Results 31 to 40 of about 183 (149)
Gravitational Lensing as a Probe of Cold Dark Matter Subhalos
Advances in Astronomy, Volume 2010, Issue 1, 2010., 2010 In the cold dark matter scenario, dark matter halos are assembled hierarchically from smaller subunits. Some of these subunits are disrupted during the merging process, whereas others survive temporarily in the form of subhalos. A long‐standing problem with this picture is that the number of subhalos predicted by simulations exceeds the number of ...
Erik Zackrisson +2 more
wiley +1 more source
Radio Loud and Radio Quiet Quasars
, 2016 We discuss 6 GHz JVLA observations covering a volume-limited sample of 178 low redshift ($0.2 < z < 0.3$) optically selected QSOs. Our 176 radio detections fall into two clear categories: (1) About $20$\% are radio-loud QSOs (RLQs) having spectral luminosities $L_6 \gtrsim 10^{\,23.2} \mathrm{~W~Hz}^{-1}$ primarily generated in the active ...
Kellermann, K. I. +4 more
openaire +2 more sources
Unveiling Radio Loudness in Quasars
, 2003 We present a new approach to tackle the issue of radio loudness in quasars. We constrain a (simple) prescription for the intrinsic distribution of radio-to-optical ratios by comparing properties of Monte Carlo simulated samples with those of observed optically selected quasars.
Cirasuolo, M. +3 more
openaire +2 more sources
The Case for Two Quasar Populations
Open Astronomy, 2011 We present evidence for two populations of quasars showing distinctly different broad line structure and kinematics. The first evidence for quasar dichotomy involve differences between radio-quiet and radio-loud sources.
Sulentic Jack +2 more
doaj +1 more source
Phylogenetic Analyses of Quasars and Galaxies
Frontiers in Astronomy and Space Sciences, 2017 Phylogenetic approaches have proven to be useful in astrophysics. We have recently published a Maximum Parsimony (or cladistics) analysis on two samples of 215 and 85 low-z quasars (z < 0.7) which offer a satisfactory coverage of the Eigenvector 1 ...
Didier Fraix-Burnet +2 more
doaj +1 more source
The Astrophysical Journal, 2023 We constrain the emission mechanisms responsible for the prodigious electromagnetic output generated by active galactic nuclei (AGNs) and their host galaxies with a novel state-of-the-art AGN radio-to-X-ray spectral energy distribution model fitting code
Mojegan Azadi +14 more
doaj +1 more source
Hidden Blazars In Radio Loud Quasars? [PDF]
Symposium - International Astronomical Union, 2000 We present the initial results from our search for hidden blazars via CIV emission line variability among radio loud quasars. The implications on models of quasar Broad Emission Line Regions are discussed, and we focus on the tidally disrupted star model.
openaire +1 more source
Blueshifted Fe ii and Balmer Broad Emission lines in a Reddened Quasar
The Astrophysical Journal, 2023 We present detailed analysis of the optical and near-infrared spectrum of the reddened radio-loud quasar F2M J154043.74+492323.9 with strong optical Fe ii emission of ${R}_{4570}\equiv \tfrac{\mathrm{Fe}\,{\rm\small{II}}\lambda \lambda \,4434,4684}{{\rm ...
Yipeng Zhou +3 more
doaj +1 more source
The ultraviolet spectra of radio-loud and radio-quiet quasars [PDF]
The Astronomical Journal, 1993 The rest-frame ultraviolet spectral properties of matched samples of radio-loud, radio-moderate, and radio-quiet quasars are investigated, using quasars drawn from the Large Bright QSO Survey. We confirm the absence of spectral differences between radio-loud and radio-quiet quasars at rest-frame wavelengths longward of 1600 A, as reported by previous ...
Francis, Paul +2 more
openaire +2 more sources
The Astrophysical JournalThe 21 cm forest is a sensitive probe for the early heating process and small-scale structures during the epoch of reionization (EOR), to be realized with the upcoming Square Kilometre Array (SKA). Its detection relies on the availability of radio-bright
Qi Niu +4 more
doaj +1 more source