A Search for HI Absorption in the Radio Spectra of the Quasi-Stellar Objects 4C 05.34 and PKS 0237-23

1975 ◽  
Vol 2 (6) ◽  
pp. 365-366 ◽  
Author(s):  
B.A. Peterson ◽  
J.D. Murray ◽  
A.E. Wright
Keyword(s):  
Emission Line ◽  
Intergalactic Medium ◽  
Mass Density ◽  
Emission Lines ◽  
Absorption Lines ◽  
Stellar Objects ◽  
Upper Limit ◽  
Quasi Stellar Objects ◽  
No Absorption

The ratio of the mass density in visible galaxies to the upper limit for the HI mass density determined from the lack of continuous Ly-α absorption in QSO spectra is 3 × 104. Thus, if galaxies form by condensation from an intergalactic medium, the process must be extremely efficient. Although no absorption due to a continuous distribution of intergalactic HI has been detected, many QSOs have been discovered that have absorption lines in their spectra, which have redshifts very different from the emission lines, and may be produced in clouds of integalactic HI. As would be expected if this were the case, the proportion of QSOs with absorption lines in their spectra is greatest for those which have large emission line redshifts. Another possibility, especially for those absorption lines in redshift systems with Zabs nearly equal to Zem , is that the absorption lines are produced in clouds surrounding the QSO.

scholarly journals Quasi-stellar objects acting as potential strong gravitational lenses in the SDSS-III BOSS survey

2019 ◽  
Vol 625 ◽  
pp. A56 ◽  
Author(s):  
Romain A. Meyer ◽  
Timothée Delubac ◽  
Jean-Paul Kneib ◽  
Frédéric Courbin
Keyword(s):  
Emission Line ◽  
Sloan Digital Sky Survey ◽  
Emission Lines ◽  
Gravitational Lenses ◽  
Stellar Objects ◽  
Sky Survey ◽  
Quasi Stellar Objects ◽  
Unique Approach ◽  
Algorithmic Search ◽  
Emission Line Galaxies

We present a sample of 12 quasi-stellar objects (QSOs) that potentially act as strong gravitational lenses on background emission line galaxies (ELG) or Lyman-α emitters (LAEs) selected through a systematic search of the 297 301 QSOs in the Sloan Digital Sky Survey (SDSS)-III Data Release 12. Candidates were identified by looking for compound spectra, where emission lines at a redshift larger than that of the quasar can be identified in the residuals after a QSO spectral template is subtracted from the observed spectra. The narrow diameter of BOSS fibers (2″) then ensures that the object responsible for the additional emission lines must lie close to the line of sight of the QSO and hence provides a high probability of lensing. Among the 12 candidates identified, nine have definite evidence for the presence of a background ELG identified by at least four higher-redshift nebular emission lines. The remaining three probable candidates present a strong asymmetrical emission line attributed to a background Lyman-α emitter (LAE). The QSO-ELG (QSO-LAE) lens candidates have QSO lens redshifts in the range 0.24 ≲ zQSO ≲ 0.66 (0.75 ≲ zQSO ≲ 1.23 ) and background galaxy redshifts in the range 0.48 ≲ zS, ELG ≲ 0.94 (2.17 ≲ zS, LAE ≲ 4.48). We show that the algorithmic search is complete at > 90% for QSO-ELG systems, whereas it falls at 40−60% for QSO-LAE, depending on the redshift of the source. Upon confirmation of the lensing nature of the systems, this sample may quadruple the number of known QSOs acting as strong lenses. We have determined the completeness of our search, which allows future studies to compute lensing probabilities of galaxies by QSOs and differentiate between different QSO models. Future imaging of the full sample and lens modelling offers a unique approach to study and constrain key properties of QSOs.

BLUESHIFTS IN ABSORPTION LINES OF QUASI-STELLAR OBJECTS?

