Results 51 to 60 of about 1,473 (119)

Phantom‐based assessment of a modified 4D‐MRI protocol for abdominal tumor motion tracking: Effects of sequence parameters and modality comparison

Journal of Applied Clinical Medical Physics, Volume 27, Issue 1, January 2026.
Abstract Purpose To investigate the effects of targeted modifications to a clinical 4D‐MR pulse sequence on displacement accuracy for abdominal tumor motion tracking, and to compare its performance with established 4D‐MR and 4D‐CT protocols using a motion phantom driven by clinically representative respiratory waveforms.
Morgan Aire, David Solis, Reagan Dugan, Olivia Magneson, Krystal Kirby   +4 more
wiley   +1 more source

Machine Learning–based Search of High-redshift Quasars

The Astrophysical Journal Supplement Series
We present a machine learning search for high-redshift (5.0 < z < 6.5) quasars using the combined photometric data from the Dark Energy Spectroscopic Instrument (DESI) Imaging Legacy Surveys and the Wide-field Infrared Survey Explorer survey.
Guangping Ye, Huanian Zhang, Qingwen Wu
doaj   +1 more source

Quest for a Coherent Definition of Weak-line Quasars and Its Physical Implications

The Astrophysical Journal
Weak-line quasars (WLQs) represent a subset of type 1 quasars distinguished by remarkably weak high-ionization broad emission lines, yet exhibiting normal optical/UV continua. This study establishes a physically motivated definition of WLQs using 371,091
Xiaoqiang Cheng, Jianfeng Wu, Qiaoya Wu
doaj   +1 more source

Extreme Variability Quasars in Their Various States. II. Spectral Variation Revealed with Multiepoch Spectra

The Astrophysical Journal
We previously built a sample of 14,012 extremely variable quasars (EVQs) based on Sloan Digital Sky Survey (SDSS) and Pan-STARRS1 photometric observations.
Wenke Ren, Junxian Wang, Zhenyi Cai, Xufan Hu   +3 more
doaj   +1 more source

Prospects for Observing High-redshift Radio-loud Quasars in the SKA Era: Paving the Way for 21 cm Forest Observations

The Astrophysical Journal
The 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, Yichao Li, Yidong Xu, Hong Guo, Xin Zhang   +4 more
doaj   +1 more source

A Pilot Study for the CSST Slitless Spectroscopic Quasar Survey Based on Mock Data

The Astrophysical Journal
The wide survey of the Chinese Space Station Telescope (CSST) will observe a large field of 17,500 deg ^2 . The GU, GV, and GI grism observations of CSST will cover the wavelength range from 2550 to 10000 Å at a resolution of R  ∼ 200 and a depth of ...
Yuxuan Pang, Xue-Bing Wu, Yuming Fu, Rui Zhu, Bing Lyu, Huimei Wang, Xiaotong Feng   +6 more
doaj   +1 more source

Cosmic Himalayas: The Highest Quasar Density Peak Identified in a 10,000 deg2 Sky with Spatial Discrepancies between Galaxies, Quasars, and IGM H i

The Astrophysical Journal
We report the identification of a quasar overdensity in the BOSSJ0210 field, dubbed the Cosmic Himalayas, consisting of 11 quasars at z = 2.16−2.20, the densest overdensity of quasars (17 σ ) in the ∼10,000 deg ^2 of the Sloan Digital Sky Survey (SDSS ...
Yongming Liang, Masami Ouchi, Dongsheng Sun, Nobunari Kashikawa, Zheng Cai, Sebastiano Cantalupo, Kentaro Nagamine, Hidenobu Yajima, Takanobu Kirihara, Haibin Zhang, Mingyu Li, Rhythm Shimakawa, Xiaohui Fan, Kei Ito, Masayuki Tanaka, Yuichi Harikane, J. Xavier Prochaska, Andrea Travascio, Weichen Wang, Martin Elvis, Giuseppina Fabbiano, Junya Arita, Masafusa Onoue, John D. Silverman, Dong Dong Shi, Fangxia An, Takuma Izumi, Kazuhiro Shimasaku, Hisakazu Uchiyama, Chenghao Zhu   +29 more
doaj   +1 more source

Discovery of spectacular quasar-driven superbubbles in red quasars. [PDF]

Sci Adv, 2023
Shen L, Liu G, He Z, Zakamska NL, Glikman E, Greene JE, Hu W, Mou G, Wylezalek D, Rupke DSN.   +9 more
europepmc   +1 more source

The Detection Rate of Associated Mg ii Absorption Lines in Quasars Depends on Their Radio Emission

The Astrophysical Journal
In active galactic nuclei, jet-driven feedback plays a significant role in influencing the properties of gas within their host galaxy and the circumgalactic medium.
Zhi-Fu Chen, Luis C. Ho
doaj   +1 more source

Reliable Identification of Binary Supermassive Black Holes from Rubin Observatory Time-domain Monitoring

The Astrophysical Journal
Periodic signatures in time-domain observations of quasars have been used to search for binary supermassive black holes (SMBHs). These searches, across existing time-domain surveys, have produced several hundred candidates.
Megan C. Davis, Kaylee E. Grace, Jonathan R. Trump, Jessie C. Runnoe, Amelia Henkel, Laura Blecha, W. N. Brandt, J. Andrew Casey-Clyde, Maria Charisi, Caitlin A. Witt   +9 more
doaj   +1 more source