scholarly journals A Search for Low-Level Seyfert Activity in the 500 Brightest Northern Galaxies

1987 ◽  
Vol 121 ◽  
pp. 451-460
Author(s):  
Alexei V. Filippenko ◽  
Wallace L. W. Sargent
Keyword(s):  
Active Galactic Nuclei ◽  
Luminosity Function ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
Full Width ◽  
Line Region ◽  
Wide Range ◽  
Hα Emission ◽  
Nearby Galaxies ◽  
Narrow Line Region

A sensitive search for intrinsically faint Seyfert nuclei in the 500 brightest northern galaxies is being conducted with the Hale 5.08 m telescope. The primary aim is to extend the luminosity function of active galactic nuclei (AGNs) to lower luminosities. Thus far, we have detected Hα emission having full-width near zero-intensity (FWZI) ≳ 4000 km s−1 in a significant fraction (≳10%) of nearby galaxies. Moreover, the narrow emission lines in a given nucleus often have markedly different widths, as shown in detail for M81. Those associated with high critical densities are generally the broadest, indicating that a very wide range of densities is present in the narrow-line region. The relative intensities of the lines can readily be explained with models in which clouds of gas having ne ≈ 102 to 107 cm−3 are photoionized by nonstellar radiation such as that produced by QSOs and luminous Seyfert 1 galaxies.

scholarly journals Studies of narrow emission lines in AGNs

1986 ◽  
Vol 119 ◽  
pp. 289-294
Author(s):  
Alexei V. Filippenko
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
As Species ◽  
Line Region ◽  
Narrow Line Region ◽  
High Velocity Clouds ◽  
Tight Correlation ◽  
Collisional Deexcitation ◽  
Narrow Emission

Optical spectra having moderately high resolution (~ 2 — 5 Å) are being used to study the profiles of narrow emission lines in active galactic nuclei (AGNs). It is often found that forbidden lines associated with high critical densities for collisional deexcitation are the broadest. A good example is [O III] λ4363 [ne(crit) ≈ 3 × 107 cm−3], whose width can be more than twice that of [O III] λ5007 [ne(crit) ≈ 8 × 105 cm−3]. The tight correlation between line width and ne(crit) implies that a much larger range of densities (∼ 102 — 107 cm−3) must be present among clouds in the narrow-line region than was previously believed. At times there almost appears to be a continuity between the narrow- and broad-line regions. In some objects the dense, high-velocity clouds are optically thick to ionizing radiation, since they emit [O I] λ6300 as well as species of much higher ionization (such as [Ne V] λ3426). These results help eliminate several difficulties in photoionization models of LINERs. It may also be possible to use the observed line widths as probes of the gravitational potential in AGNs.

scholarly journals Outflows in nearby AGNs

2009 ◽  
Vol 5 (H15) ◽  
pp. 245-246
Author(s):  
Thaisa Storchi-Bergmann
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Gas Kinematics ◽  
Integral Field Spectroscopy ◽  
Line Region ◽  
Mass Outflow ◽  
Kinematic Studies ◽  
Narrow Line Region ◽  
Integral Field ◽  
Velocity Channel

AbstractI report results of kinematic studies of the Narrow-Line Region (NLR) of nearby Active Galactic Nuclei (AGN) from integral field spectroscopy (IFS) obtained with the Gemini Telescopes, including mass outflow rates and corresponding kinetic power. The IFS has allowed the construction of velocity channel maps which provide a better coverage of the gas kinematics and do not support the presence of acceleration up to hundred parsec scales in the NLR as found in previous studies based solely on centroid velocity maps.

scholarly journals Detection of a double-peaked H α component from the accretion disc of NGC 4958

2019 ◽  
Vol 486 (1) ◽  
pp. 1138-1145
Author(s):  
T V Ricci ◽  
J E Steiner
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Outer Radius ◽  
Accretion Disc ◽  
Line Of Sight ◽  
Broad Component ◽  
Line Region ◽  
Inner Radius ◽  
The Galaxy ◽  
Narrow Line Region

Abstract Active Galactic Nuclei are objects associated with the presence of an accretion disc around supermassive black holes found in the very central region of galaxies with a well-defined bulge. In the optical range of the spectrum, a possible signature of the accretion disc is the presence of a broad double-peaked component that is mostly seen in H α. In this paper, we report the detection of a double-peaked feature in the H α line in the nucleus of the galaxy NGC 4958. The narrow-line region of this object has an emission that is typical of a low-ionization nuclear emission-line region galaxy, which is the usual classification for double-peaked emitters. A central broad component, related to the broad-line region of this object, is seen in H α and also in H β. We concluded that the double-peaked emission is emitted by a circular relativistic Keplerian disc with an inner radius ξi  = 570 ± 83, an outer radius ξo  = 860 ± 170 (both in units of GMSMBH/c2), an inclination to the line of sight i = 27.2 ± 0.7° and a local broadening parameter σ  = 1310 ± 70 km s−1.

scholarly journals The polarized signal from broad emission lines in AGNs

2019 ◽  
Vol 491 (1) ◽  
pp. 1-12 ◽  
Author(s):  
P Lira ◽  
R W Goosmann ◽  
M Kishimoto ◽  
R Cartier
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Position Angle ◽  
Emission Lines ◽  
Type I ◽  
Line Profiles ◽  
Scattering Media ◽  
Broad Emission ◽  
Line Region ◽  
Scattering Signal

ABSTRACT Using the stokes Monte Carlo radiative transfer code, we revisit the predictions of the spectropolarimetric signal from a disc-like broad emission line region (BLR) in type I active galactic nuclei due to equatorial scattering. We reproduce the findings of previous works, but only for a scatterer that is much more optically and geometrically thick than previously proposed. We also find that when taking into account the polarized emission from all regions of the scatterer, the swing of the polarization position angle (PA) is in the opposite direction to that originally proposed. Furthermore, we find that the presence of outflows in the scattering media can significantly change the observed line profiles, with the PA of the scattering signal being enhanced in the presence of radially outflowing winds. Finally, a characteristically different PA profile, shaped like an ‘M’, is seen when the scatterer is co-spatial with the BLR and radially outflowing.

scholarly journals DETERMINING INCLINATIONS OF ACTIVE GALACTIC NUCLEI VIA THEIR NARROW-LINE REGION KINEMATICS. II. CORRELATION WITH OBSERVED PROPERTIES

2014 ◽  
Vol 785 (1) ◽  
pp. 25 ◽  
Author(s):  
T. C. Fischer ◽  
D. M. Crenshaw ◽  
S. B. Kraemer ◽  
H. R. Schmitt ◽  
T. J. Turner
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Narrow Line ◽  
Line Region ◽  
Narrow Line Region

scholarly journals The narrow-line region of high-luminosity active galactic nuclei

1993 ◽  
Vol 410 ◽  
pp. 534 ◽  
Author(s):  
Beverley J. Wills ◽  
H. Netzer ◽  
M. S. Brotherton ◽  
Mingsheng Han ◽  
D. Wills ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Narrow Line ◽  
High Luminosity ◽  
Line Region ◽  
Narrow Line Region
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