2001 ◽  
Vol 10 (04) ◽  
pp. 443-464 ◽  
Author(s):  
D. BASU
Keyword(s):  
Emission Spectrum ◽  
Spectral Lines ◽  
Emission Lines ◽  
Absorption Lines ◽  
Absorption System ◽  
Stellar Objects ◽  
Quasi Stellar Objects ◽  
Ejection Mechanism

Possibility of misidentification of emission lines of QSOs and thereby missing detection of blueshifts have been suggested and demonstrated in literature. It is shown here that absorption lines observed in the spectra of QSOs may also have been misidentified. Plenty search lines are available at higher wavelengths (red/IR regions) for identification with observed absorption lines, although lines from lower wavelengths (UV/blue regions) are always considered for identification. Re-examination of the published spectra of ten QSOs shows that the observed absorption lines can be interpreted as blueshifted, with same or better accuracy and sometimes more convincingly than redshifts. Objects on the sight line are identified with same emission blueshift as the blueshift of the absorption system of the QSO, the emission spectrum of the QSO itself being of course interpreted as blueshifted as well. It is proposed that the absorbers are probably linked with the QSO either physically or tidally/gravitationally as a result of some ejection mechanism. The observed blueshifts of spectral lines in emission and absorption can be explained in a model comprising of multiple expanding universes.

Absorption lines in the spectra of low-redshift quasi-stellar objects

1978 ◽  
Vol 226 ◽  
pp. 21 ◽  
Author(s):  
B. M. Peterson ◽  
P. A. Strittmatter
Keyword(s):  
Absorption Lines ◽  
Stellar Objects ◽  
Quasi Stellar Objects

Emission-line variability and the broad-line region of quasi-stellar objects. I - Time scales and photon densities

1987 ◽  
Vol 322 ◽  
pp. 164 ◽  
Author(s):  
Wei Zheng ◽  
E. Margaret Burbridge ◽  
Harding E. Smith ◽  
Ross D. Cohen ◽  
Steven E. Bradley
Keyword(s):  
Emission Line ◽  
Time Scales ◽  
Broad Line ◽  
Stellar Objects ◽  
Broad Line Region ◽  
Line Region ◽  
Quasi Stellar Objects

Optical spectroscopy of BL Lac objects: TeV candidates

2020 ◽  
Vol 497 (1) ◽  
pp. 94-108 ◽  
Author(s):  
Simona Paiano ◽  
Renato Falomo ◽  
Aldo Treves ◽  
Riccardo Scarpa
Keyword(s):  
Lower Limit ◽  
Gamma Ray ◽  
Absorption Lines ◽  
Host Galaxies ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
Forbidden Transition ◽  
Bl Lac ◽  
Quasi Stellar Objects ◽  
Relationship Of

ABSTRACT We investigate the spectroscopic optical properties of gamma-ray sources detected with high significance above 50 GeV in the Third Catalog of Hard Fermi-LAT Sources and that are good candidates as TeV emitters. We focus on the 91 sources that are labelled by the Fermi team as BL Lac (BLL) objects or blazar candidates of uncertain type (BCUs), are in the Northern hemisphere, and are with unknown or uncertain redshift. We report here on GTC (Gran Telescopio Canarias) spectra (in the spectral range 4100–7750 Å) of 13 BCUs and 42 BLL objects. We are able to classify the observed targets as BLL objects and each source is briefly discussed. The spectra allowed us to determine the redshift of 25 objects on the basis of emission and/or absorption lines, finding 0.05 < z < 0.91. Most of the emission lines detected are due to forbidden transition of [O iii] and [N ii]. The observed line luminosity is found to be lower than that of quasi-stellar objects (QSOs) at similar continuum and could be reconciled with the line–continuum luminosity relationship of QSOs if a significant beaming factor is assumed. Moreover, for five sources we found intervening absorption lines that allow to set a spectroscopic lower limit of the redshift. For the remaining 25 sources, for which the spectra are lineless, a lower limit to z is given, assuming that the host galaxies are giant ellipticals.

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