scholarly journals Correlation between Galaxies and Quasi‐stellar Objects in the Sloan Digital Sky Survey: A Signal from Gravitational Lensing Magnification?

2003 ◽  
Vol 589 (1) ◽  
pp. 82-99 ◽  
Author(s):  
Enrique Gaztanaga
Keyword(s):  
Gravitational Lensing ◽  
Sloan Digital Sky Survey ◽  
Stellar Objects ◽  
Sky Survey ◽  
Quasi Stellar Objects

scholarly journals Fundamental differences in the radio properties of red and blue quasars: insight from the LOFAR Two-metre Sky Survey (LoTSS)

2020 ◽  
Vol 494 (3) ◽  
pp. 3061-3079 ◽  
Author(s):  
D J Rosario ◽  
V A Fawcett ◽  
L Klindt ◽  
D M Alexander ◽  
L K Morabito ◽  
...  
Keyword(s):  
Star Formation ◽  
Control Sample ◽  
Low Frequency ◽  
Galactic Nuclei ◽  
Sloan Digital Sky Survey ◽  
Stellar Objects ◽  
Radio Detection ◽  
Sky Survey ◽  
Quasi Stellar Objects ◽  
First Time

ABSTRACT Red quasi-stellar objects (QSOs) are a subset of the luminous end of the cosmic population of active galactic nuclei (AGNs), most of which are reddened by intervening dust along the line of sight towards their central engines. In recent work from our team, we developed a systematic technique to select red QSOs from the Sloan Digital Sky Survey, and demonstrated that they have distinctive radio properties using the Faint Images of the Radio Sky at Twenty centimetres radio survey. Here we expand our study using low-frequency radio data from the LOFAR Two-metre Sky Survey (LoTSS). With the improvement in depth that LoTSS offers, we confirm key results: Compared to a control sample of normal ‘blue’ QSOs matched in redshift and accretion power, red QSOs have a higher radio detection rate and a higher incidence of compact radio morphologies. For the first time, we also demonstrate that these differences arise primarily in sources of intermediate radio loudness: Radio-intermediate red QSOs are × 3 more common than typical QSOs, but the excess diminishes among the most radio-loud systems and the most radio-quiet systems in our study. We develop Monte Carlo simulations to explore whether differences in star formation could explain these results, and conclude that, while star formation is an important source of low-frequency emission among radio-quiet QSOs, a population of AGN-driven compact radio sources is the most likely cause for the distinct low-frequency radio properties of red QSOs. Our study substantiates the conclusion that fundamental differences must exist between the red and normal blue QSO populations.

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.

scholarly journals A spectroscopic survey of Abell 1703: is it a rare relaxed cluster hosting a radio halo or a usual merging system?

2020 ◽  
Vol 492 (2) ◽  
pp. 2405-2417 ◽  
Author(s):  
W Boschin ◽  
M Girardi ◽  
F Gastaldello
Keyword(s):  
Gravitational Lensing ◽  
Statistical Tests ◽  
Galaxy Cluster ◽  
Theoretical Models ◽  
Sloan Digital Sky Survey ◽  
Cluster Galaxies ◽  
Radio Halo ◽  
Sky Survey ◽  
Galaxies Kinematics ◽  
First Moment

ABSTRACT We present the study of the internal dynamics of the intriguing galaxy cluster Abell 1703, a system hosting a probable giant radio halo whose dynamical status is still controversial. Our analysis is based on unpublished spectroscopic data acquired at the Italian Telescopio Nazionale Galileo and data publicly available in the literature. We also use photometric data from the Sloan Digital Sky Survey. We select 147 cluster members and compute the cluster redshift 〈z〉 ∼ 0.277 and the global line-of-sight velocity dispersion σv ∼ 1300 km s−1. We infer that Abell 1703 is a massive cluster: M200 ∼ 1–2 × 1015 M⊙. The results of our study disagree with the picture of an unimodal, relaxed cluster as suggested by previous studies based on the gravitational lensing analysis and support the view of a perturbed dynamics proposed by recent works based on Chandra X-ray data. The first strong evidence of a dynamically disturbed cluster comes from the peculiarity of the BCG velocity with respect to the first moment of the velocity distribution of member galaxies. Moreover, several statistical tests employed to study the cluster galaxies kinematics find significant evidence of substructure, being Abell 1703 composed by at least two or three subclumps probably caught after the core–core passage. In this observational scenario, the suspected existence of a radio halo in the centre of this cluster is not surprising and well agrees with the theoretical models describing diffuse radio sources in clusters.

scholarly journals Further Identifications Of Radio Sources Between Declinations 0° And 20°

1966 ◽  
Vol 19 (3) ◽  
pp. 471 ◽  
Keyword(s):  
Radio Sources ◽  
Stellar Objects ◽  
Sky Survey ◽  
Position Data ◽  
Quasi Stellar Objects

