Relevant bibliographies by topics / Quasars. 0

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Academic literature on the topic 'Quasars. 0'

Author: Grafiati
Published: 4 June 2021
Last updated: 28 January 2023

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Journal articles on the topic "Quasars. 0"

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Yue, Minghao, Xiaohui Fan, Jinyi Yang, and Feige Wang. "A Mock Catalog of Gravitationally-lensed Quasars for the LSST Survey." Astronomical Journal 163, no. 3 (February 22, 2022): 139. http://dx.doi.org/10.3847/1538-3881/ac4cb0.

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Abstract We present a mock catalog of gravitationally-lensed quasars at z qso < 7.5 with simulated images for the Rubin Observatory Legacy Survey of Space and Time (LSST). We adopt recent measurements of quasar-luminosity functions to model the quasar population, and use the CosmoDC2 mock galaxy catalog to model the deflector galaxies, which successfully reproduces the observed galaxy-velocity dispersion functions up to z d ∼ 1.5. The mock catalog is highly complete for lensed quasars with Einstein radius θ E > 0.″07 and quasar absolute magnitude M i < − 20. We estimate that there are ∼103 lensed quasars discoverable in current imaging surveys, and LSST will increase this number to ∼ 2.4 × 103. Most of the lensed quasars have image separation Δθ > 0.″5, which will at least be marginally resolved in LSST images with seeing of ∼0.″7. There will be ∼200 quadruply-lensed quasars discoverable in the LSST. The fraction of quad lenses among all discoverable lensed quasars is about ∼10%–15%, and this fraction decreases with survey depth. This mock catalog shows a large diversity in the observational features of lensed quasars, in terms of lensing separation and quasar-to-deflector flux ratio. We discuss possible strategies for a complete search of lensed quasars in the LSST era.
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Dultzin-Hacyan, Deborah, Paola Marziani, C. Alenka Negrete, and Jack W. Sulentic. "Quasar evolution: black hole mass and accretion rate determination." Proceedings of the International Astronomical Union 2, S238 (August 2006): 83–86. http://dx.doi.org/10.1017/s1743921307004735.

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AbstractAccurate measurements of emission line properties are crucial to understand the physics of the broad line region in quasars. This region consists of warm gas that is closest to the quasar central engine and has not been spatially resolved for almost all sources. We present here an analysis of optical and IR data for a large sample of quasars, covering the Hi Hβ spectral region in the redshift range 0 ≲ z ≲ 2.5. Spectra were interpreted within the framework of the the so-called “eigenvector 1” parameter space, which can be viewed as a tentative H-R diagram for quasars. We stress the lack of spectral evolution in the low ionization lines of quasars, with prominent Fe ii emission also at z ≳ 2. We also show how selection effects influence the ability to find quasars radiating at low Eddington ratio in flux-limited surveys. The quasar similarity at different redshift is probably due to the absence of super-Eddington radiators (at least within the caveats of black hole mass and Eddington ratio determination discussed in this paper) as well as to the limited Eddington ratio range within which quasars seem to radiate.
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García-Vergara, Cristina, Matus Rybak, Jacqueline Hodge, Joseph F. Hennawi, Roberto Decarli, Jorge González-López, Fabrizio Arrigoni-Battaia, Manuel Aravena, and Emanuele P. Farina. "ALMA Reveals a Large Overdensity and Strong Clustering of Galaxies in Quasar Environments at z ∼ 4." Astrophysical Journal 927, no. 1 (March 1, 2022): 65. http://dx.doi.org/10.3847/1538-4357/ac469d.

