We review the variety of Active Galactic Nuclei (AGN) classes (so-calledAGN zoo") and classification schemes of galaxies by activity types based on their optical emission-line spectrum, as well as other parameters and other than optical wave-length ranges. A historical overview of discoveries of various types of active galaxies is given, including Seyfert galaxies, radio galaxies, QSOs, BL Lace...

We present a catalogue of ROSAT detected sources in the sample of spectroscopically selected Seyfert 1 and Seyfert 2 galaxies of Rafanelli et al. (1995). The catalogue contains 102 Seyfert 1 and 36 Seyfert 2 galaxies. The identification is based on X-ray contour maps overlaid on optical images taken from the Digitized Sky Survey. We have derived the basic spectral and timing properties of the X...

Far-infrared flux densities are newly extracted from the IRAS database for the RSA and CfA complete samples of Seyfert galaxies. These data are used to classify the Seyfert galaxies into those where the far-infrared continuum emission is dominated by the active galactic nucleus (AGN), circumnuclear starburst, or host galaxy. While AGN-dominant objects consist of comparable numbers of Seyfert 1 ...

We test whether there is a relation between the observed tidal interactions and Seyfert activity by imaging in HI twenty inactive galaxies at the same spatial resolution and detection threshold as the Seyfert sample. This control sample of inactive galaxies were closely matched in Hubble type, range in size and inclination, and have roughly comparable galaxy optical luminosity to the Seyfert ga...

The magnitude-limited catalog of the Southern Sky Redshift Survey (SSRS2), is used to characterize the properties of galaxies hosting Active Galactic Nuclei. Using emissionline ratios, we identify a total of 162 (3%) Seyfert galaxies out of the parent sample with 5399 galaxies. The sample contains 121 Seyfert 2 galaxies and 41 Seyfert 1. The SSRS2 Seyfert galaxies are predominantly in spirals o...

We estimated black hole masses for 9 Seyfert 1 and 13 Seyfert 2 galaxies in the Palomar and CfA bright Seyfert samples using the tight correlation between black hole mass and bulge velocity dispersion. Combining other 13 Seyfert 1s and 2 Seyfert 2s in these samples but with black hole masses measured recently by reverberation mapping and stellar/gas dynamics, we studied the correlations of blac...

In this paper, we present our preliminary results on Seyfert galaxies with circumnuclear/nuclear starburst(SB) activity. We have searched the recent available literature and found 76 active galaxies with clear evidence of nuclear SB activity, among which 16 are Seyfert 1s, 51 Seyfert 2s, and 9 LINERs. After studying the 51 Seyfert 2s, we find that those Seyfert 2s with hidden Seyfert 1 nuclei, ...

Galaxy interactions are studied in terms of the starburst-Seyfert connection. The starburst requires a high rate of gas supply. Since the efficiency for supplying the gas is high in a galaxy interaction, although the companion is not necessarily discernible, Seyfert galaxies with circumnuclear starbursts are expected to be interacting. Since the large amounts of circumnuclear gas and dust obscu...

The classical unified model is challenged by the presence of various kinds of Seyfert 2 galaxies. We assemble a sample composed of 243 nearby Seyfert galaxies with redshifts z ≤ 0.05 to test the unification scheme. The sample contains 94 broad line Seyfert 1s (BLS1s), 44 narrow line Seyfert 1s (NLS1s), 36 X-ray absorbed hidden broad line region (BLR) Seyfert 2s (HBLR S2s), 42 X-ray absorbed non...

We present optical spectra for new infrared Seyfert galaxies obtained with the 2.16m telescope at Bei-jing Astronomical Observatory (BAO). After wavelength and flux calibration, they are classified by the degree of nuclear activity: nine Seyfert 2 and three Seyfert 3 galaxies. In addition, by using the data from de Grijp et al.(1992), we find that (1) there exists a tight correlation between lu...