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Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2004

The nuclear region of low luminosity flat radio spectrum sources. II. Emission-line spectra

Résumé

We report on the spectroscopic study of 19 low luminosity Flat Radio Spectrum (LL FRS) sources selected from Marchã's et al. (\cite{March96}) 200 mJy sample. In the optical, these objects are mainly dominated by the host galaxy starlight. After correcting the data for this effect, we obtain a new set of spectra clearly displaying weak emission lines; such features carry valuable information concerning the excitation mechanisms at work in the nuclear regions of LL FRS sources. We have used a special routine to model the spectra and assess the intensities and velocities of the emission lines; we have analyzed the results in terms of diagnostic diagrams. Our analysis shows that 79% of the studied objects harbour a Low Ionization Nuclear Emission-line Region (or LINER) whose contribution was swamped by the host galaxy starlight. The remaining objects display a higher ionization spectrum, more typical of Seyferts; due to the poor quality of the spectra, it was not possible to identify any possible large Balmer components. The fact that we observe a LINER-type spectrum in LL FRS sources supports the idea that some of these objects could be undergoing an ADAF phase; in addition, such a low ionization emission-line spectrum is in agreement with the black hole mass values and sub-Eddington accretion rates published for some FRS sources.
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hal-03732497 , version 1 (29-07-2022)

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A. C. Gonçalves, M. Serote Roos. The nuclear region of low luminosity flat radio spectrum sources. II. Emission-line spectra. Astronomy and Astrophysics - A&A, 2004, 413, pp.97-105. ⟨hal-03732497⟩
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