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Abstract We present an Atacama Large Millimeter/submillimeter Array (ALMA) survey of CO(4–3) line emitting galaxies in 17 quasar fields at z ∼ 4 aimed at performing the first systematic search of dusty galaxies in high-z quasar environments. Our blind search of galaxies around the quasars results in five CO emitters with S/N ≥ 5.6 within a projected radius of R ≲ 1.5 h −1 cMpc and a velocity range of δv = ±1000 km s−1 around the quasar. In blank fields, we expect to detect only 0.28 CO emitters within the same volume, implying a total overdensity of 17.6 − 7.6 + 11.9 in our fields, and indicating that quasars trace massive structures in the early universe. We quantify this overdensity by measuring the small-scale clustering of CO emitters around quasars, resulting in a cross-correlation length of r 0 , QG = 8.37 − 2.04 + 2.42 h − 1 cMpc, assuming a fixed slope γ = 1.8. This contradicts the reported mild overdensities (x1.4) of Lyα emitters (LAEs) in the same fields at scales of R ≲ 7 h −1 cMpc, which are well described by a cross-correlation length 3.0 − 1.4 + 1.5 times lower than that measured for CO emitters. We discuss some possibilities to explain this discrepancy, including low star formation efficiency, and excess of dust in galaxies around quasars. Finally, we constrain, for the first time, the clustering of CO emitters at z ∼ 4, finding an autocorrelation length of r 0,CO = 3.14 ±1.71 h −1 cMpc (with γ = 1.8). Our work, together with the previous study of LAEs around quasars, traces simultaneously the clustering properties of both optical and dusty galaxy populations in quasars fields, stressing the importance of multiwavelength studies, and highlighting important questions about galaxy properties in high-z dense environments.
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Yee, H. K. C., and Richard F. Green. "The association of galaxy clusters with moderately-high-redshift quasars." Symposium - International Astronomical Union 119 (1986): 481–87. http://dx.doi.org/10.1017/s0074180900153239.

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CCD images of quasars having redshifts between 0.3 and 0.65 are analyzed to study the association of galaxies with quasars. Average luminosity functions (LF) of the excess galaxies associated with the radio-loud quasars are determined. It is found that for the sub-sample with z>0.55, there is a significant brightening of the characteristic magnitude M*, if qo is assumed to be 0. Comparing computed quasar-galaxy spatial-covariance amplitudes, we can conclude, at the 0.025 significance level, that the spatial-covariance amplitudes of the sub-sample with z>0.55 are greater than those of the lower redshift quasars. This indicates that there has been a strong evolution of preferred sites for bright radio-loud quasars, implying some number-density evolution of quasars has taken place, and that some rich clusters at z∼0.6, in comparison with the local rich clusters, have significantly different physical conditions.
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Ubachukwu, A. A., and J. N. Ogwo. "Luminosity Selection Effects and Linear Size Evolution in the Quasar/Galaxy Unification Scheme." Australian Journal of Physics 51, no. 1 (1998): 143. http://dx.doi.org/10.1071/p97012.

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The implications of linear size evolution and luminosity selection effects in the quasar/galaxy unification scheme have been investigated. We show that both radio galaxies and quasars undergo similar size evolution above some low redshift cut-off zc = 0·2–0·3. However, this evolution can be attributed largely to the strong luminosity selection effects present in the sample. We also observe that there is a marked difference in the luminosity–redshift slope between low and high redshift sources, which may be responsible for the conflicting results in the literature as to whether or not radio galaxies and quasars have similar linear size versus luminosity/redshift relationships. Our present result seems consistent with the quasar/galaxy unification scheme in which the two classes of object are expected to have similar linear size versus luminosity/redshift relationships.
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Shen, Xuejian, Philip F. Hopkins, Claude-André Faucher-Giguère, D. M. Alexander, Gordon T. Richards, Nicholas P. Ross, and R. C. Hickox. "The bolometric quasar luminosity function at z = 0–7." Monthly Notices of the Royal Astronomical Society 495, no. 3 (January 2020): 3252–75. http://dx.doi.org/10.1093/mnras/staa1381.

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ABSTRACT In this paper, we provide updated constraints on the bolometric quasar luminosity function (QLF) from z = 0 to z = 7. The constraints are based on an observational compilation that includes observations in the rest-frame IR, B band, UV, soft, and hard X-ray in past decades. Our method follows Hopkins et al. with an updated quasar SED model and bolometric and extinction corrections. The new best-fitting bolometric quasar luminosity function behaves qualitatively different from the old Hopkins model at high redshift. Compared with the old model, the number density normalization decreases towards higher redshift and the bright-end slope is steeper at z ≳ 2. Due to the paucity of measurements at the faint end, the faint end slope at z ≳ 5 is quite uncertain. We present two models, one featuring a progressively steeper faint-end slope at higher redshift and the other featuring a shallow faint-end slope at z ≳ 5. Further multiband observations of the faint-end QLF are needed to distinguish between these models. The evolutionary pattern of the bolometric QLF can be interpreted as an early phase likely dominated by the hierarchical assembly of structures and a late phase likely dominated by the quenching of galaxies. We explore the implications of this model on the ionizing photon production by quasars, the CXB spectrum, the SMBH mass density, and mass functions. The predicted hydrogen photoionization rate contributed by quasars is subdominant during the epoch of reionization and only becomes important at z ≲ 3. The predicted CXB spectrum, cosmic SMBH mass density, and SMBH mass function are generally consistent with existing observations.
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Meyer, Romain A., Roberto Decarli, Fabian Walter, Qiong Li, Ran Wang, Chiara Mazzucchelli, Eduardo Bañados, Emanuele P. Farina, and Bram Venemans. "Constraining Galaxy Overdensities around Three z ∼ 6.5 Quasars with ALMA and MUSE." Astrophysical Journal 927, no. 2 (March 1, 2022): 141. http://dx.doi.org/10.3847/1538-4357/ac4f67.

