A. A. Smirnova

HST IMAGING OF FADING AGN CANDIDATES. I. HOST-GALAXY PROPERTIES AND ORIGIN OF THE EXTENDED GAS*

We present narrow- and medium-band HST imaging, with additional supporting ground-based data, for 8 galaxies identified as hosting fading AGN. These have AGN-ionized gas projected >10 kpc from the nucleus, and significant shortfall of ionizing radiation between the distant gas and the AGN, indicating fading AGN on ~50,000-year timescales. Every system shows evidence of ongoing or past interactions; a similar sample of obscured AGN with extended ionized clouds shares this incidence of disturbances. Several systems show multiple dust lanes in different orientations, broadly fit by differentially precessing disks of accreted material ~1.5 Gyr after initial arrival. The gas has lower metallicity than the nuclei; three systems have abundances uniformly well below solar, consistent with an origin in tidally disrupted low-luminosity galaxies, while some systems have more nearly solar abundances (accompanied by such signatures as multiple Doppler components), which may suggest redistribution of gas by outflows within the host galaxies themselves. These aspects are consistent with a tidal origin for the extended gas in most systems, although the ionized gas and stellar tidal features do not always match closely. In contrast to clouds near radio-loud AGN, these are dominated by rotation, in some cases in warped disks. Outflows are important only in localized regions near some of the AGN. In UGC 7342 and UGC 11185, luminous star clusters are seen within projected ionization cones, potentially triggered by outflows. As in the discovery example Hannys Voorwerp/IC 2497, some clouds lack a strong correlation between H-alpha surface brightness and ionization parameter, indicating unresolved fine structure. Together with thin coherent filaments spanning several kpc, persistence of these structures over their orbital lifetimes may require a role for magnetic confinement. (Abridged)

Seyfert galaxies that are undergoing merging but appear non-interacting

We present new broad-band optical images of some merging Seyfert galaxies that were earlier considered to be non-interacting objects. In our deep images obtained at the Russian 6-m telescope we have detected elongated tidal envelopes belonging to satellites debris with a surface R-band brightness about 25-26.5 mag arcsec ―2 . These structures are invisible in Sloan Digital Sky Survey (SDSS) pictures because of their photometric limit. We found that 35 per cent of the sample of isolated galaxies has undergone merging during the last 0.5-1 Gyr. Our results suggest that statistical studies based on popular imaging surveys (SDSS or Second Palomar Observatory Sky Survey (POSS-II)) can lead to underestimation of the fraction of minor mergers among galaxies with active nuclei (AGN). This fact impacts on statistics and must be taken into consideration when finding a connection between minor/major merging or interactions and nucleus activity.

Fading AGN Candidates: AGN Histories and Outflow Signatures

We consider the energy budgets and radiative history of eight fading AGN, identified from an energy shortfall between the requirements to ionize very extended (radius > 10 kpc) ionized clouds and the luminosity of the nucleus as we view it directly. All show evidence of significant fading on ≈ 50, 000-year timescales. We explore the use of minimum ionizing luminosity Qion derived from photoionization balance in the brightest pixels in Hα at each projected radius. Tests using presumably constant Palomar-Green (PG) QSOs, and one of our targets with detailed photoionization modeling, suggest that we can derive useful histories of individual AGN, with the caveat that the minimum ionizing luminosity is always an underestimate and subject to uncertainties about fine structure in the ionized material. These consistency tests suggest that the degree of underestimation from the upper envelope of reconstructed Qion values is roughly constant for a given object and therefore does not prevent such derivation. The AGN in our sample show a range of behaviors, with rapid drops and standstills; the common feature is a rapid drop in the last ≈ 2 × 10 years before the direct view of the nucleus. The e-folding timescales for ionizing luminosity are mostly in the thousands of years, with a few episodes as short as 400 years. In the limit of largely obscured AGN, we find additional evidence for fading from the shortfall between even the lower limits from recombination balance and the maximum luminosities derived from from infrared fluxes. We compare these long-term light curves, and the occurrence of these fading objects among all optically identified AGN, to simulations of AGN accretion; the strongest variations on these timespans are seen in models with strong and local (parsec-scale) feedback. We present Gemini integral-field optical spectroscopy, which shows a very limited role for outflows in these ionized structures. While rings and loops of emission, morphologically suggestive of outflow, are common, their kinematic structure shows some to be in regular rotation. UGC 7342 exhibits local signatures of outflows < 300 km s−1, largely associated with very diffuse emission, and possibly entraining gas in one of the clouds seen in HST images. Only in the Teacup AGN do we see outflow signatures of order 1000 km s−1. In contrast to the extended emission regions around many radio-loud AGN, the clouds around these fading AGN consist largely of tidal debris being externally illuminated but not displaced by AGN outflows. Subject headings: galaxies: active — galaxies: individual (NGC 5792, NGC 5252, UGC 7342, UGC 11185, Mkn 1498) — galaxies: Seyfert — galaxies: interacting 1Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487 2wkeel@ua.edu, Twitter: @NGC3314 3Astrophysics, Oxford University; and Adler Planetarium, 1300 S. Lakeshore Drive, Chicago, IL 60605 4Current address: Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 5Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407 6Department of Astronomy, New Mexico State University, P. O. Box 30001, MSC 4500, Las Cruces, New Mexico 1 ar X iv :1 61 2. 06 00 6v 1 [ as tr oph .G A ] 1 8 D ec 2 01 6

3D Spectroscopic Study of the Line Emitting Regions of Mrk 493

We report the results of three-dimensional spectroscopic observations of Mrk 493 (narrow-line Seyfert 1 galaxy) with the integral-field spectrograph MultiPupil Fiber Spectrograph of the Special Astrophysical Observatory of the Russian Academy of Sciences 6 m telescope. The difference in the slope of the optical continuum emission intensity across the nucleus part and an extensive continuum emission region is detected. The emission in lines (Hα, Hβ, [O III], etc.) coincides with a composite nuclear region: an active galactic nucleus plus a circumnuclear star-forming ring observed in the Hubble Space Telescope UV/optical images. The [S II] emission region tends to be up to 1 kpc around the center. The Hα and Hβ could be decomposed into three components (broad ~2000 km s–1, intermediate ~700 km s–1, and narrow ~250 km s–1). We found that the width (~750 km s–1) of the Fe II lines corresponds to the intermediate component that may indicate a non-broad-line region (non-BLR) origin of the Fe II lines, or that a large fraction of the Fe II emission arises in the outer parts of the BLR. The weak broad component detected in the Hα, Hβ, and Heλ4686 may come from the unresolved central BLR, but also could be partly produced by violent starburst in the circumnuclear ring. Moreover, diagnostic diagrams clearly show the presence of the H II regions (not an Sy 1 nucleus) in the narrow-line region of Mrk 493.

The origin of gas in extended narrow-line regions of nearby Seyfert galaxies – I. NGC 7212

The extended narrow-line region (ENLR) of an active galactic nucleus (AGN) is a region of highly ionized gas with a size of a few up to 15–20 kpc. When it shows a conical or biconical shape with the apexes pointing towards the active nucleus, this region is also called an ionization cone. Ionization cones are evidence of the unified model, which predicts an anisotropic escape of ionizing photons from a nucleus confined to a cone by a dusty torus. Many details about the complex structure of the ENLR still remain to be unveiled, such as for example the origin of the ionized gas. Here we present new results of a study of the physical and kinematic properties of the circumnuclear gas in the nearby Seyfert 2 galaxy NGC 7212. Medium- and high-resolution integral-field spectra and broad-band photometric data were collected and analysed in the frame of an observational campaign of nearby Seyfert galaxies, with the aim of handling the complicated issue of the origin of gas in the ENLR. This work is based on (i) the analysis of gas physical properties (density, temperature and metallicity), (ii) the analysis of emission-line ratios and (iii) the study of kinematics of gas and stars. By reconstructing the [O III]/Hβ ionization map, we point out for the first time the presence of an ionization cone extended up to about 6 kpc, made of a large amount of low-metallicity gas, kinematically disturbed and decoupled from stars, a highly ionized component of which shows radial motions at multiple velocities, as proved by the complex profiles of the spectral lines. Since NGC 7212 is a strongly interacting triple galaxy system, gravitational effects are likely to be at the origin of the ENLR in this Seyfert galaxy.

Observational evidence for AGN fueling. I. the case of NGC 6104-merging with a companion

We investigate in detail the kinematics and morphology of the Seyfert galaxy NGC 6104 in order to identify the mechanism of gas transportation to the active galactic nucleus (AGN). Our observational data were obtained at the 6-m Special Astrophysical Observatory telescope with the MPFS integral-field spectrograph and the SCORPIO universal device in three modes: direct imaging, a scanning Fabry—Perot interferometer, and long-slit spectroscopy. Images from the HST archive were invoked to study the structure of the circumnuclear region. An analysis of deep images has shown for the first time that NGC 6104 is in the phase of active merging with a companion galaxy. We have been able to study the detailed picture of ionized gas motions up to galactocentric distances of 14 kpc and to construct the stellar velocity field for the inner region. The radial gas motions toward the AGN along the central bar play a significant role at galactocentric distances of 1–5 kpc. In addition, we have detected an outflow of ionized gas from the nucleus that presumably resulted from the intrusion of a radio jet into the ambient interstellar medium. Using diagnostic diagrams, we estimate the contributions from the AGN and star formation to the galactic gas ionization. We estimate the bar pattern speed by the Tremaine-Weinberg method and show that the inner ring observed in the galaxy’s images has a resonant nature. Two possible ring formation scenarios, before and during the interaction with a companion, are discussed.

