We present the discovery of a triplet of emission-line nuclei in the disturbed disk galaxy NGC 3341, based on archival data from the Sloan Digital Sky Survey and new observations from the Keck Observatory. This galaxy contains two offset nuclei within or projected against its disk, at projected distances of 5.1 and 8.4 kpc from its primary nucleus and at radial velocity separation of less than 200 km/s from the primary. These appear to be either dwarf ellipticals or the bulges of low-mass spirals whose disks have already been stripped off while merging into the primary galaxy. The inner offset nucleus has a Seyfert 2 spectrum and a stellar velocity dispersion of 70+/-7 km/s. The outer offset nucleus has very weak emission lines consistent with a LINER classification, and the primary nucleus has an emission-line spectrum close to the boundary between LINER/HII composite systems and HII nuclei; both may contain accreting massive black holes, but the optical classifications alone are ambiguous. The detection of an offset active nucleus in NGC 3341 provides a strong suggestion that black hole accretion episodes during minor mergers can be triggered in the nuclei of dwarf secondary galaxies as well as in the primary.
Seyfert nuclei are typical active galactic nuclei (AGNs) in the local universe, which are thought to be powered by gas accretion onto a supermassive black hole (SMBH). The dynamical effect exerted either by non-axisymmetric gravitational potential (such as a stellar bar) or by interaction with other galaxies has been often considered to cause the efficient gas fueling. However, recent systematic studies for large samples of Seyfert nuclei have shown that; 1) Seyfert nuclei do not prefer barred galaxies as their hosts, and 2) only $\simeq$ 10% of Seyfert galaxies have companion galaxies. These …
We have launched a search for large-scale ($\gapprox$1 kpc) minor-axis outflows in edge-on Seyfert galaxies in order to assess their frequency of occurrence and study their properties. Here we present optical continuum and \han2 line images and/or minor-axis long-slit spectra of 22 edge-on Seyfert galaxies. Six of these galaxies show at least one of the following: (i) bi-symmetric H$α$ halos extending along the minor axis, (ii) bright emission-line complexes at distances $\gapprox$4 kpc (in projection) out of the disk, and (iii) double-peaked emission-line profiles from the gas along the minor…
(Abridged) Spiral galaxies often have extended outflows that permeate beyond the region of the disk. Such outflows have been seen both in starburst galaxies, actively star forming galaxies and galaxies with an AGN. In the latter galaxies it is unknown whether the large-scale outflows are driven by star formation activity or purely by the active nucleus. The aim of our investigation is to study the frequency of extended minor-axis outflows in edge-on Seyfert galaxies to investigate the role of the AGN, the circumnuclear environment and star formation activity within the disk regions, and their …
The large scale (~ 100 kpc) environments of Seyfert galaxies are not significantly different from those of non-Seyfert galaxies. In the context of the interaction model of the formation of active galactic nuclei (AGN), it has been proposed that AGN form via "minor mergers" of large disk galaxies with smaller companions. We test this hypothesis by comparing the nuclear spectra of 105 bright nearby galaxies with measurements of their R or r band morphological asymmetries at three successive radii. We find no significant differences in these asymmetries between the 13 Seyfert galaxies in the samp…
We report on a detailed morphological and kinematic study of the isolated non-barred nearby Seyfert 2 galaxy NGC 2110. We combine Integral Field optical spectroscopy, with long-slit and WFPC2 imaging available in the HST archive to investigate the fueling mechanism in this galaxy. Previous work (Wilson & Baldwin 1985) concluded that the kinematic center of the galaxy is displaced \~220 pc from the apparent mass center of the galaxy, and the ionized gas follows a remarkably normal rotation curve. Our analysis based on the stellar kinematics, 2D ionized gas velocity field and dispersion velocity…
We report redshift measurements of 5 X-ray emitting blue stellar objects (BSO's) located less than 12 arc min from the X-ray Seyfert galaxy, NGC 3516. We find these quasars to be distributed along the minor axis of the galaxy and to show a very good correlation between their redshift and their angular distance from NGC 3516. Moreover the redshifts of these 5 quasars are: 0.33, 0.69, 0.93, 1.40 and 2.10 which are very near the peaks of the redshift periodicity distribution (i.e. z=0.3, 0.6, 0.96, 1.41 and 1.96). All these observed properties strikingly confirm, around this single example of a S…
We present a high spatial and spectral resolution 2-D echelle spectrogram of the Narrow-Line Region in the Seyfert 2 galaxy NGC1386. This Seyfert galaxy was observed with CASPEC in the wavelength range 5270-7725 Angstrom which covers the H-alpha and the [N II] lines. With the use of spatially high resolved images taken with the WFPC2 aboard the Hubble Space Telescope we could identify individual components of the Narrow-Line Region in our spectra. A Gaussian decomposition of the spectra revealed 9 distinct emission-line complexes. The brightest component is blue-shifted by -120+-10 km/s with r…
We present deep images of the kpc-scale radio continuum emission in 14 edge-on galaxies (ten Seyfert and four starburst galaxies). Observations were taken with the VLA at 4.9~GHz (6~cm). The Seyfert galaxies were selected from a distance-limited sample of 22 objects (defined in paper~I). The starburst galaxies were selected to be well-matched to the Seyferts in radio power, recessional velocity and inclination angle. All four starburst galaxies have a very bright disk component and one (NGC~3044) has a radio halo that extends several kpc out of the galaxy plane. Six of the ten Seyferts observe…
We describe ISO and BIMA observations of the z=0.04 Seyfert 1 ring galaxy NGC985 which suggest close parallels with some quasar host galaxies. NGC985 contains two closely spaced nuclei embedded in an R$^{1/4}$--law stellar bulge and an outer ring, evidence of an ongoing merger. The system contains \~1.8x10^{10}Msolar of highly disturbed molecular gas which lies in an asymmetric bar-like structure with the peak in observed CO column densities significantly offset from the compact double nucleus. In contrast to this, the ISO observations show strong dust emission centered on the AGN, located in …
We present ROSAT PSPC and HRI images of eight galaxies selected from a distance-limited sample of 22 edge-on Seyfert galaxies. Kiloparsec-scale soft X-ray nebulae extend along the galaxy minor axes in three galaxies (NGC 2992, NGC 4388 and NGC 5506). The extended X-ray emission has 0.2-2.4 keV X-ray luminosities of $0.4-3.5 \times 10^{40} erg s^{-1}$. The X-ray nebulae are roughly co-spatial with the large-scale radio emission, suggesting that both are produced by large-scale galactic outflows. Assuming pressure balance between the radio and X-ray plasmas, the X-ray filling factor is $\gapprox…
We have investigated the dynamics of the merging process in the minor merger hypothesis for active galactic nuclei. We find that for a satellite galaxy to be able to merge directly with the nucleus of the host galaxy (for example, to give rise to the compact dust discs which are seen in early type active galaxies) requires the initial orbit of the satellite to be well aimed. For the case of the host galaxy being a disc galaxy, if the initial orbits of the satellites are randomly oriented with respect to the host galaxy, then the orbits of those which reach the host nuclear regions in a reasona…
The Seyfert 1 nucleus of NGC 4395 is energized by a black hole of 360,000 Solar masses (Peterson et al.), making it one of only two nuclear black holes of intermediate mass, one thousand to one million Solar masses, detected in the radio regime. Building upon UV and X-ray evidence for outflows from this Seyfert nucleus, the VLBI High Sensitivity Array was used at 1.4 GHz to search for extended structure on scales greater than 5 mas (0.1 pc). Elongated emission was discovered, extending over 15 mas (0.3 pc) and suggesting an outflow on sub-parsec scales from this intermediate-mass black hole. T…
