding blazar physics and the emission processes in these objects.
        Methods. We investigate the radio VLBI and high energy γ-ray emission by using two large and unbiased AGN samples extracted from the first and second Fermi-LAT catalogs of hard γ-ray sources detected above 10 GeV (1FHL) and 50 GeV (2FHL). For comparison, we perform the same correlation analysis by using the 0.1−300 GeV γ-ray energy flux provided by the third Fermi-LAT source catalog (3FGL). We assess the correlation’s statistical significance by means of a method based on permutations of the luminosities, by taking into account the various observational biases, which may apparently enhance or spoil any intrinsic correlation. 
        Results. We find that the correlation strength and significance depend on the γ-ray energy range, with a different behavior among the blazar sub-classes. Overall, the radio and γ-ray emission above 10 GeV turns out to be uncorrelated for the full samples and for all of the blazar sub-classes with the exception of high synchrotron peaked (HSP) objects, which show a strong and significant correlation. On the contrary, when 0.1−300 GeV γ-ray energies are considered, a strong and significant correlation is found for the full blazar sample as well as for all of the blazar sub-classes. 
        Conclusions. We interpret and explain this correlation behavior within the framework of the blazar spectral energy distribution properties. In the most powerful blazars, which are in general of low synchrotron peaked type, the high energy emission component peaks at energies lower than those sampled by the LAT. On the contrary, in HSP blazars the part of the high energy spectrum affected by cooling effects is well beyond the energy range sampled by the LAT, showing a rising spectrum both in the 3FGL and 1FHL/2FHL energy ranges

R. Lico

M. Giroletti

M. Orienti

L. Costamante

V. Pavlidou

F. D’Ammando

F. Tavecchio

EDP Sciences OAI-PMH repository (1.2.0)

Exploring the connection between radio and GeV-TeV

Crossref

Exploring the connection between radio and GeV-TeV <i>γ</i>-ray emission in the 1FHL and 2FHL AGN samples

The Fermi Large Area Telescope (LAT) revealed that blazars, representing the
most extreme radio-loud active galactic nuclei (AGN) population, dominate the
census of the gamma-ray sky, and a significant correlation was found between
radio and gamma-ray emission in the 0.1-100 GeV energy range. However, the
possible connection between radio and very high energy (VHE, E>0.1 TeV)
emission still remains elusive, owing to the lack of a homogeneous coverage of
the VHE sky. The main goal of this work is to quantify and assess the
significance of a possible connection between the radio emission on parsec
scale measured by the very long baseline interferometry (VLBI) and GeV-TeV
gamma-ray emission in blazars, which is a central issue for understanding the
blazar physics and the emission processes. We investigate the radio VLBI and
high energy gamma-ray emission by using two large and unbiased AGN samples
extracted from the first and second Fermi-LAT catalogs of hard gamma-ray
sources detected above 10 GeV (1FHL) and 50 GeV (2FHL). For comparison, we
perform the same correlation analysis by using the 0.1-300 GeV gamma-ray energy
flux provided by the third Fermi-LAT source catalog. We find that the
correlation strength and significance depend on the gamma-ray energy range with
a different behavior among the blazar sub-classes. Overall, the radio and
gamma-ray emission above 10 GeV turns out to be uncorrelated for the full
samples and for all of the blazar sub-classes with the exception of high
synchrotron peaked (HSP) objects, which show a strong and significant
correlation. On the contrary, when 0.1-300 GeV gamma-ray energies are
considered, a strong and significant correlation is found for the full blazar
sample as well as for all of the blazar sub-classes. We interpret and explain
this correlation behavior within the framework of the blazar spectral energy
distribution properties

GIROLETTI, MARCELLO

ORIENTI, Monica

D'AMMANDO, FILIPPO

TAVECCHIO, Fabrizio

OA@INAF - Istituto Nazionale di Astrofisica

Exploring the connection between radio and GeV-TeV gamma-ray emission in the 1FHL and 2FHL AGN samples

Context. With the advent of the Fermi Large Area Telescope (LAT) it was revealed that blazars, representing the most extreme radio-loud active galactic nuclei (AGN) population, dominate the census of the Î3-ray sky, and a significant correlation was found between radio and Î3-ray emission in the 0.1-100 GeV energy range. However, the possible connection between radio and very high energy (VHE, E> 0.1 TeV) emission still remains elusive, owing to the lack of a homogeneous coverage of the VHE sky. Aims. The main goal of this work is to quantify and assess the significance of a possible connection between the radio emission on parsec scale measured by the very long baseline interferometry (VLBI) and GeV-TeV Î3-ray emission in blazars, which is a central issue for understanding blazar physics and the emission processes in these objects. Methods. We investigate the radio VLBI and high energy Î3-ray emission by using two large and unbiased AGN samples extracted from the first and second Fermi-LAT catalogs of hard Î3-ray sources detected above 10 GeV (1FHL) and 50 GeV (2FHL). For comparison, we perform the same correlation analysis by using the 0.1-300 GeV Î3-ray energy flux provided by the third Fermi-LAT source catalog (3FGL). We assess the correlation's statistical significance by means of a method based on permutations of the luminosities, by taking into account the various observational biases, which may apparently enhance or spoil any intrinsic correlation. Results. We find that the correlation strength and significance depend on the Î3-ray energy range, with a different behavior among the blazar sub-classes. Overall, the radio and Î3-ray emission above 10 GeV turns out to be uncorrelated for the full samples and for all of the blazar sub-classes with the exception of high synchrotron peaked (HSP) objects, which show a strong and significant correlation. On the contrary, when 0.1-300 GeV Î3-ray energies are considered, a strong and significant correlation is found for the full blazar sample as well as for all of the blazar sub-classes. Conclusions. We interpret and explain this correlation behavior within the framework of the blazar spectral energy distribution properties. In the most powerful blazars, which are in general of low synchrotron peaked type, the high energy emission component peaks at energies lower than those sampled by the LAT. On the contrary, in HSP blazars the part of the high energy spectrum affected by cooling effects is well beyond the energy range sampled by the LAT, showing a rising spectrum both in the 3FGL and 1FHL/2FHL energy ranges

Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna

Exploring the connection between radio and GeV-TeV Î3-ray emission in the 1FHL and 2FHL AGN samples

Exploring the connection between radio and GeV-TeV gamma-ray emission in
  the 1FHL and 2FHL AGN samples

Exploring the connection between radio and GeV-TeV gamma-ray emission in the 1FHL and 2FHL AGN samples

Abstract

Similar works

Full text

Available Versions

EDP Sciences OAI-PMH repository (1.2.0)

Crossref

OA@INAF - Istituto Nazionale di Astrofisica

Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna