scholarly journals Correlations between Environmental Parameters and Nuclear Activity

1990 ◽  
Vol 124 ◽  
pp. 437-440
Author(s):  
W. Kollatschny ◽  
K.J. Fricke
Keyword(s):  
Sample Size ◽  
Seyfert Galaxy ◽  
Environmental Parameters ◽  
Seyfert Galaxies ◽  
Nuclear Activity ◽  
The Galaxy ◽  
Quantitative Properties ◽  
Galaxy Environment ◽  
Companion Galaxy

The occurrence and quantitative properties of Seyfert 1 and Seyfert 2 galaxies as a function of the galaxy environment have been studied in a systematic way. For this investigation we have selected from the Catalogue of Quasars and Active Nuclei (Veron & Veron, 1989) all Seyfert galaxies with the following properties:(i) mV ≤ 15,(ii) listed classification as Sey 1, Sey 2, or Sey 3,(iii) vrad ≤ 20000 km s-1.This results in a sample size of 242 Seyfert galaxies. For all these objects their galaxy environment has been inspected on POSS and ESO/SRC plates.The vicinity of each sample Seyfert galaxy was searched for companion galaxies out to at least 0.5 Mpc. Lacking redshift information we adopted as a companion galaxy any galaxy in this area having a size between 20 and 200 percent of the Seyfert galaxy size.

scholarly journals Nuclear Activity in the Seyfert Galaxy NGC 1365

1994 ◽  
Vol 159 ◽  
pp. 448-448
Author(s):  
M. Hjelm ◽  
P.O. Lindblad ◽  
S. Jörsäter
Keyword(s):  
Velocity Gradient ◽  
Seyfert Galaxy ◽  
Minor Axis ◽  
Contour Plot ◽  
Nuclear Activity ◽  
The Galaxy ◽  
Ngc 1365

NGC 1365 is a barred Seyfert 1.5 galaxy. Fig 1a is a contour plot of an [OIII]λ5007 image (Jörsäter & Lindblad 1989), showing a plume-like structure pointing towards SE in the direction of the minor axis of the galaxy, which also is the direction of the steepest velocity gradient in [OIII]λ5007. The plume is roughly aligned with a radio feature in the 6 and 20 cm continuum (see Sandqvist et al., this volume). The [OIII]-emission on the NW side is weaker. This plume-like structure is not seen in Hα.

scholarly journals Secular evolution and pseudo-bulges

2019 ◽  
Vol 14 (S353) ◽  
pp. 155-161
Author(s):  
Francoise Combes
Keyword(s):  
Black Hole ◽  
Angular Resolution ◽  
Seyfert Galaxies ◽  
Central Star ◽  
Gravity Models ◽  
Nuclear Activity ◽  
Secular Evolution ◽  
The Galaxy ◽  
Galaxy Disk ◽  
Zone Of Influence

AbstractThrough vertical resonances, bars can produce pseudo-bulges, within secular evolution. Bulges and pseudo-bulges have doubled their mass since z=1. The frequency of bulge-less galaxies at z=0 is difficult to explain, especially since clumpy galaxies at high z should create classical bulges in all galaxies. This issue is solved in modified gravity models. Bars and spirals in a galaxy disk, produce gravity torques that drive the gas to the center and fuel central star formation and nuclear activity. At 0.1-1kpc scale, observations of gravity torques show that only about one third of Seyfert galaxies experience molecular inflow and central fueling, while in most cases the gas is stalled in resonant rings. At 10-20pc scale, some galaxies have clearly revealed AGN fueling due to nuclear trailing spirals, influenced by the black hole potential. Thanks to ALMA, and angular resolution of up to 80mas, it is possible to reach the central black hole (BH) zone of influence, discover molecular tori, circum-nuclear disks misaligned with the galaxy, and the BH mass can be derived more directly from the kinematics.

