نتایج جستجو برای: quasar

تعداد نتایج: 5239  

1997
K. Nilsson H. J. Lehto

We have made a radio and optical study of the radio source PKS 0241+011 associated with a quasar at z = 1.40. In earlier radio maps this source appears as a large triple radio source with an angular extent of 400 arcsec (2.4h −1 Mpc; H 0 = 100h km s −1 Mpc −1 , q 0 = 0.0). If the triple radio structure seen in radio maps represents a single object, PKS 0241+011 would be the largest radio quasar...

2005
Luka Č. Popović

⋆⋆ Summary. Selective amplification of the line and continuum source by microlens-ing in a lensed quasar can lead to changes of continuum spectral slopes and line shapes in the spectra of the quasar components. Comparing the spectra of different components of the lensed quasar and the spectra of an image observed in different epochs one can infer the presence of millilensing, microlensing and i...

2008
YUE SHEN NETA A. BAHCALL

We select a sample of ∼ 4200 traditionally defined broad absorption line quasars (BALQs) from the Fifth Data Release quasar catalog of the Sloan Digital Sky Survey. For a statistically homogeneous quasar sample with 1.7 ≤ z ≤ 4.2, the BAL quasar fraction is ∼ 14% and is almost constant with redshift. We measure the auto-correlation of non-BAL quasars (nonBALQs) and the cross-correlation of BALQ...

2006
Matthew T. Whiting Rachel L. Webster Paul J. Francis

The high-redshift radio-loud quasar PKS 2126−158 is found to have a large number of red galaxies in close apparent proximity. We use the Gemini Multi-Object Spectrograph (GMOS) on Gemini South to obtain optical spectra for a large fraction of these sources. We show that there is a group of galaxies at z ∼ 0.66, coincident with a metal-line absorption system seen in the quasar’s optical spectrum...

2009
R. Decarli M. Dotti R. Falomo M. Uslenghi

We present an imaging study of the black hole binary candidate SDSS J1536+0441 (z ≈ 0.3893), based on deep, high resolution VzK images collected at the ESO/VLT. The images clearly show an asymmetric elongation, indicating the presence of a companion source at ∼ 1 (≈ 5 kpc projected distance) East from the quasar. The host galaxy of the quasar is marginally resolved. We find that the companion s...

2013
Matthew J. Graham S. G. Djorgovski Andrew J. Drake Ashish A. Mahabal Melissa Chang Daniel Stern Ciro Donalek Eilat Glikman

We compare quasar selection techniques based on their optical variability using data from the Catalina Real-time Transient Survey (CRTS). We introduce a new technique based on Slepian wavelet variance (SWV) that shows comparable or better performance to structure functions and damped random walk models but with fewer assumptions. Combining these methods with WISE mid-IR colors produces a highly...

2017
H. Lin R. G. McMahon C. D. Fassnacht T. F. Eifler

We report the discovery and spectroscopic confirmation of the quad-like lensed quasar system DES J0408-5354 found in the Dark Energy Survey (DES) Year 1 (Y1) data. This system was discovered during a search for DES Y1 strong lensing systems using a method that identified candidates as red galaxies with multiple blue neighbors. DES J0408-5354 consists of a central red galaxy surrounded by three ...

2001
Gordon T. Richards Robert H. Becker

We present high resolution radio data at 3.5 and 20 cm from the VLA in the A configuration for 144 quasars with known C IV absorption line properties. Using these measurements, we compare and contrast a number of quasar orientation indicators. These quantities are used to study the velocity distribution of C IV absorption lines as a function of quasar orientation measures. That there is an exce...

2002
Makoto Kishimoto Omer Blaes

We have found for the first time a Balmer edge feature in the Big Blue Bump emission of a quasar. The feature is seen in the polarized flux spectrum of the quasar, where all the emissions from outside the nucleus are scraped off and removed. The existence of the Balmer-edge absorption feature directly indicates that the Big Blue Bump is indeed thermal and optically-thick.

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