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 Collimated Bipolar Outflow and the Formation of Nuclear Spirals; Possible Role of Magnetic Fields

1990 ◽  
Vol 140 ◽  
pp. 447-448
Author(s):  
P. Pismis ◽  
E. Moreno ◽  
A. Garcia-Barreto
Keyword(s):  
Magnetic Fields ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
The Past ◽  
Bipolar Outflow ◽  
The Difference ◽  
Observational Techniques ◽  
Quasars And Radio Galaxies

The existence of non–steady phenomena, namely activity in the form of radial motions (outflow) of matter from the nuclei of galaxies is well established at present. Active Galactic Nuclei (AGN) constitute a topic of great interest and are intensively studied by all existing observational techniques. Conventionally objects classified as AGN span a range from quasars, radio galaxies to Seyferts 1 and 2. It appears, however, that there exist galaxies which exhibit somewhat milder activity which does not qualify their inclusion in the AGN group. The designation of MAGN (M for mildly) was suggested in the past (Pismis, 1986) to cover the less energetic nuclei. It may be reasonable to consider that active nuclei form a sequence, the difference along it being due to the energetics of the nuclei, from the most active quasars and radio galaxies down to the mildest ones like M31 or our Galaxy. The phenomenon underlying the activity may thus be universal, subject to the intrinsic energetics of the nuclei (Pismis, 1987).

scholarly journals Radio Nuclei in Nearby Galaxies

1984 ◽  
Vol 110 ◽  
pp. 251-256
Author(s):  
E. Preuss
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Instrumental Performance ◽  
Nuclear Activity ◽  
Normal Galaxies ◽  
Nearby Galaxies ◽  
The Subject ◽  
5 Ghz ◽  
Work Done

This review is an attempt to summarize VLBI continuum observations at cm- and dm-wavelengths of active galactic nuclei at distances ≲ 100 Mpc (Ho = 50 km s−1 Mpc−1). ‘Nearby galaxies’, thus defined, are close enough for achieving the highest possible spatial resolution. Galaxies at these distances, however, typically do not show extreme and rare forms of nuclear activity such as powerful radio sources, the cores of which are relatively easy to map with VLBI, and which are therefore the subject of most of the VLBI work done so far (see e.g. Preuss, 1983). Nearby active galaxies show rather more ‘ordinary’ forms of nuclear activity; they include a few of the weaker classical ‘radio galaxies’, but most of them are Seyfert galaxies and mildly active ‘normal galaxies’. Their total radio emission is typically weak (P(5 GHz) ≲ 1031 erg s−1 Hz−1) and so are their compact radio nuclei (if any). The highest available sensitivity is therefore required for their study and the current instrumental performance is just becoming sufficient to tackle the strongest of them in the hope of obtaining maps.

scholarly journals Planetary Nebulae and Seyfert Galaxies - Similarities and Differences

1983 ◽  
Vol 103 ◽  
pp. 473-486 ◽  
Author(s):  
Donald E. Osterbrock
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Planetary Nebulae ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
Broad Line ◽  
Tentative Model ◽  
Input Spectrum ◽  
Similarities And Differences ◽  
Galaxy Nucleus

Knowledge gained in the study of planetary nebulae has been, and can be further, transferred to understanding active galactic nuclei. Photoionization is the main energy-input mechanism in the narrow-line regions, and probably although by no means certainly in the broad-line regions as well. There are many detailed differences because of the much “harder” input spectrum in active galactic nuclei, compared with planetary nebulae. A tentative model of the structure of the gas distribution in a Seyfert-galaxy nucleus is presented.

scholarly journals X-Ray Properties of Galactic Nuclei

1980 ◽  
Vol 5 ◽  
pp. 623-630
Author(s):  
Daniel W. Weedman
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
Strong Emission ◽  
X Ray ◽  
Ngc 4151 ◽  
Survey Results ◽  
Emission Line Galaxies

