Results 81 to 90 of about 83,297 (253)

Quasars Probing Quasars. II. The Anisotropic Clustering of Optically Thick Absorbers around Quasars [PDF]

open access: yesThe Astrophysical Journal, 2007
With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We used a sample of 17 Lyman limit systems with column density N_HI > 10^19 cm^-2 selected from 149 projected quasar pair sightlines, to investigate the clustering pattern of optically thick ...
Hennawi, Joseph F., Prochaska, Jason X.
openaire   +2 more sources

Probing ~100 AU Intergalactic MgII Absorbing "Cloudlets" with Quasar Microlensing

open access: yes, 2006
Intergalactic MgII absorbers are known to have structures down to scales ~ 10^{2.5} pc, and there are now indications that they may be fragmented on scales
Kayser R., Subo Dong
core   +3 more sources

Spatially Resolved Patchy Lyman-$\alpha$ Emission Within the Central Kiloparsec of a Strongly Lensed Quasar Host Galaxy at z = 2.8 [PDF]

open access: yes, 2017
We report the detection of extended Lyman-$\alpha$ emission from the host galaxy of SDSS~J2222+2745, a strongly lensed quasar at $z = 2.8$. Spectroscopic follow-up clearly reveals extended Lyman-$\alpha$ in emission between two images of the central ...
Acharyya, Ayan   +12 more
core   +2 more sources

EIGER. III. JWST/NIRCam Observations of the Ultraluminous High-redshift Quasar J0100+2802

open access: yesThe Astrophysical Journal, 2023
We present the first rest-frame optical spectrum of a high-redshift quasar observed with JWST/NIRCam in Wide Field Slitless mode. The observed quasar, J0100+2802, is the most luminous quasar known at z > 6. We measure the mass of the central supermassive
Anna-Christina Eilers   +8 more
doaj   +1 more source

Margin reduction and optimal prescription isodose model for liver stereotactic radiotherapy with respiratory motion

open access: yesJournal of Applied Clinical Medical Physics, Volume 27, Issue 1, January 2026.
Abstract Purpose This study aimed to establish a framework for optimizing planning target volume (PTV) margins in liver SBRT using virtual 4DCT (v4DCT), by introducing the concept of the Dosimetric Coverage Amplitude (DCA) to quantify motion tolerance and deriving an Optimal Margin (OM) that balances tumor coverage with normal‐tissue sparing.
Daisuke Kawahara   +5 more
wiley   +1 more source

A Southern Photometric Quasar Catalog from the Dark Energy Survey Data Release 2

open access: yesThe Astrophysical Journal Supplement Series, 2022
We present a catalog of 1.4 million photometrically selected quasar candidates in the southern hemisphere over the ∼5000 deg ^2 Dark Energy Survey (DES) wide survey area. We combine optical photometry from the DES second data release (DR2) with available
Qian Yang, Yue Shen
doaj   +1 more source

Logarithmic and Strong Coupling Models in Weyl‐Type f(Q,T)$f(Q,T)$ Gravity

open access: yesAnnalen der Physik, Volume 538, Issue 1, January 2026.
This work explores Weyl‐type f(Q,T) gravity using recent observational datasets — CC, Pantheon+, Union 3.0, and DESI DR2. Through MCMC analysis of logarithmic and strong coupling models, the study reveals a transition from deceleration to acceleration, quintessence‐to‐phantom dynamics, and late‐time consistency with LCDM, offering a geometry‐driven ...
Rahul Bhagat, S. K. Tripathy, B. Mishra
wiley   +1 more source

Lensed quasar hosts

open access: yesNew Astronomy Reviews, 2006
8 pages, 6 figures, review article with C. Impey at the conference on "QSO Host Galaxies: Evolution and Environment", Aug. 29-Sep.
Peng, Chien Y.   +7 more
openaire   +2 more sources

Quasar Clustering and the Lifetime of Quasars [PDF]

open access: yesThe Astrophysical Journal, 2001
ApJ Accepted (Feb 2001). 30 pages, 8 embedded ps figures, AASTEX5. Added discussion of quasar luminosity evolution. Also available at http://www.ociw.edu/~martini/pubs/
Martini, Paul, Weinberg, David H.
openaire   +3 more sources

Measuring the Virial Temperature of Galactic Halos Through Electron Scattering of Quasar Emission Lines

open access: yes, 1998
Semi-analytic models of galaxy formation postulate the existence of virialized gaseous halos around galaxies at high redshifts. A small fraction of the light emitted by any high-redshift quasar is therefore expected to scatter off the free electrons in ...
Abraham Loeb   +10 more
core   +2 more sources

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