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Abstract We quantify galaxy overdensities around three high-redshift quasars with known [C ii]158 μm companions: PJ231–20 (z = 6.59), PJ308–21 (z = 6.24), and J0305–3150 (z = 6.61). Recent SCUBA2 imaging revealed the presence of 17 submillimeter galaxies (SMGs) with sky separations 0.′7 < θ < 2.′4 from these three quasars. We present ALMA Band 6 follow-up observations of these SCUBA2-selected SMGs to confirm their nature and redshift. We also search for continuum-undetected [C ii]158 μm emitters in the ALMA pointings and make use of archival MUSE observations to search for Lyα emitters (LAEs) associated with the quasars. While most of the SCUBA2-selected sources are detected with ALMA in the continuum, no [C ii]158 μm line emission could be detected, indicating that they are not at the quasar redshifts. Based on the serendipitous detection of CO 7–6 and [C i]809 μm emission lines, we find that four SMGs in the field of PJ231–20 are at z ∼ 2.4, which is coincident with the redshift of an Mg ii absorber in the quasar rest-frame UV spectrum. We report the discovery of two LAEs within <0.6 cMpc of PJ231–20 at the same redshift, indicating an LAE overdensity around this quasar. Taken together, these observations provide new constraints on the large-scale excess of Lyα- and [C ii]158 μm-emitting galaxies around z > 6 quasars and suggest that only wide-field observations, such as MUSE, ALMA, or JWST mosaics, can reveal a comprehensive picture of large-scale structure around quasars in the first billion years of the universe.
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Singal, J., S. Mutchnick, and V. Petrosian. "The X-Ray Luminosity Function Evolution of Quasars and the Correlation between the X-Ray and Ultraviolet Luminosities." Astrophysical Journal 932, no. 2 (June 1, 2022): 111. http://dx.doi.org/10.3847/1538-4357/ac6f06.

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Abstract We explore the evolution of the X-ray luminosity function of quasars and the intrinsic correlation between the X-ray and 2500 Å ultraviolet luminosities, utilizing techniques verified in previous works and a sample of over 4000 quasars detected with Chandra and XMM-Newton in the range 0 < z < 5. We find that quasars have undergone significantly less evolution with redshift in their total X-ray luminosity than in other wave bands. We then determine that the best-fit intrinsic power-law correlation between the X-ray and ultraviolet luminosities, of the form L X ′ ∝ ( L UV ′ ) γ , is γ = 0.28 ± 0.03, and we derive the luminosity function and density evolution in the X-ray band. We discuss the implications of these results for models of quasar systems.
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Jalan, Priyanka, Hum Chand, and Raghunathan Srianand. "Constraining the ratio of median pixel optical depth profile around z ∼ 4 quasars using the longitudinal proximity effect." Monthly Notices of the Royal Astronomical Society 505, no. 1 (May 10, 2021): 689–701. http://dx.doi.org/10.1093/mnras/stab1303.