Preparing this review was my just punishment for stating only two years ago - in another review (Weedman 1977) - that Seyfert galaxies are not strong X-ray sources. I said that because, as recently as three years ago, NGC 4151 was the only Seyfert galaxy known as an X-ray source. Now we have 36 Seyfert 1 galaxies, along with 12 other galaxies with strong emission-line nuclei, that are X-ray sources. And this is all without even having HEAO-2 data at our disposal yet. The study of active galactic nuclei with X-ray astronomy is progressing so rapidly that a reviewer feels almost hopeless. The best I can do is summarize what is known as of the summer of 1979 and give a simple overview of how X-ray and other properties relate.Some excellent reviews of the X-ray properties of Seyfert and other emission-line galaxies already exist. I especially recommend that by Andrew Wilson (1979). He provides very complete references as of a year ago, but X-ray astronomy is progressing so rapidly that he then had only somewhat more than half the active nuclei now in Tables 1 and 2. It was the group working with the Ariel V SSI that made the initial comprehensive X-ray studies of Seyfert galaxies (Ward et al. 1977, Elvis et al. 1978). The UHURU results for Seyfert galaxies followed soon after and are summarized by Tananbaum et al. (1978); the HEAO-A-2 survey results are now in press (Marshall et al. 1979) I have tried to incorporate these and other recent results in Tables 1 and 2.

scholarly journals Radio Emission from Low-Luminosity Active Galactic Nuclei

1998 ◽  
Vol 164 ◽  
pp. 205-206
Author(s):  
Schuyler D. Van Dyk ◽  
Luis C. Ho
Keyword(s):  
High Resolution ◽  
Radio Emission ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Physical Origin ◽  
Common Variety ◽  
Nearby Galaxies ◽  
Optical Evidence ◽  
Shed Light

AbstractMany nearby galaxies show optical evidence for low-luminosity AGNs that are far less luminous than classical Seyfert nuclei and QSOs. LINERs, the most common variety of such emission-line objects, comprise ~ 1/3 of nearby galaxies, and may serve as an important “missing link“ between normal and Seyfert galaxies. To shed light on the physical origin of LINERs, which remains controversial, we are conducting a high-resolution continuum survey of a representative sample of galaxies using the VLA to search for compact radio cores. We additionally discuss the dramatic radio variability in the LINER nucleus of M81.

High-density gas in bipolar outflow sources and active galactic nuclei

1986 ◽  
Vol 64 (4) ◽  
pp. 421-425 ◽  
Author(s):  
S. E. Persson
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Near Infrared ◽  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Detailed Comparison ◽  
Seyfert Galaxies ◽  
High Density ◽  
Young Stellar Objects ◽  
Molecular Outflow

The highest density regions near the base of the outflow in young stellar objects with bipolar molecular outflows are discussed. Bright emission lines of Ca II and O I characterize the spectra and lead to estimates of n ~ 1010 cm−3, temperatures of a few thousand Kelvins, and mass motions of several hundred kilometres per second. Typically the rate of momentum transfer within this region fails by more than an order of magnitude to provide the force necessary to drive the molecular outflow on the parsec scale. The overall near-infrared spectra of these young stars are similar to those of certain active galactic nuclei having strong Fe II emission.A comparison is made between the Ca II and O I lines in the infrared core source of the bipolar H II region S106 and in the Seyfert galaxy Mrk 42. The spectra are shown to be scaled versions of each other, and we conclude that the physical conditions are broadly similar in the high-density emission-line regions of these two objects. The Ca II lines appear self-reversed in both objects, but possible Ca II absorption in the underlying galaxy in Mrk 42 compromises the detailed comparison of line shapes. Nevertheless, it is likely that the geometries and velocity fields are also analogous. Derived parameters of the emission-line regions in S106 and the Seyfert galaxies I Zw 1 and Mrk 42 are compared.

