353 research outputs found
Starbursts and black hole masses in X-shaped radio galaxies: Signatures of a merger event?
We present new spectroscopic identifications of 12 X-shaped radio galaxies
and use the spectral data to derive starburst histories and masses of the
nuclear supermassive black holes in these galaxies. The observations were done
with the 2.1-m telescope of the Observatorio Astron\'omico Nacional at San
Pedro M\'artir, M\'exico. The new spectroscopic results extend the sample of
X-shaped radio galaxies studied with optical spectroscopy. We show that the
combined sample of the X-shaped radio galaxies has statistically higher
black-hole masses and older episodes of star formation than a control sample of
canonical double-lobed radio sources with similar redshifts and luminosities.
The data reveal enhanced star-formation activity in the X-shaped sample on the
timescales expected in galactic mergers. We discuss the results obtained in the
framework of the merger scenario.Comment: 9 pages, 10 figures, accepted for publication in Astronomy &
Astrophysic
Understanding the relationship between the environment of the black hole and the radio jet: optical spectroscopy of compact AGN
We aim to investigate the relationship between radio jet activity on
parsec-scales and the characteristics of both the bright active galactic nuclei
(AGN) and their broad line regions (BLR). For this purpose, we combine 2cm Very
Long Baseline Array observations of AGN with their optical spectral
observations. This would enable us to investigate the optical spectra of a set
of 172 relativistically beamed, flat-spectrum AGN with the nuclear disk
oriented near to the plane of sky. Here, we present first results from optical
spectroscopic observations of the brightest AGN from the 2 cm VLBA survey, and
show a diversity of their spectral morphologies.Comment: 2 pages, to be published in the Proceedings of "Multiwavelength AGN
Surveys", Cozumel, Dec 8 - 12, 200
Radio-optical scrutiny of the central engine in compact AGN
We combine Very-Long-Baseline Interferometry (VLBI) data for active
galactic nuclei (AGN) available from the Very Large Baseline Array (VLBA) 2 cm
imaging survey and optical spectroscopy to investigate the relationships in the
emission-line region--central engine--radio jet system. Here, we present the
diversity of spectral types among the brightest AGN in our sample. We also
discuss correlations between the mass of the central engine and properties of
the parsec-scale radio jet for 24 AGN selected by the presence of H
broad-emission lines in their spectra.Comment: 4 pages, 5 figures, to appear in the proceedings of the Workshop on
"Multiband Approach to AGN" held in Bonn (Germany), 30 September - 2 October
2004, to be published in "Memorie della Societa Astronomica Italiana
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