scholarly journals Kiloparsec Scale Radio Structure in Active Galaxies

1983 ◽  
Vol 6 ◽  
pp. 467-480 ◽  
Author(s):  
A. S. Wilson
Keyword(s):  
Interstellar Medium ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Active Galaxies ◽  
Radial Acceleration ◽  
Radio Structure ◽  
Interstellar Clouds ◽  
Ram Pressure ◽  
The Galaxy

AbstractA substantial fraction of active galaxies contain linear radio sources with sizes of a few hundreds or thousands of parsecs. Such sources are found in essentially all classes of active galactic nuclei, including Seyfert galaxies of both types, X-ray selected active nuclei, radio galaxies and quasars. The radio emission is clearly energised by the active nucleus, probably in the form of a jet. A number of observable consequences of the interaction of the jet with the interstellar medium of the galaxy are discussed. These processes include jet disruption by instabilities, acceleration of cosmic rays by shocks or turbulence, ionization and radial acceleration of interstellar clouds, creation of a hot thermal component through the agency of shock waves and bending of the jet by the ram pressure of a rotating interstellar medium.

scholarly journals Population Analysis of Seyfert Galaxies in the Coma-Abell 1367 Supercluster

2012 ◽  
Author(s):  
Megan Jones ◽  
Eric Wilcots
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Population Analysis ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Active Galaxies ◽  
Environmental Correlation ◽  
Galaxy Groups ◽  
Level Of Activity ◽  
The Galaxy

We are studying the population of active galaxies residing both in and out of groups along the Coma-Abell 1367 supercluster to look at the occurrence of Seyfert galaxies. We are also measuring the level of activity, as defined by active galactic nuclei (AGN) and star formation rates in the galaxy groups. Our goal is then to relate this information to determine any environmental correlation of these two features. We report on the distribution of Seyfert galaxies as a function of environment across the supercluster and probe the characteristics of the population of groups that currently host at least one Seyfert. 

scholarly journals OH Megamasers and Active Galactic Nuclei

1988 ◽  
Vol 129 ◽  
pp. 261-262
Author(s):  
R.P. Norris
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Disk ◽  
Galactic Nuclei ◽  
Far Infrared ◽  
Active Galaxies ◽  
Radio Continuum ◽  
Substantial Fraction ◽  
Continuum Source ◽  
Maser Amplifier ◽  
The Galaxy

OH megamasers are believed to be active galaxies in which a substantial fraction of the OH gas in the disk of the galaxy is stimulated by the intense far-infrared flux from the active nucleus. The result is that the galactic disk acts as a maser amplifier, producing in the OH line an amplified image of the radio continuum source in the nucleus. Megamasers promise to be powerful tools for the study of active galaxies, provided we can determine what it is that turns an active galaxy into a megamaser. Here I examine the archetypal megamaser galaxy Arp220 and ask the question: what makes it different from other active galaxies?

scholarly journals Variability of Water Megamasers in AGN

2002 ◽  
Vol 19 (1) ◽  
pp. 88-90 ◽  
Author(s):  
Philip Maloney
Keyword(s):  
Interstellar Medium ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Time Varying ◽  
Interstellar Scintillation ◽  
The Galaxy ◽  
Show Evidence ◽  
Ngc 1068 ◽  
Water Masers

AbstractPowerful water masers have been detected in 23 active galactic nuclei (AGN) to date. Most of the sources that have been monitored show evidence for variability, which may be either intrinsic (response of the masers to a time-varying pump or background source) or extrinsic (the effects of scintillation in the interstellar medium of the Galaxy). I briefly review the examples in which these mechanisms may be operating (interstellar scintillation in the Circinus galaxy, a time-varying background source in Mrk 348, and a time-varying AGN luminosity in NGC 1068).

scholarly journals Relativistic Iron Kα Emission in Seyfert Galaxies

1997 ◽  
Vol 159 ◽  
pp. 36-39
Author(s):  
K. Nandra
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Relativistic Effects ◽  
Seyfert Galaxies ◽  
Active Galaxies ◽  
Line Profiles ◽  
Central Black Hole ◽  
Gaussian Profile ◽  
Central Regions ◽  
Excellent Description

AbstractEvidence is presented for widespread relativistic effects in the central regions of active galactic nuclei (AGN). A sample of 18 Seyfert 1 galaxies observed by ASCA show iron Kα emission which is resolved, with mean full width at half maximum (FWHM) ~ 50,000 km s−1 for a Gaussian profile. However, many of the line profiles are asymmetric. A strong red wing is indicative of gravitational redshifts close to a central black hole, and accretion-disk models provide an excellent description of the data. Such observations probe the innermost regions of AGN, and arguably provide the best evidence yet obtained for the existence of supermassive black holes in the centers of active galaxies.

