Optical spectroscopy and polarization of a new sample of optically bright flat radio spectrum sources

Marchã, M. J. M.; Browne, I. W. A.; Impey, C. D.; Smith, Paul S.

doi:10.1093/mnras/281.2.425

Cited by 255 publications

(155 citation statements)

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“…the 200 mJy survey, Marchã et al 1996; the RGB survey, Laurent-Muehleisen et al 1998; the DXRBS survey, Perlman et al 1998;Landt et al 2001; the REX survey, Maccacaro et al 1998, Caccianiga et al 1999; the CLASS survey, Marchã et al 2001;Caccianiga et al 2001). In particular, we classify a source as BL Lac object if the 4000 Å break is absent (i.e.…”

Section: Optical Classificationmentioning

confidence: 99%

XMM-Newton spectroscopy of an X-ray selected sample of RL AGNs

Galbiati

Caccianiga

Maccacaro

et al. 2005

A&A

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Abstract. This paper presents the X-ray spectroscopy of an X-ray selected sample of 25 radio-loud (RL) AGNs extracted from the XMM-Newton Bright Serendipitous Survey (XBSS). The main goal of the work is to assess and study the origin of the X-ray spectral differences usually observed between radio-loud and radio-quiet (RQ) AGNs. To this end, a comparison sample of 53 RQ AGNs has been also extracted from the same XBSS sample and studied together with the sample of RL AGNs. Since there are many claims in the literature that RL AGNs have, on average, a flatter spectral index when compared to the RQ AGNs, we have focused the analysis on the distribution of the X-ray spectral indices of the power-law component that models the large majority of the spectra in both samples. We find that the mean X-ray energy spectral index is very similar in the 2 samples and close to α X ∼ 1. However, the intrinsic distribution of the spectral indices is significantly broader in the sample of RL AGNs. In order to investigate the origin of this difference, we have divided the RL AGNs into blazars (i.e. BL Lac objects and FSRQs) and "non-blazars" (i.e. radiogalaxies and SSRQs), on the basis of the available optical and radio information. Although the number of sources is small, we find strong evidence that the broad distribution observed in the RL AGN sample is mainly due to the presence of the blazars. Furthermore, within the blazar class we have found a link between the X-ray spectral index and the value of the radio-to-X-ray spectral index (α RX ) suggesting that the observed X-ray emission is directly connected to the emission of the relativistic jet. This trend is not observed among the "non-blazars" RL AGNs. This favours the hypothesis that, in these latter sources, the X-ray emission is not significantly influenced by the jet emission and it has probably an origin similar to the RQ AGNs. Overall, the results presented here indicate that the observed distribution of the X-ray spectral indices in a given sample of RL AGNs is strongly dependent on the amount of relativistic beaming present in the selected sources, i.e. on the relative fraction of blazars and "non-blazars".

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Section: Optical Classificationmentioning

confidence: 99%

XMM-Newton spectroscopy of an X-ray selected sample of RL AGNs

Galbiati

Caccianiga

Maccacaro

et al. 2005

A&A

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“…A spectroscopic analysis in the optical band is able to show the mutual strength of these two components. At this purpose the Ca H&K break absorption (Stocke et al 1991;Marcha et al 1996), if present, is one of the most frequently investigated features. A weak non-thermal continuum emission, reflecting in a very sharp Ca H&K break, is the footprint of a weak central engine and probably shares little with the blazar nature, characterized by much more extreme properties.…”

Section: Validation Of Blazar Candidatesmentioning

confidence: 99%

New blazars from the cross-match of recent multi-frequency catalogs

Maselli

Massaro

D’Abrusco

et al. 2015

Astrophys Space Sci

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Blazars are radio-loud active galactic nuclei well known for their non thermal emission spanning a wide range of frequencies. The Roma-BZCAT is, to date, the most comprehensive list of these sources. We performed the cross-match of several catalogs obtained from recent surveys at different frequencies to search for new blazars. We cross-matched the 1 st Swift XRT Point Source catalog with the spectroscopic sample of the 9 th Data Release of the Sloan Digital Sky Survey. Then, we performed further cross-matches with the catalogs corresponding to the Faint Images of the Radio Sky at Twenty cm survey and to the AllWISE Data re- lease, focusing on sources with infrared colors similar to those of confirmed γ-ray blazars included in the Second Fermi-LAT catalog. As a result, we obtained a preliminary list of objects with all the elements needed for a proper blazar classification according to the prescriptions of the Roma-BZCAT. We carefully investigated additional properties such as their morphology and the slope of their spectral energy distribution in the radio domain, the features shown in their optical spectrum, and the luminosity in the soft X rays to exclude generic active galactic nuclei and focus on authentic blazar-like sources. At the end of our screening we obtained a list of 15 objects with firmly established blazar properties.

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“…Typically, a source is classified as an FSRQ if it shows emission lines with equivalent widths |W λ | > 5 Å, while it is classified as a BL Lac if the equivalent widths are |W λ | < 5 Å (e.g. [2,3]). This can be understood as FSRQs having a higher accretion rate than BL Lacs (and hence more luminous accretion discs), which leads to a greater ionization of the broad and narrow line regions (see e.g.…”

Section: Introductionmentioning

confidence: 99%

Characterising the Fermi-LAT BCUs: Optical Spectroscopy and Neural Networks

Soelen¹,

Marais²,

Britto³

et al. 2017

Proceedings of 4th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA 2016)

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The Fermi-LAT telescope has provided an unprecedented view of the GeV gamma-ray sky since its launch in 2008. The latest Fermi-LAT catalogue of Active Galactic Nuclei lists 1591 sources associated with AGN, of which 460 are classified as blazar candidates of uncertain type (BCU). The characterisation of the physical properties of these BCU sources is important for observational cosmology and fundamental physics, as these sources and their environments constitute a natural laboratory to study particle acceleration and matter/radiation interactions in extreme conditions. Of particular interest is the search for new and interesting/unusual sources that may be observable at very high energies by ground-based imaging atmospheric Cherenkov telescopes. Based on the observed gamma-ray properties, a number of machine learning techniques are being investigated to classify these sources. However, the classification of a blazar as a FSRQ or BL Lac depends on the optical spectral properties. Here we discuss the work that we have thus far undertaken to optically characterise a selection of sources as well as future plans to undertake classification to help calibrate an artificial neural network method.

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Optical spectroscopy and polarization of a new sample of optically bright flat radio spectrum sources

Cited by 255 publications

References 0 publications

XMM-Newton spectroscopy of an X-ray selected sample of RL AGNs

XMM-Newton spectroscopy of an X-ray selected sample of RL AGNs

New blazars from the cross-match of recent multi-frequency catalogs

Characterising the Fermi-LAT BCUs: Optical Spectroscopy and Neural Networks

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