scholarly journals Redshift Distribution of Quasi-Stellar Objects and the Radio Source Counts

1972 ◽  
Vol 44 ◽  
pp. 464-469
Author(s):  
Vahé Petrosian
Keyword(s):  
Radio Source ◽  
Large Scale ◽  
Redshift Distribution ◽  
Stellar Objects ◽  
Quasi Stellar Objects

The evolution of QSOs and the reality of their apparent cutoff for z > 2.3 is determined using their large scale redshift distribution. The contributions of QSRs to radio source counts are calculated on the basis of possible evolution of QSOs having z > 2.2.

scholarly journals The Large-Scale Variations of Quasi-Stellar Objects

1972 ◽  
Vol 44 ◽  
pp. 283-284 ◽  
Author(s):  
W. H. McCrea
Keyword(s):  
Large Scale ◽  
High Peak ◽  
Stellar Objects ◽  
Standard Object ◽  
Quasi Stellar Objects ◽  
The Mean ◽  
Optical Brightness ◽  
Very High

The proposition for consideration is:A QSO is an approximately standard object: it has an approximately standard history consisting mainly of an increase of optical brightness to a very high peak, and a subsequent decline. I suggest that the history has a relevant duration of about 106 yr, and that the total increase of brightness is by a factor about 103, while the mean brightness is of the order of 1% of the peak brightness (so that the peak is rather sharp).

A discussion on infared astronomy - Quasi-stellar objects

1969 ◽  
Vol 264 (1150) ◽  
pp. 263-266 ◽  
Keyword(s):  
Infrared Spectrum ◽  
Radio Source ◽  
Infrared Emission ◽  
Present Knowledge ◽  
Stellar Objects ◽  
Normal Galaxy ◽  
Infrared Measurements ◽  
Quasi Stellar Objects ◽  
Infrared Wavelengths ◽  
The Subject

Our knowledge of the infrared emission from quasi-stellar objects is developing rapidly at the present time so I shall not give a systematic survey of the subject. I prefer rather to mention what appear to be the highlights of our present knowledge. First among these highlights comes the behaviour of 3C 273 B. This, the first quasi-stellar radio source to be discovered (redshift z = 0.158, Schmidt 1963), emits more energy at infrared wavelengths tha n at all other wavelengths combined. The first infrared measurements were made by H . L. Johnson (1964) at wavelengths of 0.87 μm ( I filter) and 2.2 μm ( K filter), using the 28 in. telescope of the Lunar and Planetary Laboratory at Tucson, Arizona, and a PbS cell. Measurements at longer wavelengths have since been made (Low & Johnson 1965), but already Johnson was able to state that the infrared spectrum of 3C 273 B was unlike that known for any star, or as it turned out (Johnson 1966) for any normal galaxy.

scholarly journals The Clustering and Evolution of QSOs

1990 ◽  
Vol 43 (2) ◽  
pp. 251 ◽  
Author(s):  
BJ Boyle
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Significant Progress ◽  
Stellar Objects ◽  
Recent Advances ◽  
Quasi Stellar Objects ◽  
The Universe ◽  
Made In

Recent advances in instrumentation, particularly at the Anglo-Australian Telescope, have greatly increased the number of quaSi-stellar objects (QSOs) identified at faint magnitudes (B> 20 mag) and high redshifts (z> 2.2). As a result, significant progress has been made in the study of QSO clustering and evolution in the last two to three years. This paper reviews the results obtained and discusses their relevance to models of galaxy formation and the large-scale structure of the universe.

scholarly journals Principal component analysis tomography in near-infrared integral field spectroscopy of young stellar objects – I. Revisiting the high-mass protostar W33A

2021 ◽  
Vol 503 (1) ◽  
pp. 270-291
Author(s):  
F Navarete ◽  
A Damineli ◽  
J E Steiner ◽  
R D Blum
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Rotation Axis ◽  
Principal Component ◽  
Young Stellar Objects ◽  
High Mass ◽  
Continuum Emission ◽  
Rotating Disc ◽  
Stellar Objects ◽  
K Band

ABSTRACT W33A is a well-known example of a high-mass young stellar object showing evidence of a circumstellar disc. We revisited the K-band NIFS/Gemini North observations of the W33A protostar using principal components analysis tomography and additional post-processing routines. Our results indicate the presence of a compact rotating disc based on the kinematics of the CO absorption features. The position–velocity diagram shows that the disc exhibits a rotation curve with velocities that rapidly decrease for radii larger than 0.1 arcsec (∼250 au) from the central source, suggesting a structure about four times more compact than previously reported. We derived a dynamical mass of 10.0$^{+4.1}_{-2.2}$ $\rm {M}_\odot$ for the ‘disc + protostar’ system, about ∼33 per cent smaller than previously reported, but still compatible with high-mass protostar status. A relatively compact H2 wind was identified at the base of the large-scale outflow of W33A, with a mean visual extinction of ∼63 mag. By taking advantage of supplementary near-infrared maps, we identified at least two other point-like objects driving extended structures in the vicinity of W33A, suggesting that multiple active protostars are located within the cloud. The closest object (Source B) was also identified in the NIFS field of view as a faint point-like object at a projected distance of ∼7000 au from W33A, powering extended K-band continuum emission detected in the same field. Another source (Source C) is driving a bipolar $\rm {H}_2$ jet aligned perpendicular to the rotation axis of W33A.

The properties of the dusty inner regions of nearby QSOs

2019 ◽  
Vol 15 (S356) ◽  
pp. 95-95
Author(s):  
Itziar Aretxaga
Keyword(s):  
Star Formation ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Stellar Objects ◽  
X Ray ◽  
Mir Spectroscopy ◽  
Polycyclic Aromatic ◽  
Quasi Stellar Objects

AbstractWe present MIR spectroscopy and photometry obtained with CanariCam on the 10.4 m Gran Telescopio CANARIAS for a sample of 20 nearby, MIR bright and X-ray luminous quasi-stellar objects (QSOs). We find that for the majority of QSOs the MIR emission is unresolved at angular scales ∼0.3 arcsec. We derive the properties of the dusti tori that surround the nucleus based on these observations and find significant differences in the parameters compared with a sample of Seyfert 1 and 2 nuclei. We also find evidence for polycyclic aromatic hydrocarbon (PAH) features in the spectra, indicative of star formation, more centrally peaked (on scales of a few hundred pc) than previously believed.

scholarly journals Classification of Compact Objects: QSS, QSOs, N-Type and Compact Galaxies, Seyfert and Galactic Nuclei

1972 ◽  
Vol 44 ◽  
pp. 97-103
Author(s):  
W. W. Morgan
Keyword(s):  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Classification Criteria ◽  
Compact Objects ◽  
Stellar Objects ◽  
Quasi Stellar Objects ◽  
Compact Galaxies

Some methods currently in use for the classification of the optical forms of the ‘compact’ galaxies and quasi-stellar objects are reviewed. It is shown that the category ‘Seyfert Galaxy’ is basically a spectroscopic (rather than a form) classification.An optical form-classification is described which is, in principle, identical with published classification criteria for QSO, N-type, and compact objects. The importance of maintaining rigid form-standards is emphasized.

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