EAS Publications Series

Issue		EAS Publications Series Volume 10, 2003 JENAM 2002, Galactic & Stellar Dynamics
Page(s)		211
DOI		10.1051/eas:2003152

Galactic & Stellar Dynamics
C. Boily, P. Patsis, S. Portegies Zwart, R. Spurzem and C. Theis (eds)
EAS Publications Series, Vol. 10, 2003
DOI: 10.1051/eas:2003152

Spectroscopic study of low luminosity BL Lac type objects

M. Serote Roos¹ and A.C. Gonçalves^{1, 2}

¹ CAAUL, Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal
² ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany

Abstract
We have examined the spectroscopic properties of a sample of 19 optically bright, low luminosity core-dominated radio sources; this sample was expected to contain a high fraction of objects observed at small angles to the line-of-sight (blazar-like objects). Our study focuses on the properties - stellar populations and optical emission-line spectra - of such nuclei. Stellar population synthesis shows that their nuclear populations are composed, in a general way, of old stars of solar metallicity or lower; the dust content is weak. After subtraction of the stellar contribution, we are left with a set of nuclear emission-line spectra; their analysis shows that most of the objects harbour a Low Ionisation Nuclear Emission Region (or LINER), whose contribution was highly diluted by the host galaxy starlight. Such a low ionisation spectrum is in agreement with the black hole mass values and sub-Eddington accretion rates published for some BL Lacs; also, the stellar populations derived in this study are in agreement with those usually found in LINERs. Our findings give strength to a unifying picture involving low luminosity blazar-like objects and FR I radio-galaxies (which usually display LINER-type spectra).

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