scholarly journals Turbulence/outflows perpendicular to low-power jets in Seyfert galaxies

2019 ◽  
Vol 15 (S359) ◽  
pp. 464-466
Author(s):  
Giacomo Venturi ◽  
Alessandro Marconi ◽  
Matilde Mingozzi ◽  
Giovanni Cresci ◽  
Stefano Carniani ◽  
...  
Keyword(s):  
Low Power ◽  
Active Galactic Nuclei ◽  
Interaction Mechanism ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Near Ir ◽  
The Galaxy ◽  
Line Widths ◽  
Integral Field Spectrograph ◽  
Integral Field

AbstractWe present recent results from our MAGNUM survey of nearby active galactic nuclei (AGN), which exploits observations from the optical/near-IR integral field spectrograph MUSE at VLT. We detect strongly enhanced line widths in emission line maps of four galaxies perpendicularly to their low-power jets and AGN ionisation cones, indicative of turbulent/outflowing material. The observation of a similar phenomenon in other works suggests that it originates from an interaction mechanism between the jet and the galaxy disc through which it propagates.

scholarly journals Extended Emission-Line Regions Around AGN

1997 ◽  
Vol 159 ◽  
pp. 280-287
Author(s):  
A. Robinson
Keyword(s):  
Interstellar Medium ◽  
Emission Line ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Active Galaxies ◽  
Radio Sources ◽  
Relative Importance ◽  
High Excitation ◽  
Ambient Gas ◽  
Extended Emission

AbstractHigh-excitation extended emission-line nebulae around active galactic nuclei probably result either from photoionization of the interstellar medium by beamed continuum radiation, or dynamical interactions between radio sources and the ambient gas, or both. Here I discuss the models based on these mechanisms, and their relative importance in radio-quiet and radio-loud active galaxies.

scholarly journals Wolf-Rayet stars in Active Galactic Nuclei

1999 ◽  
Vol 193 ◽  
pp. 760-761
Author(s):  
Robin J.R. Williams ◽  
John E. Dyson ◽  
Judith J. Perry
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Active Galaxies ◽  
Emission Lines ◽  
Supply Rate ◽  
Stellar Cluster ◽  
Uv Emission ◽  
Ram Pressure

Starbursts, black holes and AGN have strong observational links, as discussed elsewhere in these proceedings. Perry & Dyson (1985 (PD), see also Perry 1994) studied the role of shocks around supernovae and stellar wind bubbles in the nuclei of active galaxies. Both the ejecta and the ambient ISM are initially shocked to high temperatures. PD found that while the shocked gas is maintained at high pressure by ram pressure, it cools rapidly, to then produce the observed optical and UV emission lines. The mass supply rate from the nuclear starburst, inferred from the strength of the emission lines, tallies well with that required by an accreting black hole to generate the observed luminosity. A symbiosis between a starburst stellar cluster and an accreting black hole naturally generates the observational features associated with QSOs.

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 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 Probing the cool ISM in galaxies via 21 cm H i absorption

2012 ◽  
Vol 8 (S292) ◽  
pp. 188-188
Author(s):  
J. R. Allison ◽  
E. M. Sadler ◽  
S. J. Curran ◽  
S. N. Reeves
Keyword(s):  
Spectral Line ◽  
Active Galactic Nuclei ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Host Galaxies ◽  
The Galaxy ◽  
Early Type Galaxy ◽  
Finding Method ◽  
Compact Array ◽  
Cold Gas

AbstractRecent targeted studies of associated H i absorption in radio galaxies are starting to map out the location, and potential cosmological evolution, of the cold gas in the host galaxies of Active Galactic Nuclei (AGN). The observed 21 cm absorption profiles often show two distinct spectral-line components: narrow, deep lines arising from cold gas in the extended disc of the galaxy, and broad, shallow lines from cold gas close to the AGN (e.g. Morganti et al. 2011). Here, we present results from a targeted search for associated H i absorption in the youngest and most recently-triggered radio AGN in the local universe (Allison et al. 2012b). So far, by using the recently commissioned Australia Telescope Compact Array Broadband Backend (CABB; Wilson et al. 2011), we have detected two new absorbers and one previously-known system. While two of these show both a broad, shallow component and a narrow, deep component (see Fig. 1), one of the new detections has only a single broad, shallow component. Interestingly, the host galaxies of the first two detections are classified as gas-rich spirals, while the latter is an early-type galaxy. These detections were obtained using a spectral-line finding method, based on Bayesian inference, developed for future large-scale absorption surveys (Allison et al. 2012a).

Sign in / Sign up

Export Citation Format

Share Document