Seyfert Galaxies and Their Environment

1999 ◽  
Vol 186 ◽  
pp. 355-355
Author(s):  
P. Focardi ◽  
B. Kelm ◽  
G.G.C. Palumbo
Keyword(s):  
Seyfert Galaxies ◽  
Nuclear Activity ◽  
Normal Galaxies ◽  
Normal Galaxy ◽  
Large Samples ◽  
The Galaxy ◽  
Pair Separation ◽  
Galaxy Sample

The role played by environment on nuclear activity in galaxies is not clear and largely debated (see e.g. Barnes & Hernquist 1992, Kelm 1996). To overcome statistical uncertainties, environment properties of two large samples of Seyfert galaxies (Sy 1 and Sy 2 have been kept separated) have been computed and compared with equivalent size “normal galaxy” sample ones. Seyfert samples have been extracted from the Veron & Veron catalogue (Veron & Veron 1996), whilst “normal galaxies” have been randomly extracted from ZCAT (Huchra 1993). The samples are limited in cz ([1500–9500] km/sec) and contain 149 Sy 1, 173 Sy 2 and 160 “normal galaxies” (hundreds of random extractions from ZCAT). For each galaxy neighbors have been computed (from ZCAT) within two variables radii, R (isolation radius) and r (pair separation), which span [0.2 - 2] h100 Mpc. and [20–90]h100 kpc. respectively. Neighbors must lie also within 700 km/sec from the galaxy. In this way, for each value of R and r, environment of each galaxy has been “quantified”.

scholarly journals Galaxy Interactions and Strength of Nuclear Activity

1990 ◽  
Vol 124 ◽  
pp. 399-402
Author(s):  
S. M. Simkin
Keyword(s):  
Theoretical Calculations ◽  
Seyfert Galaxies ◽  
Tidal Effects ◽  
Galaxy Interactions ◽  
Nuclear Activity ◽  
Feeding Mechanism ◽  
Companion Galaxy

Almost a decade ago, the morphological similarities between patterns seen in Seyfert galaxies and those produced by gravitational forcing led to the suggestion that Seyfert activity might be fueled by material inflow induced by either a central bar or a perturbing companion (Simkin, Su, and Schwarz, 1980). More recent theoretical calculations suggest that such a feeding mechanism may involve a central bar-like, structure even if initially induced by the tidal effects of a companion galaxy (Noguchi, 1988a,b).

scholarly journals Nuclear Activity of Galaxies within Groups

1987 ◽  
Vol 121 ◽  
pp. 371-376
Author(s):  
K.J. Fricke ◽  
W. Kollatschny
Keyword(s):  
Critical Radius ◽  
Control Sample ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
Activity Class ◽  
Nuclear Activity ◽  
Group Member

Results from a spectroscopic survey of groups around Seyfert galaxies and of an appropriate control sample are reported. The groups are ≲1 Mpc across. A nuclear spectroscopic “activity class” is assigned to each group member. The active types show a peaked distribution around the Seyfert galaxy and are confined to a critical radius ~300 kpc while the nonactive members are uniformly distributed over the whole extent of the groups. These results are briefly discussed.

scholarly journals Understanding the origin of radio outflows in Seyfert galaxies using radio polarimetry

2019 ◽  
Vol 15 (S356) ◽  
pp. 247-251
Author(s):  
Biny Sebastian ◽  
Preeti Kharb ◽  
Christopher P. O’ Dea ◽  
Jack F. Gallimore ◽  
Stefi A. Baum ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Radio Emission ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
Starburst Galaxies ◽  
Galactic Magnetic Fields ◽  
5 Ghz

AbstractThe role of starburst winds versus active galactic nuclei (AGN) jets/winds in the formation of the kiloparsec scale radio emission seen in Seyferts is not yet well understood. In order to be able to disentangle the role of various components, we have observed a sample of Seyfert galaxies exhibiting kpc-scale radio emission suggesting outflows, along with a comparison sample of starburst galaxies, with the EVLA B-array in polarimetric mode at 1.4 GHz and 5 GHz. The Seyfert galaxy NGC 2639, shows highly polarized secondary radio lobes, not observed before, which are aligned perpendicular to the known pair of radio lobes. The additional pair of lobes represent an older epoch of emission. A multi-epoch multi-frequency study of the starburst-Seyfert composite galaxy NGC 3079, reveals that the jet together with the starburst superwind and the galactic magnetic fields might be responsible for the well-known 8-shaped radio lobes observed in this galaxy. We find that many of the Seyfert galaxies in our sample show bubble-shaped lobes, which are absent in the starburst galaxies that do not host an AGN.