New photometric and spectroscopic observations of the Seyfert galaxy Mrk 315

We present new important results about the intermediate-type Seyfert galaxy Mrk 315, recently observed through optical imaging and integral-field spectroscopy. Broad-band images were used to study the morphology of the host galaxy, narrow-band Hα images to trace the star-forming regions, and middle-band [O III] images to evidence the distribution of the highly ionized gas. Some extended emission regions were isolated and their physical properties studied by means of flux-calibrated spectra. High-resolution spectroscopy was used to separate different kinematic components in the velocity fields of gas and stars. Some peculiar features characterize this apparently undisturbed and moderately isolated active galaxy. Such features, already investigated by other authors, are re-analysed and discussed in the light of these new observations. The most relevant results we obtained are: the multitiers structure of the disc; the presence of a quasi-ring of regions with star formation much higher than previous claims; a secondary nucleus confirmed by a stellar component kinematically decoupled by the main galaxy; a new hypothesis about the controversial nature of the long filament, initially described as hook shaped, and more likely made of two independent filaments caused by interaction events between the main galaxy and two dwarf companions. Ke yw ords: galaxies: individual: Mrk 315 ‐ galaxies: interactions ‐ galaxies: Seyfert.

3D spectroscopy of merger Seyfert galaxy Mrk 334: nuclear starburst, superwind and the circumnuclear cavern

We are presenting new results on kinematics and structure of the Mrk 334 Seyfert galaxy. Panoramic (3D) spectroscopy is performed at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences using the integral-field Multi-Pupil Fiber Spectrograph (MPFS) and scanning Fabry―Perot interferometer. The deep images have revealed that Mrk 334 is observed during the final stage of its merging with a massive companion. A possible mass ratio ranges from 1/5 to 1/3. The merger has triggered mass redistribution in the disc resulting in an intensification of nuclear activity and in a burst of star formation in the inner region of the galaxy. The circumnuclear starburst is so intense that its contribution to the gas ionization exceeds that contribution of the active galactic nuclei (AGN). We interpret the nuclear gas outflow with velocities of ∼200 km s ―1 as a galactic superwind that accompanies the violent star formation. This suggestion is consistent with the asymmetric X-ray brightness distribution in Mrk 334. The trajectory of the fragments of the disrupted satellite in the vicinity of the main galaxy nucleus can be traced. In the galaxy disc, a cavern is found that is filled with a low-density ionized gas. We consider this region to be the place where the remnants of the companion have recently penetrated through the gaseous disc of the main galaxy.

The Gas Content in Galactic Disks: Correlation with Kinematics

We consider the relationship between the total HI mass in late-type galaxies and the kinematic properties of their disks. The mass MHI for galaxies with a wide variety of properties, from dwarf dIrr galaxies with active star formation to giant low-brightness galaxies, is shown to correlate with the product VcR0 (Vc is the rotational velocity, and R0 is the radial photometric disks cale length), which characterizes the specific angular momentum of the disk. This correlation, along with the decrease in the relative mass of the gas in a galaxy with increasing Vc, can be explained in terms of the previous assumption that the gas density in the disks of most galaxies is maintained at a level close to the threshold (marginal) stability of a gaseous layer to local gravitational perturbations. In this case, the regulation mechanism of the star formation rate associated with the growth of local gravitational instability in the gaseous layer must play a crucial role in the evolution of the gas content in the galactic disk.

The gas kinematics in the Mrk 533 nucleus and circumnuclear region: a gaseous outflow

We present an analysis of 3D spectra of Mrk 533, observed with the integral-field spectrograph MultiPupil Fiber Spectrograph (MPFS) and using the Fabry-Perot Interferometer (FPI) of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) 6-m telescope. We found emissions of gas from the active type 2 Seyfert nucleus in the centre and also from the H II regions in a spiral structure and a circumnuclear region. The gas kinematics shows regular non-circular motions in the wide range of galactocentric distances from 500 pc up to 15 kpc. The maps of inward and outward radial motions of the ionized gas were constructed. We found that the narrow-line region (NLR) is composed of at least two (probably three) kinematically separated regions. We detect a stratification in the NLR of Mrk 533 with the outflow velocity ranging from 20-50 kms -1 to 600-700 kms -1 , respectively, on the radial distances of ∼2.5 and ∼1.5 kpc. The maximal outflow velocity comes from the nucleus and corresponds to the position of the observed radio structure, which is assumed to be created in an approaching jet. We suggest that these ionized gas outflows are triggered by the radio jet intrusion in an ambient medium.