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ABSTRACT We present a detailed study of the longitudinal proximity effect using a sample of 85 quasars spanning an emission redshift range of 3.5 ≤ zem ≤ 4.5 and Lyman continuum luminosity (L912) ranging from 1.06 × 1031 to 2.24 × 1032 erg s−1 Hz−1. We use the high-quality spectra of these quasars obtained at a spectral resolution of R ∼ 5100 and S/N ∼ 30 using X-SHOOTER spectrograph mounted on the Very Large Telescope (VLT). In our analysis, we compared the transmitted flux and pixel optical depth of the Ly α absorption originating from the vicinity of quasars to those from the general intergalactic medium (IGM) by using a redshift-matched control sample. The longitudinal proximity effect is found up to r ≤ 12 Mpc (proper) from quasars. By appropriately scaling up the pixel optical depth in the vicinity of quasars to account for the excess ionization by quasars, we constrain the ratio of median H i optical depth in the vicinity of the quasar to that of the IGM (Rτ(r)). The Rτ(r) is found to be significantly higher than unity up to 6 Mpc from the quasar with a typical radial profile of the form Rτ(r) = 1 + A × exp(− r/r0) with A = 9.16 ± 0.68 and r0 = 1.27 ± 0.08 Mpc. The integrated value of the scaled pixel optical depth over the radial bin of 0–6 Mpc is found to be higher by a factor of 2.55 ± 0.17 than the corresponding integrated value of the median pixel optical depth of the IGM. We also found Rτ(r) to be luminosity dependent.
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Gupta, N., G. Shukla, R. Srianand, J. K. Krogager, P. Noterdaeme, A. J. Baker, F. Combes, et al. "MALS SALT-NOT Survey of MIR-selected Powerful Radio-bright AGN at 0 < z < 3.5." Astrophysical Journal 929, no. 1 (April 1, 2022): 108. http://dx.doi.org/10.3847/1538-4357/ac4220.

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Abstract We present results of an optical spectroscopic survey using SALT and the Nordic Optical Telescope to build a Wide-field Infrared Survey Explorer mid-infrared color-based, dust-unbiased sample of powerful radio-bright (>200 mJy at 1.4 GHz) active galactic nuclei (AGN) for the MeerKAT Absorption Line Survey (MALS). Our sample has 250 AGN (median z = 1.8) showing emission lines, 26 with no emission lines, and 27 without optical counterparts. Overall, our sample is fainter (Δi = 0.6 mag) and redder (Δ(g−i) = 0.2 mag) than radio-selected quasars, and representative of fainter quasar population detected in optical surveys. About 20% of the sources are narrow-line AGN (NLAGN)–65% of these, at z < 0.5 are galaxies without strong nuclear emission, and 10% at z > 1.9, have emission line ratios similar to radio galaxies. The farthest NLAGN in our sample is M1513-2524 (z em = 3.132), and the largest radio source (size ∼330 kpc) is M0909-3133 (z em = 0.884). We discuss in detail 110 AGN at 1.9 < z < 3.5. Despite representing the radio loudest quasars (median R = 3685), their Eddington ratios are similar to the Sloan Digital Sky Survey quasars having lower R. We detect four C iv broad-absorption line (BAL) QSOs, all among AGN with least R, and highest black hole masses and Eddington ratios. The BAL detection rate ( 4 − 2 + 3 %) is consistent with that seen in extremely powerful (L 1.4GHz > 1025 W Hz−1) quasars. Using optical light curves, radio polarization, and γ-ray detections, we identify seven high-probability BL Lacertae objects. We also summarize the full MALS footprint to search for H i 21 cm and OH 18 cm lines at z < 2.
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Dissertations / Theses on the topic "Quasars. 0"

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Cogato, Fabrizio. "Vincoli all'Universo Oscuro tramite la combinazione ottimale di sonde cosmologiche tra 0." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24984/.

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In questa Tesi proponiamo uno studio analitico volto alla quantificazione di sinergie e complementarità tra sonde cosmologiche indipendenti in un contesto di inferenza dei parametri cosmologici. Tramite lo sviluppo di un codice computazionale versatile e robusto, sfruttiamo la statistica bayesiana per ricavare da una selezione di sonde cosmologiche a z<8 precisi vincoli su di un'ampia rosa di modelli cosmologici. In particolare, affianchiamo a due delle principali sonde, SuperNovae di Tipo Ia e Oscillazioni Barioniche Acustiche, alcune delle sonde più promettenti emerse di recente: Cronometri Cosmici, Quasar e Gamma-Ray Burst. Analizzandole sistematicamente al variare delle ipotesi cosmologiche esploriamo, oltre al modello standard ΛCDM, alcune delle sue più valide estensioni includendo una variazione nella geometria assunta e nella forma dell'equazione di stato dell'energia oscura. Abbiamo così la possibilità di identificare punti di forza e debolezza di ciascun metodo, e di valutare il contributo di ognuno al vincolo dei parametri cosmologici. Introduciamo perciò un primo metodo analitico per la quantificazione di sinergie e complementarità tra sonde cosmologiche indipendenti tramite la definizione di un parametro di ortogonalità che misuri l’angolo reciproco tra i vincoli delle varie sonde. Sfruttiamo quindi questo parametro per individuare la combinazione più efficace in funzione dei vincoli cosmologici che si desidera imporre. L'analisi congiunta di tutte le sonde produce interessanti risultati nell'ambito del paradigma cosmologico moderno. Indagando la forma dell'equazione di stato dell'energia oscura otteniamo w=-1.00±0.07 (1σ), mentre dallo studio della geometria ricaviamo Ωk=-0.07±0.11 (1σ). Per una cosmologia standard, troviamo un valore della costante di Hubble pari a 69.4±3.2 km/s/Mpc (1σ) non ancora competitivo nel contesto della Tensione di Hubble ma che, con l'inclusione di ulteriori sonde innovative, promette di raggiungere una maggiore precisione.
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Books on the topic "Quasars. 0"