scholarly journals Hidden molecular outflow in the LIRG Zw 049.057

2018 ◽  
Vol 609 ◽  
pp. A75 ◽  
Author(s):  
N. Falstad ◽  
S. Aalto ◽  
J. G. Mangum ◽  
F. Costagliola ◽  
J. S. Gallagher ◽  
...  
Keyword(s):  
Far Infrared ◽  
Minor Axis ◽  
Spectral Lines ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Nuclear Activity ◽  
Molecular Outflow ◽  
The Galaxy ◽  
Excitation Conditions

Context. Feedback in the form of mass outflows driven by star formation or active galactic nuclei is a key component of galaxy evolution. The luminous infrared galaxy Zw 049.057 harbours a compact obscured nucleus with a possible far-infrared signature of outflowing molecular gas. Due to the high optical depths at far-infrared wavelengths, however, the interpretation of the outflow signature is uncertain. At millimeter and radio wavelengths, the radiation is better able to penetrate the large columns of gas and dust responsible for the obscuration. Aims. We aim to investigate the molecular gas distribution and kinematics in the nucleus of Zw 049.057 in order to confirm and locate the molecular outflow, with the ultimate goal to understand how the nuclear activity affects the host galaxy. Methods. We used high angular resolution observations from the Submillimeter Array (SMA), the Atacama Large Millimeter/submillimeter Array (ALMA), and the Karl G. Jansky Very Large Array (VLA) to image the CO J = 2–1 and J = 6–5 emission, the 690 GHz continuum, the radio centimeter continuum, and absorptions by rotationally excited OH. Results. The CO line profiles exhibit wings extending ~ 300 km s-1 beyond the systemic velocity. At centimeter wavelengths, we find a compact (~ 40 pc) continuum component in the nucleus, with weaker emission extending several 100 pc approximately along the major and minor axes of the galaxy. In the OH absorption lines toward the compact continuum, wings extending to a similar velocity as for the CO are only seen on the blue side of the profile. The weak centimeter continuum emission along the minor axis is aligned with a highly collimated, jet-like dust feature previously seen in near-infrared images of the galaxy. Comparison of the apparent optical depths in the OH lines indicate that the excitation conditions in Zw 049.057 differ from those within other OH megamaser galaxies. Conclusions. We interpret the wings in the spectral lines as signatures of a nuclear molecular outflow. A relation between this outflow and the minor axis radio feature is possible, although further studies are required to investigate this possible association and understand the connection between the outflow and the nuclear activity. Finally, we suggest that the differing OH excitation conditions are further evidence that Zw 049.057 is in a transition phase between megamaser and kilomaser activity.

scholarly journals The impact of bars and interactions on optically selected AGNs in spiral galaxies

2018 ◽  
Vol 618 ◽  
pp. A149 ◽  
Author(s):  
Sol Alonso ◽  
Georgina Coldwell ◽  
Fernanda Duplancic ◽  
Valeria Mesa ◽  
Diego G. Lambas
Keyword(s):  
Spiral Galaxies ◽  
Control Sample ◽  
Sloan Digital Sky Survey ◽  
Blue Color ◽  
Nuclear Activity ◽  
Internal Process ◽  
Two Samples ◽  
Accretion Rates ◽  
The Galaxy ◽  
The Impact

