scholarly journals Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas

2020 ◽  
Vol 6 (27) ◽  
pp. eaay9711 ◽  
Author(s):  
D. Krishnarao ◽  
R. A. Benjamin ◽  
L. M. Haffner
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Center ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Hydrogen Gas ◽  
Emission Lines ◽  
Neutral Gas ◽  
Optical Line ◽  
Tilted Disk

Optical emission lines are used to categorize galaxies into three groups according to their dominant central radiation source: active galactic nuclei, star formation, or low-ionization (nuclear) emission regions [LI(N)ERs] that may trace ionizing radiation from older stellar populations. Using the Wisconsin H-Alpha Mapper, we detect optical line emission in low-extinction windows within eight degrees of Galactic Center. The emission is associated with the 1.5-kiloparsec-radius “Tilted Disk” of neutral gas. We modify a model of this disk and find that the hydrogen gas observed is at least 48% ionized. The ratio [NII] λ6584 angstroms/Hα λ6563 angstroms increases from 0.3 to 2.5 with Galactocentric radius; [OIII] λ5007 angstroms and Hβ λ4861 angstroms are also sometimes detected. The line ratios for most Tilted Disk sightlines are characteristic of LI(N)ER galaxies.

scholarly journals The Compact Magnetic Field Structures of AGN from Space VLBI Polarization Observations

2001 ◽  
Vol 205 ◽  
pp. 134-135
Author(s):  
D.C. Gabuzda ◽  
J.L. Gómez
Keyword(s):  
Magnetic Field ◽  
Active Galactic Nuclei ◽  
Linear Polarization ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Emission Mechanism ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Bl Lac ◽  
Optical Line

BL Lacertae objects are active galactic nuclei with weak, sometimes undetectable, optical line emission and strong variability in total intensity and linear polarization over a broad range of wavelengths from ultraviolet to radio. It is believed that synchrotron radiation is the dominant emission mechanism virtually throughout the spectrum. Their strong linear polarization makes BL Lac objects prime targets for space VLBI polarization observations.

scholarly journals The Relationship of Hard X‐Ray and Optical Line Emission in Low‐Redshift Active Galactic Nuclei

2005 ◽  
Vol 634 (1) ◽  
pp. 161-168 ◽  
Author(s):  
T. M. Heckman ◽  
A. Ptak ◽  
A. Hornschemeier ◽  
G. Kauffmann
Keyword(s):  
Active Galactic Nuclei ◽  
Line Emission ◽  
Galactic Nuclei ◽  
X Ray ◽  
Optical Line ◽  
Relationship Of ◽  
The Relationship

scholarly journals Infrared [FeII] and H2 Line Emission in Active Galactic Nuclei

1989 ◽  
Vol 134 ◽  
pp. 365-371
Author(s):  
A.F.M. Moorwood ◽  
E. Oliva
Keyword(s):  
Active Galactic Nuclei ◽  
Supernova Remnants ◽  
Large Scale ◽  
Large Fraction ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
Detection Frequency ◽  
Spatial Displacements

Infrared spectra around [FeII](1.644μm), H2 (v = 1-0 S(1) at 2.121μm) and Brγ (H 7-4 at 2.167μm) have been obtained of 35 emission line nuclei whose optical spectra range from pure HII regionlike to Seyfert 1. All three emission lines have been detected in a large fraction of those nuclei exhibiting starburst activity but not in “pure” Seyferts. The highest detection frequency, however, was found for composite nuclei showing evidence for both starburst and Seyfert activity. Several arguments suggest that both the [FeII] and H2 are shock excited and could be largely attributed to supernova remnants. The fact that the [FeII]/Brγ and H2/Brγ ratios tend to be somewhat larger in composite than in pure starburst nuclei, however, plus significant spatial displacements between the [FeII] and H2 emitting regions found recently during follow-up observations of selected galaxies suggest that large scale phenomena, e.g. SN winds or mass outflows from AGN, may also be important.

scholarly journals MODELING THE SS 433 JET BENDS

2008 ◽  
Vol 17 (10) ◽  
pp. 1925-1930 ◽  
Author(s):  
H. L. MARSHALL ◽  
CLAUDE R. CANIZARES ◽  
NORBERT S. SCHULZ ◽  
SEBASTIAN HEINZ ◽  
TODD C. HILLWIG ◽  
...  
Keyword(s):  
Emission Measure ◽  
Line Emission ◽  
Optical Emission ◽  
Local Environment ◽  
Emission Lines ◽  
X Ray ◽  
Ss 433 ◽  
Jet Cooling ◽  
Doppler Shifts ◽  
Optical Line

We fit Chandra HETGS data obtained for the unusual X-ray binary SS 433. While line strengths and continuum levels hardly change, the jet Doppler shifts show aperiodic variations that probably result from shocks in interactions with the local environment. The X-ray and optical emission line regions are found to be related but not coincident as the optical line emission persists for days while the X-ray emission lines fade in less than 5000 s. The X-ray spectrum of the blueshifted jet shows over two dozen emission lines from plasma at a variety of temperatures. The emission measure distribution derived from the spectrum can be used to test jet cooling models.