Clarke, Bolton, and Shimmins (1966) have recently suggested identifications for 138 of the radio sources listed in the Parkes catalogue for declinations 0� to +20� (Day, Shimmins, Ekers, and Cole 1966). The identifications were made from inspection of the Palomar Sky Survey plates in areas 2' arc square centred on the catalogue positions. In general, identifications were suggested only for galaxies or possible quasi-stellar objects brighter than 17m . 5, in order to avoid the possibility of chance coincidences. Where objects fainter than 17m . 5 were suggested, position data of higher accuracy were available, due principally to unpublished measurements by Shimmins, Clarke, and Ekers with the 210 ft telescope.

scholarly journals New Optical Identifications from the Parkes 2700 MHz Resurvey of the ± 4° Declination Zone

1982 ◽  
Vol 35 (2) ◽  
pp. 207 ◽  
Author(s):  
Ann Savage ◽  
JG Bolton ◽  
Jenny Trett
Keyword(s):  
Radio Sources ◽  
Stellar Objects ◽  
Sky Survey ◽  
Quasi Stellar Objects ◽  
Optical Identifications

Identifications are suggested for 59 radio sources from the resurvey of declination zone �4�, 27 with galaxies and 32 with stellar objects; 19 of the latter are confirmed as quasi-stellar objects (QSOs). The identifications were made from the Palomar Sky Survey prints plus supplementary plates taken with the Palomar and U.K. Schmidt telescopes and the Anglo-Australian 3�9 m telescope.

scholarly journals Probing the missing baryons with the Sunyaev-Zel’dovich effect from filaments

2019 ◽  
Vol 624 ◽  
pp. A48 ◽  
Author(s):  
Anna de Graaff ◽  
Yan-Chuan Cai ◽  
Catherine Heymans ◽  
John A. Peacock
Keyword(s):  
Gravitational Lensing ◽  
Sloan Digital Sky Survey ◽  
Low Density ◽  
Local Universe ◽  
Sky Survey ◽  
The Galaxy ◽  
Sunyaev Zel'dovich Effect ◽  
Galaxy Halo ◽  
The Universe ◽  
Sources Of Contamination

Observations of galaxies and galaxy clusters in the local universe can account for only ∼10% of the total baryon content. Cosmological simulations predict that the “missing baryons” are spread throughout filamentary structures in the cosmic web, forming a low-density gas with temperatures of 105−107 K. We search for this warm-hot intergalactic medium (WHIM) by stacking the Planck Compton y-parameter map of the thermal Sunyaev-Zel’dovich (tSZ) effect for 1 002 334 pairs of CMASS galaxies from the Sloan Digital Sky Survey. We model the contribution from the galaxy halo pairs assuming spherical symmetry, finding a residual tSZ signal at the 2.9σ level from a stacked filament of length 10.5 h−1 Mpc with a Compton parameter magnitude y = (0.6 ± 0.2)×10−8. We consider possible sources of contamination and conclude that bound gas in haloes may contribute only up to 20% of the measured filamentary signal. To estimate the filament gas properties we measure the gravitational lensing signal for the same sample of galaxy pairs; in combination with the tSZ signal, this yields an inferred gas density of ρb = (5.5 ± 2.9) × ρ̄b with a temperature T = (2.7 ± 1.7) × 106 K. This result is consistent with the predicted WHIM properties, and overall the filamentary gas can account for 11 ± 7% of the total baryon content of the Universe. We also see evidence that the gas filament extends beyond the galaxy pair. Averaging over this longer baseline boosts the significance of the tSZ signal and increases the associated baryon content to 28 ± 12% of the global value.

scholarly journals A gravitational lensing detection of filamentary structures connecting luminous red galaxies

2020 ◽  
Vol 633 ◽  
pp. A89 ◽  
Author(s):  
Qianli Xia ◽  
Naomi Robertson ◽  
Catherine Heymans ◽  
Alexandra Amon ◽  
Marika Asgari ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Critical Density ◽  
Average Density ◽  
Sloan Digital Sky Survey ◽  
Weak Lensing ◽  
Luminous Red Galaxies ◽  
Sky Survey ◽  
Combining Data ◽  
Red Galaxies ◽  
Cluster Sequence

We present a weak lensing detection of filamentary structures in the cosmic web, combining data from the Kilo-Degree Survey, the Red Cluster Sequence Lensing Survey, and the Canada-France-Hawaii Telescope Lensing Survey. The line connecting luminous red galaxies with a separation of 3 − 5 h−1 Mpc was chosen as a proxy for the location of filaments. We measured the average weak lensing shear around ∼11 000 candidate filaments selected in this way from the Sloan Digital Sky Survey. After nulling the shear induced by the dark matter haloes around each galaxy, we reported a 3.4σ detection of an anisotropic shear signal from the matter that connects them. Adopting a filament density profile, motivated from N-body simulations, the average density at the centre of these filamentary structures was found to be 15 ± 4 times the critical density.

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