Aims. With the aim of performing a suitable comparison of the internal process of galactic bars with respect to the external effect of interactions on driving gas toward the inner most region of the galaxies, we explored and compared the efficiency of both mechanisms on central nuclear activity in optically selected active galactic nuclei (AGNs) in spiral galaxies. Methods. We selected homogeneous samples of barred AGNs and active objects residing in pair systems, derived from the Sloan Digital Sky Survey (SDSS). In order to carry out a reliable comparison of both samples (AGNs in barred hosts in isolation and in galaxy pairs), we selected spiral AGN galaxies with similar distributions of redshift, magnitude, stellar mass, color and stellar age population from both catalogs. With the goal of providing an appropriate quantification of the influence of strong bars and interactions on nuclear activity, we also constructed a suitable control sample of unbarred spiral AGNs without a companion and with similar host properties to the other two samples. Results. We found that barred optically selected AGNs show an excess of nuclear activity (as derived from the Lum[OIII]) and accretion rate onto a central black hole (ℛ) with respect to AGNs in pairs. In addition, both samples show an excess of high values of Lum[OIII] and ℛ with respect to unbarred AGNs in the control sample. We also found that the fractions of AGNs with powerful nuclear activity and high accretion rates increase toward more massive hosts with bluer colors and younger stellar populations. Moreover, AGNs with bars exhibit a higher fraction of galaxies with powerful Lum[OIII] and efficient ℛ with respect to AGN galaxies inhabiting pair systems, in bins of different galaxy properties. Regarding AGNs belonging to pair systems, we found that the central nuclear activity is remarkably dependent on the galaxy pair companion features. The Lum[OIII] for AGNs in pairs is clearly enhanced when the galaxy companion exhibits a bright and more massive host with high metallicity, blue color, efficient star formation activity and young stellar population. The results of this work reveal an important capacity of both mechanisms, bars and interactions, to transport material towards the galaxy central regions. In this context, it should also be noted that the internal process of the bar is more efficient at improving the central nuclear activity in AGN objects than that corresponding to the external mechanism of the galaxy–galaxy interactions.

scholarly journals Radio and X-ray Observations of the Restarted Radio Galaxy in the Galaxy Cluster CL 0838+1948

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 108
Author(s):  
Simona Giacintucci ◽  
Tracy Clarke ◽  
Namir E. Kassim ◽  
Wendy Peters ◽  
Emil Polisensky
Keyword(s):  
Radio Source ◽  
Survey Data ◽  
Radio Galaxy ◽  
Galaxy Cluster ◽  
Gas Emission ◽  
Low Frequencies ◽  
Nuclear Activity ◽  
X Ray ◽  
Hot Gas ◽  
The Galaxy

We present VLA Low-band Ionosphere and Transient Experiment (VLITE) 338 MHz observations of the galaxy cluster CL 0838+1948. We combine the VLITE data with Giant Metrewave Radio Telescope 610 MHz observations and survey data. The central galaxy hosts a 250 kpc source whose emission is dominated by two large lobes at low frequencies. At higher frequencies, a pair of smaller lobes (∼30 kpc) is detected within the galaxy optical envelope. The observed morphology is consistent with a restarted radio galaxy. The outer lobes have a spectral index αout=1.6, indicating that they are old, whereas the inner lobes have αinn=0.6, typical for an active source. Spectral modeling confirms that the outer emission is a dying source whose nuclear activity switched off not more than 110 Myr ago. Using archival Chandra X-ray data, we compare the radio and hot gas emission. We find that the active radio source is contained within the innermost and X-ray brightest region, possibly a galactic corona. Alternatively, it could be the remnant of a larger cool core whose outer layers have been heated by the former epoch of activity that has generated the outer lobes.

scholarly journals The Galaxy Environment of Quasars in the z ⋍ 1.3 Clowes-Campusano Large Quasar Group

2005 ◽  
Vol 201 ◽  
pp. 465-466
Author(s):  
C. P. Haines ◽  
R. G. Clowes ◽  
L. E. Campusano
Keyword(s):  
Star Formation ◽  
The Galaxy ◽  
Galaxy Environment ◽  
Red Sequence

We report significant associated clustering in the field of a z = 1.226 quasar from the Clowes-Campusano LQG in the form of both a factor ˜ 11 overdensity of I - K > 3.75 galaxies, and red sequences of 15-18 galaxies at I - K ⋍ 4.3, V - K ⋍ 6.9 indicative of a population of massive ellipticals at the quasar redshift. The quasar is located between two groups of these galaxies, with further clustering extending over 2-3 Mpc. A band of V - I < 1 galaxies bisects the two groups of red sequence galaxies, and we suggest that the merging of these two groups has triggered both this band of star-formation and the quasar.

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