scholarly journals VLBA Imaging of a Large Sample of Blazars

1998 ◽  
Vol 164 ◽  
pp. 159-160
Author(s):  
J. M. Attridge ◽  
D. H. Roberts ◽  
J. F.C. Wardle
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Active Galactic Nuclei ◽  
Ambient Medium ◽  
Surrounding Medium ◽  
Galactic Nuclei ◽  
Large Sample ◽  
Field Lines ◽  
5 Ghz ◽  
The Magnetic Field

AbstractAs part of our continuing study of parsec-scale magnetic fields in active galactic nuclei we have obtained deep polarization-sensitive images of the blazar 1055+018 with the VLBA at 5 GHz. These dramatic images reveal a magnetized layer of material on the outer surfaces of the jet, distinct from the bulk of the jet. This morphology suggests interaction of the jet with the surrounding medium, the resulting shear stretching the magnetic field lines in the direction of the flow. Further multi-frequency polarization-sensitive observations of 1055+018 offer the opportunity to study radio jet-ambient medium interactions in detail.

The GLEAM 4-Jy Sample: The brightest radio-sources in the southern sky

2019 ◽  
Vol 15 (S356) ◽  
pp. 375-375
Author(s):  
Sarah White
Keyword(s):  
Radio Emission ◽  
Active Galactic Nuclei ◽  
Visual Inspection ◽  
Low Frequency ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Relativistic Jets ◽  
The Galaxy ◽  
Murchison Widefield Array ◽  
Past Activity

AbstractLow-frequency radio emission allows powerful active galactic nuclei (AGN) to be selected in a way that is unaffected by dust obscuration and orientation of the jet axis. It also reveals past activity (e.g. radio lobes) that may not be evident at higher frequencies. Currently, there are too few “radio-loud” galaxies for robust studies in terms of redshift-evolution and/or environment. Hence our use of new observations from the Murchison Widefield Array (the SKA-Low precursor), over the southern sky, to construct the GLEAM 4-Jy Sample (1,860 sources at S151MHz > 4 Jy). This sample is dominated by AGN and is 10 times larger than the heavily relied-upon 3CRR sample (173 sources at S178MHz > 10 Jy) of the northern hemisphere. In order to understand how AGN influence their surroundings and the way galaxies evolve, we first need to correctly identify the galaxy hosting the radio emission. This has now been completed for the GLEAM 4-Jy Sample – through repeated visual inspection and extensive checks against the literature – forming a valuable, legacy dataset for investigating relativistic jets and their interplay with the environment.

scholarly journals Chemical abundances in Seyfert galaxies – V. The discovery of shocked emission outside the AGN ionization axis

2020 ◽  
Vol 501 (1) ◽  
pp. L54-L59
Author(s):  
R A Riffel ◽  
O L Dors ◽  
M Armah ◽  
T Storchi-Bergmann ◽  
A Feltre ◽  
...  
Keyword(s):  
Electron Temperature ◽  
Active Galactic Nuclei ◽  
Direct Evidence ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Chemical Abundances ◽  
Temperature Distributions ◽  
Field Unit ◽  
Dusty Torus ◽  
Integral Field

ABSTRACT We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies: Mrk 79, Mrk 348, and Mrk 607 obtained from Gemini Multi-Object Spectrograph-integral field unit observations at spatial resolutions of ∼110–280 pc. We study the distributions of electron temperature in active galaxies and find temperatures varying in the range from ∼8000 to $\gtrsim 30\, 000\,$K. Shocks due to gas outflows play an important role in the observed temperature distributions of Mrk 79 and Mrk 348, while standard photoionization models reproduce the derived temperature values for Mrk 607. In Mrk 79 and Mrk 348, we find direct evidence for shock ionization with overall orientation orthogonal to the ionization axis, where shocks can be easily observed as the active galactic nuclei radiation field is shielded by the nuclear dusty torus. This also indicates that even when the ionization cones are narrow, the shocks can be much wider angle.

Sign in / Sign up

Export Citation Format

Share Document