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 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 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 Properties of X-ray detected far-IR AGN in the green valley

2019 ◽  
Vol 15 (S356) ◽  
pp. 147-151
Author(s):  
Antoine Mahoro ◽  
Mirjana Pović ◽  
Petri Väisänen ◽  
Pheneas Nkundabakura ◽  
Beatrice Nyiransengiyumva ◽  
...  
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Far Infrared ◽  
Mass Range ◽  
Infrared Emission ◽  
Active Galaxies ◽  
X Ray ◽  
Normal Galaxies ◽  
Using Data

AbstractIn this study, we analysed active galactic nuclei in the “green valley” by comparing active and non-active galaxies using data from the COSMOS field. We found that most of our X-ray detected active galactic nuclei with far-infrared emission have star formation rates higher than the ones of normal galaxies of the same stellar mass range.

scholarly journals 3.8. Are the stellar populations in starbursts, LINERs and Seyfert galaxies similar?

1998 ◽  
Vol 184 ◽  
pp. 105-106
Author(s):  
M. Joly ◽  
C. Boisson ◽  
D. Pelat ◽  
M. Serote Roos ◽  
M.J. Ward
Keyword(s):  
Active Galactic Nuclei ◽  
Stellar Population ◽  
Galactic Nuclei ◽  
Stellar Populations ◽  
Seyfert Galaxies ◽  
Activity Level ◽  
Substantial Fraction ◽  
Level Of Activity ◽  
Low Activity

It is well known that about 10% of galaxies harbour an Active Galactic Nuclei (AGN). A debated question is whether the activity influences the stellar population, or inversely, whether the level of activity is induced by the stellar population. By inspection of AGN spectra of low activity level, it is obvious that starlight contributes to a substantial fraction of the light.

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 Determining star-formation rates in Active Galactic Nuclei hosts via stellar population synthesis

2020 ◽  
Author(s):  
Rogério Riffel ◽  
Nicolas D Mallmann ◽  
Gabriele S Ilha ◽  
Thaisa Storchi-Bergmann ◽  
Rogemar A Riffel ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Active Galactic Nuclei ◽  
Stellar Population ◽  
Control Sample ◽  
Galactic Nuclei ◽  
Active Galaxies ◽  
Host Galaxy ◽  
Population Synthesis ◽  
Stellar Population Synthesis

Abstract The effect of active galactic nuclei (AGN) feedback on the host galaxy, and its role in quenching or enhancing star-formation, is still uncertain due to the fact that usual star-formation rate (SFR) indicators – emission-line luminosities based on the assumption of photoionisation by young stars – cannot be used for active galaxies as the ionising source is the AGN. We thus investigate the use of SFR derived from the stellar population and its relation with that derived from the gas for a sample of 170 AGN hosts and a matched control sample of 291 galaxies. We compare the values of SFR densities obtained via the Hα emission line ($\rm \Sigma SFR_{Gas}$) for regions ionised by hot stars according to diagnostic diagrams with those obtained from stellar population synthesis ($\rm \Sigma SFR_\star$) over the last 1 to 100 Myr. We find that the $\rm \Sigma SFR_\star$over the last 20 Myrs closely reproduces the $\rm \Sigma SFR_{Gas}$, although a better match is obtained via the transformation: $\mbox{log($ \rm \Sigma SFR_\star $)} = (0.872\pm 0.004)\mbox{log($\rm \Sigma SFR_{Gas}$)} -(0.075\pm 0.006)$ (or $\mbox{log($\rm \Sigma SFR_{Gas}$)} = (1.147\pm 0.005)\mbox{log($ \rm \Sigma SFR_\star $)} +(0.086\pm 0.080)$), which is valid for both AGN hosts and non-active galaxies. We also compare the reddening obtained via the gas Hα/Hβ ratio with that derived via the full spectral fitting in the stellar population synthesis. We find that the ratio between the gas and stellar extinction is in the range 2.64 ≤AVg/AV⋆ ≤ 2.85, in approximate agreement with previous results from the literature, obtained for smaller samples. We interpret the difference as being due to the fact that the reddening of the stars is dominated by that affecting the less obscured underlying older population, while the reddening of the gas is larger as it is associated to a younger stellar population buried deeper in the dust.

scholarly journals A Linkup Between Seyfert's and their Surroundings

1996 ◽  
Vol 171 ◽  
pp. 408-408
Author(s):  
A.P. Mahtessian ◽  
E.Ye. Khachikian ◽  
H. Tiersch
Keyword(s):  
Seyfert Galaxies ◽  
Physical Characteristics ◽  
Active Galaxies ◽  
Galaxy Groups ◽  
The Galaxy ◽  
Redshift Survey ◽  
Insight Into

The observed physical characteristics of galaxies are (at least partly) determined by the influence of the surroundings after the formation of the galaxies. The examination of the frequency of the occurence of active galaxies, i.e. Seyfert galaxies, in different galaxy systems compared to a sample of field galaxies gives possibly an insight into this problem.The galaxy groups were taken from the CfA redshift survey, the list of them is published in Mahtessian (1992, Soob. Byurakan. Obs. 65).

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 Constraining photoionization models with a reprojected optical diagnostic diagram

2020 ◽  
Vol 499 (4) ◽  
pp. 5749-5764 ◽  
Author(s):  
Xihan Ji ◽  
Renbin Yan
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Theoretical Models ◽  
Line Ratio ◽  
Star Forming ◽  
Optical Diagnostic ◽  
Diagnostic Diagram ◽  
Upper Limits ◽  
Nitrogen Abundance

ABSTRACT Optical diagnostic diagrams are powerful tools to separate different ionizing sources in galaxies. However, the model-constraining power of the most widely used diagrams is very limited and challenging to visualize. In addition, there have always been classification inconsistencies between diagrams based on different line ratios, and ambiguities between regions purely ionized by active galactic nuclei (AGNs) and composite regions. We present a simple reprojection of the 3D line ratio space composed of [N ii]λ6583/H α, [S ii]λλ6716, 6731/H α, and [O iii]λ5007/H β, which reveals its model-constraining power and removes the ambiguity for the true composite objects. It highlights the discrepancy between many theoretical models and the data loci. With this reprojection, we can put strong constraints on the photoionization models and the secondary nitrogen abundance prescription. We find that a single nitrogen prescription cannot fit both the star-forming locus and AGN locus simultaneously, with the latter requiring higher N/O ratios. The true composite regions stand separately from both models. We can compute the fractional AGN contributions for the composite regions, and define demarcations with specific upper limits on contamination from AGN or star formation. When the discrepancy about nitrogen prescriptions gets resolved in the future, it would also be possible to make robust metallicity measurements for composite regions and AGNs.

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.

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