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Swarup, Govind, and V. K. Kapahi, eds. Quasars. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4716-0.

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Shipman, Harry L. Black Holes, Quasars, and the Universe: Second Edition. Dover Publications, Incorporated, 2013.

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Book chapters on the topic "Quasars. 0"

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North, Gerald. "Quasars, Active Galaxies and Cosmology." In Astronomy in Depth, 210–21. London: Springer London, 2003. http://dx.doi.org/10.1007/978-0-85729-426-5_20.

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Barbieri, C., and S. Cristiani. "Quasar Candidates in the Field of S.A. 94 (2h53m+0°20′)." In Structure and Evolution of Active Galactic Nuclei, 465–70. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4562-3_28.

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"Quasars." In The Invisible Universe, 96–101. New York, NY: Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-68360-7_12.

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ELVIS, MARTIN, JONATHAN C. MCDOWELL, and BELINDA J. WILKES. "EUV EXCESSES IN QUASARS." In Extreme Ultraviolet Astronomy, 238–44. Elsevier, 1991. http://dx.doi.org/10.1016/b978-0-08-037302-7.50031-8.

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"Beyond the Quasars—Radio Cosmology." In The Invisible Universe, 112–21. New York, NY: Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-68360-7_14.

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Webb, James R. "Active galaxies, quasars and supermassive black holes." In Extragalactic Astrophysics (Second Edition). IOP Publishing, 2022. http://dx.doi.org/10.1088/978-0-7503-3551-5ch4.

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MARSHALL, HERMAN L. "EUV RADIATION FROM ACTIVE GALACTIC NUCLEI AND QUASARS." In Extreme Ultraviolet Astronomy, 228–37. Elsevier, 1991. http://dx.doi.org/10.1016/b978-0-08-037302-7.50030-6.

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Ifeoma Onah, Costecia, Augustine A. Ubachukwu, and Finbarr C. Odo. "Evolution of Radio Source Components and the Quasar/Galaxy Unification Scheme." In Astronomy [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.106244.

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In this work, a theoretical model is developed for explanation of temporal evolution of extragalactic radio sources via beaming, orientation effects and asymmetries. Equation of the form D≈P±q1+z−m is used to account for the D ∼ P/z relation. Also, D≈D01+z−1+z1+z2 accounted properly for Ω0=1 cosmology than the Ω0=0 counterpart in linear size versus redshift of radio sources. Similarly, D=Dc1∓lnPPc1/2 model explained redshift-luminosity relationship of extragalactic radio sources. The results from the regression analyses are q = +0.003 (r = 0.04) for sources with z < 1 and q = −1.59 (r = −0.6) for all z≥1 sources. A critical linear size, Dc of 316kpc which matches the maximum theoretical linear size, Dmax of 0.15D0 at a critical redshift zc∼1 and a critical luminosity Pc=26.33WHz−1 are obtained. The indication of all these results is that the linear size of radio sources evolves up to a certain limit in D–P plane and thereafter decreases with increasing luminosity as predicted in this work.
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Conference papers on the topic "Quasars. 0"

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Bondarenko, Yu, D. Marshalov, D. Vavilov, and Y. Medvedev. "International Radar Observations of Near-Earth Asteroids on Radio Telescopes of the Quasar VLBI Network." In Groud-Based Astronomy in Russia. 21st Century. Специальная астрофизическая обсерватория РАН, 2020. http://dx.doi.org/10.26119/978-5-6045062-0-2_2020_455.

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