![]() 2001) show that they are created by mass-accreting black holes with a certain geometry of the magnetic field that threads the accretion disc. Astrophysical models ( Blandford & Znajek 1977 hereafter B − Z, Blandford & Payne 1982 Meier et al. The creation of the relativistic radio jets is not completely understood and is currently under investigation. Thereafter, it was realised by theoretical efforts ( Salpeter 1964 Lynden-Bell 1969 Bardeen 1970) that a supermassive black hole (10 6−10 10 M ⊙) residing at the centre of host galaxy must be responsible for powering ( Rees 1971) the radio galaxy through twin collimated and relativistic jets ( Blandford & Rees 1974 Scheuer 1974). ![]() These galaxies later came to be known as radio galaxies (RGs), whose radio emission often extends well beyond the physical extent of the galaxies as seen at optical wavelengths. In the 1950s, it was revealed that some galaxies dominantly emit at radio wavelengths ( Jennison & Das Gupta 1953 Baade & Minkowski 1954) through synchrotron radiation ( Shklovskii 1955 Burbidge 1956). Tables A1–A4 are only available at the CDS via anonymous ftp to ( 130.79.128.5) or via We discuss their formation and growth scenarios, highlighting the key physical factors that cause them to reach their gigantic size. We present new results for GRGs that range from black hole mass to large-scale environment properties. The probability of finding the brightest cluster galaxy as a GRG is quite low and even lower for high-mass clusters. Our environmental study reveals that ∼10% of all GRGs may reside at the centres of galaxy clusters, in a denser galactic environment, while the majority appears to reside in a sparse environment. Our analysis reveals a strong correlation between the black hole Eddington ratio and the scaled jet kinetic power, which suggests a disc-jet coupling. We find that GRGs in high-excitation state statistically have larger sizes, stronger radio power, jet kinetic power, and higher Eddington ratio than those in low-excitation state. This enabled us to compare key physical properties of their active galactic nuclei, such as the black hole mass, spin, Eddington ratio, jet kinetic power, total radio power, magnetic field, and size. Using the mid-infrared data, we classified GRGs in terms of their accretion mode: either a high-power radiatively efficient high-excitation state, or a radiatively inefficient low-excitation state. However, GRGs have a lower Eddington ratio than RGs. Our results establish that the distributions of the radio spectral index and the black hole mass of GRGs do not differ from the corresponding distributions of normal-sized radio galaxies (RGs). This provides new insights into their nature. For the first time, we present the multi-wavelength properties of the largest sample of GRGs. As part of the project SAGAN, we have created a database of all known GRGs, the GRG catalogue, from the literature (including our new sample) it includes 820 sources. We have identified 162 new GRGs primarily from the NRAO VLA Sky Survey with sizes ranging from ∼0.71 Mpc to ∼2.82 Mpc in the redshift range of ∼0.03−0.95, of which 23 are hosted by quasars (giant radio quasars). We present the first results of a project called SAGAN, which is dedicated solely to the studies of relatively rare megaparsec-scale radio galaxies in the Universe, called giant radio galaxies (GRGs). Lyon, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon, 69230 Saint-Genis-Laval, France ![]() Max-Planck-Institut für Radioastronomie, Auf dem Hugel 69, 53121 Bonn, Germanyĭepartment of Physics, Presidency University, 86/1 College Street, Kolkata 700073, Indiaĭiscipline of Astronomy, Astrophysics and Space Engineering, Indian Institute of Technology Indore, Indore 453552, India Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR Chinaĭepartment of Astronomy, School of Physics, Peking University, Beijing 100871, PR China ![]() National Centre for Radio Astrophysics, TIFR, Post Bag 3, Ganeshkhind, Pune 411007, India Homi Bhabha Road, Pashan, Pune 411008, India Indian Institute of Science Education and Research (IISER), Dr. Sorbonne Université, Observatoire de Paris, Université PSL, CNRS, LERMA, 75014 Paris, FranceĬollège de France, 11 Place Marcelin Berthelot, 75231 Paris, France Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The NetherlandsĮ-mail: Centre for Astronomy and Astrophysics (IUCAA), Pune 411007, India Astronomical objects: linking to databases.Including author names using non-Roman alphabets.Suggested resources for more tips on language editing in the sciences Punctuation and style concerns regarding equations, figures, tables, and footnotes
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