Given the existence of the M_BH-sigma relation, models of self-regulated black hole (BH) growth require both a fuel supply and growth of the host bulge to deepen the potential, or else the system will either starve or self-regulate without sustained activity. This suggests that bright quasars must be triggered in major mergers: a large fraction of the galaxy must be converted to new bulge mass in a dynamical time or less. Low-luminosity AGN, in contrast, require little bulge growth and small gas supplies, and could be triggered in more common non-merger events. This predicts a transition to me…
We have collected emission line ([Oiii] 5007 and Halpha+[Nii]) and radio continuum images for a volume limited (cz <= 3600 km/s) sample of southern Seyfert galaxies. The optical data were obtained at ESO using the 2.2 m, NTT and 3.6 m telescopes, and have a typical resolution of 1" and noise level of ~1e-16 ergs cm-2 s-1 arcsec-2. The radio continuum observations were obtained with the VLA (6 cm) and ATCA (3 cm) and have a resolution of ~1" matching that of the optical images. All, but one of the observed sources were detected above the noise limit of ~0.15 mJy. In the radio, 30% of the source…
We present non-adiabatic hydrodynamic simulations of a supersonic light jet propagating into a fully ionized medium of uniform density on a scale representative of the narrow line region (NLR) in Seyfert galaxies with associated radio jets. In this regime the cooling distance of the swept up gas in the bowshock of the jet is of the same order as the transverse extent of the jet bowshock, as opposed to the more extreme regimes found for more powerful adiabatic large scale jets or the slow galactic jets which have been simulated previously. We calculate the emissivity for the H_alpha line and ra…
(Abridged) We present here a long (100ks) XMM-Newton follow-up of the Seyfert 1.8 galaxy ESO113-G010 performed in November 2005, in order to study over a longer time-scale its main X-ray properties. The source was found in a higher/softer time-averaged flux state, and timing analysis of this source reveals strong, rapid variability. The Power Spectral Density (PSD) analysis indicates (at 95% c.l.) a break at 3.7 x 10^-4 Hz. This cut-off frequency is comparable to those measured in some other rapidly-variable Seyferts, such as MCG-6-30-15 and NGC4051. From the mass-luminosity-time-scale, we inf…
Aperture synthesis observations of CO(J=1-0) emission and near-infrared broad-band photometry of the non-barred Seyfert galaxy NGC 5033 (D = 18.7 Mpc) were performed. Our 3".9 x 3".6 resolution CO observations reveal a perturbed distribution and the kinematics of molecular gas in the center of NGC 5033; we find the characteristic gaseous features that are widely observed in barred spiral galaxies, such as two bright CO peaks near the center (separated by ~ 3'' or 270 pc from the nucleus), two offset ridges of CO emission emanating from the CO peaks, and a CO ring (with a radius of ~ 14'' or 1.…
D. Reimers and H.-J. Hagen report in A&A 329, L25 (1998) that a QSO of z = .807 is a "by chance projection" on the center of a galaxy of z = .009. A considerable amount of previously published evidence would lead us to expect an active, low redshift galaxy within about one degree of such a quasar. It is shown here that, in fact, there is a bright Seyfert galaxy of z = .008 only 36.9 arcmin distance. Moreover, it turns out that a total of five quasars, plus the dwarf galaxy, are accurately aligned along the minor axis of this Seyfert with the quasars in descending order of redshift, i.e., z = 2…
We found a very large, 35 kpc, emission-line region around the Seyfert type 2 galaxy NGC 4388, using deep narrow-band imaging with the prime focus camera (Suprime-Cam) of the Subaru telescope. This region consists of many faint gas clouds or filaments, and extends northeastwards from the galaxy. The typical H-alpha luminosity L(H-alpha) of the clouds is 10^37 erg s^-1, and the total L(H-alpha) of the region within 10 kpc from the nucleus is 2 x 10^38 erg s^-1, which corresponds to an ionized gas mass of 10^5 M_solar. The map of the emission-line intensity ratio I([OIII])/I(H-alpha) indicates t…
The velocity dispersion of 7 Seyfert 1 galaxies at z~0.37 is measured using high signal-to-noise Keck spectra. Black hole (BH) mass estimates are obtained via an empirically calibrated photoionization method. We derive the BH mass velocity dispersion relationship at z~0.37. We find an offset with respect to the local relationship, in the sense of somewhat lower velocity dispersion at a fixed BH mass at z~0.37 than today, significant at the 97% level. The offset corresponds to Delta log sigma = -0.16 with rms scatter of 0.13 dex. If confirmed by larger samples and independent checks on systemat…
