scholarly journals Active galactic nuclei among the polar-ring galaxies

2021 ◽  
Author(s):  
D. V. Smirnov ◽  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Nuclear Activity ◽  
Polar Ring ◽  
Show Evidence ◽  
Ring Galaxies

Based on SDSS data the nuclear activity statistics of the polar-ring galaxies (PRGs) was investigated. BPT-diagrams for PRGs and comparison samples were plotted and analyzed. Obtained results show evidence of excess of active galactic nuclei among PRGs compared to regular objects. Possible interpretation of such effect is discussed.

scholarly journals Active Galactic Nuclei among Polar-Ring Galaxies

2020 ◽  
Vol 46 (8) ◽  
pp. 501-508
Author(s):  
D. V. Smirnov ◽  
V. P. Reshetnikov
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Polar Ring ◽  
Ring Galaxies

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.

The relation between the environment and nuclear activity in nearby QSOs: Defining a control sample

2020 ◽  
Vol 15 (S359) ◽  
pp. 339-341
Author(s):  
Bruna L. C. Araujo ◽  
Thaisa Storchi-Bergmann ◽  
Sandro B. Rembold
Keyword(s):  
Active Galactic Nuclei ◽  
Control Sample ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
Active Galaxies ◽  
Host Galaxies ◽  
Stellar Objects ◽  
Nuclear Activity ◽  
Quasi Stellar Objects

AbstractIn this study, we aim to investigate the relation between nuclear activity and the environment for luminous (L[O III] >7.63 × 1041 erg s–1) Active Galactic Nuclei (AGN) - that, at these luminosities are classified as quasi-stellar objects (QSOs) - using a sample of 436 type 2 QSOs. Recent studies suggest that there is an excess of interacting hosts in luminous AGN, indicating that interactions trigger the nuclear activity. In order to examine this, it is necessary to select a control sample of non-active galaxies, matched to the active ones by the properties of the host galaxies, such as distance and stellar mass. We present here the results of the search for such a control sample.

scholarly journals Compton Thick AGN

2013 ◽  
Vol 9 (S304) ◽  
pp. 112-118
Author(s):  
N. A. Levenson
Keyword(s):  
Active Galactic Nuclei ◽  
Geometric Distribution ◽  
Galactic Nuclei ◽  
Infrared Emission ◽  
Nuclear Activity ◽  
X Ray ◽  
Central Engine ◽  
Black Hole Growth ◽  
Hole Growth ◽  
X Ray Background

AbstractCompton thick active galactic nuclei (AGN), which are obscured by column density NH > 1.5 × 104 cm−2, can be difficult to identify. They are certainly cosmically significant, both in producing the observed cosmic X-ray background, and in providing a location where black hole growth is hidden from view. Here I review some recent results from surveys that provide indications of Compton thick AGN, considering X-ray, radio, and infrared selection techniques. I also offer a caution against using mid-infrared silicate features to measure line-of-sight obscuration to active galactic nuclei. Instead, these features better indicate the geometric distribution of dust that the central engine heats. I conclude that the outstanding problem of Compton thick AGN is not the cases where the obscuration is directly associated with the environment of the active nucleus itself, even in the most obscured examples. Instead, we still risk missing the completely buried AGN, which are obscured by large amounts of gas and dust over large solid angles. The solution to finding Compton thick AGN may be to begin the search based on infrared emission and star formation, and then select for nuclear activity.

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 11.4. Demographics of nuclear activity in nearby galaxies

1998 ◽  
Vol 184 ◽  
pp. 463-464
Author(s):  
Luis C. Ho ◽  
Alexei V. Filippenko ◽  
Wallace L. W. Sargent
Keyword(s):  
Active Galactic Nuclei ◽  
Luminosity Function ◽  
Galactic Nuclei ◽  
Optical Spectra ◽  
Complete Sample ◽  
High Quality ◽  
Nuclear Activity ◽  
Moderate Resolution ◽  
Nearby Galaxies ◽  
Scientific Results

Between 1984 and 1990 we conducted a survey at Palomar Observatory (Filippenko and Sargent 1985) to quantify the luminosity function of nearby active galactic nuclei (AGNs). The Hale 5 m telescope was used to obtain high-quality, moderate-resolution optical spectra of a nearly statistically complete sample of about 500 bright (BT ≤ 12.5 mag), northern (δ > 0°) galaxies (see Ho et al. 1995 for details). The survey has now been completed, and the first scientific results are reported in a series of papers by Ho et al. (1997a, b, c).

Role of environment on AGN activity

2019 ◽  
Vol 15 (S356) ◽  
pp. 171-171
Author(s):  
Amirnezam Amiri
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Galaxy Clusters ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
Local Universe ◽  
Nuclear Activity ◽  
Star Forming ◽  
Star Formation Activity

AbstractMotivated by the apparently conflicting results reported in the literature on the effect of environment on nuclear activity, we have carried out a new analysis by comparing the fraction of galaxies hosting active galactic nuclei (AGNs) in the most overdense regions (rich galaxy clusters) and the most underdense ones (voids) in the local universe. Exploiting the classical BPT diagnostics, we have extracted volume limited samples of star forming and AGN galaxies. We find that, at variance with star-forming galaxies, AGN galaxies have similar distributions of specific star formation rates and of galactic ages (as indicated by the Dn4000 parameter) both in clusters and in voids. In both environments galaxies hosting AGNs are generally old, with low star formation activity. The AGN fraction increases faster with stellar mass in clusters than in voids, especially above 1010.2 M⊙. Our results indicate that, in the local universe, the nuclear activity correlates with stellar mass and galaxy morphology and is weakly, if at all, affected by the local galaxy density.

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