Anisotropic Emission and the Radio-Loud/Radio-Quiet Problem of Active Galactic Nuclei, Quasi-Stellar Objects

1996 ◽  
Vol 112 ◽  
pp. 909 ◽  
Author(s):  
W. A. Stein
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Stellar Objects ◽  
Quasi Stellar Objects ◽  
Anisotropic Emission

scholarly journals Quasi-stellar object redshift estimates from optical, near-infrared, and ultraviolet colours

2019 ◽  
Vol 629 ◽  
pp. A56 ◽  
Author(s):  
S. J. Curran ◽  
J. P. Moss
Keyword(s):  
Active Galactic Nuclei ◽  
Rest Frame ◽  
Near Infrared ◽  
Galactic Nuclei ◽  
Additional Contribution ◽  
Stellar Objects ◽  
Simple Estimate ◽  
Photometric Redshift ◽  
Wide Range ◽  
Quasi Stellar Objects

A simple estimate of the photometric redshift would prove invaluable to forthcoming continuum surveys on the next generation of large radio telescopes, as well as mitigating the existing bias towards the most optically bright sources. While there is a well-known correlation between the near-infrared K-band magnitude and redshift for galaxies, we find the K − z relation to break down for samples dominated by quasi-stellar objects. We hypothesise that this is due to the additional contribution to the near-infrared flux by the active galactic nucleus, and, as such, the K-band magnitude can only provide a lower limit to the redshift in the case of active galactic nuclei, which will dominate the radio surveys. From a large optical dataset, we find a tight relationship between the rest-frame (U − K)/(W2 − FUV) colour ratio and spectroscopic redshift over a sample of 17 000 sources, spanning z ≈ 0.1−5. Using the observed-frame ratios of (U − K)/(W2 − FUV) for redshifts of z ≲ 1, (I − W2)/(W3 − U) for 1 ≲ z ≲ 3, and (I − W2.5)/(W4 − R) for z ≳ 3, where W2.5 is the λ = 8.0 μm magnitude and the appropriate redshift ranges are estimated from the W2 (4.5 μm) magnitude, we find this to be a robust photometric redshift estimator for quasars. We suggest that the rest-frame U − K colour traces the excess flux from the AGN over this wide range of redshifts, although the W2 − FUV colour is required to break the degeneracy.

scholarly journals ADAPTIVE OPTICS IMAGING OF QUASI-STELLAR OBJECTS WITH DOUBLE-PEAKED NARROW LINES: ARE THEY DUAL ACTIVE GALACTIC NUCLEI?

2011 ◽  
Vol 739 (1) ◽  
pp. 44 ◽  
Author(s):  
D. J. Rosario ◽  
R. C. McGurk ◽  
C. E. Max ◽  
G. A. Shields ◽  
K. L. Smith ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Adaptive Optics ◽  
Galactic Nuclei ◽  
Stellar Objects ◽  
Adaptive Optics Imaging ◽  
Quasi Stellar Objects

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.

Interactions among Active Galaxies: An HI Perspective

2004 ◽  
Vol 217 ◽  
pp. 424-425
Author(s):  
Jeremy Lim ◽  
Cheng-Yu Kuo ◽  
Wen-Shuo Liau ◽  
Jenny Greene ◽  
Paul T. P. Ho
Keyword(s):  
Active Galactic Nuclei ◽  
Atomic Hydrogen ◽  
Direct Evidence ◽  
Galactic Nuclei ◽  
Active Galaxies ◽  
Optical Observations ◽  
Stellar Objects ◽  
Galaxy Interactions ◽  
Nuclear Activity ◽  
Quasi Stellar Objects

Galaxy-galaxy interactions is one of the leading candidates for triggering nuclear activity in galaxies. Such interactions are thought to be able to bring a fresh supply of gas to the center of a galaxy to fuel its resident supermassive black hole. Optical observations, however, do not reveal direct evidence for interactions among the majority of active galaxies. on the other hand, neutral atomic hydrogen (HI) gas has proven to be an exquisite tracer of galaxy-galaxy interactions, even when no such interactions are visible in the optical. Here, we describe our systematic HI imaging surveys of galaxies hosting active galactic nuclei (AGNs) and quasi-stellar objects (QSOs), and present a few illustrative results.

scholarly journals Quasi Stellar Objects and Active Galactic Nuclei

1984 ◽  
Vol 78 ◽  
pp. 443-456
Author(s):  
C. Barbieri
Keyword(s):  
Active Galactic Nuclei ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Physical Processes ◽  
Stellar Objects ◽  
Sky Survey ◽  
Quasi Stellar Objects ◽  
The One

The role of the Schmidt telescopes in the discovery of the Quasi Stellar Objects and of the Active Galactic Nuclei, and in the understanding of their properties was and continues to be of the greatest importance. Thousands of Radio-Sources have been quickly associated to their optical counterparts thanks to the worldwide availability of the Palomar Observatory Sky Survey plates and charts and more recently of the films of the ESO B Survey. Other thousands of QSOs and AGNs devoid of radio emission are found by the large Schmidts nowaday in operation. This wealth of data give fundamental cosmological knowledge and insight in the physical processes occuring in these objects. I'll concentrate in this Review on two specific topics, namely on the discovery techniques and on the study of the optical variability. To both subjects, the 67/92 cm Schmidt telescope here at Asiago has made significant contributions. The first topic is treated in several excellent papers, such as the one by M. Smith (1978) and the one by P. Veron (1983); the material presented in the second part is largely new. In the following, I'll use rather loosely the terms QSOs and AGNs to designate a variety of objects including Quasars (those QSOs in catalogs of Radio-Sources), high-redshift compact galaxies with emission lines, BL LACset similia.

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