Hubble quasar
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Hubble Quasar Studies: Insights and Discoveries
Hubble Constant Measurement Using Quasars
Time-Delay Strong Lensing and Quasars
The Hubble constant (H₀) has been a focal point of cosmological research, and quasars have played a significant role in its measurement. One method involves using time-delay strong lensing (TDSL) of quasars. For instance, the doubly imaged quasar SDSS 1206+4332 was analyzed using a combination of time delays, Hubble Space Telescope (HST) imaging, and other data to infer a Hubble constant of H₀ = 68.8 km s⁻¹ Mpc⁻¹1. This method, which avoids experimenter bias through blind analysis, has shown consistency with other independent measurements, providing a robust check on lens modeling systematics.
Quasars as Standard Candles
Another innovative approach uses quasars as "standard candles" by leveraging the non-linear relationship between their UV and X-ray emissions. This method has produced a Hubble Diagram extending up to redshifts of z ~ 5, offering new constraints on cosmological parameters when combined with supernova data2. This technique promises to refine our understanding of the universe's matter and energy content, especially with larger quasar samples in the future.
Combining Radio Structure and Gravitational Lensing
Combining observations of ultracompact radio structures in quasars with strong gravitational lensing has also been proposed to measure H₀ and cosmic curvature (Ωₖ). This method has yielded a Hubble constant of H₀ = 78.3 km s⁻¹ Mpc⁻¹ and provided insights into the spatial curvature of the universe3. Such combined approaches enhance the precision of cosmological measurements and help resolve existing tensions in H₀ values derived from different methods.
Gravitational Lensing and High-Redshift Quasars
Cluster-Lensed Quasars
Quasars lensed by galaxy clusters offer another avenue for H₀ measurement. Analyzing three such quasars (SDSS J1004+4112, SDSS J1029+2623, and SDSS J2222+2745) has provided a combined H₀ value of 74.1 km s⁻¹ Mpc⁻¹4. This method, though requiring a large sample size for high precision, demonstrates the potential of cluster-lensed quasars in cosmological studies.
Discovery of High-Redshift Lensed Quasars
The discovery of a gravitationally lensed quasar at z = 6.51, the first such object at the epoch of reionization, underscores the importance of high-resolution imaging in identifying lensed quasars. This quasar, magnified by a factor of ~50, suggests that many high-redshift lensed quasars might have been missed in previous surveys9. Such discoveries are crucial for understanding the early universe and the role of quasars in cosmic evolution.
Quasar Host Galaxies and Black Holes
Imaging Quasar Host Galaxies
HST imaging has been instrumental in studying quasar host galaxies. For example, a systematic search of the HST archive identified five low-redshift quasars, revealing interactions and companion objects indicative of recent galactic interactions5. These findings contribute to our understanding of the environments in which quasars reside and their evolutionary history.
Dual and Multiple Quasars
The identification of dual and multiple quasars, such as the quadruply lensed quasar SDSS J1608+2716, highlights the challenges and importance of high-resolution imaging in confirming such systems6. These discoveries provide insights into the dynamics of supermassive black holes and their role in galaxy mergers.
Conclusion
Quasars, through various innovative methods and high-resolution imaging, continue to be pivotal in advancing our understanding of the Hubble constant, cosmic structure, and the early universe. The integration of different observational techniques and the discovery of new quasar systems promise to refine our cosmological models and resolve existing tensions in fundamental measurements.
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Most relevant research papers on this topic
H0LiCOW – IX. Cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 and a new measurement of the Hubble constant
The Hubble constant H_0 = 68.8|$+5.4_-5.1$| km s1 Mpc1 is consistent with previous measurements, providing a sanity check on lens modeling systematics.
Highly CitedA Hubble Diagram for Quasars
Quasars can serve as "standard candles" for measuring cosmological parameters by using their intrinsic UV and X-ray emission as absolute distance indicators, providing robust constraints on matter and energy content in the cosmos.
Measurements of the Hubble constant and cosmic curvature with quasars: ultracompact radio structure and strong gravitational lensing
This study improves the method for measuring the Hubble constant and cosmic curvature by combining ultracompact radio structure and strong gravitational lensing, providing stringent constraints on H0 and K.
Hubble Constant Measurement from Three Large-separation Quasars Strongly Lensed by Galaxy Clusters
The Hubble constant H0 = 74.1 8.0 km s1 Mpc1 can be determined using six time delay measurements from three cluster-lensed quasars, with a 1% uncertainty achievable in the next decade.
Quasar host galaxy images from the Hubble Space Telescope Archive
Five low-redshift quasars identified in the HST Archive are involved in ongoing gravitational interactions, with three of them being at least 2.5 mag brighter than L.
Varstrometry for Off-nucleus and Dual Subkiloparsec AGN (VODKA). SDSS J1608+2716: A Subarcsecond Quadruply Lensed Quasar at z = 2.575
SDSS J1608+2716 is a quadruply lensed quasar at z = 2.575, with a fourth point-like component and edge-on disk galaxy in between the four point sources.
Quasars, their host galaxies and their central black holes
Radio-quiet quasars are more common than radio-loud quasars, with their host galaxies being predominantly massive ellipticals, indicating a strong relationship between black hole and spheroid mass.
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