We report on a detailed kinematic study of the galactic-scale outflow in the Seyfert galaxy NGC 2992. The TAURUS-2 Imaging Fabry-Perot Interferometer was used on the Anglo-Australian 3.9-m telescope to derive the two-dimensional velocity field of the Halpha-emitting gas over the central arcminute of NGC 2992. The complete two-dimensional coverage of the data combined with simple kinematic models of rotating axisymmetric disks allows us to differentiate the outflowing material from the line-emitting material associated with the galactic disk. The kinematics of the disk component out to R = 3.0 …
We present new UV spectra of the nucleus of the Seyfert 1 galaxy NGC 5548, which we obtained with the Space Telescope Imaging Spectrograph at high spectral resolution, in conjunction with simultaneous Chandra X-ray Observatory spectra. Taking advantage of the low UV continuum and broad emission-line fluxes, we have determined that the deepest UV absorption component covers at least a portion of the inner, high-ionization narrow-line region (NLR). We find nonunity covering factors in the cores of several kinematic components, which increase the column density measurements of N V and C IV by fac…
We present a new technique for observationally identifying galaxy mergers spectroscopically rather than through host galaxy imaging. Our technique exploits the dynamics of supermassive black holes (SMBHs) powering active galactic nuclei (AGNs) in merger-remnant galaxies. Because structure in the universe is built up through galaxy mergers and nearly all galaxies host a central SMBH, some galaxies should possess two SMBHs near their centers as the result of a recent merger. These SMBHs spiral to the center of the resultant merger-remnant galaxy, and one or both of the SMBHs may power AGNs. Usin…
Optical spectropolarimetry of the nucleus of the LINER NGC 1052, obtained at the Keck Observatory, reveals a rise in polarization in the wings of the H-alpha line profile. The polarization vector of H-alpha is offset by 67 degrees from the parsec-scale radio axis and by 83 degrees from the kiloparsec-scale radio axis, roughly in accord with expectations for scattering within the opening cone of an obscuring torus. The broad component of H-alpha has FWHM ~ 2100 km/s in total flux and FWHM ~ 5000 km/s in polarized light. Scattering by electrons is the mechanism most likely responsible for this b…
We present optical and near-IR spectroscopy of a z=2.38 hyperluminous IR galaxy, covering the restframe wavelength range from 1000-5000A. It appears to comprise two components separated by less than 1" on the sky (<8kpc); one component (B) is blue, the other (P) is red in restframe UV-optical colours. The combined system has an optical luminosity of ~8L* and its restframe optical spectrum is characteristic of a Seyfert AGN. However, its restframe UV spectrum exhibits striking features associated with young stars, including P-Cygni lines from stellar winds and blue-shifted interstellar absorpti…
We present optical images of the nucleus of the nearby radio galaxy M84 (NGC 4374 = 3C272.1) obtained with the Wide Field/Planetary Camera 2 (WFPC2) aboard the Hubble Space Telescope (HST). Our three images cover the H$α$ + [N II] emission lines as well as the V and I continuum bands. Analysis of these images confirms that the H$α$ + [N II] emission in the central 5'' (410 pc) is elongated along position angle (P.A.) $\approx 72\arcdeg$, which is roughly parallel to two nuclear dust lanes.Our high-resolution images reveal that the H$α$ + [N II] emission has three components, namely a nuclear g…
We present ISO-SWS and ISOPHOT-S spectroscopy of the Seyfert galaxy NGC 4151. We detect a total of 17 fine structure emission lines emitted by a wide range of low- and high-excitation ions, two rotational lines of molecular hydrogen, and the Br beta HI line. We find that the mid-IR fine structure line profiles display blue asymmetries which are very similar to those observed in the optical lines produced in the narrow line region. Because the mid-infrared lines are much less sensitive to extinction than are the optical lines this similarity places strong constraints on scenarios which have bee…