Radio galaxies with and without emission lines

2020 ◽  
Vol 15 (S359) ◽  
pp. 396-401
Author(s):  
Grażyna Stasińska ◽  
Natalia Vale Asari ◽  
Dorota Kozieł-Wierzbowska
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Equivalent Width ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Radio Galaxies ◽  
Emission Lines ◽  
The Common ◽  
Black Hole Masses

AbstractUsing the recent ROGUE I catalogue of galaxies with radio cores (Kozie_l-Wierzbowska et al. 2020) and after selecting the objects which are truly radio active galactic nuclei, AGNs, (which more than doubles the samples available so far), we perform a thorough comparison of the properties of radio galaxies with and without optical emission lines (galaxies where the equivalent width of Hα is smaller than 3Å are placed in the last category). We do not find any strong dichotomy between the two classes as regards the radio luminosities or black hole masses. The same is true when using the common classification into high- and low-excitation radio galaxies (HERGs and LERGs respectively).

scholarly journals The optical emission lines of type 1 X-ray bright Active Galactic Nuclei

2014 ◽  
Vol 54 (7) ◽  
pp. 1382-1388 ◽  
Author(s):  
G. La Mura ◽  
M. Berton ◽  
S. Ciroi ◽  
V. Cracco ◽  
F. Di Mille ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Emission Lines ◽  
X Ray

scholarly journals A bayesian-like approach to derive chemical abundances in type-2 active galactic nuclei based on photoionization models

2019 ◽  
Vol 489 (2) ◽  
pp. 2652-2668 ◽  
Author(s):  
E Pérez-Montero ◽  
O L Dors ◽  
J M Vílchez ◽  
R García-Benito ◽  
M V Cardaci ◽  
...  
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Chemical Properties ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Emission Lines ◽  
Chemical Abundances ◽  
Star Forming ◽  
Large Dispersion

Abstract We present a new methodology for the analysis of the emission lines of the interstellar medium in the narrow-line regions around type-2 active galactic nuclei. Our aim is to provide a recipe that can be used for large samples of objects in a consistent way using different sets of optical emission lines that takes into the account possible variations from the O/H–N/O relation to use [N ii] lines. Our approach consists of a bayesian-like comparison between certain observed emission-line ratios sensitive to total oxygen abundance, nitrogen-to-oxygen ratio, and ionization parameter with the predictions from a large grid of photoionization models calculated under the most usual conditions in this environment. We applied our method to a sample of Seyfert 2 galaxies with optical emission-line fluxes and determinations of their chemical properties from detailed models in the literature. Our results agree within the errors with other results and confirm the high metallicity of the objects of the sample, with N/O values consistent with a large secondary production of N, but with a large dispersion. The obtained ionization parameters for this sample are much larger than those for star-forming object at the same metallicity.

scholarly journals Spectral Monitoring of AGN: Preliminary Results for Ark 564 and Arp 102B

2011 ◽  
Vol 20 (3) ◽  
Author(s):  
A. I. Shapovalova ◽  
L. Č. Popović ◽  
D. Ilić ◽  
A. Kovačević ◽  
J. Kovačević ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Radio Galaxy ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Emission Lines ◽  
Broad Line ◽  
Preliminary Results ◽  
Line Shapes ◽  
Spectral Monitoring

AbstractWe present preliminary results of the long-term spectral monitoring of two active galactic nuclei with different broad line shapes: Ark 564 and Arp 102B. Ark 564 is a bright nearby narrow-line Syfert 1 (NLS1) galaxy with relatively narrow permitted optical emission lines and a high Fe II/Hβ ratio, while Arp 102B is a nearby broad-line radio galaxy with broad double-peaked Balmer emission lines. The spectra of Ark 564 were observed during 11-year period (1999-2009) and the spectra of Arp 102B in the 12-year period (1998-2009), with SAO 6 m and 1 m telescopes (Russia) and the OAGH 2.1 m telescope (Cananea, Mexico).

scholarly journals A new tool to derive chemical abundances in type-2 active galactic nuclei

2019 ◽  
Vol 15 (S356) ◽  
pp. 61-65
Author(s):  
Rubén García-Benito ◽  
Enrique Pérez-Montero ◽  
Oli L. Dors ◽  
José M. Vlchez ◽  
Monica V. Cardaci ◽  
...  
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Direct Method ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Emission Lines ◽  
Chemical Abundances ◽  
Line Region ◽  
Oxygen Ratio

AbstarctWe present a new tool for the analysis of the optical emission lines of the gas in the Narrow Line Region (NLR) around Active Galactic Nuclei (AGNs). This new tool can be used in large samples of objects in a consistent way using different sets of optical emission-lines taking into the account possible variations from the O/H - N/O relation. The code compares certain observed emission-line ratios with the predictions from a large grid of photoionization models calculated under the most usual conditions in the NLR of AGNs to calculate the total oxygen abundance, nitrogen-to-oxygen ratio and ionization parameter. We applied our method to a sample of Seyfert 2 galaxies with optical emission-line fluxes from the literature. Our results confirm the high metallicity of the objects of the sample and provide consistent values with the direct method. The usage of models to calculate precise ICFs is mandatory when only optical emission lines are available to derive chemical abundances using the direct method in NLRs of AGN.

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