A new combined data of 5 well known type 1 AGN are probed with a novel hybrid method in a search for oscillatory behavior. Additional analysis of artificial light curves obtained from the coupled oscillatory models gives confirmation for detected periods that could have physical background. We find periodic variations in the long-term light curves of 3C 390.3, NGC 4151, NGC 5548 and E1821+643, with correlation coefficients larger than 0.6. We show that oscillatory patterns of two binary black hole candidates NGC 5548 and E1821+643 corresponds to qualitatively different dynamical regimes of chaos and stability, respectively. We demonstrate that absence of oscillatory patterns in Arp 102B could be due to a weak coupling between oscillatory mechanisms. This is the first good evidence that 3C 390.3 and Arp 102B, categorized as double-peaked Balmer line objects, have qualitative different dynamics. Our analysis shows a novelty in the oscillatory dynamical patterns of the light curves of these type 1 AGN.

We present a full study of deep optical long-slit spectroscopy, and deep broad-band photometry of NGC 6086. We cover up to at least 3 re in spectroscopy and 5 re in photometry (re ≈ 22 arcsec in our V-band photometry). The envelope first appears in the photometric profile around 23 arcsec and the velocity dispersion, age, metallicity and Mg2 indices all show changes starting at about this radius suggesting that we are seeing two separate structures (ellipsoid and envelope) with different properties in the data. We do not find the Kinematic Decoupled Core (KDC) reported in Carter et al. (1999) . The velocity dispersion profile rises from 300 km s−1 in the centre to 600 km s−1 at 40 arcsec, a similar tendency to that previously observed in NGC 6166 (Bender et al. 2015). Populations indicate a trend from old, metal-rich stars to younger metal-poorer ones as the radius increases. Line-index analysis indicates that the α element proportion is high at all radii and that the Mg2 index declines relatively steeply with radius. The photometry shows the extended envelope with Sérsic index of 0.6 and flat colour gradients. Previous measurements of the velocity dispersion of the galaxies in the cluster A2162 are in the range 300-420 km s−1 for only around 40 member galaxies, but there appears to be a radial discontinuity in the distribution of galaxies and a flattish distribution in radial velocity implying that the kinematics of this cluster requires further investigation.

Abstract. We have carried out photometry and spectroscopy on a sample of 10 cD galaxies. The photometry shows, in general, fairly flat and red profile colours, implying an envelope with the same stellar population as the central galaxy. This may indicate a possible primordial origin for both structures, consistent with ideas of downsizing. Preliminary spectroscopic results are generally in agreement with the photometry, with for example younger populations at large radii for A2199, but A2589 has only younger populations.

cD galaxies are supergiant elliptical galaxies found generally in the central parts of rich clusters, which have an extended halo-like component (envelope) in addition to the underlying de Vaucouleurs-Sérsic elliptical galaxy-like component. This envelope can extend to radial distances of > 500 kpc (Oemler 1976, Schombert 1988). There have been many theories to explain the formation of these envelopes. These include tidal stripping, where material is stripped from neighbouring galaxies; mergers and fusions, where the envelope is built up hierarchically by successive mergers with large and small galaxies; primordial origin, where the envelope is formed at the same time as the rest of the elliptical galaxy (which appears to be related to theories of early formation of the largest galaxies); and cooling flows: in clusters with X-ray emission there is often a minimum temperature in the centre interpreted as a flow of cooling gas towards the centre of the cluster, where the gas can cool sufficiently, forming stars. The colours of the stars in the envelopes will be affected by their process of formation and subsequent evolution.